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UNITED STATES ARMY AVIATION CENTER OF EXCELLENCE
FORT RUCKER, ALABAMA
JUNE 2011
STUDENT HANDOUT
TITLE: AH-64 INTEGRATED HELMET AND DISPLAY SIGHT SYSTEM (IHADSS)
(Lot 13)
FILE NUMBER: 11-0920-4.0
This package has been developed for use by: AH-64D Aviator Qualification Course
Proponent for this Student Handout is: COMMANDER, 110
th AVIATION BRIGADE
ATTN: ATZQ-ATB-AD
Fort Rucker, AL 36362
FOREIGN DISCLOSURE STATEMENT: FD6. This product/publication has been reviewed by the product developers in coordination with the USAAWC Foreign Disclosure Authority. This product is releasable to students from foreign countries who have purchased the AH-64D model, but the IETM is NOT releasable.
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TERMINAL LEARNING OBJECTIVE
At the completion of this lesson, you will:
ACTION: Demonstrate knowledge of components, care requirements, characteristics and symbology and messages interpretation for the Integrated Helmet And Display Sight System (IHADSS).
CONDITIONS: In a classroom environment, given an AH-64D Operator’s Manual (TM 1-1520-251-10-2), AH-64D Operator’s and Crewmember’s Checklist (TM 1-1520-251-CL-2), and the Aircrew Training Manual (TC 1-251), and the Student Handout.
STANDARDS: Identify the components and characteristics of the AH-64D Integrated Helmet and Display Sight System (IHADSS) to include interpretation of symbology and messages and receive a ―Go‖ by correctly answering 14 of 20 questions on scoreable unit 1 of criterion-referenced test 011-1047 in accordance with the Student Evaluation Plan.
Introduction
The IHADSS is organized into two subsystems: the Helmet Mounted Sight (HMS) subsystem and the
Helmet Mounted Display (HMD) subsystem. The HMS subsystem provides continuous LOS
information to the Weapon Processor (WP) for sensor pointing and weapons aiming. The HMD
subsystem provides the electro-optical link (display) between the selected sensor (PNVS or TADS)
and the crewmember, which allows the crewmember to see the world outside the cockpit through the
FLIR sensor. These two subsystems form a closed loop, which electrically and electro-optically links
the crewmember with the selected sensor. The IHADSS uses a monocular display for pilotage, which
increases the need for proficiency and understanding of operation to reduce pilot workload and
ensure safe and effective mission completion.
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A. ENABLING LEARNING OBJECTIVE 1:
After this lesson, you will:
ACTION: Identify the components of the IHADSS.
CONDITIONS: Given a written test without the use of student notes or references.
STANDARDS: In accordance with TM 1-1520-251-10-2 and TC 1-251.
1. Learning Step/Activity 1. Identify the components of the IHADSS.
Figure 1 IHADSS IHU and HDU
a. IHADSS
(1) IHADSS combines the Integrated Helmet Unit (IHU) and the Helmet Display Unit
(HDU), which is also referred to as the Helmet Mounted Display (HMD).
(2) The combination of IHU and HDU provides head protection, sensor pointing,
weapons ballistic calculations, and communications.
(3) The helmet component of the IHADSS provides an audio headset for
communication. The audio portion of the helmet is not considered a part of the
IHADSS.
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(4) The IHADSS is used as the crewmember’s (head-mounted) primary day/night
Heads-Up Display (HUD) control for the weapon systems, navigating, and flying
the aircraft.
(5) The HDU provides the crewmembers with night vision imagery for night flight.
Figure 2 IHADSS Subsystem Components
b. IHADSS subsystems
(1) IHADSS is task-organized into two subsystems.
(a) HMS subsystem. The HMS subsystem provides continuous Line Of
Sight (LOS) information to the Weapons Processors (WPs) for sensor
pointing and weapons aiming.
(b) HMD subsystem. The HMD subsystem provides the electro-optical link
(display) between the selected sensor—Pilot Night Vision Sensor
(PNVS) or Target Acquisition and Designation Sight (TADS)—and the
crewmember. The HMD allows the crewmember to see the world
outside the cockpit through the Forward Looking Infrared (FLIR) sensor.
(2) These two subsystems form a closed loop that electrically and electro-optically
links the crewmember with the selected sensor (PNVS or TADS).
(3) Together these subsystems provide the crew with a very precise means of
moving the Night Vision System (NVS) sensors and sights while providing an
aiming point to the WP for accurate ballistic calculations.
c. IHADSS components
(1) The IHADSS components are located primarily in the crewstations and the forward
portions of the Extended Forward Avionics Bay (EFABs).
(2) Many of IHADSS components do not require any crewmember interaction but are an
integral part of the system.
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(3) The components of the IHADSS will be discussed within their functional groups:
(a) HMS subsystem components
(b) HMD subsystem components
(4) The other components that are integral to the IHADSS but will not be discussed in this
Learning Objective are:
(a) WPs. The WPs are the bus controllers for the weapons and sight subsystems.
(b) Display Processors (DP). The DPs provide symbol generation for the
appropriate symbology within the crewmembers’ HDU.
(c) TADS and PNVS components. The TADS and PNVS components provide the
selected sensor imagery to be displayed to the crewmembers’ HDU.
d. HMS subsystem
(1) HMS components
(a) IHU
(b) Sensor Surveying Unit (SSU)
(c) Sight Electronic Unit (SEU)
(d) Boresight Reticle Unit (BRU)
(2) HMS component description
Figure 3 IHU
(a) IHU
1) The IHU is a fitted helmet with an attached visor and housing
assembly that provides for crash protection, noise attenuation,
and mounting for the following:
a) Four Infrared (IR) detectors and associated electronics
attached to the insides of the helmet shell
b) HDU
c) Communications components
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2) The helmet is currently issued in three sizes (medium, large, and
extra large) and is fitted to each individual.
3) The helmet weighs approximately 3.1 pounds, approximately 4
pounds with the HDU mounted.
4) The IHU provides the circuitry and IR detectors necessary to
detect the SSU IR fan beams. The detector circuitry is internal to
the helmet and is mounted between the helmet shell and the
helmet liner.
5) There are two IR detectors located on each side of the helmet,
one towards the front of the helmet and one towards the rear of
the helmet.
6) The IR detectors and IHU electronics detect and generate the
necessary electrical pulses, which are then sent to the SEU.
7) There are two connecting cables on the IHU, one that connects
the IR detectors to the aircraft, and the other for crewmember
communications.
Figure 4 SSUs
(b) SSU
1) Two SSUs are located in each crewstation and are attached to
the airframe on each side of the crewmember seat.
2) Each SSU is surveyed into position and rigidly mounted to the
airframe when the aircraft is assembled. The SSU itself can be
removed and replaced from the SSU mount without having to
resurvey it in the event of an SSU failure.
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3) Each SSU generates thin fan shaped beams of IR energy
designed to stimulate the IR detectors on the crewmember’s
helmet, causing them to send electronic pulses to the SEU.
4) Each SSU is electronically interfaced to the SEU and is
dependent on the SEU for power and operation.
5) The placement of the SSUs was designed to provide the
maximum cockpit coverage regardless of crewmember head
position.
6) Placement and orientation of the SSUs define the area within the
cockpit where the HMS subsystem can measure the IHU
position, establishing the motion box.
Figure 5 Motion Box
7) The motion box is a theoretical rectangular box that represents
the physical limits at which the SSUs can stimulate a pair of IR
detectors.
8) Motion box dimensions
a) Forward: 12 inches
b) Aft: 1.5 inches
c) Horizontal: 5 inches
d) Vertical: ±2.5 inches
9) Dimensions are determined by engineering data, based on a
typical user's head pivot point and design eye position.
10) If a crewmember’s helmet is outside the motion box, the SSUs
can no longer stimulate the IR detectors, so head position
indications are lost. This results in an ―IHADSS LOS INVALID‖
message being displayed on the crewmember’s High Action
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Display (HAD). Placing the IHU within the motion box will delete
the IHADSS INVALID message and return the system to normal
operation.
11) The motion box can also be altered if the SSUs or the IR
detectors on the IHU are obstructed or damaged. It is important
for crewmembers to ensure that the SSUs and IR detectors are
functional and unobstructed during flight.
12) Redundancy within the systems allows for limited component
failure without serious degradation to system operation. This
includes the following:
a) One SSU not operational
b) One IR detector (of the four) not operational
c) One IR detector on each side of the IHU not operational
13) With component loss, aiming accuracy of the sight/sensors and
weapons may be reduced or at times intermittent based on
crewmember head movement within the motion box.
Figure 6 SEU
(c) SEU
1) The SEU is a processor that interfaces directly with the IHU (IR
detectors) and SSUs to compute each crewmember LOS and
sends that information to the WP.
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2) The SEU is the processor that computes the LOS of the
crewmember by determining the crewmember’s head position in
azimuth and elevation relative to the Armament Datum Line
(ADL).
3) The SEU is located in the right EFAB.
4) The SEU supplies power to the SSUs and monitors the SSU
functions.
Figure 7 BRU
(d) BRU
1) The BRU is an electro-optical device aligned to the aircraft ADL
that provides the crewmember with a collimated (bull's eye)
reticle pattern.
2) The BRU is surveyed into position and rigidly mounted on top of
the center section of the crewmember's instrument panel.
3) It is used to boresight the IHU in combination with the HDU to
the ADL for that crewstation. The HMD portion of the IHADSS is
then coupled together with the HMS portion of IHADSS at the
completion of a boresight routine.
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Figure 8 BRU Reticle Pattern
4) Brightness of the BRU reticle is controlled by the PRIMARY
rheostat control located on the INTR light panel.
5) The reticle pattern consists of two concentric circles, which
provide the crewmember with a 5° acquisition cone measuring
1.5 inches across when viewed from 20 inches from the BRU
and 3 inches across when viewed from 40 inches.
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Figure 9 HMS Operations
(3) HMS operations
(a) The HMS provides for accurate measurement of the IHU LOS. It is
designed to continuously measure the IHU LOS, as long as the IHU is
within the motion box.
(b) LOS is calculated from known data, through the SEU.
1) Fixed data
a) The angular velocity of the rotating mirror, rotational
direction, and the distance between the SSU mirrors
b) Distance between the IR detectors
c) SSU that is in position to stimulate a particular pair of IR
detectors
2) Computed data. SEU computes the time differential between
timing pulse received from the appropriate SSU and the
electrical pulse generated by the stimulated IR detector.
3) The SEU determines the location of both detectors of either
detector pair, which defines two points in space. A line
connecting these two points represents the LOS of the detector
pair and by definition, the LOS of the IHU (electronic LOS).
e. HMD subsystem. The HMD subsystem displays the FLIR image (PNVS or TADS as
selected) and symbology to the crewmember.
(1) HMD components
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(a) Display Electronics Unit (DEU)
(b) Display Adjust Panels (DAPs)
(c) HDU
(2) HMD component description
Figure 10 DEU
(a) DEU
1) The DEU provides the interface between the selected sensor
(PNVS or TADS) and the HMD subsystem (video processor).
2) It is located in the right EFAB.
3) It provides the following functions:
a) Receives composite video signals from the DP for the
pilot and CPG sensor video
b) Responds to video selection by the crewmember and
provides the selected video to the crewmember's DAP
c) Provides video signal vertical and horizontal sizing and
centering
d) Provides power to the DAP
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e) Generates, upon command from the crewstation, a test
pattern (grayscale) to the crewmember for IHADSS video
adjustments (brightness and contrast)
Figure 11 DAP
(b) DAP
1) The DAP receives video signals from the DEU and is the
interface between the DEU and the HDU. The DAP contains two
connectors on the face where the crewmember’s HDU is
attached.
2) Each DAP has independent control of the HDU in that
crewstation, allowing the crewmembers to adjust their own HDU.
However, the location of the DAPs makes it difficult for
crewmembers to make adjustments for proper sizing and
centering while seated in the aircraft. Maintenance personnel
should be available for this adjustment.
3) The DAP are located on the right side, behind the seat, in each
crewstation.
4) The DAP control the brightness and contrast of the HDU in
response to the crewstation brightness and contrast controls.
They contain a high voltage power supply and video amplifier
required to drive the HDU Cathode Ray Tube (CRT).
5) The DAP provide mounting for the sizing and centering controls
for the DEU. The top two rheostats are used to adjust the
horizontal sizing and centering while the middle two rheostats
allow the crewmember to adjust vertical sizing and centering.
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6) The DAP electronically focus the video signal from the DEU
using the FOCUS adjustment rheostat (bottom).
7) Once a DAP has been adjusted for one crewmember, it does not
require additional adjustments for a different crewmember.
Figure 12 HDU
(c) HDU
1) The HDU is an electro-optical (monocular) display device which
provides the video and symbology input from the DAP to be
displayed on the combiner lens in front of the crewmember's
right eye.
2) The HDU contains a 0.75 inch CRT and magnifying optics which
are designed to display an image so the crew receives a 30° by
40° Field Of View (FOV).
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Figure 13 HDU
3) A combiner lens is mounted on an adjustable stem to provide
custom adjustment for each crewmember. Video image is
projected onto the combiner lens permitting simultaneous
viewing of video and the outside world.
4) The HDU incorporates a quick release mount to the IHU.
5) The HDU receives operational power from the DAP.
6) Adjustments (in/out) are made on the HDU barrel assembly.
7) A focus adjustment ring (infinity focus collar) is located on the
rear of the HDU barrel for focusing the image presented on the
combiner lens.
8) A display orientation adjustment (image rotation collar) is located
forward of the focus adjustment ring and is used to level the
display as seen on the combiner lens.
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CHECK ON LEARNING
1. The IHADSS consists of what two subsystems?
ANSWER: ________________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. What sighting subsystem component does the IHU interface with for LOS calculation?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
3. What components make up the HMD subsystem?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
4. Which component creates the symbology viewed by the crewmember?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
5. What components make up the HMS subsystem?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
6. What two adjustments are made on the HDU assembly?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
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B. ENABLING LEARNING OBJECTIVE 2
ACTION: Identify care requirements for IHADSS components and the
characteristics of connecting the IHADSS and mounting the HDU to
the IHU.
CONDITIONS: Given a written test without the use of student notes or references.
STANDARDS: In accordance with TM 1-1520-251-10-2, TM 1-1520-251-CL-2,
and TC 1-251.
1. Learning Step/Activity 1. Identify care requirements for IHADSS components and the
characteristics of connecting the IHADSS and mounting the HDU to the IHU.
Figure 14 IHU Handling
a. Care of IHADSS components
(1) IHU
(a) Do not carry or hang the IHU by the chinstrap. This may cause the liner
to shift, inducing LOS misalignment.
(b) Avoid leaving the IHU in direct sunlight as this may damage the IR
detectors.
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(c) Avoid dropping the IHU as this may either damage or shift the IR
detectors, causing LOS misalignment.
Figure 15 HDU Storage
(2) HDU
(a) Each crewstation has an HDU storage compartment. Caution must be
utilized when entering or exiting the crewstation to avoid stepping on or
kicking the HDU or HDU storage panel.
(b) Exercise care when removing or inserting the HDU into the HDU storage
panel to avoid damage.
(c) When handling the HDU, avoid scratching or leaving fingerprints on the
coated combiner lens.
(d) Extra care should be taken when handling the combiner lens to avoid
loosening or breaking the sliding clip attached to the HDU.
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Figure 16 SSU and BRU
(3) SSU and BRU
(a) The SSUs and BRUs are surveyed into place when the aircraft is
manufactured because of their importance in establishing the
crewmember’s LOS relative to the ADL.
(b) Crewmembers must use care when entering or exiting the aircraft not to
use these components as handholds as this may cause misalignments of
the mounting brackets or the components themselves.
(c) The IHU and other objects should not be hung from or placed over the
SSUs as this could cause displacement of the bracket or component.
(d) The SSUs become hot after use and could cause severe burns if
crewmembers come in contact with them.
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Figure 17 IHU Connectors
b. Attaching the IHU to the aircraft
(1) The IHU must be connected to the aircraft using the two attached cords.
(a) The smaller cord establishes the communications link.
(b) The larger cord establishes the link between the crewmember and the
aircraft for the Sighting System. This cord connects the crewmember’s
IHU directly to the SEU.
(2) If the IHU is not properly connected during aircraft power-up, a question mark is
displayed in the HAD sight select data field (unless the crewmember sight selects
Fire Control Radar [FCR] or TADS), indicating that the HMD is not connected
and cannot be used as a sight.
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Figure 18 HDU Connectors
c. Attaching the HDU to the IHU
(1) Remove the HDU from the HDU storage panel and ensure that the cable
assembly is properly connected to the DAP. There are two cannon plug
connectors that attach the HDU to the DAP.
(2) Once the IHU is connected to the aircraft and the crewmember has fitted the IHU
comfortably on the head, the HDU must be mounted to the IHU.
(3) The HDU mounting plate (clip) must be brought into the IHU at a right angle with
the mounting plate resting on the receiver assembly. The crewmembers must
rotate the HDU down until they ―feel‖ it lock into place.
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Figure 19 Secure Cable
d. Securing the HDU cable assembly
(1) An alligator clip is attached to the HDU cable and is designed to secure the HDU
cable to the crewmember restraint harness when the HDU is worn.
(2) The crewmember should rotate the head left and right to ensure that enough
―slack‖ was left in the HDU cable after securing it to the restraint harness.
(3) The alligator clip should not be attached to the survival vest. Removing the
alligator clip from the vest during an egress sequence could slow or hinder the
egress.
(4) The IHADSS HDU cable should not be routed under the right arm as it may
cause entanglement during emergency egress.
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Figure 20 HDU Lens Adjustment
e. HDU combiner lens adjustment
(1) The HDU must first be rotated in front of the crewmember’s eye. This is
accomplished by releasing the friction on the adjustable mount.
(2) Once the friction is removed, the CRT assembly is free to rotate up/down and/or
in/out dependent on the individual crewmember’s facial features.
(3) The HDU plastic housing will rest slightly on the individual’s cheek when adjusted
properly in front of the right eye. The HDU is free to rotate up and out of the way
of the crewmember’s eye when rotating within the adjustable mount.
(4) Reapplying friction to the adjustable mount will maintain the current position of
the HDU over the crewmember’s right eye. The HDU combiner lens is then
moved up or down on the sliding clip to center the combiner lens on the right eye.
(5) When the HDU is correctly positioned in front of the crewmember’s eye, the
symbology and the FLIR image can be adjusted to an optimum setting. This will
allow the crewmember to see the correct FLIR image (1:1 real world/FLIR image
ratio) and all IHADSS symbology.
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(6) HDU rotation stops are provided so that the HDU, when flipped up, does not
swing back and dangle from its mount. A rotation stop is also provided so that
the HDU does not rest completely on the crewmember’s cheekbone when the
HDU is down.
(7) The HDU can slide forward (away from the crewmember’s face) or back (towards
the crewmember’s face). This allows the individual pilots to establish how far
away the HDU sits from the face.
(8) Once the HDU is positioned at the correct distance in front of the crewmember’s
right eye and is vertically positioned, it must be adjusted horizontally (left or right)
so that the combiner lens is centered in front of the eye.
(9) The combiner lens is attached to the HDU by a sliding clip. This sliding clip
allows for the movement of the combiner lens left and right for correct positioning
directly in front of the crewmember’s right eye.
f. Check for freedom of movement.
(1) It is important to check for obstructions and freedom of movement of the HDU to
ensure that the HDU will not come in contact with objects or be blocked during
scanning.
Check on Learning
1. Where is the Helmet Display Unit (HDU) stowed?
ANSWER: ________________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. What does the HDU cable assembly connect to?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
3. How should the HDU cable assembly NOT be routed?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
4. What is the purpose of the combiner lens sliding clip?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
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C. ENABLING LEARNING OBJECTIVE 3
ACTION: Identify the characteristics for boresighting the IHADSS.
CONDITIONS: Given a written test without the use of student notes or references.
STANDARDS: In accordance with TM 1-1520-251-10-2, TM 1-1520-251-CL-2,
and TC 1-251.
1. Learning Step/Activity 1. Identify the characteristics for boresighting the IHADSS.
Figure 21 Pilot/CPG WPN UTIL Pages
a. IHADSS enable
(1) The IHADSS will power up automatically when the aircraft is being powered by
the Auxiliary Power Unit (APU), but will remain off if powered up using an
Aviation Ground Power Unit (AGPU). System operation and/or initialization can
be verified on the WEAPON UTILITY (WPN UTIL) page.
(2) The IHADSS on/off option is located on the WPN UTIL page and is a common
option. If one crewmember selects the system on or off, it affects the system in
both crewstations.
(3) Once the IHADSS is operational, each crewmember must optimize their HDU.
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Figure 22 IHADSS Grayscale
b. IHADSS optimization
(1) General
(a) IHADSS optimization is the adjustment of the projected image on the
combiner lens from the HDU CRT.
(b) When NVS is used, IHADSS optimization would be the combination of
the FLIR image and symbology that the crewmember would have to set
up correctly. If the NVS is not being used, the crewmember would be
optimizing just the symbology displayed on the combiner lens.
(c) To begin optimizing, the crewmember must first establish what is
referred to as a ―grayscale‖ on the combiner lens.
(2) Grayscale
(a) The grayscale can only be turned on from the MPD WPN pages. It is
only displayed on the top level MPD WPN page (no Weapon buttons
selected or weapons actioned).
(b) The grayscale option is an independent selection for each crewmember.
If the GRAYSCALE option is selected, the grayscale symbology will be
displayed on the crewmember’s combiner lens.
(c) Once the GRAYSCALE option is selected, it will remain displayed on the
crewmember’s HDU until the option is deselected by the crewmember.
(d) The grayscale is a rectangular symbology box with center horizontal
lines that are used as a reference to properly size and center the image
and/or symbology displayed on the crewmember HDU.
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(e) The two grayscale areas on the display represent 10 separate shaded
areas that the crewmember uses to establish the proper brightness and
contrast for the FLIR image that will be projected onto the combiner lens.
(f) The four vertical centerlines and one horizontal line that run through the
center are used to establish the correct focus for the crewmember’s
individual visual acuity.
(3) Establishing a proper grayscale
(a) With the grayscale displayed on the HDU, the crewmember must
establish the proper settings.
Figure 23 Focusing and Leveling
(b) The first thing to do is level the grayscale relative to the airframe..
(c) As the crewmember views the grayscale displayed on his/her HDU, the
image rotation collar can be turned to level the grayscale image with the
airframe.
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Figure 24 CPG’s TDU and Pilot’s VIDEO Panel
(d) Once the grayscale is level, the crewmember must adjust it for the
proper brightness.
(e) Using the brightness and contrast controls either on the pilot VIDEO
panel or the TADS Electronic Display And Control (TEDAC) bezel panel,
the crewmember must establish a brightness and contrast that presents
the best brightness and resolution of the image displayed on the HDU
combiner lens.
1) The crewmember first adjusts brightness and contrast all the way
down. From this setting, the brightness control can be adjusted
first.
2) The brightness control is adjusted up until there is a little
backlighting—a faint glow—and the grayscale image is visible.
(f) After the brightness setting is established, the crewmember adjusts the
contrast control up to a setting that breaks out the 10 shades of the
grayscale. The top block in both columns should be approximately the
same shade as the background.
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Figure 25 DAP and HDU Focus Controls
(g) With the grayscale displayed, the crewmember adjusts the focus using
the HDU infinity focus collar on the HDU.
(h) The crewmember adjusts the mechanical focus collar on the HDU and, if
necessary, the electronic focus potentiometer on the DAP for the best
focus.
(i) When the FOV is properly focused, the crewmember can clearly
distinguish the center raster lines while viewing the display.
(j) When the center focus lines are adjusted for best clarity, the
crewmembers are ready to adjust the grayscale for proper sizing and
centering both in the horizontal and vertical axes.
(k) This establishes the proper image size for display of symbology and/or
sensor.
(l) If symbol brightness is advanced to full bright, the symbols will appear
blurred and possibly be misinterpreted as an out-of-focus condition.
(m) If the crewmember judges the HDU to be out of focus, the infinity focus
ring on the aft portion of the HDU should be adjusted.
(n) Focusing the HDU at anything less than infinity will result in muscular
tension and eyestrain occurring within a short time, causing eye pain,
headaches, or both.
(o) If this condition is not corrected, degradation in crewmember
performance may occur.
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Figure 26 Sizing and Centering
(4) Sizing and centering
(a) With the grayscale displayed on the combiner lens, the crewmember
must properly size and center the grayscale symbology. The grayscale
symbology represents the edges of the symbology display area. It is
important that the crewmember ensure that the combiner lens is correctly
positioned (centered).
(b) Sizing and centering of the HDU grayscale is similar to sizing and
centering a computer screen.
(c) A 30° by 40° FOV is presented to the crewmember with sizing and
centering adjusted correctly. Sizing and centering is accomplished as
follows:
1) Correctly position the combiner assembly.
2) Adjust brightness and contrast to full on (clockwise). This allows
the crewmember to see the mask on the field flattener lens by
lighting the grayscale background. The field flattener lens, on
the face of the CRT, has a mask (dark border). It is used as a
reference during sizing and centering.
3) Observe the white outer border of the grayscale. If the border is
adjacent to the mask on the field flattener lens on all sides, no
adjustment is required. The crewmember must move the eye left
and right to see the mask and border.
4) Adjust horizontal sizing and centering potentiometers as
necessary to make the grayscale border top and bottom,
adjacent to the mask. The horizontal sizing and centering is
accomplished using the top two rheostats on the DAP labeled
SIZE and Centering (CTRG).
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5) Adjust the vertical sizing and centering potentiometers as
necessary to make the grayscale border top and bottom adjacent
to the mask. The vertical sizing and centering is accomplished
using the two middle rheostats on the DAP labeled SIZE and
CTRG.
6) The location of the DAPs makes it difficult for crewmembers to
make adjustments for proper sizing and centering while seated in
the aircraft. Maintenance personnel should be available for this
adjustment.
7) IHADSS boresighting is required after any sizing and centering
adjustment.
(5) After the crewmember completes the sizing and centering adjustments, all
symbology should be visible.
(6) After sizing and centering of the grayscale adjustments, any loss of symbology is
a result of:
(a) Improper helmet fit
(b) Display position
(c) Combiner extension
(d) Wearing of eyeglasses
(7) Through practice and experience, crewmembers will have less difficulty
accomplishing the sizing and centering of their displays.
(8) A good helmet fit is important not only for crewmember comfort but also for
maintaining proper boresight. A comfortable helmet fit helps to eliminate display
movement and/or helmet shifting.
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Figure 27 Infinity Focus
(9) Infinity focus check
(a) Infinity focus check is a condition of focus at the HDU, where the FLIR
image and flight symbology are perceived to be focused. A good focus
is achieved while the human eye viewing through the HDU focuses on an
object at least 200 feet away.
(b) The human eye is more relaxed while focused at infinity. For that
reason, the PNVS FLIR is designed, electrically and mechanically, to
provide imagery to the HDU at an infinite focus.
NOTE
The focus ring on the HDU compensates for the variation in visual acuity among aviators. The
infinity focus ring/collar allows each individual to focus the image to infinity.
(c) If the crewmember judges the HDU to be out of focus, the manual focus
ring on the aft portion of the HDU should be adjusted.
NOTE
Focusing in on anything less than infinity cannot be maintained for a prolonged duration without
creating eyestrain and other negative effects.
(d) If this condition is not corrected, degradation in crewmember
performance may occur.
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Figure 28 Armament Datum Line
c. IHADSS LOS
(1) A primary function of the IHADSS is to establish the crewmember LOS in
reference to the aircraft ADL. This is referred to as establishing an electronic
LOS.
(2) The ADL is established along the aircraft longitudinal axis and is a 0° azimuth, 0°
elevation line that extends through the aircraft.
(3) The ADL is elevated to a point that equals approximately +4.9° when referenced
from the aircraft on a flat surface. At a hover, the ADL is approximately the
same.
(4) Once the crewmember’s electronic LOS is established, continuous head
positioning is provided to the WP.
(5) As crewmembers move their heads in azimuth and elevation, the IHADSS
interprets the crewmembers’ LOS and continually provides the crewmember’s
head position (LOS) to the WPs for processing.
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d. IHADSS WP Functions
(1) The WP is the primary bus controller for the Sighting and Weapons Systems.
(2) Crewmember head movement is constantly interpreted and sent to the WPs.
(3) The WP processes crewmember LOS for:
(a) Sensor pointing
(b) Symbol generation
(c) Ranging
(d) Weapons aiming
e. IHADSS boresight
(1) The actual IHADSS boresight procedure begins after:
(a) The crewmember is seated in the crewstation.
(b) Crewmember’s helmet connected to the aircraft.
(c) Crewmember’s helmet fastened to head.
(d) HDU mounted to the helmet.
(e) Aircraft is powered (usually performed under APU power).
(f) IHADSS system is on.
(g) Sizing and Centering adjustments are complete.
(2) With the HDU donned and the combiner lens positioned in front of the
crewmember’s eye, the crewmember will observe the flashing dots around the
LOS and the message IHADSS BORESIGHT REQUIRED HAD message
flashing. This indicates that a boresight has not been accomplished.
WARNING
Offset boresighting is not authorized.
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Figure 29 WPN Page
(3) When the crewmember is ready to perform the IHADSS boresight procedure, he
must first select the WPN page either from the MENU page or from the WPN
Fixed Action Button.
(4) The crewmember must ensure that there are no weapons actioned or selected
from the bottom of the WPN page. If the crewmember fails to ensure this, the
―top level‖ WPN page format is not presented and the BORESIGHT page option
is not displayed.
(5) From the WPN page, the crewmember then selects the BORESIGHT page.
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Figure 30 Pilot and CPG Boresight Page
(6) When the BORESIGHT option is selected, the BORESIGHT page will be
displayed.
(7) The BORESIGHT page format displayed will be determined by whether the
crewmember is selecting it from the pilot or CPG crewstation.
(8) The CPG BORESIGHT page provides access for accomplishing the TADS
boresight procedures. This is not accessible from the pilot crewstation.
NOTE: TADS boresight will be discussed in the Sighting System lesson.
(9) With the Boresight page displayed, the crewmember selects the IHADSS option.
(10) The IHADSS boresight option must be selected to initiate the IHADSS boresight
procedure.
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Figure 31 Pilot Boresight Page
(11) When the NVS mode is NORM and the IHADSS option is selected, the NVS will
position to the BRU LOS (0° azimuth -15° elevation).
(12) The BRU in that crewstation is illuminated and the intensity of the BRU is
adjusted using the PRIMARY rheostat on the lighting panel.
(13) Once the crewmember has adjusted the intensity of the BRU to the desired
brightness, he is ready to complete the IHADSS boresight procedure.
(14) The IHADSS boresight option keeps the selected sensor fixed forward until the
boresight procedure is complete or until the IHADSS boresight option is selected
off.
(15) The IHADSS boresight is automatically selected off if the crewmember leaves the
BORESIGHT page and selects another MPD page. This keeps the crewmember
from inadvertently leaving the IHADSS fixed forward.
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Figure 32 LOS Reticle Alignment with BRU
(16) To boresight the IHADSS to the ADL, the crewmember aligns the IHADSS LOS
to the center of the BRU concentric circles. The color of the BRU concentric
circles as viewed through the HDU should have a red tint.
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Figure 33 B/S NOW Select
(17) When the LOS is properly aligned, the crewmember must press the B/S NOW
button on the WPN BORESIGHT page.
(18) The following actions occur upon selection of the B/S NOW button on the MPD:
(a) Boresight correctors are established at the SEU.
(b) LOS cueing dots stop flashing.
(c) IHADSS B/S REQUIRED message and IHADSS LOS INVALID
messages are no longer displayed in the sight status area of the HAD.
(d) BRU is turned off.
(e) IHADSS boresight enable option is deselected.
(19) The SEU stores the boresight bias until the crewmember shuts off electrical
power to the IHADSS or again actuates the IHADSS Boresight switch while in the
Boresight mode. Each crewmember must boresight the IHU before operating the
system so that the SEU will know what bias to apply during operational
computations.
(20) Once crewmembers have successfully completed IHADSS boresighting
procedures, they may adjust their seat heights as desired for flight. However, the
IHU must remain within the motion box.
(21) If necessary, crewmembers may disconnect and then reconnect the IHU
electrical connector. This action will not affect the stored boresight bias.
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Figure 34 HMS Subsystem Operation
f. IHADSS helmet-mounted sight operation
(1) Three points in space define crewmember LOS when boresighting:
(a) Design eye position
(b) HDU crosshair reticle
(c) BRU target
(2) In the Boresight mode, the SEU measures the nonparallel condition between the
imaginary LOS(s), which are imaginary straight lines between the two sets of left
and right IHU IR detectors; the straight line created by the design eye position;
the HDU crosshair reticle; and the BRU target.
(3) The ―minor‖ misalignment between the crewmembers LOS and the electronic
LOS of the helmet is then applied to the crewmember’s operational mode LOS as
a bias correction factor.
(4) The visual LOS of the user is that LOS seen through the center of the video
display on the combiner lens of the HDU.
(5) After the crewmember completes the boresighting procedure, the HMS will be
capable of measuring the electronic LOS of the infrared detectors and the IHU.
(6) Likewise, the HMS is capable of factoring-in the boresight bias and of providing
the PNVS with an accurate electronic duplication of the crewmember’s visual
LOS.
(7) If PNVS components are functioning properly, the PNVS should point along the
LOS determined by the crewmember.
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(8) To ensure system accuracy, the crewmember should perform a registration
check.
(9) Offset boresighting is boresighting the IHADSS to anything other than the aircraft
ADL and is not authorized at any time.
g. Factors that prevent a crewmember from achieving a successful IHADSS boresight
(1) There are many factors that can affect the capability of the crew to achieve a
successful IHADSS boresight. These include:
(a) One or both SSUs are inoperative or malfunctioning.
(b) IR detectors are operating intermittently or are totally inoperative.
(c) IHU electrical connector is improperly connected.
(d) IHU fits improperly.
(e) HDU is positioned improperly.
(f) Display is not centered properly.
(g) IR detector to HDU alignment error is in excess of 3°.
(h) Direct sunlight enters an open cockpit door.
(i) Establishing an LOS using binocular versus monocular vision.
(j) Seat is improperly adjusted.
(k) Helmet is too far aft of the motion box.
(2) If an IHADSS boresight is in question, the crewmember may attempt another
boresight. However, if the boresight is not achieved, the crewmember should not
use the HMD as a sight as this will create inaccurate pointing of the sight/sensor
and/or weapon systems.
h. Factors that can cause a disparity between electronic LOS and the visual LOS
(1) Once the IHADSS boresight procedure has been accomplished, there are many
factors that can affect the alignment of the electronic LOS and the visual LOS.
These include, but are not limited to, the following:
(a) IR detector pairs and the HDU mounting pad on the helmet may be
misaligned.
(b) The HDU mounting clip may not hold the HDU in proper alignment.
(c) HDU combiner may not be properly aligned.
(d) CRT image may not be properly centered.
(e) CRT in the HDU may be misaligned with the HDU body.
(2) If a disparity is noted by the crewmember between the electronic LOS and the
visual LOS, the IHADSS should be considered defective and not used for
sight/sensor aiming and/or weapons pointing.
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Figure 35 Registration Check
i. Registration check
(1) After IHADSS boresighting has been performed, a registration check is required
to ensure that the NVS is looking at the same point as that of the crewmember’s
eye.
(2) When crewmembers boresight the IHADSS, they electrically correct for minor
errors between the visual LOS and the electronic LOS of the IHU.
(3) If the crewmember’s helmet shifts after boresighting, the relationship between the
visual LOS and the IHU electronic LOS has changed. This can result in a
perceivable difference between where the crewmember is looking and where the
NVS turret is pointing.
(4) The registration check is designed to confirm that the aided eye LOS and the
NVS turret LOS are aligned. To perform proper registration, the crewmember
should do the following:
(a) Prior to proceeding with the registration check, the CPG should verify
PNVS and TADS Captive Boresight Harmonization Kit (CBHK)
correctors. A proper registration check will not occur if the PNVS and
TADS correctors are incorrect or different from the logbook values.
(b) Aviators are only authorized to verify and correct CBHK values to the
current CBHK values as recorded in the logbook.
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(c) Align the NVS with an object along the 0° Azimuth (AZ) and 0° Elevation
(EL) line (represented by the head tracker symbol). TM 1-1520-251-10,
Chapter 4, authorizes ±5º degrees of azimuth. The object being used
should be at least 90 feet in front of the NVS turret. If the object is not
aligned to the ADL or is closer than 50 feet, accurate registration will not
be possible because of parallax.
(d) View the real-world object with the aided eye through the combiner lens
by centering the NVS LOS over the object. This is accomplished after
the crewmember properly aligns the aircraft and the selected object.
(e) If the real-world, through-the-lens view of the object and the FLIR image
of the same object are superimposed, the NVS is properly registered.
Figure 36 Registration Check at Night
(5) Registration check at night
(a) At night, the registration point is an individual stationed at the front of the
aircraft within the head tracker symbol.
(b) This individual holds a flashlight visible to the crewmember. The light is
held in the center of the torso. This allows the crewmember to determine
the real world and image alignment. By viewing the flashlight, the
crewmember is able to determine the registration point in a darkened
environment.
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Figure 37 LOS Reticle
(6) Specifications allow for an approximate displacement (alignment differential) of
the thermal image and reference object being used to perform the check. The
allowable registration error is 1 foot of azimuth or elevation at 90 feet. The center
open position of the LOS reticle is equivalent to 1 foot at 90 feet. Use the
opening between the LOS from 3 and 9 o’clock for azimuth error and opening
between the LOS from 6 and 12 o’clock for elevation error.
Figure 38 Registration Check In/Out of Tolerance
(7) If the real world image and the FLIR image are not superimposed within the
specification limit during the registration check, the crewmember must perform
the boresight alignment again.
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Figure 39 DMS UTIL Page
(8) Selection of the DMS UTIL (Data Management System Utility) page offers the
crewmembers an opportunity to verify system operation. WP SEL (Select)
provides the means to select between WP1 Single or WP2 Single Operation, but
are not selectable when the aircraft is in the air. To verify Boresight system
operations select the opposite WP and attempt another Boresight. If successful,
then the original WP is in error. If still unsuccessful, then the Boresight system is
in error. Findings must be reported to maintenance personnel.
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Figure 40 Unity Magnification Check
j. Unity magnification check
(1) Unity magnification is a one-to-one size relationship between objects observed
on the HDU and their real-world counterparts.
(2) The size of a tree or building viewed on the HDU is judged identical to the size of
the actual object viewed directly without the HDU.
(3) A crewmember under Visual Meteorological Conditions (VMC) perceives
distances to objects and closure rates through:
(a) Three-dimensional
(b) Wide FOV
(c) Binocular vision (good depth perception)
(4) A crewmember flying with an NVS views the world through:
(a) Narrow FOV FLIR
(b) Two-dimensional monocular display (poor depth perception)
(5) The absence of the third dimension, which provides depth perception, and the
restricted FOV of the sensor, necessitates a new method for perceiving distances
and closure rates.
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Figure 41 Narrow FOV Effects
(6) The adverse effects of a narrow FOV sensor are compensated for through turret
slewing. This provides the crewmember with a total Field of Regard (FOR) much
larger than the FOV.
(7) The loss of depth perception is compensated for through the observation of size
and the relative changes in the size of objects visible on the display.
(8) In this manner, the crewmember obtains a panoramic view of the terrain by
turning the head, and judging distances and closure rates by the size and relative
changes in the size of objects visible within this viewing area.
(9) Because a crewmember using NVS must rely on perceived object size on the
display for depth perception information, they must operate the NVS at the
proper unity magnification.
(10) Objects visible in the thermal scene viewed by the crewmember must appear to
be the same size as when viewed unaided from the same perspective point as
the FLIR sensor.
(11) Unity magnification exists only when the crewmember HDU projects thermal
imagery to the crewmember’s eye in a 30° by 40° format.
(12) This format matches the FOV of the FLIR sensor and provides a one-to-one
relationship between the display FOV and the sensor FOV.
(13) The one-to-one relationship between the crewmember’s view of the thermal
image and the FLIR view of the real world is affected by DAP adjustments.
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Figure 42 Unity Magnification
(14) These adjustments are usually required only when the HDU or DAP is replaced.
The crewmember can ensure a 30° by 40° format is present on the HDU by
selecting the grayscale and noting the position at the boundary lines surrounding
the grayscale bars. When properly adjusted, these lines are at the limits of the
display. Additionally, the corners of the display are obscured as a result of the
40° FOV limitation of the 0.75-inch CRT within the HDU.
(15) Magnification of the FLIR imagery results when the crewmember display format
is greater than 30° by 40°. This condition causes objects in the thermal scene to
appear larger than their real-world size. This may cause a crewmember to
miscalculate the distance to the objects based on their size and perceive them to
be closer than they actually are.
(16) Conversely, display minification results when the display format is less than 30°
by 40°. This condition causes objects in the thermal scene to appear smaller on
the display than their real-world size. Again, a crewmember may miscalculate
the distance to the objects based on their size and perceive them to be farther
away than they actually are.
(17) If the crewmember properly sized and centered the grayscale during the sizing
and centering check, the unity magnification check is only a validation that the
scene displayed is in fact the proper size.
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Figure 43 Unity Magnification
(18) The technique of superimposing objects in the thermal imagery over close-
proximity, real-world objects to check for unity magnification can be misleading.
This is because of the difference in physical perspective points between the FLIR
sensor and the FLIR display (parallax effect).
(19) The crewmember may minimize the effect of parallax by orienting the view
straightforward and overlaying prominent objects on the horizon to ensure unity
magnification. This procedure may be accomplished in the Fixed Forward mode
or with the turret slaved to the crewmember IHU.
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CHECK ON LEARNING
1. Where is the GRAYSCALE option found?
ANSWER: ________________________________________________________________________
2. How many shades of gray are displayed when the grayscale has been optimized correctly?
ANSWER: ________________________________________________________________________
3. Which two adjustments are made on the Helmet Display Unit (HDU) itself?
ANSWER: ________________________________________________________________________
4. What are the two most important things to remember when performing the infinity focus check?
ANSWER: ________________________________________________________________________
______________________________________________________________________
5. Why is it important to perform the infinity focus check correctly?
ANSWER: ________________________________________________________________________
______________________________________________________________________
6. What is the aircraft Armament Datum Line (ADL)?
ANSWER: ________________________________________________________________________
______________________________________________________________________
7. What systems(s) can be boresighted from the pilot BORESIGHT page?
ANSWER: ________________________________________________________________________
8. What systems(s) can be boresighted from the CPG BORESIGHT page?
ANSWER: ________________________________________________________________________
9. Crewmembers boresight their Integrated Helmet and Display Sight System (IHADSS) to the _______.
ANSWER: ________________________________________________________________________
10. What is the maximum allowable registration check error?
ANSWER: ________________________________________________________________________
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D. ENABLING LEARNING OBJECTIVE 4
ACTION: Interpret IHADSS symbology.
CONDITIONS: Given a written test without the use of student notes or references.
STANDARDS: In accordance with TM 1-1520-251-10-2 and TC 1-251.
1. Learning Step/Activity 1. Interpret IHADSS symbology.
Figure 44 Flight and Weapons Symbology Formats
a. IHADSS symbology
(1) IHADSS symbology is displayed in one of two formats, Flight Symbology and
Weapons Symbology.
(a) Flight symbology format
1) Flight symbology consists of those symbols, scales, and digital
readouts required for pilotage.
2) Flight symbology can be displayed in each crewstation in one of
four modes: Hover, Bob-Up, Transition, and Cruise. These flight
modes are selected by crewmembers using the Symbology
Select switch on the cyclic.
3) The CPG will have flight symbology present on the HDU when
the Sight Select switch is selected HMD. If the Sight Select
switch selection is TADS and the NVS Mode switch selection is
Norm or Fixed, flight symbology will be present on the HDU.
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(b) Weapons symbology format
1) The CPG crewstation provides weapons symbology whenever it
has not been out-prioritized by flight symbology: When the
selected sight is TADS or FCR, the NVS Mode switch is set to
OFF, and the TEDAC Video Select switch is set to TADS, FCR,
or grayscale.
2) Unique weapon symbols are displayed to the crewmembers in
either format when a weapon is actioned in a crewstation.
(2) Displayed symbols follow the ―management by exception‖ rule. A symbol is not
displayed if the component supporting the symbology is not installed or is turned
off (for example: FCR not installed; therefore, FCR centerline symbology is not
present).
Figure 45 Symbology Sets
(3) IHADSS symbology can be broken down into five individual groups of
symbology, as follows:
(a) Top symbology set
(b) Right symbology set
(c) Bottom symbology set
(d) Left symbology set
(e) Center symbology set
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Figure 46 Hover mode
b. Hover mode
(1) The flight symbology format provides the crewmember with a tremendous
amount of information integrated onto one display.
(2) The Hover mode symbology is the base mode for all symbology formats. Hover
mode symbology is described first, followed by symbology that is different in the
other three modes
(3) Some symbology is edge-limited, which means that if information that the
symbology represents is beyond the physical limits of the IHADSS display area,
the symbology will move to the edge of the display and remain until the source of
the information is back within the IHADSS FOV. Other symbols are not edge-
limited and will not be displayed if outside the current IHADSS display area.
(4) Top callouts
Figure 47 IHADSS Symbology – Top callouts
(a) Heading scale
1) The heading scale is centered in the top area of the display. The
moving scale has a total range of 360º.
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2) It displays an instantaneous 180º in 10º increments. The major
cardinal points are labeled N, S, E, W and every 30º point is also
labeled.
3) Current magnetic heading is located in the center of the heading
scale within a status window. It is displayed as three numerals
indicating the current heading of the aircraft to the degree (for
example: 091).
4) The heading scale is presented after the Embedded Global
Positioning System Inertials (EGI) have determined its true
heading and has a position for determining magnetic variance.
5) The heading scale will not be displayed if EGI information is not
valid or EGIs have failed.
(b) Command heading
1) The command heading chevron symbol along the bottom of the
magnetic heading scale indicates the heading to the next
navigation waypoint as selected from the Tactical Situation
Display (TSD).
2) The command heading will move automatically to the next
waypoint within a route when the aircraft has passed the current
waypoint.
3) The symbol is presented when there is a valid next waypoint and
the heading scale is presented.
4) The symbol is edge-limited. If the waypoint is beyond the
instantaneous heading scale, it will be displayed at the 90º point
from the lubber line.
(c) FCR centerline bearing
1) The FCR centerline bearing is displayed along the bottom of the
magnetic heading scale.
2) It represents the azimuth of the current FCR centerline (or line of
bearing) relative to the aircraft centerline when the centerline is
within the displayed portion of the heading scale.
3) The FCR centerline bearing is presented when the heading scale
is presented and the FCR footprint is shown on the TSD page.
(d) Alternate sensor bearing
1) The alternate crewmember sensor bearing is a filled chevron
displayed at the bottom of the heading scale and indicates the
opposite crewmember-selected LOS with respect to the heading
of the aircraft.
2) It is only presented when the heading scale is presented and the
opposite crewmember’s sight is valid.
3) This allows one crewmember to see the other crewmember’s
selected sensor LOS relative to the aircraft heading.
4) The symbol is not presented in a crewstation when the other
crewmember’s selected sight is FCR.
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(e) Automatic Direction Finder (ADF) bearing symbol
1) The ADF bearing is an ―inverted lollipop‖ symbol presented along
the bottom of the magnetic heading scale, representing the
current bearing to the tuned Non-Directional Beacon (NDB).
2) It is displayed only when a valid bearing signal is received by the
ADF system and the heading scale is presented.
3) The ADF symbol is edge-limited and will move to the edge of the
display that represents the shortest direction to the currently
tuned NDB.
(f) Lubber line
1) The lubber line is aligned to the centerline of the aircraft.
2) It is the reference for both heading and angle of bank.
3) The lubber line will not be displayed if EGI information is not
valid or EGIs have failed.
Figure 48 IHADSS Symbology – Right callouts
(b) Radar altitude HI/LO indicators
1) The radar altitude HI and LO indicators are displayed just above
and below the radar altitude digital readout.
2) The HI and LO indications can be set to be displayed when the
altitude is between 1 and 1420 feet Above Ground Level (AGL)
(1428 feet actual).
3) If the HI or LO indications are set to 0, they are not presented to
the crew.
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4) HI and LO settings are set on the FLT page with the SET option
selected.
(c) Vertical Speed Indicator (VSI) – rate of climb/descent indicator
1) The rate of climb scale and indicator triangle are located to the
left and adjacent to the radar altitude vertical scale.
2) The scale is presented with a triangle pointer indicating the
current rate of climb/descent. Tic marks designate rates of climb
or descent at 100 fpm increments to 500 fpm. A single tic mark
designates the 1000 fpm.
(d) Radar altitude digital readout and analog scale (tape)
1) The radar altitude is presented with a digital readout and analog
tape in the center right area of the page.
2) Radar altitude is displayed as a digital readout in 1 foot
increments from 0 to 50 feet AGL and 10 foot increments from
50 feet AGL to a maximum altitude of 1420 feet AGL.
3) The radar altitude vertical scale is composed of a moving vertical
tape displayed along an analog scale corresponding to the radar
altitude when the aircraft is operating at altitudes between 0 feet
and 200 feet (climbing), or 10 and 180 feet (descending).
4) When the aircraft climbs above 200 feet, the analog tape will not
be displayed. It will reappear when the aircraft descends below
180 ft.
5) The analog scale has tic marks to the right of the tape in 10 foot
increments up to 50 feet, and 50 foot increments from 50 feet to
200 feet. The left side of the tape, which is used for the vertical
rate of climb indicator, has tic marks which correspond to 100
feet per minute rate of climb and rate of descent but can also be
used to represent 10 foot increments for the radar analog tape.
6) The radar altitude digital readout and scale are not presented
when:
a) Radar altitude data is not valid
b) Radar altitude exceeds 1420 ft.
c) Radar altimeter is not powered on
d) Out of range
7) Rate of descent digital readout
a) When the rate of descent exceeds 1000 fpm, a data field
indicating the current rate of descent is presented
adjacent to the VSI triangle.
b) The data field presents the rate of descent to the nearest
100 fpm.
c) As the rate of descent decreases to less than 600 fpm,
the digital readout will not be displayed.
d) Rates of descent are not presented if the EGI is not
providing valid vertical speed information.
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(e) Altitude hold
1) When the Flight Control System is attempting to hold altitude, a
horizontal ―homeplate‖ symbol is placed at the zero rate of climb
symbol position as the altitude hold symbol.
2) If the Hold mode fails or is disengaged, a flight controls tone is
initiated and the symbol flashes for 3 seconds and is then
removed.
Figure 49 IHADSS Symbology – Bottom callouts
(6) Bottom callouts
(a) Skid/slip ball
1) The skid/slip ball provides an indication of the amount of side
acceleration and how well a turn is coordinated.
2) Reference lines represent the limits for in-trim or coordinated
flight.
3) If inertial acceleration is not available (the EGI data is not valid),
the skid/slip ball or ground speed are not presented.
(b) Field Of Regard (FOR)
1) FOR is a box representing the selected sensor and is displayed
at the bottom, representing the total gimbal limits of the
crewmember's selected sensor.
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a) The pilot FOR contains the pilot's HMD FOV, Cued LOS
Dot, FCR Current Centerline, and FCR Last Scan
Centerline.
b) The CPG FOR contains Cued LOS Dot, a FCR Current
Centerline, and a FCR Last Scan Centerline.
1 If the CPG selected sight is TADS or FCR, the
CPG FOR also contains the TADS FOV box.
2 If the CPG selected sight is HMD, the FOR also
contains the HMD FOV box.
2) The PNVS FOR represents the total possible FOR (gimbal limits)
of the PNVS.
3) The TADS FOR represents the total possible FOR (gimbal limits)
of the TADS.
(c) Cued LOS dot
1) The Cued LOS dot is a dynamic symbol displayed within the
FOR.
2) It represents the active acquisition source relative to the aircraft
ADL.
3) It is edge-limited to the current FOR.
(d) FOV box
1) The FOV box is a small, dynamic box displayed within the FOR.
2) It represents the real-time FOV relative position within the FOR,
based on the crewmember's selected sight and FOV. It is edge-
limited to the currently displayed FOR.
3) The FOV box represents the pilot HMD on the pilot flight formats.
4) The FOV box represents the CPG HMD or TADS on the CPG
formats.
5) The FOV represents the CPG HMD when the CPG-selected
sight is HMD. It represents the TADS when the CPG sight is
TADS or FCR.
(e) FCR current centerline
1) The FCR current centerline is a solid, vertical line within the
currently presented sensor FOR.
2) This line represents the current centerline of the selected scan
size about which the FCR will scan.
3) The FCR current centerline is not presented if the heading is not
valid or the FCR is not valid.
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(f) FCR last centerline
1) The FCR last scan centerline is a dashed, vertical line displayed
within the sensor FOR.
2) The FCR last scan centerline is displayed to represent the FCR
centerline of the most recent scan for which target information is
currently being displayed.
3) The FCR last scan centerline is only visible when the current
centerline has been repositioned from the azimuth of the most
recent scan.
4) Once a new scan is initiated, the FCR last centerline is removed
from the display.
Figure 50 IHADSS Symbology – Left callouts
(7) Left callouts
(a) Airspeed digital readout
1) The true airspeed in knots is presented in the left middle area of
the page.
2) The airspeed becomes boxed to indicate the airspeed has
reached Velocity Not to Exceed (VNE).
3) The valid airspeed range is 0 to 210 Knots True Air Speed
(KTAS) in 1 knot increments.
4) If airspeed data is not available, airspeed is not presented.
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(b) Attitude Hold mode
1) When the Flight Control System is attempting to hold attitude, a
status window is placed around the airspeed readout to indicate
attitude hold.
2) Attitude Hold mode should not be confused with the VNE
airspeed box that appears around the airspeed when the aircraft
is exceeding VNE.
3) If the Hold mode fails or is disengaged, a flight controls tone is
initiated and the symbol flashes for 3 seconds and is then
removed.
(c) Engine torque
1) The engine torque is presented as a digital readout in the upper
left area of the display.
2) It indicates the highest engine torque of the two engines.
3) When a greater than 12% (difference) torque split occurs
between engines, the torque flashes to indicate impending single
engine operation.
4) The torque is boxed when 98% or higher for dual engine,
indicating an impending continuous torque limit of 100%.
5) For single engine, 108% or higher will be boxed and will flash.
(d) Engine Turbine Gas Temperature (TGT)
1) The engine TGT digital readout is presented in the upper left
area of the display below the torque indication.
2) It is only presented when two minutes remain in any particular
TGT limit range (e.g., after TGT has been in the 30 minute range
for 28 minutes).
(e) Force of Gravity (G) status
1) A digital indication of the experienced vertical acceleration will be
displayed when:
a) Aircraft is within 0.25G of the current acceleration limit
b) Aircraft exceeds the 0.3G to 2G normal operating region
2) The acceleration limit is dynamic and determined for the current
altitude, velocity, and gross weight conditions.
3) The G status digital readout is located near the airspeed digital
indication for easy reference in flight.
4) Once the G status digital readout is presented, it will remain
displayed for a minimum of 2 seconds prior to removal to prevent
the symbol from appearing to flash.
(f) Selected PNVS Sensor
1) The PNVS selected sensor data field presents the name of the
selected PNVS sensor: TV or FLIR.
2) The selected EOCOM FLIR filter is incorporated into this status:
1FLIR (filter 1), 2FLIR (filter2), or FLIR (clear).
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3) TV status is a growth provision for an image intensification
system.
Figure 51 IHADSS Symbology – Center callouts
(8) Center callouts
(a) Cueing dots
1) Cueing dots appear at all four tips of the LOS reticle and flash
when the IHADSS B/S REQUIRED message is present within
the High Action Displays Sight Status field.
2) Cueing dots are displayed at the outer tips of the LOS reticle to
indicate the quadrant containing the currently selected
acquisition source.
3) A cueing dot appears at the upper or lower tip of the reticle when
a change in elevation is required and appears at the left or right
tip when a change in azimuth is required.
4) The cueing dots do not appear when the acquisition source is
within 4º of the LOS.
(b) Acceleration cue
1) The acceleration cue provides magnitude and direction indication
of the aircraft acceleration relative to the end of the velocity
vector.
2) It is a small, dynamic, open circle displayed in the center area of
the format.
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3) It moves about the format to indicate aircraft longitudinal and
lateral acceleration.
4) The origin of the acceleration cue is:
a) The outer end of the velocity vector when the vector is at
less than maximum scale (edge of format).
b) The center of the LOS reticle when the velocity vector is
at or greater than maximum scale.
5) In Transition mode the acceleration cue is always referenced to
the tip of the velocity vector.
(c) Velocity vector
1) The velocity vector symbol is used to indicate the magnitude and
direction of the aircraft velocity relative to the nose of the aircraft.
2) The velocity vector is a solid line displayed in the center of the
format.
3) The origin is the center of the LOS reticle.
4) The line orients in the direction of the aircraft movement
according to the direction and severity of motion acting on the
aircraft at that instant.
5) It extends and withdraws (in length) from the origin to indicate
longitudinal and lateral velocities of ground movement.
6) The velocity vector and acceleration cue:
a) Flash when an inertial velocity error greater than 1 foot
per second exists.
b) Blank when inertial data is not valid.
c) Are not displayed in the Cruise mode.
7) The information is derived from the EGIs.
8) The velocity vector ―saturates‖ based on the symbology mode
selected.
a) In the Hover mode, it is fully extended when the aircraft
reaches a velocity of 6 knots.
b) In the Transition mode, it is fully extended when the
aircraft reaches a velocity of 60 knots.
(d) Head tracker
1) The Head Tracker is a virtual broken diamond symbol displayed
in the center area of the format.
2) The Head Tracker is displayed when it moves within 30º
vertically and 40º horizontally about the nose of the aircraft.
3) Movement on the format indicates the crewmember's head
position (LOS) relative to the centerline of the aircraft.
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(e) LOS reticle
1) The LOS reticle is a crosshair located in the center area of the
flight format.
2) It represents the LOS of the crewmember when the selected
sight is HMD or TADS and is used as an aiming reticle.
3) It is also used as a reference for boresighting as well as for the
head tracker, horizon line, velocity vector, acceleration cue, and
the hover position box.
4) The LOS reticle flashes when the crewmember LOS is invalid or
the selected PNVS or TADS sensor is at its gimbal limit.
5) It also flashes when the gun is the selected weapon and the gun
system has failed or is not tracking the crewmember’s head.
(f) Cued LOS reticle
1) The cued LOS reticle is a dashed crosshair symbol, which
represents the crewmember’s active acquisition source.
2) The cued LOS reticle is only presented when the selected sight
and acquisition are valid and CUEING is selected on.
3) The cued LOS reticle can be driven off the display.
(g) Video Degraded/Frozen Status
1) The VIDEO DEGRADED or VIDEO FROZEN status is displayed
when the respective condition is detected.
2) The message is displayed as confirmation that the condition
exists.
Figure 52 Symbology Select Switch
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Figure 53 Bob-up Mode
c. Bob-up mode. Flight symbology displayed can be changed by either crewmember using
the cyclic symbology select switch. Bob-Up mode symbology includes the symbols
displayed in the Hover mode plus the following symbols:
(1) Hover position (BOB-UP) box is a dynamic octagonal box.
(a) The box initializes at the position being held by the Flight Management
Computer (FMC), if operating in position Hold mode.
(b) If the FMC is not operating in position Hold, it initializes at the center of
the crewmember LOS reticle upon selection of the Bob-up mode.
(c) The bob-up box moves to indicate the position of the aircraft relative to
the spot on the earth where the box was initiated.
(d) The box shows an approximately 12-foot square area on the ground.
(e) Maximum displacement to the edge of the format represents
approximately 40 feet in any direction (laterally or longitudinally).
(f) The symbol is not presented when the inertial (EGI) data is not valid.
(2) Bob-up heading
(a) The command heading chevron symbol becomes the bob-up heading
symbol and is the heading of the aircraft upon the initiation of the Bob-up
mode.
(b) It remains at that heading until the Bob-up mode is disengaged or the
heading becomes invalid.
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Figure 54 IHADSS Symbology – Transition Mode
d. Transition mode. Transition mode symbology includes the symbols displayed in the
Hover mode in addition to the following symbols:
(1) Horizon line
(a) The horizon line is a dynamic split dashed line positioned horizontally in
the center of the format, about the center of the LOS reticle. It
represents an artificial horizon relative to the LOS reticle.
(b) The horizon line can be set on the MPD Flight page.
(c) The aircraft EGIs provide pitch and roll attitude information to determine
the (level) positioning of the horizon line of the format.
(d) The symbol moves within +30º in pitch, and hangs at the end positions of
this range for pitch attitudes greater than +30º.
(e) A dashed line positioned in the center of the format represents the
artificial horizon.
(2) Flight Path Vector (FPV)
(a) The FPV provides the crewmember an indication of where the aircraft
flight path is based on the current flight control settings and movement of
the aircraft.
(b) The FPV is a small dynamic circle with tic marks on the outer portion of
the circle at the 3, 9, and 12 o'clock positions.
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(c) The FPV is a virtual symbol on the format to indicate the outside world
reference with regard to actual aircraft flight path.
(d) The vector represents the point towards which the aircraft is flying.
(e) The horizontal difference between the head tracker and the FPV
indicates the aircraft sideslip direction and magnitude, when both are not
limited.
(f) The FPV flashes when edge is limited and is only presented when INU
velocities are valid and the 3-dimensional velocity magnitude is greater
than 5 knots.
(3) Time to Go digital readout
(a) Indicates the time it will take to reach the fly-to destination point based
on the aircraft current ground speed.
(b) Nothing is displayed when the aircraft ground speed is 15 knots or below
or the estimated time is greater than or equal to 10 hours.
(c) The second’s digits are only displayed when the estimated time is less
than 5 minutes.
(4) Destination point
(a) Indicates which waypoint, hazard, control measure, or threat/target is
currently selected as the fly-to destination point.
(b) The destination point is displayed in the lower left area of the display.
(c) The destination point numbers range from 1 to 999, preceded by one of
the following letters: Waypoint (W), Hazard (H), Control Measure (C), or
Target/Threat (T).
(d) The destination point will automatically change to the next waypoint in
the selected route when the aircraft passes within 1 minute of the
currently displayed waypoint and the aircraft passes abeam the
waypoint.
(5) Distance to go
(a) The distance remaining to the destination point is displayed to the right of
the destination point, directly above the time to go.
(b) The digital readout can be displayed in tenths of kilometers or nautical
miles.
(c) Valid range is 0– 999.9 kilometers or nautical miles.
(6) Ground Speed
(a) Ground speed is presented to the nearest knot
(b) Ground Speed is only presented when the INU is aligned.
(7) Digital Barometric Altitude
(a) The barometric altitude is established by the aircraft or changed
by the crewmember on the MPD FLT SET page.
(b) The barometric altitude is presented in feet in the upper right
area of the display.
(c) Range is from -2300 to 20,000 feet, in 10 foot increments.
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(d) Inertial altitude information will be displayed in place of the
barometric altitude if the barometric altitude cannot be
determined because of system failure.
(8) Navigation FLY-To-CUE
(a) The navigation fly-to-cue represents direction to the active next
navigation waypoint.
(b) Used in conjunction with the Flight Path Vector to aid in
navigation. When properly aligned, the Flight Path Vector will fit
within the fly-to-cue.
(c) The fly-to-cue is a small diamond shaped polygon with a flat
bottom and a dot in the center. It is virtual symbol when shown
over wide FOV imagery (HMD, TDU or MPD).
e. Cruise mode. With the exception of the acceleration cue and the velocity vector, Cruise
mode symbology includes the symbols displayed in the Transition mode, in addition to
the following symbols:
Figure 55 Cruise Mode
(1) Bank angle indicator
(a) Provides an indication of the aircraft current bank angle
(b) The bank angle triangle is aligned and fixed to the roll movement of the
pitch ladder.
(2) Attitude indicator (Pitch Ladder)
(a) Provides direct and immediate indication of the pitch attitude of the
aircraft.
(b) The pitch ladder displays 90º pitch nose down/up around the lateral axis.
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(c) The ladder appears to be solid above the center horizontal line and
dashed below the center horizontal line.
(d) The center horizontal line represents the artificial horizon of the pitch
ladder; this is not the same symbol as the horizon line.
(e) To offer less obstruction of the real-world or imagery background, 5° tic
marks used in the MPD FLT page are not presented, and the scaling has
been changed.
(3) The LOS reticle is a bold cross-hair in Cruise Mode
NOTE
The horizon line and attitude indicator horizon bar will appear to jump when changing between
transition and cruise modes. This is due to the difference in display scaling/rate of movement
between the horizon line (2:1 movement) and the horizon bar (4:1 movement).
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Figure 56 Weapons Format
f. Weapons format. The weapons symbology format is displayed in the CPG station on the
HMD, TEDAC displays, as well as on the MPD Video page. CPG switch position will
determine which symbol set will be displayed on the HMD. Components of the weapon
symbol set will be discussed at length during the individual weapon class.
CHECK ON LEARNING
1. What are the four selectable symbology modes available in both crewstations?
ANSWER: ________________________________________________________________________
_______________________________________________________________________
2. What does the Field of View (FOV) box represent?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
3. What does the head tracker symbol represent?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
4. The velocity vector saturates (fully extends) in Transition mode symbology at what ground speed?
ANSWER: ________________________________________________________________________
______________________________________________________________________
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E. ENABLING LEARNING OBJECTIVE 5
ACTION: Interpret High Action Display (HAD) messages.
CONDITIONS: Given a written test without the use of student notes or references.
STANDARDS: In accordance with TM 1-1520-251-10-2 and TC 1-251.
1. Learning Step/Activity 1. Interpret High Action Display (HAD) messages.
Figure 57 HAD Messages
NOTE: Caution must be taken when viewing the HAD messages on the Video page as this could
represent the other crewstation messages.
a. High Action Display (HAD) messages
(1) The HAD is located along the bottom and center of the IHADSS flight and
weapons formats.
(2) HAD messages are also found on the FCR and Video page when VSEL is
selected.
(3) The HAD provides very important information to the crew for use in operation of
sight and weapons systems. The messages are typically presented in priority
order based on the selected sight and/or weapon system. These messages will
assist crews in determining the status and control of the sight and weapon
systems.
(4) Crewmembers can also view HAD messages on the Video page. The following
options will display the appropriate HAD messages.
(a) CPG options (TADS, CPG HMD, or CPG SIGHT)
(b) Pilot options (Pilot HMD or Pilot SIGHT) selected or on the TEDAC display with
PNVS selected
(5) All HAD messages are independent for each crewstation.
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Figure 58 HAD Message Fields
b. Message fields
(1) The HAD is divided into eight status message fields.
(2) The status fields (sections) displayed in the HAD are:
(a) Sight select status
(b) Sight status
(c) Range and range source
(d) Weapon inhibit
(e) Weapon control
(f) Weapon status
(g) Acquisition select
(h) HMD format owner cue
Figure 59 HAD Message Additional Fields
(3) Two additional Selected Missile Side fields provide missile information when
actioned. One additional field is provided for ASE Manual Program Selection.
The Selected Missile Side and ASE Manual Program Selection fields are
discussed in the Sight and ASE System lessons. Current messages can be
found in TM 1-1520-251-10-2, Chapter 4,Table 4-7.
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Figure 60 Sight Select Status Field
(4) Sight select status field
(a) The HAD sight select status field is located on the top left of the display
field and occupies five character spaces. This field indicates the
crewmember’s selected sight.
(b) An "L" is displayed when that crewmember has the FCR and TADS
operating in a linked mode, (Example: "TADSL" or "P-FCRL").
(c) Current messages can be found in TM 1-1520-251-10-2, Chapter 4,
Table 4-12.
Figure 63 Sight Status Field
(5) Sight status field
(a) The HAD sight status field is located on the bottom left of the display field
and occupies 12 character spaces.
(b) This field provides sight status messages in the priority order based on
the crewstation and selected sight.
(c) Indicates the status of the crewmember’s selected sight and, in certain
conditions, the status of the selected NVS or weapon system
(d) Current messages for this can be found in TM 1-1520-251-10-2, Chapter
4, Table 4-3.
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Figure 64 Range and Range Source Status Field
(5) Range and range source status field
(a) The HAD range and range source status field is located on the top left of
the display field and occupies 5 character spaces.
(b) This field provides range and range source messages based on the
crewstation.
(c) Current messages for this field can be found in TM 1-1520-251-10-2,
Chapter 4, Table 4-4.
Figure 65 Weapon Inhibit Field
(6) Weapon inhibit status field
(a) The HAD weapon inhibit field is located in the center area of the display
field just above the sensor FOR box and occupies 12 character spaces.
(b) Provides an indication of safety or performance inhibit messages based
on selected weapon system including Missile, Gun, and Rocket inhibits.
(c) In addition, it will indicate the target store location and armament control
SAFE message.
(d) Current messages for this field can be found in TM 1-1520-251-10-2,
Chapter 4, Tables 4-8 (Generic Weapon Inhibits), 4-9 (Gun Inhibits), 4-
10 (Rocket Inhibits), and 4-11 (Hellfire Inhibits).
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Figure 64 Weapon Control Field
(7) Weapon control status field
(a) The Weapon Control field is located on top right of display field and
occupies 5 character spaces.
(b) This field provides the status of the selected weapon in the opposite
crewstation.
(c) Current messages for this field can be found in TM 1-1520-251-10-2,
Chapter 4, Table 4-5.
Figure 65 Weapon Status Field
(8) Weapon status field
(a) The HAD weapon status field is located on the bottom right of the display
field and occupies 12 character spaces.
(b) Provides weapon status messages based on selected weapon system.
(c) Provides indications of type, mode, and quantity remaining, when rockets
are actioned.
(d) Current messages for this field can be found in TM 1-1520-251-10-2,
Chapter 4, Table 4-6.
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Figure 66 Acquisition Select Status Field
(9) Acquisition select status field
(1) The HAD acquisition select status field is located on the top right of the
display field and occupies 4 character spaces.
(2) This field provides status of the selected acquisition source in that
crewstation.
(3) Current messages for this field can be found in TM 1-1520-251-10-2,
Chapter 4, Table 4-13.
Figure 67 HMD Format Owner Cue Field
(10) HMD format owner cue field
(a) The HAD HMD FORMAT OWNER CUE field will display in center area of the
display field, just above weapon inhibit area during single Data Processor (DP).
The field contains 10 character spaces.
(b) The HMD FORMAT OWNER CUE will indicate PLT FORMAT or CPG FORMAT.
(c) These messages will flash for 3 seconds whenever the ownership changes, and
upon entry/exit into single DP operations.
(d) During single DP operation, both crewstations share common symbology and
imagery on their HMDs.
(e) Symbology brightness is controlled by the crewmember whose symbology and
imagery is presented on both HMDs.
(f) Control of the HMD presentation is as follows:
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1) If the NVS MODE switch is OFF in both crewstations, the pilot’s
symbology and imagery will be presented on both HMDs.
2) If only one crewmember’s NVS MODE switch is NORM or FIXED, that
crewmember’s symbology and imagery is presented on both HMDs.
3) If both crewmembers’ NVS MODE switches are NORM or FIXED, the
symbology and imagery of the crewmember that last changed NVS
MODE or NVS selection will be displayed.
CHECK ON LEARNING
1. What are the HAD message areas?
ANSWER: ________________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. What does the ―L‖ following the selected sight message indicate?
ANSWER: ________________________________________________________________________
______________________________________________________________________
______________________________________________________________________
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