Geometric Design2 Aircraft

CEE 4674 - Airport Planning and Design

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Geometric Design Standards in Airport Engineering

(Part 2)

Dr. A. A. TraniAssociate Professor of Civil Engineering

Virginia Tech

CEE 4674

Airport Planning and Design


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Outline of this Presentation

•

Ground maneuvering issues

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Examples of geometric design standards

• Taxiways and taxilanes• Taxiways and runways

•

Use of CAD software


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Aircraft Maneuvering Principles

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Aircraft use tricycle landing gear configurations

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Special maneuvering requirements need to be accounted for

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Tricycle gears are less stable than four wheelers

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Tricycle gears permit tighter maneuvers

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Always consult with the aircraft manufacturer documents fro airport design


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Sample Aircraft Maneuvering Envelopes

Boeing 777-300


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Few Definitions

Steering angle

= angle defined by the aircraft longitudinal axis and the nose gear (usually up to 70 degrees for some aircraft)


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Few Definitions

Turning Center

= the imaginary point where the aircraft pivots while turning at a given steering angle.

Turning center


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Sample Aircraft Maneuvering (B777-300)


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Operational Issues

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While steering angles as high as 60-70 degrees are technically possible in some aircraft, it is unwise to ask pilots to use such high steering angles in practice while on a taxiway

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Very high steering angles are typically associated with apron maneuvering (while aircraft is moving at very low speeds)

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Consider the pilot visibility when designing your airport infrastructure. Aircraft have limited frontal and lateral visibilities

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Consult the appropriate aircraft manuals when in doubt


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Sample Aircraft Forward Visibility


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Implications of Aircraft Maneuvering

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Apron design requirements

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Taxiway design requirements

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Taxilane design requirements

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Runway exit design requirements

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Holding bay design


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Taxiway Design Standards and Requirements

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Source: FAA AC 5300-13 (Chapter 4)

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Dictated by safety analyses

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Provide sufficient taxiway and runway-taxiway intersection width to avoid accidents (i.e., landing gears go into the shoulder or grass)

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Use simple FAA criteria to design taxiway-taxiway or taxiway-runway intersections


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Where is the Info. in FAA AC 150/5300-13?


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Why Do We Need Taxiway Fillets?

As the aircraft maneuversaround the taxiway, themain gears get fartheraway from the taxiwaycenterline (track-in distance)

Track-in distance = 0

Track-in distance > 0


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Taxiway Fillet Design Rationale Track-in distance = 0

Track-in distance > 0

Safety Distance

Distance from PC

PC

Minimum safetydistance

Distance fromouter main gear


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Taxiway Fillet Design Solution

Critical DimensionsR - Radius of CLL - Length of filletF - Inner fillet radiusW - Width of taxiway


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Taxiway Fillet Design Standards (per FAA)


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Taxiway Dimensional Standards (per FAA)


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Taxiway Design Equivalencies

According to FAA the following equivalent design procedures can be used instead of the values in the previous table

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Taxiway safety area

equals the aircraft wingspan

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Taxiway OFA

(Object Free Area) equals 1.4 times the critical aircraft wingspan + 20 ft. (6 m.)

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Taxilane OFA

(Object Free Area) equals 1.2 times the critical aircraft wingspan + 20 ft. (6 m.)


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Example: Taxiway Intersection for B777-300

Goal:

Design a suitable taxiway-taxiway intersection for a Boeing 777-300

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Look at Boeing 777-300 airport compatibility documents

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Aircraft fits design group V (< 213 ft. wingspan) - 199 ft. in wingspan

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31.22 m (102 ft. and 5 inches) of wheel base

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10.97 m (36 ft.) of wheel track (between center of main landing gear struts)


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Boeing 777-300 (per Boeing data)


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Use FAA Criteria for Taxiway Fillet Design

From Table 4-2 in the FAA AC 150/5300-13 obtain the following parameters:

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R = 150 ft. (radius of taxiway)

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L = 250 ft. (lead-in fillet)

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F = 85 ft. (fillet inner radius - centerline tracking)

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W = 75 ft. (taxiway width)


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Solution Drawing

L = 250 ft. R= 150 ft.

F= 85 ft.W = 75 ft.

Taxiway-TaxiwayDesign Geometryfor Boeing 777-300


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Reality Check (with Manufacturer)

• Some minor problems are identified

• The aircraft has a long wheel base and thus track-in distances are excessive

• According to Boeing the distance from the pavement edge to the outer wheel is 4.0 m (14 ft.)

• This is below the FAA required value of 15 ft. (4.5 m.)

• See the examples in the following pages

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Sample Solution for Boeing 777-300

Runway Taxiway

Source: Boeing 777-300 data


Sample Solution for Boeing 777-300

Runway

Taxiway

NOTE: FAArequires 4.5 m.of safety distancefrom taxiway edgeto outboard wheel


Example Boeing 777-300 Taxiway-Taxiway

NOTE: FAArequires 4.5 m.of safety distancefrom taxiway edgeto outboard wheel


Recall FAA Table 4-2 (AC 150/ 5300-13)


Holding Bays

• Large paved areas to hold more than one aircraft at a time near a runway end

• Provide the physical space for a runway departure queue

• Provide operational flexibility to ATC personnel to sequence aircraft in a departure queue

• Should be simple for pilots to use them adequately

• Some busy airports use 5-6 holding bays


Sample Holding Bay (Boeing 777-300)


Taxiway Fillet Design (Table 4-2)


Detailed Aircraft Trajectory Analysis

• Use detailed add-on packages to Autocad such as Autoturn software (from Transoft Solutions)

• Use FAA AD42 software (approximate techniques to study aircraft kinematics on the ground)


Detailed CAD Analysis Using Transoft AutoturnTM

• Autoturn simulates the vehcile trajector and checks for inconsistencies (i.e., large steering angles)

• Requires a centerline track (aircraft follows the track designed in AutoCad - say a cricular segment)

• Has new aircraft templates (version 5.0 has a template for the Airbus A380). Version 5 has a standard library of over 50 aircraft

• Ability to “user define” your own aircraft

• Conduct “jet blast” analysis and evaluate fuel service points. Try this in the CEECL lab!


Autoturn Example (Transoft Solutions)


Autoturn Procedures

In order to test a taxiway/apron maneuvering geometry through Autoturn vehicle simulation execute the following steps:

• Select an aircraft library

• Select the aircraft type to be modeled

• Set simulation parameters (steering angle limits, etc.)

• Choose a path and run the animation

• The program provides feedback on the actual track and the possible constrainst of the vehicle to complete the desired maneuver


Autoturn Example (Transoft Solutions)


Autoturn - Evaluation of Service Points


Autoturn Jet Blast Analysis


Instructions to Start Autoturn

Step 1 = Start AutoCad in the standard way

Step 2 = load acad.lsp (in Autoturn folder) by:

selecting the file acad.lsp located in the Autoturn folder. From the Tools menu (go to load Application) and select the file acad.lsp

Step 3 = At the command prompt in AutoCad , type LOADAT to start Autoturn

You are ready to use Autoturn and a new pull down menu should be available in the AutoCad environment


Example Using Autoturn

Suppose we want to evaluate the turning envelop of a Boeing 757-200 through a 150 ft. tangent segment followed by a curve segment with radius 125 ft.

Solution:

Construct in AutoCad two segments containing the path of the vehicle (one straight segment and one curved segment)


Example Using Autoturn (Construct Path)

150 ft. segment

125 ft. radius


Select Autoturn Settings

Select the aircraft to be modeled in Autoturn settings


Running a Simulation

Using the Autoturn simulation menu ran the simulation of the aircraft over selected drawing objects

Boeing 757


Run the Animation from Command Line

You can run the animation form the AutoCad command menu by typing “ra”

The animation should display the path of the vehicle as it negotiates the two segments selected


Import Envelope to AutoCad

To edit the path of the aircraft in AutoCad import the animation to the AutoCad environment by selecting Import Envelope from the Autoturn pull-down menu


Imported Trajectory (View 1)

Main Gear Paths

Wingtip EnvelopeCenterline Path


Imported Trajectory (View 2)

Main Gear Paths

Wingtip EnvelopeCenterline Path


Things to Observe

• The vehicle is capable of turning in 125 ft. as illustrated from the resulting trajectory

• The track-in distance is substantial. By the time the vehicle ends the maneuver, the outer main gear track follows the curve centerline. For a Boeing 757-200 this is equivalent to 4.2 meters (or half of the main gear track = 1.15 x 7.32 meters)

• The steeting angles are acceptable for the turn (<20 degrees)


Adding Jet Blast Envelopes

• Once the aircraft track has been imported into AutoCad, you can add service points and jet blast envelopes easily

• Suppose we would like to add jet blast envelopes to the previous drawing

• Select Import Air Symbols from the Autoturn pull down menu

• This provides several options: service points, jet blast for idle thrust, breakaway thrust and takeoff thrust


Importing Air Symbols


Jet Blast Contours Added


FAA AD42 Software to Model Aircraft Trajectories

• DOS version program

• Generates good output on vehicle steering angles, offsets and general track parameters


Types of Analyses in AD42


Sample Application

• Design a 90 degree taxiway layout with a centerline radius of 250 ft.

• Define entrance and exit stations (as shown in the diagram)

PC station

PT station

R = 250 ft.

Left offet

Right offet0 + 000 ft.

0 + 393 ft.


FAA AD42 Program Screens


FAA AD42 Program Screens


FAA AD42 Program Solution (layout)


Obtain Aircraft Data (Boeing 777-300ER)


FAA Offset Taxiway Design Procedure


Enter Aircraft Data (Boeing 777-300ER)


FAA AD42 Solution (Offsets and Steering Angle)


FAA AD42 Solution (Offsets and Steering Angle - continuation)

Documents

Geometric Design2 Aircraft