Flight TestingRobert Stengel, Aircraft Flight Dynamics

MAE 331, 2010

Copyright 2010 by Robert Stengel. All rights reserved. For educational use only.http://www.princeton.edu/~stengel/MAE331.html

http://www.princeton.edu/~stengel/FlightDynamics.html

Flight test instrumentation

Pilot opinion ratings

Flying qualities requirements

Flying qualities specifications

Pilot-induced oscillations

Flying (or Handling) Qualities

Stability and controllabilityperceived by the pilot

1919 flight tests of CurtissJN-4H Jenny at NACALangley Laboratory byWarner, Norton, and Allen

Elevator angle and stickforce for equilibrium flight

Correlation of elevator angleand airspeed with stability

Correlation of elevator angleand airspeed with windtunnel tests of pitch moment

Early Flight Testing Instrumentation

Flight recording instruments: drum/strip charts, inked needles, film,galvanometers connected to air vanes, pressure sensors, clocks

Hundreds of Measurements To Be Made

Nose Boom and Calibration Quadrants

Air data measurement far fromdisturbing effects of the aircraft

z =

pstagnation

,Tstagnation

pstatic

,Tstatic

!B

"B

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=

Stagnation pressure and temperature

Static pressure and temperature

Angle of attack

Sideslip angle

#

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Trailing Tail Cones for AccurateStatic Pressure Measurement

Air data measurement far from disturbingeffects of the aircraft

Current Small UAV Avionics

Typical components

Current Flight TestingInstrumentation

...or you could use an iPhone 4

3-axis accelerometer

3-axis angular rate

2-axis magnetometercompass

GPS positionmeasurement

1 GHz processor

512 MB RAM

32 GB flash memory

z =

!u

!v

!w

p

q

r

!horizontal

!vertical

L

"

h

#

$

%%%%%%%%%%%%%%%

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(((((((((((((((

Autonomous Control of an UnmannedAerial Vehicle via an Apple iPhone

Jillian Alfred, Clayton Flanders, & Brendan MahonPrinceton Senior Project, 2010

iPhone Installation Hobbico NexSTAR

System ComponentsPitot Tube Placement

First Flying QualitiesSpecification

First flying qualities specification: 1935, Edward Warner forDouglas DC-4 transport

Interviews with pilots and engineers

Flying QualitiesResearch at NACA

Hartley Soul and Floyd Thompson(late 1930s)

Long- and short-period motions

Time to reach specified bank angle

Period and damping of oscillations

Correlation with pilot opinion

Robert Gilruth (1941-3)

Parametric regions and boundaries

Multi-aircraft criteria

Control deflection, stick force, and

normal load factor

Roll helix angle

Lateral control power

Gilruth Roll-Rate Criterion[pb/2V]

Helix angle formed byrotating wing tips,pb/2V

Roll rate, p, rad/s

Wing semi-span, b/2, m

Velocity, V, m/s

Robert Gilruth criterion

pb/2V > 0.07 rad

NACA TR-715, 1941

Simplified Roll-Rate Response Tradeoff between high pb/2V and

high lateral stick forces prior topowered controls:

p(t) = p(0)eat

!p(t) = [Clp p(t) + Cl!A!A(t)]qSb / Ixx

= a p(t) + c!A(t)

p(t) =c

aeat!1( )"A *

p* = !Cl"A

Clp

"A *

Initial-condition response (!A = 0)

Step response [p(0) = 0]

Steady state response

NACA TR-868

IAS, mph

p*, /s

q =1

2!V 2 , dynamic pressure, N / m2

Aircraft That SimulateOther Aircraft

Closed-loop control

Variable-stability research aircraft, e.g., TIFS, AFTI F-16,NT-33A, and Princeton Variable-Response ResearchAircraft (Navion)

USAF/Calspan TIFSUSAF AFTI F-16

Princeton VRAUSAF/Calspan NT-33A

Cooper-Harper Handling QualitiesRating Scale

NASA TN-D-5153,1969

Effect of Equivalent Time Delay onCooper-Harper Rating

Short-Period Bullseye or Thumbprint

!SP

!nSP

Aerial Refueling

Difficult flying task

High potential for PIO

Alternative designs

Rigid boom (USAF)

Probe and drogue (USN)

Formation Flying Coordination and precision

Potential aerodynamic interference

US Navy Blue Angels (F/A-18)

Carrier Approach on Back Sideof the Power/Thrust Curve Precise path and airspeed control while

on the back side of the power curve

Slower speed requires higher thrust

Lightly damped phugoid mode requirescoordination of pitch and thrust control

Reference flight path generated by opticaldevice, which projects a meatball relativeto a datum line

NACA RM A57L11, 1957

Pilot-Induced Oscillations

MIL-F-8785C specifies no tendency for pilot-inducedoscillations (PIO)

Uncommanded aircraft is stable but piloting actions couplewith aircraft dynamics to produce instability

Pilot-Induced Oscillations

Category I: Linear pilot-vehicle system oscillations

Category II: Quasilinear events with nonlinear contributions

Category III: Nonlinear oscillations with transients

Hodgkinson, Neal, Smith, Geddes, Gibson et al

YF-16 Test Flight Zero High-speed taxi test; no flight intended

Pilot-induced oscillations induced by overly sensitive roll control

Tail strike

Pilot elected to go around rather than eject

Military Flying QualitiesSpecifications, MIL-F-8785C

Specifications established during WWII

US Air Force and Navy coordinated effortsbeginning in 1945

First version appeared in 1948, last in 1980

Distinctions by flight phase, mission, and aircrafttype

Replaced by Military Flying Qualities Standard, MIL-STD-1797A, with procurement-specific criteria

MIL-F-8785C Aircraft Types

I. Small, light airplanes, e.g., utility aircraftand primary trainers

II. Medium-weight, low-to-mediummaneuverability airplanes, e.g., smalltransports or tactical bombers

III. Large, heavy, low-to-mediummaneuverability airplanes, e.g., heavytransports, tankers, or bombers

IV. Highly maneuverable aircraft, e.g., fighterand attack airplanes

MIL-F-8785C Flight Phase

A. Non-terminal flight requiring rapid maneuvering precisetracking, or precise flight path control air-to-air combat ground attack

in-flight refueling (receiver) close reconnaissance terrain following close formation flying

B. Non-terminal flight requiring gradual maneuvering climb, cruise in-flight refueling (tanker) descent

C. Terminal flight takeoff (normal and catapult) approach

wave-off/go-around landing

MIL-F-8785C Levels ofPerformance

1. Flying qualities clearly adequate for the missionflight phase

2. Flying qualities adequate to accomplish themission flight phase, with some increase in pilotworkload or degradation of mission effectiveness

3. Flying qualities such that the aircraft can becontrolled safely, but pilot workload is excessiveor mission effectiveness is inadequate

Principal MIL-F-8785C Metrics

Longitudinal flyingqualities

static speed stability

phugoid stability

flight path stability

short period frequencyand its relationship tocommand accelerationsensitivity

short period damping

control-force gradients

Lateral-directional flyingqualities

natural frequency and dampingof the Dutch roll mode

time constants of the roll andspiral modes

rolling response to commandsand Dutch roll oscillation

sideslip excursions

maximum stick and pedal forces

turn coordination

MIL-F-8785C Superseded byMIL-STD-1797

Handbook for guidance rather than a requirement

Body of report is a form, with numbers to be filled in foreach new aircraft, e.g.,

Useful reference data contained in Appendix A (~700 pages)

UAV Handling Qualities

UAV Handling Qualities.....You Must Be Joking, WarrenWilliams, 2003

UAV missions are diverse and complex

All UAVs must have sophisticated closed-loop flight controlsystems

Cockpit is on the ground; significant time delays

Launch and recovery different from takeoff and landing

Suggestion: Follow the form of MIL-F-8785C, FAR Part 23,etc., but adapt to differences between manned andunmanned systems

Flight Testing for Certificationin Other Agencies

Federal Aviation AdministrationAirworthiness Standards

Part 23: GA

Part 25: Transports

UK Civil Aviation Authority

European Aviation Safety Agency

Transport Canada

Even the Best SpecsCannot Prevent Pilot Error

On September 24, 1994, a TAROM Airbus A310, Flight 381, from Bucharest on approach to Paris Orly went into a sudden and

uncommanded nose-up position and stalled. The crew attempted to countermand the plane's flight control system but were unable to

get the nose down while remaining on course. Witnesses saw the plane climb to a tail stand, then bank sharply left, then right, then

fall into a steep dive. Only when the dive produced additional speed was the crew able to recover steady flight.

An investigation found that an overshoot of flap placard speed during approach, incorrectly commanded by the captain,

caused a mode transition to flight level change. The auto-throttles increased power and trim went full nose-up as a result. The

crew attempt at commanding the nose-down elevator could not counteract effect of stabilizer nose-up trim, and the resulting dive

brought the plane from a height of 4100 feet at the time of the stall to 800 feet when the crew was able to recover command.

The plane landed safely after a second approach. There were 186 people aboard. [Wikipedia]

TAROM Flight 381 (A310 Muntenia)http://www.youtube.com/watch?v=VqmrRFeYzBI

TAROM Flight 371 (A310 Muntenia)http://www.youtube.com/watch?v=htzv2KebEkI&NR=1&feature=fvwp

TAROM Flight 371 was an Airbus A310 that crashed near Balote!ti in Romania on 31 March 1995. It was a flight from Bucharest's

main Otopeni airport to Brussels. The flight crashed shortly after it took off. Two main reasons are indicated: first the throttle of

the starboard engine jammed, remaining in takeoff thrust, while the other engine reduced slowly to idle, creating an

asymmetrical thrust condition that ultimately caused the aircraft to roll over and crash. Second, the crew failed to respond to the

thrust asymmetry.

None of the 10 crew and 50 passengers survived. [Wikipedia]

Next Time:Advanced Problems ofLongitudinal Dynamics

SupplementaryMaterial

Princeton University!sFlight Research Laboratory (1943-1983)

Robert Stengel, Aircraft Flight Dynamics, MAE 331, 2010

Forrestal Campus

3,000-ft dedicated runway

Copyright 2010 by Robert Stengel. All rights reserved. For educational use only.http://www.princeton.edu/~stengel/MAE331.html

http://www.princeton.edu/~stengel/FlightDynamics.html

Helicopters and Flying Saucers

Piasecki HUP-1 helicopter

Hiller H-23 helicopter

Princeton Air Scooter

Hiller VZ-1 Flying Platform

Princeton 20-ft Ground Effect Machine

Short-Takeoff-and-Landing, InflatablePlane, and the Princeton Sailwing

Pilatus Porter

Goodyear InflatoPlane

Princeton Sailwing

Variable-Response Research Aircraft(Modified North American Navion A)

Avionics Research Aircraft(Modified Ryan Navion A)

Navion in the NASA Langley Research Center30! x 60! Wind Tunnel

Lockheed LASA-60 Utility Aircraft Schweizer 2-32 Sailplane (Cibola)

Steve Sliwa, !77, landing on Forrestal Campus runway.currently CEO, In Situ, Inc.