777 freighter first flight preparation and conduct van chaney, boeing 777 deputy chief pilot paul...
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777 Freighter
First Flight Preparation and Conduct
Van Chaney, Boeing 777 Deputy Chief PilotPaul Bolds-Moorehead, Boeing 777 Stability & Control Senior Lead Engineer
Flight Test Safety Workshop – EuropeVienna, Austria
12 November, 2009
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…… following Capt. Cashman
14 years later, much is the same
6th generation of 777 Confidence built on past success Not a new airplane Pressure to do less (time, conditions,
money) “Keep it simple”
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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777 Freighter First Flight
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777 IntroductionFamily Evolution
535,000-lb TOW74k-84k Thrust
777-2001995
777-200LR2006
766,000-lb TOW110k & 115k Thrust
777-300ER2004
775,000-lb TOW115k Thrust
777-200IGW1997
632,500-lb TOW84k-90k Thrust
777-200ER1998
648,000-lb TOW≤ 90k Thrust
777-200ER2000
656,000-lb TOW≤ 94k Thrust
777-3001998
660,000-lb TOW84k-98k Thrust
777F2009
766,000-lb TOW110k & 115k Thrust
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MTOW 766,800 lb (with revised c.g. envelope)MLW 575,000 lb (a 17% increase)
Addition of Maneuver Load Alleviation (MLA) function in Primary Flight Computers
Summary of Changes: 777-200LR to 777F
No aerodynamic changes
-Same wing
-Same fuselage
-Same empennage
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777F Airplane DescriptionFlight Envelope
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777F Airplane DescriptionGW/CG Envelope
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Maneuver Load Alleviation (MLA)
Purpose: Reduce wing bending loads due to positive maneuver conditions
Function: Symmetrically deflects some lateral control surfaces as a function of normal load factor
Benefit: Forward CG expansion without additional structure Application:
777F unique to-date.
777F Airplane DescriptionManeuver Load Alleviation
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777F Airplane DescriptionMLA Details
Design Intent:a) Handling Qualities unchanged during normal maneuversb) Handling Quality changes during elevated “g” maneuvers to be imperceptible
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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777F First Flight Preparation
Predicted Flight Characteristics document Very thorough, rigorous evaluation of many different maneuvers
and characteristics Mapped across entire flight envelope Less breadth than for a new airplane
Pilot training in engineering simulator Procedure review/modification Flight condition reasonableness/attainability Familiarization with handling Crew Resource Management development Establish or refine abort/safety criteria
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777F First Flight Preparation (cont’d)
Control law issues MLA/HOSP interaction
(HOSP = Hardened Overspeed Protection)
First flight dry run Simulator used with most test participants Treated as actual flight
Ground testing System specific component tests “Gauntlet”
Flight test tools in use at BCA Engineering CAB / Fixed Based Simulator Flight Emulation Test System (FETS) LabVIEW Airplane Display System (LADS) Airborne Data Acquisition & Monitoring System (ADAMS)
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777F First Flight Preparation (cont’d)
Developed Contingency Plans Plan A:
Full first flight profile with a landing at Boeing Field test center Plan B:
In case of telemetry failure or other mechanical problems only do low and med risk test conditions (no high risk) return landing at origination base (Paine Field
manufacturing center) Added a temporary limitation to prevent activation of MLA
function turned out to be very wise as we essentially chose the time
and place to do battle with any “discoveries”
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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777F First Flight Day
14 July, 2008 At the airplane
Final prep activities Taxi testing
Telemetry (control) room activities Anticipating reception of telemetry data
Successes Airplane flew exactly as predicted (simulator) and the same
as the parent model (777-200LR pax airplane) Failures or “Opportunities”
Telemetry failure – followed “Plan B”, e.g. aborted and returned to origination field (PAE)
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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777F First Flight – Part Two
16 July, 2008
Completed what had been planned for first flight profile
Telemetry repeater van local for this test attempt
Arrived at primary Boeing test facility (Boeing Field, Seattle)
(originally planned for completion of first flight)
Planned layup and inspections followed
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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777F Aileron Vibration
Major discovery on third flight:
Significant aileron vibration present with MLA function active
Occurs at 1.8-2.0 g with a specific aileron deflection
Could have encountered on first flight without TM had the limitation not been present
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Aileron vibration discovery flights
Flutter-type testing 2 altitudes and increasing Mach numbers
Manual controller “kicks” Elevator frequency sweeps Roller Coasters and “kicks” in turns (elevated g)
Aileron vibration occurred with trailing edge up deflections of ailerons. Ailerons had never been used previously at these speeds due to aileron
lock-out function. With additional MLA g bias applied (e.g.- PFC thinks it’s under a 1.8 G
load): column kicks, shallow bank turns exhibited vibration Without MLA g bias: 60 deg bank turns and roller coaster maneuvers
to higher g levels showed vibration
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Aileron Vibration Details
Pilot comments on Aileron Vibration: “Alarming.” “Feels like driving over a washboard road.” “Feels like something is going to come off.” “Distracting and you naturally want to unload and slow down”
Causal factor unknown. Potential contributing factors include:
1. Aileron deflection angle for vibration corresponds to approximately zero hinge moment
2. A “scoop” is created between the mass balance tower and the lower surface of the wing when the aileron is deflected
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Aileron Vibration Video
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Aileron Vibration Data
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Aileron Vibration Mapping
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777 Outboard Aileron Balance Tower
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Aileron Vibe - Potential remedies
Aerodynamic modifications External wing treatments Aerodynamic sealing Internal flow diversion
Flight control software modifications Change to basic MLA aileron travel schedule Addition of aileron “No-Dwell zone” function
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Re-test flights : MLA Aileron “No Dwell” Zone
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Lessons Learned Summary
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777F Lessons Learned
Thorough checkout of ALL systems for the test program is crucial Although telemetry is not a flight critical system, it is necessary for test success
Past success doesn’t guarantee future success
Fly-By-Wire airplane control laws present opportunities to remedy issues such as this
Team approach to problem solving is required Especially when pilot opinion and engineering data differ
The “right thing” will still prevail once thorough communication occurs
Important to capture lessons learned on specific technical “discoveries” to share between programs
Pilot distraction needs to be considered as certification issue
Contingency planning (“Plan B”) is a necessary step
Envelope expansion for new functionality (MLA limitation) is required
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Agenda
777F Airplane Description/Background Preparation Activities First Flight Day First Flight Part 2 Subsequent Events Lessons Learned Summary
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Summary
Never assume that a test program will escape problems, no matter how seemingly “minor” the effort is !
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Questions?
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