LCDR Adam Scott – VX-20 Mr. Brandon Munday – 5.1.6.3 High-Fidelity Simulation of a Heavy Jetliner: Flight Data Collection at the Edge of the Envelope LCDR Adam Scott – VX-20 Mr. Brandon Munday – 5.1.6.3

ELDES Background & Test Goals ELDES: “E-6B Level-D Equivalent Simulator” Build a simulator that functionally meets FAA “Level D” specifications Not just FAA specs Navy-specific requirements BuNo specific – matches one particular airplane replaces on-airplane training with ground-based simulator training Collect the flight test data required to build this simulator

Specific Examples from ELDES Test areas where risk, cost and schedule tradeoffs were required: Vmcg (Minimum Control Speed, Ground) Critical Engine Failure on Takeoff Heavy-weight Rejected Takeoff (>320klb) Minimum Rotate / Minimum Liftoff Speed Stall testing, with 3 and 4 engines operating

Vmcg Test Considerations “Minimum Control Speed, Ground” Multi-engine airplane Many possible test methods and setups Large moment arm of outboard engine thrust Inherently a risky test Complexity increases with decreasing runway size

Vmcg Defined Vmcg is the minimum airspeed during the takeoff ground run at which an upwind outboard engine can fail and, with no change to the thrust of the remaining engines, the aircraft can be kept in a straight path on the runway. Control can be maintained with full rudder, not more than 75 percent of roll control, and nosewheel steering centered. “Straight path on the runway” is defined as deviating up to 30 feet from the initial intended path.

The Takeoff Heavy Jet Takeoff Numbers Vtakeoff Vrefusal Speed Vrotate Vcef Vmcg Distance

The E-6B Takeoff E-6 Takeoff Numbers Vtakeoff Vrefusal Speed Vrotate For an “optimum outboard thrust takeoff”, outboard thrust (hence the potential asymmetry) is reduced so that Vmcg becomes Vcef, and V1 is selected as that speed So: We KNOW Vmcg – we have reduced the possible thrust asymmetry Vtakeoff Vrefusal Speed Vrotate V1 = Vmcg = Vcef Distance

Is the runway long enough?

Engine Failure on Takeoff Watch the #1 (left outboard) engine Then watch the rudder

The questions Can we handle emergencies? Can we do the test locally at Pax River? Is the runway long enough? Is the runway wide enough? Can we safely kill an engine at takeoff thrust? Will we get the data we need? How much buildup do we need?

Can We Handle Emergencies? Second engine fails Only two engines to climb This drives the maximum takeoff weight to around 240klb Most critical is second engine on same side Excessive thrust asymmetry V2 (climbout speed) is below Vmcair for two engines out on same side Vmcair defined as steady heading and 5 deg bank, with full rudder, 75% roll control Can accept drift and bank angle to retain control while accelerating Existing sim used for Vmcair and CRM training Conclusion: At 240klb we can climb and get above Vmcair

Is the Runway Long Enough? If we need to abort the takeoff, we need to be able to stop in the runway remaining. Sample Numbers: For 240klb (the two-engine climb weight) Critical Field Length = 4,400 ft Available Field Length = 11,000 ft Refusal speed is at least 60 kt above Vmcg Conclusion: Plenty of runway

Is the Runway Wide Enough? If close to actual Vmcg (the goal!) we WILL drift up to 30 ft laterally. This is a BIG airplane with 150-foot wingspan and low-slung engines. The runway is 200 ft wide. Not much margin for error. We’re not trying to FIND Vmcg Start on the “conservative” side of the runway Allows an extra 30 ft of drift Provides clear Knock-It-Off (centerline) Nosewheel steering can help with heading control We can abort the takeoff safely Power reduction eliminates thrust asymmetry Conclusion: with risk mitigation, it’s wide enough

Engine Cutoff at High Power Engines are NOT designed to be shut down from high power – especially twin-spool, high-bypass engines. Special procedures are required to cool the engine core to prevent damage. Cannot immediately restart a fuel-chopped engine without risking damage. The intentionally cut engine may not be available in an emergency. Conclusion: with appropriate precautions, it’s safe

Buildup: How Much? Buildup is a good thing. Usually. In a high-risk test, extra buildup also means “increased risk” – the exposure goes up. Too much buildup is costly. Multiple takeoff and landing events cannot be conducted sequentially Brake heating limits dictate how many stops can be conducted in a given time period.

Buildup: How Granular? First engine cutoff target: V1 (Vmcg) + 5 kt Fairly conservative: About 2-3 sec for engine to spool down Increasing airspeed (3 other good engines at high power) Airplane will be well above Vmcg throughout the maneuver. It may be impossible to start faster. If too close to Vrotate, it does no good to conduct the test where the airplane is only on the runway a couple seconds. Not enough time to evaluate the handling qualities.

Vmcg: The Actual Test Selected a gross weight that: Allows two-engine climb Keeps V1 and Vmcg locked together Ensures adequate field length for aborts Buildup point: engine to idle at Vmcg + 0 Buildup point: cutoff at Vmcg + 5 End point: engine cutoff at Vmcg + 0

We elected to continue the takeoff. So Now What? The test point is over We’re still accelerating down the runway… but with just three engines! Do we continue the takeoff, or do we stop? We elected to continue the takeoff.

Vmcg: After the Test Point Following engine cutoff, continue the takeoff The E-6 community is “go-oriented” High-speed aborts are statistically more risky Test weight allows two-engine climb But… In extremis, continuing the takeoff is not required At least 50-60 ft of drift is acceptable and safe Refusal speed is well above takeoff speed Plenty of runway length to stop

Vmcg Test Results Testing was conducted on 17 Aug 2005. First buildup (Vmcg+0 IDLE): minor deviation, easily controllable Second buildup (Vmcg+5 CUTOFF): 15 ft deviation but still easily controllable End point (Vmcg+0 CUTOFF): 80 ft deviation (KIO + 50 ft)

Video: Buildup Vmcg+5

Video: Endpoint

Time (sec) NOT DISTANCE! Data for Vmcg Cutoff Time (sec) NOT DISTANCE!

Putting it in Perspective

Results: Lessons Learned NWS makes a big difference in Vmcg The Vmcg definition says “nose wheel steering centered” and “30 feet” 80’ deviation - were we below Vmcg? NATOPS calculates V1 & Vmcg using nose wheel steering to maintain centerline, but defines Vmcg as no NWS… GOTCHA 30 feet of initial right offset kept the grass out of our tires. Risk management is a good thing. With precautions, the E-6 can fuel-chop an engine from high power without damage

Results: Lessons Learned Our test planning paid off The test was successful at collecting the desired data So… Buildup is a Good Thing The extra buildup point we added was good practice But… Buildup may not tell the entire story

Questions?

Some E-6B Takeoff Definitions Vcef: Critical Engine Failure Speed is the speed at which an engine can fail, and the same distance is required to either continue the takeoff or stop. V1: Decision speed is the higher of Vcef and Vmcg, but not greater than rotation speed. (note that this includes Vmcg as part of the definition) Vrefusal: Refusal Speed is the maximum speed that the aircraft can attain under normal (four-engine) acceleration and then stop on the available runway. CFL: Critical Field Length is the total length of runway required to accelerate on four engines to V1, experience an engine failure, then continue the takeoff or stop. For a safe takeoff, CFL must never exceed the runway available.