1. 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 –

2. 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

3. 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

4. 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

5. 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.

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

7. 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

8. Is the runway long enough?

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

10. 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?

11. 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

12. 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

13. 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

14. 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

15. 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.

16. 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.

17. 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

18. 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.

19. 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 ft of drift is acceptable and safe
Refusal speed is well above takeoff speed
Plenty of runway length to stop

20. 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)

21. Video: Buildup Vmcg+5

22. Video: Endpoint

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

24. Putting it in Perspective

25. 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

26. 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

27. Questions?

29. 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.