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Engine-Out Considerations

Gulfstream G450 Abnormals

The G450 engine, the Tay, was named after a river in Scotland because it always runs. Engine failures? We don't expect it in the airplane, we practice it in the simulator, and never think about it otherwise. Having flown a fair amount of junk in the Air Force, we talked about engine failures a lot. Many of the lessons we learned the hard way still apply today.


 

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By the time I got to the KC-135, 50 had been lost. Most engine failures are survivable.

Performance

Performance - Takeoff Rejected

Over the years, Gulfstreams have gotten more power and better brakes, giving pilots a greater margin of safety when a takeoff is rejected. On shorter runways, however, lessons from the Boeing 747 fleet hold true:

  1. If the airplane will fly, you are better off getting airborne and returning to land at VREF with full flaps, the engines at idle, and all the runway in front of you; than you are rejecting at V1 with partial flaps, the engines at full power, and most of the runway behind you.
  2. If you are going to reject the takeoff, leave all smoothness behind: slam the throttles back, jerk the reversers into full, and mash down on the brakes as hard as you can. And do all that at once.
  3. Don't give up on the stop until you are stopped. Simulator tests have shown that pilots tend to relax their leg muscles at the last moment. Some suspect this is because the acceleration sense of one's inner ear semicircular canals reach an equilibrium toward the end of a drastic deceleration and fool the brain into thinking the aircraft has stopped. Whatever the reason, don't let up on the brakes until the nose bobs up and down a few times.

More on: Rejected Takeoff

Performance - Takeoff Continued

In the Air Force we called these "Engine Failure - Takeoff Continued," but in the Gulfstream it is simply an Engine Fire/Failure on Takeoff.

The first step is to keep the airplane on the runway.

See Aircraft Control - Yaw below.

The second step is to get the airplane climbing.

See Aircraft Control - Pitch below.

Finally, you need to keep the airplane in controlled flight once airborne.

See Aircraft Control - Roll below.

Checklists. In the GV/G450/G550 World there are three basic engine fire / failure checklists:

  1. Engine Failure Below V1 (EB-3) — when you reject the takeoff.
  2. Engine Failure Above V1 (EB-3) — when you continue the takeoff, when the failure occurs en route, just about any other condition that doesn't involve a fire. There are a few others in the EB ("Engine Broke") section, such as dual engine flameout and opposite hydraulics failed.
  3. Engine Fire in Flight (EC-3) — when you continue the takeoff and an engine is on fire, including while en route.

More on: Engine Fire/Failure Takeoff Continued.

Performance - High Altitude

When a two-engine aircraft at cruise altitude loses an engine, the pilot must execute a drift down to maximize forward distance while descending to a suitable one-engine cruise altitude. In most Gulfstreams the driftdown speed is very close to cruise speed, so the pilot's initial response is critical. Each aircraft has its own particular intricacies so practice in the simulator is critical. In the GV, for example, you normally have about a minute to react and your initial descent rate will be only 300 fpm. In the G450, however, you need to start down immediately and your initial descent rate will be around 600 fpm.

More on this under: G450 Engine Fail / Drift Down.

Aircraft Control - Yaw

Over the years there have been more than a few examples of pilots killing all on board in a mad dash to apply as much rudder as possible as soon as possible, neglecting to ensure the correct rudder is pressed. In 1985 all on board a KC-135A tanker were killed when a highly seasoned instructor pilot got it wrong. The impact site was no bigger than the wing span of the aircraft, it drove nose first straight into the ground. The airplane had more than enough power on three engines, the weather was CAVU, there were no time pressures, and the crew was well rested. The Air Force reminded us all to be careful out there. In Hawaii, that same year, we had a pilot almost invert an airplane 200' above a pineapple field.

We came up with our own solution: do nothing. We started teaching (and practicing) the following:

  • At 200' AGL the instructor asks the student to place his feet on the floor and forbids the use of rudder until instructed.
  • The instructor selects an outboard engine to fail, say #4, and braces the leg on the opposite side (in our example, the left leg) in case the student ignores the no rudder warning, and pulls that throttle to idle.
  • As the thrust rapidly decays the operating engines lift that side's wing up and causes a bit of yaw. The instructor says "Level the wings with ailerons." After a few seconds: "we are still flying, still climbing, albeit sideways a little. Now look at the yoke, your left hand is down. Slowly step on the low hand until the yoke is level."

I've used the method ever since and have lost a few engines in that time. The method works.

Years later I was in a simulator course where the airplane's critical engine was the left and the instructors always failed the left engine on takeoff because that's what the check airman was going to do. I used my method and the instructor would say "not bad." My flying partner always got the rudder in so fast you never saw the nose track. "Perfect," the instructor would say as the student beamed at showing up the old man (me). "How can you be sure you got the correct rudder?" I asked. She said she felt the yaw. I talked the instructor into failing the right engine instead of the left without warning her. She mashed down on the right rudder, as always, and five seconds later we were dead, in simulator hell. She was furious and has never talked to me since. She is now an airline pilot and I hope she never loses an engine.

Aircraft Control - Pitch

Aircraft with limited engine out power can be extraordinarily pitch sensitive on takeoff where errors in the rotation rate of just a degree per second or rotation angle of just a degree can mean the difference between climbing and digging an hole in the ground. Even a G450 with lots of power in reserve can find itself on the wrong side of the power curve.

Rotation Rate.

I once witnessed a pilot "swap ends" on takeoff rotation in the Boeing 707, going from 0° pitch to 8-1/2° instantaneously, stalling the wing and turning our 300,000 pound airplane into a ground vehicle with a disappearing road surface. I shoved the nose back down and slowly rotated and we became an aerospace vehicle once more. The flight manual had this caution: ". . . the pilot will bring the control column back so that takeoff attitude will be accomplished in 3 to 4 seconds." Rate? That comes to between 2 and 3 degrees per second.

The Boeing 747 manual only says "smooth rotation" but in the Air Force we used "between 4 and 5 degrees per second."

The G450 Operating Manual [12-01-10.1.] details a different procedure: "After reaching the target rotation speed, a rapid and aggressive column pull shall be applied." Nothing smooth about it.

My personal technique: you can't be harmed by smoothness here. The 4 to 5 degrees per second in a G450 means your 17° rotation will take between 3 and 4 seconds. In all that time you are gaining speed and adjusting rudder for a failed engine if need be.

Rotation Angle.

In the KC-135 the manual requires a target pitch of 8.5° for normal takeoff flaps and cautions that undershooting and overshooting by 1° can be critical. In our Boeing 747-200 the rotation angle was computed for every takeoff. In the G450, the flight director does that for you.

The G450 takeoff trim setting and the V2 to V2 + 10 target speed are based on losing an engine. With both engines running the aircraft will need lots of nose down trim and the speed is, of course, less critical.

Aircraft Control - Roll / Dutch Roll

Losing an engine on takeoff with a crosswind can lead to conditions conducive to a Dutch roll immediately following rotation. Making deliberate rudder and aileron inputs and avoiding quick, jerky reversals will help avoid any chance of Dutch rolls on aircraft with positive static stability.

Dutch roll was a big problem in the older KC-135 and the Boeing 707's without yaw dampers.

More on how to cope: Dutch Roll

Approach

An engine-out approach in the G450 is flown using all-engine procedures and configuration, with minor differences involving the aux pump and PTU system when a left engine is failed and restrictions against autothrottle and autopilot usage.

When the GV first came out the procedure was to use 20° flaps until landing was assured and then go to 39° flaps. The problem? The engines would not be commanded into a high idle setting with 20° flaps and in the event of a missed approach the engines would catch up all at once and present the pilot with a huge control problem. Other issues included a high deck angle and EVS system aim. The aircraft had more than enough power to fly the approach with full flaps and even if the flaps jammed there during a missed approach, the aircraft had enough power to cope. Now the GIV, GV, and the G450/G550 series all recommend using full flaps for an engine out approach.

Missed Approach

If executing an engine out missed approach, the auto throttles should already have been disconnected. The autopilot must also be disconnected prior to executing the missed approach.

The procedure is the same as with two engines but control of the rudder can be a challenge. Try to add rudder at the same rate as power on the good engine is applied. When in doubt, apply rudder and allow things to stabilize a bit before adjusting. Generally speaking, if you are going to use full power you will need all the rudder.

If you leave the flight level change button alone and keep the flaps at 20°, the speed command will remain at VREF + 20, where you want it. If you end up with FLC pressed and the speed command goes to 200, as it probably will, you can find VREF again on the display controller, just add 20 knots.

References

Gulfstream G450 Aircraft Operating Manual, Revision 35, April 30, 2013.

Gulfstream G450 Aircraft Operating Manual (Historical), Revision 24, September 18, 2009.

Gulfstream G450 Airplane Flight Manual, Revision 36, December 5, 2013

Revision: 20120814
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