Page 7 - April22T

This made an easy crosscheck for instructors: If there is any indicated airspeed at all, you’re too fast to simulate an engine failure.
Note that VMCA (red radial) speed is a worst-case scenario for engine failure in the air (the subscript “A”). There is also a VMCG (for “ground”) that takes into account nosewheel steering and the nose tire’s resistance to turning. However, in the absence of a published VMCG in most piston twins, VMCA is usually the only guidance we have.
4. Minimum altitude for simulated engine failure after takeoff: 500 AGL/above field elevation. The rate of departure from desired flight path on all three axes (pitch, roll and yaw) is very great in a twin at low altitude. The operating engine is generating more thrust, so the effects of asymmetric thrust are greater. Even in turbocharged airplanes, there is less thrust at higher altitudes because of reduced propeller efficiency. What you see practicing engine failures at the FAA-suggested 5,000 feet AGL minimum altitude is much less dynamic than what you’d experience in a real-world engine failure on takeoff because at altitude the “good” engine is putting out much less power.
Meanwhile, there is more drag on the “dead” side’s windmilling propeller in thicker, low-altitude air. If the gear is down the loss of airspeed is so great that you don’t even have time to retract the gear before it becomes critical – hence push the nose down, chop both throttles to idle to remove thrust asymmetry, and hold heading with rudder while you land straight ahead. If the gear is up you may be able to push and hold to remain at VYSE (“blue line”) while you address the engine failure and, if appropriate, feather the correct propeller. But you may climb very little or even lose some altitude while you do so.
That’s why I do not initiate a simulated engine failure within 500 feet of the ground – to give you room for a possible loss of altitude during your response.
5. Single-engine go around minimum altitude: 500 AGL/above field elevation. Experience shows that it takes roughly 400 feet to turn a single-engine final approach descent into a single-engine go-around climb in many piston twins. As you apply full power on the operating engine and adjust controls for the change in asymmetric thrust, re-trim the airplane and retract the landing gear and flaps. The airplane will continue to descend before it slowly begins to climb at the very low rate of a piston twin on one engine. This is an exception to the rule “positive rate, gear up.” Most pistons and even some turboprops will rarely be able to climb at all on one engine with the gear extended. You need to retract the gear before seeing a positive rate of climb because you’ll never see it if you don’t retract the gear.
This brings up another decision point: When landing on one engine (in a real-world engine failure), you are committed to land when either (1) you select full flaps (because of the substantially added drag and long retraction time) or (2) you descend below 500 AGL. If either (1) or (2) occurs, you may have to side-step and land on a taxiway or in the grass if something blocks the runway. But you have a very low chance of success if you attempt a single-engine go around.
Personally, I use 800 AGL as a minimum single- engine go around altitude to provide a little margin. Unless the go around is done specifically for training (i.e., we’re simulating a single-engine landing and someone taxis onto the runway ahead of us, or we’ll land long or short, or we aren’t holding centerline without sideways drift), I’ll follow a prebriefed procedure with the student where we restore climb power to both engines and control the airplane into a two-engine climb.
6. No landing with a propeller feathered except in an actual emergency. There was a time when many multi-engine instructors would have the student feather a prop and then land. It’s a great confidence builder and many members enjoyed the experience. But there are no margins for error. And restarting a feathered propeller on the ground is difficult and stressful on the engine (that’s why the props have anti-feather lock pins for normal shutdown). So most multi-engine instructors limit themselves against actual one-engine landings – a personal minimum I fully support.
I do, however, have the student land with an engine in zero thrust. This allows the pilot to experience the “rudder reversal” when reducing the operating engine to idle for landing. The rudder trim, set to counter the effects of asymmetric thrust, now yaws the airplane in the opposite direction. It also demonstrates the “float” and substantially longer landing distance on one engine, so much so I’ve always personally required at least 5,000 feet of pavement for a zero-thrust landing. This maneuver requires good pre-briefing and coordination between the instructor and student because to be effective the
April 2022 / TWIN & TURBINE • 5