From The Lycoming "Flyer" page 49 under the sub heading of National Transportation Safety Board Warning on Simulated Engine-Out Maneuvers
The fatal crash of a light twin in which a flight instructor and an applicant for a multiengine rating were killed prompted the NTSB to issue an urgent warning to all pilots simulating an engine-out condition on multiengine airplanes.
The Board’s investigation revealed that some flight instructors do use the fuel selector or the mixture control to shut down an engine to test a multiengine applicant. Although this is a recommended procedure, the urgent warning was aimed at flight instructors who were using this procedure at altitudes too low for continued safe flight.
The NTSB observed that use of such procedures at traffic pattern altitudes may not permit instructors enough time to overcome possible errors on the part of the applicant.
The recommendation by the NTSB means that all simulated engine-out operation at the lower altitudes should be accomplished by retarding the throttle, and this should be done slowly and carefully to avoid engine damage or failure.
Many flight instructors down through the years used the technique of abruptly cutting an engine with a multiengine candidate to test his emotional reaction and judgment with this extreme technique. Big radial piston engines with short, stubby crankshafts could tolerate the abrupt technique. However,
flat-opposed piston engines with their long crankshafts and attached counterweights could not as readily take the abuse of suddenly snapping a throttle shut, particularly at takeoff or climb power. Use of the latter technique would tend to detune crankshaft counterweights and could possibly result in a nasty engine failure.
Since it was common technique by flight instructors to terminate power abruptly to simulate an engine power loss, we had to protect the engine. As a result, we published in our Engine Operator’s Manual and in Service Bulletin No. 245, the recommendation that if the power was abruptly terminated, it must be accomplished with the mixture control. Of course, this was intended for the higher altitudes where a complete engine shut-down could be conducted safely. The student was to identify the dead engine by retarding that throttle to about 12" MP to simulate zero thrust, or similar to having the prop feathered. At that point, the instructor could immediately return the mixture to an engine-operating condition, and power would be available
if needed.
In our publications, we then explained the reason for using the mixture to abruptly terminate power. By putting the mixture control in idle cutoff position with the throttle in a normal open or operating position, the pilot merely cut off the fuel, but allowed the air to continue to fill the cylinders with resulting normal compression forces that are sufficient to cushion the deceleration of the engine and prevent the detuning of the crankshaft counterweights.
However, any practice of simulated engine-out condition at low altitudes should be best accomplished by a slow retardation of the throttle in accordance with the NTSB recommendation. This careful technique will protect the engine, and at the same time, provide for instant power if it is needed.
The above information from the engine manufacturer is in marked variance to what many in Pprune have written on this thread. Time for those concerned to step back and reflect on their folly?
Last edited by Tee Emm; 26th May 2012 at 13:28.