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Filing Flight Plan
Tiger, thank you for so vividly illustrating the critical problem with the way that we (GA) teach the concept of critical engine.
To a pilot in flight, a failure of a critical engine is not really any more critical than a failure of any other engine and the actions taken to maintain control and assure a safe condition of flight are the same in any case.
Thus my position is that critical engine is a concept best understood and taught as a certification matter, not as an operational concern for pilots, and certainly not overexplained with dubious theories that tend to confuse more than enlighten.
Lastly, let's add one more memorable engine failure to my personal anecdote; that one having occurred in a single-engine airplane, resulting in an off-airport landing. THAT, to me at least, was all the proof needed that when we only have one engine operating, a failure of that one engine is, indeed, critical. {ref. post #27}
-bob
Misinformation leads to misunderstanding. The ways that accelerated and spiraling slipstream are being presented are oversimplified and/or inaccurate. On a twin with wing-mounted engines and a fuselage-mounted vertical stabilizer, the propeller slipstream doesn't exert significant influence on the vertical stabilizer in flight. Local flow behavior over the wing sections behind the propeller and near the nacelle can be very complex and the downgoing/upgoing blade theory is too simplistic to predict the actual lift distribution on a real airplane operating in a given flight condition. For example, none of the PAST explanations I've read mention the variations in section AOA that are induced by the propeller slipstream, and that those AOA variations tend to mitigate lift asymmetry. A basic, accurate understanding of aerodynamics is not moot, Tiger, but how does the propagation of misinformation help us to be safer, better pilots?
These remarks show how the concept of critical engine is misunderstood. Those who designed our multi-engine airplane did so under the assumption that any powerplant failure would occur in a worst-case-scenario set of conditions, which include the failure of the engine that would most adversely affect the performance OR handling qualities of the airplane (definition of critical engine). Thus the vertical stabilizer and rudder were designed and sized so as to provide sufficient control authority in the worst-case set of conditions envisioned by the certification standards. During the flight test program, a minimum control speed, Vmc, is established for the assumed worst-case condition (critical engine failed). From that point forward--and this, my friends, is the BIG PICTURE as I see it--the matter of which engine is the critical engine is merely academic: so long as a pilot maintains an indicated airspeed at or above Vmc, sufficient control authority exists to safely maneuver the aircraft regardless of which engine is failed. The failure of the critical engine is no more dangerous, from the standpoint of controllability, than the failure of any other engine. Empirical evidence supports this assertion: having experienced four in-flight engine malfunctions that resulted in failures or precautionary shutdowns and one propeller system failure, along with countless simulated engine failures in training, I have never found the failure of one engine to be significantly, or even noticeably, more difficult to manage than another (on twin-engine airplanes, that is. Three and four-engine airplanes are, of course, a whole nuther story).
To a pilot in flight, a failure of a critical engine is not really any more critical than a failure of any other engine and the actions taken to maintain control and assure a safe condition of flight are the same in any case.
Thus my position is that critical engine is a concept best understood and taught as a certification matter, not as an operational concern for pilots, and certainly not overexplained with dubious theories that tend to confuse more than enlighten.
Lastly, let's add one more memorable engine failure to my personal anecdote; that one having occurred in a single-engine airplane, resulting in an off-airport landing. THAT, to me at least, was all the proof needed that when we only have one engine operating, a failure of that one engine is, indeed, critical. {ref. post #27}
-bob
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