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Semaphore Sam
5th Mar 2002, 23:45
I've heard that the concept of the 'Critical Engine' is the same for props and turbines. Is this true?

Diesel8
6th Mar 2002, 10:24
Any engine that quits in an untimely manner is pretty critical, be a piston or a turbine.. .. .Critical engine,of course, refers to which engine most adversely affects the handling characteristics of the aeromobile. It depends on the direction of rotation of a propeller, but all prop driven airplanes has one.. .. .Like my old friend says: Pistons are for cars, props for boats and jets for kids!!

IMMELMAN
6th Mar 2002, 13:02
Sam - On props - if contra-rotating, then no critical engine. With turbine, apart from possible small torque effect, term does not really apply. Sometimes, if neither effect is a consideration, an engine may be considered 'critical' if, sy, it happens to drive an important system that cannot be driven by another engine. Probably quite rare on modern arcraft - but that is why at one stage, people used to get confused about the term 'critical', which now generally applies to the engine which, if it fails, will cause maximum yaw. So, on a piston or turbo-prop, whichever DOWNGOING prop blade is further from the longitudinal axis of the aircraft, compared to its counterpart on the other side will be 'critical'. If you are in a single - then that is the critical engine but not really for the same reason, although I suppose it is since it does affect the handling carachteristics of the aircraft - if it fails, you go in a downward direction <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

Mago
6th Mar 2002, 13:52
I do not know for you, but for me, in a twin engine aircraft, the critical engine is the one that stay operating when the other fails!. .If you donīt take care of it the situation will become CRITICAL!. .. .My apologize to the individual who discover the "P" factor <img border="0" title="" alt="[Roll Eyes]" src="rolleyes.gif" />

Justforkix
6th Mar 2002, 14:14
In a max crosswind takeoff I would call the upwind engine the critical engine.

tired
7th Mar 2002, 00:36
Immelman has the answer - whichever engine causes the greatest yaw when it fails.. .. .Piston/turbo-prop - as described by Immelman.. .. .4-engine jet - either outboard engine.. .. .Twin jet - as someone else stated, I don't think it would really apply, other than for very small torque effect from the fans.