Critical Engines
05-26-2012 | 06:10 AM
#11
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From: CRJ700 F/O
I would suggest paying an instructor to teach you this..there's a difference between studying the material and getting everything all confused, in which case the instructor is going to have a lot of your misunderstandings to correct...
To stay on subject though, left engine for conventional twins. Usually training twins (Seminole, Dutchess, etc) have counter-rotating props..hence eliminates what makes a critical engine, "critical"
Why don't they just put counter rotating props on everything? Goes back to what I learned in private ground school..what makes an airplane fly? Money
To stay on subject though, left engine for conventional twins. Usually training twins (Seminole, Dutchess, etc) have counter-rotating props..hence eliminates what makes a critical engine, "critical"
Why don't they just put counter rotating props on everything? Goes back to what I learned in private ground school..what makes an airplane fly? Money
05-26-2012 | 07:34 AM
#13
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From: C172 LEFT
I think you guys are confused as to what my question was actually asking. I understand why there is a critical engine, that not every plane has a critical engine. The only question I had is ASSUMING that every propeller spun clockwise (and only clockwise) would every plane have a critical engine? If you read any multi engine hand book or even the King Multi engine ground school no where in there does it refer to heavy multi engine airplanes. I am merely trying to verify that if every propeller did in fact spin clockwise that every airplane would in fact have a critical engine.
05-26-2012 | 08:09 AM
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From: PNF
Unless the Europeans designed both engines as counterclockwise rotating, then no the right engine is not critical.
Remember the only reason we have a "critical" engine is because when you lose that engine the other engine creates the largest effect on control and performance.
Remember to read your PAST acronym.
Pfactor
Accel slipstream
Sprial slipstream
Torque
05-26-2012 | 09:21 AM
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From: Admiral
I think you guys are confused as to what my question was actually asking. I understand why there is a critical engine, that not every plane has a critical engine. The only question I had is ASSUMING that every propeller spun clockwise (and only clockwise) would every plane have a critical engine? If you read any multi engine hand book or even the King Multi engine ground school no where in there does it refer to heavy multi engine airplanes. I am merely trying to verify that if every propeller did in fact spin clockwise that every airplane would in fact have a critical engine.
In response to another comment about P-Factor being the most important factor in determining the critical engine. I must disagree. Accelerated lift can play a large factor in determining the critical engine as well.
Good luck studying for you Multi!
05-26-2012 | 10:17 AM
#16
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From: Volleyball Player
Lots of the time when I was teaching this people would often confuse "critical engine" with "reasons why an airplane rolls and yaws towards the dead engine". They are different things. Airplanes yaw and roll due to asymetrical thrust, windmilling prop (prop a/c only), loss of accelerated slipstream (prop only), and the outside wing yawing and generating more lift. No matter what engine fails, these always happen and they always cause a yaw and roll to the dead engine.
05-26-2012 | 10:20 AM
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From: CRJ700 F/O
I think you guys are confused as to what my question was actually asking. I understand why there is a critical engine, that not every plane has a critical engine. The only question I had is ASSUMING that every propeller spun clockwise (and only clockwise) would every plane have a critical engine? If you read any multi engine hand book or even the King Multi engine ground school no where in there does it refer to heavy multi engine airplanes. I am merely trying to verify that if every propeller did in fact spin clockwise that every airplane would in fact have a critical engine.
In response to another comment about P-Factor being the most important factor in determining the critical engine. I must disagree. Accelerated lift can play a large factor in determining the critical engine as well.
Good luck studying for you Multi!
05-26-2012 | 12:28 PM
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P-factor, longer moment arm on the descending blade. Correct. Another thing to remember is you lose 50% of your available horsepower, but you generally lose 80% of your performance. That running engine, if you're not good at maintaining in balance, will just take you to the scene of the accident. Long time MEI.
05-26-2012 | 04:43 PM
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From: A-320 FO
The British did have a counter clockwise rotating engine, the Rolls Royce Dart, thus making the right engine the critical engine. Either way they spin leaves you with a longer moment arm on the critical engine, and asymmetric disc loading (P-factor).
05-26-2012 | 09:38 PM
#20
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Um, well, you realize the asymetrical thrust (P-factor) across the propeller blade at high AOAs IS what CAUSES the asymetrical lift (accelerated slipstream) in back of prop right?, and a rolling moment a little greater to the left with the left engine dead than to the right with the right engine dead....
Lots of the time when I was teaching this people would often confuse "critical engine" with "reasons why an airplane rolls and yaws towards the dead engine". They are different things. Airplanes yaw and roll due to asymetrical thrust, windmilling prop (prop a/c only), loss of accelerated slipstream (prop only), and the outside wing yawing and generating more lift. No matter what engine fails, these always happen and they always cause a yaw and roll to the dead engine.
Lots of the time when I was teaching this people would often confuse "critical engine" with "reasons why an airplane rolls and yaws towards the dead engine". They are different things. Airplanes yaw and roll due to asymetrical thrust, windmilling prop (prop a/c only), loss of accelerated slipstream (prop only), and the outside wing yawing and generating more lift. No matter what engine fails, these always happen and they always cause a yaw and roll to the dead engine.
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