Critical Engines
05-25-2012, 08:36 PM
#4
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I have read the material. I have been studying twin engine aerodynamics however this is a legitimate question. Not every airplane has a critical engine; understood. I am not asking a hypothetical question either. Take a Dash 8 for instance would a Dash 8 have a critical engine if both engines operated clockwise? A Dash 8 and a PA-44's aerodynamics are highly different (i.e high wing vs low wing; perhaps higher torque; etc). That's what I am asking. Do all twin engine aircraft (assuming both propellers operated clockwise) have a critical engine? I understand why there is a critical engine and how we come to the conclusion I am just trying to fully understand this principle.
05-25-2012, 09:12 PM
#6
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If both engines are turning the same direction then yes there is a critical engine. It doesnt matter if there is a low wing or high wing. The PA-44 does not have a critical engine because it has counter rotating props.
05-26-2012, 05:26 AM
#7
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The main principle you should be looking into is P-factor. If you lose the left engine you have to pitch up to substitute for the loss of lift to maintain altitude. When pitching up you are increasing the the angle of attack of the descending blade, which creates more of a "bite". The arm is longer from the longitudinal axis to the descending blade on the right engine and shorter on the descending blade of the left engine. This increase in P-factor and longer arm on the right side is what makes the left engine critical whenever both propellers spin clockwise. There are three other factors that contribute to the left engine being the most critical to lose, but P-Factor is the main one to conecentrate on. Hope this Helps!
05-26-2012, 05:39 AM
#8
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Keep it simple brother.
Unless you have counter-rotating propellers you have a critical engine which will always be the right engine. At least I've never heard of both props running counter-clockwise. If that were the case though the left would be critical.
Unless you have counter-rotating propellers you have a critical engine which will always be the right engine. At least I've never heard of both props running counter-clockwise. If that were the case though the left would be critical.
05-26-2012, 05:54 AM
#9
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Originally Posted by captain152
Keep it simple brother.
Unless you have counter-rotating propellers you have a critical engine which will always be the right engine. At least I've never heard of both props running counter-clockwise. If that were the case though the left would be critical.
Unless you have counter-rotating propellers you have a critical engine which will always be the right engine. At least I've never heard of both props running counter-clockwise. If that were the case though the left would be critical.
You have it mixed up. The "critical engine means the engine whose failure would most adversely affect the performance or handling qualities of an aircraft". Clockwise= Left engine critical.
05-26-2012, 06:05 AM
#10
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Correct me if I'm wrong but on European built airplanes isn't the critical engine usually the right engine? ASpilot2be I know the PA-44 does not have a critical engine however my question was assuming that all props rotated clockwise only.
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