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#16
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Piston engines 101-a : When a pilot says his aircraft manifold pressure goes to "zero" on a gauge that only goes down to 10, he is really saying that his MP went to what amounts to .33 bar's. Well within the probability of compression braking caused by intake obstruction. Zero is a euphemism for "bottom of the gauge ".
And as for any inference that a piston engine can not " run" at less than 12"MP, once again this misses the point. If an aircraft is "flying" and the prop is spinning, engine is "running" but not producing power . Thereby the MP can easily indicate less than 12" of merc, provided that the induction side is somehow constrained. And / or it wasn't powerful enough. Last edited by Roger : 01-10-12 at 10:44 PM. |
#17
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Clearly you were there, and I wasn't, weren't you?
This particular smart-ass fresh-from-the-jet expert didn't see zero and he didn't see bottom of the gauge. He didn't see anything but what his imagination told him was there, and my assessment of his accounting and the event, my subsequent investigation, and examination and operation of the aircraft proved it to be the case, which is why I presented it as I did. I noticed, incidentally, that you weren't there. Quote:
Icing was not a consideration. Induction obstruction was not an issue. Engine failure was not an issue. He had a partial power loss, and in fact landed under power. You seem very hung up on the issue of manifold pressure, but the issue at the time, particularly for the mechanics, was the insistence that a turbo failure would cause manifold pressure to drop to zero, when in fact that is entirely inaccurate. A complete power loss with a closed throttle plate does not equate to zero, or even bottom of the gauge. This is particularly true at the speeds the airplane was operating, and the resultant windmilling force on the propeller and RPM. High speed was not an issue, nor was high RPM, and manifold pressure in a windmilling piston engine is a function of windmilling RPM and throttle position. |
#18
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"Condescending"? Now that's funny
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