KRyan
Pre-takeoff checklist
I normally have recourse to a whole group of pilots, but all of them are at Oshkosh, so I am putting this question up to you . . .
I had a customer call today. He built a Lancair and was doing some ground operational checks. He found that to cycle the propeller, he had to be above 1700 RPM, somewhere about 1775-1800 to get the prop to cycle on the ground. I told him that was fairly normal, and while some governors control to lower RPMs, that 1700 was pretty much the cut-off as far as controlling the prop would go.
He was concerned because, according to him, he was trained to “pull the prop back” (to a low RPM setting) in the event of a partial engine power event, such as a loss of compression in one cylinder, plug fouling, etc. and that he would not have prop control below 1700 RPM.
The prop he has, as do most single engine propellers, defaults to fine pitch (high RPM) in the event of a governor failure, loss of oil pressure, etc. If you had an engine that was running correctly, you’d have to reduce throttle to prevent an overspeed. In the event he is describing, however, he’d still have oil pressure and governor control, he just wouldn’t be able to produce full engine power.
It seems to me that if the engine can’t produce better than 1700 RPM in flight with the prop in low pitch (high RPM) then pulling the prop back to high pitch (low RPM) is exactly the wrong thing to do, and wouldn’t do anything for you anyway, as the prop would still be in an underspeed condition if you pulled the governor back to its lowest controllable RPM, and the prop would stay in low pitch.
If this was a twin engine aircraft, I could understand his “pull the prop” back training, as the pilot may opt to shut down the engine and feather the prop, but this doesn’t make sense to me in a single, unless the reason is to protect the engine in case the problem clears itself so that you don’t overspeed.
On the other hand, just leaving the prop control where it is seems to make the most sense to me. The engine is still making power, even though it is reduced power. The governor would be in an underspeed condition, and would put the prop in low pitch. Depending upon how much power the engine was still putting out, you could still fly, just not as fast, and if the low power condition cleared itself, the prop wouldn’t overspeed, as it would get “caught” by the governor at its original setting. His contention was that he needed the prop in the highest pitch it could get to, but higher pitch at low engine power would only make the engine run slower.
What say you??? Were you trained to pull the prop back when a low power condition occurred?
I had a customer call today. He built a Lancair and was doing some ground operational checks. He found that to cycle the propeller, he had to be above 1700 RPM, somewhere about 1775-1800 to get the prop to cycle on the ground. I told him that was fairly normal, and while some governors control to lower RPMs, that 1700 was pretty much the cut-off as far as controlling the prop would go.
He was concerned because, according to him, he was trained to “pull the prop back” (to a low RPM setting) in the event of a partial engine power event, such as a loss of compression in one cylinder, plug fouling, etc. and that he would not have prop control below 1700 RPM.
The prop he has, as do most single engine propellers, defaults to fine pitch (high RPM) in the event of a governor failure, loss of oil pressure, etc. If you had an engine that was running correctly, you’d have to reduce throttle to prevent an overspeed. In the event he is describing, however, he’d still have oil pressure and governor control, he just wouldn’t be able to produce full engine power.
It seems to me that if the engine can’t produce better than 1700 RPM in flight with the prop in low pitch (high RPM) then pulling the prop back to high pitch (low RPM) is exactly the wrong thing to do, and wouldn’t do anything for you anyway, as the prop would still be in an underspeed condition if you pulled the governor back to its lowest controllable RPM, and the prop would stay in low pitch.
If this was a twin engine aircraft, I could understand his “pull the prop” back training, as the pilot may opt to shut down the engine and feather the prop, but this doesn’t make sense to me in a single, unless the reason is to protect the engine in case the problem clears itself so that you don’t overspeed.
On the other hand, just leaving the prop control where it is seems to make the most sense to me. The engine is still making power, even though it is reduced power. The governor would be in an underspeed condition, and would put the prop in low pitch. Depending upon how much power the engine was still putting out, you could still fly, just not as fast, and if the low power condition cleared itself, the prop wouldn’t overspeed, as it would get “caught” by the governor at its original setting. His contention was that he needed the prop in the highest pitch it could get to, but higher pitch at low engine power would only make the engine run slower.
What say you??? Were you trained to pull the prop back when a low power condition occurred?
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