Cycling the Prop

Alchemy

Alchemy

Well-Known Member
I have a quick question about cycling the propellor on aircraft with constant speed props. The runup checklist in 182RG I've been flying just says "Propellor-- Cycle".

However, my CFI has me cyle the prop three times during each runup. The first time I check for a drop in RPM, the second I check for a rise in manifold pressure, and the third time for a drop in oil pressure.

I was just wondering if everyone did it this way, or if some of you only did it once? Just curious, thanks.
 
Three is generally the "accepted rule." All you're really concerned about is that the prop will move when commanded, hold agiven setting and on twins (and some high-end/specialised singles) that the prop will feather. The "cycling" is just moving warm oil into the governor - cold oil makes the prop move slower.
 
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Yeap I have always done it 3 times.

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I'm confused, Iain. Not trying to be an ass, but aren't you a Private Pilot? If so, did you already get your complex endorsement?

I thought maybe you are confusing "Cycling" the prop (in a plane with a CONSTANT speek prop) with "Priming" = where you pump the primer three times before starting.

I'm pretty sure they are two entirely different things.
 
I have my private license and a complex endorsement, probably gonna go get my high performance endorsement soon too.

Cheers


John Herreshoff
 
Don't get me wrong. I know you CAN have both. Just wasn't sure that Iain did. I was curious... that's all.
 
I have both high performance and complex sign offs, with about 30 hours in an aircraft with a constant speed propeller. What gave you the impression I was referring to priming the engine?
 
Sweet! I thought you were talking about priming as opposed to cycling because of the reference to "three times". As you know, in most GA a/c, you have to pump the primer "Three times".

Just showing my ignorance. Carry on.
grin.gif
 
I also teach in an aircraft (Katana) that has a constant speed prop. It's not complex (fixed gear) yet I have many pre-private students in it. No big deal...
 
3 times seems to be the generally accepted method, but in reality it's a little bit of over kill. Once is enough to determine if the governer is functioning and to cycle the oil. Constant speed props have a calibrated leak designed into the system allowing for continous oil circulation, after 1 cycle a steady flow of warm oil should be assured.

That said I cycle it 3 times, was allways told to do it that way and it doesn't hurt...
 
Different airplanes have you check governor operation in different ways. Some like the Arrow and C182 just have you move the prop from full rpm to minimum rpm so you see and hear a drop in rpm. There will also be a drop in oil pressure as the governor uses engine oil to change prop rpm. If the airplane is cold, doing this 3 times is good because it will put warm oil into the propellor dome and make the prop more responsive. If the engine is warm, once is enough.

In most twins after the magneto check when the engine is still at 2000 rpm, the prop is pulled back several hundred rpm to make sure it holds at the desired setting. If you add 1/2" MAP the rpm should not change. If it won't hold its setting, you usually just adjust the quadrant friction lock, so the levers do not move. This can be done once when warm and 3 times when cold. Later in the runup the prop governors will be checked by putting the engines at 1500 rpm and moving the prop levers quickly into the feather detents and back up. You are looking for a max drop of 400-500 rpm and want to check oil pressure.
 
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I also teach in an aircraft (Katana) that has a constant speed prop

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What Katana has a constant speed prop? Is it the Lycoming powered ones?
 
I do it three times in the winter, and twice in the summer. Single engine, or multi engine, no matter. Same.
 
Thanks for all the feedback. I flew the 182RG for about 8 hours last weekend on a trip to mississippi, bringing my total complex time up to about 20 hours. Doing the runup procedure 4 or 5 times within a few days caused me to wonder about it, but it appears that 3 cycles is the generally accepted method.

Also, I hear some people say they let the RPM stay at a lower setting for a few seconds to see if the prop will hold its pitch at lower RPM's.....in the 182 I push the prop control back to full forward as soon as I notice the drop or rise in whatever instrument I am looking at. This is probably just a procedural difference between particular aircraft.....
 
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Also, I hear some people say they let the RPM stay at a lower setting for a few seconds to see if the prop will hold its pitch at lower RPM's

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NEVER do that unless it is a rental airplane, it puts way too much un-needed stress on the prop and hub. good way to get oil leaks around the seals. $$$

I run the prop three quick shots. as soon as I feel or see a drop, it is back to full. All I am looking for is no loss of oil pressure, and nothing sticking the gov. We had our Gov lock up in flight last year. Mech it prob had some "gunk" in it.

I think Gunk is Aviation term.....
 
Ian,
The Katanas with the Rotax engines have the constant speed props. That would be the DA-20-A1 designator, not the "C" series with the Lycoming.

You probably need the variable pitch prop on the Rotax engine because of the little power it produces. The engine makes no power to begin with (80hp), with a fixed pitch prop (inefficient) you'd get even less of the little power there is getting converted into thrust.

Even with the 80hp engine you get 172 performance on 3.5-4.5gph. Not bad.
 
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