Just came across this thread.
I was taught to cycle prop 3 times.
one to watch that oil pressure drops.(governor operation)
two to watch that manifold pressure increases.(engine power safety)
three to watch for smooth rpm drop (smooth not notchy blade adjustment)
I do the prop cycle prior to mag check to load the engine first.
I use the higher 2000rpm check to put more pressure on the cylinders which can show a weak spark much better than lower pressure as is seen on the spark plug tester at annuual.
When I have run Franklins in the past, the manufacturer calls for a low and a high rpm mag check.
Jeremy
good to see many at JC though sorry I did'nt get time to chit-chat with all.
gets busy out there.

hotrod150 wrote: If anyone wants it, I'll sell the vernier throttle assembly for half the new price. I can get the Spruce part number & length if anyone's interested. Eric

It's an A-750 throttle cable assembly, 48" long, 10/32 thread on the carb end & a 3/4" hole in the panel required at the other end. Sells for $60 new at Spruce.

Jeremy,

I was taught the three pulls, and their meaning as well. I got to thinking about it, though, which is why I started asking the manufacturers why 3 pulls.

Consider this:

1) one to watch that oil pressure drops.(governor operation)
If the prop cycles, you'll hear it. If it cycles, oil pressure HAS to drop to accomplish the cycling.

2) two to watch that manifold pressure increases.(engine power safety)
Again, if the prop cycles, the manifold pressure HAS to drop proportionally. Basic physics.

Have you ever had one cycle and the oil pressure NOT drop or MP NOT rise? I haven't, which is why I started asking. One of the prop manufacturers reps and a well known engine rep and I were discussing this one day, and they both agreed that if the prop cycles, MP will increase and oil pressure will drop.

That shot my old learnings in the butt, though they always sounded good, and gives you something to do while you're cycling the prop three times.

I still couldn't get the prop guys to say that you should only cycle the prop once, though. They just couldn't give me a good reason for doing so three times.

So, what you describe is good operating practice, but I'm not sure it really means much.

If it cycles smoothly once, it may be good enough, but.....

MTV

Cycle it three times to flush the oil through the crank and dome, and apparently in cold weather to get the cold oil replaced with warm oil. I have not operated piston engines in artic conditions, but some that have have told me it's not uncommon at all for the prop to respond slowly on the first cycle and better on the second, but should respond normally by the third cycle, or I guess they keep cycling it until they get a normal response?
My cold WX experience is with turbines.

Well now I see this thread has some good activity.

Yes I cycle three time, just like I was taught by pilots with more years of flying than I'll ever have. I can say that yes, in cold weather it takes a bit to cycle the first time, quicker the second and right on the third?

So does cycling the prop three times, make it a tri-cycle?

C ya, Bub

The oil doesn't actually go anywhere at least on a IO-520. There is an oil transfer collar on the front end of the crankshaft which supplies oil pressure to the governor which increases the pressure to the propeller dome to offset the counterweights and hold rpm. That's why there is baby shit in the crank snout, it acts as a centrifuge. I cycle mine on the taxi roll.

That is what the no prop cycle guys are saying that the oil does not go anywhere. That the governor provides the oil to the prop. While others say cycling the prop keeps the sludge from accumulating. At this point I am going to settle for a compromise and prop cycle first flight of every day. At least I will know the prop is working before the days flying. Besides I am not convinced it will do any more harm then flying the aircraft.<a href="http://plugin.smileycentral.com/http%253A%252F%252Fwww.smileycentral.com%252F%253Fpartner%253DZSzeb008%255FZNfox000%2526i%253D4%252F4%255F12%255F3%2526feat%253Dprof/page.html" target="_blank"><img src="http://smileys.smileycentral.com/cat/4/4_12_3.gif" alt="SmileyCentral.com" border="0"><img border="0" src="http://plugin.smileycentral.com/http%253A%252F%252Fimgfarm%252Ecom%252Fimages%252Fnocache%252Ftr%252Ffw%252Fsmiley%252Fsocial%252Egif%253Fi%253D4%252F4_12_3/image.gif"></a>

Absolutely correct the oil doesn't go any where, but just like a turkey baster if you empty and refill it a couple or three times you will exchange some oil with what is in the engine, not all of it of course, but some of it.

Another point of view says that pulses of fresh oil, i.e. the three prop cycles, will tend to flush the mechanism with fresh oil and dissolve the sludge in the dome. Obviously you don't want to lug the engine for an extended period of time. I think we've all had some time on a hose to get the gravity of this concept.

So far I read two people that asked manufacturers about the cycling.

First of all they write the POH, so they won’t tell you to ignore the POH.
Secondly, the POH is written by lawyers.

I am in the aviation business and believe me, QRH, POH, AFM’s, AOMs’s whatever the name, are all written by lawyers. So in general you should follow the books/manuals, but also understand that those books/manuals are not necessarily written to operate the aircraft most economically (maintenance cost and fuel cost) and that they are generally written conservatively.
In addition a certified aircraft that gets technically upgraded will often use the same limitations even if the new items do not require it. This saves recertification and therefore costs.

So you do cycle x amount of times because the manufacturer says so, or you don’t because you technically understand what is going on.

Im always amazed at questions like this. You should do what the checklist AND what the manufacturer tells you you should do and not what Cletus tells you over coffee you should do. It's that simple.

gregwyatt wrote:Im always amazed at questions like this. You should do what the checklist AND what the manufacturer tells you you should do and not what Cletus tells you over coffee you should do. It's that simple.

Actually, using your brain is a relatively important function for pilots. There are lots of things on GA checklists that are pure legal boiler plate.

Doesn’t suggest throwing the checklist out, but……

MTV

Hey that’s an old timers thread. A couple of them guys got kicked off BCP. Hell maybe even dead by now.

I always cycled the prop on the 1st flight too. Guess because Grandpa did it that way.

gbflyer wrote:Hey that’s an old timers thread. A couple of them guys got kicked off BCP. Hell maybe even dead by now.

I always cycled the prop on the 1st flight too. Guess because Grandpa did it that way.

Indeed! I see examples of both Some of them even wrote like they had Covid....
I do what mike said and made my own mind, because I've know technical writers... they're a lot like gov't check airmen that certify people in stuff they've never operated..... and because I've flown planes owned by a Cletus or two

Interesting discussion I've not seen before. I'll tell you my experiences for no other reason than I feel like it.... I'm a licensed mechanic, the Aussie and NZ equivalent of an A&P with an IA. 32 years on the tools and 31 years as a pilot

I always cycle the prop, how many times depends what happens on the first cycle, or what I feel like doing. Definitely before the first flight of the day and often on subsequent flights. If it's an unsealed area I might do it while on the taxi or rolling so the prop doesn't get damaged

Over the years I have had a number of instances where the prop cycling has identified an issue.

Many years ago in a Mooney M20J, I cycled the prop on taxi for the second or third flight of the day, the RPM dropped and stayed there. For some reason the piston had galled in the cylinder and seized. Never seen it happen before or since

All other instances have been with piston twins. The props would cycle fine, but wouldn't feather. Obviously a less than desirable scenario

In Australia, CASA mandate an AD applicable to feathering props fitted to piston engines... To ensure propellers are capable of feathering when required, a ground functional check is introduced. Regular feathering of propellers will reduce the engine oil sludge build up in the propeller dome and aid in redistribution of grease in blade bearings

When I moved to New Zealand, I was concerned to see mechanics never feathered the props on piston twins. I have always done a 'shut down' feather check, then used paddles to put the blades back to fine. Quite a number of the props I tried to feather would go about halfway coarse, but not even close to feather, but using the paddles to rotate the blades always cleaned out whatever was catching the pistons and then they would feather correctly. Could be a little unpleasant in a twin at gross weight and unable to feather a prop if needed

I do a shutdown feather check each 100 hours or 12 months.

Follow your POH or AFM