Exercising props?

popaviator

popaviator

Well-Known Member
I was looking at a Duchess checklist and during the runup it calls for exercising the props and looking for a 100-200 rpm drop. Why do you exercise the props and then later in the checklist a feather check?

The only explination I can find so far is that in cold temperatures you should exercise the prop so that oil can't congeal in the prop dome. ???
 
...and exercising is different than governing.

A governor and feather check is done once before each flight like magnetos, but the 'exercising' is pulling the props down 100-200 rpm about 3 times on a cold first flight to get the oil circulating in the governor.
 
Feather check checks the feathering system on the airplane, and also circulates the cold oil out of the prop hub. Exercise just makes sure that the governor will set a different RPM and hold it steady.
 
"Exercising" is done to get warm oil up into the governor and prop system. A feather check verifies that the governor will dump pressure to allow the prop to feather if you needed it to. A governor check is done to ensure that the governor is working properly. All different, but related things.
 
And you should only do these checks on the first flight of the day. There is no need to do a govern/feather check 6 times a day.
 
ryanmickG said:
And you should only do these checks on the first flight of the day. There is no need to do a govern/feather check 6 times a day.
Click to expand...

Couldn't disagree with you more. Your logic assumes that because it functioned normally for the first check, that nothing could have failed during the ensuing operations.

This logic has harmed more people than worn out systems by excercising the governor and feathering systems before each flight.
 
Dunno, I've seen a lot of prop leaks but I haven't had a governor go inop. I'm not saying it doesn't happen and I know it would be a bad thing, but I'm in the camp of exercising the props once a day.

It may be unfounded and unwise but that is how I see.
 
http://www.mccauley.textron.com/prop/prop-tech/pg01facts.html
http://www.warmkessel.com/jr/flying/td/jd/16.jsp

From #2:

"How many times should you cycle the prop? If the RPM drops smoothly and properly, once is enough. The fresh oil will probably cause the piston to move a good deal and when it comes back to the low pitch stops, most of the "old" oil will be pushed out. If you really want to feel good, do it twice, to get even more of that "old" oil out of there. Three times is gross overkill, in my opinion, but a lot of people do three times, or more. In reality, there are tiny bleed holes that allow a constant flow of warm oil to both sides of the prop piston, so even if you take off with cold oil in there, it will quickly be replaced with nice slippery warm stuff. On some of the big old props on the radials, in extreme Arctic conditions, the oil would congeal faster than the bleed ports could replace it, but I doubt you'll find any modern props with this problem. I should note for completeness that many of the props on the big radials might require many more cycles to achieve a smooth RPM drop when cold. In freezing temperatures, it may take up to ten cycles. There's a lot more to the mechanism, and a lot more oil involved."
 
popaviator said:
I was looking at a Duchess checklist and during the runup it calls for exercising the props and looking for a 100-200 rpm drop. Why do you exercise the props and then later in the checklist a feather check?

The only explination I can find so far is that in cold temperatures you should exercise the prop so that oil can't congeal in the prop dome. ???
Click to expand...

So they don't get fat?
 
In the cold weather make sure you let the prop fluid get nice and warm before you go "exercising" it. Doing it before it is warm enough can damage the seals.
 
Douglas said:
Dunno, I've seen a lot of prop leaks but I haven't had a governor go inop. I'm not saying it doesn't happen and I know it would be a bad thing, but I'm in the camp of exercising the props once a day.

It may be unfounded and unwise but that is how I see.
Click to expand...

Same here...flying a 182 jump plane with sometimes close to 20 loads a day would put a lot of stress on the components if we are checking the prop every single 0.3 - 0.5 flight
 
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