Since we are on the subject of constant speed propellers, I Just have a question about run-up procedures in the PA32-300. (I own the Hartzell HC-C2YK-1).
The owner handbook states "The propeller control should be moved through its complete range to check for proper operation, then placed in full "increase RPM for take-off"".
Until last year,for the run-up, I always let the prop drop about 500 RPM two to three times as shown by most of my past instructors and other "experts" over the years.
My prop assembly went bad last year and started working less and less (e.g. gradually did not decrease when pulled back in flight). I really did not notice during the run-up until it after I noticed in the air. The prop assembly was replaced (a plus was that the eddy current inspection AD went away).
Finally the question is: Does anybody out there pull the prop control fully back during run-up?
I now do as the manual states but the engine decreases in RPM nearly to 500 RPM.
Just curious of what comments everyone has on the subject.
Well I'll be switched! My POH says the same thing (PA32-301):
"The propeller control should be moved through its complete range to check for proper operation..." It adds: "Do not allow a drop of more than 500 RPM during this check."
The POH instruction seems kind of silly to me. How can you "check for proper operation" when the engine's at 2,000 RPM? In concept, if you move the prop control all the way to the stop the RPM's should reduce to some specific number, which you would obtain out of a table corrected for density altitude. Piper doesn't exactly give us the tools for that. The non-quantitative check we all do insures the governor has warm oil and is operable. I doubt we'll ever get more information out of the test than that - it's right at the lower limit of the governor's ability to operate.
When I was taught High Performance, the instructor told me to never allow the RPM's to drop more than 300 or it could "damage the engine." It's probably worth asking how it could damage the engine and what would be damaged? I don't know.
I have a 1981 Saratoga and while you cannot check for full range during the ground run up, my instructor once told me at an idle while in flight to slowly move the prop control rearward and you can feel the drag load lightening as you move it. Maybe not as accurate as you'd like but you feel the slip as you glide. It surprised me as it felt as if the plane received a push from the rear.
I still wonder how many others have manuals that direct you to go through the full range with out the 500RPM drop disclaimer. Technically, (based on the little I know about constant speed props) I do not see a problem with going through the full range.
When I flew SIC in a B-25 with the Commemorative Air Force, our mechanic, (who had 50 years of experience) said that the props should go through the full range to reduce corrosion from moisture. It's been a few years since I reviewed the Manual(s) on that so I do not remember what was required.
I've been meaning to check our Arrow POH ever since I saw you do that. I'll check it out when I get back in town next week. No instructor ever told me to move the control over its entire range. It it's in the POH, I missed it.
I don't know that much about engines, but I'd guess that the RPM drop limit is intended to protect the engine against very high torque.
On the Pratt & Whitney 1340 we cycle the props through their full range. At the full low RPM position at run up power we get 1000-1200 RPM. We also shut the engine down at full low RPM to position the pistons in the hubs in the most protective position (dirt & moisture) and on start to allow the engine oil to initially lubricate internal engine parts more efficiently. Granted, this is a different animal.
My 69 180 Arrow AFM states "the propeller control should be moved through its complete range to check for proper operation and then be placed to increase RPM for takeoff."
Why there are some instructors who preach not to allow your RPM lever to go down to that "dark and forbidden zone" on run up I have no idea, other than some AFM's for some aircraft specify a max drop of 500 RPM so maybe they assume it's that way for all CS props.
The manual that came with my new prop this April has no RPM restriction unless there is one specified in the AFM.
I was instructed to fly each airplane in their respective realm of operating limitations including exercising the prop throughout its full range unless specified otherwise in the respective AFM. If you have an early Arrow (maybe later too) take a look at your RPM indicator. Notice there are two green ranges. The 500-2000 range is for ground operations, and the 2200-2700 RPM range is for flight. You will not hurt anything operating the equipment in the range it was designed to operate in.
I cycle the prop allowing only a 200-300 rpm drop at runup. Any more and you are putting excessive loads on the engine & prop. You do not want to risk blowing any seals when cold. I believe moving it full range might do that.
The goal at runup is to see that the lever changes oil flow/pressure to move the prop. If the oil is cold it will be sluggish so be careful not to over do it.
I have owned a couple of Sixes and have been teaching for 16 plus years. I teach to pull the prop handle back (every aircraft is slightly different) about 3/4 aft and then forward to the stop when the RPM hits 300 or so drop. You will get a 500 RPM drop as a result but if the oil is cool, the first or second change in prop may not get to the 500 RPM drop.
The above poster is correct in that Piper does not give us specifics as to full decrease and I to believe this will put way to much stress on the system to actually go past the 500 RPM drop since it is not a full feathering system.
When I flew the Piper Seminole at ERAU, we would go through the full range for each engine without the 500 RPM drop. I cant see a problem with doing so other than cycling the oil through the hub.
timmccall Wrote:
-------------------------------------------------------
> >
> The above poster is correct in that Piper does not
> give us specifics as to full decrease and I to
> believe this will put way to much stress on the
> system to actually go past the 500 RPM drop since
> it is not a full feathering system.
Are you referring to "beliefs,feelings" or mfgs. recommendations? Piper states the recommended runup procedures in the POH.
"The propeller control should be moved through its complete range to check for proper operation and then be placed to increase RPM for takeoff." This sounds like a specific pre take off operational check. You are not airborne pulling the prop lever to your lap at cruise power. It's a whole different story up there.
If you fear the structural integrety of your motor mount or have nightmares of watching your pistons poking through the sides of your cowl during runup, then it's probably best conduct your propeller check as you feel is best for your sanity.
Hartzell's number is 937-778-4379. They have no objection to checking the propellers operation up to the high pitch stop if it's not prohibited in the AOM with the approved prop / engine combination installed.It's probably done once a year on your Annual anyway.
Sounds like there are a lot of interpretations to what should be performed. I see there are many differing manuals and opinions. Nothing like something being standardized to make it easy on us.
One always wonder how much thought really went into writing the manuals and whether they really meant what they wrote. a 100 years ago out of college, for my first job, I was assigned to write service repair manuals for the McDonnell Douglas F-18 Hornet. Years later, after gaining experience, I know that some items could have been expressed better or some of the subject mater could have had ambiguous meanings. There was was a couple times that remember saying, how can they interpret that from that?
Hopefully Piper would not use "green" Engineers to write their manuals but if McDonnell Douglas would, I would imagine Piper would as well. (Don't worry, now that I'm gone, only perfect manuals are produced and all the old ones have been revised)
So, I guess I will follow the manual precisely and hope the experienced engineer or the green new hire at Piper knew what they were doing when it was written.
GM Wrote:
-------------------------------------------------------
> timmccall Wrote:
> --------------------------------------------------
> -----
> > >
> > The above poster is correct in that Piper does
> not
> > give us specifics as to full decrease and I to
> > believe this will put way to much stress on the
> > system to actually go past the 500 RPM drop
> since
> > it is not a full feathering system.
>
>
> Are you referring to "beliefs,feelings" or mfgs.
> recommendations? Piper states the recommended
> runup procedures in the POH.
> "The propeller control should be moved through its
> complete range to check for proper operation and
> then be placed to increase RPM for takeoff." This
> sounds like a specific pre take off operational
> check. You are not airborne pulling the prop lever
> to your lap at cruise power. It's a whole
> different story up there.
> If you fear the structural integrety of your motor
> mount or have nightmares of watching your pistons
> poking through the sides of your cowl during
> runup, then it's probably best conduct your
> propeller check as you feel is best for your
> sanity.
> Hartzell's number is 937-778-4379. They have no
> objection to checking the propellers operation up
> to the high pitch stop if it's not prohibited in
> the AOM with the approved prop / engine
> combination installed.It's probably done once a
> year on your Annual anyway.
Yep, you are correct in your statement. I have no issues with your interpritation of the POH statement. You are also correct that it is more of a general rule (warm and fuzzy) in the method used. My POH and hartzell manual say the same thing, full range. They also don't tell you what RPM to let the engine drop to. I have flown with several FAA inspectors (flight checks for my position at work) and they have all preached the exact same thing. You can move the prop lever from full forward to full aft (full range) but to not let the RPM drop all the way until there is no more change. Their reason is that it puts undue wear and tear on the systems. This may be a complete fabrication on their part but that is what I have been taught and heard my entire career.
With that said, at the low RPM and HP setting that we are doing the check at, I have to agree with you that no damage would occur by doing exactly what the POH states.
This subject sort of sounds like the Rich of Peak and Lean of Peak arguments out there. All of them correct.
