I'm told my hartzell three blade is not returning quickly enough when cycling during run up. I didn't realize the problem but a flight instructor recommended checking it out. Local shop agrees with his assessment. Current plan is to ship gov off for inspection then, depending on outcome, begin looking further into the hub. Does this sound like proper approach? 750 hrs since new.
CS Prop not returning to RPM
- Thread starter darylp
- Start date
CJones
Final Approach
How old is the prop (calendar and hours of service)?
We had a MT prop that would sometimes 'stick' at a particular pitch. Sent it off to MT and they did a full o/h on the prop. Even though it only had a few hundred hours on it, it was past the calendar time for recommended o/h.
We had a MT prop that would sometimes 'stick' at a particular pitch. Sent it off to MT and they did a full o/h on the prop. Even though it only had a few hundred hours on it, it was past the calendar time for recommended o/h.
JohnAJohnson
Cleared for Takeoff
Props have a limited amount of overhauls before they must be replaced. Many believe a prop should NEVER be overhauled, only IRAN'd. If your governor is ok and you decide to have your prop checked out, you might want to consider an IRAN instead of an overhaul.
Geico266
Touchdown! Greaser!
bbchien
Touchdown! Greaser!
Now you know why he sold you the airplane.
JohnAJohnson
Cleared for Takeoff
What is the difference?
I've got 600 hours and 7 years on my 2 blade CS.
Maybe not any difference. But an overhaul mandates grinding of the blades, which can be done three times max. What if blade grinding isn’t necessary?
The Savvy Aviator #8: Overhaul Overdone
You're not likely to even get one grinding if you send it to hartzell. Props have an odd history of becoming unservicable with ANY inspection at Hartzell.
KRyan
Pre-takeoff checklist
Daryl:
I'm assuming this is a single engine aircraft. If so, this prop is oil to high pitch (low RPM). If I understand your problem, you are able to go to low RPM, but the return to high RPM is sluggish.
For your prop to return to high RPM, your governor simply "dumps" the oil out of the prop. This is an actual mechanical action - your action on the prop control is physically lifting the valve spool in the governor to dump the oil.
I'd venture to guess that your governor will check out OK, and that the problem lies with your prop. It's probably cheaper to get the governor checked first - as mentioned, it is simply a bench test, whereas your prop will most likely have to be diassembled to determine if the problem lies with the prop. My best guess is you either have a "sludge" problem, a problem with the blade bearings (corrosion), or the hub is full of grease. On a Hartzell prop, if the grease procedure is not carried out in accordance with the manual, the hub can fill with grease and the prop will either be sluggish or not cycle at all.
I'm assuming this is a single engine aircraft. If so, this prop is oil to high pitch (low RPM). If I understand your problem, you are able to go to low RPM, but the return to high RPM is sluggish.
For your prop to return to high RPM, your governor simply "dumps" the oil out of the prop. This is an actual mechanical action - your action on the prop control is physically lifting the valve spool in the governor to dump the oil.
I'd venture to guess that your governor will check out OK, and that the problem lies with your prop. It's probably cheaper to get the governor checked first - as mentioned, it is simply a bench test, whereas your prop will most likely have to be diassembled to determine if the problem lies with the prop. My best guess is you either have a "sludge" problem, a problem with the blade bearings (corrosion), or the hub is full of grease. On a Hartzell prop, if the grease procedure is not carried out in accordance with the manual, the hub can fill with grease and the prop will either be sluggish or not cycle at all.
I should have mentioned this before. The prop control is extremely sensitive requiring only about half an inch movement from full forward to bring it back to 2400 rpm. Not sure how that impacts diagnosis.
KRyan
Pre-takeoff checklist
The sensitivity is more likely related to the rigging of the control to the governor, and shouldn't have anything to do with the problem you are having.
KRyan
Pre-takeoff checklist
How does it act in the air?
I found it to be fine. This started with an instructor making comment that prop did not seem to return to rpm quickly enough. Gov is off for inspection. If it comes back ok, can prop be cleaned internally without disassembly?
KRyan
Pre-takeoff checklist
No, it has to be disassembled
Marauder
Cleared for Takeoff
- Joined
- Oct 24, 2012
- Messages
- 1,463
- Display Name
Display name:
Marauder
When my governor went I saw an over rpm situation (above the 2700 red line) that I could only control by lowering the manifold pressure (reducing throttle).
I experienced a "sludge" thing as well. In my case, while doing a run-up, it would take quite a while for the prop to cycle (~10 seconds) to a lower rpm but would return to run-up rpm.
flyingmoose
Pattern Altitude
Yea that!
If u go from cruise to high speed in flight do u find it is still slow?
Most likely it is not unsafe. How slow is it? Couple seconds? A minute? More?
Sent from my iPad using Tapatalk HD
gismo
Touchdown! Greaser!
Even the some of the good prop shops (e.g. Maxwell) recommend IRAN instead of overhaul under most part 91 situations. An OH is likely to require replacement of some perfectly acceptable components that an experienced technician knows would easily go the distance to the next inspection. In any case I'd bet that an IRAN every 5-10 years is way better than an OH every 10-20.
N747JB
Final Approach
I had my 421 props "re-sealed" a couple years ago, they were 300 hours since new, almost 10 years old and one was "misting oil" the other was seeping a little. I could have just done one, but figured why put off the inevitable.
Anyway it was $2K per side, I think overalls would have been double, plus cutting the blades.
weirdjim
Ejection Handle Pulled
- Joined
- Jul 8, 2008
- Messages
- 4,171
- Location
- Grass Valley, CA (KGOO)
- Display Name
Display name:
weirdjim
That's an interesting heresy. Care to share your sources? Prop on my personal 182 has gone through half a dozen overhauls in its 50 year history.
Jim
gismo
Touchdown! Greaser!
AFaIK, it's only the blades that are limited in terms of overhauls and even there I think the "limit" isn't a specific number of overhauls, but rather the result of the combination of blade dimension limits and typical blade grinding required. You're prop might have required less removal of metal per o/h than average or maybe the blades were replace during one. I'm also wondering if it's possible that some or all of your prop overhauls were actually "reseals" as the names of the two procedures are often used almost interchangeably.
weirdjim
Ejection Handle Pulled
- Joined
- Jul 8, 2008
- Messages
- 4,171
- Location
- Grass Valley, CA (KGOO)
- Display Name
Display name:
weirdjim
You'da thunk that an A&P IA would be rather sensitive to that sort of stuff on their own bird, wouldn'cha?
Jim
gismo
Touchdown! Greaser!
Sure, but I couldn't tell if the "overhauls" you mentioned were performed when you owned the plane or before you had any direct control or knowledge of it's maintenance. Then again, I'm puzzled why a A&P, IA would opt for a prop overhaul every time assuming a good "inspection/repair" was an option.
Last edited: