overhauling cessna prop

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bobkiksass

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bobkiksass
I am wondering if anyone has experience with what the standards are for overhauling a cessna 150 prop, mccauley. Mine has a small bit of corrosion on the leading edge, my mechanic thinks I should have it overhauled and ballanced due to some vibration. It is original from 76 and has around 10k hours on it. The corrosion looks like it would come off with a bit of scotch brite, its only started on the prop in the last 6-9 months. He is concenred that the people who overhaul it might reject it because on the small bit of corrosion. He said if we removed it, and gave it to them and they rejected it that he would not put it back on the plane due to liability.

Can anyone reccomend a prop overhauler in so cal that would tell me before I gave them if the prop is up to their standards. I can send pictures to verify before hand. I dont want to remove it if I wont be able to put it back on. I think I could fix it up with some scotch brite and paint, but the mechanic thinks the ballance is off and Id really like to get that fixed thru an overhaul. He suggested I could find one ready to be overhauled.

He thought around 900$ to overhaul the prop, does that sound right ? Any advice ? What should a used one thats overhauled cost ?
 
That many hours, save some money and call McCaulley and ask for the dimentions for the chord lengths,

I'd be a beer that it is undersized already and would be rejected for that reason
 
Santa Monica propellor, but as Duncan said, measure it first because it's likely been worked down before.
 
Agreed with Duncan and Henning... get the chord specs at each station and measure it....
 
bobkiksass said:
I am wondering if anyone has experience with what the standards are for overhauling a cessna 150 prop, mccauley. Mine has a small bit of corrosion on the leading edge, my mechanic thinks I should have it overhauled and ballanced due to some vibration. It is original from 76 and has around 10k hours on it. The corrosion looks like it would come off with a bit of scotch brite, its only started on the prop in the last 6-9 months. He is concenred that the people who overhaul it might reject it because on the small bit of corrosion. He said if we removed it, and gave it to them and they rejected it that he would not put it back on the plane due to liability.

Can anyone reccomend a prop overhauler in so cal that would tell me before I gave them if the prop is up to their standards. I can send pictures to verify before hand. I dont want to remove it if I wont be able to put it back on. I think I could fix it up with some scotch brite and paint, but the mechanic thinks the ballance is off and Id really like to get that fixed thru an overhaul. He suggested I could find one ready to be overhauled.

He thought around 900$ to overhaul the prop, does that sound right ? Any advice ? What should a used one thats overhauled cost ?
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You need to fire your A&P. they must know how to blend a prop and feather out any damage.

your's apparently doesn't.
 
Tom-D said:
You need to fire your A&P. they must know how to blend a prop and feather out any damage.

your's apparently doesn't.
Click to expand...

I wasn't going to go there not having all the info, I am hoping the real reason the mechanic isn't happy with the prop is the vibration. Corrosion on the leading edge is typically not a big deal to fix
 
Skylane81E said:
I wasn't going to go there not having all the info, I am hoping the real reason the mechanic isn't happy with the prop is the vibration. Corrosion on the leading edge is typically not a big deal to fix
Click to expand...

How do we know the vibe is in the prop?

If the A&P is that unknowledgeable, how do we know the prop is indexed properly?

If the Vibe is in the prop why doesn't he get it balanced? after he cures the corrosion problem?

Why the overhaul? does he believe that will cure a vibe?
 
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Skylane81E said:
You and I, we don't. However a 10,000hr prop isn't a bad place to start looking either, especially if it has developed over time.
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Vibrations don't simply grow in a prop, if you got a vibration that has start and is getting worse don't look for it in the prop.
 
We don't have all the data to make that call for the OP.

Besides, if it needs a new prop anyway what's the harm?
 
Skylane81E said:
We don't have all the data to make that call for the OP.

Besides, if it needs a new prop anyway what's the harm?
Click to expand...

new prop? about 2500 bucks.

If it met specs when it was put on, why wouldn't it meet them now? Did some one grind the hell out of it while installed?

McCaulley ICAs allow cleaning blending and corrosion control, why not do that rather than send it in to be condemned ?

If the A&P doesn't know this simple stuff, I sure wouldn't allow them to work on my engine.
 
Tom-D said:
Vibrations don't simply grow in a prop, if you got a vibration that has start and is getting worse don't look for it in the prop.
Click to expand...


Sure it can. Its call loose or broken prop bolt, cracked prop flange or even a cracked crankshaft flange.
 
Tom-D said:
If the A&P doesn't know this simple stuff, I sure wouldn't allow them to work on my engine.
Click to expand...


Your know-it-all atidude = complacency in my book. You won't be working on my airplane.
 
bnt83 said:
Sure it can. Its call loose or broken prop bolt, cracked prop flange or even a cracked crankshaft flange.
Click to expand...

that is not the prop its self. the 150/152 prop is a block of aluminum, it won't grow or shrink all be its self.

You can bet on it,, you can also bet I don't send fixed pitched props in for overhaul.

have you ever seen what is done to a blade when they overhaul it? it can only be done a certain numbers of time before they throw it away. so why send them in
 
Tom-D said:
have you ever seen what is done to a blade when they overhaul it? it can only be done a certain numbers of time before they throw it away. so why send them in
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I'm well aware of what they do to props. I'm also aware they wear out, don't last forever, and they do break. If this prop has 10,000 hrs, that was $0.25 per hour to fly the prop.
 
For all we know this O-200 suffered a prop strike years ago but the crank checked out and was returned to sevice. It looks to me about 25% of those cranks break later in service. If you research SDR's you'll find there are several O-200 crank failures that had a history of prop strike.


Edit: All it has to do is crack between two bushing holes in the crank flange.
 
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Tom-D said:
new prop? about 2500 bucks.

If it met specs when it was put on, why wouldn't it meet them now? Did some one grind the hell out of it while installed?

McCaulley ICAs allow cleaning blending and corrosion control, why not do that rather than send it in to be condemned ?

If the A&P doesn't know this simple stuff, I sure wouldn't allow them to work on my engine.
Click to expand...

And if its been dressed beyond limits I don't need to send it in to be condemmed, I will do it for McCaulley. Last prop I pulled was 8,000hrs old and 1/8 under minimums.

Don't wory I don't need to work on your engine and you don't need me to
 
bnt83 said:
I'm well aware of what they do to props. I'm also aware they wear out, don't last forever, and they do break. If this prop has 10,000 hrs, that was $0.25 per hour to fly the prop.
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I can live with that life, 34 years and 10,000hrs?

Still willing to buy the OP a beer if it not undersized...
 
Skylane81E said:
I can live with that life, 34 years and 10,000hrs?

Still willing to buy the OP a beer if it not undersized...
Click to expand...


If OP needs a new prop him/her can always sell the old with a nice coat of paint in prep for a lifetime of service hanging on a wall :lol:
 
bnt83 said:
I'm well aware of what they do to props. I'm also aware they wear out, don't last forever, and they do break. If this prop has 10,000 hrs, that was $0.25 per hour to fly the prop.
Click to expand...

And any good A&P can do a blade profile and know if it meets the limits. When it meets the limits why not do the ICAs and continue in service?
 
bnt83 said:
For all we know this O-200 suffered a prop strike years ago but the crank checked out and was returned to sevice. It looks to me about 25% of those cranks break later in service. If you research SDR's you'll find there are several O-200 crank failures that had a history of prop strike.


Edit: All it has to do is crack between two bushing holes in the crank flange.
Click to expand...

Now you bloviate about things not in evidence.
 
Tom-D said:
new prop? about 2500 bucks.

If it met specs when it was put on, why wouldn't it meet them now? Did some one grind the hell out of it while installed?

McCaulley ICAs allow cleaning blending and corrosion control, why not do that rather than send it in to be condemned ?

If the A&P doesn't know this simple stuff, I sure wouldn't allow them to work on my engine.
Click to expand...

10,000 hours of dressing and filing nicks and such takes its toll.
 
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Henning said:
10,000 hours of dressing and filing nicks and such takes its toll.
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Wouldn't you know if it did? Would you have to send it to the prop shop to find out?
 
Tom-D said:
Wouldn't you know if it did? Would you have to send it to the prop shop to find out?
Click to expand...

No, I said measure it first. If it measured up I'd rack it onto a wheel balancer to check static balance and trim it up if need be and give it a spin by hand to check the tracking and tweak that a bit if required. Anyone who has ever observed a prop being worked on understands this is not an area that requires one to be particularly delicate lol. After it went back on I'd dynamically balance as well and call it done. If it didn't measure up I'd call the salvage yard and get another.
 
Tom-D said:
where ?
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What's the ICAW say? I'd imagine it measures in length and across the cord in some places. It may even have a minimum weight it has to meet. I don't know, I've never owned a fixed pitch prop. If there are no standards, clean and dress, balance it and throw it back on. It's a solid prop, not a big deal so long as it's not cracked, in balance and performs adequately. I've straightened boat props under water with a hammer and a dolly block before.
 
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Tom-D said:
where ?
Click to expand...


What do you mean "measure it where".......

The manufacturer has specs on the approved width at each station.. Stations are points along the prop moving outward from the center hole. At each station you get a venier caliper and measure the width.... Do that at all the stations and then measure the total length ,and either it is legal or it is NOT.... GEEZ..

I would really like to think you knew all this................
By making the statement "WHERE", makes you look incompetent.... Which I am beginning to think you are...:dunno::confused:
 
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N801BH said:
What do you mean "measure it where".......

The manufacturer has specs on the approved width at each station.. Stations are points along the prop moving outward from the center hole. At each station you get a venier caliper and measure the width.... Do that at all the stations and then measue the totla length ,and either it is legal or it is NOT.... GEEZ..

I would really like to think you knew all this................
By making the statement "WHERE", makes you look incompetent.... Which I am beginning the think you are...:dunno::confused:
Click to expand...


I find it odd that Tom cannot give maintenance advice without using this phrase:

"If your mechanic cannot ________________ they need to be fired!"

Its in almost every thread he posts in.
 
bobkiksass said:
I am wondering if anyone has experience with what the standards are for overhauling a cessna 150 prop, mccauley. Mine has a small bit of corrosion on the leading edge, my mechanic thinks I should have it overhauled and ballanced due to some vibration. It is original from 76 and has around 10k hours on it. The corrosion looks like it would come off with a bit of scotch brite, its only started on the prop in the last 6-9 months. He is concenred that the people who overhaul it might reject it because on the small bit of corrosion. He said if we removed it, and gave it to them and they rejected it that he would not put it back on the plane due to liability.

Can anyone reccomend a prop overhauler in so cal that would tell me before I gave them if the prop is up to their standards. I can send pictures to verify before hand. I dont want to remove it if I wont be able to put it back on. I think I could fix it up with some scotch brite and paint, but the mechanic thinks the ballance is off and Id really like to get that fixed thru an overhaul. He suggested I could find one ready to be overhauled.

He thought around 900$ to overhaul the prop, does that sound right ? Any advice ? What should a used one thats overhauled cost ?
Click to expand...

Dear Bob?

Vibration is a tricky thing to diagnose and we have very little information to go on. Everyone here is certain that your prop will not pass an overhaul, and probably is true. Without a picture of the corrosion / erosion we can't really comment on the issue. There are cheaper alternative props you can replace it with if in fact you do need a new prop.

Filing/blending the prop is a very common practice to remove nicks and corrosion damage and must be done by an A&P in accordance with the prop maintenance manual. Here is some general information on prop care:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/895eff1883ee06768625707b00727fd6/$FILE/AC%2020-37e.pdf

Here are some ideas for troubleshooting your vibration,

Prop Group

#1 Prop Indexing -The prop must be clocked correctly (indexed) on the crankshaft or this can induce unusual vibration. If incorrect, an A&P can simply remove it and reinstall it in the correct position. This only applies if the vibration suddenly shows up after re-installing the prop at which time it may have been indexed wrong. (See page 31 of AC-20-37E in the FAA link above)

#2 Blade Track - If both blades do not pass within the same plane of rotation this can induce vibration. A very slightly bent prop will not track correctly. (See page 11 of AC-20-37E in the FAA link above)

#3 Spinner - May be installed off center. This can be seen when the engine is running as the spinner will wobble. The spinner and prop assembly may have been dynamically balanced at one time and it's crucial to index the spinner correctly to keep that dynamic balance. Spinner cracks and improper hardware could cause it also.

#4 Prop Bolts - Could be loose or broken. This isn't likely but can happen.

#5 Cracked Crankshaft Flange - Unlikely.

#6 Cracked Prop Flange – Again unlikely.

Engine Group

#1 Magneto Improper Timing


#2 Spark Plug Not Firing – Fouled spark plug or plug with high internal resistance. Also can be caused by worn out & shorted ignition harness or a weak magneto.


#3 Weak Magneto – can be caused by a number of internal magneto issues. A bad coil will short out when hot but can pass a mag drop check when the engine is cold. If you do a mag check in-flight with engine hot and have a bad coil, the engine will run very rough or not at all on the bad magneto. Take note of which ignition switch position the engine symptoms occur and tell your mechanic. A weak capacitor can hinder magneto output which can cause the higher resistance spark plugs to misfire. Improper internal magneto timing otherwise known as E-gap could be wrong. Internal mag timing does drift a little in service as parts wear.


#4 Leaky Induction Manifold – Messes up the fuel/air mixture that each cylinder receives, making one (or more) cylinder run much leaner than the others.

#5 Sticky valve - Pretty sure you wouldn't fly it after experiencing this in flight on a 4 cylinder engine.

#6 Worn out engine vibration isolators (Rubber Engine Mounts)

Edit: all that being said, I wouldn't send it to a prop shop without rubbing the leading edge with scotchbrite, removing the corrosion and measuring the blades. If the prop is undersized already, there is no point in sending it to a prop shop and paying the shipping costs and any possible reject fees.
 
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I sold the McCauley off my Vagabond and
wanted to verify it was airworthy.
I called McCauley and they would not give me
anything other than total length numbers.
Told me to have a prop shop check it.
Since I am able to measure, I was a little miffed,
Also identified myself as A&P IA.
My Sensenich prop is great and they are very helpful.

Dave
 
d.grimm said:
I sold the McCauley off my Vagabond and
wanted to verify it was airworthy.
I called McCauley and they would not give me
anything other than total length numbers.
Told me to have a prop shop check it.
Since I am able to measure, I was a little miffed,
Also identified myself as A&P IA.
My Sensenich prop is great and they are very helpful.

Dave
Click to expand...


Hmmm..

I am not sure if you told Mc Cauley you were a A&P IA t,hey could deny you that info as you were going to use it for a flight safety check /test on one of their products..:dunno::dunno:
 
N801BH said:
Hmmm..

I am not sure if you told Mc Cauley you were a A&P IA t,hey could deny you that info as you were going to use it for a flight safety check /test on one of their products..:dunno::dunno:
Click to expand...


OEM's are not requird to give away data. They even can charge for SB's that even AD related.
 
N801BH said:
Hmmm..

I am not sure if you told Mc Cauley you were a A&P IA t,hey could deny you that info as you were going to use it for a flight safety check /test on one of their products..:dunno::dunno:
Click to expand...

Vary common, the A&P can not do repairs to a prop other than what is written in the instructions for continued airworthiness. So the company lawyers are simply doing a CYA for the manufacturer. all other repairs are in the overhaul manual used by the certified prop shops.

All A&Ps should know the limitations of their certificate. The OP's A&P probably doesn't want the liability of working on a prop. many A&P's won't work on mags either.
 
bnt83 said:
I find it odd that Tom cannot give maintenance advice without using this phrase:

"If your mechanic cannot ________________ they need to be fired!"

Its in almost every thread he posts in.
Click to expand...

Get real.

I believe the A&P should know what they are talking about, and be able to communicate that to their customers.

If the offends you, that is simply your problem.
 
d.grimm said:
I sold the McCauley off my Vagabond and
wanted to verify it was airworthy.
I called McCauley and they would not give me
anything other than total length numbers.
Told me to have a prop shop check it.
Since I am able to measure, I was a little miffed,
Also identified myself as A&P IA.
My Sensenich prop is great and they are very helpful.

Dave
Click to expand...

I have always gotten the data, but I also tell them that I think that after I get the data and measure I will be buying a prop from them. Maybe that shifts their motivation?
 
Well, if they don't give the dimensions for an IA to be able to measure, then the IA cannot condemn the prop for bad measurements. Check the balance and track, clean and paint, bolt it on and do a dynamic balance and be done with it.
 
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