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8 Answers

Changing Blade Angle of a Fixed-Pich Propeller

Asked by: 10669 views Aircraft Systems

This is probably a bit more of a maintenance question, but here goes:  I am getting contradictary infromation about changing the bade angle of a fixed-pitch prop.  I have been told by many (one of whom was an A&P for about 40 years) that you can put the prop in jig and torq it to change the angle.  Another professor is saying that is madness and cannot be done.  I have been looking for answers, but there is not much out there on the topic.  Any links to credible infor would be great.  Thanks for your help!

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8 Answers



  1. Bill Trussell on Feb 27, 2012

    While I have not been able to locate any documents or links that says you can not do this, in theory it would induce fatigue at the hub at a minimum.  This is clearly not a good side effect as it would eventually lead to sudden departure of one or more blades.  This assumes that you are twisting it in a uniform manner
    My next question is “why would you want to do this anyway?” If you desire more of a climb or cruise prop, then go get one from the manufacturer and be done with it.  It would seem that the cost of the jig required to change the pitch in a uniform manner would outweigh any benefit in not going for a new prop, properly designed.  Never mind throwing a blade now and then.
    I would ask “what’s the point?” at this stage and turn it back over to you Jim.

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  2. Jim Foley on Feb 27, 2012

    I agree, I would be pretty hesitant to use one when it was my life up there.  It’s just that I’m getting mixed info from my professors, and just want to figure this out.  I suppose an email to McCauley is in order.

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  3. Kris Kortokrax on Feb 27, 2012

    I instructed many years in a Cherokee that had a cruise prop that had been repitched for climb.  The prop shop has the equipment to handle the job.
     
    Stress risers from nicks in the metal are far more likely to create a situation in which the blade will crack.
     
    As to your professors, “Those who can, do.  Those who can’t, teach”.
    Listen to the prof who is a 40 year A & P

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  4. Brian on Feb 28, 2012

    “The prop shop has the equipment to handle the job”

    I think this is what you need to take away from this. Just like you don’t rebuild your engine, you shouldn’t be twisting your prop with a 2×4 and some vice grips. However, properly equipped shops are capable of making such changes. Have a look:

    —–Can a PAC Wood or Carbon Fiber Propeller be re-pitched.It is possible to change pitch on all of our propellers. Modification of a propeller to correct for performance conditions may included re-pitch, reducing diameter, reshape of the chord width, thinning airfoil sections or a combination of these modifications.—–This is a company that specializes in aircraft propeller work, here is there site: http://www.princeaircraft.com/FAQ.aspx

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  5. Jim Foley on Feb 28, 2012

    Sorry Brian, my mistake.  I didn’t specify who was doing this.  I just kinda assumed that it would be understood that it would be rediculous to do in your basement.  Obviously it would be done by those certified.
    And from what I’ve heard, this is only for metal props, not wood or composite.
    I guess the biggest thing for me is that, even tho many people say it can be done, and have done it, I can’t find any publications or literature to prove that it can be done.  I emailed McCauley, so hopefully I can get some more insight into this.

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  6. Brian on Feb 28, 2012

    “I can’t find any publications or literature to prove that it can be done.”

    The site I posted is a propeller manufacturing company. Take a look at their resume and the aircraft companies they’ve built propellers for. It’s quite extensive. Also, it’s for metal, composite, and wood propellers. The question I quoted from their FAQ page asked about wood/composite being twistable; the reply said all of their propellers could be have pitch adjustments.

    —

    Here are other shops/custom prop manufacturers that perform repitching:

    http://www.aircraftpropellerworks.com/ – FAA Certified to include repitching.
    http://www.greatplainsas.com/ed.html – Custom wood props that can be reshaped/repitched.
    http://www.brinkleyaviation.com/propellers.html – This company re-pitches McCauley, Hartzell, and others.
     
    —
     
     
    Here is are some articles on Sensenich propellers:
     
    http://www.rv7.us/a_u-prop-repair.htm – Read notes 3 & 4
    http://www.sensenich.com/files/documents/Repairs_Trouble_Shooting_Repitch_Limits_1303228075.pdf
     
    —
     
     
    Here is a youtube video on the process:
     
    http://www.youtube.com/watch?v=VUKKLqcwd9o
     
    —
     
    I can’t find any technical documents that details the process. I’d suspect there are proprietary forces at work here, but that’s just a guess. I did find a class on McCauley propeller overhaul for $500 which noted discussion of how to repitch their propellers. I’m not sure if any of this is what you’re looking for, but I hope it helps. It would seem the mechanic was on mark.

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  7. Jim Foley on Feb 28, 2012

    Thanks for the links, Brian, that will keep me busy for a while.
    If anybody’s interested, here’s a copy of the reply I got from McCauley.  Not really what I was looking for but still some good info.  For example, I didn’t know you can repitch as many times as you want.  I’m not sure why he included the part about maximum pitch change, since I asked nothing of the sort, but still nice to know.
     
    “It is permissible to repitch McCauley fixed pitch propellers.  When you repitch a propeller by 1” pitch setting, either to a higher or lower pitch it will affect your RPM approximately 30 RPM.  Also you asked about maximum pitch change, McCauley does not have a maximum, but it is highly recommended that a maximum of 4 pitch change be used as further repitch may cause a wavy looking propeller, which is not pleasing to the eye.  As you may have guessed, it becomes very difficult to blend the stations with higher pitch change setting. 
     
     
    As far as McCauley is concerned as long as the propeller is within serviceable limits, the propeller can stay in service, this includes repitching as many times as you want and changing pitch as much as you want.”

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  8. Joseph A Stevens on Dec 08, 2012

    Tiffin air in Tiffin, Ohio repitched a prop for me. It is something to see. They put it in a jig and have a large tool with a long handle that slides over the blade and they twist it and measure until they get the right pitch. Most props can only be repitched two times.
    Why would you do this? To have a prop that climbs better, or cruises a little faster or just gets you out of that short field better.
    Why not just buy a new one as someone suggested. Just an average fixed pitch propeller can cost four thousand dollars or more new.

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