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Thread: Piper Service Life

  1. #1

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    Piper Service Life

    I've been reading a lot about the unfortunate situation Australian (and other) Cessna owners have with SIDS-type inspections in which the inspection costs sometimes exceed the value of the aircraft. It got me to thinking about aging aircraft in general and Super Cubs in particular.

    Apparently, a lot of the Cessna problems come from a design philosophy that their original service life would be 18 years (I read somewhere). If true, with a lot of their aircraft well past that expectation it's not really surprising that repairs would be needed.

    Did Super Cubs have design life that short? It seems unlikely, given that the fabric (I read) is supposed to be good for 50 years. Still, (again, I read) that some of the recovering projects find other things to fix, so that implies necessary issues. Are these issues primarily corrosion?

    On the short wing piper site, Steve Pierce (in 2012?) cited an aging aircraft web site, which now apparently is no longer updated. Are we no longer concerned about this?

    As always, if I'm thinking about this wrong and my thought process would be improved with re-phrasing, please let me know.

  2. #2
    cubdriver2's Avatar
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    The beauty of a Rag & tube aircraft is that it can be repaired/restored by almost anyone. If something is worn out or bent then replace it. Simple design that only requires simple tools to make airworthy again. The biggest expense is time. The prettier you want it the longer it will take

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    cruiser's Avatar
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    No Skip, I am not going to say it

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    Cubs came with cotton covering. Not a 50 year fabric if left outside. Hard to find a factory cub fuselage that will not need a few/lot of tubes replaced due to rust. We are way past the expected life of most all older aircraft. Look at the military bombers/tankers, Beavers, and all the other stuff we keep upgrading. One of the best things that can happen to a old aircraft is for someone to fall hard in love and bend it. With the help of the right IA it can be truly made better than new. I have a 1951 PA18A I think the only things that came from the factory are the seat, altimeter, and stick. If you are looking for a Cessna find one that has had a rebuilt gearbox (by a good shop) and you will be ahead of the game. If you look at what experimental guys/gals are doing today, the are building planes using the same techniques used 60 years ago because it works. You can replace every part on a Cub, Cessna, and Beaver or build new but it usually looks a lot like the old stuff.
    DENNY
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    Quote Originally Posted by DENNY View Post
    You can replace every part on a Cub, Cessna, and Beaver or build new but it usually looks a lot like the old stuff.
    Okay, I take it then that you can replace everything you need to in order to avoid complete obsolescence. Like a BMW opposed twin motorcycle this continues to be economically an reasonable possibility as long as we are willing to keep the used prices high enough. Good enough, thanks.
    Last edited by Jaywalker; 10-26-2017 at 10:39 PM.

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    I would not say it was economically reasonable!! It is just what I do a 1951 PA 18A is the best machine for the job. I am at a point in life that I can spend the money to keep it flying. I will put my cub up against any new factory plane for my mission. If I wanted to be economical I would buy a pacer. Some of the new stuff is really nice and will perform, but, bang for the buck old metal rules!!!! If you are looking to buy find a plane that has recent hard crash with proper rebuild.
    DENNY
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  7. #7
    Steve Pierce's Avatar
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    The FAA quit funding that project. They were late to the game. The idea was that owners could discuss the problems they were finding with aging aircraft openly without the FAA using it against them. That was already happening through forums like this and ShortWingPipers.org. Most CAR 3 airplanes are not life limited but most Part 23 airplanes I have seen the maintenance manual on have life limits at which point they are to be removed from service.
    Steve Pierce

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    Here in the US we have the Administrative Procedures Act. In short, it says any agency that wants to pass a regulation that will cost $ to the public has to have na NPRM and the public has the ability to comment on it. Since all these airplanes were certified without life limits or mandatory inspections (beyond an annual), to impose such a requirement would invoke the APA requirement for public comment. How many aircraft owners would make positive comments to such a proposal? Not many, and it would be a waste of time and money on the part of FAA.


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    I'm seeing more and more businesses selling a product and then a service contract to go with it, then replacing the entire product after 4 or 6 or 10 years. Buy a new jet and sign up for the engine plan, you are essentially paying for the engine twice - once upfront, then per hour as you go along (with a 150 hour/annum minimum). Who ever gets to TBO on a business jet? I've seen one Westwind with more money in the engine fund than it is now selling for. But to unlock that money, you have to fly for another 2000 hours, and pay another $300,000.

    An Aerostar has a life limited windshield - around 4600 hours. A Piper Seminole and Tomahawk have life limited wings. I believe the Cessna SIDS program is good. At the very least it points private owners at the areas that need to be looked. Planes, buildings, cars are always designed with a certain service life in mind. I believe German cars are designed for 3000 hours. Look after it in an easy environment you are going to get more. Abuse it in a tough environment, then less.

    A Super Cub probably has a very high or infinite fatigue life, but I suspect most fuselages will corrode or be bent before reaching that point. And what fatigue failures there are are probably more related to landings than flight time?

    One of the huge attractions to Super Cub's is the ability to keep repairing and replacing components at a reasonable price from multiple sources with involving the OEM. How many other planes can you do that too?

    Aerodon

  10. #10
    behindpropellers's Avatar
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    Fairly certain that there are components in the Top Cub that are life-limited.

    Tim

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    Steve Pierce's Avatar
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    Quote Originally Posted by behindpropellers View Post
    Fairly certain that there are components in the Top Cub that are life-limited.

    Tim
    I just happen to have that manual handy. Don't know why stabilizers have such a short life.
    Attached Files Attached Files
    Steve Pierce

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  12. #12

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    A lot of what Cessna wrote into the SID inspections makes good sense. I have a copy of the SID for my airplane on my desktop and I refer to it often. Nothing in the instructions is worrisome to me but parts of it are difficult (expensive) to do. Skins on a Cessna are structural so seeing what's underneath them isn't always simple. Compare that to a Cub? Very different. After stripping the cover some guys dink and clink on their old airframes and return them to service. Others will replace with new (that's a real Cub advantage). Wing structure is easy to inspect and repair with the fabric off. Tail feathers and control surfaces are easy to repair or replace. Some guys replace things like gear bolts every year. Some are riding on really old ones. The variation in quality in the Cub fleet is wide. The same can be said of Cessnas. You can buy a beater old Cub and make it new again pretty easily. All it takes is money. To buy an old beater Cessna and make it new? Much more difficult and much, much more money.

    None of them was meant to last forever.
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    mvivion's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I just happen to have that manual handy. Don't know why stabilizers have such a short life.
    Take a look at your stabilizer during max power operation, particularly with flaps deployed. Those parts get beat and thrashed pretty hard, particularly with 180 hp. May or may not be the reason, however.

    MTV

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    Steve Pierce's Avatar
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    Quote Originally Posted by mvivion View Post
    Take a look at your stabilizer during max power operation, particularly with flaps deployed. Those parts get beat and thrashed pretty hard, particularly with 180 hp. May or may not be the reason, however.

    MTV
    Yea but I see more issues with elevator bushings and trim yokes than the actual stabilizers.
    Steve Pierce

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  15. #15

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    Quote Originally Posted by behindpropellers View Post
    Fairly certain that there are components in the Top Cub that are life-limited.

    Tim
    Seat cushions?!? Really?
    When did a seat cushion become a structural item?

    George

  16. #16
    Steve Pierce's Avatar
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    Quote Originally Posted by NE Cub View Post
    Seat cushions?!? Really?
    When did a seat cushion become a structural item?

    George
    Part 23 seats have to withstand so many Gs and they do it with the seat cushions. They do get harder over time. I can attest to that after my latest trip to Utah.
    Steve Pierce

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  17. #17

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    Quote Originally Posted by Steve Pierce View Post
    Part 23 seats have to withstand so many Gs and they do it with the seat cushions. They do get harder over time. I can attest to that after my latest trip to Utah.
    Correct, for a Part 23 airplane, all the components that make up the seat including the upholstery make up the "certified seat" the holes in the seat pan on the 172R &S are designed to allow the foam of a specific density to extrude through allowing energy absorption to meet the standard.


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    Friend of mine had to do SIDS inspections on his C130 here in NZ. He imported it from the US and only had about 3000 hours on it. It had been really looked after in the US and surprise surprise they found nothing to repair. I think it should be done but on high time aircraft that really are showing their age!

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  19. #19

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    Oops that's C170.....not a Hercules lol.

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