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Supercub questions

kcabpilot

kcabpilot

Registered User
I'm looking at a local Supercub for sale and have a few questions concerning it's history and status. I'm an A&P/IA so I don't have any concerns about determining it's condition or legality, just about what differences there may be and how that might affect value.

It was originally a 1957 PA18-90 and has gone through three engine changes - an O-200, an O-290 and finally an O-320. No GW increase. Going through the logs one thing I noticed was that the horizontal stab was replaced when it got the O-290. What other airframe differences are there between the 90 and the 150? Would it be eligible for a GW increase? Is there any reason I would not want this airplane just based on that?

I've probably got more questions but that's all I can think of right now
 
If you are not super cub savvy, you might want to hire a cub guy for a few hours to help you through it.

There is at least one tube in the back that needs added I believe.

Also, lots of mods get done/don't get done in these birds. Unless you really know, you won't know.

Many threads on the changes and modifications. Some info is in the member areas also.

Flaps is a big difference though, 90 hp were without...
 
This one has flaps, owner says it always did. Maybe they were an option? I copied the logs and a whole stack of 337's lots of STC's done but I didn't see anything about adding flaps. I can sift through most of it, mainly just wondering what airframe differences there were between the 18 and the 18-150.
 
We have a couple here that were converted. Fewer wing ribs on the 90, and there is an AD on the longerons - an acid test for 4130. I would look for documentation on the flaps - if original, they should show up on the equipment list?
 
There are three 3/8" tubes at the stock battery box location that up the gross from 1500 lbs to 1750 along with balanced Super Cub tail feathers, hydrosorb bungees and horse power increase. A 1957 PA18-95 should have those tubes. 90 hp Super Cubs never had flaps from the factory. Looks like you have several red flags.
 
Yea I'm trying to educate myself on these and this is one of the areas I'm not real clear on - i.e. what is a PA18-95? The TCDS lists PA18 with a C90, PA18-105 with an O-235, a -125 and a -135 with O-290's and the -150 with O-320 but there is no listing for a -90 or -95, just PA18. Maybe the C90 is sometimes called a -95 because of that 5 minute take-off/climb allowance? There are four airframe logbooks that I'm still going through and many of the handwritten entries are a challenge, which is typical, but so far it looks like the tail feathers were changed when the O-290 was installed but I see nothing about flaps. Also seems as though it had both wing tanks from the beginning.

I've just started to seriously look for a Supercub and this one is very close so it gives me an opportunity to take a good look at it and get myself up to speed. There is a ton of info scattered here and other places so I've been doing a lot of reading but with the modern internet you just have to be wary that maybe 60% of what you find might just be flat out wrong :roll:

Anyway, any tips, advice or info is appreciated and thanks for the responses.

Paul
 
Look for a logbook entry regarding installed flaps per Piper drawing #, I think that's how they did over time.
 
I had photocopied all of the logbooks and spent some time going through them today. It's got an interesting history, has had about half a dozen different engines over the years. The airframe has 15,000 hours on it so it's been around. The tail feathers were replaced when an O-290-D was installed in 1990 and it was completely recovered in 2001 with Stits. It looks pretty decent but unfortunately things start to fall apart around that time because there is no logbook entry nor 337 for the O-320 install. The only record is an entry in the engine logbook saying that it was installed on this aircraft. The engine came from a '56 Tri-Pacer.

Maybe it could all be straightened out but I'm not looking for that kind of a challenge right now. I'm just going to keep searching. Too bad because it's so close and he's not asking that much for it.
 
Yeah, there's a few of those flying around! You're an IA, you could straighten it out. You would have to get the piper drawing for the flap install (someone here has them) and make sure the flap install is I.A.W. The engine, just buy the STC paper work, Cub Crafters I think is one.
 
That's true, I just looked at it yesterday so I'm still absorbing it all. It does have a number of pluses. Seventy one years of history is a lot to pour over.
 
mike mcs repair said:
It’s just paper work. Pay attention to the plane, not the paper work.
Click to expand...

In this case yes-- a pretty standard upgrade.
But some mods are diffecult or even impossible to "paper in" after the fact,
if they're not approved mods or if the mod was not done in the approved manner.
 
From previous experience if there are one or two red flags there are more.

According to the FAA and the lawyers airplanes fly because of paperwork. All good till you are across the table from them and all is on record
 
Well that was why I was here asking. Like I said I'm an A&P and the plane is less than 20 miles from my house so I can check out all the red flags and determine if they are surmountable. I just need some information.
 
One of the issues you will have, is that many people, especially in the FAA are not used to dealing with old TCDS. If you take a look at the TCDS under PA-18-150 section, you will see a line that says S/N's eligible. That means exactly what it says. If your S/N falls in that range, it is eligible to be converted to the 150 by using the data referenced in the TCDS. It's already been established that the later 90 hp Cubs had the flap provisions in the fuselage. I don't have one in front of me but there's a good possibility that the gross weight tubing is also in there.
I could go on about this subject but I'll leave it there for now.

Sent from my E6810 using Tapatalk
 
kcabpilot said:
Yea I'm trying to educate myself on these and this is one of the areas I'm not real clear on - i.e. what is a PA18-95? The TCDS lists PA18 with a C90, PA18-105 with an O-235, a -125 and a -135 with O-290's and the -150 with O-320 but there is no listing for a -90 or -95, just PA18. Maybe the C90 is sometimes called a -95 because of that 5 minute take-off/climb allowance?
Click to expand...

Paul,

It's my understanding that Piper never actually used the "PA-18-95" designation on any official paperwork. The data plate and the type certificate list "PA-18" for the 90 horsepower version of the airplane. Also, Piper never certified the airplane for the 95 horsepower takeoff limit. The RPM limit for all operations is 2475, which is 90 horsepower on the C-90. So the "-95" model designation is incorrect anyway.

Now, having said that, some of Piper's "owner's manuals" do use the "PA-18-95" model designation, even though the official paperwork and type certificate do not. The airplane is limited to 90 horsepower by certification, but they call it the "-95" anyway on many non-official documents. They caused their own confusion. The airplane is officially a "PA-18" with no dash number.

And as Steve mentioned, non of the 90 hp PA-18s had flaps from the factory. I own a 1960 model, which is one of the last of the breed (they build a few in '61) and it has no flaps and no balanced elevators.
 
PA 18 95 model appears all over in the Piper Supercub parts manual, may be where it comes from.

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jnorris said:
…. some of Piper's "owner's manuals" do use the "PA-18-95" model designation, even though the official paperwork and type certificate do not. The airplane is limited to 90 horsepower by certification, but they call it the "-95" anyway on many non-official documents. They caused their own confusion.....
Click to expand...

Kind of like the W&B.
Piper likes the wing leading edge (WLE) as a datum,
but with some models I believe they also used a "point in space" datum in some situations.
Consistency would cut down on the confusion.
 
Yea I’ve gone over the TCDS, it’s an eligible S/N with all of the required equipment outside of the fact that he’s got 8.50’s on it. Regardless, there should still at least have been a 337 filed, unless I missed it.
 
I would get the factory pull slip (work order) and make sure the airframe serial number(s) matches. That is not the same as the data plate. Do this before you put any money into it. You could end up with a real can of worms, if, someone has changed parts or all of the airframe.
 
kcabpilot said:
Yea I’ve gone over the TCDS, it’s an eligible S/N with all of the required equipment outside of the fact that he’s got 8.50’s on it. Regardless, there should still at least have been a 337 filed, unless I missed it.
Click to expand...
Some old timers maintained that if you were switching parts per the TCDS it wasn't a major alteration. Only a logbooks entry was needed.

I've never bought into that theory.

At the least you would need a change of weight and balance and flight manual.

Sent from my E6810 using Tapatalk
 
S2D said:
Some old timers maintained that if you were switching parts per the TCDS it wasn't a major alteration. Only a logbooks entry was needed.

I've never bought into that theory.

At the least you would need a change of weight and balance and flight manual.
Click to expand...
You young wippersnapers need to listen up! :lol:

14 C.F.R. §1.1 (1962)
by Federal Aviation Administration

Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications— (1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or (2) That is not done according to accepted practices or cannot be done by elementary operations.

And “minor alteration means an alteration other than a major alteration.”

Therefor since a 337 is only required for Major repairs and alterations, only a logbook entry is needed. Weight and balance would need to be revised and a flight manual would need to be included if it was called out in the T.C..
 
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skywagon8a said:
You young wippersnapers need to listen up! :lol:

14 C.F.R. §1.1 (1962)
by Federal Aviation Administration

Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications— (1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or (2) That is not done according to accepted practices or cannot be done by elementary operations.

And “minor alteration means an alteration other than a major alteration.”

Therefor since a 337 is only required for Major repairs and alterations, only a logbook entry is needed. Weight and balance would need to be revised and a flight manual would need to be included if it was called out in the T.C..
Click to expand...

Do you believe you would need a 337 for the 8.50 tires?
 
Steve Pierce said:
Do you believe you would need a 337 for the 8.50 tires?
Click to expand...
Good question Steve, "Do I believe?" No. I would have to research what the FAA believes. Since 8:00 tires are approved in the TC I would follow:
" That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness"
Key word appreciably.
 
skywagon8a said:
You young wippersnapers need to listen up! [emoji38]

14 C.F.R. §1.1 (1962)
by Federal Aviation Administration

Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications— (1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or (2) That is not done according to accepted practices or cannot be done by elementary operations.

And “minor alteration means an alteration other than a major alteration.”

Therefor since a 337 is only required for Major repairs and alterations, only a logbook entry is needed. Weight and balance would need to be revised and a flight manual would need to be included if it was called out in the T.C..
Click to expand...

Thanks skywagon. Learn something new every day. Don't know why I've always missed that first sentence. !!!!!!!

Sent from my E6810 using Tapatalk
 
Right, I'm an oldtimer A&P who understands the scope of "major" alterations and I see all sorts of examples where people just basically treat any alteration or repair as major. I think it's just a CYA mentality. This is why we have STC's for silly things like Rosen sun visors and such because eventually some dufus is going to come along and claim you can't clamp a visor onto the tube because it's not in the type certificate. So a 337 pretty much shuts them up.

In this case however there is not even a logbook entry, at least not in the airframe log. The only entry is in the transferred engine logs which just says that this engine was installed on this airframe. Maybe that's okay, I mean there is a record at least. Better than nothing at all I guess but what about a W&B? What's the difference between an O-290 and a 320?
 
Last edited:
You remember that a logbooks entry only has to be kept for one year. So that still doesn't make it illegal.

Sent from my E6810 using Tapatalk
 
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