The International Cessna^® 170 Association

N9149A wrote:

doug8082a wrote:. The Hatz is designed to have a trim tab, but I plan on installing a Cub trim system.

Doug I don't know if I'd do that. The Cub trim system (jack screw) is considered a week link at least for aerobatics and is one of the first things removed when a Cub is built for serious aerobatics. Thought you might want to know that.

I agree. If your talking about the jack screw system. It is a weak link even if you are not doing aerobatics.

N9149A wrote:

doug8082a wrote:. The Hatz is designed to have a trim tab, but I plan on installing a Cub trim system.

Doug I don't know if I'd do that. The Cub trim system (jack screw) is considered a week link at least for aerobatics and is one of the first things removed when a Cub is built for serious aerobatics. Thought you might want to know that.

I agree. When I changed my A65 engine out for a C90, I found there's never enough nose-down trim with the stock system.

As you get into more powerful engines and other mods, it gets worse. Super Cubs have even bigger engines, plus flaps. A mechanic I know well believes this was the cause of a fatal PA18 accident locally: Cub driver executes a go-around, and stalls when the flaps are raised. Trim was found fully nose-up in the wreckage. Mechanic thinks the pilot might have saved the situation by reducing power and putting the flaps down again, long enough to retrim. As it was, the elevators apparently didn't have enough oomph to overcome the nose-up trim.

If the design calls for a tab, I'd want to stick with it!

Best Regards,

John

so....not a single cub or L4 had wooden ribs?!
i didn't know that!
i've spent too much time on wwii jeeps!
well...i'll go with the metal ribs then.
i'll have to see how many i can salvage off these wings!
thanks
dave

a couple of dumb Q's

what does TSO'd and FAA/PMA'd mean?
dave

PMA is parts manufacturer approval:

http://www.faa.gov/aircraft/air_cert/de ... ovals/pma/

TSO is technical standard order:

http://www.faa.gov/aircraft/air_cert/de ... ovals/tso/

I'm looking forward to following along with your project ... once the RV-8 is done I'd like to find an old classic in a barn somewhere (cub, c-170) and put her back together....

T.

thanks T.
i take it that
a standard category plane
must have these type of parts
to be correctly certified?
dave

Hmmm ... now I better defer to the experts.
I am pretty sure that a certified plane must have certified parts (PMA / TSO / etc.) but I don't know all the specifics. There are certain situations where you can have owner manufactured parts that are signed off ... I'm sure there are others who can expand on this much more...
I'm just a doc like you - trying to absorb as much info about these planes as I can!

Thomas

If you have a standard category airplane it must be repaired using approved parts. The parts can be genuine manufacturer parts (i.e. Cessna) or approved after-market parts (i.e. FAA-PMA) or they must comply with some other basis of approval (i.e. owner-produced, ... or in accordance with a properly installed/approved STC, etc.)

TSO is a standard which is intended to guarantee (insofar as such guarantees are possible) that equipment will not interfere with other equipment installed on the airplane, and will perform in accordance with certain performance standards. It is not required that equipment installed on Part 91 aircraft in non-commercial service be TSO'd, unless otherwise indicated by approval basis. (you can install a non-TSO'd comm radio in your C-170. However, If you have an autopilot that navigates on a certain nav radio, the autopilot STC might require the nav radio meet certain TSO's.)
Another requirement for TSO might be regulatory...such as your ELT must meet TSO. Your seatbelt must meet TSO. (But not the shoulder harness in your airplane if your airplane was originally certificated without a shoulder harness and is not otherwise required to have a shoulder harness.)

Now....isn't that a lot clearer?

Dave

Like I said no Pipers of ANY model every had wood ribs. If yours has any it's either not legal or not a real Piper.

Ribs are know available from several sources that are PMA's and STC's to be used as replacements. There are pros and cons to the construction of each of these ribs. If it where my wings and I was rebuilding them to the level that I was removing all the ribs and I found that say half of them where damaged, I'd probably replace them all so they all match. Also ribs are very easily repaired so don't trash them to quickly.

Dave I can not stress enough that the most important thing you can do is take your time doing research talking to people about these aircraft. You need to find several people who have been there and done that.

They are simple and it is easy to start making your own modifications that seem to make sense. Some do and in the big picture lots don't. It would be a shame to rebuild the machine to find you missed an easy mod that improves a weak point or worse created one.

There are lots of parts most but not all are PMA'd today. PMA's DON"T necessarily make the parts good either. There is a major manufacturer of parts that are PMA'd yet they have a reputation to not fit just right. How can this be if the are PMA'd.

You will find that while Cubs and many other machines of the time where made the same they where still made by hand one at a time and they each are unique. Many parts in fact I might say nearly all the parts other than engine parts and prop will most likely need some adjustment to fit them to your aircraft. The trick is finding the parts that are the closest to start with.

Also unlike our Cessnas, nearly everything in the Cub other than the engine and prop is standard AN hardware, easily produced by craftsman locally and used under the owner produced part criteria or approved as a standard technique or practice under 43.13. And then dare I say there are a few parts you might find on the back shelves of your local hardware store which is where Piper acquired them originally in 1939. Shellac, tire tape and Leukenheimer (sp) fuel shut off valves come to mind.

many thanks for all this great advise
i'll keep you all updated,
and try not to pester you too much
and talk about 170's more
dave

Dave

Just noted your signature having ZL-4B. The Z in front doesn't ring a bell. Is it a typo?

Also the USAF wasn't formed till Sept 1947 so your L-4B was part of the USAAF. Unless of course your saying it served with the USAF after 1947.

Just wondering.

hi bruce
i wondered about this?
USAAF looks right.
also, the Z was obviously stamped later
and didn't know if this was done after
it was accepted into the USAAF.
the letter from the USAF to the CAP
on donation after the war refers to it as ZL-4B also.
i asked the people on the cub forum,
and said s.t. about a recall????
here is the data plate.
dave

Here are the fuselage differences BTW the J3 and the L4
does anyone have any pictures to illustrate this?
thanks
dave

1. GREENHOUSE enclosure. Tale tale fabric bulges

2. Observer's desk.

3. Fuselage Serial Number.
8278 to 14033 inclusive.

4. Rear seat.
2 cross tubes bolted to tabs welded to fuselage vertical
members. Seat has Al formers for parachute.
J3 has 1 cross tube for back and 1 under the seat.

5. Seat belt rings welded to fuselage 2 on each side

6. Seat belt security. were bolted to primary fuselage structure
not fastened to a metal loop.

7. Floor boards at rear. Al tunnel over control cables.

8. Observer's desk welded to fuselage

9. Fuselage mod for rear facing observer seat.

10. floating instrument panel

11. cups for leveling plane in flight.

Dave I don't have pictures but of course have seen most of it. Not sure what you are getting at with the window framing for the greenhouse unless you are trying to identify that you have an L-4 because it's there. Some L-4s have had the windows removed and fabric just stretched over the old framing.

Number 11 the leveling cups I'll try to describe. If you where sitting in the back seat on the left side of the aircraft there is a longeron which is the bottom of the window and just above the throttles. There will/should be two pieces of about 3/8" OD tube about 3/8" high welded to the tube. These cups are where you set a level when leveling the fuselage for rigging or W&B.

i had asked about the L-4B's
plate having a 'Z' in front of it,
and no one seemed to know what it meant.
some thought it was a misprint.
here is the front page of the erection manual
that clearly shows this designation.
dave