Wing Change?

[Pacer 24C]

I have owned a 56 22/20 and now have a 53 22/20- When did the wing rib spacing actually change and what is the change? I thought it would change with the 150hp - but I have seen 55 models with the older wing?? If you STC a 135 to a 150 - any actual changes required? Any info appreciated thanks

[Tadpole]

From what I understand, none of the STCs to upgrade an engine involve upgrading a wing.

[SuperPacer]

My limited understanding is the "13" rib wing was added to the Tri-Pacer with the addition of the O-320 150 / 160 engine option from the factory. This also increased the VNE and Gross weight. Not really sure what year that happened.

None of the engine upgrade STC's include the engineering to make the wing / Gross weight nor VNE increase(s). I suspect one could use 13 rib wings on older planes and have some "excess capacity" in the bank, so to speak.

I have heard of people modifing 12 rib wings, but that is really not a good idea, as it leaves a large number of rib attach holes in the spar, as the spacing is different. All of the above is speculation, check the drawings for verification.

Enjoy the day,

john

[Steve Pierce]

John and Jason are correct.

[moe2goe]

I'm sure the Type Cert. Data Sheets will show the change from 135 hp to 150 hp by serial number. Pretty sure that would include the change in gross wieght and wing design. BUT , I haven't checked .... Not the case if engine change was done by STC.

[Throttle Pusher]

I dont think the O-320 came out till 56? I think at that point it was a no brainer for Piper to install it on the Tri-pacer.
The first installs of the O-320 were O-320 no A,B etc.. just O-320. These were the first one Lyc. came out with.
I think that piper was waiting, along with other aircraft manufacters to put the O-320 on as soon as it came out.
I'm sure lyc. did a PR for it as well.( before it came out)

Ken

[redbarron55]

My Crosswind STOL STC for the 150 HP installs the O-320 in the original PA-20 witht he 12 rib wing. The Vne does not change and the limitations limit the RPM to limit HP to `125 HP. Since the engine will not ususally pull max RPM in takeoff and the HP is reduced with altitude the limitation is not very limiting.
That being said the O-290D I had with the blue printed cam and D-2 Pistons had better performance only limited by the exhaust valve head that broke off and ate the engine.