I'd go on the Apache FB Group. Tons of info ...and this is BeechTalk...

I am curious what a flight manual supplement for the nacelle fairings would say if there is one. Please let us know what you find out. The Aztec came with them and they can be fitted to an Apache. Early models made from soft aluminum are best. I have seen the later fiberglass ones chaff all the way through the leading edge skin. If you have fiberglass ones I would advise isolating them some anti chaff material.

I can attest to this- I discovered wear at this location from the fiberglass, some protection here is a must.

I believe that the nacelle fairings reduce vmc by 4 mph, to 72 mph. I used to have a 1956 Apache with them, I am looking for a copy of Supplement 11 to confirm.

From the TCDS:

Item 401-s: DMCR approved Supplement No. 11, dated September 30, 1958, to Airplane Flight Manual, Item 401(m).
Required when Item 611 is installed.

Item 611- Nacelle fairings, Piper P/N 19361 (left) and 19361-1 (right), installed
in accordance with Piper Drawing 17913, Revision BP. Item 401(s)
required for Model PA-23, S/N 23-1 through 23-1163.

I have the inboard aluminum Piper factory fairings installed on N4440P and N4457P. They are not compound curved just flat wrap aluminum with some flanges on the edges for the screw holes but they wrap in a way it makes a sort of intersection fairing.

N4440P did have the aftermarket fiberglass outboard nacelle to wing leading edge fairings but I removed them to not have to unscrew every time the cowl side was removed. The factory inboard fairings can stay installed with cowl removed.

I did not notice any performance changes once the outboard fairings were removed.

The 160hp airplanes were different when they came to the G model. There was a gross weight increase with the 160hp but later Flap and gear extension speed increase were added. 125 to 150mph VLE and 100 to 125 mph VFE.
I think the later airplanes eligible for this can be identified by a fuselage with no diagonal brace in the aft cabin windows. There were earlier 160hp airplanes with the brace but lower gear/ flap extension speeds
S/N 1871 and later is what to look for but they are rare. Especially if planning a bigger engine modification.
S/N 1774 was a stand alone maybe prototype for testing the higher gear and flap speeds?

Glenn thank you for the supportive words. This thread has been very helpful and contains so much useful information in its 24 odd pages. From my research it appears that some of the later 150 planes came with the nacelle fairings just as all the 160 airplanes. The later -150 planes with the fairings installed came with supplement 11 added to the AFM from the factory reducing the Vmc. The 160s came with them and already had the reduced Vmc, with that, SL 307 and 320 offered them as a retrofit for the earlier 150 airplanes.

In other words my airplane is 588 an early plane with the fairings added and a 337 on file referencing the Sl and saying that supplement 11 has been added to the AFM. I unfortunately however don’t physically have it and really needed so I am reaching out to the community

Norman, I am pretty confident that the Flight manual supplement will say that with the installation of these fairings, the Vmc is reduced to 78MPH. And I need it in my possession for the DER to complete the field approval. If and when I get ahold of a copy I will certainly post it.

Norman, I am pretty confident that the Flight manual supplement will say that with the installation of these fairings, the Vmc is reduced to 78MPH. And I need it in my possession for the DER to complete the field approval. If and when I get ahold of a copy I will certainly post it.

As per item 611 of the TCSD, the addition of those fairings ( the two part numbers) reduces the Vmc, someone posted those two lines up above. The 337 in my records that denotes the addition of the two fairings also states that per the AFMS, the VMC is reduced to 78 mph. Now I Just need the actual AFMS

Here is something I have never seen. A Piper Apache manual cowl flap/door fitted to inboard side. It was on a hurricane wind damaged Apache that was previously on the Canadian registry.

I am parting it out and have a pair of low time new style compact hub no AD props and a pair of low time O320B3B 160HP straight mount engines. (Will fit Super Cub and RVs).

Lots of other good parts too.

Also just got offered a rare Apache 235 with low time engines. (Essentially an early Aztec with lower compression derated engines). They are very rare and fly nice. Also can operate on Mogas. If anyone is interested I will pass on the phone #.

the apache 235 CAN operate on mogas but not legally. It showed vapor lock issues in crossfeed and peterson gave up on it.

Even better, you can change the low compression 235 hp pistons for the regular 250 hp pistons and now you've got an early Aztec. Same airframe, better performance.

FWIW, the Peterson tests were ridiculous, because of FAA demands. They had to use winter-spec fuel in the summertime, heated to 110 degrees before flight. Of course you could have vapor issues with that combination. Which could have been solved with a flight manual supplement requiring fresh fuel at all times, no six-month-old winter-blend fuel allowed.

Even better, you can change the low compression 235 hp pistons for the regular 250 hp pistons and now you've got an early Aztec. Same airframe, better performance.

FWIW, the Peterson tests were ridiculous, because of FAA demands. They had to use winter-spec fuel in the summertime, heated to 110 degrees before flight. Of course you could have vapor issues with that combination. Which could have been solved with a flight manual supplement requiring fresh fuel at all times, no six-month-old winter-blend fuel allowed.

I have a 250 hp converted PA23-235. It's a wonderful airplane. The only difference between a 1960-1962 Aztec, and a 1963-1966 Apache 235, are the pistons in the engines, and the flight manual performance charts. Some PA23-235's were converted by using a Nayak STC to swap the engines from the O-540-B1D5 to the O-540-A1D5. Others were done by swapping pistons under 337's. The plane remains a PA23-235 but has the extra performance that 30 HP gives. In addition, the Apache 235's had fewer options so they are often 100 or more pounds lighter.

By the way, if anyone needs the supplement I inquired about above regarding the installation of Nacelle fairings to reduce VMC and what may be necessary to upgrade a 150 to a 160… here is supplement no 11