Early Mooney M20 prop

[Kevin]

I got a call from a customer last night who bought a 1956 M20. It has an O-320 engine (that's it, an O-320, not an O-320-A3A or any other suffix, just a plain old O-320, no suffix)

 

He's got an old Hartzell steel hub prop, and the prop shop has told him its "shot," so he's looking for another propeller. Unfortunately, his only option is another Hartzell steel hub prop (per the TC). I couldn't find any STC'd prop for this application, and the new Hartzell steel hub prop is quite pricey.

 

It seems to me his best option would be to install an aluminum hub compact Hartzell or McCauley. Has anyone out there gotten a field approval to install an alternate prop on an old M20?

[Alan Fox]

Look up the TCDS on FAA.GOV , if its not applicable , Call Lasar , they probably can help.... On my B model , it came with a McCauley , but the TCDS allowed a Hartzell    good luck...

[Kevin]

Your "B" model has a 360. The 320 will take a Hartzell, but the Hartzell it allows is more expensive than the plane!

[Alan Fox]

Did you look up STCs on FAA.GOV ??  Maybe some relief there...

[Skybrd]

I know of a old Mooney that's been sitting for years. I think it's a 1958 or 57 Mooney and know it has a 150 hp engine. Anyway the owner is Danny Marvin and his airplane is in Ridgecrest, Ca. I know he has two homes and think he mostly lives in Tehachapi, Ca. You might try to call him by using the phone book and ask him if you could buy it from him. I doubt if he will ever use the propeller. Good luck.

[Kevin]

Thanks for the tip, Skybrd, I'll call the customer and refer him to this site. I'm afraid, though, that if the plane has been sitting for years that the prop may be as bad as the one he already has.

 

I was really hoping that someone had gotten an STC or field approval for a "modern" prop for this bird, but it's not looking so good . . .

 

It seems like the logical replacement would be a Hartzell aluminum prop, but the TC for the prop doesn't show an approval on a "straight" O-320, so getting a field approval won't be easy, if it ever is.

[jetdriven]

What about a field approval for a constant-speed prop from a Twin Comanche? It had IO-320B1A's and there is a Hartzell Top Prop (HC-E2YL-2B) approved for that engine.  The straight O-320 is a very similar engine with the 7.00:1 C/R and all.

[Kevin]

The Twinkie prop is feathering. No need to put it on - extra weight & complexity, but there are plenty of similar non-feathering props that could be installed if someone had a previous approval. Getting an approval nowdays is almost imposible.

[jetdriven]

Oops, my oversight.  I have heard the Ft. Worth FSDO is pretty accomodating in regards to approvals.  Another way is to find someone else who has put a different prop on a M20A and copy them. Perhaps Hartzell has some information?

[Kevin]

Hartzell does not have any info other than the approved propeller - Hartzell is aware of no STC's for an alternate propeller on this aircraft.

[kerry]

Because of the age of the plane I would say a 337 would be your best option. I hear field approval is much easier on older aircraft. I would contact FSDO and start asking questions. Is the flange the same as a O360. If so I'd think field approval would even be easier with 30 less hp.

[Kevin]

The flange is not the same as on the 360.

 

I'm hoping someone else has already gotten a field approval, then I can direct my costomer to that individual. It's much easier to get a field approval if it has already been approved on another plane of the same type. You can basically walk in to the FSDO and say "I want to do this to my plane as well."

[kerry]

I've heard of it being approved on a piper pacer/tripacer. Read it on Pacer short wing forum. Look up MT light weight or Aeromatic prop. I also believe the O320 w/no suffix is consider the same as a O320 A1A. There is a Mooney wood wing group that has a forum. Dave Morris runs it. You could ask there and find some info.

[jetdriven]

Many prop shops never saw a prop that didnt need overhauled.  San Antonio Propeller is not like that.  I got a strip, reseal and paint for 500$.

[carusoam]

Jim,

 

Interesting Yahoo group.  I always wondered where the wooden ones were hanging out.  Just assumed the numbers had dwindled before the internet was born.

 

Glad they have support.

 

Best regards,

 

-a-

[Cody Stallings]

Wonder how many M20A are out there flying?........ There are no other props that fit that plane, cause of the crank flange... Can find one that fits an do a 337, that's not cool at all.

[kerry]

Wonder how many M20A are out there flying?........ There are no other props that fit that plane, cause of the crank flange... Can find one that fits an do a 337, that's not cool at all.

My guess would be around 200 M20A's that are airworthy.  The M20A has 180 hp O-360.  The earlier wood wing had the 150 hp O-320 and was designanted as a M20.  I've heard the 150 hp is a great engine set up for the airframe.  Less fuel and nearly as fast as the M20A.  I didn't realize there were issues with the prop.  Too bad.

[Cody Stallings]

Sorry about that, guess I'm not up to speed on the mooney models..... I knew there was one with the o-320 though...

[carusoam]

It's definitely worth a visit to the web site that was pointed out earlier above here regarding the early Mooneys...

-a-

[Cody Stallings]

I must agree, very informative. Lookin at those old pics make me wish I was around back then, aviation was different, there were muscle cars, leaded gas, an nobody was screaming about going green...

[kerry]

I came across a lycoming service letter. SI-1435, converting a constant speed prop to a fixed prop. Maybe this could be an option.

[dcrogers11]

Bynum Props in Ft. Worth does my eddy current.  Might be worth a call, altough previous post on prop shops is usually pretty accurate.  God bless this guy for working to revive this old bird.  Has he had the wooded wings looked at?  Also Air Salvave guys at Lancaster field near Dallas are also pretty helpful as well as Don Maxwell's shop.