Hatz Biplane Association

It is my understanding the test flight program is affected by which engine-propeller combination is installed. With a certified engine-propeller combination the test program is 25hrs and with an experimental combination 40hrs. I searched the Classic forum for information about engines-propeller combinations builders are using with little return. So, I looked at the TCDS for my O-320-E2D and did not find anything specific regarding an approved engine/prop combination. Next I checked the Cessna 172 TCDS, because that is where the engine came from, which does have approved propeller specifications for the E2D. There listed were several McCauley part numbers that are approved. Out of curiosity (this is an educational endeavor) I searched the web for refurbished McCauleys and found a place in Ohio that had two props with the correct part numbers. They are also a McCauley distributor. When I inquired about the props I received a message asking what size spacer did I need. Whoa! Spacer? I was also informed that McCauley does not sell a prop for the E2D without a spacer.

So for the forum, what are the engine prop combinations being used and do any of these installations require or are using a spacer? I have a beautiful Sensenich wooden propeller designed for an O-320 150HP which I intend on using but am a little concerned I may be missing something regarding its installation. My plan was to mount the prop directly ahead of the starter gear support assembly with a crush plate. No spacer, as there is no interference between the nose cowl and the spinner rear bulkhead. Am I wrong?

http://www.sabermfg.com/extensions.htm

Check out the above link. I have been told that with a wood prop - you need a spacer between the hub and the prop and a crush plate on the front. I used a 3/8" spacer and a 3/8" crush plate. Worked fine.

Michael
N838MM

Hi Ebby,
I believe, as you have found, that all Cessna 172's that had the E2D engine have a prop spacer. Since you have the wood Sensenich prop, why not just use it? The only wood prop certified on an O-320 is the Sensenich W80-?, which is STC'ed for the Super Cub/O-320. I'm flying my Hatz, O-320-A1B, with a Sensenich wood W74FM7-54. The wood prop saves about 15 pounds, runs very smooth and will save the crank if I ever have a prop strike (hope not). The Piper PA-14 with E2D used a McCauley without a spacer, Citabria's with O-320's also, not sure if they are E2D's. Most O-320 use a Sensenich metal 74DM-50 through 61, like Cherokees, Tri-Pacers and Super Cubs. Your DAR will be the final say if it will be 25 or 40 hours. You may find more McCauley info at http://www.mccauley.trexton.com, they have a lot of airframe/engine/prop info. Good luck. Herb, CB-1, SN-400, based 2NK9, Modena,NY

Hi Ebby,
I will be using a wood prop (Sterba) and found I need a small spacer to get the proper clearance of my spinner to the nosebowl.
Al

I contacted Sabre Mfg. and Sensenich and confirmed the current set-up I have for engine and prop will be fine. I look forward to using the wooden prop as I have heard from several sources they run smooth, limit vibration and are forgiving (to the engine) in the event of a prop strike. Pretty interesting investigation non-the-less.

What is the proper spacing? I'm currently running a Sensenich wood prop (that will need replaced soon) on an O-320 and it seems extremely close to the cowling.

Also, are the Sterba props pretty good? Are there other lower cost wood props that are being used? I'm OK with the Sensenich's performance, but if I am going to replace it anyway, I'd rather not pay the "certified" price if there is an experimental alternative that is just as good.

Following Saber's green light with what I have, I will mount the prop directly on the flange and use a 1/2" crush plate.