Scary thought
 

I've convinced myself that the best twin airframe ever designed is the P337. So, because I'm not impressed with any of the new single-engined composite models rolling off the assembly line, I've decided to search for a reasonably low time P337 airframe and refurbish the aircraft. On paper, the cost of that project seems roughly equal to the cost of, say, a Cirrus SR22. Plus, it'll keep me busy.

So, I shared my excitement with my wife. And she looked at me and said...

"Honey, when that rear prop breaks loose, what happens to that nice twin tail boom?"

I was shocked by her question, mostly because I had never thought of that. So, I've got to ask this question...

Has that ever happened?

Tail boom strick
 

If you had gone to the OKC fly-in you would have seen a boom that had a tail strick in Don's hanger. It almost cut one of the booms in two, but the plane made to to a save landing. Don can give you more detail.
Fred N358

scary
 

Fred, First of all the only time I ever heard of a prop cutting one of the booms is when I saw the boom in Don's hangar. If I recall correctly it was from a military 02 Skymaster...not sure though.
Can a prop come off an aircraft? Sure it can but the fact is, it is a very rare thing and a lot of things have to go wrong for it to happen. Perhaps an equal question is.

If a prop comes off a single engine plane, it is going to ruin your day. Like wise, if a prop comes off a conventional twin, that too will ruin your day. Since the chances are so small of that type of an event, if that's what you have to worry about, one should not leave the house, however I will answer the question in another way.

If you look at the free space below and on top of both booms, even if a prop were to leave the hub, the chances of a boom strike are really really small. The boom strike that Don has in his hangar was not a full strike but instead a partial hit on the bottom side of the boom. Hope this helps you out.

Jerry
N34EC

scary thought
 

Edrapp, If you want to e-mail or call me I can give you all the details about the aircraft I have that had the boom strike. Yes it was an 0-2A, but the good thing is that Cessna built a very strong aircraft in the 337/0-2. More than 50% of the boom was torn away. The structure of the 0-2A boom is exactly the same as the boom structure in all 337 aircraft. Also, I have a pressurized 337 for sale.
Don Nieser
405-722-4079
nieser.02.337parts@juno.com

Here's a picture of that boom. You can see about half of it is gone, but as everyone has pointed out, the plane landed safely

Rear Prop
 

Get in touch with Don Nieser at Commodore in OKC, he can tell you some stories on this subject. We have a tail boom from an O2 that was hit by a prop. There are many stories on line about battle damage on the O2 during Vietnam. The O2 can take a direct hit from 37mm flak and still make it back to base. If you would like to see a picture of the type of damage that may happen, just let me know. We at Commodore can also help with all your part needs/maintenance.

Ed,

The chances of a 'boom-strike' by a thrown prop blade are so infinitely small as to not even register. There are MANY other things to be concerned with... and probably the greatest concern of the worst of all is in high density traffic areas. You have more of a chance of a mid-air with a low-wing aircraft than ever being exposed to a prop-strike.

BTW we fly a P-model... and wouldn't think of owning or flying ANY other type of aircraft.

As you ponder which Skymaster to call your own, remember, the 337 series went through R&D as a military creation in the first place so as to withstand combat sensitive operations and come back home safely. Having said that, the rest of the risk is a pilot attitude thing... which flying is!

Remember also, the Skymaster is a high-performace airplane... and it WILL get ahead of you if you're not ready for it. So my advice is to first master high-performance single engine flying first before you take on the challenge of the Skymaster.

Fly safe.

SkyKing

Ed:

I agree with the thrust of Skyking messages, namely that a prop hitting a boom pales when compared to other risks (like traffic and weather), that the Skymaster is built like a tank, and that it is a high-performance aircraft which requires attention.

That said, let me disagree on two points. First, the aircraft was designed for the general aviation market, not as a military aircraft. The history of the Skymaster -- which you can link to from my "backup" website at www.SkymasterUS.com -- clearly indicates that the Army expressed interest in the aircraft after production of the 337 had begun. Some special mods were then incorporated in the military O2A (like foam in the fuel tanks and larger cowl flaps). It's possible that lessons learned in Vietnam may have led to some refinements in the later versions (like the 337G and beyond), but I've never read this. Second, if your instruction and experience was on a high wing aircraft (mine was on a Cessna 182), then you might find (as I did) that the transition is an easy one, with the help, of course, of a Skymaster-savvy instructor.

Ernie

The same Skymaster history is available as a link on the home page of this site, on the left edge of the page. "336/337 History". Or just click here. This link is actually a link to Skyrocket LLC's site, and we thank them for letting us do so.

Kevin

I read of one case where a 337 lost the rear prop. The airplane, if I recall correctly, was a turboprop conversion undergoing flight testing. The rear engine acted up, and the pilot shut it down. The aircraft returned to base safely on the front engine. The pilot didn't know that the rear prop had parted company with the airplane until he got out and looked. It apparently missed the tailbooms completely and there was no damage to the airframe.

I will admit to being a little worried about this as well. I think the booms may be "failsafe" in the sense that a single tail boom could support all normal flight loads. The problem comes from the fact that the prop would tend to sever a boom near the point where it attaches to the wing, as evidenced by the photos. Now, in flight, you have nearly the entire length of the severed boom, still attached at the stabalizer, gyrating wildly in the slipstream. This will impart all sorts of twisting moments to the horizontal stabalizer. Yikes! I guess if it did happen (assuming the failure of the horizontal tail was not immediate) the best course of action would be to slow way down, just over the stall speed, plan to put it down whever you are, and pray.

Of course, some conventional twins have even worse layouts. I used to fly and Aero Commander 500. It was an older airplane without the club seating (all three rows faced forward. Many a middle row passenger would involuntarily tuck their feet in under the seat when the engines cranked up. Loss of a prop, or a single blade on a Commander, Aerostar, MU2 etc could really ruin someone's day.

All this being said, it's not a major concern. I wouldn't base a buying decision on this point. All in all, the 337 is an excellent airplane.

Note to site admin: I used to post to this site as "Hardball." I've been inactive for a few months. Apparently, the site ate my user id/password (again). My email to you bounced. So, I gave up and registered again.

Regards,
Jim

Don't forget the elevator rudder and trim cables also go through the booms.

Good point! I presume they are all routed through only one boom. Is that correct?

Regards,
Jim

Since I am a serious worry wart about things like this, I've done a little thinking on it too.

First, chances of this are smaller than Bill Gates calling you up and giving you Microsoft for free.

Second, if this does happen and the boom stays intact but the cables are lost, you still will be able to control pitch with power.

Third, these babies are Mack trucks. Tanks in the sky. Have you seen some of the damage these things took in Vietnam? Huge chunks gone and they still made it back to the field.

comments
 

To EDRAPP, Now that you heard some of the comments to your initial listing, what do you think? Is the Skymaster the plane for you?

Cheers
Jerry
N34EC