Official B-29 Doc Restoration Thread

[CAPFlyer]

While I agree that production of R-3350 was enormous, it does not change the fact that it was (is) an unrealible powerplant. Isnt the CAF still having issues with the hybrid? Did that restored DC-7 ever get out of Charlotte after its -3350 expired on takeoff?

I disagree. First, the issue with the EAL DC-7 was a PRT issue, not the engine. While the PRTs were fairly reliable in airline use, like many things with radial engines, they don't like extended periods of not running. Also, the DC-7 is still at CHS and will probably remain there after the crew was unable to obtain funding to repair the engine. This also occurred about the time that the parent company started running into problems due to a loss in work from the continued recession as well that saw them selling several of their other aircraft.

The B-29 engines (both the hybrid and original) do not use PRTs, so this removes them from the equation. Additionally, as was said above - the R3350 is a fairly reliable engine. 1000HRS TBO is about average for current radials (R1830, R2800, R2600) and last I heard, Anderson had said he hoped for 1200-1500HR TBO on the hybrids, which would exceed what you get out of the originals, but as was said before, they've already well surpassed the average TBO from the original engines, so it's more than a smart investment to get the new engines on 'Doc.'

[menards]

The new hybrid engine is very reliable. We have over 500 hours on our engines with very few problems, I think we've had one cylinder change due to a loose spark plug boss. Remember the airlines used this same engine and would put 1,500 to 2,000 hours on before overhaul. One reason for the reliability is we are only using 2,400 rpm for maximum power which reduces wear and tear, we are essentially operating at METO (Maximum Except Take Off) power which can be run all day long. With the lower rpm also brings cooler temperatures. I've operated these engines on a 103 degree day and never saw the CHT (cylinder head temp) exceed 200 degrees C. (232 is max). I keep talking about temperatures. Controlling temperatures are the key to successfully operating a large radial engine.


B29driver, Don Davis, Mike Looney, and Rodney Jackson are the folks who came up with the idea of the hybrid engine. B29driver and Gary Austin, and Dave Miller made it happen.

Lots of good info here...thx.

[menards]

While I agree that production of R-3350 was enormous, it does not change the fact that it was (is) an unrealible powerplant. Isnt the CAF still having issues with the hybrid? Did that restored DC-7 ever get out of Charlotte after its -3350 expired on takeoff?

The B-29 engines (both the hybrid and original) do not use PRTs, so this removes them from the equation. Additionally, as was said above - the R3350 is a fairly reliable engine. 1000HRS TBO is about average for current radials (R1830, R2800, R2600) and last I heard, Anderson had said he hoped for 1200-1500HR TBO on the hybrids, which would exceed what you get out of the originals, but as was said before, they've already well surpassed the average TBO from the original engines, so it's more than a smart investment to get the new engines on 'Doc.'

Coming full circle to the original question, with two flying examples utilizing the -3350 "Hybrid" motor, how many parts are out there to continue to build engines for these two birds? Enough parts for 10 engines? 100 engines? An indefinate supply?

[b29flteng]

To answer Iclo: We combined parts from two different "dash" numbered R-3350 engines to create a "new" hybrid engine that hasn't been certified. There are no custom built parts installed in the engines. Since FIFI is licensed as an experimental aircraft, we were able to accomplish these modifications without the FAA to certify it. The FAA did require us to test fly the aircraft for 25 hours before we were able to fly out on tour or airshows.

[ryguy135]

Ok little update. I have been hit with overtime so my time helping with Doc has almost ceased for the time being. However, the bulk of the structural work is complete with the exception of reinstalling the belly pan so there's not much I feel qualified to assist with now anyway.

Some problems have arisen with the fuel cells not fitting properly. These problems are being worked through however and hopefully will be solved soon.

The rest of the engines are being prepped for installation and have the accessories all attached. Additionally, the cowl has been test fit on the installed engine.




Regarding the discussion about spares - Doc is fortunate enough to have the support of Spirit Aerosystems across the street to assist in building parts when necessary. Spirit helped fabricate a new lower wing spar which was a rather difficult and complex undertaking. WIth the aerospace industry that Wichita has, acquiring replacement parts is more an issue of money rather than availability.

And about the engines, I know the original plan was to acquire two spare hybrid engines in addition to the four to be used. I have not heard otherwise, and with the reliability of these engines, that should be more than enough to keep Doc's propellors turning for years to come.

[CAPFlyer]

Coming full circle to the original question, with two flying examples utilizing the -3350 "Hybrid" motor, how many parts are out there to continue to build engines for these two birds? Enough parts for 10 engines? 100 engines? An indefinate supply?

Somewhere between the 2nd and 3rd option I'd venture. There were several thousand of these motors built (of each type), significant spares for both, and both models are still in active use. While you can't hybridize every one of them, I doubt that spares will be a significant issue for some time to come, even if a 3rd or 4th airplane began to fly the engine as well.

Oh, and don't forget, Rare Bear uses the hybrid engine as well, so there's actually 3 flying aircraft with this engine.

[B-29 Watcher]

Hey Ryguy;
It is good to hear from you, it has been a while. It's too bad you cant get to DOC as much, but it is good you have plenty of work. We appreciate the updates when you can give them.

[Jeremy S]

For those of you who don't use Facebook, here are a few of the photos that they posted on the "Doc's Friends" page today. There are several more so I won't post all of them.

https://www.facebook.com/DocsFriends

Our restoration volunteers mounted engine #4 this past weekend, complete with the new exhaust system. Our team expects to receive the exhaust systems for the remaining three engines over the next three weeks.

[maxum96]

Thanks for the pics Jeremy. The exhaust collector is a work of art. Wish I was that good with a TIG welder.

[menards]

Regarding the discussion about spares - Doc is fortunate enough to have the support of Spirit Aerosystems across the street to assist in building parts when necessary. Spirit helped fabricate a new lower wing spar which was a rather difficult and complex undertaking. WIth the aerospace industry that Wichita has, acquiring replacement parts is more an issue of money rather than availability.

And about the engines, I know the original plan was to acquire two spare hybrid engines in addition to the four to be used. I have not heard otherwise, and with the reliability of these engines, that should be more than enough to keep Doc's propellors turning for years to come.

Hopefully the Friends of Doc have Deep Pockets. Would love to see this bird on the east coast.

[AURktman]

As I said on the Facebook post, Borla ain't got nuttin' on that stainless exhaust!

[B-29 Watcher]

It seems to me that someone in Wichita would have the time to post the progress more than once in a while. The last post on Facebook was on April 7th and in that post they said (and I quote) "Our team expects to receive the exhaust systems for the remaining three engines over the next three weeks.". It has been over two weeks and nothing. I wish Ryguy or Jeremy could post they kept us in the know. I hate not knowing or seeing for such a long time.

[B-29 Watcher]

They Installed the propeller on the #4 engine this weekend. they posted it on facebook today. In the picture you can see the other engine(s) are not hung yet, but it is great to see the progress.

[ryguy135]

The props, cowls, and engines are now permanently hung in the #1 and #4 positions. #2 and #3 should follow in a few weeks. They also have started painting the stars and bars on the fuselage sides.

[Jeremy S]

For those of you who don't use Facebook:

We are one step closer to flight! Our restoration volunteers installed one of Doc's new propellers this weekend.

Source: https://www.facebook.com/DocsFriends