B-29 reset

[GrauGeist]

The mission here men, is how to help the WWII effort. How can we get the aircraft fielded sooner and improve the early performance?

You couldn't...there was just too much to be worked out. So much so, that the military started looking at alternatives in case it didn't work out.
The XB-19 program was in the works and first flew in '41. It had used both the Allison V-3420 and the Wright R-3350 engines.
The XB-39 was an Allison engined B-29 alternative and actually proved to be faster and higher flying than the Radial powered B-29. The problem here, is that it would be late to the game unless they had designed the B-29 with Allison V-3420-17 from the beginning. The V-3420-17 was available well before the U.S. got involved in the war and could have easily been incorporated into the design.
And of course, there was the B-32 project that started shortly after the B-29 began development. But it also called for R-3350s, so we're back to square "A".

One suggestion was a different engine.

The P&W R-4360 Wasp Major was initially rated at 3,000 hp...but it was in development until '44. Until then, the R-2600 was a close competitor. There's other Radials available, but you need to horsepower to get this monster in the air under load and then move it a great distance.

Another suggestion was two more engines.

You can't just hang extra engines on something without extensive rework. Alot of consideration has to be taken for engine placement and support. You also need to add extra fuel tanks to feed those two new engines. and the list goes on.
Probably plenty of room for the additional oil tanks, though.

Another suggestion was improving development of the historical engine.

They were working on the R-3350 as best as they could, especially with the military breathing down their neck. (imagine: "are we there yet? Are we there yet? Are we there yet?")

 

[GregP]

If that was s simple question, please think about them going forward. When someone says it's accelerating and you asked if they weren't really backing off to avoid death, it comes across as very sarcastic. Since I have done that very thing in the past unintentionally (everyone laugh here ...), let's move on.

The B-29 performed VERY well. Here is a pic of the XB-39, basically a B-29 with the Allison V-3420 as the powerplant.

If you want to start improvement, why not start with the bombers that needed it the most? The B-17 and B-24 could have been improved, too. They DID try a B-17 with Allisons, the XB-38 ... it was the fastest B-17 on record. Here's a pic:

They didn't elect to produce it or even continue with tests, for some reason.

Here's a B-24 with a B-17 nose section grafted on:

They didn't proceed with that either, though it certainly LOOKED better than a standard B-24. I haven't seen a B-24 with alternate powerplants or an alternate airfoil, both of which it could have used. The PB4Y-2 was a single tail version, without other improvement and the side turrets were ludicrous. Other than the planes already mentioned (B-17, B-24, B-29, B-38, B-39) I can't think of any US heavy prototypes that would have helped out.

I like the XB-42 / 43, but it was a medium bomber, as was the "improved" B-25, the North American XB-28. I can't think of anymore heavy bombers we worked on during WWII that made serve in WWII. The XB-35 didn't fly until after the war and was politically killed. The XB-15 and XB-19 were pre-WWII and were not selected for production.

I'm out of candidates, but firmly believe the B-29 was everything it needed to be, albeit a few years late due to the R-3350 that was neglected for 5 years by Wright. If they had not done that, the B-29 would have been a very major player in the war. But they HAD their chance with the V-3420 version and turned it down, probably over drinks at a golf course by people who weren't really familiar with the Allison, but who were in a position to shoot it down yet again despite very promising test results.

Politics was and IS alive and well, even today. Think of the disaster called the F-35. Why in hell we are still throwing money at it I'll never know, but we are. If you can't successfully make it combat worthy with a run of 100+ aircraft. I suggest you cut your losses and move on. But we certainly aren't, are we? And if you can't develop it in 25 years, you don't need it.

 

[FLYBOYJ]

Politics was and IS alive and well, even today. Think of the disaster called the F-35. Why in hell we are still throwing money at it I'll never know, but we are. If you can't successfully make it combat worthy with a run of 100+ aircraft. I suggest you cut your losses and move on. But we certainly aren't, are we? And if you can't develop it in 25 years, you don't need it.

Greg, once again you make unwarranted and unsubstantiated attacks on the F-35 while it's still under development. Earlier in this thread you didn't appreciate the comment of gjs, now I'm calling BS on this as you're crossing the political line here and really clouding this thread. I don't want to shut this thread down so I suggest sticking to topic and keeping F-35 discussions to specific threads where you could show actual proof of it's downfall or success. As you said earlier "please don't troll for an argument," I hope I'm clear on this!!!!

 

[Shortround6]

In a lot of cases timing is everything. The B-19 taught Douglas ( and by extension, the US aero industry, The Government paid for the design data and shared it) a lot about large aircraft structures and other problems but it took so long to complete that it was out of date when it first flew. Contracts for the B-35 and B-36 being issued before the B-19 first flew. With R-3350 engines it had a top speed of 224mph. While it had range and bomb load it didn't have enough performance to hope to survive in hostile skys.

In order to get the numbers of bombers desired ( and the engines to power them) decisions had to made on which designs to mass produce around two years before squadron service. Design work started on the B-24 in 1938. Early versions with out turbo superchargers failed to meet specified speed. First US combat use of fully combat capable B-24s was in June of 1942 by 13 planes. Mucking about with "improved" aircraft in 1941-42 is going to delay the onset of the bombing campaign by months (or several seasons) minimum. Switching a factory from one bomber type to another (or a substantial modified version) could result in a loss of production of hundreds of air-frames. The US might be able to afford such a loss in 1944 but by then it is almost too late to matter, Loosing that number of air-frames in 1942 or early 1943 is something else. And to be switching production lines in 1942-43 means design work needed to start back in 1940 (4 engine bombers need more time to design than single engine fighters).

 

[pbehn]

The soviet Tu 4 used a Russian development of the Wright R-1820, maybe that would have been an option.

from wiki
The Soviet engine, the Shvetsov ASh-73 was a development of the Wright R-1820 but was not otherwise related to the B-29s Wright R-3350.[

 

[Shortround6]

We have been over this before. the ASh-73 was a development of the R-1820 in the same way that the R-3350 was a development of the R-1820. they were evolved in parallel with the ASh-73 being later in timing, much later. Production did not begin until 1947 FlyboyJ has provided this chart before but here it is again.

Please note that the 18 cylinder engines M-70, M-71 and M-72 were pretty much failures. Trying to substitute a metric 18 cylinder failure for an SAE 18 cylinder failure ( in early versions) isn't going to solve or speed up anything for the US forces.

 

[gjs238]

I'm not suggesting changes during production that would create even more delays.
What I am suggesting are design changes prior to production that we can make with the benefit of hindsight.

At the genesis of the B-29 folks could not have known how extended development of the R-3350 was going to be.
Unless we can come up with a reasonable plan to get the R-3350 ironed out sooner, it seems that perhaps the XB-39 with the Allison V-3420, may have been the best solution.
As Greg pointed out earlier, it was a "low risk" design.

Mass production of the V-3420 in quantity exceeding B-29 demand could have led to other uses of the V-3420, as occurred historically with the R-3350.

Earlier fielding of the B-29 and more reliable early fielding of the B-29 could provide some interesting speculation.
Perhaps the B-29/B-32 would have appeared over Europe.
Perhaps the bombing campaign against Japan would have gone differently.

 

[tomo pauk]

Was the M-71 really a failure?

 

[Balljoint]

They were not backing off to prevent engine fires. Don't be a spokesman for disinformation. The R-3350's had issues but. again, I might remind you the B-29 had the lowest combat loss rate of ANY heavy bomber of WWII. If that's a dangerous engine, I'll fly behind it every time regardless of engines, if given the choice of the B-29 or any other heavy bomber.

If I had to choose one and only one bomber to fly, I'd take Douglas A-26's every time.

Gis238, please don't troll for an argument. If you attend one the talks given by the vets and ask that kind of question, they'll eat you alive and you'll be asked to leave if you do it twice. State your opinion by all means if you can back it up with facts, but it's tough to say something was a death trap when it flew 31,000+ sorties with the lowest loss rate in the USAAF for it's class of aircraft, don't you think?

I think the B-29 was a great machine for its time. However, the engine nacelles were a bit tight and with a poor firewall, engine fires got to the magnesium engine mounts rather directly. Being at or over gross often in the Tinian heat, the 29 had a serious weakness in the way it was operated.

During a conversation with the Wright theater engineer he spoke of an unusual loss rate among the B-29s flying the Hump with cargo. By bumming rides in the jump seat he learned that, apparently from boredom, the pilots were competing to have the lowest fuel consumption. Apparently they were using Lindbergh's P-38 technique which the B-29 didn't forgive.

The plane wasn't bad but it needed careful handling and was a bit marginal when the limits were pushed as often the case at Tinian. Once at altitude and speed and having burned off some fuel it was just another plane,

 

[fastmongrel]

Was the V3420 a low risk design. Almost everyone else who tried doubling up engines had problems when they went from hand made prototypes to line built engines.

 

[GrauGeist]

The soviet Tu 4 used a Russian development of the Wright R-1820, maybe that would have been an option.

The TU-4 was a reverse engineered B-29, so it required the development and deployment by the U.S. before the Russians were able to take interred examples and create the TU-4 and it's native powerplants.

 

[FLYBOYJ]

During a conversation with the Wright theater engineer he spoke of an unusual loss rate among the B-29s flying the Hump with cargo. By bumming rides in the jump seat he learned that, apparently from boredom, the pilots were competing to have the lowest fuel consumption. Apparently they were using Lindbergh's P-38 technique which the B-29 didn't forgive.

Linbergh's procedure called for operating lower RPMs at higher manifold settings, not to exceed what the manufacturer specifies, doing this while you set the mixture to "lean of peak." This wasn't voodo magic and I would guess that the FE's manual had mixture setting procedures that specified this. I would also think that if the pilot was exceeding limits the FE would be punching the crap out of him!

 

[Shortround6]

Linbergh's procedure was pretty much the same as Tony Levier's which means it was pretty much what both Lockheed and Allison recommended for P-38s ( Army instructors didn't ?). It was also pretty much standard for Merlins and most other aircraft engines that had pilot or FE controllable mixture settings.

 

[GregP]

Hi Flyboy,

You are very clear. I didn't think not liking it was political, but I understand you apparently do.

So I'll pipe down about not liking it in here except in F-35 threads.

Is that OK?

 

[Shortround6]

Russians were working on the M-71 engine in 1939 with a few prototypes built in 1939 and a few the following the year, it did NOT pass it's state tests until the fall of 1942 and was only flown in 4 types of prototype aircraft. The I-185 was flying with it in the Spring of 1942 and performance was such that series production was planed. Series production of the I-185 was canceled in mid 1943 due to continued unreliability of the M-71 engine and the need to use the M-82 (the only alternative) in the LA-5.

The M-72 was pretty much a two speed supercharged M-71 and was due to start production in the 3rd quarter of 1945 ( a little late for the B-29) but was superseded by the Ash-73. Please note that ALL these engines were from the same design team. Work started on teh Ash-73 in 1944 but prototypes were not built until 1945/46 with a few engines using some American components. State tests were started in Aug of 1946 but not completed until 1948.

 

[GregP]

Was the V-3420 a low-risk design?

The V-1710 doesn't leak much oil. It weeps a small bit, like any large V-12, but rather less than most other engines. The double DBs tended to leak more because they were inverted V-12's, not upright V-12's. In inverted engines, any potential leaks usually eventually DO leak. More oil leaks lead to more oil in the nacelle or in the V between the two crankcases that is ready to ignite.

I can't say definitely, but the only V-3420 I have ever seen run was absolutely dry after the run. That being said the run was not more than 8 minutes or so, and you might expect that. But it certainly wasn't leaking from anywhere unexpected.

On the Allison, the main sources of oil leaks are a few drops coming from the prop shaft seal, some very small occasional leaks from the tachometer drive, maybe a few leaks from the valve covers,. and maybe a trail or two from where the top and bottom engine cases join. The engine case leaks usually stop after 1 - 3 hours of running, which we do on a test stand. Altogether not much in the way of leaks, usually a few drops and maybe a very small oil trail that wipes off easily after flight.

When Joe Yancey builds his engines, we usually see a few leaks on the first run, wipe them down during cool down and tighten a few things and almost nothing after that ... maybe a few drops. It certainly leaks much less than any radial I have ever tried to wipe down, including a Russian M-14P in a Yak-52. So I THINK it might be a good candidate for the double engine, if ever there was one.

But only time and experience could tell us.

There is no record of the XB-39 having issue with the V-3420, but since the R-3350's were performing well in combat, it also didn't make sense to convert to the V-3420, so they dropped it.

The only real trouble with Allisons in bomber development I know of was the XB-38, which was the Allison-powered B-17. Apparently the Allison V-1710's installed in it had intake leaks and they had to correct that at least once or twice. On the last flight the left inboard engine caught fire and they bailed out. Allisons mostly do not catch fire and the P-38, P-39. and P-40 didn't have issues with that event. So it makes we wonder of they had people working on the XB-38 at Vega who were familiar with the Allison at all. Unfamiliarity opens all sorts of opportunities for problems.

Bringing in Joe Yancey again, when he assembles an engine, the intake seals get a lot of attention. If they are cracked they cannot be used. He has never shipped an Allison with intake leaks, but I have seen one that had a leak and we fixed it. You could tell by the color of the inside of the exhaust pipe that the mixture was different in three cylinders on the left bank, so we easily found the leaking intake seal. The pipes cleaned up and showed the same color as the rest on the next run.

In the end, they elected not to try that alternative, but it was there for the taking if the R-3350 had stumbled enough to warrant it.

 

[tomo pauk]

Thanks. That is from Kotelnikov, I presume?
The M-71 was already featuring the 2-speed S/C, going from the table posted here (can be translated)? Power was 1798 or 1673 CV, at FTH of 2250 and 5025 m respectively.

 

[FLYBOYJ]

Linbergh's procedure was pretty much the same as Tony Levier's which means it was pretty much what both Lockheed and Allison recommended for P-38s ( Army instructors didn't ?). It was also pretty much standard for Merlins and most other aircraft engines that had pilot or FE controllable mixture settings.

WW2 pilots were so ingrained about over boosting that I think some sections of the POH (especially performance charts) were ignored.

In many aircraft those throttles BELONG to the FE, the pilot just "steers the plane."

 

[pbehn]

The TU-4 was a reverse engineered B-29, so it required the development and deployment by the U.S. before the Russians were able to take interred examples and create the TU-4 and it's native powerplants.

Yes I know but the engine was a reverse engineered engine from an earlier model, I was just suggesting if the Russians could fly a B29 copy in 1947 maybe the USA could have done it much earlier after all from wiki

The R-1820 Cyclone 9 represented a further development of the Wright P-2 engine dating back to 1925. Featuring a greater displacement and a host of improvements, the R-1820 entered production in 1931. The engine remained in production well into the 1950s.

 

[Shortround6]

Yes I know but the engine was a reverse engineered engine from an earlier model, I was just suggesting if the Russians could fly a B29 copy in 1947 maybe the USA could have done it much earlier after all from wiki

The Russian engine was NOT reverse engineered. Using the same (or similar) starting point it took the Russians until 1947/48 to develop a production/serviceable engine comparable to the R-3350 which was in service 2-3 years earlier.

The R-1820 Cyclone 9 represented a further development of the Wright P-2 engine dating back to 1925. Featuring a greater displacement and a host of improvements, the R-1820 entered production in 1931. The engine remained in production well into the 1950s.

Not quite right but a common misconception. The Wright Cyclone 9 started as a 1750 cu/in modification (longer stroke) to the 1654 cu/in P-2 (only 14 built) and many other improvements. The P-2 being rendered obsolete by the P&W R-1340 Wasp. By 1930 Wright increased the bore to make the R-1820 "E" series engine and the Cyclone 9 went on through the "F", "G", "G-100", "G-200" and "H" series engines, last engine delivered Dec of 1963.

Aside from keeping the same bore and stroke everything else was changed. For example one difference between a G-100 engine and a G was the introduction of a forged steel crankcase instead of forged aluminium (which had changed from cast aluminium on "F" sereis) . It weighed 30lbs more but was 50% stronger. The G-100 was introduced just 20 months after the G. The G-200 changed crankcases again, still using steel but back to the weight of the aluminum crankcase but even stronger than the first steel one. It followed the G-100 by 26 months. There were changes in pistons, connecting rods, crankshafts, main bearings, cylinder heads ( from cast to forged) and cylinder barrels. The engine went from 920lb for an R-1750 E with reduction gears and running on 50 octane fuel to 1469lbs for a late "H" running on 115/145 fuel. Early versions used 12 hold down bolts per cylinder, changing to 16 bolts on the middle engines and finally 20 bolts per cylinder on the "H" engines.
The "H" was first delivered Oct 1942 although there was quite a bit of overlap (sometimes years) between the start of production of one series of engines and end of another series.

There were also a host of modifications even in a particular series of engines. While the "Cyclone 9" may have been marketed or sold for over 36 years it is quite debatable as to if it was the same engine.

Edit: To clarify the start of the Russian program/development in the fall of 1932 the Russians sent a delegation to the US to negotiate a "deal" for the Cyclone 9 engine with Wright. The "deal" included Wright providing documetaion in metric units and to build and test pattern engines built to the metric system. A Nov 1933 STO decree covered the purchase of about 150 complete engines, 100 engines as parts and and enough of the most complex components for another 100 engines. First Engine was shipped to Russia in Dec 1933. Metric engine completed a 100 hr test in the US in April 1934. By 1936 complete M-25 engines were being built in Russia with no imported parts. This was the start of the series of engines that lead to the ASH-73 used in the TU-4 bomber.