Allison V-3420- Anyone have information on it? It seems like it would have been perfect for the XB-42.

[tomo pauk]

For most of the war, the Merlin WAS a better high-altitude engine. In 1945, not really. Post-war, the Allisons that were developed were more powerful than post-war Merlins at high altitude, where you seem to want to be.

What numbers do yo have to back up the claim of post-war Allisons being more powerful than the post-war Merlins at high altitude, as well as in 1945? What are the versions in question?

The Allison was much easier to overhaul, consuming anywhere from a high of about 67% of the man-hours required for a Merlin down to only 55% late war, and the TBO was longer. I have an old post which said that TBOs were set based on engine performance. That is incorrect. TBOs were set so that a certain percentage (usually 98.5% or more) of the engine cases sent back for overhaul were, in fact, able to overhauled instead of being scrapped. Early-on, both Merlins and Allisons were TBO at about 200 - 250 hours. Later, Merlins went up to around 350 hours and Allison went up to about 500 hours. The change didn't so much reflect reliability as much as the engine cases/parts being able to be overhauled.

Let's say your numbers here are correct.
How much of a good thing is the perfectly reliable V-1710-39 above France, UK or Belgium in better part of 1942, when compared with a less perfectly reliable Merlin 45?
Or, in 1943, above West Europe or Italy, the perfectly reliable V-1710-81 vs. the less perfectly reliable Merlin 60 series?

Everything I've found indicates that the Allison, when it initially was deployed to Europe had 2 main issues (fuel, intake and, perhaps less well known, incorrect operation techniques), making it less reliable than the Merlin (Allison time bomb period). When those issues were solved (about late summer 1943), the Allison was as or more reliable, based on parts wear out, and held a tune longer than the Merlin.

You are knocking on the wrong doors there.
Main issue of the V-1710 when initially deployed in ETO was that it lagged behind in power at higher altitudes when compared with Merlin. More seriously, it was also badly out-performed by German engines.
Lack of performance at higher altitudes was due to the low capacity of it's S/C. There was no quick fix for that, Allison was the institution to do it across the pond.

 

[Shortround6]

A lot of the, shall we say, durability of the engines depended on use/duty cycle of the engines.
What is rather amazing is that both engines were rated at much higher times between overhauls at the end of the war, making much greater power levels, than they were early in the war.
Also means we have to be careful what figures we are using and from when.

RR claimed in one of their books that the Merlin in 1939 (type/s not given but in 1939 there weren't that many different ones ) that the fighter engines were rated at 240 hrs while the bomber engines were rated at 300hrs.
Allison engines were rated at how many hours in 1939?
In 1944 Merlins were rated at 300hrs for fighters (types not given) 360hrs for bombers and 480hrs for transports. In 1945 that jumped to 360hrs for fighters, 420 hrs for bombers and 500hrs for transports.

From 1942 onward they list two different numbers

Percentage of engines reaching time expiry passing through repair organizations 35%

average life of engines passing through repair organizations ...........approximately 60% of normal life for type.

Now please note that engines go to repair organizations for a number of reasons. Like time expired, defects noted during routine inspection/maintenance (metal in the oil. etc).
battle damage, crash damage.

 

[GregP]

What numbers do yo have to back up the claim of post-war Allisons being more powerful than the post-war Merlins at high altitude, as well as in 1945? What are the versions in question?



Let's say your numbers here are correct.
How much of a good thing is the perfectly reliable V-1710-39 above France, UK or Belgium in better part of 1942, when compared with a less perfectly reliable Merlin 45?
Or, in 1943, above West Europe or Italy, the perfectly reliable V-1710-81 vs. the less perfectly reliable Merlin 60 series?


You are knocking on the wrong doors there.
Main issue of the V-1710 when initially deployed in ETO was that it lagged behind in power at higher altitudes when compared with Merlin. More seriously, it was also badly out-performed by German engines.
Lack of performance at higher altitudes was due to the low capacity of it's S/C. There was no quick fix for that, Allison was the institution to do it across the pond.

Like I said, we'll have to agree to disagree. I already covered the V-1710-127. It was ready near the end of the war, but the war was all but over. So, no sense in procuring it. Likewise, the Merlin had some nice test stand runners, too, including the RM 17 that put out around 2,600 hp but was never procured for a flying aircraft either.

Stop beating on it, Tomo; we aren't going to agree. Late model V-1710s were performing very nicely at altitude, both with turbos in late P-38s and with the aux-stage supercharger available in general and installed in P-63s that were sent to the USSR. They'd give most warplanes all they could handle if the range was short enough.

Once the P-38J-25 added hydraulic ailerons, the P-38 could have been returned to the ETO with very good results since we also had decent training by then and the faults had been mostly worked out, particularly heaters and intakes. There was no point since the P-51s were doing the job and the P-38s were performing very well where they were. A LOT of the war record for any aircraft depends on timing and military decisions about where they get deployed and how they are used. If P-51s had never been tapped for escort duty, I wonder how many victories they would have had. But, they were, and there's no point "what offing" ourselves to death.

You and I may never agree on the engines, but the course of the war won't change. The Merlin was a great contributor. I just completely disagree with your contention that the Allison wasn't a very good engine and wasn't reliable. It was both once the initial faults had been rectified. It was even suited to the ETO, just not really in single-stage, single-speed configuration. To fight well in the ETO, it needed a turbo or a 2nd-stage supercharger. The U.S.A. was definitely NOT on wartime development push when the war started, and we didn't really start to develop things until after we were drawn into the war. And ... development takes some time. The Merlin was being developed BEFORE the war started, and they did a very good job of it. Allison didn't exactly do a BAD job, but the war was on while they were in early development, and the planes that were deployed early-on weren't really up to the task.

So, do we fight on or give up? The anwer, rather obviously, is fight on and develop as best you can. We did and the results weren't bad. The P-38, P-39, P-40, P-47, P-51, and even the P-63 all served well. Interestingly, 5 of those 6 aircraft started with Allisons. The P-51 obviously moved to the Merlin, but the Allison versions were well suited to what they were used for. The sum of the Allied effort won the war. The U.S.A. didn't win it alone and neither did the British. We both might have lost had the Germans not invaded the Soviet Union, but they DID. In my mind, the Allison played a significant part in our wartime efforts, and it always will.

Was it playing catch-up with the Merlin for most of the war? Yes. But it did catch up and the planes it powered did the job well enough in the end. Their collective war record isn't bad at all. Good enough to win, anyway, when taken together with their other allied counterparts.

 

[tomo pauk]

You and I may never agree on the engines, but the course of the war won't change. The Merlin was a great contributor. I just completely disagree with your contention that the Allison wasn't a very good engine and wasn't reliable.

It is fine to disagree.
What is not fine is putting the words in one's mouth - please quote my post where I've disparaged V-1710's reliability.

It was even suited to the ETO, just not really in single-stage, single-speed configuration. To fight well in the ETO, it needed a turbo or a 2nd-stage supercharger.

The single stage configuration of the V-1710 was exactly what was found in 80% or aircraft powered by it before 1944.
Thing to note is that 1-stage Merlin (main competition that we talk about here), DB 601/605 and BMW 801 (powering the real threats to the pilots flying a V-1710-powered fighters) were better performers than 1-stage V-1710s - a far more serious thing than us here trying to prove the respective points.

Allison didn't exactly do a BAD job, but the war was on while they were in early development, and the planes that were deployed early-on weren't really up to the task.

??
USA was not in a war from 1927 to the late 1941, during the time the V-1710 was being developed.
Main shortcoming of the P-40, P-39 and P-51 (yes, really bad fighters...) was that their engine was behind the curve when compared with Merlin and Axis best. P-40 and P-51 were improved (P-51 was greatly improved) with Merlin in the nose.

If P-51s had never been tapped for escort duty, I wonder how many victories they would have had.

That misses the point - P-51 was tapped for escort duty because engine transplant enabled it to reach it's potential, that included out-flying whatever the Axis could deploy (with reservation to the rocket/jet aircraft). Victories were the consequence of that.

 

[wuzak]

I already covered the V-1710-127. It was ready near the end of the war, but the war was all but over. So, no sense in procuring it. Likewise, the Merlin had some nice test stand runners, too, including the RM 17 that put out around 2,600 hp but was never procured for a flying aircraft either.

There were 2 years between the first run of the RM.17SM (1944) and the V-1710-127 (1946).

The RM.17SM had been cleared for flight at >2,300hp (not sure if it actually did fly), passed its type test at 2,200/2,100hp and was ready for production before the end of the war.

At the end of the war the V-1710-127 was, at best, a non-functional mock-up, or, at worst, an idea in someone's head.

"It was ready near the end of the war" is true if near the end of the war was over a year after the end of the war, and "ready" is true if one can accept the limited life of the turbine before it melted, requiring an entirely new turbine design for the project to proceed.

 

[GregP]

It is fine to disagree.
What is not fine is putting the words in one's mouth - please quote my post where I've disparaged V-1710's reliability.



The single stage configuration of the V-1710 was exactly what was found in 80% or aircraft powered by it before 1944.
Thing to note is that 1-stage Merlin (main competition that we talk about here), DB 601/605 and BMW 801 (powering the real threats to the pilots flying a V-1710-powered fighters) were better performers than 1-stage V-1710s - a far more serious thing than us here trying to prove the respective points.


??
USA was not in a war from 1927 to the late 1941, during the time the V-1710 was being developed.
Main shortcoming of the P-40, P-39 and P-51 (yes, really bad fighters...) was that their engine was behind the curve when compared with Merlin and Axis best. P-40 and P-51 were improved (P-51 was greatly improved) with Merlin in the nose.

That misses the point - P-51 was tapped for escort duty because engine transplant enabled it to reach it's potential, that included out-flying whatever the Axis could deploy (with reservation to the rocket/jet aircraft). Victories were the consequence of that.

Trying talk with you is like getting surgery without anesthestic. You can find where you've said the Allison was less than good and/or reliable; I don't need to go hunt it down.

Hope you had a good holiday, if you observe it.

Cheers.

 

[tomo pauk]

Hope you had a good holiday, if you observe it.

Cheers.

Happy holidays to you, too.

 

[Zipper730]

"Boeing XB-39"

Only a couple of bits, but interesting.

That's about the information I already had. I didn't assume it to be quite as reliable as some of the stuff I'd find elsewhere such as WWII Aircraft Performance, SAC (Standard Aircraft Characteristics) sheets and so forth.

 

[GregP]

The V-3420 was reliable enough for a W-24 engine. That isn't exactly a reliable bunch to be included in, but the V-3420 wasn't noted for being unreliable. Neither was it without fault. With development, it could have been a decent engine for the complexity involved. But, it suffered from being the engine that was developed as insurance against the R-3350 failing. In my mind, the R-3350 DID fail. The B-29A wasn't noted for returning home with all four turning all that often and the V-3420 should likely have been pursued.

I prefer to think of it as, "the state of the art wasn't quite ready to produce a reliable 2,500 to 3,500 hp piston engine at the time." Everyone who tried a super big piston had issues including the Allies and the Axis over many engine types. Some succeeded and some didn't. More didn't than did.

Early V-3420s were in the 2,600 hp class. Developed, they could have gotten into the 3,000+ hp range without too much difficulty, but the market never seemed to quite materialize.

I have a friend who has two of them and would like to get one running. I'm not holding my breath.