No US-built Merlin: plausible developments?

[tyrodtom]

The USAAF in Europe lost more aircraft to flak, than they did fighters.
Reducing their altitude would make them more likely to take even more damage from their greater threat, flak. Because 10-14 k feet puts the within the range of even medium flak, 37-40mm . More guns shooting, with less of a aiming problem, would offset the ability to protect them from the fighters.

 

[wuzak]

Griffon engine versions pushed forward /B]

I disagree.

The Merlin engine had top priority because it powered Spitfires and Lancaster bombers. If the USA doesn't supply Merlin engines then Rolls Royce will be told to concentrate exclusively on Merlin engine production. Development of the Griffin engine and other Rolls Royce projects will sputter to a halt for the duration of the war.

While production of the Merlin will take priority, as it did in 1940, the development of the Griffon won't be delayed any more than historically. Production would be the issue.

When these decisions have to be made the Griffon is in initial development, but has been earmarked (from 1939) and modified for use with the Spitfire. The Merlin engined Machester III is just being mooted, while the Merlin Halifax I is about to start production.

I would suggest that bythe time Lancaster production begins the fears over Hercules shortages have been put to rest, and more Lancasters and Halifaxes are so powered - freeing up the Merlins for Spitfires and Mosquitos. Meanwhile, the Griffon Spitfire continues apace.

Also, no reason that the Lancaster can't be adapted to the Griffon sooner, thus giving the Griffon an even higher priority than historically.

 

[GregP]

I think the aux stage was a dead end because of the weight and length it added. Fine for a bomber or larger aircraft, even though a penalty .... but relatively impossible for a small fighter.

 

[wuzak]

I think the aux stage was a dead end because of the weight and length it added. Fine for a bomber or larger aircraft, even though a penalty .... but relatively impossible for a small fighter.

It did enable them to keep the standard single stage front section as per turbo installations - at least on some 2 stage versions.

 

[parsifal]

I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.

merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942. A failure to produce the merlin would delay the commencment of the great offensives in 1944, particulalry the air offensives. This would delay the cross channel invasion and allow the Russians time to overrun the whole of Europe. that would probably have had implications for the whole of Europe that would continue to affect us today.

The US built 150000 merlins from 1942 to 1950. You cannot remove that many engines, with a delay of say 1 year and not expect massive impacts on your force structure. Much as this might pain the US forum members, the merlin was one of those critical pieces of kit that could not be ignored in the US victory. The germans had a similar reliance on their DB engines

 

[Shortround6]

I don't differ with you; just saying that without the Merlin it may be a good compromise. I see the bomber effort as initially an air superiority contest requiring fighter escort primarily to destroy LW interceptors and secondarily to protect bombers –though one is a function of the other. Without escort, even Ju-52s were able to stand off and fire rockets at the bomber formations.

Do you have a reference for this last bit?

The P-39 was included with regard to availability and the thought that it had perhaps a range of 500 mi. internal fuel.

I realize that you are new here and I have no idea if what you actually know. I would suggest that there are many technical manuals in the Technical section available for viewing or download. They give a much better idea of the capabilities of some of these aircraft than many print books or websites. However a good website is Zeno's Warbird Video Drive-In - World War 2 airplane videos playing for free live online which has a number of pages from such manuals for mostly American aircraft such as:

http://www.zenoswarbirdvideos.com/Images/P-39/P39SEFC.pdf

and: http://www.zenoswarbirdvideos.com/Images/P-39/P39FOIC.pdf

Granted this version of the P-39 only had 87 gallons of fuel but even with 120 gallons the "range" of a P-39 is not great. For escort duty you can fly on the drop tank/s ( I don't care how big it is) until combat is joined, at which point the tank/s are dropped and you have 120 gallons of internal fuel. USAAF doctrine ( I believe, memory could be going) called for radius of action to figures at 5 minutes of Military power after tanks are jettisoned ( about 11.5 gallons for the late P-39s) and 20 minutes of MAX continous power, even 15 minutes of max con power is worth 27-28 gallons for the P-39. You now have 81 gallons to get home with. A P-39 burns about 0.5-0.66 gallons a minute at it's most economical speed so allowing just 20 minutes reserve to find the airfield and land means another 10-13 gallons that can't be used. Call it 70 gallons to get home and you can't fly at the most economical setting in enemy territory. At 240mph indicated (312mph true) at 15,000ft the P-39 burns 65 gal an hour or about 4.8MPG. 5 minutes at WEP instead of Military power burns an extra 2.5 gallons (12 miles) and an extra 5 minutes at max con power before heading home cost 9 gallons (43 miles). Prevailing winds over Europe are out of the west. A head wind heading home much more often than not.
How far from the English coast do you want to be when the drop tanks go? 300miles? 200 miles? Less?

Same with Flak. As long as the bombers stayed above the 20 mm stuff, the quantity wouldn't increase much though the aim and duration over Flak concentrations would somewhat.

Even if you are above the 37mm stuff you have just radically increased the Flak's effectiveness. Say a German anti-aircraft gun has a max ceiling of 9900meters, it may have an effective ceiling of 8000 meters, effective ceiling is the altitude at which it can track a target and fire a certain amount of shots at it. This ceiling may require the target aircraft to fly directly over the gun and flying several thousand meters to the side could put the target out of effective range ( due to the slant distance). Dropping the target aircraft to 4500-5000meters and the gun can begin firing sooner and keep firing later. It can also fire at targets flying a flight path further to the "sides". If the time fuses have an error of 0.02 of the time of flight cutting the time of flight means "shorts and longs" will actually be much closer to the target. Considering the rate at which shells slow down a 1/3 reduction in altitude may result in 1/2 the time of flight. This also reduces the amount of lead needed further increasing the accuracy.

Without fighter protection, the 190s and 109s really didn't need much performance to ravish the bombers.

True but by dropping the bombers AND their escorts into the prime altitude band for the 190 means that the "air superiority contest requiring fighter escort primarily to destroy LW interceptors and secondarily to protect bombers" just shifted somewhat into the Luftwaffe's favor compared to fighting at higher altitudes. The 190s being much more able to deal with allied fighters at 4000-6000 meters than at 7000 meters and above.

My point has to do with tactics to deal with the lack of high altitude, long range escort fighters, which was the situation prior to the arrival of the P-51B. This was a terrible time for the bombers. Perhaps it would have been less so had they come down a bit. From a tactics viewpoint, the bombers set the combat altitude.

Maybe you are right and maybe you are just trading one means of loosing bombers for other ways.

 

[wuzak]

I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.

merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942.

Had to be made before 1942. The Packard factory had to be built and start supplying engines by then.

The US built 150000 merlins from 1942 to 1950. You cannot remove that many engines, with a delay of say 1 year and not expect massive impacts on your force structure. Much as this might pain the US forum members, the merlin was one of those critical pieces of kit that could not be ignored in the US victory.

Packard built 55,000 Merlins - mostly for the British. Continental made a few, but no more than a couple of thousand, and only very late in teh war - they were gearing up to build the IV-1430.

There were 150,000 Merlins built all up.

I thought US production of Merlins finished not long after WW2.

 

[Shortround6]

I think a decision by the US to not produce the merlin would be a strategically very significant event, and likley to extend the war considerably.

merlins were built under licence because US engines, despite years of development were not ready for mass productuion, and decisions on design, and what to produce and in what numbers had to be made in 1942. A failure to produce the merlin would delay the commencment of the great offensives in 1944, particulalry the air offensives. This would delay the cross channel invasion and allow the Russians time to overrun the whole of Europe. that would probably have had implications for the whole of Europe that would continue to affect us today.

I agree with much of what you say except that your timing is off. The Decisions as to what engines to be made were being made in 1940. Packard signs the deal to make Merlin's in Sept 1940, it takes about one year to get the first 2 ceremonial engines onto test stands. It takes until Dec 1941 for production to exceed a dozen a month. Also in Sept 1940 Ford signs deal to make R-2800s and breaks ground on new factory to do so. It takes 13 months to deliver 1st engine, Nov 41 sees 99 engines and by May 42 production hits 500 a month and keeps climbing. Packard had hit 500 engines a month the Month before. Allison had reached 500 engines a month in July of 1941. Studebaker, Buick and Chevrolet started delivering engines in March, April and May of 42 respectively so the "decision" had to made about a year or more earlier.
Over 2/3s of Merlins made by Packard went to Commonwealth aircraft. While the Merlin may not have been a deal breaker for US forces (depends on view of the Mustang) the loss of that many engines ( or the substitution/delay) of that number of engines to the Allied cause WOULD have very large consequences that cannot be argued/wished away. A one year delay in Packard Merlin Production was worth 7-8000 engines PER year for 1942/43/44 for a total of of around 21-23,000 engines. That is just sliding the 2-42 production to 43 and 43 to 44 and so on.

This makes the decision to go for the Merlin that much easier. 2 reasons.

1st, The US was refusing to build British weapons built to British Specifications but would build weapons/equipment to British orders that US forces could/would use. (No British tank designs and so forth).

2nd, the Merlin in the summer of 1940 was a proven engine with thousands of MK IIIs made, hundreds of MK Xs and the MK XX ready to go. In the summer of 1940 Allison production had yet to break 100 a month, a total of 8 R-2800s exist. Just over 200 R-2600s were built up until Jan of 1940 and while another 400 had been built by the end of June 1940 they had little time to establish a track record.
The R-1820 and R-1830 were both known quantities but development potential was limited.
Any other US high powered engines existed in quantities under a dozen at best or as "vaporware".

 

[Edgar Brooks]

I disagree.

The Merlin engine had top priority because it powered Spitfires and Lancaster bombers. If the USA doesn't supply Merlin engines then Rolls Royce will be told to concentrate exclusively on Merlin engine production. Development of the Griffin engine and other Rolls Royce projects will sputter to a halt for the duration of the war.

No, they wouldn't; the Air Ministry couldn't dictate what a private company's development department did, or didn't, do to that extent. They could refuse to order any new engine, but, if it turns out to be a better product, that would be foolish in the extreme, and Heaven help them if the government found out that they were deliberately holding things back.

 

[GregP]

Parsifal,

The Allison WAS in mass production. We also had a high-altitude system for it.

The decision makers decided to remove that from the popwer system of our fighters by deleting the turbocharger.

Once we identified the issues with the intake system, it took only several months to fix. It took almost a year to realize that European fuels were not teh same mix as American fuels. That took some carburetor adjustments, but was also fixed.

 

[davebender]

That wouldn't surprise me. The USAAF didn't arrive in Europe in large numbers until the war was two thirds over and the Luftwaffe was short on aviation gasoline.

What do you think would happen if the RAF of 1939 were replaced with the USAAF of 1939?

 

[Balljoint]

I realize that you are new here and I have no idea if what you actually know.

My interest is broad and tends towards strategy. While I think I have a working knowledge of the aviation it definitely is not the encyclopedic expertise of many on this forum. For the most part I've been content to lurk.

My post was intended to tease out one aspect of a larger strategy to test it against greater knowledge – but I thought it might have enough meat as to not waste your time.

I'm sure I had a source for the stand off rocket attack, but the Ju-52 was more an example since many of my resources disappeared during a remodel. I will search though.

And I stand corrected on the P-39; I shouldn't have dragged it into this issue, i.e. an Allison mustang.

More specifically, the "no Merlin" period from mid1942 until the early 1944 is the period that I'm concerned with. The LW could easily evade the part-way escort. Bomber losses were horrendous. Allison-powered fighter performed well at lower altitude for the Soviets -albeit in tactical roles- and against Oscars in China. The P-51A was an ugly duckling that, with long range tanks could fill a huge gap at lower altitudes.

Actually, I thought that weather would be the main objection. Flak didn't really track flights but instead filled blocks. Maybe this would change at less height. LW interceptors had to form up at low altitudes so would they gain altitude for the vertical advantage or just come in?

There are a number of "what if" issues for sure. But when the P-51Bs stared escort duties about Jan 1944 the LW fighter capability was still strong. About May of 44 the allies gained air superiority over Western Europe. What if the P-51A had been on the scene from mid 43 with low altitude but long range escort? Many, many questions, but maybe it would have helped.

 

[tyrodtom]

A Ju-52's service ceiling is 17,000 feet, as low as the daylight formations flew was 22,000, but usually higher. With the Ju-52 top speed being about the same as a allied formations speed and it's altitude being a least a mile lower, I just don't see the possibility of a Ju-52 lobbing rockets at anything but empty sky.

 

[Shortround6]

The Allison WAS in mass production.

Please define mass production. In 1940 Allison built/shipped 3 engines in Jan, 7 engines in each of Feb, March and April, 14 engines in May, 30 in June, and 73 in July.
Allison did deliver 223 engines in Sept when the deal with Packard was signed. First time production hit triple digits. Production fell below 200 per month 3 times by April of 1941 with a high of 400 in Feb. 1941.
Things got much better after May of 1941. But by that time The Aircraft engine industry was tooling up in massive fashion. The deals with Studebaker, Buick and Chevrolet were already signed in addition to the Packard and Ford deals and more were to come.

We also had a high-altitude system for it.
The decision makers decided to remove that from the popwer system of our fighters by deleting the turbocharger.

The decision makers made that decision because, in their opinion, the 1939 turbo system wasn't ready for either production or squadron service or both. They estimated that waiting for a turbo system that was usable in squadron service would delay the P-40 (see P-37) and perhaps the P-39 by an additional year. Turbo P-40s showing up in the Spring of 1941 instead of non-turbo P-40s the Spring of 1940? Turbo P-39s showing up in Dec of 1941 instead non turbos P-39s in Dec of 1940? It took about 1 year to go from 5th aircraft delivered to the 1000th aircraft delivered for those two models. A little less for the P-40 and a little more for the P-39.

Much is made of the lack of high altitude capability of American fighters in the Spring/summer of 1942. Not many people consider the effect on the US of being about 2000 fighters shorter than we were at the time of Pearl Harbor and the carry over into the Spring/summer of 1942. Low altitude fighters being better than NO fighters.

Allison realized the need for a better supercharger in 1938 and started the 2 stage project. But when you are making only 1-2 engines a month and even those are not the same model and trying to expand the factory by an order of magnitude ( or several orders of magnitude) at the same time, certain projects get moved to the back of the stove.

Once we identified the issues with the intake system, it took only several months to fix. It took almost a year to realize that European fuels were not teh same mix as American fuels. That took some carburetor adjustments, but was also fixed.

Which problem with the intake? I think there was more than one.

Anybody with any knowledge of gasoline at all KNEW there was a difference in US gas and British gas in 1940. The specifications could not have been more clear. US Spec fuel could not contain more than 2% aromatics. British Spec fuel could not contain less than 20% aromatics, ten times the US max. Without the aromatics however there is NO rich response (or a very small one), no 100/130 fuel. US fuel Specs were brought into line with the British ones, what the British may have given up I don't know.

The problem with "European fuel" came later. In an attempt to stretch fuel supplies a higher percentage of heavy compounds were allowed in all 100/130 fuel. Not all batches of fuel may have gotten the heavier compounds or gotten them in the same amounts. These heavy compounds showed a greater tendency to condense out (or the fuel, being a bit heavier condensed easier?) at low temperatures and 'puddle' in the intake manifolds. This problem was known/anticipated and Allison was working on a new intake manifold in the late spring or summer of 1943. BY the time P-38s in Europe were actually having difficulties the New manifolds were already designed, flight tested and in production. New engines got the manifolds and old engines were retrofitted in the field with the new manifolds often shipped by air to the units.
With fuel being made in a number of different refineries and with different amounts of certain compounds allowed or used ( there are over 400 different compounds that can be used in "gasoline", obviously not all at the same time) it is not surprising that a few batches may have come up a little short. I would note that the problems the European P-38s had were also made worse by poor piloting technique. They were being taught to cruise at low boost and high rpm which is not only wrong from a range//endurance standpoint (and against both Allison and Lockheed recommendations) but caused the intake charge temperature to be lower than normal which added to the fuel vaporization problem.

P-38s in warmer theaters may have gotten poorly blended fuel but the warmer temperatures (and lower altitudes) may have kept the vaporization problem to a minimum.

According the "Vees for Victory" ALL Allisons go the new manifolds, P-39s, P-40s, and Allison powered P-51a/A-36s, not just P-38s.

 

[tyrodtom]

That wouldn't surprise me. The USAAF didn't arrive in Europe in large numbers until the war was two thirds over and the Luftwaffe was short on aviation gasoline.

What do you think would happen if the RAF of 1939 were replaced with the USAAF of 1939?

That's a bit of exaggeration there dave. If the Luftwaffe was getting short of fuel before the USAAF got there, it would be because they just didn't produce enough, because no one had targeted petrol production to any serious extent up to that time.

In 1939, that would be the USAAC, less than 60 B-17s by the middle of 39, the P-40 first flew in late 38. So a American effort at bombing in 1939 would be B-18s escorted by P-35s and P-36s. That would be a sad exhibition.

 

[Shortround6]

– but I thought it might have enough meat as to not waste your time.

If you are willing to learn then you are not wasting my time or, I hope, the time of any of the many members who are more knowledgeable than I am.
We have certainly discussed many subjects with less meat to them

Actually, I thought that weather would be the main objection. Flak didn't really track flights but instead filled blocks. Maybe this would change at less height.

Flak did both. If you have hundreds of guns and hundreds of bombers flying over them then you can just point the barrels up and have at it. But every major nation spent a lot of time and money on "predictors/directors" that would track an aircraft target and predict the future location and the time of flight of the shell to get there. They were mechanical analog computers. The Predictor sent signals to the guns that moved pointers on dials, the gunners traversed and elevated the guns until matching pointers lined up with predictor driven ones. One man controlled the traverse and one man the elevation and they never looked at the airplane/s in question, just tried to keep the pointers aligned. The Predictor also sent signals to the automatic fuse setters. The gun crew just stuck the nose of the shell into the fuse setter and automatic jaws aligned the fuse and twisted the timing ring to the correct setting, the crew then removed the shell and loaded it into the Breech in a measured fashion. (predictor figured in a set loading time between setting the fuse and gun firing.
The lower the time of flight the easier the predictor's "job". Low level attacks took out the predictor because there wasn't enough time to track and get solutions. heavy AA didn't work well below certain heights.

 

[Shortround6]

Probably, but it was the Army's baby.

True but nepotism should only go so far

Possibly a better bet would have been in the Lycoming H-2470?

Possibly but it suffered from some of the same problems as the IV-1430, like the separate cylinders. The Army did try to complicate even further by adding such "features" as a two speed propeller drive which added several hundred pounds of weight.

The 2A-2775 maybe a lightweight engine that couldn't have too much development, in the form of boost, at that weight. Still, At 1720lbs dry it would have an installed weight similar to an R-2800 and as much power. And it would have been available sooner.

It is a mighty big maybe. Consider that the Rolls-Royce Vulture was an X 24 of 2592 cu in (an X-2590 or 2600 in American terms.) that weighed 2450lbs for 2000hp? at 3000rpm. BMEP=203. For Packard to get 1900hp out of a 7% larger engine turning 6.66% slower and yet weighing only 70% as much must mean either that Packard knew a lot more than than R-R about engine building or that the Packard couldn't put out that kind of power for very long (as in service life).
Also consider that the X-2775 was little more than two short stroke V-1500s running on a common crankshaft and the V-1500 dates from 1924. There were only two and possibly three X-2775s built, the same engine/s were rebuilt into several different configurations.

The 1A-5000 and 2A-5000 were never completed. The poppet valve 5000 series engines were based off the V-2500 cylinder blocks (another 1920s engine) and bore X stroke.
While the Marine versions in PT boats started at 1200hp and went to 1350 and then 1500hp I would note that these are ground supercharged engines. The supercharger is used to boost performance at ground (sea) level and not for altitude performance. Please subtract about 2% for every 1000ft for altitude performance. Granted a different supercharger and/or gear ratio could improve altitude performance but only at the cost of lower sea level performance.
Think of them sort of like a Merlin VIII in a Fulmar.

 

[tomo pauk]

<snip>

This great post should go to myth buster topic, sticky, or something similar. A required read.

Further on the tread:
What changes for the British production would been undertaken, in order to use the R-2800 or V-1710 (produced by Packard in this time line) in airframes of their origins? Mossie FB with V-1710 (ducks for cover)?

 

[wuzak]

Question: If Packard aren't building Merlins in 1942 is it because Packard or the US Government rejected the request from Rolls-Royce/British Governemnet?

If this is rejected, what of the Tizard mission? Will he take all his goodies (cavity magnitron, jet engine planes, other bits of British technology) back home with him?

 

[Balljoint]

Do you have a reference for this last bit?

The last bit being the ability of JU-52s standing of and launching rockets. No luck on the cite I had in mind but I understand the Ju-52 skepticism. I did find the following at page 208, Masters of the Air by Donald L. Miller;

"That morning, there were more enemy fighters in the air than on the first Schweinfurt mission, and dozens of them were rocket ships: converted twin-engine night fighters, most of them Junkers 88s, capable of launching 250-pound missiles from tubes suspended beneath their wings –called stovepipes by the Germans. These were the rockets that had helped decimate the Hundredth at Munster –fused missiles that streaked towards the bombers and detonated at a predetermined range, creating bursts four times the size of ordinary flak explosions. … The Junkers launched the missiles out of range of the bomber's guns."

Certainly a Ju-52 differs from a Ju-88. But even the Ju-88 would not be there in the presence of escort fighters. Of course rockets were used later by German interceptor fighters but only in the face of escort fighters.

It's just an opinion, but I suspect that, while overall more bombers were taken by flak than air opposition, if the timing were examined the air losses would be rather larger through early 1944, and thereafter the flak losses would go up sharply. Hitler didn't want the LW to be a "defensive" weapon. Thus he beefed up the AA to over 13,000 heavy guns while the bombing targets, such as the synthetic fuel plants, became more concentrated.