USAAC/AAF being much improved in 1938-42?

[Shortround6]

By mid/late 1942, Mustang can get the Merlin 50. Yes, not the 2-stage version, but better engine than the best 1-stage V-1710 the Mustang ever got.

Why?
The Merlin 50 is a Merlin 45 with a different carburetor. Single speed
If that is all you want stick the V-1650-1 two speed single stage engine in the P-51s, of course that means that there are fewer P-40Fs and Ls.

 

[tomo pauk]

Why?
The Merlin 50 is a Merlin 45 with a different carburetor. Single speed

Member asked (my bold):

I believe that the British converted a P-51 to have a Merlin as a proof-of-concept, so they could probably do a conversion. Are you asking if it would have made sense for North American to ship the RAF engine-less P-51s for completion in the UK? I'm not sure the UK had the industrial capacity needed for that without adversely affecting another program.

So, the Merlin 50 (or 45, or 46, I'm not that picky) goes into Mustang airframe.

If that is all you want stick the V-1650-1 two speed single stage engine in the P-51s, of course that means that there are fewer P-40Fs and Ls.

I've always wanted V-1650-1 in Mustang airframe, ASAP (1942-43). Despite having less P-40Fs and Ls produced.

 

[Kevin J]

Member asked (my bold):



So, the Merlin 50 (or 45, or 46, I'm not that picky) goes into Mustang airframe.



I've always wanted V-1650-1 in Mustang airframe, ASAP (1942-43). Despite having less P-40Fs and Ls produced.

Maybe, P-51A with V-1650-1 instead of P-40L. There were still some issues with the P-51 as a fighter.

 

[Shortround6]

I think people often forget how fast paced the Mustang program was and how much overlap was going on.
Without changing the orders around too much the US only had 810 Allison powered Mustang/Apache airframes.

The British had 770 airframes.

The British start with 620 that are paid for with cash, likewise the Allison engines are paid for with cash. The orders are placed in the spring/summer of 1940.
The first production plane is rolled out in April of 1941
In July of 1941 the British order 150 more aircraft paid for by lend lease, This is two months before a Mustang is loaded on a ship and sent (via the Panama canal) to England. It doesn't arrive until the the 24th of October 1941. Aside from some reports from whatever pilots the British had doing acceptance flights at the factory in California this is the first the British get a look at what they had purchased back in 1940. Actual test flying at at Boscombe Downs starts Jan of 1942.
In April of 1942 the US orders 500 A-36s as funding trick to keep the production line open. At what point the the line changes over to building the P-51 lend lease planes with four 20mm cannon I don't know but the first one is test flown on May 29th 1942, This is just under 2 weeks after the British use the Mustang I on it's first operational mission. Of the 150 planes ordered 93 make it to the British, the US takes 55 as the F-6A photo recon planes and two are used as Merlin test beds as the XP-78, On June 23rd an order is placed for 1200 Allison powered P-51As. A contract for the completion of the planes to use 2 stage Packard Merlin's was given to NA on July 25th 1942. 2 days later 16 Mustang Is make a fighter sweep over the Ruhr. The first time allied fighters have been over Germany since the fall of France?
August 1942 was a busy month for the Mustang, One of the XP-78s was being worked on, 5 Mustang Is are sent to RR for development of the Mustang X, The British manage to have 4 squadrons in service using Mustang Is, and at the end of the Month on the 26th the US orders 400 Merlin powered mustangs, later the order is increased by 1350 aircraft.
In sept of 1942 the first A-36 is flown. On Oct 8th 1942 NA gets another contract for 1350 airplanes to be built in Dallas as P-51Cs with Packard Merlin 2 stage engines. This is before the first flight of a Merlin powered Mustang X takes place in England. In Jan 1943 the USAAF orders another 2000 Merlin Mustangs and the order for 1200 P-51A's is changed to 310 Allison powered planes and the remainder are to be completed as P-51Bs with Merlins.

Now please note the first P-40E is not delivered until the middle of 1941 and the first P-40F production plane is not delivered until Jan/Feb of 1942.
By the time you have any real number of even V-1650-1s they were already planning to fit (and cutting metal) on the prototype 2 stage engine planes and ordering Merlin powered P51s by the hundreds.

 

[davparlr]

you are comparing a loss of speed with the change in drag. They are not quite the same thing.
Drag goes up with the square of the speed, but drag isn't really powered required either, that goes up with the cube of the speed.

All I am comparing is two aircraft of similar design both at the same altitude and generating similar horsepower/thrust. Ideally power, equalized at SL is a much better demonstration of drag difference, but I don't have that so this will have to do. With identical thrust, identical wing, and identical altitude, the only effect on velocity is A and Cd. A is affected by engine size and Cd? I don't know but am sure is affected. However, for this example, at this altitude, at this power, with identical wing, there is about 10% difference in drag. Now, as altitude goes up, the percentage difference of drag decreases, and conversely, as altitude goes down, percent difference increases.

he "old tech" bombers had turbos that allowed for a pretty good amount of power at 25,000ft, more than the R-2600 could supply without a turbo. The few attempts at putting a turbo on the R-2600 didn't work out well. The engine seemed to have cooling problems.

I don't know much about engines, certainly not as much as you, but it appears to me that by the time more money became available to improve engine performance for war, and the more powerful R-2800 engine coming on line, the R-2600 was moving backward in demand and interest and thus affecting desire to update. I certainly would have used the R-2800 (with a P-47 turbo?) for an upgrade bomber for '43. I would expect a 40-50 mph cruise speed improvement at 25k ft.

formation speed being based on the worst performing plane being on the outside of the formation as it makes a turn.

The "old tech" bombers will fly formation at less than 180-200 mph, very slow. The newly being developed "super tech" B-29s are still going to be formating (sic) 50+ mph faster. I don't think turns are too big a deal. Outside bombers will just add some planned power increases, also, in general, I suspect there will be only a few turns. No yanking and banking here. Also I would expect this much airspeed increase to have a significant effect on survivability primarily due to reduced exposure to defenses, increased difficulties in targeting, and reduced effectiveness of airborne defenses due to reduced reaction time and increased fuel consumption required for intercept.

Of course I am sure that at that time it was fully expected the B-29 would be operational early 1943 and would then be available for Europe. Unfortunately, the B-29/B-32 (which could also have replaced the B-17/24) had significant delaying problems with their similar engines, an unfortunate decision. As I have said, these sucked up all the resources for bomber development. In hind sight, it would have been more prudent, and save more lives, to not build the basically worthless B-32 and instead develop a lower risk advanced bomber ala unpressurized B-33A.

 

[tomo pauk]

I think people often forget how fast paced the Mustang program was and how much overlap was going on.
...

USAAC/AAF received 1st Mustang for testing in late August 1941. They fast-pace it into warehouse and flight test it after 100 days or so. Or, it took AAC/AAF about same time to test it as it took for the NAA to roll out the NAA-73, or, about same time it took for a ship to go California-Panama-UK.
AAF was so eager to have Mustang so they almost strangled it in crib (some people think that was because of strong hugs, I don't), it took fiscal maneuvering to prevent Mustang production line being shut down.
British noted immediately (early 1942) that Mustang was a good fighter, and that just needed Merlin to be even better.

Now please note the first P-40E is not delivered until the middle of 1941 and the first P-40F production plane is not delivered until Jan/Feb of 1942.
By the time you have any real number of even V-1650-1s they were already planning to fit (and cutting metal) on the prototype 2 stage engine planes and ordering Merlin powered P51s by the hundreds.

Do 'we' have 2-stage Merlin engines (either in UK or in USA) or we don't?
If not - stick 1-stage engines in the nose, nobody will cry if yet another squadron of P-40Fs or Spitfire Vs is not delivered in 1943, those are not aircraft that can bring war to Germany proper.
If we have the engines - even better.
You've noted, many times, that 'planning to fit' is way diffierent to 'have stuff, will fight' situation.

 

[XBe02Drvr]

I certainly would have used the R-2800 (with a P-47 turbo?) for an upgrade bomber for '43. I would expect a 40-50 mph cruise speed improvement at 25k ft.

A bit optimistic here, aren't we? I doubt you'd get that much gain unless you emulated the slender tube/low drag remote turret B29 airframe profile. Drag reduction is generally much more effective than adding power for speed gain. That means the remote control turret technology has to get perfected much earlier than it was for the B29, and the resources to build a fleet of these things have to be diverted from other desperately needed programs. Good luck!
Cheers,
Wes

 

[davparlr]

I'm not so sure my estimate is far off. The B-33A, which was under contract, was expected to have a 242 mph cruise speed, about 60 mph faster than the B-17 and 40 mph faster than the B-24. That was with R-2600 engines. The R-2800 engines would produce a max increase of 800 hp total for four. Now the B-33A cruising speed may have been at a higher altitude but I think I'm in the ball park. The B-26, was a very aerodynamically clean aircraft for the day.

As for resources, don't build the B-32, cancel my beloved B-26.

 

[Shortround6]

Part of the problem in shifting to "new" types of aircraft was the incredible investment in new factories/production facilities.

For the B-33A "By May 8, 1941, it had been redesigned with four 1800 hp Wright R-2600-15 radials with a wing mounted high on the fuaelage and twin tails. The crew was to have been seven, and a gross weight of 95,000 was projected. "

Now the R-2600-15 is a bit of a mystery engine, only one other R-2600 was ever rated at 1800hp. The R-2600 jumped from 1700hp to 1900hp and the 1900hp version had next to no interchangeable parts with the 1700hp version. Wright built a grand total of ONE R-2600-15 engines and that may have been in June of 1942.
Production of the 1900hp versions didn't really start until Aug 1943 (first month they built over 10).

Studebaker had been brought into the aircraft engine production scheme by the end of 1940 and by the end of 1944 they had built over 57,000 R-1820s, just about all for B-17s?
Buick built 8395 R-1830s in 1942 alone (1943 was 24,624 engines) While Chevrolet built 4.033 in 1942 and 11,842 in 1943, both companies engines were single stage engines, mostly for B-24s. Chevrolet built another 11,572 R-1830s in 1943 for C-47s and PBYs and a few other planes.

Buick and Chevrolet had both been brought into the production scheme in late 1940 or early 1941.

This is why the war was fought (for the most part) with the planes it was fought with historically. Some of the intermediate planes, like the B-33A were going to show up too late, or in not enough numbers soon enough or by waiting what was hoped to be mere months, a much better plane could be built.

The same month that the B-33A was transformed on paper to a 4 engine aircraft the USAAF ordered 250 B-29s. The order was increased to 500 in Feb 1942 and another 1000 planes were ordered in March of 1942.
Granted in Jan of 1942 402 B-33s had been ordered. But none were near flying by Dec 1942 when the program was canceled.

Switching to R-2800s does dodge the question/s of the R-2600s (actual power and reliability) but doesn't do a whole lot for availability.
Ford Built single stage engines which are probably the ones going into a turbo bomber. Nash Kelvinator built two stage navy engines. P&W Kansas City and Chevrolet built C series engines but not really in time to power substitute bombers over Germany. P&W Hartford never built more than about 8300 R-2800s in one year which is certainly not going power a fleet of four engine bombers no matter how many other planes you cancel.

You want an intermemdiate bomber between the B-17/B-24 and the B-28 you had better swipe one or more of the engine plants dedicated to the B-17/B-24 program and retool it to the desired engine in 1941-42.

What the Air Force did know in 1940-41 was that the existing R-2600 (the 1600hp one) didn't take well to turbo charging (lots of overheating problems) and the R-2800 was an unknown quantity in that regard. One thing to gamble on one fighter type, another thing to pin the strategic bomber force on an unkown. just look at what happened with the R-3350 and the R-3350 was, in 1937-40 about 6 months ahead of the R-2800. Wright got sidetracked and when they went back to the R-3350 they just about started over.

Also the B-33A figures are estimates and some of the B-17/B-24 figures are operational, not even "test" numbers. B-17s. depending on weight and other factors coulspost top speeds of 300mph even in the G version with chin turret.

 

[hobbes154]

I submit that getting down off our high horse and admitting that our airmen could possibly someday encounter an enemy plane that outperforms theirs, and teaching them what to do about it would have been more effective and less of a strain on the resources than chasing the last 2% of performance.

Well sure, training boom & zoom, Thatch weave + skip bombing is probably more useful than any realistic technical improvements in this timeframe. But it's less fun to argue about. (And the high altitude performance of a P-43 over an Allison single stage, or the range of even a P-51A is more than 2% extra.)

As a general comment, I thought we were assuming a point of departure in 1938 so we could make reasonably big changes by 1942. According to this maybe just killing the Curtiss Tornado and keeping Rudy Daub on the R-3350 could have solved a lot of problems (though again, probably not paying off by 1942): Superbomber's Achilles' Heel.

Also, less Spit IXs or P-40s (or A-36s) for more P-51s seems like a pretty good bargain in hindsight.

 

[XBe02Drvr]

Also, less Spit IXs or P-40s (or A-36s) for more P-51s seems like a pretty good bargain in hindsight

But given the depression era pace of aeronautical development, the P51's bolt out of the blue quantum leap in airframe design, going from napkin sketch to flying machine in record time, was hardly foreseeable in 1938. Certainly not something plans could be based on. And don't you go messing with the Brits and their beloved Spits.

 

[MikeMeech]

But given the depression era pace of aeronautical development, the P51's bolt out of the blue quantum leap in airframe design, going from napkin sketch to flying machine in record time, was hardly foreseeable in 1938. Certainly not something plans could be based on. And don't you go messing with the Brits and their beloved Spits.

Hi

There was no way the P-51 could be delivered earlier, it only happened because of the British Purchasing Commission requirement and British 'hard cash', so basically no USAAC input for the design. The Merlin powered version was due to the work at Rolls-Royce on fitting it to the Mustang airframe with the details then sent to North American. A requirement for it from the US cannot be moved forward for a 'What if' as there was no 'US requirement' until the British had bought and used it. As for the 'Spits' US designs were not instead of British production it was always an 'as well as', orders in the USA prior to and in the early war years was to provide additional equipment as British factories had a lot of work in hand plus their own expansion programme.

Mike

 

[Shortround6]

The Merlin powered version was due to the work at Rolls-Royce on fitting it to the Mustang airframe with the details then sent to North American

Not quite, work was being done in both countries at the same time.

July 14th 1942, RR makes a preliminary study.
July 25th, NA gets a contract to convert two P-51 airframes.
Aug 1942 a Prototype installation is made in a P-51 airframe
Aug 1942 AUg 1942, five Mustang Is are sent to RR and modifications start.
Oct 13th The first of the five Mustangs in England makes it's first flight, pieces fall off.
Oct 16th, 6th flight is made in England.
Nov 30th, NA First flight by XP-51B, flight ends in over heating.
Dec 1942, NA resumes test flights with new radiator design.

RR Mustang X

RR may have sent information and engineering data to North American. Maybe NA sent some back(?) but basically there were two separate programs going on at the same time thousands of miles apart.

 

[hobbes154]

But given the depression era pace of aeronautical development, the P51's bolt out of the blue quantum leap in airframe design, going from napkin sketch to flying machine in record time, was hardly foreseeable in 1938.

Depression era pace was pretty damn fast by any subsequent standards. Or even prior standards:

The Army Air Corps' final Boeing and Curtiss biplane fighters of 1931 differed very little from the designs of 1916. ... Increased performance came from increased power, not design refinement.
- Wings & Airpower (Jan 2001) p.34

I think you could foresee in 1938 that an airframe designed in 1940 (P-51) would be better than an airframe designed in 1934 (P-36). Certainly NAA were confident they could build a better mousetrap or it wouldn't have happened in the first place.

Anyway if we're not allowed to use hindsight, what is the point of this thread?

 

[XBe02Drvr]

I think you could foresee in 1938 that an airframe designed in 1940 (P-51) would be better than an airframe designed in 1934 (P-36).

Of course progress was to be expected, in its normal evolutionary way, but it was the happy coincidence of several ground breaking innovations in drag reduction with the optimum powerplant in an airframe that could lug the fuel for a strategic combat radius, that appeared at the right time to fulfill an unforseen need that couldn't have been predicted back in 1938.

 

[hobbes154]

Of course progress was to be expected, in its normal evolutionary way, but it was the happy coincidence of several ground breaking innovations in drag reduction with the optimum powerplant in an airframe that could lug the fuel for a strategic combat radius, that appeared at the right time to fulfill an unforseen need that couldn't have been predicted back in 1938.

The Mustang has about 10% less drag than the Spitfire, therefore roughly 10% more range on the same fuel. That's a useful improvement but not off the charts. Interesting argument that the Spit could have taken enough fuel to be a useful escort fighter: Escort Spitfire - a missed opportunity for longer reach? - Royal Aeronautical Society.

I also don't think a long range fighter (or even bomber escort) is such an unthinkable idea in 1938 - it's the self escorting bomber concept that looks optimistic in hindsight. After all the Lightning (first flight 1938) could on paper have done the same job as the Mustang, it was just the turbo and compressability problems that stopped it.

 

[XBe02Drvr]

After all the Lightning (first flight 1938) could on paper have done the same job as the Mustang, it was just the turbo and compressability problems that stopped it

Turbo and compressibility. Two of the issues that just were "not quite ready for prime time" in 1938. And fighters were thought of then as single engine, single seat, but it's been pretty well established on this forum that the engine technology just didn't exist then for single engine fighters to be competitive and carry the fuel for long range escort. Hence the P38, which was arguably just about as maneuverable as a twin could hope to be.

 

[Shortround6]

Interesting argument that the Spit could have taken enough fuel to be a useful escort fighter: Escort Spitfire - a missed opportunity for longer reach? - Royal Aeronautical Society.

I seem to recall that that article tended to ignore a few things. It has been brought up several times on this forum.

Two of the issues that just were "not quite ready for prime time" in 1938.

not quite ready for prime time in 1941-42 either:0

 

[tomo pauk]

Turbo and compressibility. Two of the issues that just were "not quite ready for prime time" in 1938. And fighters were thought of then as single engine, single seat, but it's been pretty well established on this forum that the engine technology just didn't exist then for single engine fighters to be competitive and carry the fuel for long range escort. Hence the P38, which was arguably just about as maneuverable as a twin could hope to be.

not quite ready for prime time in 1941-42 either:0

Those funky Japanese probably didn't get our memo on unsuitability of long range fighters on 1 engine in 1938-42.

 

[XBe02Drvr]

Those funky Japanese probably didn't get our memo on unsuitability of long range fighters on 1 engine in 1938-42.

Equip a Zero with all the things Americans thought a fighter needed to have (armor, heavier armament, fuel tank protection, turtledeck rollover protection, all around airframe ruggedness), and where's your long range escort fighter?