Bomber Losses: USAAF vs RAF

[stona]

Just to clarify, my point about the P-39 was not to suggest that it could have made an escort fighter, even with auxiliary tanks (which were to be external, not sure if they were to be disposable without double checking), but that the American leadership constantly dropped the ball on the concept of auxiliary fuel tanks.
While it's true that by and large the Americans accepted the British position, that no single engine aircraft could be developed to provide an escort fighter, it was something that was discussed time and time again through the 1930s. The lack of clarity in thinking to which I referred was the inevitable fall back position, essentially that the bombers were capable of defending themselves, despite mounting evidence that this was not so.
It took until 1943 for the USAAF to finally accept this harsh reality and it very nearly derailed the American contribution to the combined bomber offensive at a time when it was not exactly going well for the British either. It took even longer for the first US fighters in Europe to be fitted operationally with drop tanks in meaningful numbers. The first was a matter of the obstinacy that Slessor had noted in Washington, the second is far less excusable as there were opportunities to develop such systems long before the US even entered the war.
Cheers
Steve

 

[drgondog]

Let's not forget that the Mustang was considered a 'British' aeroplane and was being built to a British requirement for the British services. It took a bit of convincing to get the USAAC/F to buy into it. The First P-51s, i.e. built for US needs were diverted from RAF Mustang production.

Nuuumaannn - while much of the statement is true, it should be noted that the contributions made by BPC technical review of NAA proposal were directed to self sealing tanks and armor, not the basic airframe. In the mind of Material Command, which wanted NAA to build more P-40's, the NAA entry was a bastard stepchild but NAA was very careful to design the Mustang to AAF published standards.

The first Mustang, already in production, that AAF suborned from the production line, was NA-91 Mustang IA. The IA became the P-51-1-NA with Recon Variant modified form a Mustang IA at factory, the -2-NA were Mustang IA's modified at Depots and two were retained as NA-101 XP-51B base airframes.

I only make this point to emphasize that British Purchasing Commission birthed the Mustang but did not change the proposal in ways that they did not change P-39D to P-400 with self sealing tanks and 20 mm gun - but not airframe. In the same way the British made the brilliant decision to install the new Merlin 61 into the Mustang I, NAA made the production changes to the Mustang IA to change the Cooling system, drop the wing, move carburation intake, install A-36/P-51A external wing racks, controls and fuel lines, modify upper and lower cowl to retain aerodynamic features. for serial production.

The British very much wished to license the manufacturing of the Mustang, particularly the P-51B and modify any feature they wished to better match RAF tactical doctrine. Had the Brits been able to do so, perhaps the Griffon would have been installed - but doubtful given long lead time to secure tooling - similar to P-51C or even Australia.

 

[drgondog]

To further Bill's post I looked through AHT and found, if I did the math right, that the engine installation of the P-51B/C weighed about 2992lbs (individual aircraft may vary) this does NOT include the cowling (possible the engine mounts) or the fuel system but does include controls, starter, propeller, radiator and oil system (empty).
The book does not have the numbers for the Allison powered P-51, perhaps Bill does?

"What makes this worthwhile and pertinent to this discussion, is that according to the charts, the V-1650-3 made about 1200hp at 25,000ft (61in MAP) while the V-1710-39 made about 600hp at 25,000ft. The powerplant in the P-51B/C made double the power while only going up about 33% in weight. It was this change in the power to weight ratio of the powerplant that made the escort fighter fighter possible.

SR - I look to Gruenhagen to get some clarity on the question of delta powerplant weight between V-1710-39 and Merlin 1650-3. He states the Built up weight as 1335 pounds to 1710-39 and 1690 pound for 1650-3. Pure built up engine with no details for Intercooler/Radiator differences or Prop or incremental fuel lines added later for 85 gallon tank. Delta --------> 255 pounds

AHS lists "Engine (incl accessories) " as 1670 which is pretty close to Gruenhagen. While he doesn't give a detailed build up for Basic weight of P-51-1, he represents P-51-1 Basic Weight as 7050 and P-51B as 7325. ----------> Delta 275 pounds for every difference including Prop, Colling system and engine section. So, Gruenhagen differs by 20 pounds from AHS without showing his (Gruenhagen) build up. (The P-51-1 20mm gun inst'l vs 50 cal in P-51B-1 is another factor). I have the weights and balances but pretty lazy at the moment to extract the details.

The Power Available to Power Required Delta between the P-51/A and P-51B above 15,000 feet was dramatic for a couple of reasons; 1.) the Thrust Hp of the Merlin/4 blade prop was greater than the Allison/three blade system, 1.) Not only the Thrust HP delta increased with altitude above 15000 feet but also exhaust thrust contribution and Ram Effect of the Merlin/P-51B-1.

I agree tour thesis about the A6M in contrast with P-51B/D. The high altitude cruise requirements to maintain escort in ETO pushed the envelope for required optimal cruise beyond the nominal 'best cruise altitudes/speed' for F4U/P-38/A6M/F6F' - also reduced P-51B but much less impact on Miles/gallon between 15,000 and 25,000 feet.

 

[Shortround6]

I have no idea why the US resisted the use of drop tanks as they had used quite a number of detachable even if not drop-able auxiliary fuel tanks in the early/mid 30s. You can find pictures of Curtiss P-6 fighters with and without tanks, Same for Boeing P-12s and their navy equivalent. Curtiss A-12s used them, as did the Curtiss Hawk III, perhaps others?
Some may have been drop-able in flight, others not?
Perhaps some bad experiences?

 

[drgondog]

I have no idea why the US resisted the use of drop tanks as they had used quite a number of detachable even if not drop-able auxiliary fuel tanks in the early/mid 30s. You can find pictures of Curtiss P-6 fighters with and without tanks, Same for Boeing P-12s and their navy equivalent. Curtiss A-12s used them, as did the Curtiss Hawk III, perhaps others?
Some may have been drop-able in flight, others not?
Perhaps some bad experiences?

SR - None of the tanks were designed for combat, pure ferry tanks and MC didn't embark on Spec/Bid/Test/Contract for 60, 75, 110 and 160 gallon tanks until after Arnold February 1942 Conference. MC forbade the use of external tanks for any purpose other than Ferry in non-combat zones prior to the introduction of the 'new tanks' which Kelsey clearly violated (and confessed to Arnold) for P-38 ferry to UK

 

[Peter Gunn]

Man I'm going to feel stupid for asking but the difference between ferry tanks and drop tanks is...?

I assume one is pressurized perhaps?

 

[drgondog]

Man I'm going to feel stupid for asking but the difference between ferry tanks and drop tanks is...?

I assume one is pressurized perhaps?

Yes. But certain other features to be leak proof were also incorporated.

 

[stona]

The issue for me is that the 200 gallon (paper) belly tank for the P-47 wasn't tested and cleared for production until July 1943.
The 84 gallon (metal) belly tank wasn't even tested until August 1943 and the 108 gallon tank not until September.

Quite apart from the missed opportunities years earlier (and the Americans were by no means the only ones guilty of this) the realisation that something really had to be done didn't dawn until the US bombing offensive was on the verge of failure. It was a message rammed home in no uncertain terms with the losses on the Schweinfurt-Regensburg raid in August. This may have been a 'Saul on the road to Damascus' moment, rather like the Butt report was for the British, in the sense that it was suddenly obvious that what they were doing wasn't working or going to work.

Cheers

Steve

 

[drgondog]

The issue for me is that the 200 gallon (paper) belly tank for the P-47 wasn't tested and cleared for production until July 1943.
The 84 gallon (metal) belly tank wasn't even tested until August 1943 and the 108 gallon tank not until September.

Quite apart from the missed opportunities years earlier (and the Americans were by no means the only ones guilty of this) the realisation that something really had to be done didn't dawn until the US bombing offensive was on the verge of failure. It was a message rammed home in no uncertain terms with the losses on the Schweinfurt-Regensburg raid in August. This may have been a 'Saul on the road to Damascus' moment, rather like the Butt report was for the British, in the sense that it was suddenly obvious that what they were doing wasn't working or going to work.

Cheers

Steve

Actually Steve - the initiative to seek combat tanks was an outcome of Arnold's Fighter conference in February 1942. The first combat tank was not the 200 gallon monstrosity, but the 108 gallon tank in September. It also required a field mod to pressurize. The last combat tank approved (of four priorities) was the 160 steel tank initially made by Lockheed.

The 8th Service Command/Hough were the drivers for the field external tank mods in summer 43 and Barney Giles, Arnold CoS was the driver for internal fuse tank increases at same period.

The 'alarm bell' was ringing quite loudly in the same mid 1943 timeframe, not during the Arnold Fighter conference more than a year earlier. The YB-40 was a desperate short term - easy mod sol'n - that didn't work, the P-51B production reached 100 in that period but clearly not yet operational in ETO, the P-38 operation reliability was a shambles - but offered some promise before deployment exposed the issues post Schweinfurt.

Even Eaker and Spaatz saw the handwriting on the wall - but Eaker held out to the idea of attrition if he could just keep 600 bombers in the inventory - for which I believe was key reason to promote him 'out' of ETO.

 

[nuuumannn]

I only make this point to emphasize that British Purchasing Commission birthed the Mustang but did not change the proposal in ways that they did not change P-39D to P-400 with self sealing tanks and 20 mm gun - but not airframe.

Hi Bill, absolutely yes. My point was that there were prevailing attitudes within the USA that pointed to the fact that the Mustang was a 'British aircraft', so interest needed to grow from within the service (the USAAC) based on evidence, rather than just grabbing the thing and running with it. As we all know, it took time for the Mustang to gain a foothold, hence my response to your statement, which I was essentially agreeing with, that the P-51 was not going to be put into US service any sooner than it was at that time.

The British very much wished to license the manufacturing of the Mustang, particularly the P-51B and modify any feature they wished to better match RAF tactical doctrine. Had the Brits been able to do so, perhaps the Griffon would have been installed - but doubtful given long lead time to secure tooling - similar to P-51C or even Australia.

Yes indeed. Of course opening up Mustang production in Britain then raises the inevitable questions of by whom (I think Gloster was mooted), where and by consequence what get's displaced in favour of the Mustang and what impact does that have on things, but that's a different discussion for a different thread.

 

[Koopernic]

Man I'm going to feel stupid for asking but the difference between ferry tanks and drop tanks is...?

I assume one is pressurized perhaps?

On the early Me 109E an external ferry tank could be carried but it couldn't be jettisoned and the pilots couldn't use them for combat. That's what I've always considered a ferry tank on a fighter. Some Me 109E1/B even had a bomb rack but weren't plumbed for fuel or the plumbing disconnect to allow jettisoning wasn't developed and tested. This is all rather odd since the Heinkel He 51 had drop tanks and was used during the Spanish civil war and had drop tanks. There is no way the Luftwaffe could have won the air battles over Britain in 1940 without drop tanks yet apart from small numbers drop tanks weren't the standard till the Me 109E7 which arrived in small numbers at the end of the so called BoB where they could make no difference. The E7 was a very successful aircraft because of its bomb rack and drop tank.

The function of the Luftwaffe was to support the Army and as Germany lacked oil and resources and would always loose a long term war a fast and rapid war called Blitzkrieg or (Breakthrough by the British stragegists that invented it) was needed. A fast flying, fast climbing aircraft was needed to intercept at her borders and gain air superiority over the battlefield.

These were the ideas that dominatated. When WW2 started Germany had 8 Freya radar stations in operation (plus a few naval port based Seetakt and mobile Freya). This had risen to 20 by the Battle of France. Radar changed the Paradgyne to one where forcefull interception of the bomber was inevitable and this may not have had time to sink in yet neither in the Luftwaffe, RAF or USAAF.

It seems likely others in the USA had the same short coming and the drop tank, already technically proven, was eschewed.

Besides there was a reasonably long ranged USAAF pursuit aircraft, the P-38. It was an odd ball design whose thick inner wing (to create fuel storage space) helped create all manner of aerodynamic problems that delayed its entry into service.

 

[Peter Gunn]

Thanks Bill and Koop, you know, I almost hesitate to post here anymore, you guys all make me feel real dumb most of the time.

So I'll follow the old "keep my mouth shut and ears open" rule, I must say though I sure do learn a lot here.

 

[drgondog]

On the early Me 109E an external ferry tank could be carried but it couldn't be jettisoned and the pilots couldn't use them for combat. That's what I've always considered a ferry tank on a fighter. Some Me 109E1/B even had a bomb rack but weren't plumbed for fuel or the plumbing disconnect to allow jettisoning wasn't developed and tested. This is all rather odd since the Heinkel He 51 had drop tanks and was used during the Spanish civil war and had drop tanks. There is no way the Luftwaffe could have won the air battles over Britain in 1940 without drop tanks yet apart from small numbers drop tanks weren't the standard till the Me 109E7 which arrived in small numbers at the end of the so called BoB where they could make no difference. The E7 was a very successful aircraft because of its bomb rack and drop tank.

The function of the Luftwaffe was to support the Army and as Germany lacked oil and resources and would always loose a long term war a fast and rapid war called Blitzkrieg or (Breakthrough by the British stragegists that invented it) was needed. A fast flying, fast climbing aircraft was needed to intercept at her borders and gain air superiority over the battlefield.

These were the ideas that dominatated. When WW2 started Germany had 8 Freya radar stations in operation (plus a few naval port based Seetakt and mobile Freya). This had risen to 20 by the Battle of France. Radar changed the Paradgyne to one where forcefull interception of the bomber was inevitable and this may not have had time to sink in yet neither in the Luftwaffe, RAF or USAAF.

It seems likely others in the USA had the same short coming and the drop tank, already technically proven, was eschewed.

Besides there was a reasonably long ranged USAAF pursuit aircraft, the P-38. It was an odd ball design whose thick inner wing (to create fuel storage space) helped create all manner of aerodynamic problems that delayed its entry into service.

Koop - the P-38 airfoil was the same as the F4U/F6F/FW190 --------->NACA 23016, NACA 23018, NACA 23015.6,NACA 23015
and the F8F had NACA 23018

All had Mach tuck issues at Mcr, all in the same range of dive velocities - and the P-38 wake turbulences issue was due to lack of filet between wing and fuselage. The venturi effect between boom and fuselage was the factor that accelerated the attainment of Mcr, not the airfoil thickness per se.

 

[stona]

"The first combat tank was not the 200 gallon monstrosity, but the 108 gallon tank in September. It also required a field mod to pressurize."

I hate to disagree, but I think the timeline I gave was correct. It is based on the 8th Air Force's own reports.

According to those reports, final tests on the 200 gallon 'pressed paper' tank took place at Bovington on 7th July 1943. The report notes that
"As a result of these tests the Bowater Lloyd Co.(manufacturers of the tanks and fairings) the British Thermostat Co. (manufacturers of the pressure relief valve) and BAD (manufacturers of the rack) have already been given the go-ahead for full scale production."

On 17th August
"The 75 gal. (actually 84 gallons) metal teardrop tank was installed and today was flight tested and jettisoned..."
It was decided to convert the 56th FG as soon as possible as they already had the relevant "Republic two point suspension kits" available and because there was expected to be a shortage of the 200 gallon tanks.

A report of 3rd September noted
"Installation and flight tests were conducted with the 108 gal. metal belly tank installation on P-47, 2 September 1943."
Various problems with the installation were discovered, but the conclusion was that once these were addressed the tanks would be "satisfactorily acceptable as a production auxiliary belly tank for the P-47 airplane."

I believe that the 200 gallon monstrosity was first, if only by a couple of months!

Cheers

Steve

 

[Clayton Magnet]

Had the Brits been able to do so, perhaps the Griffon would have been installed

A Mustang III with 2000 horsepower would have been quite the beast

 

[Shortround6]

The 200 gallon paper tank was used first but problems prevented really widespread use or a large increase in radius, it seems that the tanks were only part filled as there were feed problems at high altitude? It seems the tanks were only used for the climb out (not take-off?), forming up and initial cruise and then dropped as the planes climbed past 15,000, on a later operation they were dropped at 22,000ft.
It could take P-47 50-70 gallons just to climb from sea level to 20,000ft so this was a good boost but not the one that a 200 gallon tank would suggest.
They were also using 75/85 gallon tanks from P-39s/P-40s and 10,000 tanks ares shipped from the US during this time period Late August/early September. I am not going to argue about dates shipped and dates received

 

[Koopernic]

In regard to the issue of Oboe Bombing by the B-17 and in answer to Shortround6, Stona, Wuzak, drgndog etc etc.

Fist I'd like to note that the USAAF never gave up its ideal of precision and there was recognition of the limits of visual bombing but the USAAF wouldn't compromise its tactics or strategy. It's likely at an atavistic level it wouldn't comprise its ideals or morality by bringing in under developed inaccurate solutions, it would rather operate in daylight an retain the hope and ideal of precision even though clouds and weather eliminated this perhaps 80% of the time in winter. There is evidence it worked in as far as Hermann Goerings Post war statement that US daylight raids often destroyed equipment that could not be replaced wheres housing could be replaced. We're likely dealing with a statistical issue where US daylight raids occasionally did achieve their ideals of precision but this success is swamped by averages.

Consider the "Shoran" blind bombing and navigation system that has its inception to 1938 (contract awarded in 1940). It worked on similar principles to Gee-H but was entirely an US development. Its deployment could certainly have been accelerated. SHORAN - Wikipedia

You can see this dedication to precision also in the AN/APQ-7 "Eagle" radar dating to 1941 which is the only WW2 ground mapping radar that truly can be called a blind bombing system rather than a navigation aid.

To Stona. I'm not great believer in the war era H2S. The 9cm versions shouldn't have been introduced into service and reserved for submarine hunting as was argued at the time and only the 3cm version with gyro stabilisation antenna showed value outside of detecting the coast. Images taken of the 9cm H2S PPI scope that are genuine and not overlayed by maps and lines are quite poor.

Oboe itself offered a 50 yard accuracy and Gee-H a 150 yard accuracy. This is the measurement accuracy devoid of any other errors such as actually flying the aircraft along this path, time delays in responding to commands, bomb fall errors, low altitude cross winds effecting bomb fall, mapping errors, formation spread, targeting errors, confusion, equipment malfunction, training, fear etc.

The devil is in the details and obviously computing and automation mechanisms needed to be developed to convert the circular coordinates into cartesian coordinates that would allow easier free form bomb runs to make the system easier to use. Such systems apparently came in to use. These would eliminate the true causes of error.

The term "Mico-H" appears often in American War dairies in reference to blind bombing missions yet little is available on this system. To hazard a guess it appears to be Gee-H converted to microwave frequencies. Gee-H itself reused old Gee frequencies (around 1.5m) and equipment to accelerate deployment. New built US equipment would need no such expediency and could directly use microwaves.


Shortround6. In regards to B-17F service ceiling. You would have to admit that 9000m/30,000ft is a plausible attack altitude for a B-17F whose target is 500km/306 miles from the English coast.

10,000m/33,000ft is stretching it a bit but note that at a fuel consumption of about 1440bs/hour that less than 3600lbs is needed for the round trip after having achieved altitude over Britain and such a "B-17F" would be stripped of a moderate amount of weight, such as the waist gunners and the nose guns bar one 30 Caliber.

The Luftwaffe would be hard pressed to intercept in 1942 or even 1944. Ju 88R with their BMW 801 converted to run of Nitrous Oxide kits developed for the Ju 88S1 in the latter half of 1942 or Me 109 without radar but directed by Wurzbug radar. Both have severe operation limits.


The USAAF did have a escort fighter. It was called the P-38 and although it exhibited problems these were resolved. It at least shows a commitment to the escort fighter and the appreciation of its need even if the implementation was somewhat protracted.

 

[drgondog]

"The first combat tank was not the 200 gallon monstrosity, but the 108 gallon tank in September. It also required a field mod to pressurize."

I hate to disagree, but I think the timeline I gave was correct. It is based on the 8th Air Force's own reports.

According to those reports, final tests on the 200 gallon 'pressed paper' tank took place at Bovington on 7th July 1943. The report notes that
"As a result of these tests the Bowater Lloyd Co.(manufacturers of the tanks and fairings) the British Thermostat Co. (manufacturers of the pressure relief valve) and BAD (manufacturers of the rack) have already been given the go-ahead for full scale production."

On 17th August
"The 75 gal. (actually 84 gallons) metal teardrop tank was installed and today was flight tested and jettisoned..."
It was decided to convert the 56th FG as soon as possible as they already had the relevant "Republic two point suspension kits" available and because there was expected to be a shortage of the 200 gallon tanks.

A report of 3rd September noted
"Installation and flight tests were conducted with the 108 gal. metal belly tank installation on P-47, 2 September 1943."
Various problems with the installation were discovered, but the conclusion was that once these were addressed the tanks would be "satisfactorily acceptable as a production auxiliary belly tank for the P-47 airplane."

I believe that the 200 gallon monstrosity was first, if only by a couple of months!

View attachment 471022



Cheers

Steve

Steve - you will note that the 200 gallon tank test (and ops) you pointed to for Hough July test pointed to 'non-pressurized' which by definition is not a combat tank. The 200 gallon tank would not function above 18-20K and jettisoned in combat despite 8th FC saying 'retain'.

It took another several weeks before Service Cmd modified engine to provide pressure pump to the externals. You are right about the 75 gallon tank preceding the 108 but the key was the pressure pump mod that were performed at BAD1 , then BAD2 for the Mustang before the mid block P-51B-5 arrived with factory fix in January, 1944.

 

[drgondog]

A Mustang III with 2000 horsepower would have been quite the beast

with Merlin 100 - it was a beast. but only a few modified by RAF to chase V-1. P-51H w/2200 Hp was also a beast

 

[Koopernic]

Without pressure there is also no suction to raise the fuel.