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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.
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.
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 UKI 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?
Yes. But certain other features to be leak proof were also incorporated.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?
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 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
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.
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.
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.
A Mustang III with 2000 horsepower would have been quite the beastHad the Brits been able to do so, perhaps the Griffon would have been installed
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'."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
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 beastA Mustang III with 2000 horsepower would have been quite the beast