Spitfire/Hurricane etc and drop tanks
 

It’s well known that until the P51 bombers going to Germany from England didn’t have an escort with the range to accompany them for the entire mission


The Mustang had a large fuel capacity even without drop tanks but until it came along why didn’t the allies fit them on other types such as the Spitfire, Hurricane, P47 and others ?


They couldn’t have gone as far but they could have stayed with the bombers a lot longer ?

They did have them on other types - the Hurricane had 44 gallon drop tanks, the Spitfire had several types of tank it could carry, and drop tanks were available for use on the P-47 by the summer of 1943.

Also remember that it wasn't until the summer of 1943 that the USAAF was fully convinced that escort all the way was required; faith in the combat box with a formation protected by dozens of heavy machine guns remained fairly high to begin with. I forget when the first USAAF Mustangs were fitted with drop tanks

One view re Spitfire.

https://www.aerosociety.com/news/esc...-longer-reach/

A well researched opinion of adoption of drop tanks by the USAAF here:

Interesting article @megan, I had no idea about the drag differential between a P-51 & and a Spitfire. Quite an eye opener! The cooler drag in particular is interesting, even with the 'meredith' radiators, the difference is that high?

In Paul Stoddart's article, he references use of the rear tanks making the Spitfire directionally unstable; didn't the P-51 also have this problem, and wasn't the guidance to always use the tanks in the order rear -> drop -> main? It wasn't isolated to these aircraft though, I remember reading about use of certain tanks in the Blackburn Firebrand being forbidden due to their propensity to 'spin in under power'

i recall an article by the late Hoof Proudfoot describing his first "ferry flight" in a P-51D, from Geneva to the UK; he used main tanks first and it became somewhat squirrelly longitudinally.

Although the article only mentions the cooling drag, the P-51 had a new, laminar flow, wing section. I gather there is some question about how far such wings achieved their theoretical gains in practice, but the section and the relatively smaller wing area must have contributed quite a bit to the reduced drag.

The article seems to suggest that there was some kind of failure in not developing a long-range Spitfire, but I wonder if that was ever a realistic proposition. The RAF had reacted to the vulnerability of unescorted bombers in daylight by flying at night. The USAAF would surely have been reluctant to adopt a British fighter, even if one had been available, and the suggestion that the Spitfire might have been built in the US seems very improbable, on political grounds.

The Mustang had the advantage of being designed several years later than the Spitfire, years in which a great deal of experience had been gained; it also seems to have been one of those cases where everything came together, the only major lack being a high-altitude supercharger.

The Mustang only worked because the British replaced the Allison engine with a Merlin as an experiment.

Stilton
I have read previously (unfortunately information sources not to hand) that Leigh-Mallory was very much against using fighters as long range escorts. Something like he considered them (primarily?) as defensive tools.

The P-51 was (initially) only reluctantly accepted by the US. Many thousands of P-39s / P-40s etc, were on order & they didn’t want to disrupt deliveries of proven aircraft.

From memory, even in late 1943/early 1944, P-51B/Cs were still being assigned to the RAF & the 9th(?) AF in the intruder role. It was only when Anderson & Doolittle hoovered up all available P-51B/Cs in early February 1944 the 8th AF finally had the escort fighter they needed (& tactics & sufficient drop tanks & well trained pilots). The ‘Big Week’ was one result.

As an aside, it was ‘proven’ in tests by Wright Field that the paper-mâché tanks wouldn’t work ...

Worth noting is that there is the apparent `difference` in capacity between UK and US gallons ie
90 IMP gals =108 US GALS ; 75 IMP=90 USG etc..conversion ,Imp-US GAL -x1.2.

This is a portion of an A&AEE report on Mustang drop tanks on a Spitfire.
https://cimg9.ibsrv.net/gimg/pprune....e5dc6e7a1f.jpg

The range difference between (say) a P51D and a Mk9 spitfire was mostly the amount of fuel that they could carry....

P51 D - 180 USG (wing/main) + 85 USG (rear fuse) + 220 USG (drops) = 485 USG = 404 imp Gallons

Spitfire Mk9 - 96gal (main) +75 gal (rear fuse) + 45gal (drop) = 216 imp gallons

Guess which aircraft had the longer range ;)

Just checked in the Robert Goebel autobio 'Mustang Ace',he confirmed that they did indeed completely fill the 85usg rear tank,He says that he would take off with main (wing) tanks selected,after take off he selected the rear tank and burned that down to approx 30usg at which point he emptied the drop tanks before reselecting the rear tank to empty that !
He also said that if too much fuel was left in the rear tank (C of G too far aft) the a/c would 'tighten up' in the turn and loss of control could follow.

I have seen the P51 described as a 'Dog' with the rear tank full,but the losses due to instability problems were deemed acceptable at that time

Fareastdriver , 21st Jul 2020 01:37
The Mustang only worked because the British replaced the Allison engine with a Merlin as an experiment.

Hooie...
I’ve met multiple times with all the guys that run the Roush V12 shop in Detroit, and hands down, the Packard is their iteration of choice.
Per their critique, the original Allisons were far from ready for prime time, the British RR’s were “Hand fit, but only once“, and “never again”” while the Packards were “built to tenths, and everything still fits,” (80 Years later) engine to engine, part to part.

Based on the RAF experience using the Allison powered version for Rhubarb raids there was a USAAF suggestion put forward to retain an Allison powered version in production along side the Merlin version for the low altitude/ground attack role. Reason being better fuel economy with the Allison (longer range) as the Merlin couldn't run at the low RPM necessary. the Allison was more bullet proof, averaging 1,500 hours between main bearing failures vice 5-600 on the Merlin. The RAF removed the automatic boost controller so they could extend the 44" limit out to an approved war emergency 56". On operations the RAF operated for up to 20 minutes full throttle at sea level (72") without hurting the engine. The aircraft was faster than the 109 and 190 of the time (May 1943) and the rule was not to enter combat, but outpace the enemy by "running away" as it were. The ground attack objective being seen as more important. Even though the RAF Allison version remained in service right up to VE Day and was involved in D Day and subsequent operations, continued production ceased with the Merlin introduction. Merlins used for the Reno races use Allison con rods because of their better ability to handle the stress.The difference is down to the implementation of the Meredith design. The Spitfire intake was swallowing the boundary layer, whereas the F-51 inlet was positioned out of the boundary layer, and because of the larger radiator in the -51 the air passing through had a greater dwell time so the air temperature was able to be raised to higher temperature. The reason why there was a proposition to give the Spitfire the -51 style set up.

That continued with the British automobile engines until the mid fifties. The cylinder block would have stamps on it showing 010/015/020 on each bore showing what oversize piston rings to fit. The crankshaft would also have the same treatment.

Working on American engines you just dropped in the correct part number.

The American built Sikorsky S76 helicopter is known in the maintenance trade as the Shimkorsky, it's French built equivalent the Dauphin has minimal shimming and a lot less buggering about.
Lessons lost?

Here we go again. The myths that surround the Merlins built by Packard still swirl around. Believe me, I worked on Merlins in the 1950s (I was a graduate apprentice in the Rolls-Royce Hillington factory) and one day we decided to see if a supercharger built in America would fit an engine built in the UK. There had been a lot of nonsense talked about Packard 'tightening up the tolerances' etc. We had dozens of Packard 66s out in the yard in the original packing cases (the batch built right at the end of the war and never needed), and brought one into the experimental shop, and removed the supercharger. We brought a supercharger off one of our Merlins and having inserted the locating dowels, we offered it up to the Packard. Perfect fit - it just slid on to the dowels with no problems. We didn't go as far as bolting it on and testing the engine, but I have no doubt it would have worked fine. We overhauled a batch of these 66s and they were fitted to Heinkel 111s which the Spanish Airforce needed when the German engines reached the end of their lives, There was NO material difference between a Hillington engine and a Packard one if you excepted the makers plate. Packard were issued with a complete set of gauges for every part of the Merlin, and I have no doubt they used them.

Is this the same Leigh-Mallory that spent several years frittering away experienced ilots and aircraft on fighter sweeps, rhubarb and other offensive actions that ultimately did little to beat the Luftwaffe?

If you read Stanley Hooker's autobiography it explains that the early Rolls-Royce Merlin engines were built to their own drawing/tolerance standards, but when the Ford factories were engaged to build Merlins they initially said that they couldn't to the RR drawings. RR staff (might have been Hooker himself) are reputed to have said "I suppose you find our tolerances too difficult" to which the Ford response was "on the contrary, your tolerances are far wider than we use in motor cars, if we build to them nothing will fit". As a result Ford redrew all the RR Merlin drawings to ensure proper mass-production tolerances and subsequently these were the drawings used by Packard. The increasing reliability of Merlins as WW2 carried on is probably indicative of these manufacturing improvements as well as the RR method of eliminating weaknesses serially by running at increased power until the next thing broke. The magneto-drive skewgear failures were later traced to the tolerance build-up of the assembly being inadequate.

Packard also provided a lot of information to Britain about the metals to use in the big-end plain bearing shells, at the time this was very secret stuff and even now there is a lot of incorrect information about. I had a long chat with one of the Shuttleworth collection engineers about it, he said that they use parts that are essentially identical to the Packard specification and have no more trouble whereas older engines such as the Kestrel in the Hawker Hind are much more problematic and subject to erosion if the engine runs too hot because the wind down radiator is not wound down far enough and doesn't provide enough cooling.