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The RAE's Technical Note No.Aero.1501(Flight) on Improvement of Performance of Fighter Aircraft Operating Against the German Flying Bomb dated August 1944 describes improvements and results for the Mustang III:I'm trying to figure out what mods/changes the RAF used on the Mustang IIIs (and maybe IVs?) that were used to intercept V1 flying bombs. Other than running 25 lbs of supercharger boost, what other changes were made to boost performance? I do believe that 25 lbs of boost was equal to 80 in/Hg, which is what the V-1650-9 in the P-51H used (along with 90 in/Hg, which I thing equated to 30 lbs of boost).
One thing that I read did say that the V-1 Mustang IIIs were capable of 415-420 mph at 2000 ft. So I'm wondering, one, how valid is that claim, and two, what was done to get there. I'm also interested in how that compared to a Mustang III that was used by Rolls-Royce as a Merlin 100 test bed.
water/methanol gets you almost no increase in high altitude performance, and weighs a LOT. The whole point of the 51H was to be light.Why did they not work up an ADI system before the P-51H, given that round engines had apparently been fitted with wate injection well before this time?
Also, how did they deal with engine cooling in these operations? At the Reno races, run at about 10,000 feet density altitude, the racers found early on that a stock Mustang cooling system simply cannot deal with the heat loads of sustained operation at above 60 inches -- after just a few minutes the radiator exit door has to be fully open with a big loss of speed. In Reno operations nearly everyone uses "spray bars" to dump water on the radiator face -- this was not available during WWII. Did they have cooling issues back then?
Well you cant have P-51H for chasing flying bombs anyway, it was not in service until after the V1`s had ceased to be launched.I never thought about weight being a big issue with a water-alcohol system. There's a pump, regulators, piping, and of course the water itself. How much heavier was a dash 9 than an earlier engine? Seems like ADI would be useful at V-1 chasing altitudes.
Could cooling be an additional issue? If the cooling system struggled with a stock engine at high power, more power would simply make the problem worse...
I do wonder how the V-1 mods compare to what Rolls Royce did with a Mustang III that used Merlin 100 and 113 engines (quoting an entry from Wikipedia on the subject, but citing official reports):
"While North American was concentrating on improving the performance of the P-51 through the development of the lightweight Mustangs, in Britain, other avenues of development were being pursued. To this end, two Mustang Mk IIIs (P-51Bs and P-51Cs), FX858 and FX901, were fitted with different Merlin engine variants. The first of these, FX858, was fitted with a Merlin 100 by Rolls-Royce at Hucknall; this engine was similar to the RM 14 SM fitted to the XP-51G and was capable of generating 2,080 hp (1,550 kW) at 22,800 ft (7,000 m) using a boost pressure of +25 lbf/in2 (170 kPa; 80 inHg) in war emergency setting. With this engine, FX858 reached a maximum speed of 455 mph (732 km/h) at 17,800 ft (5,425 m), and 451 mph could be maintained to 25,000 ft (7,600 m). The climb rate was 4,500 ft/min (22.9 m/s) at 1,600 ft (486 m) and 4,000 ft/min (20.3 m/s) at 13,000 ft (3,962 m).[60]
One interesting problem that had for intercepting V-1's at night was the flame from the pulsejet. While the flame was easy to see at night it also made it very difficult to judge the range to the flying bomb in a tail chase - and you did not want to be too close if you hit one and it exploded, nor too far away so that the gunfire was ineffective. So they took a Typhoon and added a APQ-13 or Monica tail warning radar focused forward. When the warning light came on the pilot knew how far he was from the V-1 and thus judge much better when to open fire. This apparently was fitted only to one aircraft for test purposes.
Fwiw, see attached:Why did they not work up an ADI system before the P-51H, given that round engines had apparently been fitted with water injection well before this time?
Generally the Mosquitos patrolled along the French coast at around 8,000 ft in clear weather in an attempt to spot the flashes from the launchings and then the flames from the pulsejet. They then dived to the roughly 2,500ft (but heights were variable, with one attack occurring at 12,000ft) at which the bombs flew at 320-350mph. In other cases they were vectored out to meet them by land based radar. Other than the problems of getting on a V1's tail and closing for the attack, the third problem in completing the kill was to do it in the space of about 30 miles before it reached the gun belt on the English coast or over land between the gun belt and the balloon belt immediately south of London.Interesting. There must be some stories around about how the Mosquitoes managed. I've a very fuzzy recollection of having read something somewhere about that, although memory fails me at the moment.
".......... Rolls-Royce have done some careful test and assessment work wherein they found that the slight extra cooling effect of the injection is more than off-set by the slightly lowered thermal content of the total charge."One of those fuzzy memories- Aid for the daylight location of flying bombs by fighter aircraft: