the mustang's range arguably decided the outcome of the air war over germany. its range compared with other fighters, whether allied or axis, seemed to me like a physical impossibility. how was it done?
It's also worth noting that an 85-gallon fuel tank was inserted into the rear fuselage wfrom the B/C series - together with the wing drop-tanks mentioned by CAC, a combat range of 880 miles could be achieved.
I believe the keys were the laminar flow wing and packing a lot of gas. Most of the gas was internal and the P-51 could manage over 900 miles even without drop tanks. She was very clean aerodynamically but inline engines aren't a huge advantage there due to the need for a radiator and the P-51 had a big one. There are many who say that the radiator exit on the Mustang was designed to actually increase thrust, but I've never understood how that would be possible. Lots of radial engines fighters had very long range too, like the Zero, Hellcat and Corsair. Packing all that gas had trade off too. The tank behind the cockpit shifted the CC aft when it was full and made the plane difficult to fly and pilots used that one first. To move the CC forward again. The Zero's unbelievably long range made it almost impossible to fly when it took off with maximum fuel and it couldn’t fight or maneuver at all until some of it burned some off. The Mustang was pretty heavy, even when empty, for a land based single seater. Not as heavy as a Tempest or P-47 but still over a ton heavier than an empty Spit or 109.
Cooling drag is a large component of the parasitic drag of piston engined aircraft - whether air cooled or liquid cooled. The drag penalty in air cooled engines is largely from the increased frontal area to expose the cylinder fins to air flow, but also in the ducting of air out of the cowling. Inline engines need a radiator exposed to air flow which results in a drag penalty. The P-51 cooling system was designed to utilize the Meredith Effect. Basically a radiator at the largest area of a divergent air duct and a convergent exit duct. The radiator adds heat to the air in the duct increasing volume and velocity throught the venturi-like exit. The thrust generated offset the cooling drag reducing it to close to zero. Some claim a net positive thrust was generated, but the removal of cooling drag was the benefit.
Was it's radius really "unmatched"? The P-38 was pretty long ranged especially if one knew how to fine tune it. Likewise the P-47N had some pretty decent "legs". The Corsair and F7F weren't exactly slouches either.
In practical terms the P51 was the only fighter escort to go all the way to Berlin. That is unmatched in historic terms. .
Hopefully one of our real experten like mccoffee will chime in, but until then we might note that the first American fighters over Berlin were P-38s, of the 55th Fighter Group, on March 3, 1944. The replacement of P-38s by -51s in the escort role was due to performance and operational issues, especially at high altitudes. The distance from English airfields to Berlin, about 600 miles, is not so remarkable compared to the 900+ achieved by P-38s in the Pacific. As already noted, the P-47N, the long-range escort version of that fighter, achieved similar ranges.
Right, and the US Navy fighters could have done it too. I think they were more expensive then the P-51 though. The P-47 and the P-38 definately were more expensive.
And as earlier noted the A6M had legs easily the equal of the P-51 and quite regularly made longer round trip escort missions than London to Berlin during the Guadalcanal campaign. (At tremendous cost in pilot fatigue, which doubtless contributed to losses.) The P-51 was a great bird, but it didn't defy physics.
Yes, but the RAF did not believe in long range escorts. The Spitfire was designed as an interceptor. Photo reconnaissance Spitfires were fitted with external tanks .
That's true, but the 'interceptor' tag in the specification that resulted in the P-38 was a bit of subterfuge. The USAAC had an arbitrary limit of 500 lbs for the armament for fighter aircraft at the time the X-608 Circular Proposal was written. A heavily armed fighter was desired and the specification called for at least 1000 lbs of armament including a cannon, and a full throttle endurance of 1 hour at 20,000 feet was specified. By calling it an interceptor - a classification that didn't exist in the AAC at the time - they got around the armament weight limit. Thus the required fuel capacity and armament called for a very different fighter that the Spitfire which was intended as a point defense fighter.
From what I recall it was intended as an intercepter in any case but not a point defense one. Wasn't it intended to intercept bombers attacking the continental US?
Yes, it was intended to intercept incoming bombers. The AAC and the Navy were in dispute about who was responsible for coastal defense. From memory the AAC had to intercept bombers outside the Navy defense zone (late '30's) and thus the spec for a long range high altitude interceptor.
The P47 had a pretty descent range with drop tanks as well, as did the Corsair and the P38 as others have mentioned. I guess the kicker is going to Berlin and back. From what I've read P47s only went to Western or Northern Germany, but it didn't say they wouldn't have been able to make it to Berlin with drop tanks.
Depends... IIRC, all of the aircraft you mentioned carried quite a bit more internal fuel than the P-51 B/C/D. P-51 B/C/D: 269 gallons F4U-1: 351 gallons P-47D-25: 370 gallons P-38 J/L: 410 gallons The P-47N got it's phenomenal range because it carried 556 gallons internally. IIRC, the earlier "razorback" P-47Ds only carried some 305 gallons internally and were slow climbers, so even with drop tanks, they were unable to go to Berlin & back. However, the "bubble canopy" -25s with their increased internal fuel capacity and new "paddleblade" propeller could fly to Berlin & back with drop tanks.
It's not all about the gallons. It has almost as much to do with AC weight and drag. The P-51 carried a lot of fuel in total, had a slippery shape, laminar flow wings, etch. Jugs, while having a lighter radial engine, had that offset with way more drag in the nose and wings, and of course was a much heavier bird.