pinehilljoe
Senior Airman
- 731
- May 1, 2016
The Corsair was the first US Fighter to reach 400 mph
The P-40 was not a good fighter
The P-40 was not a good fighter
Aviation myths that will not die
- Thread starter fastmongrel
- Start date
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Shortround6
Major General
Not myths
Or depends on wording. The XF4U-1 was supposed to have hit 400mph Oct 1, 1940. insert either "single engine" or "carrier" between "first" and "US fighter" and it is true.
XP-38 had 11 hours and 50 minutes of flight time before departing on the cross country flight that ended in the crash. It is possible in just under 12 hours of flight testing that they did a high speed of run of 400mph. Maybe somebody has the date of the 400mph P-38 flight?
How good the P-40 was as a fighter depended on the opposition. In many theaters it needed top cover by other aircraft types.
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Shortround6
Major General
Dropping leaflets that said they were going to bomb certain city/s at some point in the future could certainly have been done and probably was, even as an exercise in physiological warfare. If even a few percent of the workers leave because of leaflets that is a cheap hit to production.
Dropping leaflets with schedule of cities and dates and then keeping to it would have been a great gift to the defense.
Extremely unlikely as much of the Dresden bombing by the USAAF was done by H2X. In the last 6 months of the war only 14% of 8th AF bombing was done visually, the weather in NW Europe precluded it.
50% of bombing was done through 8-9/10th cloud and 10/10 cloud.
To give an idea of the accuracy of radar bombing in late 1944/early 1945, through 10/10th cloud just 1 bomb in 500 fell within 1000' of the aiming point, nearly 60% fell 5 miles or more from the aiming point.
These results are actually worse than Bomber Command achieved using H2S at night, probably because the 8th AF bombed from higher altitude.
Cheers
Steve
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FLYBOYJ
"THE GREAT GAZOO"
The P-38 Lightning
What was the actual maximum speed of the XP-38? To begin, it is almost certain that no attempt was made to operate the aircraft at maximum speed. The first flight almost ended in disaster when the flap operating rods broke on takeoff. There were only five other test flights used to correct the flap problem and other known defects, after which the aircraft was sent on its cross-country flight. Kelsey was a trained test pilot and the flight plan required strict adherence to specific power settings calculated to balance speed with fuel consumption. In fact, he makes a similar statement in an interview (see below).
Warren Bodie's definitive book on the P-38 has most of the answers concerning this question. The best data comes from an interview that took place several years after Kelsey's retirement. It appears that he took two sets of performance readings during the flight while at high-speed cruise. He used this to calculate what the maximum speed would be at 20,000 feet at rated power. Remember that Kelsey was an MIT engineering graduate who spent much of his time estimating the performance of new airplanes.
One of the calculations showed a maximum speed of 394 mph at 20,000 feet on 1150 hp/ engine. The other showed 399 mph at 20,000 feet if 1250 hp/ engine was used. His data and calculations were given to Kelly Johnson who came up with 403 mph at critical altitude (around 20,000 feet) on 1150 hp/ engine. Johnson also had plans to alter the design of the airplane and expected to improve the speed by around 10-mph, giving it a top speed of 413 mph. This is often quoted as the top speed of the XP-38, but as flown, it would appear to be between 394 to 403 mph. Nonetheless, this makes the P-38 the first 400-mph fighter in history.
Shortround6
Major General
So the XP-38 never actually hit 400mph in flight, it was calculated. And we are assuming that they used the correct correction factor for drag at 400mph because the P-38 famously ran into compressability problems.
The YP-38 seemed to have a bit of trouble hitting 400mph in tests even with gun ports covered.
Of course to be fair the XF4U Corsair's claim to 400mph is also a bit dubious. According to WIki that was the average ground speed on a flight from Stratford Ct (Chance Vought plant) to East Hartford (P & W Plant). The Flight was in a North East direction and that happens to be about the direction of the prevailing winds in the Area (I lived in Stratford for over 12 years) and distance between the two air fields in about 45 miles. It would take 6.66 minutes at the claimed 405 mph. Now just ho long was the engine supposed to held at max power?
Who was doing the timing? and what reference points were being used to start and stop the watch.
The plane may have averaged the 405mph But I would bet it help from a tail wind. Perhaps not to the extent of the famous 400mph Hurricane though
The YP-38 seemed to have a bit of trouble hitting 400mph in tests even with gun ports covered.
Of course to be fair the XF4U Corsair's claim to 400mph is also a bit dubious. According to WIki that was the average ground speed on a flight from Stratford Ct (Chance Vought plant) to East Hartford (P & W Plant). The Flight was in a North East direction and that happens to be about the direction of the prevailing winds in the Area (I lived in Stratford for over 12 years) and distance between the two air fields in about 45 miles. It would take 6.66 minutes at the claimed 405 mph. Now just ho long was the engine supposed to held at max power?
Who was doing the timing? and what reference points were being used to start and stop the watch.
The plane may have averaged the 405mph But I would bet it help from a tail wind. Perhaps not to the extent of the famous 400mph Hurricane though
FLYBOYJ
"THE GREAT GAZOO"
I think the 400 mph top speed came from the calculated times during the legs on Kelsey's cross country flight.
michaelmaltby
Colonel
I believe this is true .... but it's the stuff of myths
View: https://www.youtube.com/watch?v=reytu0y5efs
View: https://www.youtube.com/watch?v=reytu0y5efs
drgondog
Major
I don't believe that either Kelly Johnson or Ben Kelsey were fully aware of compressibility drag rise in 1938 (or 1941).
M 1 @ 20,500 feet at STP is 705mph. 400mph is ~ .56M. The very much cleaner P-51 compressibility factor at that speed is approximately 1.25 absolutely 'clean'. As much as I respect Kelly Johnson I would not trust a top speed performance analysis which yielded 400 mph. The approach 'back in the day' would have been a balance between Power Available and Power Required. The latter was based on Total Drag at that speed and altitude and it is very unlikely that the reasonable compressibility drag factor for parasite drag was even close.
Far more likely would be the ground speed estimates with variable west to east tailwinds. We might consider that the speed run was Not made east to west to average out the winds aloft.
M 1 @ 20,500 feet at STP is 705mph. 400mph is ~ .56M. The very much cleaner P-51 compressibility factor at that speed is approximately 1.25 absolutely 'clean'. As much as I respect Kelly Johnson I would not trust a top speed performance analysis which yielded 400 mph. The approach 'back in the day' would have been a balance between Power Available and Power Required. The latter was based on Total Drag at that speed and altitude and it is very unlikely that the reasonable compressibility drag factor for parasite drag was even close.
Far more likely would be the ground speed estimates with variable west to east tailwinds. We might consider that the speed run was Not made east to west to average out the winds aloft.
davparlr
Senior Master Sergeant
Ground speed estimates of top speed is, in my opinion, dismissable, if that's a word.
Shortround6
Major General
Ground speed, as measured between two points on the ground, can be very accurate. It is the way world speed records were measured. It can also be very inaccurate, all the way down to WAG territory.
World speed records require cameras and clocks that are synchronized at both the start and finish lines and flights to be made both ways within a short period of time to average the wind conditions.
Flights from airport A to airport B certainly introduce a host of variables. Synchronized clocks at each airport? Pilots wrist watch?
When was the time started? Did the plane loose altitude over the course of the flight? like drop several thousand feet over 50 miles? Tail winds were what speed at what altitude?
However even test flights are not 100% accurate until/unless correction factors are figured into the instrument readings.
Sometimes extra instruments were fitted to aircraft including things like recording barometers and temperature recorders (they recorded on paper drums)
So the proper corrections could be made to the instrument readings, like the normal altimeter and air speed indicator.
Often a new/different pitot tube was fitted to test aircraft in order to minimize errors due to pitot tube location or shape until a general correction could be worked out for production examples. Also the correction factor for the pitot tube/airspeed indicator varied a bit with the speed of the aircraft and in some cases gave higher readings than true instead of lower.
Both the P-38 and F4U were designed with the intention of being 400mph aircraft. Both wound up being 400mph aircraft, just not in their original form or using their original engines. Since due to crashes of prototypes and delays in programs they over lapped considerably the only real value in which was first would be to settle a bar bet.
World speed records require cameras and clocks that are synchronized at both the start and finish lines and flights to be made both ways within a short period of time to average the wind conditions.
Flights from airport A to airport B certainly introduce a host of variables. Synchronized clocks at each airport? Pilots wrist watch?
When was the time started? Did the plane loose altitude over the course of the flight? like drop several thousand feet over 50 miles? Tail winds were what speed at what altitude?
However even test flights are not 100% accurate until/unless correction factors are figured into the instrument readings.
Sometimes extra instruments were fitted to aircraft including things like recording barometers and temperature recorders (they recorded on paper drums)
So the proper corrections could be made to the instrument readings, like the normal altimeter and air speed indicator.
Often a new/different pitot tube was fitted to test aircraft in order to minimize errors due to pitot tube location or shape until a general correction could be worked out for production examples. Also the correction factor for the pitot tube/airspeed indicator varied a bit with the speed of the aircraft and in some cases gave higher readings than true instead of lower.
Both the P-38 and F4U were designed with the intention of being 400mph aircraft. Both wound up being 400mph aircraft, just not in their original form or using their original engines. Since due to crashes of prototypes and delays in programs they over lapped considerably the only real value in which was first would be to settle a bar bet.
What did the Germans call the P-38?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Lightning
The 38 sounded nothing like the 51...the 51 was loud...the 38 is very quiet...
So where did the Fork Tailed Devil name come from then?
Shortround6
Major General
Training manual writer for the Air Corp trying to boost Morale
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Americans...the nickname eventually ended up in the training manual
I am glad that our fellow Europeans followed the English name system rather than a nondescript number for the
forked tailed devil/lightning.
