Page 1 of 3 123 LastLast
Results 1 to 10 of 30

Thread: Near-supersonic Spitfire incident, 1952

  1. #1
    Join Date
    May 2010
    Posts
    42
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default Near-supersonic Spitfire incident, 1952

    A Spitfire has been cited as achieving the highest Mach number of any piston engined aircraft. On 5 February 1952, a Spitfire reportedly became out of control during a high altitude flight and achieved Mach 0.96 and 600kts (691mph) in a vertical dive.

    Can anyone provide any details about this incident or direct me to a source?

    Thanks,
    David Isby

  2. #2
    Join Date
    Nov 2007
    Location
    Wiltshire
    Posts
    2,493
    Thanks
    0
    Thanked 2 Times in 2 Posts

    Default

    David,

    I believe you are thinking of a meteorological ascent in a Spitfire PRXIX (PS852) flown by Flt Lt Ted Powles at Kai Tak on 5 February 1952. He reached 51,550 ft before having to descend rapidly due to depressurisation. From instrumental readings it was calculated the aircraft reached 690 mph during the dive. The incident is descibed 'Spitfire - the Biography' by Jonathan Glancey.

    There are several accounts, mostly saying the same thing on the Internet; for instance see:

    http://forum.keypublishing.com/showthread.php?t=69838
    http://warbirdsforum.com/showthread.php?t=1409
    http://www.lincolnshirelife.co.uk/uploads/files/aspects_of_lincolnshire/aspectsoflincolnshire-0208.pdf
    http://www.mkiwi.com/New+Zealand+picture/Auckland+Photos/Spitfire.html

    Brian

  3. #3
    Join Date
    Nov 2007
    Posts
    942
    Thanks
    0
    Thanked 1 Time in 1 Post

    Default

    There was also some discussion on the TOCH forum on the subject. It must be noted that the similar, and entirely confirmed results were achieved by Fuehrer Martindale while on series of tests made during the war.

  4. #4
    Join Date
    Nov 2007
    Location
    Wiltshire
    Posts
    2,493
    Thanks
    0
    Thanked 2 Times in 2 Posts

    Default

    Er - 'Fuehrer' Franek? Don't think Squadron Leader Martindale would be too pleased!

    Brian

  5. #5
    Join Date
    Nov 2007
    Location
    Canada, eh
    Posts
    1,217
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    I would be very interested in any detailed reports of "the instrument readings" used to support this claim. Conventional airspeed indicators and the associated pitot static heads can become very unreliable approaching Mach 1. This has resulted in several unsupportable claims by aircraft of that generation becoming "nearly supersonic" when clearly they would not have survived such an event. I'm sure that they could have encountered compressibility effects, but on a relatively thick wing (compared say, to an F-104) this can start around Mach .7 to .8, or about 370 to 420 knots true airspeed at high altitude.

  6. #6
    Join Date
    Nov 2007
    Posts
    942
    Thanks
    0
    Thanked 1 Time in 1 Post

    Default

    Brian
    I do not know if he was pleased, but it is, how he was called by the personnel!
    Bill
    Measurements were made by barograph, and recalculated onto speed. Much more precise than a Pitot tube.

  7. #7
    Join Date
    Nov 2007
    Location
    Wiltshire
    Posts
    2,493
    Thanks
    0
    Thanked 2 Times in 2 Posts

    Default

    Franek,

    Are you sure re the barograph? I wasn't aware that barographs were used for met soundings. If the barograph was in the cockpit (can't think where else it would be) it would be ineffective due to the cockpit being pressurised. I always thought that pressures were obtained from a sensitive altimeter calibrated for met work.

    Anyone read Glancey's book?

    Brian

  8. #8
    Join Date
    Nov 2007
    Location
    Canada, eh
    Posts
    1,217
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Default

    Can some of the met guys tell me what a barograph would have measured on these flights? Was it just ambient static pressure?

  9. #9
    Join Date
    Nov 2007
    Posts
    942
    Thanks
    0
    Thanked 1 Time in 1 Post

    Default

    Hi
    Most popular altimeters are barometric ones, and they measure static pressure. They could be very precise, but require calibration prior to the flight, hence qnh and qfe settings. Barograph would make a graph of pressure in function of time, and knowing other parameters like temperature, this allows to recalculate it onto a speed of the aircraft. Perhaps it is not clear from my writing, but actually is quite simple.

  10. #10
    Join Date
    Nov 2007
    Location
    Lancashire
    Posts
    524
    Thanks
    0
    Thanked 3 Times in 3 Posts

    Default

    However, all such instruments rely upon the accuracy of the readings taken, and cannot be relied upon at high Mach numbers.

    The Spitfire's wing was slimmer than those if its contemporaries, and thus it could reach a higher Mach Number before affected by the steep drag rise associated with compressibility (the Sound Barrier). It had a drag divergence Mach Number of (IIRC) 0.92, as opposed to 0.84 for the P-51 or Me262. Thus the speed reached by Martindale is entirely credible, even without being backed by sound evidence as part of a specific series of trials on terminal velocity dives.

    The speed credited to Powles is not so well backed, as drag would have exceeded thrust long before. Although conditions within the thundercloud were hardly "steady state". The aircraft may well have been travelling at close to Mdd with respect to the local air, which in turn was descending rapidly. The sum of the two speeds may have reached the total quoted, but it is somewhat difficult to see how this could be measured with the limitations of the instruments of the day.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •