P-47 vs P-51 in a dive

Discussion in 'Aviation' started by Jenisch, Apr 8, 2012.

  1. Jenisch

    Jenisch Active Member

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    #1 Jenisch, Apr 8, 2012
    Last edited: Apr 8, 2012
    Which of them was the fastest diver?
     
  2. GregP

    GregP Well-Known Member

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    #2 GregP, Apr 8, 2012
    Last edited: Apr 8, 2012
    I believe the WWII data says the P-47 was a bit faster in dive speed, but the P-47 dive performance was in Indicated Airspeed and the P-51 dive peformance was in calibrated airspeed.

    At 10,000 feet the P-47C could dive at 520 mph IAS and the P-51 limits was 505 mpgh CAS. Little to choose.

    As an aside, I spoke with Steve Hinton about the P-47 in a dive and he said he had flown a P-47 to 25,000 feet (operating turbocharger) and had dived it vertically at full power. He said it accelerated quickly to 450 mph and stayed there ... but I didn't think to ask if it was IAS, CAS, TAS, or what, and I didn't ask at what altitude he pulled out. A strong diver from all the reports, but Steve said he expected it to be faster in a dive.

    I didn't "interview" him about it, it was a short conversation.

    Additionally, in one of the magazines he is quoted as having said the P-38F was faster than the P-38J. I aksed him about that he said that at the same power, the P-38F was faster than a P-38J or L ... but the J and L had more power availabe and so were actually faster than an F model. He said his comment was taken out of context as he was describing the P-38F as being faster than a J or L in normal cruise at the same power levels .. amd that part never made the magazine quote.
     
  3. Jenisch

    Jenisch Active Member

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    #3 Jenisch, Apr 8, 2012
    Last edited: Apr 8, 2012
    Interesting. I risk to say that maybe the P-47 he flown, a civilian version I suppose, didn't have all the weight of a wartime model and hence didn't accelerated as fast in a dive.
     
  4. Jenisch

    Jenisch Active Member

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  5. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Dive limit for the P-51B/-D was 505 mph IAS (from manual), while for P-47 it was 500 mph (from 'US 100 hundred' book).
     
  6. Jenisch

    Jenisch Active Member

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    Thanks Pauk. The little better speed of the Mustang was effect of the laminar flow wing? Anyway, the P-47 was some 3 tons heavier, so it's acceleration in the dive must have provided a decisive advantage.
     
  7. GregP

    GregP Well-Known Member

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    The "civil version" of the P-47 Steve flew has all the wartime equipment in it, including the turbocharger. The guns don't fire, but are otherwise stock, and the armor plate is still there.

    I'd venture to say it is within spittign distance of stock weight, though the ammunition doesn't have powder in it.
     
  8. drgondog

    drgondog Well-Known Member

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    The laminar flow wing has the effect of beginning the transonic shock wave near Max t/c which is ~ 40% MAC. I t had two effects - 1.) delaying wave drag, 2.) reducing/eliminating nose down pitch due to flow separation.

    The fastest I Have ever heard of a 51 dive was an RAF test in which a MK IV was at .82-.85 M (instrumentation a little fuzzy) and the aircraft had so many wringled panels and fastners fail that the a/c was written off. That was Far above the Placard speed.
     
  9. CobberKane

    CobberKane Banned

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    The RAF compared the P-47 to a number of other aircraft in 1943 - the trials are n the web somewhere sorry, as is so often the case I couldn't find the document when I was lookinf for it. I do recall that the Mustang ran away from the Thunderbolt in a dive, which surprised me. The anecdotal evidence from both sides of the conflict seems to be that the 47 was miles ahead of everything else in this area, so go figure.
    I wonder if a great part of the Thunderbolts reputation for diving comes not so much from outright speed as controllability. Maybe there were other aircraft around that dived as fast as the P-47 but without the control. I also wonder if the P-47's ability to pick up speed so quickly in the dive (and remain controllable) goes some way to answering the question as to whether it could roll with a Fw-190. The P-47 semed to everything well as high speeds and I suspect that any opponent silly enough to dive away from one would quickly enter the speed zone in which the Thunderbolt reigned, even if they were matching it for outright speed.
    One other thing I always wondered about is the P-47's reputation for firepower. It had great armament for the job; the .50's gave it plenty of punch for dealing with the fighters and light bombers it mostly flew against,and plenty of firing time to boot, but surely it was outgunned by Typhoons, Tempests and even Hurricanes in terms of instantaneous firepower.
     
  10. Juha

    Juha Well-Known Member

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    Critical Mach Number for both P-38 and P-47 was .68, low when compared many other fighters of the time, that was why both got the dive recovery flaps later on, so pilots could dive very near their planes' limit without danger that dive became unrecoverable.

    Juha
     
  11. MikeGazdik

    MikeGazdik Member

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    It seems (from my various book reading over the years) that the P-47 and P-51 were able to dive and catch any Me109 or Fw190. What are the respective dive speeds of these aircraft? I would say until the advent of the P-51, the Thunderbolt was the first single engine fighter that dove so well, so much of the talk and lore passed on are because it was the first.

    CobberKane, you bring up an interesting point.
     
  12. Siegfried

    Siegfried Banned

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    It's not so simple, the P-38 and P-47 airfoils had very poor critical mach numbers, dive recovery flaps were added under the leading edges to pitch up the aircraft to cure this problem from about 1944. The P-51 had outstanding mach characteristics and didn't need dive recovery flaps. Me 109 mach limit problems were actually traced to rudder overbalancing caused by a horn balance on the rudder. A new tall tail using a balance tab greatly increased mach limit to the point that the Me 109 was on occaision out diving the P-51D (with the bubble canopy).

    You could count on Mach 0.78-0.79 as the Mach limit for the FW 190 and Me 109.

    I'm just reading "The Focke Wulf Ta 152: by Thomas Hitchcock. Extraordinary in this book given the aircrafts very high aspect ratio is several pilots accounts of extrmely high dive speeds in the aircraft, the pilots reported flutter and wing vibration but no problems recovering and no damage.
     
  13. Jenisch

    Jenisch Active Member

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    P-40 wasn't extremely good in the dive as well?
     
  14. GregP

    GregP Well-Known Member

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    Neve heard of an Me 109 outdiving a P-51. Where did you come up with that?

    At speeds over 400 mph the flight control surfaces of an Me 109 are almost solid and it is unmaneuverable in the extreme. I have neard of many Me 109's diving straight into the ground when attempting to chase an Allied fighter in a medium to low altitude dive (from combat reports), but never out diving a P-51.
     
  15. Juha

    Juha Well-Known Member

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    Hello GregP
    there are P-51D pilots’ combat reports where they stated that 109s they were following outdove them. Most probably cause was simply that the hunted (109 pilot) took greater risks than the hunter (P-51D pilot). After all the behaviour of a plane didn’t transfer from normal to impossible instantly at the critical Mach number but became nastier and nastier when a/c approached the critical Mach number. P-51D’s critical Mach number was appr. .82 and the highest Mach Number achieved by 109 in German tests was .805 with specially modified 109F with G series wings and with the late 109 high tail. In the plane the control movement was limited to 50% of the reference movement of the ailerons. The horizontal stabilizer trim was limited in its upwards range of motion to +1°15 by a stop unit.

    Juha
     
  16. MikeGazdik

    MikeGazdik Member

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    Yes, the P-40 was very good in the dive. But I don't think It could match the P-47. And it would never have began a dive at the altitudes at P-47 would obtain, it couldn't get that high!
     
  17. davparlr

    davparlr Well-Known Member

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    Early report of P-51 (Allison) verses P-38F, P-39D, and P-47F
    P-51 Tactical Trials
     
  18. Siegfried

    Siegfried Banned

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    I pulled this of google books a few years ago:


    "My flight chased 12 109s south of Vienna. They climbed and we followed,
    unable to close on them. At 38,000 feet I fired a long burst at one of
    them from at least a 1000 yards, and saw some strikes. It rolled over
    and dived and I followed but soon reached compressibility with severe
    buffeting of the tail and loss of elevator control. I slowed my plane
    and regained control, but the 109 got away.

    On two other occasions ME 109s got away from me because the P 51d could
    not stay with them in a high-speed dive. At 525-550 mph the plane would
    start to porpoise uncontrollably and had to be slowed to regain control.
    The P 51 was redlined at 505 mph, meaning that this speed should not be
    exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it
    often was exceeded, if you wanted to keep up with those enemy planes.
    The P 51b, and c, could stay with those planes in a dive. The P 51d had
    a thicker wing and a bubble canopy which changed the airflow and brought
    on compressibility at lower speeds."
    - Robert C.Curtis, American P-51 pilot.

    I would take Curtis's story with a grain of salt as we don;t know if his P-51d had the dorsal fillet or the metal elevators.

    The Me 109 ailerons were certainly stiff, but this doesn't mean the aircraft couldn't be rolled. The light aileron forces on the P-51B+ is due to the use of 'internal balancing' of the ailerons. If the aileron was deflected up the pressure would increase at the aileron-wing hinge point. This high pressure air was chanelled to a bellows on the opposit side to reduce deflection forces. The P-51A lacked this innovation and thus had rather poor roll rate. The good mach characteristics of the P-51 wing section and the stiff two spar wing was also clearly a factor. The Spitfire's thin wing had low control forces but the aircraft didn't didn't have room for internal balancing. Due to the single spar design and low twist rigidity the Spitfire could achieve good deflection of the aileron but this wass then negated by the wing twisting in the opposite direction. The Me 109 didn't have a twist problem, it just had stiff ailerons at high speed. Note at mediium speeds it had a very good roll rate and low forces. A very small number of Me 109's made by WNF (Wiener Neustad Fabrik) near Vienna had spring tab servo ailerons where a small tab assists the pilot. They are somewhat of a mystery however. These were common in post 1944 USN fighters as well as the German jets.
     
  19. CobberKane

    CobberKane Banned

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    I read an article concerning the RAF testing of various Allied and Axis aircraft and the highest dive speeds they got were from (surprise) an ME-262 and a Griffon engined Spitfire. To match the 262 the spit had to use a much steeper dive angle. It lost it's prop and after an unpowered landing the wings were found to be canted back. I bet the pilot is still having nightmares over that one! Outright speed notwithstanding, the RAF also found that the P-47 handily out-dived the Spit IX
    I'd reiterate that dive performance is about more than just terminal velocity, it includes variables such as control and acceleration. If a P-47 out-accelertes a Bf 109 in the dive and outrolls it at, say, 470 mph, and has a better zoom climb to boot, then it's not going to matter much if the 109 pilot can actually ring a few extra knots out of his machine. The standard defensive manouver for a P-47 pilot with a 109 on his tail will be to put the nose down and firewall the throttle in the knowlege that his machinne will 'outdive' the German.
     
  20. Jenisch

    Jenisch Active Member

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    OFF, caught my attention:

    (4) The turning characteristics of the subject aircraft are substantially the same as the P-40F and the P-39D. None of these appears to have any definite superior turning characteristics.

    I know this is an Allison Mustang but there were substantial differents from the Merlin ones in terms of turning performance? Hans Lerch, in Luftwaffe Test Pilot, claims the Merlin Mustang B he flown was very good in turninfight as well. I already read in other sources the Mustang was a great dogfighter as well. However, it's strange, since it's laminar airfoil don't seems to give sufficient lift, and it's wing load was also higher then say, a 109. Someone can explain me this?
     
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