Author Topic: About the Spitfire IX at very high speeds (Read 1018 times)

gatt · « **on:** November 21, 2001, 06:29:00 AM »

I'd like to hear something from Spitfire IX pilots. Dont you think that our IX is a bit too maneuverable at very high speeds?
I've been flying it for some sorties and I have to say that you can use real Hit&Run tactics at *very* high speeds without suffering (too much) from bad roll rate or black outs.
I remember very well the WB's Spitfire IX and it was quite different. Outstanding fighter ... but you couldnt use it at very high speeds. Flying AH's MkIX I fear much less the compression than flying the 109 or many other fighters.
Not a whine or a flame, just curious <S>!

Jochen · « **Reply #1 on:** November 21, 2001, 06:54:00 AM »

I think there has been some talk about bit generous high speed roll rate of Spit V/IX earlier but I am not sure if they were just guesses or were they backed up by evidence.

Nifty · « **Reply #2 on:** November 21, 2001, 09:43:00 AM »

I have no idea about the real life data on Spits roll rates. At higher speeds in AH, she does get sluggish in the roll and lift. It's hard to compress a Spit. I've never had one vibrate on me like a 109 does. Also, the Spit starts straining and whining at you before she loses all manueverability, so I start leveling out before something rips off.

Maybe the point at which she fully compresses is just past her structural threshold? She starts creaking about 450mph, IIRC.

Karnak · « **Reply #3 on:** November 21, 2001, 11:07:00 AM »

She'll actually reach compression before shedding anything, she'll just complain for a lot of it. Mossie does the same.

It has been too long since I dove a Spit to high speed, but IIRC the roll rate might be a bit generous. The Spitfire's elevators, on the other hand, shouldn't suffer from high speed as they have always been described as light handling at all speeds.

funkedup · « **Reply #4 on:** November 21, 2001, 01:07:00 PM »

Going off pilot anectdotes, pilot's notes, etc: Spitfire had a very high maximum safe diving speed. Elevator control was not a problem. But ailerons got very stiff.

Seeker · « **Reply #5 on:** November 21, 2001, 01:12:00 PM »

The Spit IX is the fastest diving piston engined fighter of WWII.

Not the fastest in level flight, not the fastest acceleration, but point the nose down from a great height and you'll get to 0.97 mach. You'll also blow the prop off, just like they did at Boscombe down.

Zigrat · « **Reply #6 on:** November 21, 2001, 02:49:00 PM »

theres no way that thick airfoil could get to true m.97

Karnak · « **Reply #7 on:** November 21, 2001, 03:02:00 PM »

As I understood it, it was a Spitfire PR.MkXIX that set the record, post war, at .92 mach (and it didn't shed anything, back in service less than a week later). The pilot saw the air take on the milky look of transconic flow over the wings.

It should be noted that this was an unintential test and the Spitfire was out of control. The dive started from over 50,000ft and ended at about 2,000ft.

Zigrat,

What thick airfoil? We're talking about Spits. They have quite thin airfoils, actually. Turned out that the Spit's wing was better than the lamilar flow wings of the Spitful.

-ammo- · « **Reply #8 on:** November 21, 2001, 05:35:00 PM »

Quote

Originally posted by Seeker:
The Spit IX is the fastest diving piston engined fighter of WWII.

Not the fastest in level flight, not the fastest acceleration, but point the nose down from a great height and you'll get to 0.97 mach. You'll also blow the prop off, just like they did at Boscombe down.

Even moreso than a P-47? I have never seen a reference for that but would like to learn more. Could you provide?

V/R

Kratzer · « **Reply #9 on:** November 21, 2001, 05:40:00 PM »

I've also been under the impression that the P47 was the best diver... of course, maybe that is just in terms of accelleration... I'd like to see data on that as well.

Karnak · « **Reply #10 on:** November 21, 2001, 05:45:00 PM »

The P-47 will accelerate much, much faster than the Spitfire, and so for all practical purposes in combat the P-47 dives better. So does the P-51D, and I'd guess, the F4U, F6F, Fw190 and maybe the Bf109.

What the Spitfire has is the asoteric claim to the fastest speed in a dive when diving from high altitude. This capability actually gave clues to what was desirable in wings when going for the sound barrier.

GRUNHERZ · « **Reply #11 on:** November 21, 2001, 06:57:00 PM »

The 109G6 actually outdives a Spit14 until speeds get very high then spit catches.

Vermillion · « **Reply #12 on:** November 21, 2001, 11:42:00 PM »

But you do have to admitt that the Spit in AH, does Not seem to suffer much roll stiffness due to high speed.

Karnak · « **Reply #13 on:** November 22, 2001, 12:53:00 AM »

It doesn't seem to suffer as much as is described from tests on the real thing.

I would agree with you on that.

Badboy · « **Reply #14 on:** November 22, 2001, 07:44:00 AM »

For the Spitfire Mk IX, the pilot’s notes quote a limiting Mach number of 0.85 and to put that into perspective, even some of the jet aircraft produced after the war had lower critical Mach numbers. However, the values quoted in pilots notes are often conservative for safety reasons and the Spitfire was indeed capable of more.

During 1942 trials were conducted at RAE Farnborough to measure the drag and trim changes at high Mach numbers on the P-47, P-51 and Spitfire. The results of the drag measurements between the Mustang and Spitfire are interesting and show that the Spitfire had lower drag from Mach 0.65 upwards. The Mustang had lower drag at all speeds below that, and the P-51's drag bucket and excellent long-range capability occurs at relatively low speed. I have curves taken from that report and the data represents values actually achieved in flight, it shows the Spitfire achieving speeds of Mach 0.9 when flown by Sqn Ldr Tobin, and the Mustang only barely beyond Mach 0.8. That agrees with the often quoted limiting Mach of 0.77 for the P-51. The Spitfire also achieved a speed of Mach 0.9 in the hands of Sqn Ldr Martindale which I have seen quoted as Mach 0.89 in some sources, possibly due to confusion caused by calibration issues with the specially fitted Mach meters. The question, of whether the Spitfire reached Mach 0.89 or Mach 0.9 is not important, the point is, that it was faster than any other aircraft of that time!

The reason for the Spitfire’s outstandingly better high Mach number behaviour is due to the fact that it had a thickness to chord ratio of 13 percent, compared to the 16 percent of the Mustang, which also had a more draggy cooling system and a thicker tailplane. Also, the Spitfire was structurally sound at those speeds and there were only rare incidents involving minor failures. Most notably, the loss of a prop' in one test flown by Sqn Ldr Martindale that did not result in the loss of his aircraft because he managed to land it safely.

I believe that the Spitfire's strengths at high speed in Aces High is accurate. However, this does of course only relate to maximum speed in a dive, as already pointed out.

Badboy

[ 11-22-2001: Message edited by: Badboy ]