sound barrier?

[Angus]

Widewing: do you think that he mached the control surfaces?
That's not mach one for the aircraft, but for a limited amount of airflow it is.

[Widewing]

Originally posted by Angus
Widewing: do you think that he mached the control surfaces?
That's not mach one for the aircraft, but for a limited amount of airflow it is.

Indeed, localized airflow can go transonic, but the aircraft itself is still far away from Mach one. While Mach 0.94 may seem close to Mach one, in terms of drag rise, it's still far, far away.

While the 262's thickness ratio was relatively low for the time (11%), it was still a conventional airfoil and subject to greater drag rise than the laminar airfoil of the F-80. Sweep was minimal, and solely designed-in for balancing lift, not forestalling the onset of peak drag (see this), but certainly helped, nonetheless.

Averaged over the entire span, the P-39's thickness ratio was around 12% (15% at root, 8% at wingtip). Compared to the P-51D (16.5 % wing root, 11.5% wingtip), you might think that the P-39 would have the higher critical mach. It doesn't. At Mach 0.75, the P-39 is experiencing a tremendous rise in drag coefficient, but the P-51 is only showing a moderate increase (.055 Vs .025, up from .0217 and .0176 respectively).

For reference, zero lift drag coefficients (from NASA):
F-80 - .0134
P-51D clean, without pylons - .0163
Me 262 - .0169 (NASA) or .0161 (Boyne)

Here's another interesting read relative to the topic: Aerodynamic Problems and Refinements

My regards,

Widewing

[Angus]

Widewing, can I email you?
If so, drop me a note on info@gardsauki.is.
I am digging into these matters, and you could help me as well as I could provide you with some interesting information.

[Charge]

" My understanding is that the Me 262 had a critical Mach of 0.87, and suffered structural failure not far above this."

Where did you get that figure, Widewing?

Stormbirds estimate it to be 0.82.

Help Wiki says:

Messerschmitt also conducted a series of carefully controlled flight tests with the series production Me 262. In these dive tests, it was established that the Me 262 was out of control in a dive at Mach 0.86, and that higher Mach numbers would lead to a nose-down trim that could not be countered by the pilot. The resulting steepening of the dive would lead to even higher speeds and disintegration of the airframe due to excessive negative g loads.

Bla bla... Messerschmitt undertook no attempts to exceed the Mach 0.86 limit for the Me 262.

After the war, the Royal Aircraft Establishment — at that time one of the leading institutions in high-speed research — re-tested the Me 262 to help with the British attempts at breaking the sound barrier. The RAE achieved speeds of up to Mach 0.84 and confirmed the results from the Messerschmitt dive tests as accurate. No attempts were made to exceed the Mach limit established by Messerschmitt.

http://help.com/wiki/Messerschmitt_Me_262

For some reason I don't think that wing sweep angle to be the only determining  factor for mach performance for 262...

"Averaged over the entire span, the P-39's thickness ratio was around 12% (15% at root, 8% at wingtip). Compared to the P-51D (16.5 % wing root, 11.5% wingtip), you might think that the P-39 would have the higher critical mach. It doesn't. At Mach 0.75, the P-39 is experiencing a tremendous rise in drag coefficient, but the P-51 is only showing a moderate increase (.055 Vs .025, up from .0217 and .0176 respectively)."

...but airfoil shape and wing sweep combined. Don't know the NACA profile for 262 but AFAIK it was not a laminar flow profile.

-C+

[Debonair]

just judging from pics of 262s, it looks awful with respect to the supersonic area rule.  
much worsed than the mentioned straight wing supersonic planes

[Angus]

The late version Meteors went quite fast, and for a while held the world speed (or was it racing) record. Wonder how the wing design racks up against the 262 when it comes to the transonic area...??

[Widewing]

Originally posted by Angus
The late version Meteors went quite fast, and for a while held the world speed (or was it racing) record. Wonder how the wing design racks up against the 262 when it comes to the transonic area...??

From NASA's history of aviation:

"Although bearing a number of configuration similarities to the Messerschmitt Me 262, the Gloster Meteor differed in a number of significant respects from the German fighter. The Rolls-Royce Derwent [284] centrifugal- flow turbojet engines of 3500 pounds thrust each were mounted in the chord plane of the wing rather than below it. The front spar actually passed through the inlet, and the rear spar was split and formed hoops around the top and bottom of the engine. The data in table V show that the wing was of low aspect ratio and had no sweepback. Airfoil-section thickness ratio varied from 12 percent at the root to 10.4 percent at the tip. Simple split flaps for lift augmentation were located on the wing lower surface between the fuselage sides and engine nacelles. These relatively small, ineffective, high-lift devices dictated the relatively low wing loading of 43 pounds per square foot, a value about 63 percent lower than that of the Me 262. As compared with the German fighter, the Meteor was characterized by both higher wing area and drag area. Highly desirable dive brakes were provided on the upper and lower surfaces of the wing between the nacelles and the sides of the fuselage. To clear the jet exhaust, the horizontal tail was mounted high on the vertical tail. Longitudinal trim changes could be made with an elevator tab. An innovation at that time was the pressurized cockpit, which maintained the cabin pressure at a value corresponding to 20 000 feet when the actual altitude was 40 000 feet.
 
Performance characteristics shown in table I give a maximum speed for the Gloster Meteor F. Mk. 4 of 570 miles per hour, or a Mach number of 0.81, at 20000 feet. One source (ref. 162) indicates that at high speeds the Meteor experienced large trim changes, high aileron stick forces, and a tendency toward snaking. Snaking may be described as a self-sustained yawing oscillation; it plagued many of the earlier jet fighters. According to reference 188, numerous modifications were tried in an effort to cure the problem on the Meteor - none of them were entirely successful. (Later research indicated that the problem was probably related to incipient flow separation from the relatively thick airfoil sections used in the tail.) Climb performance of the aircraft was outstanding. The sea-level rate of climb was 7500 feet per minute, and an altitude of 30 000 feet could be reached in 5 minutes. Clearly, the performance of the Meteor F. Mk. 4 was much superior to the performance of the Messerschmitt Me 262A for which data are given in table V. To put this comparison in proper perspective, however, the Meteor F. Mk. 4 did not fly until after the end of World War II and had a thrust-to-weight ratio of 0.47 as compared with 0.28 for the earlier German aircraft. The author's analysis of the physical and performance characteristics of the two aircraft suggests that the superior performance of the Meteor was due to the higher thrust of its engines and not to any inherent superiority in aerodynamic design."

My regards,

Widewing

[Angus]

WOW, that was quick.
0.81 level or max in dive?

[Widewing]

Originally posted by Angus
WOW, that was quick.
0.81 level or max in dive?

Level...

My regards,

Widewing

[Angus]

TY Widewing.
I have Neville Duke's "Test Pilot", which has a lot of material about breaking the barrier. He flew the Meteor as well, quite a bit.
I lent the book but will have it in my hands later today, so I'll see if there is anything there I can come up with.

[cav58d]

Originally posted by Meatwad
You didnt ask anything about breaking the sound barrier. You should learn how to post your questions better


Anyway if you can read what you posted in the first post, you will see your answer

I know exactly what he was talking about

[Debonair]

Supersonic flame war!