Did the Me 262 break the sound barrier?

[Topspeed]

Gabriel,

You amaze me. You know all about aviation.

The finnish test pilot who brought a the first Fiat G.50s into Finland have been said to have reached the sound barrier.

In fact ltn. Harmajas plane hit the compessibility problem, plane was scrapped after a dive that reached 850 km/h in 1939.

JT

[Hop]

No ww2 fighter was capable of breaking the sound barrier. None had a wing with a high enough critical mach.

Both NACA in the US and the RAE in the UK carried out a lot of research into high speed flight, including very high altitude, very high speed dive tests. Several of the test pilots died.

The highest speed they managed to reach was mach 0.89 in a Spitfire.

There is a huge drag rise when you exceed the critical mach of the wing. The critical mach depends on 3 main factors, sweep, thickness, and aspect ratio. The lower the aspect ratio the higher the critical mach. However, the most important factor is wing thickness. You simply have to have thin wings.

The Spitfire had the thinnest wings of any of the prop fighters, 13% root, 9.4% tip. The P-51 was 16% root, 11% tip. The 262 was 11% root, 9.1% tip.

The F-86 Sabre, the first jet to go supersonic, was 9.5% root, 8.5% tip, and had heavy sweep, and a lower aspect ratio (the 262 aspect ratio was quite high)



This is from the RAE and shows the drag figures for some of their high speed dives. You can see how the drag increases dramatically as the critical mach is exceeded. There is no way round this other than to raise the critical mach by having wings, lower aspect ratio and sweeping the wings.

[Topspeed]

Hop,

Thanks for the nice chart. Are you an aerodynamist ?

JT / Oulu / Finland

[gabriel pagliarani]

No ww2 fighter was capable of breaking the sound barrier. None had a wing with a high enough critical mach.

Both NACA in the US and the RAE in the UK carried out a lot of research into high speed flight, including very high altitude, very high speed dive tests. Several of the test pilots died.

The highest speed they managed to reach was mach 0.89 in a Spitfire.

There is a huge drag rise when you exceed the critical mach of the wing. The critical mach depends on 3 main factors, sweep, thickness, and aspect ratio. The lower the aspect ratio the higher the critical mach. However, the most important factor is wing thickness. You simply have to have thin wings.

The Spitfire had the thinnest wings of any of the prop fighters, 13% root, 9.4% tip. The P-51 was 16% root, 11% tip. The 262 was 11% root, 9.1% tip.

This is from the RAE and shows the drag figures for some of their high speed dives. You can see how the drag increases dramatically as the critical mach is exceeded. There is no way round this other than to raise the critical mach by having wings, lower aspect ratio and sweeping the wings.

CDo in your RAE graph is not Cx. The drag-force opponent to front motion is Cx component.This is not the right graph to show us. :roll: Everything could trespass Mach 1 if throwed with enough power! The problem is in homing back still living...Not only: if your plane is close to Mach1 are you sure that all parts of your plane are still sub-sonic? No? Propeller is the fist to become super-sonic....never say never. Try to explain the inversion of commands without exceeding Mach1! Chuck Yeager experienced it and his X-1 surely was supersonic! Italian pilots that experienced "inversion" dogfighting over Naples during 1943 never said to be "supersonic"...they tasted the "inversion" and their own Reggiane 2005 were totally bent after it. This evidence let engineers to think they trespassed Mach1...the few still living.

[gewehrdork]

You mean to say the italian pilots dived so hard to high tail it form the fight they exceeded mach 1 ?. Sorry but could not resist the question ( he he he ).

[Topspeed]

Gabriel,

Whatza think of my pusher design..could that go beyond mach 1 ?

JT

[gabriel pagliarani]

You mean to say the italian pilots dived so hard to high tail it form the fight they exceeded mach 1 ?. Sorry but could not resist the question ( he he he ).

They were not doing a speed test in the desert of Arizona. Ten. Mazzoleni of 362a Squadriglia lift off on alert wit the rest of the formation from ciampino airport at 06:00 of 24 july 1943. Some days before a close mix formation of B17/B-24 just destroyed Borgo S.Lorenzo, a populated quarter of Rome causing more than 1500 casualties in a while. Ten Mazzoleni fired against intruders over Naples, less than an hour later. He attacked frontally a B24 and he was climbing for a 2nd attack when P-38 escorting the formation obliged him to a sudden dive from 24000 ft to sea level. No escort followed him in such a dive, but when he returned home his Re 2005 was completely out of order with the rudder and the tail bent. He experienced the "inversion of command" and the errngineering staff established he had a supersonic dive.
Pls visit:
http://www.aldini.it/re2005/
"In May of 1943, the first Sagittarios entered service with the Regia Aeronautica. The first prototype and several of the zero series aircraft were used operationally by the 362a Squadriglia, 22o Gruppo at Naples-Capodichino starting in May 1943, being used to defend Rome and Naples. The squadron had developed a rather daring method of attacking Allied B-17s which involved diving head-on with all guns blazing, then flipping the aircraft over on its back and diving away at the last minute.The Reggiane had good behaviour in close dogfight and , according to General Minguzzi, who flew both Re 2005 and Spitfire, was even better than the Spit in tight turns and handling.The operative life of the Sagittario was concluded by the Armistice , that came in the September 1943. "
Mazzoleni's B-24 crashed near Albano Laziale. Only 2 of 10 crew bailed out. Cpt. Mazzoleni died in Umbria in Summer 1998. I knew him.

The fact that Colombo went in America as first, doesn't mean he was really the first man really gone in America as first Roger?Open your mind Gewehrdork. At least 2000 pilots (Axis or Alleys) tasted compressibility during WW2 and someone more than a time. Only very very few survived to those lethal meetings with the "sound barrier".

[gabriel pagliarani]

Gabriel,

Whatza think of my pusher design..could that go beyond mach 1 ?

JT

The problem is in the propeller: front or rear mounted no actual made propeller could move your fighter faster than Mach 1.. 8) ...horizontally!

[Topspeed]

Why not Gabriel ?

If the prop revols at mach.2 why couldn't the plane go mach 1.1 for instance. This mean a lot of research and whole lotta extra power.

The current prop speed record is done at roughly 1.1 hp/kilos power to weight ratio..wouldn't cleaner aerodynamics with 1.5 hp/kilos get one somewhere..at least to the new record ?

[gabriel pagliarani]

Why not Gabriel ?

Simply because the blades of the propeller are little wings and they work by depression the most curved surface exerts on the less one. Over Mach 1 the blade causes a shock wave without any "sucking effect" (best known as "portance") exerted by the most curved surface. This is often called "high speed stall condition". Theorically is possible to build a blade banana-shaped working by shock-waves and NASA is working around this project without any allowable success. Note that the same problem affects the first stage fan rotor of any jet-engine... finally it is only a tubed propeller! The job of engineers is in slowing the speed of the air incoming from the open inlet. How? Easy..by Ventury law of statical+ dynamical pressure. (pressure exerted on the prop-fan is the sum of the pressure due to air speed + statical pressure exerted on the inner surface of the tube) Consequently supersonic jets have an inlet duct that is basically a variable-geometry reversed Venturi-tube (small inner area of the tube near the inlet, wide area close to the prop-fan). Higher the speed of the plane, lower the statical counter pressure exerted by the walls of the tube. In such way the air incoming has enormous dinamical + statical pressure but low speed because the dinamical component has been lowered and the fan prop could work in the best way, without stalling. For this reason I said that a supersonic plane could not be supersonic in any point of its own surface.... :roll: There are many kinds of reversed Venturi ducts (bi-dimensional inlets or tri-dimensional, Mach cones, semi-cones) but the principle of the reversed Venturi tube is always applied on jet-engine inlets. In other words, rev. Venturi' s pipe is the smart trick by mean of which a prop could be supersonic

[Topspeed]

Gabriel..there is still a lot space between 850 km/h and a sound barrier isn't there ?

Could a pusher plane be more economical than a jet...jet needs those inlets and tubes => THAT BRINGS MORE VETTED AREA and induced drag.

Pusher does not have the induced drag..radiators are also flee flowing with ramair effect...heatened air sorta pushes the plane too.

Juke

[Hop]

CDo in your RAE graph is not Cx. The drag-force opponent to front motion is Cx component.This is not the right graph to show us.

It is the right graph to show because it shows the rise in drag coefficient at high fractional mach numbers.

Everything could trespass Mach 1 if throwed with enough power!

Not intact it couldn't.

The Spitfire in this example had nearly 5,000 lbs of total drag at these mach speeds. With the steep rise in drag coefficient, you'd be looking at well over 10,000 lbs of drag before you hit mach 1, and with the buffeting as well, any WW2 fighter would disintergrate with forces like that acting on it.

Not only: if your plane is close to Mach1 are you sure that all parts of your plane are still sub-sonic?

They certainly aren't all still subsonic. Air speeds up to travel over the surface of a wing. The thicker the wing, the more it has to speed up. Once the plane is up over mach 0.8 or more, parts of the airflow will definately be supersonic, and not just over the prop.

Try to explain the inversion of commands without exceeding Mach1!

Control reversal can occur at high fractional mach numbers because some of the airflow is already supersonic. It's that that cause effects like mach tuck, and affects different planes at different speeds. The thinner the wing, generally the faster you can go without encountering such effects.

The British, Germans and Americans all carried out extensive testing into high speed flight. None came close to mach 1 in proper tests. The Germans, who didn't put as much effort in, didn't go much beyond mach 0.8. The US pushed Mustangs and Thunderbolts to 0.86, the British, who also used Mustangs and Thunderbolts, found the Spitfire the best, and went as high as 0.89.

That was already beyond the safe limits, and many test pilots died, but none of these tests, which were seeking information on the sound barrier, ever went faster than that.


Pilots in the field sometimes reported speeds over mach 1 because the air speed indicators fitted to aircraft could not cope with very high speeds and very high rates of descent. That's why in the proper tests of high speed flight, they didn't rely on the instruments normally fitted, but went to great efforts to fit a range of speed, altitude and temperature monitoring equipment.

Chuck Yeager experienced it and his X-1 surely was supersonic!

A great many pilots experienced it without getting anywhere near mach 1. Normal dynamic forces could cause control reversal, as well as the effects of approaching mach 1.

Italian pilots that experienced "inversion" dogfighting over Naples during 1943 never said to be "supersonic"...they tasted the "inversion" and their own Reggiane 2005 were totally bent after it. This evidence let engineers to think they trespassed Mach1...the few still living.

No, this happened on many occasions to many pilots. Aileron reversal was the most common, and could frequently happen in a normal high speed turn. Elevator reversal was not unkown, and could occur when approaching mach 0.8 and above.

The effects of the sound barrier do not begin at mach 1, they begin a long time before that. The graph I posted is a good illustration. It shows the effect of transonic drag building up between 0.7 and 0.8 mach.

The seperate table for the Thunderbolt dive shows the effect on the elevator. Despite pulling increasing up elevator, the Thunderbolt was actually increasing it's angle of dive due to mach tuck. The pilot would have been unable to recover if the plane hadn't been fitted with dive recovery flaps. The elevator trim angle reached 7 deg, and the pilot was pulling another 4 deg (which was the maximum force he could exert) and the plane was still steepening it's dive.

This evidence let engineers to think they trespassed Mach1...the few still living

Because of the translation difficulties, I'm not sure what you mean by trespassed mach 1. It's certainly possible they entered the transonic region, but that doesn't mean reaching mach 1. Did they reach the region where mach tuck, control reversal and massive buffeting occured? Certainly. Did they reach mach 1? No way. None of the high speed research flights, hundreds of which were carried out in the UK and US, reached anywhere near mach 1, despite often using planes that were specially modified for high speed.

At least 2000 pilots (Axis or Alleys) tasted compressibility during WW2 and someone more than a time. Only very very few survived to those lethal meetings with the "sound barrier".

Compressibility occurs well before the sound barrier in a WW2 fighter. You can see the phenomenon of compressibility in the first chart I posted yesterday, that's what's causing the steep rise in drag factor.

(The charts all come from a report from the RAE Royal Aircraft Establishment from dive tests conducted in 1944, courtesy of Neil Sterling who found them in the British archives)

[Topspeed]

Hap,

If they were able to reach .89 with Spitfire XI then I would almost certainly say it was possible to dive to mach 1.001 with a Swalbe. How they were able to recover from it..I dunno.

Spitfire was designed already in the thirdies and even a Fiat G.50 did reach the speed of 850 km/h the engineers were somehow able to calculate it already back then.

BTW: Tempest was able to dive at 540 mph roughly mach 0.75 ( 870 km/h ) safely according to manual and thence close in on a Me 262 for instance.

JT

PS: Didn't they loose a prop at such an attempt in a dive with a Spitfire ?

[gabriel pagliarani]

Gabriel,

You amaze me. You know all about aviation.

The finnish test pilot who brought a the first Fiat G.50s into Finland have been said to have reached the sound barrier.

In fact ltn. Harmajas plane hit the compessibility problem, plane was scrapped after a dive that reached 850 km/h in 1939.

JT

:roll: ..I would like to know really a lotta other more useful things! I was wondering about temperature: effectively at low temps air density increases linearly (P+V=nRT ) Did Harmajas touch the barrier during Finnish cold winter? Speed of sound could be lowered a lot by such freeze.

To Hop: too many words in your post pls watch carefully the pitch angle of the elevators in your Thud chart. When exceeding 500 m.p.h (or knots?) your own data sheet has well shown a banking from about 3° positive to 3° negative. THIS IS THE INVERSION OF COMMANDS! Exactly what I said before... 8) And no WW2 fighter was equipped with any machmeter before jets. Read carefully the meaning of C.I.A.S. at the bottom of the same. Consequently what have you to ask more to a pilot when the wings of his plane are stripped away and the foe is gunning his own precious and unique ass? Gulf of Naples in summer '43 was not surely the comfortable US Salt Lake high speed location during '50s. :roll:

[Topspeed]

No Harmaja flew it in Italy.

BTW: He was killed in the early days of a Winter War flying a Fokker XXI. Had he had a Fiat..things may have been better for him. We also lost a whole squadron of Gloster Gladiators when the attacking I-16s strafed while the Gladis were taking off.