The sound barrier (1 Viewer)

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If those dive tests were done in 1942 then I presume the Mustang was either Mk I or II? I wonder if the P-51 B would have done any better considering the redesigned radiator inlet. I've no issue with the Spitfire hitting Mach 0.89. There's this:

sd2011.jpg
 
Hello Ponsford
you beat me by 20 minutes, I just dug out my copy of that report from the hard drive of my second pc (ret.). But the main thing is that the report is posted here.
The key word is TYPICAL, it wasn't just one odd dive but series of dives flown by the pilots of High Speed Flight Section, one of which was certain Lt Cdr Eric Brown.

Juha

Addition, Ponsford, P-51B might well have done better, if not for other reason at least it could have climbed higher, Allison Mustang dives were started at 28000ft because of its ceiling limitations.
 
As I was hurling quotes in earlier I'd also like to add this one, not really relevant to this argument, but it stood out for me as I was doing some further research into the Spitfires creation. Its from RJ Mitchell and it dates from 1934 during detail design;

"I don't give a toss whether the wings are elliptical or not, as long as they cover the guns!"

This retort was hurled at Beverley Shenstone, late of Heinkel, who first put forward the idea of the elliptical profile. Interesting or what? :)
 
I didn't miss the point - I said slab elevator. And then I asked you how 'trim' would solve the problem if the entire elevator was immersed in turbulent flow.

I don't believe the entire 'horizontal stabilizer' was immersed in turbulent flow Bill, the elevators might have been because of the shockwave produced at the LE of the stabilizer, but not the entire stabilizer. So like Muthke one could trim the a/c out of the dive by utilizing the fully movable horizontal stabilizer, which is what he did.

The British however don't seem to have known about the full use of the fully movable horizontal stabilizer trim and used only the trim tabs, which explains their findings.
 
But he didn't say 'I don't know'. He agreed with the RAE. And he DID design a supersonic jet that flew in the HA 300 so he would have been qualified to contradict his earlier position by the mid 1960's at the very latest. But, as far as I know at least, he didn't, for whatever reason.

Speaking purely subjectively I think the p1101 could have gone supersonic in a dive relatively safely but I am happy to accept the RAE/Messerschmitt view that the 262 could not.

But how does that verify one comment of his on the Me-262 ? Like I said he didn't design the a/c and he wasn't part of the research team, so his total technical knowledge on the Me-262 would've been limited as he didn't work with the a/c every day.


Anyway I don't think we're going to agree on this so lets just agree to disagree.

The IAS of Martindales dive was 0.92, this was subsequently revised downwards to 0.89 and is considered the accurate speed.

Now guess what the IAS of Muthke's dive was, and then note that the Me-262's speedometer was the most accurate around with built in compressibility correction.
 
Soren
Quote:"The British however don't seem to have known about the full use of the fully movable horizontal stabilizer trim and used only the trim tabs, which explains their findings."

have you source for that? RAF had a/c in service with movable horizontal stabilizer at that time.

"Now guess what the IAS of Muthke's dive was, and then note that the Me-262's speedometer was the most accurate around with built in compressibility correction."

Now those Spitfires were fully instrumented for those high speed dives, so we know what their instrument readings were, how about Muthke's 262?


Juha
 
have you source for that? RAF had a/c in service with movable horizontal stabilizer at that time.

So ?

Now those Spitfires were fully instrumented for those high speed dives, so we know what their instrument readings were, how about Muthke's 262?

His speedometer hit its max = 1,100 km/h Juha.
 
Don't forget also the Miles 'Gillette Falcon', the first aircraft in the world to use an all-flying tail specifically intended for control at high speeds. It flew in 1944 and was built specifically in response to the need to be able to control the Miles M.52 at supersonic speeds. It is recognised that without this device Yaegers attack on the sound barrier in the X-1 could not have been successful so yes, the British were quite well up on this asp0ect of controllability at the time.
 
Soren
I asked independent proof, like flight test recorder. Not what someone claimed 20 years after the test.

Juha
 
Yes, it was 13% at the root tapering to only 9% further out. I think this is what made the difference, from what I have read other fighters wings did not do this, though I stand to be corrected if this is not the case.

As I mentioned earlier, during the 1946 tests Supermarine were quite perturbed to learn that their brand new, laminar flow winged, Spiteful was actually slower in the dive than the Spitfire was, especially as this same wing was being grafted onto their new jet fighter, the type 392, which had started its development as a jet-Spitfire! The production Attacker emerged with a max level speed of 590 mph in 1947, about 50 more than the 262, but it still could not outdive the Spitfire.
 
Tapering the wing thickness/chord was a rather common feature, the P-36/P40, for example, had a root section of NACA 2215 (15%) and 2209 (9%) at the tip. It seems tohave been rather uncommon for a wing to feature constant thickness. (though iirc the Whirlwind featured a constant NACA 23015 from root to tip, and the P-63 featured a constant 16% laminar flow airfoil)

The Me 262's airfoil was 11% at the root and 9% at the tip. (~8.6% taking sweep into acount)

However it would be the root (as it's the tickest) that would reach critical Mach first.
If the Spitfire's tailplane was thin enough and the tail didn't become immersed in turbulent flow from the wing above critical Mach, the elevator would still function up to until the tailplane its self reached critical mach.


As to the a/c being able to recover from a terminal dive, as can be seen in Ponsford's chart, the spitfire was only above ~.82 Mach from ~33,000 ft to ~22,000 ft. (for a total of ~22 seconds, and above .84 Mach for ~18 seconds) And the recovery was made well below these altitudes.
 
The British however don't seem to have known about the full use of the fully movable horizontal stabilizer trim and used only the trim tabs, which explains their findings.

Soren did the Me 262 feature functioning elevator trim tabs?

According to US reports, the a/c tested a Wright field apeared to be intended to used adjustable trim tabs for both the elevator and ailerons, but the ailerons were only fitted with ground-adjustable tabs, and the elevator tabs had been riveted in place. (trim being effected by the adjustable tailplane) The rudder being the only surface fitted with an in-flight adustable trim tab.

The US manual on the Me 262 also warned against using stabilizer trim changes when entering or recovering from dives as it could lead to overcontrol and possible overstressing of the airframe. (the manual did make many refrences to the stabilizer trim, so, at least for tests at Wright field, they were well aware of its use)
 
Hello Ponsford
you beat me by 20 minutes, I just dug out my copy of that report from the hard drive of my second pc (ret.). But the main thing is that the report is posted here.
The key word is TYPICAL, it wasn't just one odd dive but series of dives flown by the pilots of High Speed Flight Section, one of which was certain Lt Cdr Eric Brown.

Juha

Addition, Ponsford, P-51B might well have done better, if not for other reason at least it could have climbed higher, Allison Mustang dives were started at 28000ft because of its ceiling limitations.

Sorry about that Juha. It wasn't intentional, honest ;) Good point about the altitude of the Mustang. That hadn't occurred to me. I just remembered this report on the P-51 D dive:

Compressibility Dive Tests Part I on North American P-51D Airplane (Mustang IV), AAF No. 44-14134


"The airplane was flown to a maximum true Mach Number of 0.85 during the twenty-sixth dive on 9 September 1944 and to a maximum calibrated airspeed of 486 MPH during the twenty-eighth dive on 9 September 1944."

"In extreme war emergency the airplane can be dived to a Mach Number of 0.83 (400 MPH Indicated Airspeed at 25,000 feet) if a very gradual pull-out is made."

p-51-dive27.jpg
 
I have seen several references from NAA, USAAF and RAF that detailed terminal dives - all peaking at .85, and very descriptive of the 51D/Mustang IV at 'the edge' - particularly the strengthened ammo cover door bulge..and severe buffeting

It is also clear that the Spitfire dive tests under similar test conditions and calibrations achieved a higher Mach than the 51.

Instrumentation being what is was in 1944-1946 leads one to obtain a full report to determine the methods of calculation - most of which were instrumentation corrections using analytical methods for compressibility.

I have yet to find a definitive dive report on the 262 (i.e. not anecdotal) which describes the dive, the tuck and the methods used to a.) warn of the phoenomena and b.) the approved Me method of recovery. Perhaps Soren has one.
 
Acknowledge ? Bill I've never claimed there weren't any, I just pointed out that the entire horizontal stabilizer was used for trim, esp. in cases where the trim tabs weren't enough. (The Bf-109 had the same feature, which is what allowed it to recover from high speed dives quicker than other fighters)

The only way to get out of the negative G dive the Me-262 would start after 1,100 km/h was to utilize the movable horizontal stabilizer, the elevators and therefore also trim tabs being rendered useless because of turbulent flow.
 
http://www.zenoswarbirdvideos.com/Images/Me262/262PilotHandbook.pdf

Soren, that site had the very manual I was referring to. (with the comment of no functioning trim tabs) Accordingly, all trim changes for pitch are made by adjusting the horizontal stabilizer.

Elevator trim tabs would seem redundant given the stabilizer trim, did the Bf 109 feature elevator tabs as well?

I didn't see any mention of elevator tab controls in the cocpit instument pannel diagrams, but I haven't read the other articles there yet.
 

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