Fw 190A vs P-47D diving from 25,000 ft to deck.

[Viking]

Originally posted by Knegel
I also doubt that the FW190 had a higher critical mach!!

According to Eric Brown they actually did. See the videos I posted.

[Shuckins]

The P-47's critical mach number was .82 at altitudes above 25,000 feet....and corresponded to 601 mph TAS.

I doubt seriously that the Fw-190A had the horsepower or the weight to match the Jug in a dive from extremely high altitudes where the Jug's turbo-supercharger gave it a tremendous advantage.

Which Fw-190 was Capt. Brown talking about?  If he was talking about the D9 that might be a different matter....at least at medium altitudes.

Regards, Shuckins


P.S. Corky Meyer related a tale in a Flight Journal article about a radio-controlled Hellcat reaching .81 mach in a dive from high altitude.  He believes the people controlling the Hellcat didn't understand the effects that such a high near mach speed had on piston-engined aircraft....the controls set in concrete, the tucking under of the nose.....and as a consequence flew it into the ground in the near-vertical dive.

[Viking]

He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.

In Aces High the effects of compressibility is not modeled realistically; it is “easy mode” compared to real life. It would perhaps be difficult to model it accurately as the effects were individual to each plane. The P-38 for instance would nose over into an inverted almost vertical dive that was unrecoverable without dive flaps (that were later added to the design). Unfortunately for the P-38 pilots in Europe, their P-38s were never equipped with dive flaps and many plunged to their deaths trying to follow diving Germans.

[Viking]

Early model P-47 would often break up in compressibility dives, and late model P-47 were given dive flaps (like on the P-38) to help pilots recover. Prior to the addition of dive flaps the P-47 pilots were trained in how to recover from compressibility dives, but it was a harrowing experience that would leave them bruised and battered at 2000 feet over enemy territory, often with structural damage to the control surfaces.

[Widewing]

Originally posted by Viking
He said that when Doolittle found that his fighters didn't engage the enemy, but simply dived past them into oblivion never to be heard from again, he contacted the British at RAE Farnborough to find out what was going on. The British being the leading authority on high speed testing at that time. RAE found that the 109 and 190 had a tactical Mach limit of 0.75, the P-38 had a tactical limit of 0.68 or 0.69 (I don’t recall which) and the P-47 had 0.71. Brown said they were useless as high altitude escorts and that only the P-51 with a tactical Mach limit of 0.78 could deal with the Germans at 30k.

In Aces High the effects of compressibility is not modeled realistically; it is “easy mode” compared to real life. It would perhaps be difficult to model it accurately as the effects were individual to each plane. The P-38 for instance would nose over into an inverted almost vertical dive that was unrecoverable without dive flaps (that were later added to the design). Unfortunately for the P-38 pilots in Europe, their P-38s were never equipped with dive flaps and many plunged to their deaths trying to follow diving Germans.

Brown is off a bit about the critical Mach of the P-47. Republic states that it is Mach .74 rather than .71. Placarded maximum permitted dive speeds at 10k are as follows:

P-47D: 500 mph IAS
P-51D: 500 mph IAS
P-38L: 440 mph IAS
F4U-1D 443 mph IAS
F6F-5: 449 mph IAS

Inasmuch as the Fw 190 uses the same wing section as the F4U (NACA 23015), I doubt that the 190 had a critical Mach greater than the P-47.

My regards,

Widewing

[Viking]

Originally posted by Widewing
Brown is off a bit about the critical Mach of the P-47.

Brown was talking about tactical Mach number not critical (or limiting Mach number as he called it). Tactical Mach is the maximum speed you can still fight the aircraft. Critical/limiting Mach is the speed where you lose all control of the aircraft.

[Viking]

Originally posted by Widewing
Inasmuch as the Fw 190 uses the same wing section as the F4U (NACA 23015), I doubt that the 190 had a critical Mach greater than the P-47.

Why would that be relevant? The Spitfire had the highest limiting Mach number of all piston engine fighters and still holds the record for highest Mach attained by a piston engined aircraft: Mach 0.891.  Now, the Spitfire had an elliptical wing, but its wing section was nothing special.

The Me 109 was dived to Mach 0.79 in instrumented tests. Slightly modified, it was even dived to Mach 0.80, and the problems experimented there weren't due to compressibility, but due to aileron overbalancing. P-51 and Fw 190 achieved about Mach 0.80. The P-47 had the lowest permissible Mach number of these aircraft. Eric Brown observed it became uncontrollable at Mach 0.73, and "analysis showed that a dive to Mach 0.74 would almost certainly be a 'graveyard dive'".

[LEADPIG]

I'm confused...... .  Another thing why'd the P-38 have such a low mach number, i always assumed it was because of that long beautiful wing and those two propellors. I once heard that the most drag inducing part of a prop plane was the prop and that eliminating it would usually cause an increase of about 100mph. I think the Jug would win if someone sees me in TA one day ask me and i'll try it.

[Viking]

The P-38s wing had a higher critical Mach number, but interference from the cockpit and engine nacelles reduced the planes overall critical Mach.

[Widewing]

Originally posted by Viking
Brown was talking about tactical Mach number not critical (or limiting Mach number as he called it). Tactical Mach is the maximum speed you can still fight the aircraft. Critical/limiting Mach is the speed where you lose all control of the aircraft.

Inasmuch as Brown never flew the P-47 in combat, I'd lean towards those who did.

Bob Johnson, with whom I had many long conversations, would dispute Brown's assertion that the P-47 was "useless" at 30,000 feet.

You will find that the RAF disagrees with Brown's opinion (as does much of the Flight Test Community on many issues) as well.

Read the RAF's P-47 Tactical Trials report.

Brown has had many detractors, not the least of which was Roland (Bee) Beaumont.

I would not hang my hat on Eric Brown's veracity.

My regards,

Widewing

[Widewing]

Originally posted by Viking
Why would that be relevant? The Spitfire had the highest limiting Mach number of all piston engine fighters and still holds the record for highest Mach attained by a piston engined aircraft: Mach 0.891.  Now, the Spitfire had an elliptical wing, but its wing section was nothing special.

The Me 109 was dived to Mach 0.79 in instrumented tests. Slightly modified, it was even dived to Mach 0.80, and the problems experimented there weren't due to compressibility, but due to aileron overbalancing. P-51 and Fw 190 achieved about Mach 0.80. The P-47 had the lowest permissible Mach number of these aircraft. Eric Brown observed it became uncontrollable at Mach 0.73, and "analysis showed that a dive to Mach 0.74 would almost certainly be a 'graveyard dive'".

Herb Fisher performed over 200 high Mach dives in the P-47D-30, routinely exceeding Mach 0.80, with no issues whatsoever. Brown is an idiot. Here's a sample of actual test data at Mach 0.79, which according to Brown, would be a Graveyard dive. I have the original chart.





I have several more of Herb's charts and access to his log book. Fisher reached Mach 0.83 on several occasions. He thought the aircraft so safe, he took his 3 year-old son, Herb jr. along for a dive at Mach 0.80. I have photos of the event if you are interested... Here's one:



From Herb Fisher Jr, via e-mail:

"Do not know if you have seen the “fastest toddler” picture, well the story is true.  Also, in your article about my Dad, I saw drawings/sketches but not the actual PE219 P-47…here you go." Fisher had a special O2 mask rigged for his son. They hit 575 miles per hour during the dive.

Brown states that a dive at Mach 0.74 would certainly kill you, but a 3 year-old survived Mach 0.80.....


My regards,

Widewing

[Viking]

Originally posted by Widewing
Herb Fisher performed over 200 high Mach dives in the P-47D-30, routinely exceeding Mach 0.80, with no issues whatsoever. Brown is an idiot. Here's a sample of actual test data at Mach 0.79, which according to Brown, would be a Graveyard dive. I have the original chart.
 

The P-47D-30 was the first P-47 that could do that since among other structural improvements it had new blunt-nosed ailerons to improve controllability at high speeds, and to help in dive recovery at these high speeds, electrically-operated dive recovery flaps fitted on the undersurfaces of each wing. All P-47B, C and previous P-47D’s were deathtraps above Mach 0.73.

I could call you an idiot for not knowing that, but I won’t.

Originally posted by Widewing
Brown is an idiot

Eric M. Brown is undisputedly the world’s most experienced test pilot, and having flown all major types of allied and axis aircraft is in a unique position to comment on their relative performance. General Doolittle came to Farnborough to recruit the aid of RAE, and they specifically tested the P-38s and P-47 in service at that time (1943) against the captured 109s and 190s they had available. Calling this man an idiot is a grave insult and what respect I had for you is now gone.

[Knegel]

Hi,

wasnt the initial question, which plane reach faster the ground from 25k alt??

Although the P47 may have had some problems at highspeed, i dont think it was wing compression related. And although it might got stiff controlls, this should stop in lower altitudes, where the air got more thick and the planes dont reach that high mach numbers.

AND, i have no doubt that the P47 did dive faster to the deck, no matter how manouverable it was.
HP + weight should do the job by easy, and thats what the tests also show and what the pilots also are/was telling.

In Ah its the other way around.
(i already did offer my guess, why it is so).

Greetings,

Knegel

[AquaShrimp]

P-51 could only dive to mach .80 ?

[Viking]

Originally posted by Knegel
Although the P47 may have had some problems at highspeed, i dont think it was wing compression related.

It was very much wing compression related. When the plane approached compression speeds the wing would lose lift due to the forming of supersonic shockwaves at the leading edge. This loss of lift resulted in an uncontrolled nose down into a vertical dive. Before the installation of new ailerons and dive flaps with the D-30 model the only thing the pilots could do was throttle back and ride it out. Those that survived managed to pull out at very low altitudes. They were beaten and bruised by the heavy buffeting, and the control stick had beaten their legs black and blue. Early B and C model P-47s could also simply disintegrate in mid air.