Dive limits

[Greyman]

How about the big bombers? Anyone got the limits for the B-24, B-17?

I can't help with the American bombers but I have the Pilot's Notes for the following:

Stirling I, III, IV
(pressure head under fuselage) - 325 mph IAS
(pressure head on mast) - 295 mph IAS
(ASI connected to static vents) - 310 mph IAS

Halifax III, VII
(w/o mod. 1423 or 1448) - 280 mph IAS
(w/ mod. 1423 or 1448) - 320 mph IAS

Lancaster I, III, VII, X
360 mph IAS

 

[tomo pauk]

NACA report on the YP-38 full-scale wind tunnel test, along with recomendations to increase the 'speed limit' that goes along with delay of the onset of compressibility:

https://crgis.ndc.nasa.gov/crgis/im...d_Diving_Tendencies_of_the_YP-38_Airplane.pdf

 

[Greyman]

Great thread on fighter plane dive limits. How about the big bombers?
Anyone got the limits for the B-24, B-17?

Info from Pilot's Notes I've come across in the intervening years:

Liberator II, IV, V
310 mph IAS

Fortress II, III
(w/o mod.161) - 220 mph IAS
(w/ mod.161) - 270 mph IAS

 

[Old Wizard]

 

[daveT]

 

[DarrenW]

From the wartime F6F-3/5 Pilots Handbook:

This is below the altitude of 10,000 feet. Also, the dive limits of later built F6F-5s (and those with Model F6 Service Change #75 incorporated) were increased by 10 Knots.

 

[Zipper730]

Dive limits for the P-61.

There's a lot of confusion: Some of the dive figures indicate around 0.60-0.62 mach, however 415 mph indicated at 25,000 feet indicate almost mach 0.84

 

[Zipper730]

So far, from analyzing everything I got the following except the Fw-190 because my table only works in increments of 2,500 feet and that doesn't perfectly work out for metric

Chance Vought F4U

• 275 KIAS @ 30,000 ft: Mach 0.706*
• 307 KIAS @ 25,000 ft: Mach 0.711*
• 340 KIAS @ 20,000 ft: Mach 0.715*
• 375 KIAS @ 15,000 ft: Mach 0.721*
• 390 KIAS @ 10,000 ft: Mach 0.689*
• 410 KIAS @ Sea-Level: Mach 0.6198*

I'd almost swear I remember hearing that it started to run into problems at 0.73...

De Havilland Mosquito

FB.VI Airspeed Limits

• No external ordinance or tanks: 450 mph / 390 kts
• External tanks: 400 mph / 388 kts
• External ordinance/External fuel tanks half empty/Bomb-Door limit: 350 mph / 304 knots

Overall Mach Limits

• Mach 0.75: Placard Limit
• Mach 0.77: Maximum attempted

Hawker Tempest Mk.V

• 370 mph indicated @ 30,000 ft: Mach 0.823*
• 410 mph indicated @ 25,000 ft: Mach 0.823*
• 450 mph indicated @ 20,000 ft: Mach 0.823*
• 490 mph indicated @ 15,000 ft: Mach 0.819*
• 540 mph indicated @ 10,000 ft: Mach 0.829*

The plane's aerodynamic limit in wind-tunnel tests was 0.83, so it came pretty close to the potential

Bell P-63A

• 525 mph indicated @ Sea-Level: Mach 0.69*
• 500 mph indicated @ Sea-Level - 10,000 ft: Mach 0.657 - 0.768*
• 450 mph indicated @ 10,000 - 15,000 ft: Mach 0.691 - 0.752*
• 400 mph indicated @ 15,000 - 20,000 ft: Mach 0.669 - 0.732*
• 350 mph indicated @ 20,000 - 25,000 ft: Mach 0.64 - 0.705*
• 300 mph indicated @ 25,000 - 30,000 ft: Mach 0.604 - 0.669*
• 250 mph indicated @ 30,000 - 35,000 ft: Mach 0.558 - 0.621*

De Havilland Sea Hornet

• 350 KIAS @ 5,000 - 10,000 ft: Mach 0.571 - 0.618*
• 340 KIAS @ 10,000 - 20,000 ft: Mach 0.600 - 0.715*
• 260 KIAS @ 20,000 - 30,000 ft: Mach 0.547 - 0.667*
• 260 KIAS @ 30,000 - 41,500 ft: Mach 0.667 - 0.832*, **

Footnotes
*: Mach number is based on a table I have and rounded to the third digit
**: The aircraft only goes up to 41,500 feet if I recall and I have 40000 and 45,000 feet.

 

[DarrenW]

So far, from analyzing everything I got the following except the Fw-190 because my table only works in increments of 2,500 feet and that doesn't perfectly work out for metric

Chance Vought F4U

• 275 KIAS @ 30,000 ft: Mach 0.706*
• 307 KIAS @ 25,000 ft: Mach 0.711*
• 340 KIAS @ 20,000 ft: Mach 0.715*
• 375 KIAS @ 15,000 ft: Mach 0.721*
• 390 KIAS @ 10,000 ft: Mach 0.689*
• 410 KIAS @ Sea-Level: Mach 0.6198*

I'd almost swear I remember hearing that it started to run into problems at 0.73...

De Havilland Mosquito

FB.VI Airspeed Limits

• No external ordinance or tanks: 450 mph / 390 kts
• External tanks: 400 mph / 388 kts
• External ordinance/External fuel tanks half empty/Bomb-Door limit: 350 mph / 304 knots

Overall Mach Limits

• Mach 0.75: Placard Limit
• Mach 0.77: Maximum attempted

Hawker Tempest Mk.V

• 370 mph indicated @ 30,000 ft: Mach 0.823*
• 410 mph indicated @ 25,000 ft: Mach 0.823*
• 450 mph indicated @ 20,000 ft: Mach 0.823*
• 490 mph indicated @ 15,000 ft: Mach 0.819*
• 540 mph indicated @ 10,000 ft: Mach 0.829*

The plane's aerodynamic limit in wind-tunnel tests was 0.83, so it came pretty close to the potential

Bell P-63A

• 525 mph indicated @ Sea-Level: Mach 0.69*
• 500 mph indicated @ Sea-Level - 10,000 ft: Mach 0.657 - 0.768*
• 450 mph indicated @ 10,000 - 15,000 ft: Mach 0.691 - 0.752*
• 400 mph indicated @ 15,000 - 20,000 ft: Mach 0.669 - 0.732*
• 350 mph indicated @ 20,000 - 25,000 ft: Mach 0.64 - 0.705*
• 300 mph indicated @ 25,000 - 30,000 ft: Mach 0.604 - 0.669*
• 250 mph indicated @ 30,000 - 35,000 ft: Mach 0.558 - 0.621*

De Havilland Sea Hornet

• 350 KIAS @ 5,000 - 10,000 ft: Mach 0.571 - 0.618*
• 340 KIAS @ 10,000 - 20,000 ft: Mach 0.600 - 0.715*
• 260 KIAS @ 20,000 - 30,000 ft: Mach 0.547 - 0.667*
• 260 KIAS @ 30,000 - 41,500 ft: Mach 0.667 - 0.832*, **

Footnotes
*: Mach number is based on a table I have and rounded to the third digit
**: The aircraft only goes up to 41,500 feet if I recall and I have 40000 and 45,000 feet.

This is some very interesting stuff. I see that some flight manuals give a never exceed or max dive speed with no mention of altitude. I assume that if it's not stated then the speed is at an altitude below 10,000ft. Would make sense. The pilot would then have to calculate what that speed would translate to at any given altitude, knowing that IAS and TAS differ with changes in altitude.

 

[grampi]

Where any fighters able to break the sound barrier in a dive?

 

[Shortround6]

The F-86??


No piston engine fighter could come close and no WW II jet could either. Even coming close (over 0.90 mach) would result in loss of control and/or the plane coming apart.

A Spit once hit 0.92 but lost it's prop doing it and the pilot only recovered control after loosing thousands of feet of altitude. And then climbing thousands of feet due to being tail heavy

Wings were also bent slightly.
People may very well argue with the actual accuracy of the reported speed but no other piston engine aircraft came close.

 

[Zipper730]

The F-86??

That's right, even the prototype could

A Spit once hit 0.92 but lost it's prop doing it and the pilot only recovered control after loosing thousands of feet of altitude. And then climbing thousands of feet due to being tail heavy

I think you might be mixing up several events

• The Spitfire VIII was involved in numerous dive tests due to the new steel spar which theoretically allowed dynamic loads to something like 825 mph (I'm not sure if the wing was remotely aerodynamic to that point, it'd be around Mach 1.25), the fuselage, tail and prop could not take it even if the wing could.
• Placard limit was 0.85 Mach
• There was one dive where the prop tore loose and the pilot ended up gliding the plane in: The plane pitching up I don't recall, but I do remember the loss of the prop
• One dive reached a successful speed of Mach 0.891
• A Spitfire PR was modified with an all-moving tail to test the validity of the concept for the Miles M.52, and achieved 0.92 Mach
• A Spitfire PR lost control at high altitude after stalling: The aim was to test environmental conditions at high altitude; the pilot ended up overspeeding the airplane but pulled out and later on it was found he had acheived 0.94. It was 1952 if I recall

 

[fubar57]

Spitfires Helped Lead the Way to Supersonic Flight

 

[pbehn]

None of these high mach values are in any way verifiable as far as Mach number because they used pitot tubes in a dive. They were certainly going very fast but when your method of recovery is to scrap the propeller and therefore change the trim then you have survived a potentially fatal accident not set a record. The Spitfire was a great aeroplane, it doesn't need outlandish claims of breaking or coming close to breaking the sound barrier to gild its reputation.

Chuck Jaeger was dismissive of anyone claiming to have broken the sound barrier in WW2 aircraft and he more than most should know. For me I have never seen conclusive proof that any Spitfire ever broke its "placard limit", the one that lost its prop and bent its wings certainly proved why such limits exist, it may have broken it, but it was wrecked and that proves a point.

 

[Zipper730]

Spitfires Helped Lead the Way to Supersonic Flight

It's honestly a good question who did break the sound-barrier first: Honestly I wouldn't be shocked if an Me-262 pilot did it in April 1945

 

[Shortround6]

It's honestly a good question who did break the sound-barrier first: Honestly I wouldn't be shocked if an Me-262 pilot did it in April 1945

Most us would be shocked, Much like the bent and battered Spitfire any 262 that got that close to the sound barrier would have gone into lawn dart mode.
The plane would have been uncontrollable by the pilot and either crashed or broken up in flight before actually making a sonic boom.

There are several modern built Me 262s flying with General Electric J-85 engines (or commercial equivalent) and they have same placard never exceed speed as the WW II versions. ANY speed in excess of the placard speed and the owner/operator has entered the world of test pilot.

Please note there were a number of jets built in the late 40s that were as fast or faster than the Me 262 and most of them are never reported as breaking the sound barrier, even in a dive.

 

[pbehn]

It's honestly a good question who did break the sound-barrier first: Honestly I wouldn't be shocked if an Me-262 pilot did it in April 1945

Chuck Jaeger did. A Grand slam bomb which was basically an aerofoil weighing 10 tons didn't go supersonic dropped from 18,000 feet. The sound barrier is like an exponent, the closer you get to it the harder it is to get even closer and still harder to pass it. At my fittest I could run 100m in 12 seconds, some fast soccer players can do it in 10.5 seconds, the best sprinters go under ten seconds, how close are they to Usain Bolt at his best? In practice, not close at all, that last half second means they don't make the photo finish. Mach 0.9 or 0.94 in a dive measured by a pitot tube, is actually not even close.

 

[Zipper730]

Most us would be shocked

Okay, to be clear -- we're talking manned vehicles: Bullets have been going supersonic since the start of the 20th century if not earlier...

any 262 that got that close to the sound barrier would have gone into lawn dart mode. The plane would have been uncontrollable by the pilot and either crashed or broken up in flight before actually making a sonic boom.

I'm just basing it on a claim that a pilot made back in 1945 involving a mach-jump effect he noted (well he noted the speed gauge hovered for awhile then increased), when it was discussed in the subject of supersonic flight, he mentioned the matter and with everything said he speculated he might have went through.

A recent study said it was theoretically possible but it only would apply under a very limited set of circumstances: I do remember it being stated that he pulled back on the stick and then used stab-trim to add to it. This could damage the plane, but I'm not sure if it would always happen.

Chuck Jaeger did.

And in level flight, which is still a bonus point.

A Grand slam bomb which was basically an aerofoil weighing 10 tons didn't go supersonic dropped from 18,000 feet.

The idea was to drop it from 40,000 or 45,000 feet initially

Mach 0.9 or 0.94 in a dive measured by a pitot tube, is actually not even close.

Actually the 0.94 figure was done with elaborate atmospheric testing equipment (remember how I said it was being used?), though this was in 1952.

 

[pbehn]

The idea was to drop it from 40,000 or 45,000 feet initially
Actually the 0.94 figure was done with elaborate atmospheric testing equipment (remember how I said it was being used?), though this was in 1952.

My point was that it had no appendages at all apart from 4 comparatively minute tail fins. If it was an aircraft with wings, a tail and pilot dropped from 40,000ft by the time it reached 20,000 ft it would have to be pulling out because it weighs ten tons.

 

[Graeme]

Actually the 0.94 figure was done with elaborate atmospheric testing equipment (remember how I said it was being used?), though this was in 1952.

That was Edward Powles...

Edward Powles - Wikipedia