Thinking about me P-38 as I'm bored at work...

[bolillo_loco]

Then If I have read the chart right, with out dive flaps you may be at 10,000ft going 420 mph ias and pull out at up to 4 to 5 G's before the A/C will experience buffeting.

Isn't this similar to the dive speed restrictions placed on the Corsair? The corsair would not have had as much problems due to the fact that it operated mostly at altitudes of 20,000ft and below and also it did not pick up speed as quickly as the 38 did in a dive.

I remember the dive and dive recovery section in america's hundred thousand went into great detail for the corsair. it gave 1 G dive limits, 3 G's, and more.

if the placarded limit of 420 mph ias and 4-5 g's pull out with out dive flaps, what is the 1G limit for this plane at 10,000 ft with out dive recovery flaps? It would be higher than 420 mph ias.

thank you.

[wells]

if the placarded limit of 420 mph ias and 4-5 g's pull out with out dive flaps, what is the 1G limit for this plane at 10,000 ft with out dive recovery flaps? It would be higher than 420 mph ias.

 

Yes, it probably would be, but you won't be recovering from that dive.  A 4G pullout at 500 mph TAS will take over 4000 ft to recover and a 2G pullout = 8000 ft, so there appears to be a margin of error built in to the limits to account for terrain height and whatnot.  One could probably dive up to 500 ias at say 2500 ft and be able to pull out at the 7G airframe limit within one wingspan of the water, but I doubt anyone ever tested that!  

[Widewing]

Originally posted by Bonden:
Widewing

re: the ability of the P51 to fly on the primer when radiator damaged.

"Ah, I don't think you'd get very far without coolant regardless of how much you operated the primer. Moreover, it seems like a good way to foul the spark plugs. If you had a minor leak, then I suppose anything you could do to reduce cylinder head temperature is beneficial, to a point. However, a solid hit to the radiator core or a partial severing of a Prestone line will result in powered flight that can be estimated in minutes. Very few minutes."

If you have or can get a copy of "Death Squadron" by Grover C. Hall jr, start read of this subject at page 363 where apparently
John Godfrey returned from near Berlin to England using this primer tactic.

Dont mean to dispute your seemingly vast knowledge of the subject.  
   null

I have referred the source to several friends who own and fly Mustangs, or who have extensive time in the type. However, I suspect that Mr. Hall has made an error, or he has been misinterpreted. I'll post what I learn here.

My regards,

Widewing

[gripen]

Well, there was not much wrong (except price) with the concept of the P-38 if it had been used just as a high-speed bomber interceptor. But during war the AF wanted a long range and high altitude air superiority fighter and for this the concept of the P-51 was far better. And V-1710s with turbos were not particularly good choice; problems still continued at 1944.

I wonder where I have disagreed about aerodynamics with Kelly Johnson? He and his team knew problems and possible solutions very well and they certainly knew that there was no quick and easy fix. And it was not just the profiles but also the fuselage and wing center section between booms which caused a big part of the problems as proved with the modified P-38 with revised fuselage and wing center section and wind tunnel tests.

And no, the P-38 was not a good high altitude fighter. It could not be used as energy fighter at high altitude due to compressebility problems. In horizontal plane it was not particularly maneuverable at high altitude due to limitations of the airframe (Clmax dropped fast when mach number increased) and poor roll acceleration. In all these areas the P-51 was much better at high altitude. BTW the P-51 was THE escort fighter of the USAF, against Germany and also against Japan.

About flight envelopes and Clmax values it should be noted that I posted some useful links some time ago, too lazy to link them here again...

gripen

[Guppy]

F4UDOA,

Yeah, the P-38L didn't do well at the Pax. River conference. I've only skimmed the report, but I got the impression many pilots were unimpressed with the Lightning's quirks (terrible cockpit layout, greater inertia than single-engined types, and so on).

As regards the "high-altitude foxhole" reference, I'll post an excerpt of an interview with a then-Marine major on Guadalcanal.

"The 38s' first deployment forward to Guadalcanal was before I arrived, I think, in late 1942. That initial deployment was not a success. I don't mean to cast any aspersions at all, but I think that some of the pilots who brought the P-38s up there the first time didn't have the confidence in the aircraft that the later pilots did. When I arrived, some of them would be drifting back to Guadalcanal a half an hour before the strike part of a mission returned or had even been heard from. I'm sure that the air corps pilots of that day heard about it, but other pilots, marine, navy, etc., referred to the P-38 as a 'high altitude foxhole.'

...

"In any case, I attributed the initial situation to a hurried transition and the lack of time for confidence-building... later, it was a total turn-around--about the best airplanes and the best pilots we had."

[bolillo_loco]

thank you wells, so with the dive flaps the 420 mph ias for a 4-5G pull out may be exceeded by 20 mph ias according to the pilots manual, this means 440 mph ias and a 4-5G pull out at 10,000ft, isn't this similar to the performance of the F4U-1D according to america's hundred thousand?

In the PTO during most of the war didn't most fighters operate from short unimproved airfields? wouldn't that make the P-38 better suited than the mustang to take off from short strips with heavy loads? also they seemed to make better use of the range of the P-38 in the PTO than the ETO so that with the use of better cruise control methods and 310 gallon drop tanks the 38 actually had more endurance than the P-51D. was or wasn't range and lifting ablity more critical in the PTO?

even in the MTO when bombing the oil fields in rumania, 38s carried one 1,000lb bomb to the target, could the P-51D fly all that distance and carry a 1,000lb bomb load over that distance and still return?

grippen, I do enjoy reading the links you post and other information. I hope to soon purchase some more books and the ones you pointed out to me

Tim Mason: The Secret Years
David Birch: Rolls Royce and the Mustang
Ken Delve: The Mustang Story
Jeffrey Ethell: Mustang - a Documentary History

can somebody explain what all these numbers mean?
 http://naca.larc.nasa.gov/reports/1947/naca-rm-a7f09/index.cgi?page0022.gif

thanks.  

[wells]

Here's the F4u graph:

 

[Widewing]

Originally posted by Widewing:



I have referred the source to several friends who own and fly Mustangs, or who have extensive time in the type. However, I suspect that Mr. Hall has made an error, or he has been misinterpreted. I'll post what I learn here.

My regards,

Widewing

Ok, I have had several responses, and I found the original story as related by Jim Goodson, who flew with Godfrey.

The damage received to Godfrey's Mustang was from flak. Apparently a coolant line was nicked by a shell splinter and developed a relatively minor leak. Typically, a fighter like the Mustang would get into trouble once the cooling system pressure began to fall. If it falls too far, the Glycol will boil in the cylinder head, raising the temperature rapidly. Add to that a slight leak, and you have the makings of big trouble.

Goodson relates that he had used his primer pump to keep cylinder head temps down after taking a hit in his oil cooler. He barely made it back to Britain from the easten edge of France. However, he was flying a P-47D-10 at the time, which has an air-cooled R-2800 radial engine. This motor can survive at high temps much longer than a Merlin. My experience with radials is based upon over 2,000 hours of flying in aircraft powered by the R-2800 and R-1820 as Flight Engineer and Crew Chief.

Godfrey was advised to try the primer to keep the cylinder temps within limits. He did so and managed to get to the North Sea.
However, his hand was in severe pain and the coolant level had dropped to a point where pumping raw fuel into the cylinders was no longer of any value. As the engine began to knock and seize up, he prepared to bail out and stood up in the cockpit, Just then, he spotted the coast of England ahead. His engine quit shortly thereafter and he dead-sticked into a meadow just in from the coast.

In this case, Godfrey suffered a minor leak. Had he lost most of his coolant, he would have watched the engine seize within minutes.

Now, here's what Dudley Henriques has to say. Dudley has about 5,000 hours in Mustangs, having owned a few.

"I've heard this story several times. I wouldn't recommend it!!!
:-))
Excessive overheat in the 51 can mean big time trouble. 121c degrees is the magic number. Anything over 110c is suspect. With a maximum overheat you get a pop off valve release and plenty of white smoke past your ears. With the rad switch on auto, the flap opening is controlled by coolant temp. You can over ride and hold it open for a short time if it's set on auto and see if that brings the temp down. If that fails, and it most likely will at that point, you have a big problem going!! On the right side of the seat you have an emergency coolant flap release you can yank, but once you do, this can't be reset in flight...it's a one shot deal. This extends the coolant flap opening.The problem with the flap release is that if the actuator hasn't failed, you now have to use higher power settings to compensate for the open door. It's a bit tricky.

Bottom line on overheat in the 51 is that if it's an actuator failure or anything else morting the coolant system, I'd go through the procedure above and get the damn thing on the ground in one hell of a hurry!  :-) I don't know about Godfrey, but if it was me, I'd give a lot of thought to using that damn sensitive primer on an already excessively hot and running Merlin.
:-))))"

Gene Greisell adds:
" A Merlin suffering a total coolant loss had, as you said, very few minutes to live.  Between 30 seconds to 2 minutes before it seized,  IIRC.  A slow leak - as you suggested - might - allow, with a combination of low power gliding and rich mixture (and flapping ones  arms out the cockpit maybe), to achieve a considerable range, but somehow I don't think 400 nmiles could be made unless the leak is so insignificant as to be barely noticeable."

You can read Goodson's account of these two events in his book, Tumult in The Clouds.

My regards,

Widewing

[ 12-30-2001: Message edited by: Widewing ]

[bolillo_loco]

Hey thanks a bunch wells!

[gripen]

Thanks Wells, BTW Clmax data from the report of the joint fighter conference results suprisingly similar envelopes.

gripen

[niklas]

is it possible that the P38 was even worse in diving than the charts would you make think? I mean they talk about speed limits in IAS but when i look at the flight operation chart from zenoswarbirdvideos:

 

you can see that the error between IAS and TAS is high. Even near ground (bottom left corner) for continous power it IAS is 12mph higher than TAS (314 / 302). The trend is that with more speed the error becomes larger.
And at high altitude the error is extrem: in 30k  IAS = 252MPH, this is afaik 414mph TAS according to standard conversion tables (factor 1,644) - BUT the chart says TAS = 388MPH. This is an error of 26mph. And for full power (wep) the error would raise maybe to 35-40mph. And at 500mph and high mach numbers....

Of course the dive tables speak about IAS because itīs useful for the pilot - this is what he can read from the instrument. But with this large error the mach limit looks imo higher than it has been in reality. AND itīs imo the reason why you can read a lot of excellent speed claims from P38 pilots. They knew about standard conversion factors, but i think few of them did know about the error of the speed indicator, escepially with increasing mach number

niklas

[ 12-31-2001: Message edited by: niklas ]

[batdog]

Been watching this thread I can see its gone full circle from AH to a lesson in history, which is a good thing really.

 I am NO expert but from what I've read the 38 was an awesome ride that was basicly pushed right into combat w/out much if anything know about many of the "problems" it was to face..ie critical Mach numbers, high alt performance etc. When WW2 hit the P-38 was handsdown the most advanced concept of a fighter we had I think.
   The war dept wanted planes so the 38 was thrust into service. It was the first plane to do those high alt long range escorts w/mostly novice pilots to it.

 The P-38 required a good amount of familiarization I think as well being a high performance TWIN engined fighter. Those poor pilots that where thrust into it from the first part of the war simply had to fiqure it out on thier own in combat. The 8th airforce had no training in place for these pilots. I wonder how many more would of perhaps lived if they'd had some foresight.

 The 38 was very succesful in the Med and PAC theater. WHY was it better there? Well the alt of the fights had alot to do with it as the Euro theater brought about the unknown at the time problems of high alt, long range escorting w/basicly unproven engines at that alt.

 I hear people say the 38 faced inferior planes in the PAC. The first years of the 38's fight in the PAC the Japanese where anything BUT inferior. They had many of the best pilots in the world and the Zero was still a formiable plane. In the Med theater they faced german 109's and Fw's. The held thier own at a miniuim.

 Basicly the P-38 was a plane that under trying circumstances held its own. Due to the time of the war and how it was going against us it wasnt afforded several things that could of made it much better, much earlier... ie engines (perhaps Merlins), Paddle Props (ie the lost K version), etc.

 xBAT

P.S. (edited) Looks like Widewing already said alot of this...lol.

[ 12-31-2001: Message edited by: batdog ]

[gripen]

bolillo_loco,
Well, symbols are described in page two of the that NACA document. Shortly those graphs gives windtunnel data about relations between angle of attack and lift coefficient (left side of the graphs) and relations between lift coefficient and pitching moment coefficient (right side of the graphs) at several mach numbers and various configurations.

About dive flaps and flight envelope it should be noted that at high mach numbers those flaps extended the envelope. In the case of the P-47 dive flaps increased maneuverability above about mach 0.6 and below this speed dive flaps actually restricted maneuverability if controll forces were not the limiting factor. I don't know exact value for the P-38 but based on data on those couple NACA documents, similar mach number appears to be around mach 0.5-0.6.

About loadings of the planes it should noted that a bigger and more powerfull plane can certainly carry a given weight (say a 1000lbs bomb or what ever) much easier than a smaller and less powerfull plane. The P-38 was certainly better than the P-51 in this area.

Generally all WWII era airspeed indicators were quite unaccurate but there was somekind of primitive mach meter in the late P-38 models.

IMHO the P-38 was a good plane for pretty much everykind of tasks at below say 20k if the pilots knew the limitations of the plane and used right tactics (but even in the Pacific and Mediterranean pilots learned this hardway in the beginning). But above that altitude... well, think yourself.

gripen

[Bonden]

Widewing:

"Goodson relates that he had used his primer pump to keep cylinder head temps down after taking a hit in his oil cooler. He barely made it back to Britain from the easten edge of France. However, he was flying a P-47D-10 at the time, which has an air-cooled R-2800 radial engine".

Book says they were in Mustangs. Just relayin what I've read. Perhaps the author did get it wrong or misinterpreted but, I would be disappointed to have to add grains of salt to every WW2 account I have read!

Anyway, appreciated your reply. It's a good read. ("Death Squadron") none the less.  

regards

[F4UDOA]

bollilo_loco,

You do realize that that the F4U chart is in Knots not MPH?

At 10,000Ft the restriction is roughly 425Knots or 490MPH IAS. That is not the same as the P-38 even with dive flaps.

Also the airspeed correction chart for the P-38 indicates an error in airspeed increasing  as speed increases.

At 356MPH IAS the CAS is 340MPH
AT 377MPH IAS the CAS is 360MPH

So you can see an error in airspeed increasing with speed showing a minimum error of -20MPH at 420IAS really being 400MPH CAS.

The F4U also has an error in this regard

At 280Knts IAS the CAS is 287Knts
At 300Knts IAS the CAS is 308Knts

Showing an increase in CAS by +1 KNt for ever 10Knts. So 420KNTS IAS in the F4U is really closer to 430KNTS TAS or 500MPH.

Thanks