# B-29 Escort: P-38, P-47N or P-51H ?



## gjs238 (Sep 27, 2011)

Which would have been best for escorting B-29's; a late model P-38, the P-47N, or the P-51H?


----------



## Lighthunmust (Sep 27, 2011)

With the missions being so many hours long and considering the fact that the fighting capability of each plane being sufficient for the adversaries encountered; I think the pilot comfort provided by the P-47N Thunderbolt would be the best choice.


----------



## Readie (Sep 27, 2011)

Was the P51 or the P47 the 'flying Cadiallac' as it was very comfortable?
I agree with Steve, on a long flight comfort ( and reliability) would feature highly on my list.
Cheers
John


----------



## TheMustangRider (Sep 27, 2011)

As far as I know, the P-51s escorting B-29s out of Iwo Jima did a good job in their escort duties.
When it comes to pilot comfort however, the roomy cockpit of the P-47 seems as one of the best options.
Wonder how the Twin-Mustang would have performed in the role.


----------



## Lighthunmust (Sep 27, 2011)

TheMustangRider said:


> As far as I know, the P-51s escorting B-29s out of Iwo Jima did a good job in their escort duties.
> When it comes to pilot comfort however, the roomy cockpit of the P-47 seems as one of the best options.
> Wonder how the Twin-Mustang would have performed in the role.



I have read somewhere that P-51 pilots were sometimes so exhausted after these missions they had to be lifted out of the cockpit by ground crew. I have never read anything indicating the pilots did not do a good job.

Everything I have read indicates the P-47 was the most comfortable of the three specified escorts. I think of the engines used in the three specified escorts, the R-2800 would be the most reliable and most capable of graceful degradation from combat damage.

The P-82 may have been a better choice than the P-47. Two engines does not mean twice the reliability, but two pilots certainly could reduce fatigue problems, and two sets of eyes are better than one.


----------



## Thorlifter (Sep 27, 2011)

Readie, the P-51 was called "The Flying Cadillac", but I believe it was because it was so smooth to fly and didn't have much to do with comfort.

I agree that I would take the P-47N when it comes to room and comfort for extra long flights.


----------



## syscom3 (Sep 27, 2011)

The P38 had two engines compared to the other two, which is nice to have when your base is hundreds of miles away over water. Considering the poor quality of the Japanese air defenses, even this type of fighter could hold its own.


----------



## jim (Sep 27, 2011)

Two engines are always better than one if the result performance is similar. Also the contre rotating propellers result, in theory ,in a easier to fly aircraft.


----------



## Lighthunmust (Sep 27, 2011)

The P-38 could certainly do the job, but just like the P-82 you have twice as many engines that can have engine problems. I might add twice as many more vulnerable to minor damage or malfunction liquid cooled engines. Certainly limping back home on one engine is a possibility but not a certainty for many reasons. Granted if you only have one engine and it fails limping back home is not a possibility. Any moment now Shortround6 will probably jump in to provide a wonderfully detailed explanation of why the reliability of liquid cooled engines in not a problem followed with a wonderfully detailed explanation of why the reliability of liquid cooled engines is a problem. I think there is a good reason why the USN preferred aircooled engines even on twin-engine designs.


----------



## gjs238 (Sep 27, 2011)

Lighthunmust said:


> I think there is a good reason why the USN preferred aircooled engines even on twin-engine designs.


Didn't this have something to do with the flammability of the coolants used back then?
Not so much in the context of the aircraft (although that is important as well) but in the context of storing the material on the ship.


----------



## Lighthunmust (Sep 27, 2011)

gjs238 said:


> Didn't this have something to do with the flammability of the coolants used back then?
> Not so much in the context of the aircraft (although that is important as well) but in the context of storing the material on the ship.



I don't think flammability was an issue, since there was thousands of gallons of gasoline being stored, but need for storage could have been a minor factor. I think the major factors were maintenance, reliability, and survivability. Where is SR6 or Parsifal when we need them? They can tell you if I am completely daft, and do it with style!


----------



## TheMustangRider (Sep 27, 2011)

Lighthunmust said:


> I have read somewhere that P-51 pilots were sometimes so exhausted after these missions they had to be lifted out of the cockpit by ground crew. I have never read anything indicating the pilots did not do a good job.



Given the amount of hours sitting in a tight compartment, flying over endless ocean and the stressful expectation of fighter resistance after a long flight, I have no reason to doubt the extreme level of exhaustion both fighter pilots and bomber crew members developed after this trans-oceanic flights.
In this context the P-82 must have been most welcomed by fighter pilots if the war would have continued into 1946 and Okinawa would have stayed out of reach for US land forces.
Welcome back to the forums by the way, Lighthunmust


----------



## davparlr (Sep 27, 2011)

At, 30-35k ft, the P-47N has superior performance over the P-51H. At lower altitudes, the P-51H was quite formidable. P-47N did perform successfully over Japan at the end of the war. I guess I would vote P-47N.


----------



## MikeGazdik (Sep 27, 2011)

Over all that water, P-38 for sure! Yes, a twin engine has 2x more of a chance to have an engine hit, or damaged, but....... A single engine has at least 2x more of a chance of not making it home if 1 quits !!


----------



## Lighthunmust (Sep 27, 2011)

MikeGazdik said:


> Over all that water, P-38 for sure! Yes, a twin engine has 2x more of a chance to have an engine hit, or damaged, but... A single engine has at least 2x more of a chance of not making it home it 1 quits !!



On the other hand. Charles Lindbergh chose a single engine aircraft specifically because he thought he was more likely to have problems with a multi-engine aircraft. I think even after the USN switched to jet fighters many of them had one engine. Sure the F4, F14, and F18 all have two engines but many others that saw use on carriers did not. The F35 they want only has one engine if I recall correctly.


----------



## Readie (Sep 28, 2011)

All true, but I'd take the 'flying jug'. Big, comfortable and strong as an ox and with AC radial reliability.
That'll nice nicely Tommy.
Cheers
John


----------



## michaelmaltby (Sep 28, 2011)

"... All true, but I'd take the 'flying jug'. Big, comfortable and strong as an ox and with AC radial reliability."

Me too. . Start off with the roominess and air conditioning. The P47N had the range for Japan operations.

MM


----------



## post76 (Sep 28, 2011)

Cockpit roominess might be somewhat exaggerated when it comes to one over the other. 
The P-47N was the more roomy one, but from a strategic point of view, I'd use the P-51H for escort and use the range and tonnage capability of the P-47N to run medium to low level attack runs. 
Out of the three the P-47N was better suited for that than an escort. 
I read they ran 24 hour raids with the N, still requiring a 10 hour flight, still requiring the range. 

Why does the P-38 always get the back seat on these types of comparisons?
It was an effective escort and proved to be a handful for Japanese aircraft.
The Japanese airmen, when surveyed, said it was their most competitive adversary at high altitude. 
If it wasn't the H but instead the D model P-51, I might instead choose the P-38 for escort.


----------



## Njaco (Sep 28, 2011)

post76 said:


> Cockpit roominess might be somewhat exaggerated when it comes to one over the other.
> The P-47N was the more roomy one, but from a strategic point of view, I'd use the P-51H for escort and use the range and tonnage capability of the P-47N to run medium to low level attack runs.
> Out of the three the P-47N was better suited for that than an escort.
> I read they ran 24 hour raids with the N, still requiring a 10 hour flight, still requiring the range.
> ...



Good point. It does seem next to the Corsair, the 38 was one that won the war in the Pacific.


----------



## wuzak (Sep 28, 2011)

Speaking of the Corsair, couldn't they do the job? Launch from carriers and rendezvous with the B-29s en route, and then return to the carriers?


----------



## Lighthunmust (Sep 28, 2011)

post76 said:


> Cockpit roominess might be somewhat exaggerated when it comes to one over the other.
> The P-47N was the more roomy one, but from a strategic point of view, I'd use the P-51H for escort and use the range and tonnage capability of the P-47N to run medium to low level attack runs.
> Out of the three the P-47N was better suited for that than an escort.
> I read they ran 24 hour raids with the N, still requiring a 10 hour flight, still requiring the range.
> ...


 
I don't think anyone is thinking the P-38 deserves the back seat for any combat performance reasons. I think it really is about pilot fatigue as much as any other factor. The P-38 being a twin and ergonomic issues created a greater work load for the pilot than the P-47N. P-38s could certainly have done the job, it is just that the job would have be more difficult for the pilots to endure.



Njaco said:


> Good point. It does seem next to the Corsair, the 38 was one that won the war in the Pacific.



I hope you are ready to put on your body armor. You may be in for some serious incoming fire from Hellcat pilots and fans. There is also the "Fighter pilots make movies, bomber pilots make history" guys that may want to drop a few eggs on you. 



wuzak said:


> Speaking of the Corsair, couldn't they do the job? Launch from carriers and rendezvous with the B-29s en route, and then return to the carriers?



Even it this were a practical option, do you think HAP Arnold would ever admit to the Navy he needed their help to protect his bombers on a routine basis? Sure the Corsair could do the job, so could the Hellcat but neither would for a variety of reasons.


----------



## Njaco (Sep 28, 2011)

No worries Steve. I make absolutely no claim that I know what I'm talking about when it comes to PTO aircraft!


----------



## TheMustangRider (Sep 28, 2011)

Lighthunmust said:


> Even it this were a practical option, do you think HAP Arnold would ever admit to the Navy he needed their help to protect his bombers on a routine basis? Sure the Corsair could do the job, so could the Hellcat but neither would for a variety of reasons.



If I recall correctly, the USN began making fighter sweeps into Japanese mainland from February 1945 onwards with increasing strength which targeted the remnants of the Japanese Navy, fighter bases and transportation targets among others.
It is my belief that if Arnold and the USAAF would not have been very enthusiastic about asking the USN for fighter support, the USN would not have been much enthusiastic to lend them either.


----------



## gjs238 (Sep 28, 2011)

Wouldn't that be kinda-sorta like asking the USN to station carriers off the coast of Europe to provide fighter support for USAAF bombers?


----------



## Lighthunmust (Sep 28, 2011)

TheMustangRider said:


> If I recall correctly, the USN began making fighter sweeps into Japanese mainland from February 1945 onwards with increasing strength which targeted the remnants of the Japanese Navy, fighter bases and transportation targets among others.
> It is my belief that if Arnold and the USAAF would not have been very enthusiastic about asking the USN for fighter support, the USN would not have been much enthusiastic to lend them either.



You may be right about a lack of enthusiasm from the USN, but then again the USN may have loved the opportunity collect another chip in the interservice rivalry poker game. It may have come in handy after the war when the USAF almost had Congress convinced that Carriers were as obsolete as Dreadnoughts.


----------



## davebender (Sep 28, 2011)

When do you need it?

If you can wait until the fall of 1945 then nothing beats the P-51H. However for WWII era B-29 missions you need an aircraft that was historically available.


----------



## Readie (Sep 28, 2011)

davebender said:


> When do you need it?
> 
> If you can wait until the fall of 1945 then nothing beats the P-51H. However for WWII era B-29 missions you need an aircraft that was historically available.



True, maybe protection was most needed if an bomber was hit and limping home without the protection of the main bomber stream.
Each available escort aircraft has their merits and would do the same job very well.
Cheers
John


----------



## fastmongrel (Sep 28, 2011)

How about the Grumman Tigercat, I am sure it had the range but not sure if it had the altitude.


----------



## davebender (Sep 28, 2011)

One of my favorite aircraft. However given the antagonistic relationship between the WWII era USA and USN I cannot imagine the U.S. Army Air Corps adopting a naval aircraft.


----------



## TheMustangRider (Sep 28, 2011)

Lighthunmust said:


> You may be right about a lack of enthusiasm from the USN, but then again the USN may have loved the opportunity collect another chip in the interservice rivalry poker game. It may have come in handy after the war when the USAF almost had Congress convinced that Carriers were as obsolete as Dreadnoughts.



In that sense I agree, I don't have much detailed information about the inter-service rivalry between the USAAF and the USN but from what I have read the USAAF's struggle was not only against the Luftwaffe in Europe and the IJAF/IJN in the Pacific and CBI, but also for its independence from the Army after the war.


----------



## Readie (Sep 28, 2011)

fastmongrel said:


> How about the Grumman Tigercat, I am sure it had the range but not sure if it had the altitude.



Grumman F7F Tigercat - Wikipedia, the free encyclopedia
Yes, I had forgotten this beauty.


----------



## davparlr (Sep 28, 2011)

davebender said:


> When do you need it?
> 
> If you can wait until the fall of 1945 then nothing beats the P-51H. However for WWII era B-29 missions you need an aircraft that was historically available.



Depends on the altitude. Above 30k its performance is not a lot greater than the D, especially in climb, and nowhere near the P-47N.


----------



## davebender (Sep 28, 2011)

WWII era B-29s did not bomb from altitudes above 30,000 feet. So this shouldn't be a factor.


----------



## fastmongrel (Sep 28, 2011)

davebender said:


> One of my favorite aircraft. However given the antagonistic relationship between the WWII era USA and USN I cannot imagine the U.S. Army Air Corps adopting a naval aircraft.



The aircraft that became the Tigercat was originally an Army project called the XP50 this crashed and the Army transferred its funding to the XP65 the Navy joined in and jointly funded development. The Army dropped out of the project for various reasons possibly the fact it was already commited to the P38. The Navy kept its interest but its not too far off to consider the P65/Tiger for the B29 escort role if different decisions had been made in 1941.


----------



## davebender (Sep 28, 2011)

Now that's an interesting tidbit. 

Why didn't the U.S. Army Air Corps develop a F7F variant ILO the P-61? That would have given us a world class night fighter aircraft. IMO superior even to the RAF Mosquito.


----------



## syscom3 (Sep 28, 2011)

wuzak said:


> Speaking of the Corsair, couldn't they do the job? Launch from carriers and rendezvous with the B-29s en route, and then return to the carriers?



The carriers were only off the coast of Japan a limited number of days. Plus most B29 raids were at night when escort fighters were useless.


----------



## davparlr (Sep 28, 2011)

I don't know much about radar, but the P-61 radar was much larger than the F7F radar being three times the weight. Also, when I saw an F7F, the first thing that impressed me was how small the fuselage was. It was about the size of a fighter, very thin. The radome on the P-61 was huge. I don't know if the F7F could carry the radar the P-61 did. Now about the effectiveness of one compared to the other I don't know. However more power and weight tends to indicate better performance.


----------



## davebender (Sep 28, 2011)

Why?

RAF Mosquitos and Luftwaffe Me-110s got by just fine without a huge radome on their night fighter variants.


----------



## gjs238 (Sep 28, 2011)

Size matters


----------



## davebender (Sep 28, 2011)

That's fine if you are building an AWACs aircraft. But would you employ something like this for a night interceptor?


----------



## wuzak (Sep 28, 2011)

davebender said:


> Why?
> 
> RAF Mosquitos and Luftwaffe Me-110s got by just fine without a huge radome on their night fighter variants.



From the NFXVII the Mosquito was eqipped with the universal nose which would allow the fitment of the MkIX (British) or MkX (American SCR720) radars. The SCR720 was fitted to P-61s.

The F7F night fighter used a smaller, presumably less capable, radar.

The F7F was also later in timing than the P-61.

Would have been interesting to compare the later turbocharged P-61C using the P-61E/F-15 cockpit canopy with the F7F.


----------



## Shortround6 (Sep 28, 2011)

Here is a picture and discription of the SCR720 radar.

The Pacific War Online Encyclopedia: SCR-720 Airborne Radar

Please note that this radar WAS NOT what the P-61 was designed around. Radar was making faster progress than air frames in WW II but when the P-61 was designed the nobody really knew what radar or how big and heavy it would be used when the P-61 went into service. Building too small a plane to hold the 'future' radar would have been a bigger mistake than building too big a plane. 

The dome on the P=61 allowed the dish to turn 180 degrees which allowed for a much larger area of the sky to swept than the older fixed antennaes used on some older night fighters.


----------



## MikeGazdik (Sep 28, 2011)

As great as the P-47N, and P-51H were, I still say the comfort of LONG overwater flights in a twin engine is something that is more important. Be it P-38 or an adaptation of the F7F, either one would be better suited. I have also heard pilots say that one of the biggest causes of phatigue in a P-51 was that growling Merlin. A P-82 is at least a twin, I wonder if they were as "raspy sounding" as the Merlin powered Mustang? The Tigercat would have the silky smooth radials to keep you nice a cozy!


----------



## michaelmaltby (Sep 29, 2011)

Allison engines aren't "raspy" - more "whine". 

MM


----------



## davparlr (Sep 29, 2011)

davebender said:


> Why?
> 
> RAF Mosquitos and Luftwaffe Me-110s got by just fine without a huge radome on their night fighter variants.


When I said the fuselage was thin, I mean really thin, thinner than the F6F/F4U, think P-51 thin. The Mosquito fuselage, which housed the same radar as the P-61, was much bigger than the F7F and I don't think the Bf-110 used a rotating dish antenna. The follow-on purpose built night fighters, the F-89 and F3D were large aircraft to accommodate better and bigger radars.


----------



## Shortround6 (Sep 29, 2011)

The F7F used the same radar as the later wing pods on the F4U and F6F, it scanned a 120 degrees cone compared to the 50 degree up, 20 degree down but 180 degree lateral pattern of the SCR-720. Range of the smaller radar is sometimes given as 10,000yds against bombers (twins?) vs 17,000yds for the SCR-720. SCR-720 also had two 5in CRT displays for the operator displaying different information and a 3in CRT display for the pilot. The AN/APS- 6 had one 3in CRT display, at least for the single seaters, I don't know if the F7F had duplicate displays.


----------



## Siegfried (Oct 2, 2011)

Thorlifter said:


> Readie, the P-51 was called "The Flying Cadillac", but I believe it was because it was so smooth to fly and didn't have much to do with comfort.
> 
> I agree that I would take the P-47N when it comes to room and comfort for extra long flights.



The P-47 turbo supercharger quietened the engine enormously was compared to the P-51. The P-51 engine noise was extremely exhausting on long pacific missions.

The P-47N 'wet wing' was at no range disadvantage to the P-51.


----------



## Lighthunmust (Oct 2, 2011)

Siegfried said:


> The P-47 turbo supercharger quietened the engine enormously was compared to the P-51. The P-51 engine noise was extremely exhausting on long pacific missions.
> 
> The P-47N 'wet wing' was at no range disadvantage to the P-51.



Cadillacs are known for being roomy, comfortable, smooth riding, and quiet. Seems to me little Jim got it wrong; the P-47 was "the Cadillac of the sky" not the P-51.

The P-47N has greater range than the P-51D/K/H. I think "wet wing" is a misnomer. It had wing tanks in addition to the fuselage tank.


----------



## gjs238 (Oct 2, 2011)

Lighthunmust said:


> I think "wet wing" is a misnomer. It had wing tanks in addition to the fuselage tank.


"Wet wing" makes me think of truly wet wings, such as the Seversky/Republic P35 P43.


----------



## gjs238 (Oct 2, 2011)

Siegfried said:


> The P-47 turbo supercharger quietened the engine enormously was compared to the P-51. The P-51 engine noise was extremely exhausting on long pacific missions.


 Couldn't the same be said for the turbocharged P-38?


----------



## windswords (Oct 2, 2011)

Interesting discussion. I read an account for a pilot who flew both the 47 and the 51 and he said the 47 was definitely more comfortable. He also believed it more survivable to combat damage and brought the interesting point that if you had to ditch it in the sea, which would certainly be a possibility when escorting B-29's to Japan, that the P-47 would be safer to ditch because it didn't have the ventral air scoop to catch the water when you tried to put it down. I had never heard of that before. Does anyone know if the P-51 is difficult to ditch in the water? Another question, was the P-51H used in the war? I thought it wasn't available until later. So I don't know if the question makes sense, comparing a plane that was available to one that wasn't.

As for the P-38, the whole reason it didn't have a great success in Europe is because it had problems operating at altitude, especially keeping the pilot warm. In the PTO, altitudes were much lower and heating the cockpit was not an issue. If the P-38 were used to escort the B-29 the altitudes would as great or greater than those in Europe. The later models of the 38 may have gotten this problem sorted out, I don't know.


----------



## drgondog (Oct 3, 2011)

P-51 deadly in ditching - SOP was to bail out.

IMO P-38 best choice because of T/E - no real high altitude issues with J/L models

Probably prefer P-82 if available - high performance escort/two pilots


----------



## Lighthunmust (Oct 3, 2011)

drgondog said:


> P-51 deadly in ditching - SOP was to bail out.
> 
> IMO P-38 best choice because of T/E - no real high altitude issues with J/L models
> 
> Probably prefer P-82 if available - high performance escort/two pilots



I am not sure, but IIRC the ditching characteristics of the P-38 were also poor in comparison to the P-47. I wonder if for much of time during these very long missions the possibility of a P-38 limping home on one engine was low. Is the average reliability of one R-2800 on a P-47 greater than two V-1710s on a P-38?


----------



## FLYBOYJ (Oct 3, 2011)

The P-38 was not a good airplane to ditch either. In the -1 it states to ditch as a last resort.

As far as single engine reliability - excellent. It will cruise up to 225 mph and climb above 20K on one engine, again according to the -1. I believe earlier P-38s had one generator in the left engine so if that engine was lost you lost airframe electrical power in 30 minutes. The -1 also states to operate the good engine at 2600 RPM, 35" manifold pressure and maintain 150 to 200 mph. P-38 reliability on one engine was no different than any other single engine aircraft operating the same engine. 

The R2800 is legendary for its toughness and ability to operate damaged. Any inline engine with a liquid cooling system is a liability, however when overflying large bodies of water, two engines are always better than one.


----------



## Shortround6 (Oct 3, 2011)

Some P-38s are supposed to have flown over 600 miles on one engine.


----------



## Lighthunmust (Oct 3, 2011)

Intuitively two engines should be better for long oceanic flights. So should four be than three and three than two. But reliability is determined by more than the number of engines an aircraft has or we would not have modern twin engined airliners certified for trans-oceanic flights. Furthermore the most famous trans-oceanic flight was made in a single engine aircraft by a pilot who specifically choose not to use a multi-engine aircraft because of reliability concerns. With regard to the P-38 would the frequency of needing to limp home on one engine be a greater liability than the benefit of possibly being able too? Are there any accurate statistics about this? If two engines are so much better than one for flight over the sea, why has the USN from the beginning of the jet age adopted any single engine fighters?


----------



## Shortround6 (Oct 3, 2011)

Modern Jet engines are much more reliable than WW II Piston engines. 

At the time Lindbergh made his flight they were just switching from valve gear (rocker arms,etc) lubricated by grease fittings to being lubricated by the engine oil. having to put the grease gun on the valve gear in mid-flight was a real bummer 

While engine overhaul life is not reliability (chances of break down on any one flight) engine overhaul life was usually under 100 hours in the 20s and could be under 40 hours for some engines.

The US Navy has used a number of single engine jets. The Grumman F9F Panthers/Cougars and F-11F Tigers, F8 Crusader, F4D Skyray, the F3H Demon and the A-4 Skyhawk and others 

These have been matched by the twin engined McDonnell F2H Banshee, , F7U Cutlass, Douglas F3D and more.


----------



## MikeGazdik (Oct 3, 2011)

Lighthunmust said:


> With regard to the P-38 would the frequency of needing to limp home on one engine be a greater liability than the benefit of possibly being able too? Are there any accurate statistics about this? If two engines are so much better than one for flight over the sea, why has the USN from the beginning of the jet age adopted any single engine fighters?



To this I would say, and this would be with any twin. As I lumber along and can see only water, I wouldn't be able to see statistics, but I would be able to see those two props turning. I'm looking more at the psychological factor of having in the back of your mind, that you know you have a 2nd engine if you lose one.


----------



## FLYBOYJ (Oct 3, 2011)

Lighthunmust said:


> Intuitively two engines should be better for long oceanic flights. So should four be than three and three than two.


 Depends on the ability to operate with one or more engine gone also know as "Vmca"


----------



## jimh (Oct 3, 2011)

Lets not forget our highest scoring pilots, Bong and McGuire, used P-38s. I would have to go with the P-38, mostly cause I can't swim  ALSO, the P-38 has no critical engine and twin rudders. You have positive airflow over the rudders no matter which engine quits. The Mustang did it's job admirably albeit maybe not comfortably. I would be very nervous flying behind a Merlin over all that water. VMC for most WWII types is between 125 and 145mph, which gives a safe margin in single engine cruise. For example, the VMC of a B-25 is 145mph, with an engine feathered you can still cruise at 160-170mph. 

jim


----------



## FLYBOYJ (Oct 3, 2011)

jimh said:


> Lets not forget our highest scoring pilots, Bong and McGuire, used P-38s. I would have to go with the P-38, mostly cause I can't swim  ALSO, *the P-38 has no critical engine and twin rudders. You have positive airflow over the rudders no matter which engine quits*. The Mustang did it's job admirably albeit maybe not comfortably. I would be very nervous flying behind a Merlin over all that water. VMC for most WWII types is between 125 and 145mph, which gives a safe margin in single engine cruise. For example, the VMC of a B-25 is 145mph, with an engine feathered you can still cruise at 160-170mph.
> 
> jim



Agree 100%


----------



## syscom3 (Oct 3, 2011)

Siegfried said:


> The P-47 turbo supercharger quietened the engine enormously was compared to the P-51. The P-51 engine noise was extremely exhausting on long pacific missions.



Having heard the P51. P47 and P38 at Chino, I can tell you from experience that the P38 and P47 were quieter.


----------



## evangilder (Oct 3, 2011)

And the scary part is that the P-38s flying today don't have the superchargers, so they would be even quieter operationally!


----------



## Lighthunmust (Oct 3, 2011)

I am not sure but I don't think the P-47 at Chino has a turbo either. GregP or anyone else can you confirm this?


----------



## MikeGazdik (Oct 3, 2011)

If what I have read is true, P-38 Glacier Girl has working turbos. I was lucky enough to see, and touch that gorgeous and historical plane. (sorry for the drool marks!) 

My question is this, if the turbos on most of the turbo aircraft are not working, why are they still so much quieter? Is the exhaust plumbed through hollow shells of the turbo? I have heard Thunderbolts, Lightnings and B-17's first hand, and they are very quiet.


----------



## jimh (Oct 3, 2011)

I don't want to be a stickler for details but only the Turbo Chargers are non functioning on some aircraft. They may be installed for looks but are easily rendered inop. The Superchargers are still an essential functioning part of the engine. The Turbo used on the P-38 and P-47 is the same used on the B-17 and B-24. 

jim


----------



## wuzak (Oct 4, 2011)

The extra exhaust noise from the Merlin on a P-51 may be that it is more highly supercharged than most non-turbo Allisons, and is an indicator of the energy in the exhaust.

Or it may be that the design of the ejector stubs, which Rolls-Royce spent some time on, make for louder exhaust. The ejector stubs were designed to maximise the exhaust energy at certain speeds and engine power settings.


----------



## wuzak (Oct 4, 2011)

Lighthunmust said:


> I am not sure but I don't think the P-47 at Chino has a turbo either. GregP or anyone else can you confirm this?



Greg has told me before that the P-47 has its turbocharger, but that it is inoperative. The reason it remains is to maintain the weight balance in the aircraft, as the C-series turbocharger with intercooler and associated plumbing has more than a little weight.


----------



## jimh (Oct 4, 2011)

The Mustang is noisy because the exhaust stacks are only around 10" long and is not dampened by exhaust plumbing. Next time you see a P-40 run take note of the noise, same engine as the P-38 but, same style of short stacks like the Merlin. The P-47 and P-38 noise is dampened by exhaust plumbing, essentially like a muffler. Round engines have an exhaust "collector ring" that routes engine emissions to a specific outlet, either to the Turbo, or to a common outlet. We had the decibel levels of our B-25 measured a few years ago. The 25 has really short exhaust stacks and is extremely noisy. At cruise it was in the neighborhood of 120db. The B-17 and B-24 were relatively quiet at 90-100db, given they have full collector rings routed to the turbo. 

jim


----------



## MikeGazdik (Oct 4, 2011)

jimh said:


> I don't want to be a stickler for details but only the Turbo Chargers are non functioning on some aircraft. They may be installed for looks but are easily rendered inop. The Superchargers are still an essential functioning part of the engine. The Turbo used on the P-38 and P-47 is the same used on the B-17 and B-24.
> 
> jim



Please be a stickler. Many of the books I have read through the years used supercharging as a generic term, which caused alot of confusion for me as to what was and what was not supercharged, turbocharged, or both. Im a gearhead / car racer, and know what they all mean, but I did not know what to believe as far as what I was reading. Until the internet came along and you can speak "directly" with folks like this forum.

I don't know the specific differences of each, but could the Merlin have a little more "boost" even in low stage than an Allison? A Merlin has a snappier sound to it to me, from idle, and up on throttle, than an Allison as installed in a P-40 or P-39. ( never heard a P-39 first hand ) In my experience with drag race engines, the 3 biggest things that change the sound is camshaft, exhaust valve size, and cylinder pressure, which a supercharged engine has in spades.


----------



## jimh (Oct 4, 2011)

No worries Mike, alot of people are in the same boat. The B-29 also used the same Turbo. The turbo is a pilot operated, exhaust driven, power inducer. The function of the turbo is simple, pump sea level air pressure into the engine to maintain sea level manifold pressure at high altitudes. As an aircraft climbs the air gets thinner and Manifold Pressure slides off. The pilot controlled turbo waste gate can be closed, forcing exhaust the through the turbine, and turning the compressor mounted via a shaft to the turbine. This forces compressed air into the engine and therefore regulating a stable Manifold Pressure. The B-24 and B-17 both have optimum cruise settings of 30" of Manifold Pressure. Here is a great YouTube video from WWII. We differentiate the Turbo Supercharger and the Engine Driven Supercharger by simply saying Turbo, or Supercharger.


_View: https://www.youtube.com/watch?v=mzcP1IYHJmc_

jim


----------



## tomo pauk (Oct 5, 2011)

Simple, crisp to the point


----------



## MikeGazdik (Oct 7, 2011)

Thanks Jimh. I understand the works of both systems. I was wondering if the Merlin has either more static compression or more boost from the supercharger than an Allison,(in P-40 /39) which would make it louder and contribute to its "snappier" sound.

Going back with this original thread question, of the aircraft offered, the P-38L is the choice. Only to be bettered by a Tigercat or a Twin Mustang............maybe!


----------



## JoeB (Oct 7, 2011)

jimh said:


> Lets not forget our highest scoring pilots, Bong and McGuire, used P-38s. I would have to go with the P-38, mostly cause I can't swim  ALSO, the P-38 has no critical engine..


Both engines on production P-38's were critical, stbd engine righthanded, port engine lefthanded. IOW failure of either engine caused both yaw and torque effect to want to roll the plane over to the left/right if the left/right engine failed. The original YP-38 had a no critical engine arrangement (stbd engine lefthanded, port engine righthanded) but the flow pattern in normal operation was not favorable. 

As far as general advantage of two engines, the P-38's problem in ETO/MTO was that air combat loss of one engine made the plane so vulnerable to further fighter attack that the effect on total loss rate wasn't clear, in fact the P-38 had the highest loss rate of USAAF fighters in E/MTO though that was partly a product of more difficult operating circumstances than other types (P-39 had the lowest rate, because a lot of its missions in that theater were defensive patrols considered combat missions but no contact). So it depends to a considerable degree what kind of Japanese opposition is assumed in 1945. In the actual case the P-51 (D's, but using high octane gas and high boost, so considerably outperforming 1944 vintage ETO P-51's) units on Iwo Jima flew only a few escort missions with B-29's (though a couple involved large and furious dogfights with Japanese interceptors) before it was decided it was more worthwhile to have them sweep and strafe against Japanese airfields. Many B-29 raids then were at night anyway (though sometimes also daylight unescorted as the fighter threat diminished). But those P-51's could escape basically any Japanese fighter if they were in trouble; even P-38L's could not do that as reliably v a/c like the Type 4 (aka Frank); P-47N likewise could and P-51H even more so assuming just the Japanese types which reached operation by the end of the war.

Also besides a pilot POV a P-38 represented much more cost to produce and resource to maintain than a P-51; the P-47 had that disadvantage v Mustang too though not as much as the P-38 did.

Joe


----------



## jimh (Oct 8, 2011)

I thought about the critical engine controversy before I posted that. The definition of critical engine is one that most adversly affects handling and performance. The P-38 featured outward turning contra-rotating propellors (as you correctly pointed out) that eliminated torque when both were running normally. I tend to believe the story that the inward rotating propellors caused an area of turbulence between the booms and affected elevator stability, therefore were switched to outward. The power to weight ratio of the P-38, combined with positive rudder and rudder trim authority no matter which engine failed, eliminates the conventional critical engine theory. Watch this video, it is thorough in it's single engine performance parameters. 
_View: https://www.youtube.com/watch?v=ilArlZzLW-U_

During WWII, high performance multi engine flying was in its infancy. Commonly referred to as "single engine flying speed" rather than VMC or critical engine inop, it was taught that there was no reason to fly below this speed for the particular airplane being flown. The P-38 can be flown normally above 120mph, as seen in the Lockheed training film. I've got around 350 hours of PIC in the B-25 Mitchell. Part of the Type rating check ride is a VMC demonstration (at altitude). There are alot of contributing factures to the definition of VMC, which culminates with loss of directional control. The accepted VMC for the B-25 is 145mph. During my flight training and on the checkride itself it was possible to get the airplane down to about 110mph before I could no longer hold heading or alititude. This is well below 145, and the airplane behaves well but it is not what you want during takeoff if there is an engine failure, it will roll over into the dead engine. Which is why it is taught to retard the throttles and land straight ahead in the event of an engine failure on takeoff if single engine flying speed is not attained. see this video of an A-26...
_View: https://www.youtube.com/watch?v=QvplU_5ysjk_ This is what happens when VMC is not attained before liftoff and you have an engine failure. 

I had the good fortune of seeing Lefty Gardner do his P-38 routine on several occasions and he did single engine rolls into the dead engine quite successfully. The P-38 was truely ahead of its time and there is a reason our top scoring aces had success with this machine. It was a reliable, stable gun platform. I would rather be a sitting duck with one engine running than riding down the silk to an awaiting German pitchfork.

The Mustangs that were built in 1944 were the same as the ones built in 1945. In reality there isn't a whole lot of differences between the B and the D models. Add two guns, a bubble canopy, you have essentially identical gun platforms. They certainly fly the same. Alot of blood was shed to get the base up and running on Iwo. If the P-38, P-47, or P-39 were capable of doing the job of escorting they would have been used in that role. The superiority of the D model was proven during Korea, as it was chosen over the H model to serve in country. anyway...thats my .02...this and quarter will get me a cup of coffee.

jim


----------



## FLYBOYJ (Oct 8, 2011)

JoeB said:


> Both engines on production P-38's were critical, stbd engine righthanded, port engine lefthanded.


 Not really depending how you look at it. Like saying a glass of water is half empty as opposed to being half full. Engine out procedures were identical on each engine and although it has been mentioned that the YP-38 flew better than production models during engine out operations, you were still trimming the aircraft in some form to compensate for the dead engine. One could argue that because the left engine on earlier models carried the generator, that was considered the critical engine. I've had this question posed to many multi engine pilot, some of them being test pilots and it seems to come back as a "split decision."


jimh said:


> I thought about the critical engine controversy before I posted that. The definition of critical engine is one that most adversly affects handling and performance. The P-38 featured outward turning contra-rotating propellors (as you correctly pointed out) that eliminated torque when both were running normally. I tend to believe the story that the inward rotating propellors caused an area of turbulence between the booms and affected elevator stability, therefore were switched to outward. The power to weight ratio of the P-38, combined with positive rudder and rudder trim authority no matter which engine failed, eliminates the conventional critical engine theory. Watch this video, it is thorough in it's single engine performance parameters.
> _View: https://www.youtube.com/watch?v=ilArlZzLW-U_
> 
> During WWII, high performance multi engine flying was in its infancy. Commonly referred to as "single engine flying speed" rather than VMC or critical engine inop, it was taught that there was no reason to fly below this speed for the particular airplane being flown. The P-38 can be flown normally above 120mph, as seen in the Lockheed training film. I've got around 350 hours of PIC in the B-25 Mitchell. Part of the Type rating check ride is a VMC demonstration (at altitude). There are alot of contributing factures to the definition of VMC, which culminates with loss of directional control. The accepted VMC for the B-25 is 145mph. During my flight training and on the checkride itself it was possible to get the airplane down to about 110mph before I could no longer hold heading or alititude. This is well below 145, and the airplane behaves well but it is not what you want during takeoff if there is an engine failure, it will roll over into the dead engine. Which is why it is taught to retard the throttles and land straight ahead in the event of an engine failure on takeoff if single engine flying speed is not attained. see this video of an A-26...
> _View: https://www.youtube.com/watch?v=QvplU_5ysjk_ This is what happens when VMC is not attained before liftoff and you have an engine failure.



Great post Jim! One of the pilots I posed this question to summed it up with great simplicity in something like this "if you have to do more work shutting down or flying on one engine as opposed to another, that's you're critical engine." BTW Tony LeVier also maintained the P-38 didn't have a critical engine.


----------



## JoeB (Oct 8, 2011)

jimh said:


> 1. The power to weight ratio of the P-38, combined with positive rudder and rudder trim authority no matter which engine failed, eliminates the conventional critical engine theory.
> 
> 2. The Mustangs that were built in 1944 were the same as the ones built in 1945. In reality there isn't a whole lot of differences between the B and the D models.
> 
> 3. The superiority of the D model was proven during Korea, as it was chosen over the H model to serve in country.


1. I guess it's a matter of semantics but what you are saying is that the P-38 handled satisfactorily on one engine, which a lot of twin bombers of that time didn't, agreed. However AFAIK the definition, not theory really, of a critical engine is one which if lost will leave the torque and yaw of the remaining engine reinforcing one another to roll the plane in one direction, ie usually referring to twins with both engines of same hand, port engine critical if both engines are righthanded, stbd engine if both are left handed. But by the same standard definition, neither engine is critical with counter-rotating engines turning inward, and both are critical with counter-rotating engines turning outboard. 

But even if one assumes the standard definition of criticial engine goes out the window with counter-rotating engines, some counter-rotating twins fly better on one engine than others, and the P-38 a relatively good one, but it never matters much which engine fails on any counter-rotating twin (well except maybe a push-pull twin), just as far as flight characteristics.

2. The planes were basically* the same but the fuel wasn't and WEP boost setting was higher on 7th AF D's at Iwo Jima than what the 8th AF had used, w/ noticeable increase in speed.

*late block D's as used in PTO in '45 had some other bells and whistles like APS-13 tail warning radars, etc.
3. The F-51D was used in Korea rather than any of the somewhat different lightweight Mustangs (H) or morever the apparently more suitable F-47D or N because not only did more F-51D's remain in total USAF inventory (though the difference between total F-47 and F-51 in June 1950 wasn't as great as is sometimes portrayed) but those in ZI were concentrated on the West Coast, and moreover the FEAF still had a small number of F-51D's in inventory in Japan (though not distributed to units). Those were the a/c sent to Korea in late Jun for the ROKAF but which flew some missions w US pilots. Also it had spares stockpiles and remaining maintenance and pilot experience with the F-51D, not with the H nor the F-47. The H would have offered little advantage in Korean conditions anyway, D being adequate in the handful of combats pitting F-51's against NK prop a/c and any prop fighter was heavily outperformed by the MiG-15 later on. But FEAF later regretted the decision of 51 v 47 as F-51 losses soared especially in 1951 v more heavily AA armed Communist field armies by that time. But, the USAF wasn't willing to support operation of multiple prop fighter types in Korea and (commanding general) Stratemeyer was told to forget it when he broached the idea of adding the F-47 later on (see "Stratemeyer Diary").

Joe


----------



## FLYBOYJ (Oct 8, 2011)

JoeB said:


> 1. I guess it's a matter of semantics but what you are saying is that the P-38 handled satisfactorily on one engine, which a lot of twin bombers of that time didn't, agreed. However AFAIK *the definition, not theory really, of a critical engine is one which if lost will leave the torque and yaw of the remaining engine reinforcing one another to roll the plane in one direction, ie usually referring to twins with both engines of same hand, port engine critical if both engines are righthanded, stbd engine if both are left handed. But by the same standard definition, neither engine is critical with counter-rotating engines turning inward, and both are critical with counter-rotating engines turning outboard. *
> 
> But even if one assumes the standard definition of criticial engine goes out the window with counter-rotating engines, some counter-rotating twins fly better on one engine than others, and the P-38 a relatively good one, but it never matters much which engine fails on any counter-rotating twin (well except maybe a push-pull twin), just as far as flight characteristics.



But you're still trimming either engine after it is lost/ shut down regardless of prop direction, the aircraft is still going to roll. A little easier if the prop turns inward, so semantics perhaps?


----------



## windswords (Oct 8, 2011)

JoeB said:


> 3. The F-51D was used in Korea rather than any of the somewhat different lightweight Mustangs (H) or morever the apparently more suitable F-47D or N because not only did more F-51D's remain in total USAF inventory (though the difference between total F-47 and F-51 in June 1950 wasn't as great as is sometimes portrayed) but those in ZI were concentrated on the West Coast, and moreover the FEAF still had a small number of F-51D's in inventory in Japan (though not distributed to units). Those were the a/c sent to Korea in late Jun for the ROKAF but which flew some missions w US pilots. Also it had spares stockpiles and remaining maintenance and pilot experience with the F-51D, not with the H nor the F-47. The H would have offered little advantage in Korean conditions anyway, D being adequate in the handful of combats pitting F-51's against NK prop a/c and any prop fighter was heavily outperformed by the MiG-15 later on. But FEAF later regretted the decision of 51 v 47 as F-51 losses soared especially in 1951 v more heavily AA armed Communist field armies by that time. But, the USAF wasn't willing to support operation of multiple prop fighter types in Korea and (commanding general) Stratemeyer was told to forget it when he broached the idea of adding the F-47 later on (see "Stratemeyer Diary").
> 
> Joe



I may be wrong but wasn't it a fact that most (or all) F-47's in 1950 were assigned to Air National Guard units? I always thought that the Air force didn't want to use the Air Guard units who were familiar with the 47 in the conflict so they went with the more plentiful front line F-51. Whatever the case may be I think that the F-47 would have been the better choice, whether flown by Guard or front line units.


----------



## jimh (Oct 8, 2011)

P Factor is a function of speed. The slower you go the more negative effect Torque has, Spiraling Slipstream, and Gyroscopic Procession. High performance aircraft are slaves to the propellor. With gear and flaps down at 120mph in a P-51 you don't shove all the power into it, you ease in what you need. Otherwise you are just a passenger for a pretty neat roll. A P-47, Hellcat, Corsair, P-38 etc, are no different. A critical engine is critical when if affects directional control (or as Flyboy noted a loss of generator or hydraulic pump) at slow speed, like takeoff or a missed approach. The 38 doesn't suffer from the traditional spiraling slipstream because it has no fuselage and as the air spirals back over the booms and rudders it is actually forcing the nose straight ahead. If you lose an engine while in cruise, or being shot at in an engagement the loss is negligable because of the speed over "Blue Line" and "VMC"...be it a B-17, B-24, B-25 or P-38. You will be more vulnerable no doubt, but controlling the airplane would not be an issue. 

I would love to see your sources for the Mustang. I am always looking to learn more. AFAIK all Mustangs, even today are rated to 61" of MAP, 67" for temporary war emergency power. The Merlin can operate with octanes as low as 87 and as high as 145. The power settings are the same, no manual I have read indicates otherwise. We operate under the instructions dictated by Jack Roush. His shop has produced some of the finest running Merlins in recent times. For longevity we limit the engine to 55" for takeoff...most of us use 45-50". Cruise and aerobatics are done with 35-40". The only time you will see higher MAP's are from the transport series Merlins and Reno racers. Anyway, I'd love to see the source. Thanks

jim

PS I agree...the P-47 would have done much better in Korea than the 51...it was a poor choice by the powers that be.


----------



## JoeB (Oct 10, 2011)

windswords said:


> I may be wrong but wasn't it a fact that most (or all) F-47's in 1950 were assigned to Air National Guard units? I always thought that the Air force didn't want to use the Air Guard units who were familiar with the 47 in the conflict so they went with the more plentiful front line F-51.


The USAF units which flew F-51's in Korea were not equipped with them at the beginning of the war but rather F-80's. So either F-51 or 47 would have been a conversion, but most of the fighter units in Far East AF *had* flown the F-51 a few years earlier, which is why the FEAF was better able to re-adopt that type, having also leftover spares, maintenance experience and even around 20 of the a/c still on hand in depots in Japan. Those particular a/c were used to equip the ROKAF, though they were also used by USAF pilots on combat missions (the 4 victories over NK a/c credited to F-51's June 29 1950 were those a/c flown by USAF pilots). Then a larger number of F-51's were shipped by carrier from the west coast in July, mainly stripped from ANG units in the western US. The 8th (2 of 3 sdns), 18th (all three) and 35th (39th and 40th FIS) Fighter Groups already operating over Korea used those to start converting back from the F-80 to the F-51. The 8th went back to all-F-80 in late 1950, 18th remained an F-51 group until it converted to F-86F's in 1953; 39th FIS became an F-86 unit in 51st FIG in 1952, 40th rotated out of Korea in 1951.

Re: P-51 WEP setting, 67" Hg manifold air pressure WEP was standard in 8th AF (though often exceeded in practice to at least around 70, according to combat reports), but many sources say the 7th AF used 80" on 115/145 fuel. The RAF used 81" on its Mustangs for low altitude V1 hunting. 67> 80 was found in RAF tests to add 30mph at s/l.
One source particularly for RAF v USAAF:
P-51 Mustang Performance

Joe


----------



## drgondog (Oct 10, 2011)

JoeB said:


> The F-51D was used in Korea rather than any of the somewhat different lightweight Mustangs (H) or morever the apparently more suitable F-47D or N because not only did more F-51D's remain in total USAF inventory (though the difference between total F-47 and F-51 in June 1950 wasn't as great as is sometimes portrayed) but those in ZI were concentrated on the West Coast, and moreover the FEAF still had a small number of F-51D's in inventory in Japan (though not distributed to units).
> 
> *My father commande the 35th FBW equipped with 51D's out of Johnson AFB from 1949 to early 1950.*
> 
> ...


 
Simply the 51D's were in Nasty Guard, the 47's were ZI, there were 51's in Japan - someone had to make a decision based on data available at the time.

Erv Ethell was a Squadron CO under my father, and that's how I met and became long time friends w/Jeff Ethell.


----------



## davparlr (Oct 10, 2011)

jimh said:


> I would love to see your sources for the Mustang. I am always looking to learn more. AFAIK all Mustangs, even today are rated to 61" of MAP, 67" for temporary war emergency power. The Merlin can operate with octanes as low as 87 and as high as 145. The power settings are the same, no manual I have read indicates otherwise. We operate under the instructions dictated by Jack Roush. His shop has produced some of the finest running Merlins in recent times. For longevity we limit the engine to 55" for takeoff...most of us use 45-50". Cruise and aerobatics are done with 35-40". The only time you will see higher MAP's are from the transport series Merlins and Reno racers. Anyway, I'd love to see the source. Thanks


 
In April, 1944, the Army Air Forces Materiel Command approved 75" Hg for the V-1650-7 engines. I understand that some commands limited this operationally to 72". Combat reports showed this usage by pilots in ETO. I do not have indications that more boost, 80" Hg, was approved until the -9 engine became available in the P-51H, which, I think, used water injection.

http://www.wwiiaircraftperformance.org/mustang/75inch-clearance-v-1650-7.jpg

http://www.spitfireperformance.com/mustang/combat-reports/357-yeager-6nov44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/353-hinchey-14nov44.jpg


----------



## jimh (Oct 10, 2011)

Very cool read! It was a big deal to break the copper wire on the throttle, to me, its like pulling the pin on a hand grenade. Merlins are sooo fragile. 

jim


----------



## tomo pauk (Oct 11, 2011)

75in hg + ram = 1500 HP @ 25,000, or 1800 @ 10-12,000 ft?


----------



## Shortround6 (Oct 11, 2011)

Which engine are you referring to?

There is going to be a 220-300hp difference between low gear and high gear (takes a lot of power to get 75-80 in of pressure at high altitude) The V-1650-9 in the P-51H shows a 300hp difference.


----------



## tomo pauk (Oct 11, 2011)

V-1650-3, if that was possible for that one?


----------

