P-47: Range, Deceit and Treachery

[MIflyer]

I do not know about pressurization. I have workd a bit on aircraft drop tank systems and the jet drop tanks are pressurized by regulating the 150 PSI bleed air down to about 12-13 PSI with a back-up feature in the regulator. We had a problem with an F-105F climbing out of Savannah that started to stream fuel very heavily and the AB caught the fuel on fire; the crew punched out and one did not survive. We found that some genius at the ALC had decided to stop changing out the auxillary fuel tank pressure regulators on a time compliance basis because "it was too much trouble." The result was there was an unknown number of regulators in the fleet that could fail at any time and in which the backup feature had sat there unmoving so long that it was frozen. Failure of the primary regulator would put 150 PSI into the tanks and that might be what occurred with that F-105F. We could not be sure that had occurred but we were sure that we had a bunch of regulators that could fail at any moment and told the F-105 units to not fly with drop tanks or the bomb bay tank operational. An F-105 without those tanks has a normal endurance of about 30 min.

In WWII the US used the exhaust of the vacuum pump that drove the flight instruments such as the artificial horizon and directional gyro. This would have been no more than 2 to 3 PSI. That is what forces the fuel out of the drop tank; there are no pumps in it. I would have thought that all the drop tanks used that same approach, so I am surprised that 200 gal tank was unpressurized.

 

[Zipper730]

Never knew WWII was a mafia war, did you?

I would normally have given you a bacon for that, but in this case with the Mafia aspect of it -- would you prefer Capicola, Sopressata, or Genoa Salami instead?

I would have assumed most people here see Greg's videos the day they come out and that one came out two weeks ago. Are Greg's videos not appreciated here? This is a sincere rather than rhetorical question. I thought he was a long time commentor as well, but was never sure it was the same guy.

He's a member here? What's his handle?

 

[XBe02Drvr]

I would normally have given you a bacon for that, but in this case with the Mafia aspect of it -- would you prefer Capicola, Sopressata, or Genoa Salami instead?

Nah, only the good stuff: Prosciutto or nothing!

 

[Zipper730]

I don't know how, as a New Yorker, I could have forgotten about Prosciutto -- especially since I'm a big fan of Carbonara (that said, bacon is sometimes used in lieu of Prosciu... I think I understand now).

 

[Peter Gunn]

I don't know how, as a New Yorker, I could have forgotten about Prosciutto

I'm not sure I can countenance such an oversight, I'm asking the mods to ban you for a week as punishment...

 

[drgondog]

"MIflyer, post: 1561553, member: 42472"Good analysis! A few extra points:

1. In the P-51 the pilot had to first burn off fuel from the main tanks (about 30 gal) to allow the excess fuel return to go into the tanks and not be vented overboard. Once that was taken care of the P-51 with the aft fuselage tanks had to burn off fuel for that tank (about 30 gal) to prevent the CG from getting to far aft. Only THEN could the pilot start using the drop tanks. That means that when you punched off your drop tanks you did not have full internal fuel available, but were down probably 50 - 60 gallons or so.

The recommended and usually followed process - unless extremely long range mission - was to warm up, take off and assemble on left wing tank, switch to fuselage tank to climb to altitude and reduce fuse tank to 25-40 gallons, then switch to external combat tanks, alternating left and right, until dry - remembering that the fuel from the next switch position took about 10+ seconds to reach the engine.

25 gallons remaining in the fuselage tank was deemed 'optimal' for cg position during landing. 40+ was deemed in the safe maneuver range.

2. I read of a case where P-51's were flying over Yugoslavia they did frequent abrupt course changes to evade flak traps. They were using drop tanks and a rookie pilot on his first mission noted that when they would make those turns the fuel would slosh and the engine would sputter as a result. He did not like that, so he punched his tanks off, but the other three guys kept theirs, the engine sputtering not being of concern to the old hands. The rookie barely made it back to base since he did not use all the fuel in his tanks.
3. The paper 108 gallon fuel tanks were sent to Wright Field for evaluation and a year later they replied that they were not usable, presumably because after 24 hours they were soggy and had to be defueled and discarded. By that time the 8th AF had found out that they worked and ignored the evaluation."

The 8th figured it out in May 1944

 

[drgondog]

I do not know about pressurization. I have workd a bit on aircraft drop tank systems and the jet drop tanks are pressurized by regulating the 150 PSI bleed air down to about 12-13 PSI with a back-up feature in the regulator. We had a problem with an F-105F climbing out of Savannah that started to stream fuel very heavily and the AB caught the fuel on fire; the crew punched out and one did not survive. We found that some genius at the ALC had decided to stop changing out the auxillary fuel tank pressure regulators on a time compliance basis because "it was too much trouble." The result was there was an unknown number of regulators in the fleet that could fail at any time and in which the backup feature had sat there unmoving so long that it was frozen. Failure of the primary regulator would put 150 PSI into the tanks and that might be what occurred with that F-105F. We could not be sure that had occurred but we were sure that we had a bunch of regulators that could fail at any moment and told the F-105 units to not fly with drop tanks or the bomb bay tank operational. An F-105 without those tanks has a normal endurance of about 30 min.

In WWII the US used the exhaust of the vacuum pump that drove the flight instruments such as the artificial horizon and directional gyro. This would have been no more than 2 to 3 PSI. That is what forces the fuel out of the drop tank; there are no pumps in it. I would have thought that all the drop tanks used that same approach, so I am surprised that 200 gal tank was unpressurized.

The 8th ASC was just working on p-47C/D pressurization in July - but had not released the mod - at the same time the desperate move to use the Ferry tank at the end of Blitz week. Shortly afterward, Republic completed the mod to P-47D-6 (qty 6??) for plumbing and wing rack (not pressurized) and flew several or all to ETO with Field Service Mod notes to perform the mod on existing (and future) P-47D through -15) - but it was a VERY labor intensive modification requiring removing wing skin forward and aft of the spar to attach doublers for spar and all the necessary rack attach support and plumbing lines to feed the combat tank fuel, the pressurization lines from the vacuum pump, the fuel manifold switch, new fuel pumps, etc - which didn't equip most P-47D groups until March 1944.

 

[Vincenzo]

I don't know how, as a New Yorker, I could have forgotten about Prosciutto -- especially since I'm a big fan of Carbonara (that said, bacon is sometimes used in lieu of Prosciu... I think I understand now).

in the carbonara there is neither Bacon or Prosciutto, sure never Prosciutto, you need pig cheek for the carbonara

 

[Peter Gunn]

Dumb question:

Once empty, did Mustangs (or Thunderbolts and Lightnings) punch off their tanks as a matter of course or did they keep them on when RTB if no combat?

I've read where Iwo based Mustangs would keep the 165 gallon tanks after emptying them because they were a bit hard to come by.

 

[pbehn]

Dumb question:

Once empty, did Mustangs (or Thunderbolts and Lightnings) punch off their tanks as a matter of course or did they keep them on when RTB if no combat?

I've read where Iwo based Mustangs would keep the 165 gallon tanks after emptying them because they were a bit hard to come by.

No point in keeping a paper tank, they couldn't be re used.

 

[MIflyer]

Note that the paper tanks were not the only ones used in the ETO, For shorter range missions, such as for covering the withdrawal phase of missions and for photo ops, they often carried the 75 gal metal tanks. That famous picture of LOUIV in formation was a photo op, which explains not only the tanks used but also why it is such a incredibly good photo. It was taken by a professional using professional equipment from the waist gun position of a B-17. And in that case they kept the tanks on.

 

[Peter Gunn]

No point in keeping a paper tank, they couldn't be re used.

Agreed and thank you, I was actually thinking more of the 75 Gallon metal tanks, but I suppose there really was no reason not to punch them off when empty regardless.

 

[GregP]

Hi Guys, the Greg in the video is not me, GregP. Seems like a decent video, but I didn't make it.

 

[drgondog]

Agreed and thank you, I was actually thinking more of the 75 Gallon metal tanks, but I suppose there really was no reason not to punch them off when empty regardless.

The standing rule was to bring the metal tanks home if possible to do so safely

 

[Vic Nighthorse]

Hi Guys, the Greg in the video is not me, GregP. Seems like a decent video, but I didn't make it.

Thanks GregP, I had long wondered.

 

[oldcolt357]

IIRC, one of the 'virtues' of the paper tanks was that they were of no use to the Axis when dropped, as they could not be reused/recycled, unlike the aluminium tanks.

I appreciate Greg doing all of the research to set the record straight regarding various aspects of the fighters used in Europe and the Pacific. I have been aware of the misinformation regarding the "range" comparison of the P51 vs the P47 using drop tanks since I first started reading accounts of aircraft performance over 50 years ago as a boy. I believe the Mustang, while being a great fighter, is very over rated compared to the Thunderbolt and gets that reputation by comparing the P51 of 1944 with the P47 of 1943 and completely ignoring the thunderbolt advancements of 1944 & 45. Greg finding that order from Hap Arnold stopping the purchase of drop tanks clears up a lot of the mystery of what was going on in 1943 regarding fighter range.

 

[pbehn]

Note that the paper tanks were not the only ones used in the ETO, For shorter range missions, such as for covering the withdrawal phase of missions and for photo ops, they often carried the 75 gal metal tanks. That famous picture of LOUIV in formation was a photo op, which explains not only the tanks used but also why it is such a incredibly good photo. It was taken by a professional using professional equipment from the waist gun position of a B-17. And in that case they kept the tanks on.

View attachment 585522

Well I don't think it was normal to take a tail gunner/camera man on ops in a P-51.

 

[eagledad]

Miflyer

Per post 31, that book got me started on my 60 year journey learning about WW2 fighters.

Thanks for the memories!

Eagledad

 

[SaparotRob]

Same here. Love that photo.

 

[MIflyer]

Well I don't think it was normal to take a tail gunner/camera man on ops in a P-51.

Well, there were a few that had a radar operator back there, but I don't think he would have had such a nice camera.

By the way, as Warren Bodie points out in his book Thunderbolt, Gen Arnold may have signed out a letter forbidding drop tanks but in reality early in the war they were hanging them very commonly on P-40's and P-39's as well as 50 gal tanks on even the earliest P-38's, so that order did not seem to have any teeth. Note that the Mustang Mk I and Mk 1A did not have provisions for drop tanks. It was the RAF that appeared to be clueless about drop tanks, as was shown by those few special "Long Range" Spitfires with that hideous tank sticking out of the wing.