P-51 internal fuel question

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H

Hoggardhigh

Airman 1st Class
199
8
Jan 6, 2014
United States
Hi all,

A lot of sources I've read suggest that the Allison-engined P-51 variants had an internal fuel capacity of 90 gallons in each internal wing tank (or 180 gallons total).

My question is this: Could the Merlin-engined Mustangs carry more fuel in the wings than their Allison-engined predecessors, or did all variants have the same wing tank capacity of 184 gallons?

Thanks
 
The P-51 carried its fuel in the wings, later a rear fuselage tank was added, however Mustang Mk Is delivered to the British at the start had capacity to swap ammunition for more fuel.

Posted by drgondog on another thread.
A lot of folks do not realize that the Mark I had much more range than the P-51B based on internal fuel. Each Mark I was delivered with auxiliary fuel cell kits (not self sealing initially but Firestone developed them by end of 1942) which replaced the wing ammo and gun bay - leaving 2x 50 cal in cowl. Straight line range was ~ 1700 miles. Three cells each wing for total increase of 54 Galls to 220+ gal total. I was not able to get specific operational details but obviously had the potential to recon Berlin (or Oslo) in 1942.
 
pbehn said:
The P-51 carried its fuel in the wings, later a rear fuselage tank was added, however Mustang Mk Is delivered to the British at the start had capacity to swap ammunition for more fuel.

Posted by drgondog on another thread.
A lot of folks do not realize that the Mark I had much more range than the P-51B based on internal fuel. Each Mark I was delivered with auxiliary fuel cell kits (not self sealing initially but Firestone developed them by end of 1942) which replaced the wing ammo and gun bay - leaving 2x 50 cal in cowl. Straight line range was ~ 1700 miles. Three cells each wing for total increase of 54 Galls to 220+ gal total. I was not able to get specific operational details but obviously had the potential to recon Berlin (or Oslo) in 1942.
Click to expand...
After reading your post, I now conclude that the Mustang I had a total fuel capacity (in stock configuration) of only about 170 gallons.

Which still doesn't answer my main question: Could ALL Mustangs from the A-36A/P-51A onwards carry up to 92 gallons (184 gals. total) in each wing?
 
Hoggardhigh said:
After reading your post, I now conclude that the Mustang I had a total fuel capacity (in stock configuration) of only about 170 gallons.

Which still doesn't answer my main question: Could ALL Mustangs from the A-36A/P-51A onwards carry up to 92 gallons (184 gals. total) in each wing?
Click to expand...
As far as I know yes. As I read it drgondog drgondog was discussing additional to that, swapping guns for ammunition to give a lightly armed very long range plane. In fact with the P-51 they went the other way with the P-51D increasing the number of guns and ammunition. I don't know if thestandard internal wing tanks were changed between Allison and Merlin versions TBH.
 
Mustang Mk.IA (P-51) and Mk.II (P-51A) all had the same basic internal fuel capacity of 180 gallons. That is consistent across all versions of Pilot's Notes, Aircraft Erection & Maintenance Manuals for those three variants from earliest to last official manuals produced.

50493047811_c4b2b1f6f6_c.jpg
Mustang Mk.I and Mk.IA Fuel by Colin Ford, on Flickr

As noted in the NOTE, there were two auxialliary fuel cells that could be installed in lieu of the wing armament, but this was not intended for operational use, but primarily for aircraft range extension for ferrying purposes.

Of course with the Mustang Mk.II (P-51A) there was the option of adding the underwing drop tanks and the aircraft was plumbed and set up to use them. But the RAF rarely (basically never operationally) fitted their Mustang Mk.IIs with the underwing hard points or used the drop tanks as in the primary role that they were using their Allison engined Mustangs - being the low level tactical reconnaissance role - they had sufficient range to cover all their proposed operational areas solely on internal fuel and the carriage of external drop tanks at low altitude in the face of light and medium flak was considered to be too great a risk if a partially filled drop tank were hit. Also removing the hard points gave them a couple of extra mph through the reduction in drag.

The other key factor to take into account when comparing range on the early Allison engined Mustangs and the later R-R Merlin engined versions, is the difference in the rate of fuel burn per hour for different power settings for the two types of engine. The Allison was generally more fuel efficient (factor of fuel burnt to make HP and operating RPM), so when you look at the Specific Engine Flight Charts for the different engines across the range of power settings from maximum economic cruise to War Emergency Power the Allison burns less fuel.
 
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Lets now look at the Merlin engined Mustangs.

P-51B/C Manuals
50493499156_943f4a63d5_3k.jpg
P-51B-1 Fuel Tanks by Colin Ford, on Flickr

P-51D early
50493498986_c89e2ff178_h.jpg



P-51D/K Late
50493499156_943f4a63d5_3k.jpg



F-51D/K Post War Manuals
50492794493_1aa710fe26_h.jpg
l by Colin Ford, on Flickr

It is interesting to note that in both the Pilot's Notes and the Aircraft Erection & Maintenance Manual for the P-51D early they add the annotation that the 92 US Gallon maximum capacity quoted is the absolute maximum capacity of the tanks, the usual being the normal quoted 90 US Gallon capacity - includes notations on condition and serviceability of the tanks and variations in tank capacity due to manufacturing and installation variances.

So in summation, the basic capacity of the installed WING tanks on the Mustang remained the same from the Allison engined Mustang Mk.I all the way through to the post war F-51D/K.
 
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Hoggardhigh said:
After reading your post, I now conclude that the Mustang I had a total fuel capacity (in stock configuration) of only about 170 gallons.

Which still doesn't answer my main question: Could ALL Mustangs from the A-36A/P-51A onwards carry up to 92 gallons (184 gals. total) in each wing?
Click to expand...
Yes - from NA-91 Mustang IA/P-51-NA and A-36 through P-51A/B/C/K.

The discussion above your pot was about the RAF requested auxiliary wing cells to greatly extend combat radius - presumably for Recon purposes. They were included as kits shipped to RAF.
 
drgondog said:
The NA-73/83 had 170 gal. NA-91 180/184 and each succeeding Mustang until the XP-51F/G/J and J carried 180/184. The 184 was actual maximum capacity of the design wing tanks - but 180 was used for planning purposes to account for warm up and takeoff.
Click to expand...
What do you mean by, "planning purposes"?
 
Hoggardhigh said:
What do you mean by, "planning purposes"?
Click to expand...
As In Mission Plan. If Recon in single ship or Element, no formation assembly required -Start and warm up at 1200 rpm at 20 gal/hr, taxi and take off at MEO, post takeoff and climb to cruise altitude leg at X/Gal Hr for 10 minutes, cruise leg at 60 gal per hour for 300 miles, Loiter at Z feet for 10 minutes at 40 gal/hour, Return leg of 300 miles at 60 gal/hr, Descend to 3000 feet at waypoint M - 40 miles from base, Account for 20 minutes loiter for bad weather, Land, fill out Form 1 - get a scotch at O-Club.

If Combat Escort of maximum effort Fighter Group, all the above but add 1.) takeoff and orbit field as elements of flights take off, form up for Flight, form flights up to squadron, repeat twice to get the Group formed. Add drop externals and fight for 20 minutes - return on fuel remaining.
 
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Denniss said:
Wasn't 184 gal maximum fill but 180 gal maximum usable fuel?
Click to expand...

Actually, yes - and no. Practically speaking, as Colin Ford presented above, the 'extra four gallons per wing' was variable based on condition of the wing tanks and manufacturing tolerances. That said the specs that Firestone and Goodyear built to included the phrase 'not less than' 92 gallons.

Consider that the 5 degree wing dihedral, combined with the pump/supply system was located in wing root, all the internal tan fuel was in a 'downhill' tank.
 
Hoggardhigh said:
Hi all,

A lot of sources I've read suggest that the Allison-engined P-51 variants had an internal fuel capacity of 90 gallons in each internal wing tank (or 180 gallons total).

My question is this: Could the Merlin-engined Mustangs carry more fuel in the wings than their Allison-engined predecessors, or did all variants have the same wing tank capacity of 184 gallons?

Thanks
Click to expand...

I found this here:
Screen Shot 2020-10-22 at 3.32.28 PM.png

Mustang I Testing

This says 140 gallons of fuel in the British version with 2 x .50 cal nose guns, 2 x .50cal and 4 x .30cal wing guns.
Hope this helps.
 
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