P-38 fuel and weights

[SgtPappy]

I noticed that the outer 55 gal fuel tanks aren't used in the P-38J's or L's. 

So does that mean we can only have a maximum of 306 US gallons of fuel?

If so, then I may have found some interesting tests about the P-38J/L that show a much lower weight than the one listed in our game. 
http://www.wwiiaircraftperformance.org/p-38/p-38-67869.html <-- Done on a P-38J-10 numbered AAF, No. 42-67869.
http://www.wwiiaircraftperformance.org/p-38/p-38-13563.html <-- Done on a P-38J numbered AAF No. 43-67570.
http://www.wwiiaircraftperformance.org/p-38/p-38-28392.html <-- Done on a P-38J-15 numbered AAF, No. 28392 with the outer 55 Gallon tanks filled.

Both the J and L in-game hit the 17,500 lb mark when full of fuel and ammo but, obviously, with the lack of the outer wing tanks. The P-38J in the last test hits ~17,300 lbs. with the wing tanks full.

Therefore, assuming we don't have the wing tanks, it seems that the P-38J/L are both overweight since they're about as heavy as P-38J/L's with wing tanks full.

[Pyro]

No plane in AH has more than 5 fuel tanks.  If the real plane had more than 5 tanks, then some of the tanks get combined together.  So total fuel capacity stays the same even though there are fewer tanks.

[Krusty]

"This weight which corresponds to the combat weight of the airplane included 416 gallons of gasoline, full oil, 457.5 lbs. of ballst for 1500 rounds of .50 caliber ammunition,"

Well first of all, the plane in game either has 200rpg x 4 guns or 500rpg x 4guns (800 rounds or 2000 rounds) so the ammo weight isn't the same between the two. Also it says it's ballasted for 50cal but not 20mm. On top of that it says 5 50cal guns in the nose, not 4 guns and 1 cannon. Definitely a nonstandard plane, or an inaccurate report. Either way you can't compare directly to the one in AH.

On top of that, they're testing a higher octane, newer formula gas. It is possible that this gas has a different density and weight than standard avgas. [Edit: But I think most of the weight difference is the guns package in the nose)

[Widewing]

"This weight which corresponds to the combat weight of the airplane included 416 gallons of gasoline, full oil, 457.5 lbs. of ballst for 1500 rounds of .50 caliber ammunition,"

Well first of all, the plane in game either has 200rpg x 4 guns or 500rpg x 4guns (800 rounds or 2000 rounds) so the ammo weight isn't the same between the two. Also it says it's ballasted for 50cal but not 20mm. On top of that it says 5 50cal guns in the nose, not 4 guns and 1 cannon. Definitely a nonstandard plane, or an inaccurate report. Either way you can't compare directly to the one in AH.

On top of that, they're testing a higher octane, newer formula gas. It is possible that this gas has a different density and weight than standard avgas. [Edit: But I think most of the weight difference is the guns package in the nose)

Krusty, it was not possible to install a 5th .50 without major alterations to the mounting. You are reading way too much into a simple typo. Oh, and the specific gravity difference between 150 octane and 100/130 is nil, as is any corresponding weight difference in the fuel.

SOP to use ballast for ammo when testing fighters. Much safer in several ways.

My regards,

Widewing

[Krusty]

Well, going by AH weights (pulled from E6B previously, I made a few notes in a text file) a 50 cal round in AH weighs 0.31 lbs. If they only have 1500 instead of 2000, they're 500 rounds short. Meaning that's 155lbs there alone. Not counting 150 rounds of hispano ammo, which is 0.6 lbs in AH, comes to 90 more lbs.

That's 254lbs right there. That seems to be the weight difference right there.

*shrug*

I'd say a comparison with the exact setup AH has would share the same weight.

[SgtPappy]

No plane in AH has more than 5 fuel tanks.  If the real plane had more than 5 tanks, then some of the tanks get combined together.  So total fuel capacity stays the same even though there are fewer tanks.

Oh I see, alright.

Thanks Pyro, now I know

[CAP1]

Krusty, it was not possible to install a 5th .50 without major alterations to the mounting. You are reading way too much into a simple typo. Oh, and the specific gravity difference between 150 octane and 100/130 is nil, as is any corresponding weight difference in the fuel.

SOP to use ballast for ammo when testing fighters. Much safer in several ways.

My regards,

Widewing

100LL weighs 6 pounds per gallon. if i recall, it's pretty muchg the same weight as the 130 octane that the military used to use.
<<S>>

[Murdr]

Well since the subject has been brought up...The AH P-38J-15 and the AH P-38L-5 are identical in weight. However in real life the L model was heavier than the J.



In this Lockheed shop drawing the first production P-38J-25 and first P-38L-1 are shown side by side.  The L weighs 279lbs more than the J in that case. 

We have neither of those production blocks in the game.  We have a Pre-J-25 block which should be a bit lighter due to the absense of the dive flap and boosted alieron package.

The AH 38L and J no fuel/ammo weight is 14,530. 

Taking the above J-25 empty weight of 13,260
+gun installation=460#
+ pilot 200#
+ oil (26gal*7.5#/per gal)=195#
+ radio 57#
+ oxygen 30#
+ armor 220#
P-38j-25 w/pilot, no fuel/ammo 14,422

Taking the above L-1 empty weight of 13,539
+gun installation=460#
+ pilot 200#
+ oil (26gal*7.5#/per gal)=195#
+ radio 57#
+ oxygen 30#
+ armor 220#
+ aps-13 25#
P-38L-5 w/pilot, no fuel/ammo 14,726

Taking the P-38J-10 from Memo Report No. Eng-47-1706-A
Gross weight of 16,597
-ammo ballast 457#
-additional ballast 100#
-fuel 1,800#
P-38J-10 w/pilot, no fuel/ammo 14,240

Taking the P-38J-15 from No. Eng-47-1749-A

Gross weight 17,363
-ammo ballast 457#
-fuel 2496#
P-38J-15 w/pilot, no fuel/ammo 14,410

The AH models match this chart-

17,400 gross weight
-360 gallons of fuel 2160#
-ammo load 710#
=14,530 which is what the AH model is.
The flight operational chart for the P-38L is identical to the above, hence the AH P-38L is also identically modeled for weight.  Both charts are from the final version of AN 01-75-1.  Flight test figures for the L were not performed until Dec 1945.

The next earliest version of a flight operational chart I have, is from T.O. No. 1-75FF-1 applies to the P-38J-5-LO.

16,200 gross weight
-250 gallons of fuel 1,500#
-ammo load 710#
=13,990lbs w/pilot, no fuel/ammo.

So, between Jun 43 and whenever AN 01-75-1 was published, the "P-38J" gained 540 pounds, and the "P-38L" magically changed engines, added stiffeners for larger capacity hard points, added tail warning radar, but uses the same charts as the J-25.

Yes, I am aware it is only a few hundred pounds.  It just bugs me (and a few others) that they weigh exactly the same in the game. 




While I'm at it, the AH P-38G weighs 13,930 no fuel/ammo,

15,700 gross weight
-260 fuel 1,560#
-ammo 710#
=13,430 w/pilot, no fuel/ammo according to this chart from TO-01-75F-1

[DoNKeY]

Well since the subject has been brought up...The AH P-38J-15 and the AH P-38L-5 are identical in weight. However in real life the L model was heavier than the J.

(Image removed from quote.)

In this Lockheed shop drawing the first production P-38J-25 and first P-38L-1 are shown side by side.  The L weighs 279lbs more than the J in that case. 

We have neither of those production blocks in the game.  We have a Pre-J-25 block which should be a bit lighter due to the absense of the dive flap and boosted alieron package.

The AH 38L and J no fuel/ammo weight is 14,530. 

Taking the above J-25 empty weight of 13,260
+gun installation=460#
+ pilot 200#
+ oil (26gal*7.5#/per gal)=195#
+ radio 57#
+ oxygen 30#
+ armor 220#
P-38j-25 w/pilot, no fuel/ammo 14,422

Taking the above L-1 empty weight of 13,539
+gun installation=460#
+ pilot 200#
+ oil (26gal*7.5#/per gal)=195#
+ radio 57#
+ oxygen 30#
+ armor 220#
+ aps-13 25#
P-38L-5 w/pilot, no fuel/ammo 14,726

Taking the P-38J-10 from Memo Report No. Eng-47-1706-A
Gross weight of 16,597
-ammo ballast 457#
-additional ballast 100#
-fuel 1,800#
P-38J-10 w/pilot, no fuel/ammo 14,240

Taking the P-38J-15 from No. Eng-47-1749-A

Gross weight 17,363
-ammo ballast 457#
-fuel 2496#
P-38J-15 w/pilot, no fuel/ammo 14,410

The AH models match this chart-
(Image removed from quote.)
17,400 gross weight
-360 gallons of fuel 2160#
-ammo load 710#
=14,530 which is what the AH model is.
The flight operational chart for the P-38L is identical to the above, hence the AH P-38L is also identically modeled for weight.  Both charts are from the final version of AN 01-75-1.  Flight test figures for the L were not performed until Dec 1945.

The next earliest version of a flight operational chart I have, is from T.O. No. 1-75FF-1 applies to the P-38J-5-LO.
(Image removed from quote.)
16,200 gross weight
-250 gallons of fuel 1,500#
-ammo load 710#
=13,990lbs w/pilot, no fuel/ammo.

So, between Jun 43 and whenever AN 01-75-1 was published, the "P-38J" gained 540 pounds, and the "P-38L" magically changed engines, added stiffeners for larger capacity hard points, added tail warning radar, but uses the same charts as the J-25.

Yes, I am aware it is only a few hundred pounds.  It just bugs me (and a few others) that they weigh exactly the same in the game. 




While I'm at it, the AH P-38G weighs 13,930 no fuel/ammo,
(Image removed from quote.)
15,700 gross weight
-260 fuel 1,560#
-ammo 710#
=13,430 w/pilot, no fuel/ammo according to this chart from TO-01-75F-1

 

donkey

[Guppy35]

So is my 38G too heavy or too light.  Last time we went through this my G gained weight

[Murdr]

So is my 38G too heavy or too light.  Last time we went through this my G gained weight

"Your" 38G is too heavy...I'd have though you'd have lost the holiday season/winter weight gain by now  

The current AH 38G seems like a close match for the AN 01-75-1 P-38H chart (which is 400 lbs heavier than the chart I posted).  I don't know, it might well be modeled to hit data points that I'm not privy to.  Just saying I have the above info on the G and the weigh and balance chart that it is derived from.

[Guppy35]

"Your" 38G is too heavy...I'd have though you'd have lost the holiday season/winter weight gain by now  

The current AH 38G seems like a close match for the AN 01-75-1 P-38H chart (which is 400 lbs heavier than the chart I posted).  I don't know, it might well be modeled to hit data points that I'm not privy to.  Just saying I have the above info on the G and the weigh and balance chart that it is derived from.

How's about we upgrade it to a 38H and call it even?

[SgtPappy]

I approve of Guppy's post.

But hey, a few hundred pounds is always noticeable to the best pilots. I would feel much happier if the weights were fixed and the tiny bit of performance changed with them.
Thanks for the tests Murdr.

[DoNKeY]

I approve of Guppy's post.

But hey, a few hundred pounds is always noticeable to the best pilots. I would feel much happier if the weights were fixed and the tiny bit of performance changed with them.
Thanks for the tests Murdr.

Agreed.

donkey

[Jester]

I approve of Guppy's post.

But hey, a few hundred pounds is always noticeable to the best pilots. I would feel much happier if the weights were fixed and the tiny bit of performance changed with them.
Thanks for the tests Murdr.

Seconded.   

<S>!