Warbird Information Exchange

A recent interesting post discussing the arming of a P-40 with dummy ammo brought up several questions.

During the war, when a fighter was fully armed and loaded, did this extra weight have an extreme affect on the handling of the aircraft? Would the aircraft become noticably more nimble with the amount of ammo expended?

When discussing P-51 escort missions to say Berlin, when wing tanks were dropped for one reason or another, how long roughly could a mustang stay in the area of combat.

I also remember a well viewed film of four mustangs dropping their wing tanks and one mustang only dropped one tank, the other stayed on, would that mustang have had to turn back to base ASAP?

Could a mustang dogfight with wing tanks still attached if need be? Or would a tight turn of any sort with full wing tanks tear off the wings?

What were the rules for dropping tanks? ...if an escort flight did not see any hostile aircraft to the target and back, would the escorts return to base with their tanks attached or would they drop them anyway?

Didn't Tommy Mcguire die trying to dog fight with tanks on.

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I think on the long P-51 missions you had something like 15 minutes for combat and then you had to come home.

McGuire tried a tight turn at low altitude and the fuel in the partially full drop tanks shifted moving the CG on the P-38 causing it to crash.

Mark H

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In general...

Lift,thrust,weight,drag,&basic physics...

Ammunition - never a major factor in the load of a normal fight aircraft; compared to a modern warbird, they were more laden, but with period batteries, radios, armour, guns etc. Even cannon ammo wasn't a large weight as a percentage, I understand. Happy to be corrected.

Fuel. Use the drop tanks first, and drop them ideally before entering the combat zone. The P-51D was, I think, unusual in requiring another (the fuselage) tank to be emptied / used before you entered combat, as it affected the c of g. I'm sure we'll have a Mustang expert along soon. So, yes, if you had to drop tanks with fuel in, your escort mission was busted; but I don't know that happened to the 8th AF.

If you had a full tank hang up (which you'd only be dropping in an emergency/under attack) then it would affect handling, both weight and drag, but would probably depart. You'd not want to linger, or land with it on. An empty one, drag, but no significant weight. In both cases a bit of 'g' manoeuvring might lose it. Anyone got firsthand reports?

HTH

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

James, I'm sure that I remember reading more than once that some fuel from the fuselage tank was used first before the drop tanks. The reason for this was that pilots didn't want to enter combat with a full fuselage tank because of the adverse handling.

Thanks Robbo. My understanding was you didn't want to be flying for long with a full fuse tank, so that made sense. Handling, IIRC was marginal with that rear fuselage tank full (irrespective of having drop tanks or not, which were near or on the fore-aft c of g).

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

P-38s and P-39s would have shift of CG because of the location of the ammo. The wing mounted tanks, bombs, and ammo would have very little effect due to it being close to the CG. I've heard from old timers who flew P-51s with the fuselage fuel tanks that it had a very aft CG and was quite dangerous to fly with if you tried to do any aerobatics with it full. I think the procedure was to takeoff on the main tanks, switch to the fuselage tanks, when empty, switch to the drop tanks, then the main tanks.

As an aside, I know for a fact Hub Zemke had some of the .50s on one of his P-47s removed to save weight and increase performance.

Zack

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Thanks Zack, and he wasn't alone, when I think about it. Ammunition (and / or gun removal) has been done to get a bit more 'extra' on occasion from the Great War onwards. How much of a real difference it made, like polishing a/c for a couple of extra knots, I don't know. I suspect some of it was morale.

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

On a P-51 at a combat weight of ~9,000 lbs, removing two guns and their ammo would eliminate at least 300, possibly as much as 400 lbs. That would increase acceleration by 3-4%, increase rate of climb by more than that, and would provide a noticable increase in roll rate. Depending on what situation you found yourself in, that performance increase might make a meaningful difference.

Here is some operational considerations and procedures for the P-51B/C/D/K as all had the fuselage tanks. The early B'e were retrofitted.

The first procedure was to drain the fuse tank down to 25 gallons to get the Cg range where it belonged.

The next process was to swith to external tanks to fly to the target if unmolested. If engaged before target and external tank burn, that left you with 184 gallons in the wings and 25 gallons in fuse - roughly equal to two 110 long range drop tanks.

Mustangs occasionally failed to drop one or both tanks, and obviously would suffer in performance but it was known to happen. The external tanks fed through a glass tube which broke when the tank was dropped. If that borke prematurely then the a/c in question had to turn back, usually with one escort.

IIRC the Merlin burned about 220-250 gallons per hour at war emergency - but rated at 67" (later 72 w/150 Octane) only for 5 minutes.

Cruise consumption going in to the target was about 50 gal per hour at 1800 rpm/23" hg for the 1650-7.

Once you caught up to the bombers your altitude and cruise settings woul be higher, and if you were 'essing' over the tops your effective specific fuel consumption would increase even more because while your were doing 220 IAS over the top in the "ess", you were only travelling in a straight course at the same speed of the bomber. In this case 150 IAS at 25,000 feet.

So the mission planner looked to warm up time, take off and assembly time, climb to altitude - all at different settings until cruise altitude - then distance to RV point and altitude.. then time and fuel consuption rate until Break escort point.

I believe 15-30 minutes of reserve was allocated for combat and 30 minutes reserve for unexpected headwinds and weather on return.

The 51D with full internal fuel and 1800 rounds of 50 cal weighed about 9600 pounds. Max Gross Take Off was about 10,800 pounds with two 110 gallon drop tanks.

The P-51B in similar config was about 500 pounds less than the D.

I know you are right - and that represented 2 x69 pounds just for the 50's alone and I'm guessing another 100 pounds for 600+ rounds of ammo.

Excelent post, drgondog, thanks.

Thanks Kyleb & drgondog, I never was much cop with weights and measures!

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com