Concept of ferry tanks on fighters?

[Browning303]

Hi all, had a search for this topic and can't seem to find anything. Why didn't WW2 fighters have a second fuel tank as standard ? I'm thinking particularly of the 109 and spitfire which each had one main tank of around 80 gallons I believe. Both suffered operational problems due to their lack of range. Notoriously the 109 during the Battle of Britain, but also the Spitfire during attacks on the Luftwaffe over France and their inability to escort allied bombers to Germany and back.

Why not include a second tank towards the back of the fuselage in both aircraft? I appreciate it would affect aerodynamics but the logic would be it could be used for ferry flights. It could also be used for longer trips into Europe if this tank was selected first, so when arriving in the combat area you have a full tank of fuel in the main tank. Imagine the difference this would have made to the 109s on the battle of Britain. I appreciate if it seriously affected maneuverability the fuel would need to be burned before combat as you couldn't jettison it like you could a drop tank. But what if the 109s even just carried an extra twenty gallons during the Battle of Britain? It would enough to get them to altitude and to be approaching the British coast with a full tank of fuel?

Could be a totally unworkable idea for a fighter, I dunno. Just thought it would be interesting to discuss because I know both aircraft were designed purely to intercept bombers over their home territory and not to fly in an expeditionary way , which is what both of them ended up doing.

 

[tomo pauk]

The BF 109 already have had the main (and only) fuel tank in the rear part of fuselage. On Spitfires, the 29 gal tank was used for deployment, but not for combat (IIRC it was not self-sealing, nor protected in any particular way), but that is in 1942. Adding another 70-90 gals (500-650 lbs rougly) at the rear part of early aircraft with light engines will mean tht centre of gravity is so disturbed that fighters are going to crash easily, without the enemy action.
Drop tank was a much more sensible idea, it was already used in 1930s well before ww2 started, however LW dropped the ball with not installing them on Bf 109Es until too late for the BoB.

 

[tyrodtom]

I don't know how far to the rear you mean, but just 20 gallons is 120 lbs, plus the tank.
You place that too far to the rear and you overcome the aircraft's ability to be trimmed .

In other words as soon as you try to lift off, the tail stays on the ground, and no amount of forward elevator can get it off the ground. A stall on takeoff with full tanks is probably going to be fatal.

The Mustang had a rear tank, but not as far back as you may think. About between the back of the bubble canopy, and fuselage insignia. It severely restricted manuvers until it was drawn down quite a bit.

 

[Shortround6]

The P-36, and by extension, the P-40 did have ferry tanks, The main fuel tanks were in the wing under the cockpit and the ferry tank was behind the pilots seat.
the French crashed at least one Mohawk trying to stunt fly or perform acrobatics with too much fuel in the ferry tank.

The 109 was in a bit of bind, it was physically smaller and had been designed around a 700hp engine with 235-270(?) liters of fuel, they found room for 400 liters and added self sealing with the DB 601 engine and the later "E" models. I am not sure how much more you would be able to put in the plane without resorting to a multitude of small fuel tanks spread through the plane.

The Spitfire had a different problem. In the design stage (when the airplane is still "rubber" and can be stretched or compressed) the Spitfire was saddled with that fixed pitch prop and sense all three aircraft had to operate out of their respective countries existing airfields there was only so much weigh to could add and still keep the take-off performance.. Exactly how much fuel you could put where and in which model of plane could also change, The Spitfire wound up with ballast weights in the engine mounts so when the 2 pitch and constant speed props showed up the could take the weights out and still be somewhere near the correct CG.
Some Later Spitfires carried 72lbs of ballast in the tail to help balance the heavier two stage engines, despite larger radiator and intercooler behind the CG.

Tomo is quite right, there is limit to where you can put fuel and still have a safe, easy to fly airplane.
Depending on being able to burn off the correct amount of excess fuel before combat calls for careful planning and some cooperation from your enemies (not bouncing your formation early in the flight).

 

[MIflyer]

One of the curious things is why the British were so much worse at using drop tanks than were the Americans.

On the long range version of the Spitfire II they stuck an extra tank in the wing so that it stuck out like a mis-installed tip tank. It hurt performance while extending range and enabling operations over the French coast; they moved those few airplanes around to the units doing the long range work.

The ferry tanks used for Hurricanes, such as used for deployments to Malta, had built in pumps and then mostly were not used for operations. By mid-war the US mostly employed the exhaust from the vacuum pump to pressurize the tanks enough to push the fuel into the airplane's main tanks - until the jets in which dedicated bleed air regulators started doing the job, about 11-12 PSI. The early Wildcats such as the ones used on Guadalcanal, actually had manual fuel pumps that required the pilots to sit there and pump while they were flying to get the fuel out of the drop tanks.

I think that the US had been using external tanks for decades before WWII because our country is a lot larger than Western Europe. A typical early WWII German or British aircraft if it had been based at Kelly Field would not have been able to get out of Texas without running out of gas.

It was ironic that the British developed the paper drop tank that was used with such success on the P-51. Of course it had been in combat use for something like a year before Wright Field notified the USAAF units in Great Britain that it was not suitable.

By the way, I was surprised to read that the slipper type drop tanks used on the outboard wings of Mosquitoes were made out of wood. Seems to me that metal tanks would have been far superior as well as much easier to manufacture. I have a book that has some pictures of the tanks being made.

By the way, interesting little story about the rear tank in the P-51. A friend of mine had been involved with ferrying airplanes in WWII and got called in to go pick up a P-51D that was in Nashville or somewhere like that. Arriving there, the ferry pilot explained that he had been told to NEVER fly a P-51 with any fuel in the aft tank - and on the one he was ferrying the rear tank was empty but kept filling up with fuel! So he called in someone more qualified. It turned out that the Bendix Pressure Carb had a return that was routed to one of the main tanks, so that unused fuel went to a tank rather than being dumped overboard. Pilots on long missions were told to first burn off some of the fuel in the main tanks before switching to the aft tank and then the drop tanks so that the return from the carb had a place to go. But on the P-51D that ferry pilot was flying for some reason the return from the carb had been routed to the aft tank, which is why it kept filling up with fuel even when it started out empty.

 

[GregP]

Drop tankls are meant to be dropped. The last thing you want to do in a war where the enemy has limited resources is drop processed metal on his territory, particularly aircraft-grade aluminum (or duraluminum).

Wood tanks will be damaged when they hit the ground and paper tanks only last about one mission. Fighters are horrendously expensive to fly. Drop tank are way down on the list of expenses, but I'd bet they make up a sizeable chunk when you are dropping (and so losing) tanks from hundreds of fighters per day over the course of a month or a year. Still, compared with engines and normal wear items, they pale in cost.

If you look, there isn't much free room in a WWII fighter that is useable. Putting in extra fuel tanks is not simple. Particularly if you need the structure to withstand 8g+ when the tanks are full.

 

[Shortround6]

A big problem was fitting self sealing tanks. Post war racing mustangs (and some civil conversions?) converted the wings to integral fuel storage (seal areas of wing and filled them with fuel) that added hundreds of gallons to the capacity, BUT they were using areas the fighters used for guns and ammo and small spaces between structural components it would be impractical to fit separate fuel tanks into. It would also be nice if any extra fuel tank/s installed was in a space it could either be repaired easily or removed from in order to worked on outside the plane (or replaced to the get the plane back into service while the tank is being repaired)

 

[MIflyer]

I posted an article a while back on how Lockheed manufactured steel drop tanks, the big 160 and 300 gallon ones used on P-38's, P-47's, P-61's, PV-1's, and apparently P-82's.

Early F4F drop tanks were non-metallic, according to one of the USMC Guadalcanal pilots, who described them as being made of a "bean pod" material. I have no idea what that material could be. That may be why the pressurization system adopted later was not used; the tanks might not have been able to take even that low pressure.

The big drop tanks used on F4U's reportedly were non-metallic. Piper used one as a basis for the fuselage of its postwar Skycycle single seater.

The drop tanks used on some AVG P-40's appear to be non-metallic. I don't know what they were made of but it looks kinda like bamboo.

The flat drop tanks used on the belly of some ETO P-47's reportedly were steel. It appears those were custom made for the P-47 in order to provide ground clearance.

 

[Crimea_River]

By the way, I was surprised to read that the slipper type drop tanks used on the outboard wings of Mosquitoes were made out of wood. Seems to me that metal tanks would have been far superior as well as much easier to manufacture. I have a book that has some pictures of the tanks being made.

Not all were wood as at some point these were switched over to metal. The tanks on our B.35 were definitely not wood when we removed them.