Bomber escort logistics?

OT

All this talk of drop tanks has me thinking about the internals of the drop tank. Was there any kind kind of baffling inside the tank to stop the fuel from sloshing around?

Milosh said:

OT

All this talk of drop tanks has me thinking about the internals of the drop tank. Was there any kind kind of baffling inside the tank to stop the fuel from sloshing around?

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I don't recall that either the 75 or 160 gallon metal tanks had baffles. The 110 was made of reinforced impregnated paper made in UK and I just don't know.

The Hurricane's drop tanks had baffles. Unsure about other types.

i dont see where baffles would have come into play. not saying they did or didnt have them..just trying to rationalize this out. the only sloshing back and forth would occur on the ground taxiing or during take off and they were filled to capacity and wouldnt slosh then anyways. when flying you didnt do violent or quick maneuvers while they were attached...turns were shallow...etc. rough air after the drop tanks were partially emptied could give you a little shift but how much??

For interest here is an Australian report on the drop tank used on the A6M series up to the early A6M5 (probably from an A6M3):











What's interesting is how well constructed it was and the fact that the feed pipe was deemed to be to small to feed an engine developing full power.

Any droppable fuel tank in the 50-100 gal range is going to have some type of inner structure, that at a side benefit would also function as baffles.
You can't just have a thin metal skin, or any other material, fill it with 400 lbs and up of liquid, just put lugs on it and hang it under a wing. There has to be some kind of inner construction in that tank to transfer the load to the lugs.

Even the napalm tanks I assembled in the USAF had pretty substantial bulkheads internally, they would have functioned somewhat as baffles, though cured napalm has no need of baffles in the tank.

tyrodtom said:

Any droppable fuel tank in the 50-100 gal range is going to have some type of inner structure, that at a side benefit would also function as baffles.
You can't just have a thin metal skin, or any other material, fill it with 400 lbs and up of liquid, just put lugs on it and hang it under a wing. There has to be some kind of inner construction in that tank to transfer the load to the lugs.

Even the napalm tanks I assembled in the USAF had pretty substantial bulkheads internally, they would have functioned somewhat as baffles, though cured napalm has no need of baffles in the tank.

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Definitely; baffles of some description would be needed because there was never any guarantee that flight manouevres would be gentle enough to prevent the petrol slopping around in large quantities. Try filling (say) a five gallon container with 3 gallons of petrol, swing it gently from side to side until the petrol sets up a momentum of its own, then try holding the container steady while gripping the handle in one hand. Once unbaffled liquid starts moving it can be very hard to stop.

Greg has been pretty quiet since Shortround nailed him for umpteenth time on the difference between Range vs Combat Radius and my pointed remarks about the difference in fuel consumption for a Hellcat at 30000 feet and 340mph to escort ETO bombers vs 15000 feet and 205 mph True escorting SBD's.

Wonder if he has recovered yet. Wonder if he has decided to do some research and applied math. Wonder if he can do either and apply to the question he posed?

with the paper tanks... they broke down after awhile due to the fuel in them. any baffle would have to be a different material or you risk contaminating the fuel with the adhesive and construction material as it particalizes. those would, of course, be caught by the fuel filter but could/would probably clog it up. were the main tanks...wing and fuse baffled? i know they had a bladder of self-sealing rubberized material that acted to seal up holes...... but once fuel had been run down in those tanks and the bladder was smaller than the inside area of the tank...what kept it from it from rolling around inside that metal tank? and if they werent baffled...what would make it neccessary to baffle drop tanks?

my light sport ac has 2 wing tanks that arent baffled. its a really light ac and is more at the mercy of thermals and winds aloft than a heavy ww2 fighter so if that was going to affect flight i imagine they would have baffled them.

Lets not start looking for a fight.

Lets just leave it at this. The Hellcat was a great naval aircraft that did what it was supposed to do. Namely escort naval strike missions over the ocean. It was never intended to escort heavy bombers over heavily defended airspace.

The Hellcat would have been chopped up and spit out as an afterthought had it gone up against LW units.

Now, if we are talking about the Corsair doing heavy bomber escorts; well now that's something that's believable and quite possible.

I agree - although the fight had been in progress for some time. Enough is enough

How the Hellcat would have fared in combat is a different question.

The Corsair, unmodified has the same problem as the Hellcat. Insufficient "protected" internal fuel capacity for the escort mission.

It doesn't matter what drop tanks you can hang on it. What matters is the 237 gal internal tank. The wing tanks (57 gallons each) were protected "historically"' by a carbon dioxide purge system which kept them from catching fire (or greatly reduced the fire risk) but did nothing to stop them from leaking if hit by small caliber bullets/fragments. Fuel leaks out=plane doesn't get home.
Now, perhaps, smaller self sealing tanks could have been put in the same spaces to increase the internal fuel a substantial amount and get the radius for the Bomber escort mission up to a usable number. An extra 80-100 gallons depending on tank shape, thickness of self sealing, weight of tanks,etc?
It doesn't seem like that a big a deal, space is there, it is on or near the CG. The Plane is supposed to have a bit less drag than the F6F which helps.

The Corsair had a dramatic drop off in power at 25000 feet, although not much worse than the P-51D, but significantly more than the P-51B with critical altitude at 29000 feet.

The F4U like the F6F cruised best much lower altitudes than P-38, P-47 and P-51. Most of the reports I have just looked at for F4U-1 show max endurance at 179.5 mph at 5,500 feet with 237 gallons internal fuel. The F4U-1D however had 361 gallons of internal fuel so it was directly comparable to the P-47D-25 and later models.

The question between the F4U-1D is the difference between cruise fuel consumption when it moves 20,000 feet higher than optimum and boosts to at least 120mph more airspeed at that altitude. Both models I looked at had WI R-2800-8W two speed, two stage superchargers.

I conclude that with 111 more gallons of internal fuel and higher speed at same Rpm and boost that all versions of F4U were superior choice for ETO consideration. That is just with respect to range, much less survivability against the Fw 190 and Me 109 above 20,000 feet.

Could you check your sources?

In one manual it says that the F4D-1D did NOT have the wing tanks the earlier versions did but could carry TWO drop tanks instead of one.

Manual says wing tanks were 63 gallons each instead of the 57 gallons each in Deans "AHT" but that may be usable vs total or design vs actual? 12 gallons not enough to get exited about out of 350gals+.

Range chart in manual also makes NO allowance for warm-up, take-off, or climb to even 5,000ft.

SR - America's One Hundred Thousand was my 'quick' one stop reference. Page 507 with discussion of migration from 271 gal (wing only) in XF4U-1..

Then F4U-1, -1A, -1C went 273 fuselage only, plus two 62 gallon internal wing tanks for the 361 plus 175 centerline. It looks like the D dropped back to 237 internal (as you noted) plus two 150 gallon external. I misread the table on page 508

So, I stand corrected. Only the F4U-1, -1A and -1C could be tasked for same mission as P-47D-25 and still have enough internal fuel as the 370 gallons in the late model Jug. The F4U-1D would have less than either Hellcat internally.

On USN Range - I agree. Many Range estimates for different combat orgs assumed taxi, takeoff and climb to altitude then throttle back to maximum range throttle and rpm - but I have seen some that make no reference to 'how' the ship got to altitude and seemed to assume some mid air refueling.

ALL USAAF Combat Range profiles have warm up, taxi, take off, climb and throttle back plus 20 minutes combat power - but even those do not have an ETO style group assembly before climb..

drgondog said:

Then F4U-1, -1A, -1C went 273 fuselage only, plus two 62 gallon internal wing tanks for the 361 plus 175 centerline. It looks like the D dropped back to 237 internal (as you noted) plus two 150 gallon external. I misread the table on page 508

So, I stand corrected. Only the F4U-1, -1A and -1C could be tasked for same mission as P-47D-25 and still have enough internal fuel as the 370 gallons in the late model Jug .

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As "issued" the wing tanks were protected against fire by a CO2 dilution system to displace the flammable vapor in the tanks. The wing tanks were not protected against leakage. Had it been wanted I would guess the the wing tanks could have been replaced with self-sealing fuel tanks at some drop in capacity but still giving between the 305 and 370 gallons of the P-47s.
High speed cruise at 25,000ft and performance at 25,000 is still up for question.

US Navy tested the Fw-190A-4 vs Hellcat Corsair. At 25000 ft, the 190 was found to be faster 6 mph vs. F4U and 19 mph vs. F6F - the F6F really has nothing to offer with F4U around. The 190 was with 2 cannons and 2 LMGs aboard. Here.

Here is an encapsulation of the debate:

Postulate - F6F-3 could have performed the bomber escort role in the ETO during WWII as far as Berlin.

Given:
F6F-3 with R2800-10, 250 Gallons of fuel internally, two 150 gallon tanks externally is the proposed
Mixture of two US Bomber Types. B-17s with average altitude of 26,000 feet (TAS ~210 @ 150 mph IAS) or B-24s at 22,000 feet (TAS at 237 mph @ 180 IAS)
Assumptions:
1. Bomber course - East Anglia to Zwolle, Zwolle to Celle, Stendal and Berlin in straight line. Total = 580 miles.
2. Fighter R/V for final Target escort after Penetration Support turns for home. R/V just north of Hannover, west of Celle.
3. Fighter Route - East Anglia toward Amsterdam to Zwolle, (~270 miles), Zwolle to Hannover (~150 miles), Hannover to Berlin (~155 miles).
4. Combat Radius Profile
a.Warm up for 5 minutes
b. 1 minute take Off (MP) power - Combined warm up/take off equivalent to 5 minutes Rated Power ~ 25 minutes while all 48-52 ships form up into Group formation
c. Climb to 25,000 feet at 160 IAS and proceed along bomber course (there is a reason for this, except for some unique missions) at 210 IAS
d. At R/V climb to 30,000 feet and Ess over bombers at 210 IAS .
e. Escort to Berlin and back to same R/V point to hand off to Withdrawal Support
f. Cruise Home
g. Orbit for 30 minutes as rest of the Group lands.
h. Be Non Conservative - No Reserve - Land on fumes or display how much fuel you have left

Options
Cruise at any speed you choose but a.) must be able to R/V with bombers traveling at 210 mph at 26,000 feet from point halfway between East Anglia and Amsterdam all the way to Berlin, b.) Cruise above the bombers in central escort 4000 feet above them, c.) Cruise in Ess or straight line if you choose to drop your airspeed to bomber speed but be conscious of grave threat to your ability to protect against fighters entering at 390 mph+ TAS with altitude advantage. d.) Drop tanks for Combat at Combat Power (not WEP) for 20 minutes. e.) cruise home any way you can at any altitude and power settings you choose.
5. Reserve 30 minutes of fuel for circling airfield while the rest of the group lands.

Required:

1. Power settings, rpm, fuel rate of consumption, altitude and airspeed for each stage of the mission profile
2. Fuel remaining in external tanks (if any) at Berlin
3. Fuel usage from internal 250 gallon tank during taxi, TO and Formation assy
4. Internal fuel remaining over Berlin when entering Combat.

Argument(s) against the F6F-3 or -5 achieving suitable USAAF ETO Bomber escort to and from Berlin.
1. Altitude and ETO cruise requirements for the F6F vs P-47C, as one example, force the F6F from a Max Range profile of 12,000 feet at 200mph TAS to 30,000 feet and at least 300 mph TAS.
2. The Engine performance of the F6F is lower than the P-47C as far as Fuel consumption at equivalent speeds and altitudes and far less than either the P-38 or P-51. Additionally the profile drag of the F6F is 8+% higher than P-47 and 54% higher than the P-51
3. The internal fuel of the F6F is 18% less (55 gallons) than the 305 gallon P-47C internal tank
4. A twenty minute fight over Berlin reduces the internal reserve of fuel for the F6F from 250 to 160 for 20minute Combat Power engine settings - assuming zero internal fuel is used during take off and assembly process (not SOP in ETO)

If you choose any other parameter or profile to make your escort case, please explain your reasons.

Good summary DR, just the distance (for the fighters) is a little long. Typically they would fly out of closer airfields, eg Norwich to Berlin is only 508 miles.
Plus the bombers cruise speed was more like 180mph (for B-17s, B24s were a bit faster)

You are dead right about altitude being an important consideration, if your max economy is at a far lower height than needed for escorting then you either cruise at a non optimum height and use more fuel, or have to climb up after rendezvous cruise ... using more fuel. Plus you don't want to cross enemy territory too low as you are vulnerable to the medium AA as well as the high altitude stuff.

I just can't see how you can trick up an F-6 to do it. Maybe a Corsair with some work (and perhaps accepting CoG issues initially). Definitely a Spit (though Berlin would be the limit) and of course the later P-47s.
Those big radials really guzzled the gas.