Bomber escort logistics?

[wuzak]

The specs SAY it, the Hellcat CAN fly a 1,200 mile trip with adequate reserves if flown from a gound base, and I won't revisit this again. It absolutely CAN be done.

At Most Economic Cruise speed.

Which will:

• not allow you to catch the bombers unless you leave at the same time
• leave you at a disadvantage against the defenders
• and since you will be flying lower than the bombers you might want to look up near the target zone in case one of the bombs has your name on it!

 

[wuzak]

For instance (and just because it is the first data sheet I ran across) a Spitfire MK XIV has a top speed of 448mph at 26,000, an economical cruise of 245mph at 20,000ft and a maximum weak mixture cruise of 362mph at 20,000ft. Now the return might not be made at 362mph but flying at 245mph over Germany is like flying towing a big kick me sign.

If I were in a bomber needing escort, I would prefer that the brass is spending their time working out how to get a Spitfire XIV over target rather than a Hellcat!

And would RJ Mitchell have ever conceived that his Spitfire would, in but a few years, be able to cruise faster than it was originally able to do in all-out level flight?

 

[GregP]

Hi Wuzak, I came back because YOU were here only.

I specifically say that if Hellcats were the only option, it could be done. I would NOT choose the Hellcat for the mission but, if it were the only option, it absolutely COULD be done.

The Hellcat COULD takeoff with 600 US gallons of fuel if required, and that bis WAY more than required. Combat and return can be debated a small bit but, if the Hellcat were the only option, it could have been done easily, agreement from any of you or not. I've spoken with WWII Hellcat pilots who flew 1,5000 miiles WITH guns loaded, and THEY weren't part of this discussion and had no axe to grind.

Sorry for all you nay-sayers, but it IS possible for a Hellcat. I have not and WILL not figure it for a P-47/ This discussion is much too ridiculous for me to want to continue.

Hell, they loaded the P-51 beyond aft CG and flew it that way for a few YEARS. You think they would not have done so to the F6F ?

Get real.

 

[wuzak]

If Hellcats were the only option they may have been able to make it work. Not sure it would have been much better than no escort (or more properly, no escort over the target area, but escort part of the way there).

 

[OldSkeptic]

Agree Greg, if it was absolutely necessary they would have done it ...though the losses would have been terrible.

Wuzak is correct, better to trick up the MK VIII (or IX) or even XIV Spit first, or bring on the DH Hornet sooner if for some reason the Mustang is not available.
The superiority in performance (plus the lower fuel consumption, hence the extra fuel load required is less) make it a better platform for that sort of mission.

You are dead correct to bring up the CoG issue (an issue the anti=-Spit crowd bang on and on about all the time), but that applied to lots of aircraft in wartime. For example Mossie (and possibly PR ones) bombers were often starting off with poor CoG, which of course improved as they burned off fuel.

If you are in non-contested airspace to burn off enough fuel to stabilise the aircraft it is not (with good training of course) such an issue as some people think.
It is hard work as the aircraft can 'hunt' all the time and you must be very careful in turns (or pulling out of dives) so you won't do excessive G, as it wants to tighten up.

But training helps a lot, plus things like bob weights and the like.

Plus take off and climb to 20,000 ft on a Spit LF IX took alone (at full LR weight) about 24 gals, a Mustang IV about 30 UK ones). Who knows what a P-47 was*, 50% more at least (maybe double?).
So you were starting to get back to normal well before you got into enemy territory.

Form what I read the Mustang got much better after half the rear tank was ran down, the Spit once you got down to about 20 gals (a third of a 66 gal tank) in the Merlin 60 series with the elevator horn balance fixes (and the XIV was probably a little bit better due to the greater weight in the front). So the Mustang was better (and had more fuel anyway in the main tanks), but fully fueled up it was severely out of CoG balance on take off.

Added: Found it, P-47 normal climb with drop tanks a whipping 70 UK gals.... ouch. 84 gals with the belly tank as well... double ouch.

 

[tomo pauk]

Anyone contemplated how good/bad would be the the Spit VIII, when fitted with 29 imp gal rear tank, as per Spitfire V used for deployment in the Med? Almost 180 US gals total - what would be realistic combat radius? Either 90 or 170 imp gal slipper tank attached, or maybe 126 imp gal tank from P-38s?

 

[drgondog]

Greg - you keep flailing because a.) you don't know how to get the data, and b.) you don't know how to calculate a mission profile when you have the data.

Now - the P-47C-1 had EXACTLY the same R-2800-10 engine (Incorrect thanks to Wuzak - it was a -21 with single speed/single stage and supercharger but the sfc was still close - in favor of the P-47 at altitudes above 25,000 feet), as the F6F with very close sfc. Redo my analysis using your assumptions for fuel to mile consumption based on climb to 26,000 (non conservative), fast cruise to R/V, slow down to escort at 300+ mph, combat at MP for 20 minutes, return at same cruise as escort. 15 minutes of fuel left as reserve at your airfield (bonus - the P-47C-1 Combat radius of 170 miles with no external tanks - or additional drag - was with only15 minutes reserve)

Remember the R2800-10 at MP burns 280-300 gph at MP at 25000 feet so the Very best case is that you drain 100 gallons of internal fuel and have no drop tanks over 600 miles from home. You have 150 gallons left minus whatever you used for warm up, taxi and formation assembly minus 15 minutes at auto lean ~ 115gph or say 30 gallons.

Net - show what ya got for the R2800-10 to go 600 miles on 120 gallons of fuel.

BTW - collar your WWII Hellcat vet and have him tell you what mission he flew, or heard of, to escort ANY aircraft flying 150IAS/210TAS at 25000 feet for some 600 miles out and 600 miles back with a fight over the target. Report back with That story and maybe supply a name and contact - or invite him to join us and put me in my place?

 

[drgondog]

Anyone contemplated how good/bad would be the the Spit VIII, when fitted with 29 imp gal rear tank, as per Spitfire V used for deployment in the Med? Almost 180 US gals total - what would be realistic combat radius? Either 90 or 170 imp gal slipper tank attached, or maybe 126 imp gal tank from P-38s?

Tomo - somewhere back in time we did one of these with the 170 imp gal tank with assumptions that the extra drag would require a cruise setting higher than Max Range setting - IIRC offhand it could get 600+ with no combat.

 

[Shortround6]

I specifically say that if Hellcats were the only option, it could be done. I would NOT choose the Hellcat for the mission but, if it were the only option, it absolutely COULD be done.

Not with the escort mission profiles as done historically.

which leaves us with........

Have the bombers fly at lower altitudes so the F6F can fly top cover. Of course this puts then into more flak. but hey, lets think outside the box.

Use scads more F6Fs so some F6Fs are escorting other F6Fs which won't drop their tanks until later.

The Hellcat COULD takeoff with 600 US gallons of fuel if required, and that bis WAY more than required. Combat and return can be debated a small bit but, if the Hellcat were the only option, it could have been done easily, agreement from any of you or not.

You don't seem to grasp the idea that that the amount of fuel you take off with is irrelevant, it is the amount you have after you drop the tanks that counts, otherwise your escorts are flying one way, semi suicide missions. outside the box but hardly effective in the long run. Lets look at the P-47 because we have figures for it.

305 gallons = 125 mile radius
370 gallons = 225 mile radius
605 gallons = 425 mile radius ( two 150 gallon drop tanks)
670 gallons = 600 mile radius ( two 150 gallon drop tanks)

Please note that an extra 235 gallons of fuel extends the radius 200 miles with the smaller internal tank ( or 300 gallons got an extra 300 miles) while the extra 65 gallons internal extended the radius 100 miles with no drop tanks and is good for 175 miles with the drop tanks.

Also please note that a P-47 could fly 830 miles on 250 US gallons after warm up, take off and climb to 5,000ft at economical cruise.
USAAC planners were trying to figure out how to get the pilots and planes back to use on future missions.

I have spoken with WWII Hellcat pilots who flew 1,5000 miiles WITH guns loaded, and THEY weren't part of this discussion and had no axe to grind.

Great, now ask them if they flew that distance at 20-25,000ft doing 210mph IAS or 300 mph true.

Sorry for all you nay-sayers, but it IS possible for a Hellcat

.

Somehow it is only possible on your "say so". you have offered NO proof that is was possible at the speeds and altitudes needed for the ETO escort mission.
No disrespect to the veterans that flew the F6F but if you don't ask the right question you will not get the right answer.
Sorry Greg, without "Pixie dust" or anti-gravity paint it is NOT possible.

This discussion is much too ridiculous for me to want to continue.

Something we agree on, you bring NO facts to the table. No charts, NO tables, No flight plans, NO historic missions flown at the altitudes and speeds needed.

Hell, they loaded the P-51 beyond aft CG and flew it that way for a few YEARS. You think they would not have done so to the F6F ?

well, finally a somewhat valid suggestion. Lets just ADD 120 gallons behind the CG to get the the return profile close to the P-47s ( and ignore that the P-51s seldom, if ever, fought with the rear tank more than about 25-33% full).
Now what does an extra 720lbs of fuel + weight of the self sealing tank) do to the performance of the Hellcat at 20-25,000ft?

Get real

If the shoe fits..........

 

[Shortround6]

Now - the P-47C-1 had EXACTLY the same R-2800-10 engine as the F6F with very close sfc.

I beleive there is a difference and not in Hellcats favor.

The engine in the P-47 can supply 1200hp at 2250rpm/32in at 25,000ft burning 105 US gallons an hour and/or
1100hp at 2150rpm/31" at 25,000ft burning 95 US gallons an hour

The engine in the F6F needs to turning 2250rpm at 35" to deliver just under 1100hp to the prop at 25,000ft in high gear and about the same in low blower, 25,000ft being sort of a crossover point at this level of power. But slightly more rpm and more MAP for the same power to the prop can hardly be the same spc can it?

Add to that the engine chart for the F4U (P&W R-2800-8 differed from the -10 in the F6F in the type of carburetor used)

Gives max cruise ratings of 970hp at 2150rpm/34" at 20500ft and 93 US gallons an hour low blower and 930-950hp( chart is a bit fuzzy) at 2050rpm/34" at 26000ft in high blower at 82 gallons an hour.

With my math it seems the navy engines and the P-47 engine are either very close or a the Navy engines are a few percent behind.

 

[drgondog]

Agree Greg, if it was absolutely necessary they would have done it ...though the losses would have been terrible.

So far - lots of arm waving but no facts. The F6F-3 had the same engine as the P-47 but not turbo supercharged nor perform as well above 25000 feet, nearly the same weight and I presented the calculated Combat ranges for 25000 and 30000 feet. The P-47C calcs used only 15 minutes of reserve for landing whereas the USN had an hour IIRC and the P-47C-1 used a 20 minute combat at MP only (no WEP) and had 305 gallons internal to the F6F 250. Combat Radius 160 to 170 miles. F6F-3 will be no better on 305 gallons internal fuel and far worse on 250 gallons. Discount external fuel because on remaining internal fuel will get you home once you engage in a fight - unless you are a very stupid fighter pilot choosing to fight slow and sluggish against a 109 over Berlin.

The R2800-10 uses about 90-100 gallons in 20 minutes of MP. That takes the P-47C-1 down to 205 gallons to take off, assemble, fly to target and back with 30 gallons reserve. Using the same rule for the similar weight, same engine R2800-10 equipped F6F-3 the comparative fuel for the F6F is 250 minus 90-100 down to 150 gallons including the reserve of 30 gallons.

So, the P-47C can only fly out and return 170 miles at 335mph with 205 gallons. OK so double the 170 to 340 for straight line to get the distance the P-47C-1 can fly from Berlin towards London with 205 gallons with no reserve, down to 175 gallons so that he can fool around looking for place to land. But the Hellcat flying the same profile with the same engine and same airspeed/altitude requirements will only have 150 gallons vs the 205 and must also have 30 gallons left so its down to 175 gallons to go 600 miles. At 115 gallons per hour consumption (at auto lean 2400rpm/36" Hg) that works out to flight time remaining of 1.5 hours ------> to go 600 miles and have 30 gallons in reserve... or 1.5x335 = 502 miles.

This run out is non conservative as it assume that zero fuel is used for warm up, taxi, take off and assembly - which is contrary to SOP

Wuzak is correct, better to trick up the MK VIII (or IX) or even XIV Spit first, or bring on the DH Hornet sooner if for some reason the Mustang is not available.
The superiority in performance (plus the lower fuel consumption, hence the extra fuel load required is less) make it a better platform for that sort of mission.

IMO the Mk VIII with 170 imp gallon slipper could make Berlin and back with reserve for combat and landing

.



But training helps a lot, plus things like bob weights and the like.

Plus take off and climb to 20,000 ft on a Spit LF IX took alone (at full LR weight) about 24 gals, a Mustang IV about 30 UK ones). Who knows what a P-47 was*, 50% more at least (maybe double?).

I just put out the narrative for the P-47 and assumptions for 8th AF SOP and calculated 130 gallons to start engines, taxi, take off, assemble and climb. Your scenario and times above are for a single a/c that is not assembling into a 52 Mustang/P--47 Group before climbing out.


Added: Found it, P-47 normal climb with drop tanks a whipping 70 UK gals.... ouch. 84 gals with the belly tank as well... double ouch.

Add another 30 minutes at 115gph+ to assemble a 52 ship formation and you will get to 126 gallons - I calculated 129+ above.

 

[drgondog]

I beleive there is a difference and not in Hellcats favor.

The engine in the P-47 can supply 1200hp at 2250rpm/32in at 25,000ft burning 105 US gallons an hour and/or
1100hp at 2150rpm/31" at 25,000ft burning 95 US gallons an hour

SR - I agree your numbers. I used 2400/36" at 115 to get to the 325+mph TAS cruise.

The engine in the F6F needs to turning 2250rpm at 35" to deliver just under 1100hp to the prop at 25,000ft in high gear and about the same in low blower, 25,000ft being sort of a crossover point at this level of power. But slightly more rpm and more MAP for the same power to the prop can hardly be the same spc can it?

No, but my calcs also tended to give the F6F even more benefit of the doubt because escort altitudes were dominantly 4000-6000 feet above the bombers which for B-17s averaged 26000 feet. The F6F goes downhill fast above 25000 feet

Add to that the engine chart for the F4U (P&W R-2800-8 differed from the -10 in the F6F in the type of carburetor used)

Gives max cruise ratings of 970hp at 2150rpm/34" at 20500ft and 93 US gallons an hour low blower and 930-950hp( chart is a bit fuzzy) at 2050rpm/34" at 26000ft in high blower at 82 gallons an hour.

With my math it seems the navy engines and the P-47 engine are either very close or a the Navy engines are a few percent behind.

The differences are miniscule. The hidden factor for these discussions is the question "What is the most economical rpm/boost setting to maintain 325-340 mph TAS at 26000 to 30000 feet?"

That is how I got to 2400/36" and 115 gph.

 

[wuzak]

Now - the P-47C-1 had EXACTLY the same R-2800-10 engine as the F6F with very close sfc.

From Graham White, R-2800, Pratt Whitney's Dependable Masterpiece the P-47C-1 was fitted with the R-2800-21. This was, of course, a single stage, sigle speed engine, whose altitude performance was due to the turbocharger.

The F6F used the R-2800-10, which was a 2 stage 3 speed (low, high and neutral) supercharged engine.

Since the F6F's engine required a higher pressure a ratio from its mechanically driven supercharger at altitude than the P-47's did it would have worse fuel consumption, I would think. So that would make the comparison worse for the F6F.

 

[drgondog]

Hi Drgondog,

I already did. It's in the posts.

Great - why don't you get your cut and paste skills dusted off and bring your thesis to this discussion?

You seem to forget that Naval ranges are VERY conservative. The carrier moves around, often without the knowledge of the WWII aviator. So the Navy has a requirement for a LOT of reserve fuel. The fighter must fly the misson, come back, look around for 30 - 45 minutes and then spend 15 - 45 or more minutes in the pattern to land while the other guys recover.

I don't believe I have forgotten that Greg. Had I been so careless I would have been helped out via the USN docs which state 1 hour reserve.

It is trite to say, but land bases don't move around much and the reserves are therefore much less.

Trite? Silly? Pedantic? Moronic? Take your pic on why you state the obvious.

The specs SAY it, the Hellcat CAN fly a 1,200 mile trip with adequate reserves if flown from a gound base, and I won't revisit this again. It absolutely CAN be done.

Greg - out of confusion or ignorance you keep wandering back to the 'easy' thing - which is a single fighter, flying a one way trip, low and slow and not finding anybody to fight. The ETO/Hellcat discussion requires YOU to 'Think out of the Box' and ask 'what is different'? Your tables have provision to take off, assemble a squadron of 12 to 16, climb to 15,000 feet, fly at a leisurely pace of 200mph to a point and descend, and land. Your USN Combat Radius tables are fine for slow moving low altitude cruise to target, fight for 20 minutes and return on the deck.

With those tables a.) you get shot down on the way, b.) the Hellcats never catch the ETO bombers and c.) your only usefulness is slow and low fighter sweeps.

Your analysis is very flawed ... ask any Hellcat pilot. I have.

My analysis is sound - I don't have to ask a Hellcat pilot. You have no analysis and you can't find one in USN records to perform an ETO escort to Berlin on a rational basis... the way those nasty old generals would insist on.

Go find your analysis - that you claim to have posted - so that we may bask in the light of your brilliance. I know you must have uncovered the 'thing' that neither SR or I have failed to discern..

 

[drgondog]

From Graham White, R-2800, Pratt Whitney's Dependable Masterpiece the P-47C-1 was fitted with the R-2800-21. This was, of course, a single stage, sigle speed engine, whose altitude performance was due to the turbocharger.

The F6F used the R-2800-10, which was a 2 stage 3 speed (low, high and neutral) supercharged engine.

Since the F6F's engine required a higher pressure a ratio from its mechanically driven supercharger at altitude than the P-47's did it would have worse fuel consumption, I would think. So that would make the comparison worse for the F6F.

Wuzak - you are correct. I misread my own notes. All the P-47B and C models tested at Eglin had the R-2800-21.

 

[OldSkeptic]

Anyone contemplated how good/bad would be the the Spit VIII, when fitted with 29 imp gal rear tank, as per Spitfire V used for deployment in the Med? Almost 180 US gals total - what would be realistic combat radius? Either 90 or 170 imp gal slipper tank attached, or maybe 126 imp gal tank from P-38s?

Plugging the numbers into my spreadsheet and using a 90 gal drop tank) you get about 450miles radius. That includes
(1) Allowance for take off an climb to 20,000ft (using rear tank).
(2) Cruise to target (MEC) at 20,000ft (using drop tank).
(3) 15 mins Combat (internal fuel)
(4) Return (internal Fuel)
(5) Reserve of 22 gals (enough for 151 miles at MEC or another 10 mins at combat).

Obviously higher altitudes, etc will reduce that, say for a 25,000ft mission then 400 miles.

No need for a larger drop tank, what matters is what is left in (non CoG affecting) internal fuel after getting there and combat (15 mins = 35 gals) which on a Mk VIII is 87 gals.

You want to improve the combat radius then you need more internal fuel that does not affect performance, say some more in the wings (take out the 0.303s) or 10 gals left in the rear tank (probably acceptable with a bob weight). Even the option, used in some PR versions, of an under the seat tank (10-20 gals perhaps).

You take off, climb and cruise to target (or escort rendezvous) on the rear tank and the drop tank. Hold the drop tank until combat (SOP), then fight and return on what is left.



Edited to add: For the sheer heck of It I set up the Mustang with the same formulas (based on the aircraft data sheet) and it is interesting.

Now, for comparison I set up a 500 mile combat radius for a LR Spit MK VIII vs P-51D. Same assumptions.

For return the Spit has 87 gals and the Mustang 114 (UK of course) only 27 gals diff.

But, the Spit has only 101 miles (at MEC) as reserve, while the Mustang has 343 miles up its sleeve.

The reason is the lower drag (despite its higher cruise speed gives a lower fuel consumption.

On the way out the consumption is about the same in total, the Spit uses less in the climb but more on the cruise there. The Spit uses a bit less for combat.
But on the way back (and in a clean configuration) the Mustang has about 7% lower fuel consumption. Over 500 miles return that adds up to a much larger reserve left (or a longer return range).

Even on the same internal and external fuel load (though how you'd fit it into and on the Spit ...) the Mustang has a longer range.
When you take into account it's actual larger internal then on a realistic basis (and same assumptions) the Mustang has a larger reserve left for a 700 mile radius mission than a LR Spit VIII at 500 miles. Plus that faster MEC cruise speed for the Mustang doesn't hurt either (253 mph vs 220).

As for forming up, etc on the way there, in neither case is than an issue affecting max range, since it is done on the rear tanks and the drop tank.
For the Spit, even for a 500 mile mission with a 90 gal drop tank, only 37 gals from the drop tank is used on the cruise, leaving plenty for forming up, etc and (of course) the actual escort phase where you will be zig zagging, etc (eg you might rendezvous at the 300 mile point and escort for 200 miles).

The Mustang is naturally even better with it's larger drop tanks and lower consumption.

 

[drgondog]

OldSkeptic - if your mission is escort there is the factor for formation assembly for both Mustang and Spitfire.

The Spit and Mustang III frequently had 12 ship assignments whereas the US Mustang had 48 aircraft in a Fighter Group mission (plus spares0.

That would add at least 10 minutes for the Spit and 30+ minutes for P-51B/D at combination Rated and military power.

You also should reserve 25+ gallons in the rear tank unless the mission is relatively short like to Brunswick or Mulhausen.

 

[OldSkeptic]

OldSkeptic - if your mission is escort there is the factor for formation assembly for both Mustang and Spitfire.

The Spit and Mustang III frequently had 12 ship assignments whereas the US Mustang had 48 aircraft in a Fighter Group mission (plus spares0.

That would add at least 10 minutes for the Spit and 30+ minutes for P-51B/D at combination Rated and military power.

All done on rear and drop tank. Even in a 700 mile mission the Mustang has 61 (UK) gals free in its drop tanks for that sort of thing (after takeoff, climb and cruise).
There are 196 gals in its rear and drop tanks, more than enough for takeoff, climb, forming up, cruise, zig zagging, etc, before you hit the internal wing tanks for combat and return.

 

[drgondog]

Not arguing your point about fuel to say, Berlin. But going to Posnan or Stettin or Piryatin, Ukraine sets different operating procedures for both uses of aft fuselage fuel and cruise settings. My only point is that for your spread sheet that you start using internal fuel on assembly and climb and check when it is near 30 gallons - then switch to External fuel.

The experienced guys had to be constantly aware of the use of the externals to try to balance the usage as much as possible.

I know my father kept 50 gallons in his aft tank for the last shuttle mission, confident in his ability to fly the Mustang on the ragged edge of stability - just to make sure he had enough fuel. His directive to the shooters were to hit 'em but don't chase 'em if they broke for the deck in order to reduce the combat allowance.

He touched down after 8 hrs with 35 gallons left primarily because of confusion with Bomb Wings who reported being late, then 30 minutes later ahead of schedule so the group had to speed up the cruise to get to R/V point Nw of Warsaw.

 

[OldSkeptic]

Oh yes, that's why I call the Mustang a VLR fighter. And agree about leaving some rear tank fuel. 20-30 gals for a Mustang was quite possible and done for those very long range missions.

My spreadsheet can take account of that, for a 700 mile mission (eg) of you run the rear totally down at the beginning you have only 19 gals (or 143 miles at MEC) in reserve, not a lot.
But if you leave 20 gals in the rear tank then you have 39 gals (291 miles) which is a lot more comfortable. Even doing that you still don't use all the drop tank fuel in pure cruise, with 41 gals up your sleeve for formatting, zig zagging, etc.