Wasn't the P-51 the best escort fighter of the war?

[tomo pauk]

I am a little confused by this range chart. Why does it seem like the fuel burn rate is greater with the 108 gallon belly tank than with two 150 gallon wing tanks? The average fuel efficiency round trip with 413 gallons of fuel is 1.45 mpg, while with 605 gallons it is 1.65 mpg. Wouldn't the two larger wing tanks cause more aerodynamic drag than the single belly tank and thereby decrease fuel efficiency, or am I missing something here?

From what I can gather, with small total fuel capacity, the increased percentage of that fuel was used on high power/high consumption engine settings (take-off, climb, combat), while cruising part was not that long - thus total flight mileage was not that good.
With total fuel capacity greatly increased, a small percentage of fuel was used on high power engine settings, and much greater percentage of fuel was used on cruising - the total flight mileage improved.
Note that required combat time was 5+15min for both cases (108 gal or 300 gal of external fuel), and fuel reserve was the same (30 min). The difference in consumption per hour in hi-power and cruising settings was approx 2:1 up to 4:1.

 

[Admiral Beez]

Wasn't the Zero an escort fighter? For the time a very good one.

Admiral Yamamoto disagrees. Of course, sixteen P-38 vs. six A6M2 is hardly fair odds, but the Japanese shot down only one P-38 and didn't loose a single fighter themselves, whilst loosing both charges. It's akin to an ambush on POTUS, where the man dies, but the Secret Service force shoots at nothing and survives the day without serious injury, while the attackers get away with a single loss.

Did the Zero ever successfully escort anything? It certainly has the range and can compete with anything that's coming after the Zeros' charges, but AIUI they usually had no radio and low ammunition capacity.

It's not the aircraft's fault, but the IJN pilots seems to tactically operate alone rather than in coordination. For example, at the Battle of Midway, Hiryū's first attack wave on USS Yorktown consisted of 18 D3As and six fighter escorts, but enroute two of the Zeros broke off to chase some of Enterprise's returning (and thus, of no threat) SBDs, leaving the 18 D3As with only four escorts, and seeing thirteen of the bombers shot down (in fairness, some by AA).

 

[DarrenW]

From what I can gather, with small total fuel capacity, the increased percentage of that fuel was used on high power/high consumption engine settings (take-off, climb, combat), while cruising part was not that long - thus total flight mileage was not that good.
With total fuel capacity greatly increased, a small percentage of fuel was used on high power engine settings, and much greater percentage of fuel was used on cruising - the total flight mileage improved.
Note that required combat time was 5+15min for both cases (108 gal or 300 gal of external fuel), and fuel reserve was the same (30 min). The difference in consumption per hour in hi-power and cruising settings was approx 2:1 up to 4:1.

That does make sense. So basically a higher percentage of the total fuel load would be utilized during periods of better fuel economy. Got it!

 

[BiffF15]

I am a little confused by this range chart. Why does it seem like the fuel burn rate is greater with the 108 gallon belly tank than with two 150 gallon wing tanks? The average fuel efficiency round trip with 413 gallons of fuel is 1.45 mpg, while with 605 gallons it is 1.65 mpg. Wouldn't the two larger wing tanks cause more aerodynamic drag than the single belly tank and thereby decrease fuel efficiency, or am I missing something here?

View attachment 585011

Darren,

The Eagle is the same, IE a higher burn with one centerline vice two wing tanks. It's due on the Eagle to how far the wing tanks are from the wing versus how close the centerline bag is. Parasite drag is greater on the centerline and assume it's the same on the P-47. Or it's the pancake centerline has more drag than the teardrop wings, or a little of both.

Cheers,
Biff

 

[pbehn]

Darren,

The Eagle is the same, IE a higher burn with one centerline vice two wing tanks. It's due on the Eagle to how far the wing tanks are from the wing versus how close the centerline bag is. Parasite drag is greater on the centerline and assume it's the same on the P-47. Or it's the pancake centerline has more drag than the teardrop wings, or a little of both.

Cheers,
Biff

The ins and outs of this hurt my head and make my eyes bleed, as a pilot how much information do you have to know/use about maximising range?

 

[BiffF15]

The ins and outs of this hurt my head and make my eyes bleed, as a pilot how much information do you have to know/use about maximising range?

pbehn,

With the military equipment there is a ton of info, especially since varied external stores inflicts large swings in your drag. And with A/C that carry air to ground weapons there will be a tremendous amount of different configurations to contend with.

A simple example would be a pond (ocean crossing). Usually done in flights of six with each tanker (very simple example) in which fuel is calculated for numbers 1, 3 and 5. The wingmen, 2, 4, and 6 are considered to have the same gas as their flight leads. In reality they use more and refuel last so the flight plan has times and fuel required to start refueling for each "pair". If someone can't get gas for whatever reason they have usually a very small window in which to get it sorted then off you go as a pair to divert (have done this). The divert fuel will get you to an alternate with enough fuel to shoot several approaches if required. In peace time your flight plan will always have viable diverts. Wartime this can be waived situation dependent.

On a pond crossing the tanker launches first, followed 5-10 minutes later by the first 6 ship. We like to rejoin with the tanker above 10k as he will be at a higher speed and easier for us to form on. Additionally a spare 2 ship will launch with the lead 6 and follow them for quite awhile. The tanker will then cycle all of us across the boom, including the spares, to insure system functionality. The spares then tag along for about 45-60 minutes in case someone develops a mechanical and diverts.

After cycling the 6 across for a top off (in addition to the ops check), the tanker will usually refuel from another tanker met along the way. The end result is the lead tanker and all six chicks are topped off prior to entering the tracks (routes across the ocean also used by airliners). The two spares will then check in with each tanker / 6 ship as they RTB to see if there has been fallout. A no answer and onward they go to check in with last group then homeward bound. The two spares are usually very experienced guys / gals so they can fit in anywhere (flight lead, wingman or chase ship).

In fights you learn your fuel flows for 360's (how much gas per) at high, medium and low altitude. You also will know how to execute a minimum fuel recovery by heart and will accomplish at least one for real sometime in your early Fighter career (everyone scares themselves at least once early on).

In the airline world in the days of paper charts / books we would look up our weights / altitude and figure out max range or endurance. Now with the Flight Management Computers (FMCs) they do it for you. Also the airlines further break down fuel / engine wear / time into a cost index, that gets loaded into the FMC. The lower the number the lower the power setting, and slower speed you climb at. The higher the CI the higher the power and speed used in the climb (the latter cuts time but increases the burn).

Probably more than you wanted to know.

Cheers,
Biff

 

[pbehn]

pbehn,


Probably more than you wanted to know.

Cheers,
Biff

Not at all, thanks.

 

[DarrenW]

Darren,

The Eagle is the same, IE a higher burn with one centerline vice two wing tanks. It's due on the Eagle to how far the wing tanks are from the wing versus how close the centerline bag is. Parasite drag is greater on the centerline and assume it's the same on the P-47. Or it's the pancake centerline has more drag than the teardrop wings, or a little of both.

Cheers,
Biff

Thanks Biff, I never really realized that but it's a very good thing to remember.

 

[pinsog]

Admiral Yamamoto disagrees. Of course, sixteen P-38 vs. six A6M2 is hardly fair odds, but the Japanese shot down only one P-38 and didn't loose a single fighter themselves, whilst loosing both charges. It's akin to an ambush on POTUS, where the man dies, but the Secret Service force shoots at nothing and survives the day without serious injury, while the attackers get away with a single loss.

Did the Zero ever successfully escort anything? It certainly has the range and can compete with anything that's coming after the Zeros' charges, but AIUI they usually had no radio and low ammunition capacity.

It's not the aircraft's fault, but the IJN pilots seems to tactically operate alone rather than in coordination. For example, at the Battle of Midway, Hiryū's first attack wave on USS Yorktown consisted of 18 D3As and six fighter escorts, but enroute two of the Zeros broke off to chase some of Enterprise's returning (and thus, of no threat) SBDs, leaving the 18 D3As with only four escorts, and seeing thirteen of the bombers shot down (in fairness, some by AA).

Zero's did pretty good escorting bombers to Australia keeping defending Spitfires at a 1 to 1 ratio for Zeros and bombers combined. In fact I would love to see stats on Zeros escorting bombers over Darwin vs 109's escorting bombers in the battle of Britain. They did fine against the fighters defending Midway. They also held off Wildcats well enough for Kates to put 2 torpedoes into Yorktown later in the day while heavily outnumbered. Zeros did ok until the P38 and Hellcat arrived.

 

[Tkdog]

None of which involved a highly coordinated attack on their charges.

 

[drgondog]

And they developed tested and fitted 85G auxiliary 75G drop tanks to the P51 to escort it, in about 18 months.

Not sure of your timeline. The first production Mustang fitted with bomb/external fuel tanks was the A-36 which first flew in October 1942. The first experimental 90 gal SS tank in P-51B-1-NA flew in mid-July 1943. I haven't nailed down the date of the first 85gal fuselage tank kit installation 'first flight' but believe it was early January 1944. The first squadron level deployment by 354FG with all equipped with the kits was early February 1944. Production article 85 gal fuse tanks in P-51B-10-NA and C-5-NT were operational in late March.

 

[drgondog]

The Spitfire IX was supposed to have 175 miles of combat radius when covering US bombers.

Tomo - can you point me to the source? Without external tanks or 85 gal Fuselage tank, the P-51B-1 with 180+gal had a 'combat radius' of approx 160 mi. Same engine, cleaner airframe. Was the RAF definition of combat radius different (less) with respect to AAF combat contingencies of 5 min WEP and 15 min MP? The P-47C and D with only internal fuel was good for approx 125 mi CR.

That said, what external tankage would permit 175mi CR?

 

[tomo pauk]

Tomo - can you point me to the source? Without external tanks or 85 gal Fuselage tank, the P-51B-1 with 180+gal had a 'combat radius' of approx 160 mi. Same engine, cleaner airframe. Was the RAF definition of combat radius different (less) with respect to AAF combat contingencies of 5 min WEP and 15 min MP? The P-47C and D with only internal fuel was good for approx 125 mi CR.

That said, what external tankage would permit 175mi CR?

The 175 mile radius is stated in these two maps: picture, picture2. Unfortunately, it does not state the fuel tankage.
This map shows 200 mile radius; again, the fuel tankage of the Spitfire is not stated.

My take is that 90 imp gal (110 US gal) tank was the only addition for the 84 gal internal fuel tankage for the Spitfire for such calculations. Equals obviously to 174 imp gals, vs. 150 imp gals for the P-51B without fuselage tank and without drop tanks.

The P-47C and early D was supposed to get 175 miles of radius without drop tanks per these maps, as well as per this one. Expanded to 230 miles as US airmen gotten more experienced??

 

[drgondog]

The 175 mile radius is stated in these two maps: picture, picture2. Unfortunately, it does not state the fuel tankage.
This map shows 200 mile radius; again, the fuel tankage of the Spitfire is not stated.

My take is that 90 imp gal (110 US gal) tank was the only addition for the 84 gal internal fuel tankage for the Spitfire for such calculations. Equals obviously to 174 imp gals, vs. 150 imp gals for the P-51B without fuselage tank and without drop tanks.

The P-47C and early D was supposed to get 175 miles of radius without drop tanks per these maps, as well as per this one. Expanded to 230 miles as US airmen gotten more experienced??

Tomo - In my new book, I devoted several pages, tables and charts to explain Combat Radius per USAAF definitions and cross checked their assumptions based on flight testing results. Unfortunately, every map similar to the links you provided were a combination of undefined sourcing as well as errors in timeframe. Mike Williams has the most accurate baseline Test Flight docs for P-47C and P-51D. Dean AOHT has the best collection of the AAF combat radius tables used for ETO operations and was the foundation for cross checking my tables and map overlays.

As an example, look to the P-47C flight tests for the 125mi estimated combat radius (early) with 305 gallons (dec 1942).

The P-47D (pre-25) with full internal fuel of 305Gal, didn't approach 175 until the 205gal (100 usable) Ferry tank experiment. the streamlined 75 gal combat tank took it to 200-230

 

[Snautzer01]

Gotta get that book.

 

[Howard Gibson]

Well, let's hear it.

You don't get hit with 37mm flack while flying escort. That looks like ground attack.

 

[tomo pauk]

Tomo - In my new book, I devoted several pages, tables and charts to explain Combat Radius per USAAF definitions and cross checked their assumptions based on flight testing results. Unfortunately, every map similar to the links you provided were a combination of undefined sourcing as well as errors in timeframe. Mike Williams has the most accurate baseline Test Flight docs for P-47C and P-51D. Dean AOHT has the best collection of the AAF combat radius tables used for ETO operations and was the foundation for cross checking my tables and map overlays.

As an example, look to the P-47C flight tests for the 125mi estimated combat radius (early) with 305 gallons (dec 1942).

The P-47D (pre-25) with full internal fuel of 305Gal, didn't approach 175 until the 205gal (100 usable) Ferry tank experiment. the streamlined 75 gal combat tank took it to 200-230

Dean notes that escort radius was being extended to 340 miles in August 1943 (pg. 288) - usage of 75 gal tank perhaps? On same page, the 'theoretical escort radius' was extended to 375 miles if the 108 gals belly tank is used on September 1943.
On pg. 287, he notes that the expedient of filling the ferry tank half-full (ie. ~100 gals) enabled the P-47s to meet the enemy at distance of 260 miles.
I'm not sure how long the combat time at these ranges was.

P-47C data here. Supposed to do 170 mile radius with 20 min combat on military power at 25000 ft, with 305 gals of fuel.

 

[pbehn]

Tomo - In my new book, I devoted several pages, tables and charts to explain Combat Radius per USAAF definitions and cross checked their assumptions based on flight testing results. Unfortunately, every map similar to the links you provided were a combination of undefined sourcing as well as errors in timeframe. Mike Williams has the most accurate baseline Test Flight docs for P-47C and P-51D. Dean AOHT has the best collection of the AAF combat radius tables used for ETO operations and was the foundation for cross checking my tables and map overlays.

As an example, look to the P-47C flight tests for the 125mi estimated combat radius (early) with 305 gallons (dec 1942).

The P-47D (pre-25) with full internal fuel of 305Gal, didn't approach 175 until the 205gal (100 usable) Ferry tank experiment. the streamlined 75 gal combat tank took it to 200-230

I just had a thought, that radius is obviously from a single point, but is pretty similar in its "reach" to what the Typhoon's radius of action was in the period, and Spitfire Mk IXs did escort Typhoons. Maybe a cross over of two different mission profiles. Typhoons and their escorts didnt all set off from a point in Cambridgeshire, they used airfields closer to the target which would push that radius out.

 

[33k in the air]

For what it's worth, fighter escort ranges from the publication Eighth Air Force Tactical Development, August 1942 – May 1945 (p97):

Note that while the graphic shows the Feb. 1944 range of 475 miles being achieved with two 108-gallon tanks, the text says it was done with two 150-gallon tanks. I think the text number is a typo — it doesn't make sense to go from 425 miles with 150 gallons of extra fuel to only 475 miles with 300 extra gallons, or twice the external fuel load. But it does make sense to go from 425 miles with 150 extra gallons to 475 miles with 216 extra gallons.

ETA: The P-38 range is shown with 75- and 108-gallon drop tanks. But this publication, as well as Freeman's Mighty Eighth War Manual, state that only the 165-gallon drop tank was used by the P-38 on operations.

 

[33k in the air]

From the publication A History of the VIII USAAF Fighter Command (Plate XII):

"Target support means the use of the airplane for a period of about 15 minutes or more over the target, only. Penetration support means their use as long-range escort, directly with the bombers, along some assigned part of the course."