I don't understand how some planes ended up being so fast

[Zipper730]

Frequently lost in this discussion is that until 1943 many of those involved in the US bombing offensive were adamant that a long range escort fighter was either not needed or was impossible to make.

The idea of escort fighters was actually around for some time.

The problem that seems to have appeared with escort fighters had to do with the following

• They didn't think they were necessary: They saw them as inherently useful, but not a requirement for a successful bombing mission by in large (Billy Mitchell felt that they'd be essential, unless they could subdue the enemy Air Force on the ground).
• They were adamantly against external tanks: If they could not be jettisoned, they would be a source of drag after they served their purpose; if they were jettisonable, they would be punched off at the first sight of enemy fighters, and largely be a waste of perfectly good gasoline. So they wanted the plane to fly the range on internal fuel only, which required either a heavier plane, or a higher fuel-fraction.
• Advice of fighter pilots were not listened to: The bomber-guys had an agenda, and that often ran contrary to the fighter-pilots; they often were butting heads against each other, rather than working together for a common good. The fighter-guys had proposed both methods for shooting down bombers, as well as providing escorts, but they went unheeded.
  
• They wanted fighters with rear guns: Sounds insane, but the idea was kind of like using destroyers to protect a larger ship. It's not necessary because a bomber has defensive armament because they're not maneuverable enough to just fight it out on their own (and are more likely to be attacked from every single angle at once because of the grief they can cause). From a performance standpoint, it tends to either cut into fuel, or require a larger and heavier aircraft; from the issue of practical: Several fighters were built with such a configuration (the gunners were useless). If they listened to the fighter-tactic guys, they might very well have learned effective ways to cover bomber formations.
• There was a predilection with turbochargers: High altitude performance was favored for bombers, so the fighters had to have the ability too. The problem was that they seemed to focus very little on twin-stage superchargers (which provided less bulk), nor did they pay much attention to the idea of liquid-to-air intercoolers (they are more compact).
• They were largely unwilling to use a twin-engined fighter: It would overcome the issue with engine power...
• They were more expensive: They had to do all the things that fighters could do, except they also needed long range, and high-altitude capability (not to mention a rear-gunner). That costs more to develop, and to procure, and they were spending shitloads on bombers, so it had to wait.
• Some might have viewed such a design as impossible: The combination of small, fast, and agile, with long-range (and rear-gunners), and altitude would have been seen as quite a challenge.

Before the German declaration of war, USA probably can be excused for not embracing the escort fighter - after all they were trying to came out with inter-continetal bombers. After that, there were fast ways to create long range escort force for 1943, however the doctrine was again much slower than technology.

Often that's a problem -- the technology comes out faster than anybody can figure out what to do with it. This is actually more of a problem today than then...

Japanese were doing LR escort before the advent of Zero or Oscar.

Really?

So why is Rare Bear, a stubby radial engine F8F Bearcat the fastest piston engine aircraft in the world?

While the original Bearcat has a higher zero lift drag coefficient than a v12 fighter, it has a comparatively smaller wetted area. Radial engines package a lot of displacement in very little depth

You mean a lot of engine power in a small space?

they have less area forward of the quarter chord and can utilize shorter fuselage lengths for their frontal area.

But doesn't fineness area affect speed?

These short, squat fuselages have lower surface to volume ratios than long, sleek aircraft. So while their frontal area is larger and drag coefficient higher, their total drag area (Cd X Wetted Area) is still competitively low.

Somehow I'm drawing a blank...

Rare Bear mainly improved the design by increasing thrust. Oxygen mass flow rate was increase by using a higher displacement engine (R-3350 in lieu of R-2800), increasing engine speed (>3000rpm), increasing boost (many Reno racers reduce static compression to run higher boost) and using nitrous oxide.

Static compression? Do you mean like compression ratio?

Google seems to say power output is ~4500+hp. The propeller disc loading was decreased by using a large diameter propeller (3-point landings only) with a wider chord.

Tough to land

Voodoo holds the record now, with maybe 1000hp less.

What's Voodoo?

 

[drgondog]

"Zipper730, post: 1365230, member: 67843"]The idea of escort fighters was actually around for some time.

The problem that seems to have appeared with escort fighters had to do with the following

• They didn't think they were necessary: They saw them as inherently useful, but not a requirement for a successful bombing mission by in large (Billy Mitchell felt that they'd be essential, unless they could subdue the enemy Air Force on the ground).
• They were adamantly against external tanks: If they could not be jettisoned, they would be a source of drag after they served their purpose; if they were jettisonable, they would be punched off at the first sight of enemy fighters, and largely be a waste of perfectly good gasoline. So they wanted the plane to fly the range on internal fuel only, which required either a heavier plane, or a higher fuel-fraction.
• Advice of fighter pilots were not listened to: The bomber-guys had an agenda, and that often ran contrary to the fighter-pilots; they often were butting heads against each other, rather than working together for a common good. The fighter-guys had proposed both methods for shooting down bombers, as well as providing escorts, but they went unheeded.
  
• They wanted fighters with rear guns: Sounds insane, but the idea was kind of like using destroyers to protect a larger ship. It's not necessary because a bomber has defensive armament because they're not maneuverable enough to just fight it out on their own (and are more likely to be attacked from every single angle at once because of the grief they can cause). From a performance standpoint, it tends to either cut into fuel, or require a larger and heavier aircraft; from the issue of practical: Several fighters were built with such a configuration (the gunners were useless). If they listened to the fighter-tactic guys, they might very well have learned effective ways to cover bomber formations.
• There was a predilection with turbochargers: High altitude performance was favored for bombers, so the fighters had to have the ability too. The problem was that they seemed to focus very little on twin-stage superchargers (which provided less bulk), nor did they pay much attention to the idea of liquid-to-air intercoolers (they are more compact).
• They were largely unwilling to use a twin-engined fighter: It would overcome the issue with engine power...
• They were more expensive: They had to do all the things that fighters could do, except they also needed long range, and high-altitude capability (not to mention a rear-gunner). That costs more to develop, and to procure, and they were spending shitloads on bombers, so it had to wait.
• Some might have viewed such a design as impossible: The combination of small, fast, and agile, with long-range (and rear-gunners), and altitude would have been seen as quite a challenge.

Too simplistic. The 'future' AAF leaders were struggling to raise the role of armed aircraft from Pursuit to Attack role, and secure a place at the Joint Chief's table as an equal. Billy Mitchell (and Doughet) provided to inspiration in the mid-30's to position Bombers as Coastal Defense, which aroused animosity from the Naval mafia as well as traditional Army senior staff.

The B-17 changed everything with the combination of high altitude performance, payload and range - then shocked USN with the successful intercept of the Rex (Lemay navigator) 600 miles offshore. At that time, and through 1939-1940, there were really no interceptors save the P-38 capable of catching and attacking a B-17C at 30,000 feet.

Pursuit Aviation advocates who were perceived as 'nay sayers' to the Bomber Will Always Get Through, such as Chennault were moved aside or retired early - while Eaker, Spaatz, Arnold closed ranks and controlled allocation of aircraft technology funds.

Limited funds and evolving mission, combined with only one choice of in-line engine w/single stage supercharger and gas sucking,air cooled piston R2800 about to come on line. The specs generated after never really cited range as one of the most important attributes for successful bid, but speed was dominant. Bomber interception and attack aircraft were the focus.

Short sightedness regarding future combat ops let unprotected useful fuel capacity be designed into the P-38, P-39, & P-40. The RAF Purchasing commission intercepted the P-51 proposal and required 180 gallons in Protected fuel cells. The P-39 scaled from 200 to 120 gal, the P-38 from 400 to 300 gal, P-40 from 180 to 148/157 gal.

At no time during the spec process developed and released by Material Command, was a range capability to even closely approximate to the B-17.

Both Eaker and Spaatz were in UK during BoB and Blitz at different times, heard the skepticism from RAF regarding AAF strategic daylight mission planning - and Nobody on either side of the Atlantic foresaw the single or twin engine fighter with ability to escort our bombers at the Target. The P-61 proposal and contract was the first attempt at looking at long range fighter role with range potential equal or greater than P-38 with 646 gal internal fuel capacity - w/projected range 20% greater than P-47 and P-38, 60% greater than P-39 and P-40 - and the same as P-51 (Allison).

Eaker actually flew (and liked) the P-51 very much in 1942, but like all the rest of the AAF hierarchy, dismissed any thought of Escort fighter as the only engine on the horizon was the Allison and Merlin XX with poor performance at B-17 altitudes.

The drive for external tanks was officially noted as an outcome of Arnold's fighter Conference in Jan-Feb, 1942. Ferry tanks, unprotected, were verboten by AAF MC as being 'too hazardous'. Kelsey/Lockheed were first to take the initiative and mounted 160 ferry tank on P-38F/G to ferry to UK for 8th AF FC start up. But, neither that tank nor the 200 gal ferry tank for P-47 represented a rational approach to combat ops until summer/fall 1943 when Cass Hough at 8th Services Command and Pappy Gun 5th AF, modified P-47 and P-38 to bleed exhaust air to pressurize external fuel tanks - just as 8th AF experienced losses of Blitz Week, Tidal Wave, Schweinfurt-Regensburg.

The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.

The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison. So, rather than have a Brit/US Commission evaluating 'Best of Breed' technical developments, successful outcomes like Merlin Mustang arose from 'middle manager' advocates like Hitchcock - with connections to Winant and Roosevelt - to go around the bureaucracy.

Thank God for Barney Giles who effectively led AAF when Arnold was recovering from Heart attack on US side, and Tommy Hitchcock/Winant on UK side.

 

[tomo pauk]

...
The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison.
...

Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?

 

[wuzak]

Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?

Maybe it started when NAA rolled out the NA-73X without an engine because it hadn't yet arrived?

 

[drgondog]

Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?

Allison was doing a very poor job in two specific areas - 1.) delivery schedules, slowing down completion of Mustang I's to RAF, 2.) making significant changes to the delivered engines without communicating the changes to NAA, placing NAA in awkward position of having to modify airframe to properly install the engines.

NAA went so far as to get Mossie engine mount drawings and contact Packard to get necessary information in had for Kindleberger to meet with GM Board - allegedly it was quite a Board Meeting with GM, Allison and NAA CEO in same room. NAA was turned down, but apparently the meeting resulted in much better communication between Allison/NAA. That feud continued for years and IMO affected the fix to the Two Stage/Speed supercharged -119 replacement for Merlin after the XP-82/82B which never solved detonation issues at high MP

 

[pbehn]

An objection to external tanks only seems a bit strange with hind sight. It is a historical fact that the LW dropped back in the face of large daylight raids waiting for the escorts to turn back. However whoever was in charge of strategy must consider that their planes entering enemy air space would be met by fighters, if the LW could have met the escorts and made them drop their tanks, things could or would have been much different.

 

[tomo pauk]

..

The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.
...

Thanks for the feedback at post #105.

A few things about the quoted part. Nobody in the world in 1941 have had an non-turbo engine in production, let alone in service, that was making 1200+ HP at 25000 ft. Only UK and USA were making such engines in 1942, others did not.
However, there was prototype 2-stage R-2800 that fits the bill already in 1940. Unfortunately, USAAC was blind for that engine as a powerplant for 1-engined fighters.
There were enough of companies in the USA that could've designed a long range fighter around one turboed V-1710, or around one 2-stage supercharged R-2800 for the needs of the USAAAC/AAF before 1941. Yet they did not, and I'd bet that USAAC not wanting/specifying such a thing was much more of a hurdle than companies (in)ability.

 

[Zipper730]

"Zipper730, post: 1365230, member: 67843"]Too simplistic.

I was trying to bottom-line it...

The 'future' AAF leaders were struggling to raise the role of armed aircraft from Pursuit to Attack role, and secure a place at the Joint Chief's table as an equal.

I think you mean develop a strategic bombing capability, instead of the current pursuit & attack category, as part of a goal of an independent Air-Force like the RAF?

Billy Mitchell (and Doughet) provided to inspiration in the mid-30's to position Bombers as Coastal Defense, which aroused animosity from the Naval mafia as well as traditional Army senior staff.

Mitchell wanted to use bombers to hammer airfields, harbors, and cities predominantly: He focused on bombing ships because it seemed more acceptable to the public than what he really wanted (Many people subscribe to the notion that when the cause is just, the methods don't matter); the idea of using them for maritime patrol was simply an excuse to build a fleet of heavy bombers, though I think they started to believe their own narrative (the pit-fall of creating an echo-chamber where no opposing view is allowed), and the unerring accuracy of the Norden (which erred many times).

The B-17 changed everything with the combination of high altitude performance, payload and range

Actually, it started with the Martin B-10, which was able to outrun the fighters that were in service at the time (mostly due to having a monoplane, and retractible gear, though eventually the aircraft would have an enclosed canopy, turrets, NACA cowlings, and variable pitch props, etc.), a fighter with similar features would probably be able to outrun it.
As for the B-17, the prototype (Model 299) didn't actually have a turbocharger (that was added later), though it produced a critical altitude of around 25000 feet, and got the top speed over 300 miles an hour. It wasn't uncommon to see cruising altitudes around 32000 feet in some variants, though over Europe, altitudes were often around 22000 to 27000 feet it seemed.

At that time, and through 1939-1940, there were really no interceptors save the P-38 capable of catching and attacking a B-17C at 30,000 feet.

That sounds about right.

Pursuit Aviation advocates who were perceived as 'nay sayers' to the Bomber Will Always Get Through, such as Chennault were moved aside or retired early

Which basically is what I said about the bomber guys not listening to them: This wasn't something unique to the US, the RAF's Bomber Barons largely thought the same way until they suffered high losses over Germany (ironically at least some of it had to do with the altitude they were attacking at, owing to the change in target systems).

Regardless, it was clearly true: Provided a fighter had sufficient speed and high altitude capability, the bombers would be in major trouble. In the US, we did favor high altitude capability, but found it a crap-shoot in both fighters and bombers

• There was a B-10 fitted with a turbo: Increased speed to 236 mph. It was unreliable and dropped.
• The P-30 was based on the P-24 with aerodynamic refinement and a turbo: It worked after some work
• The P-37 was able to achieve 340 mph at 25000 feet but had an excessively long nose
• The B-17 worked
• The P-38 worked
• The P-39 didn't seem to have enough internal volume to pack in everything it was supposed to carry, and it's aerodynamics (propulsion wise) seemed to be a bit shoddy
• The B-24 worked

Eaker, Spaatz, Arnold closed ranks and controlled allocation of aircraft technology funds.

Which basically meant that bombers got priority...

Limited funds and evolving mission, combined with only one choice of in-line engine w/single stage supercharger and gas sucking,air cooled piston R2800 about to come on line.

The inline-engine issue had to do with the following

• Too Many Designs: They had numerous engine designs being drawn up, but basically had a limited demand for them after the great-depression, and the development of the NACA cowling. With limited resources, it is best to focus on the engines with the best potential, and pour the bulk of the resources into those (this problem is not entirely dissimilar from the Luftwaffe during WWII: They produced loads of designs, some of them brilliant, but few in numbers large enough to make a difference).
  
• Continental Engines: They were owned by the US Army, which basically drew up the designs for a hyper-engine that they wanted (O-1430, later I-1430); then told them to build it. It doesn't appear that they really listened much to the engine designers insights and knowledge, and fixated on the opposed-cylinder layout long after common sense showed that it was not needed.
• Conflict of Interest: The Lycoming O-1230 seemed actually to be a better design, but with the Army owning Continental, who's going to be picked?

As for the radials, there were was at least the R-2600 available since the mid/late 1930's.

The drive for external tanks was officially noted as an outcome of Arnold's fighter Conference in Jan-Feb, 1942. Ferry tanks, unprotected, were verboten by AAF MC as being 'too hazardous'.

Yet the RAF adopted drop-tanks of various sorts

Kelsey/Lockheed were first to take the initiative and mounted 160 ferry tank on P-38F/G to ferry to UK for 8th AF FC start up. But, neither that tank nor the 200 gal ferry tank for P-47 represented a rational approach to combat ops until summer/fall 1943 when Cass Hough at 8th Services Command and Pappy Gun 5th AF, modified P-47 and P-38 to bleed exhaust air to pressurize external fuel tanks - just as 8th AF experienced losses of Blitz Week, Tidal Wave, Schweinfurt-Regensburg.

Wait, the P-38's weren't pressurized at first? I know the P-47's weren't...

The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.

Yup...

The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison.

Firstly what engines would have been practical to license other than the Merlin, and what problems existed between Allison and NAA?[/quote][/quote]

 

[mad_max]

There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.

 

[pbehn]

There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.

That is a question of resources, you have to take account of the worst case scenario. To meet US escorts in equal numbers all around the airspace Germany had to defend results in fantasy numbers, but there are scenarios where the LW could have "got lucky" and inflicted devastating losses.

 

[Shortround6]

You also had the Americans using relays of fighter, one (or more) groups escorted the bombers in to a certain point, flying at over 300mph and doing "S" turns above the bombers in order to not get ahead of them. At some point a fresh group of fighters would show up having flown directly form their bases and thus having much more fuel still in the tanks. Perhaps this group is present over the target,perhaps it is relieved by a third group of fighters right before the target?
There will be other groups of fighters waiting to meet the bombers on their way out and escort them into save airspace. Forcing the 1st or 2nd group to drop tanks does NOT leave the bombers exposed for the majority of the mission.

External tanks had been used during the early 30s, but I have never read any reports on how they worked, either good or bad. Perhaps there were accidents that prejudiced the officers against them?

AS far as long range fighters vs bombers goes, A Vickers Wellington IC with Pegasus engines could go 28,500lbs at take-off which is a wing loading of 34lbs per sq ft at a time when the Spitfire was around 28.8lbs per sq ft (late MK V), a B-17 at 54,000lbs around 38lbs per sq ft.

Nobody expected bombers to fly like fighters (mostly) and they loaded them accordingly. lots of fuel to go with the bombs.
A late B-17 could hold 2780 gallons in the wings or around 10 times what a Mustang could hold including rear tank. An early B-17 could hold around 1700 gallons in the inner wing tanks, or about 10 times what a P-36 would hold including the Ferry tank. About 425 gallons per engine. Granted the B-17 has more drag but you are going to have cram a LOT of fuel into a P-36 to come close to the range of a B-17.
Heck , stick a 100 gallon drop tank under it and see how far you get? A B-17F running light (under 50,000lbs) could fly at about 200mph at around 10,000ft getting about 1 mile per gallon or about 1600miles on the inner wing tanks after using up 132 gallons in warm up, taxi and take-off The older ones might do a bit better, A P-36 was good for about 6.5 miles per gallon at the same speed/altitude under best conditions, soooo.... you need 246 gallons after warming up, taxing, take-off and climb to several thousand feet, I would add that even 15 minutes at 88% power will suck up 45 minutes worth of this low speed cruise or 150 miles of range.

SO you either limit the range of your bombers to that of a compromise fighter or you admit that the single engine escort fighter isn't viable until the Merlin 61 comes along. (or perhaps cramming a P-47 full of fuel).

The Navy 2 stage R-2800 isn't the answer for turbo charged B-17s. the power was only rated at about 1460hp at 23,500ft (including RAM) in the fall of 1941. Given the weight and drag (and thirst) of the R-2800 this isn't good enough to plan an escort fighter around. Production engines got a bit better and the production F4U-1 used a "B" series engine that gave 1650hp at 23,000ft with ram. Again, given the weight/drag and thirst of the R-2800 this isn't good enough.

I have said this before, a number of air staffs believed the only way to get performance and range was by using twin engined fighters.
Japanese Army built Ki-45s in addition to the Ki-43. Germans had the Bf 110.
The thinking behind the Ki-45 started in 1936, the requirement was issued to the manufacturers in March of 1937, many of these programs took years.

 

[Zipper730]

There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.

That has to do with logistics: Because they never planned to use escorts with drop-tanks, they never procured enough.

The 5th Air Force interestingly was manufacturing their own: And people say government can't do anything right...

External tanks had been used during the early 30s, but I have never read any reports on how they worked, either good or bad. Perhaps there were accidents that prejudiced the officers against them?

No idea...

I have said this before, a number of air staffs believed the only way to get performance and range was by using twin engined fighters.
Japanese Army built Ki-45s in addition to the Ki-43. Germans had the Bf 110.

It's a simpler way to do it. We also developed the YFM-1 Airacuda (It was predominantly a long range patrol interceptor, that could also double as a bomber escort) which despite its interesting looks was a turd with wings.

 

[drgondog]

There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.

You are dead right. The strategy was to force en masse drop with a bounce, but the leadership of 8th FC were already responding appropriately - namely sending a flight instead of a squadron when a few attacking fighters were encountered.

 

[tomo pauk]

...
SO you either limit the range of your bombers to that of a compromise fighter or you admit that the single engine escort fighter isn't viable until the Merlin 61 comes along. (or perhaps cramming a P-47 full of fuel).

The Navy 2 stage R-2800 isn't the answer for turbo charged B-17s. the power was only rated at about 1460hp at 23,500ft (including RAM) in the fall of 1941. Given the weight and drag (and thirst) of the R-2800 this isn't good enough to plan an escort fighter around. Production engines got a bit better and the production F4U-1 used a "B" series engine that gave 1650hp at 23,000ft with ram. Again, given the weight/drag and thirst of the R-2800 this isn't good enough.

In 1941, the BMW 801C was making ~1100 HP (~1120 PS) there, weighting 2325 lbs dry (+ armored oil coooler + oil).
The Navy's R-2800 was making the power you stated in the fall of 1940, not 1941. Weight 2495 lbs dry. Excellent engine to plan an escort fighter for tasks well above 20000 ft, it pushed big, heavy and thick-winged XF4U-1 at 380 mph at 23500 ft in 1940.
As for the Army's escort fighter around it - 350 gals of fuel + drop tanks, 300 sq ft wing of perhaps NACA 23015 profile at root. Engine is thirsty, but so are two V-1710s on a single airframe.

The P-47 with 350 gal of fuel also works, so does a fighter with 220-230 gals of fuel based around one turboed V-1710 from 1941 on.

 

[grampi]

What's Voodoo?

A highly modified P-51...

 

[Shortround6]

The P-47 with 350 gal of fuel also works, so does a fighter with 220-230 gals of fuel based around one turboed V-1710 from 1941 on.

for the last part

A Mustang it ain't
one source says 200 gallons internal.

 

[Zipper730]

Nobody expected bombers to fly like fighters (mostly) and they loaded them accordingly. lots of fuel to go with the bombs.

There's probably more to it than that.

When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.

When it comes to strength to weight: It favors the small. This is offset through creative design features, and lower g-load requirements (bombers); the same applies to power to weight ratio, which is also why you'll see a high power to weight ratio on a fighter, a smaller amount on a bomber.

A late B-17 could hold 2780 gallons in the wings or around 10 times what a Mustang could hold including rear tank.

True, but you're not factoring in fuel fraction. Fuel fraction is more important for performance than actual weight.

 

[pbehn]

There's probably more to it than that.

When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.

When it comes to strength to weight: It favors the small. This is offset through creative design features, and lower g-load requirements (bombers); the same applies to power to weight ratio, which is also why you'll see a high power to weight ratio on a fighter, a smaller amount on a bomber.
True, but you're not factoring in fuel fraction. Fuel fraction is more important for performance than actual weight.

Zipper, I love some of your posts, have you considered patenting the flying cube? I can see some issues in drag and lift but in terms of bomb load and fuel capacity it is a winner.

 

[Shortround6]

There's probably more to it than that.

When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.

When it comes to strength to weight: It favors the small. This is offset through creative design features, and lower g-load requirements (bombers); the same applies to power to weight ratio, which is also why you'll see a high power to weight ratio on a fighter, a smaller amount on a bomber.
True, but you're not factoring in fuel fraction. Fuel fraction is more important for performance than actual weight.

I really have no idea what you are talking about here.
I could be mistaken but Fuel fraction has very little to do performance except for range. For example take two hypothetical fighters, both 8,000lbs gross and both with 1500hp engines, Plane "A" holds 180 gallons (fuel fraction 13.5%?) and plane "B" holds 150 gallons (fuel fraction 11. 25%?). this tells us very little except that plane "A" might be expected to have longer range/endurance than plane "B". Assuming equal payloads (guns/ammo for a fighter) it may tell us that the designer of Plane "A" managed to design a lighter weight structure (or used lighter engine). It sure doesn't tell us anything about speed, climb or turn. Please note that Plane "B" might have used 180lbs of weight up in either heavier armament or in better protection on essentially the same weight airframe. but without knowing the payload fuel fraction really doesn't tell us much.

Please note that every plane built in the 1930s and early 40s had unused volume somewhere in the structure. The engines simply weren't powerful enough to allow all the "space" to be filled up. Unlike modern jets were even the vertical stabilizer is sometimes used for fuel storage the old planes were rather restricted as to where you could put things.

The B-17 started as the Boeing 299 in 1934 and the first one used P & W Hornet (R-1690) engines rated at 750hp at 7000ft and 850-875hp for take-off. Empty weight was 21,657 pounds max loaded was 38,053 pounds. While they changed the rear fuselage/tail the wing stayed the same shape and area. The last of the B-17Gs weighed 32,720 pounds empty and 72,000 pounds maximum although even 65,000lbs called for restricted take-offs and very restricted maneuvers when flying. Obviously they filled up some of the empty volume over the years but trying to fly 65,000lb bombers with 800 hp engine wasn't going to get very far. See XB-15 or Boeing model 294 for what it took for a long range bomber with small engines. The Boeing 299/B-17 was Boeing's 2nd shot at a 4 engine bomber.

I would note that while we are arguing about escort fighters the Boeing 299 prototype flew 2100 miles nonstop on it's Delivery flight from the Boeing factory to Wright Field, granted it was very likely it was aided by a tail wind but NOBODY had single engine fighters that could fly anywhere near 2000 miles no matter what you did to them in the summer of 1935.

I would note that sometimes size has a strength of it's own. As in a thick wing section is harder to bend than a thin wing section of the size (span and area) due to the upper surface having to be compressed more and the bottom surface having to be stretched more for the same amount of "bend".

 

[pbehn]

S/R I was thinking along the same lines this afternoon, looking at cut away drawings of the P-51 there isn't much unused space. I wonder what the engineers at FAA thought when told "hey that's a great plane, can you put another 300 gallons of fuel and oil in or on it and a couple of extra guns would be nice too"