Why were U.S. pursuit fighters at the start of WW2 of lower performance than European fighters?

[marathag]

A great deal of thought goes into preliminary design - interactive as various fixed and consumable stores are positioned and re-positioned. The most important is the fuel and the fuel fraction as the designers/performance guys play with tankage - usually the most important consumable and most potential impact on static margins and cg travel for stability.

I would assume that the Hawker designers elected to go with their decision after exploring many options to improve hazard management for the amount of fuel required to meet the spec. Very few designers of Pursuit aircraft elected to put fuel in wings as wingtankage tended to force more weight into wing, make difficult decisions fat wing/thing wing for drag considerations, increase structural related weight, etc

But 28 Imp. gallon is still pretty small to move about, not like gaining the huge 237 US gallon fuselage tank that the USN wanted Wing guns, XF4U lost the four wing fuel tanks, with the cowl guns removed, plus the Cockpit moved over 3 feet aft, to keep the big fuel load near the CoG

Just trying to make the Hurricane more Mustang like, though with a far smaller tank behind the seat.

 

[Shortround6]

Hurricane started at just under 5700lbs and in 1939 with no protection and a two pitch prop went about 6400lbs.

XP-51 went just over 7900lbs with an Allison engine.
P-51B with Merlin gained over 300lbs of engine weight and over 100lbs of propeller weight plus everything else.

 

[GrauGeist]

But 28 Imp. gallon is still pretty small to move about

28 Imperial gallons (or 33 U.S. gallons) will weigh close to 202 pounds.

Add the dry weight of the fuel tank plus fasteners, etc. and you have much more than "pretty small".

Also take into consideration, that the further it's moved from the CoG, the greater influence it will have on the aircraft.

 

[marathag]

28 Imperial gallons (or 33 U.S. gallons) will weigh close to 202 pounds.

Add the dry weight of the fuel tank plus fasteners, etc. and you have much more than "pretty small".

Also take into consideration, that the further it's moved from the CoG, the greater influence it will have on the aircraft.

Agreed, as I brought up earlier. Dynamic CoG would shift more, but far less load changed than experienced with P-40 Warhawk and P-51 Mustang that had larger tanks behind the seat.

Worth it for Pilots not getting burned up, I think

 

[GrauGeist]

Agreed, as I brought up earlier. Dynamic CoG would shift more, but far less load changed than experienced with P-40 Warhawk and P-51 Mustang that had larger tanks behind the seat.

Worth it for Pilots not getting burned up, I think

To get an idea of where the CoG is in regards to either the Hurri or Mustang, compare a profile drawing from both aircraft side-by-side and use the afore mentioned balance point situated roughly at the front of the cockpit.

The Hurricane is clearly at a disadvantage versus the P-51, as the Mustang's CoG is further back.

*if* you remove the firewall fuel tank and place it behind the cockpit, you need to remove a comparable amount of weight from the opposing point and place it where the fuel tank was.
However, as the Hurri's fuel tank was situated at the CoG axis, it's variable fuel level weights were negligible on it's performance BUT now, being behind the cockpit, will now didctate performance whereas the former mass in that location was static.

 

[Reluctant Poster]

Duplicate

 

[Reluctant Poster]

Agreed, as I brought up earlier. Dynamic CoG would shift more, but far less load changed than experienced with P-40 Warhawk and P-51 Mustang that had larger tanks behind the seat.

Worth it for Pilots not getting burned up, I think

Different attitudes back then. Pilots died a lot more frequently. In general life wasn't as precious as it is 80 years later. Look at motor racing in the 50 s and 60s and add up the number of drivers burned to death. Siffert, Bandini, Courage, Williamson, Bonnier. That's only F1 and off the top of my head.
The first car magazine I remember seeing was a Motor Sport with coverage of the 1965 Mexican Grand Prix. Out of the 17 drivers that started that race 9 would die in racing accidents.

 

[Reluctant Poster]

View attachment 716178from a model kit
View attachment 716179
Looks to me like there was room to move forward some, but would leave some space above the legs, as you point out.

But why the desire to put a gravity fed fuel tank there, and not the oil tank/glycol tank or cowl guns, as other nations did with that area?

Why not move the cockpit forward some, and relocate the oil tank from by the wing to ahead of the instrument panel, and have the reserve tank just behind the seat, with the radio gear ontop?

What this would look like, is similar to the P-51 layout
View attachment 716180

The goal is to keep fuel from a punctured fuel tank from streaming into the cockpit by the windstream.

Yeah, hot Oil and/or hot glycol would not be an enjoyable bath either, but worlds better than the 'Blow torch intensity flame'

At 600 yards, too far away to register, Page opened fire on one of the leading machines, then abruptly stopped short. One moment there had been clear sky between himself and thirty Dorniers. Now the air was criss-crossed with a fusillade of glinting white tracer-cannon shells converging on the Hurricanes. He saw Gracie's machine peel from the attack; the distance between Page and the leading bombers was only thirty yards now. Strikes from his machine-gun fire flashed in winking daggers of light from a Dornier's port engine; it was suddenly a desperate race to destroy before he himself was destroyed.
As a thunderclap explosion tore at his eardrums, Page's first reaction was: I can't have been hit. It could happen to other people, but not me. Then all at once fear surged again as an ugly ragged hole gaped in his starboard wing. And then the petrol tank behind the engine, sited on a level with his chest, blew up like a bomb; flames seared through the cockpit like a prairie fire, clawing greedily towards the draught from the open hood. A voice Page barely recognized was screaming in mortal terror: Dear God, save me — save me, dear God.'

Desperately he grappled with the Sutton harness, head reared back from the licking flames, seeing with horror the bare skin of his hands on the control column shrivelling like burnt parchment in the blast furnace of heat. Struggling, he screamed and screamed again. Somehow — he would never know how — he extricated himself from the cockpit, and began falling like a stone, powerless to stop.
Richard Collier Eagle Day - The Battle of Britain Hodder & Stoughton 1966

If you compare it to it predecessor the Fury they moved the pilot forward to take advantage of the space formerly occupied by the cowl guns.

 

[z42]

Looks to me like there was room to move forward some, but would leave some space above the legs, as you point out.

But why the desire to put a gravity fed fuel tank there, and not the oil tank/glycol tank or cowl guns, as other nations did with that area?

Why not move the cockpit forward some, and relocate the oil tank from by the wing to ahead of the instrument panel, and have the reserve tank just behind the seat, with the radio gear ontop?

What this would look like, is similar to the P-51 layout

The goal is to keep fuel from a punctured fuel tank from streaming into the cockpit by the windstream.

Yeah, hot Oil and/or hot glycol would not be an enjoyable bath either, but worlds better than the 'Blow torch intensity flame'

If you compare it to it predecessor the Fury they moved the pilot forward to take advantage of the space formerly occupied by the cowl guns.

From those pictures, maybe there is a little bit (~20cm?) the pilot could be moved forward before his feet hit the firewall. And have to leave a bit of room for working those rudder pedals as well. Remove the petrol tank ahead of the instrument panel, put the oil tank there instead. Put small fuel tanks in the wing leading edges, where the oil tank was? And then an L-shaped fuel tank below/behind the pilot, similar to the Bf 109. There is still height left in the fuselage, although the wing box is below the cockpit, so I'm not sure how feasible it is to put fuel tanks there; you'd need multiple small bladders probably? Then you probably need to move the radiator a bit aft to make space for the fuel tank, which might mean the entire wing moves backwards as well to compensate for the CG shift. Starting to look suspiciously like a 1935 Mustang, yes.

 

[Reluctant Poster]

From those pictures, maybe there is a little bit (~20cm?) the pilot could be moved forward before his feet hit the firewall. And have to leave a bit of room for working those rudder pedals as well. Remove the petrol tank ahead of the instrument panel, put the oil tank there instead. Put small fuel tanks in the wing leading edges, where the oil tank was? And then an L-shaped fuel tank below/behind the pilot, similar to the Bf 109. There is still height left in the fuselage, although the wing box is below the cockpit, so I'm not sure how feasible it is to put fuel tanks there; you'd need multiple small bladders probably? Then you probably need to move the radiator a bit aft to make space for the fuel tank, which might mean the entire wing moves backwards as well to compensate for the CG shift. Starting to look suspiciously like a 1935 Mustang, yes.

You're missing stressed skin construction and a laminar flow wing. The reality is that the Hurricane was based very much on prior art. The Spitfire was more of a leap into the future. Never forget that Mitchell had more experience in high speed flight than just about any aircraft designer of that era. Also never forget that the Spitfire took longer to get into production.

 

[z42]

You're missing stressed skin construction and a laminar flow wing. The reality is that the Hurricane was based very much on prior art. The Spitfire was more of a leap into the future. Never forget that Mitchell had more experience in high speed flight than just about any aircraft designer of that era. Also never forget that the Spitfire took longer to get into production.

I wrote that it's starting to look like a Mustang, with the radiator (and slightly, the wing) moved backwards, not that it would be the same as the Mustang.