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.