F8F Bearcat Questions

stona · Apr 22, 2016

I have the take off weight somewhere. I do not know the configuration but I bet it was clean.

Edit: I don't have the weight for that flight.
Tare for the Mk 24 was 7,351 lbs.
Take off with all internal fuel, including rear tanks, which seems unlikely for the test, no external stores was 9,900lb.
Take the weight of 66 gallons for the upper and lower rear fuel tanks away, and maybe 36 gallons for the various wing tanks, and you'll be in the ball park. Call the weight of that petrol 750lb (at 7.3lb/imp.gallon) and you are left with 9,150 lbs which is very close to the known take off weight of the Spiteful in testing.
The Mk 24 was still climbing at 4,100 ft/min at 17,000ft.
Cheers
Steve

drgondog · Apr 23, 2016

Sounds reasonable Steve - the challenge in relating flight test performance is a getting concise facts about the parameters of take off condition. In nearly all Flight tests after 1942, the US SOP was 'external racks' because the mission normally included the escort role and non-combat ferry tanks and racks were coming into play in mid 1943, then standard escort role in 1944 and 1945 - both AAF and USN.

My experience in examining RAF/RAE flight testing was that external racks were exceptions, not the rule, whereas AAF/USN racks were the rule not the exception .

That said, for given Power available the ROC calculation is very sensitive to Gross Weight changes and additional drag items and relative angle of attack in climb as incremental CL is attained,

Is there a reference that clearly outlines "Basic Weight' and precisely what that means fro RAF?

US custom is the weight of the airframe absent mission specific items such as ammo, oil, , pyrotechnics, fuel, external racks - but does not includes mission specific load out - Pilot, oil, fuel, racks, ammo, rockets, bombs/external fuel tanks to get to Gross weight specifics.

stona · Apr 23, 2016

drgondog said:
Sounds reasonable Steve - the challenge in relating flight test performance is a getting concise facts about the parameters of take off condition. In nearly all Flight tests after 1942, the US SOP was 'external racks' because the mission normally included the escort role and non-combat ferry tanks and racks were coming into play in mid 1943, then standard escort role in 1944 and 1945 - both AAF and USN.

My experience in examining RAF/RAE flight testing was that external racks were exceptions, not the rule, whereas AAF/USN racks were the rule not the exception .

That said, for given Power available the ROC calculation is very sensitive to Gross Weight changes and additional drag items and relative angle of attack in climb as incremental CL is attained,

Is there a reference that clearly outlines "Basic Weight' and precisely what that means fro RAF?

US custom is the weight of the airframe absent mission specific items such as ammo, oil, , pyrotechnics, fuel, external racks - but does not includes mission specific load out - Pilot, oil, fuel, racks, ammo, rockets, bombs/external fuel tanks to get to Gross weight specifics.

I don't think the British included racks for these test flights, and obviously not external ordnance or other stores.
The British tare weight is effectively the empty weight of the aircraft. Then there is a whole series of other weights given which start with all the basics like internal fuel, oil, and pilot ammunition and increase from there.
For the Spitfire Mark 24 the tare weight was 7,351 pounds. The take off weight, which I think includes a full internal fuel load, ammunition etc was 10,102 pounds. The maximum permissible weight was 10,150 pounds but this is a bit of a misnomer because, finally, there is the maximum overload weight of 12,150 pounds.
It is this last figure that includes rockets, bombs, 'overload tank' (90 gallons)and finally the big 170 gallon ferry tank in various combinations giving weights from 9,900 pounds up to 11,930 pounds. It is all very confusing and difficult to tell what exact configuration was used in any one series of tests!

Cheers

Steve

Mother Fokker · Apr 24, 2016

I once saw the Bearcat and the Tigercat together at an airshow, unbelieveable sight and sound.
Personally I prefer the Tigercat though, with that extremely thin fuselage.
Beautiful plane.

grampi · Apr 26, 2016

drgondog said:
Steve - the apple to apple comparison depends on full internal loads for both, as well as presence of external racks. The same era SAC dated 1949 for the P-51H with full internal fuel (255 gal) and racks was 410kt/472mph 5000fpm-SL, 2850fpm- 25K but 412kt/474mph 5840fpm SL, 3450fpm-25K with 60 gal.

Don't these figures mean the P-51H is the most awesome plane?

GregP · Apr 26, 2016

A military stock Bearcat set a 1946 climb record of standstill to 10,000 feet in 94 seconds. No doubt it wasn't hauling a full internal load. I'll think about the P-51H as a better climber when it beats that record at any load.

Personally, I like both airplanes a lot, but the Bearcat is my personal favorite piston fighter. No doubt the P-51H was faster at best altitude. Not too sure it is faster down low, but maybe. Drgondog probably knows. At this late date, I suppose it doesn't much matter since we'll likely never see either one set too many more records and, if they do, it is also very likely neither airframe will be even close to military stock configuration ... they may not even have the same engine type as was delivered in the aircraft when new.

grampi · Apr 27, 2016

GregP said:
A military stock Bearcat set a 1946 climb record of standstill to 10,000 feet in 94 seconds. No doubt it wasn't hauling a full internal load. I'll think about the P-51H as a better climber when it beats that record at any load.

Personally, I like both airplanes a lot, but the Bearcat is my personal favorite piston fighter. No doubt the P-51H was faster at best altitude. Not too sure it is faster down low, but maybe. Drgondog probably knows. At this late date, I suppose it doesn't much matter since we'll likely never see either one set too many more records and, if they do, it is also very likely neither airframe will be even close to military stock configuration ... they may not even have the same engine type as was delivered in the aircraft when new.

grampi · Apr 27, 2016

GregP said:
A military stock Bearcat set a 1946 climb record of standstill to 10,000 feet in 94 seconds. No doubt it wasn't hauling a full internal load. I'll think about the P-51H as a better climber when it beats that record at any load.

Personally, I like both airplanes a lot, but the Bearcat is my personal favorite piston fighter. No doubt the P-51H was faster at best altitude. Not too sure it is faster down low, but maybe. Drgondog probably knows. At this late date, I suppose it doesn't much matter since we'll likely never see either one set too many more records and, if they do, it is also very likely neither airframe will be even close to military stock configuration ... they may not even have the same engine type as was delivered in the aircraft when new.

The Bearcat is an impressive climber up to a certain altitude, and then there are others that are better. The P-51H was better, as well as some of the later model Spits at higher alititudes. The Cat may have been the best to 10K or 15K feet, but after that, all bets are off...

Shortround6 · Apr 27, 2016

Once again you have to be specific when referring to the Bearcat. An F8F-1 had as much as 2750hp at sea level combat rating but that dropped to 2450hp at 9,600ft and by 16,000ft the supercharger may have been only capable of supplying enough air for 1700hp.

With the change of engine on the F8F-2 the engine was capable of 1800hp at 23,250ft in combat rating and 1600hp at 22,000ft military.

Both planes held only 16 gallons of water for the water injection system so the combat rating was of limited duration.

The engine in the -2 was an "E" series R-2800 that used very few parts common to even the "C" series engines and a new supercharger using a variable hydraulic coupling like the DB engines instead of a two speed drive.

the -2 gained around 700lbs in weight in large part by going to 20mm cannon.

drgondog · Apr 27, 2016

The MP of the F8F was similar to F6F and F4U and exceeded that of the 1650-9 at MP and will always out climb the P-51H to the 15000 foot range and will do so at WEP/WI. After that altitude the P-51H will always have an advantage with respective combat load outs being equal. The wild card would be for the P-51H to carry full load of ammo but

When using 90"/WI the P-51H has a huge advantage in Power Available vs Power Required, lower drag and same approximate Gross Weight. An example is straight away speeds at SL where the P-51H is doing 409mph on WEP to the F8F-2 386mph. and 470mph at 22,500 to 450+mph for the F8F-2 .

The rated time for a P-51H to climb to 10,000 feet is 2,3 minutes and 6.7 to 25,000 feet. GW= 9485 which is full internal load of ammo and fuel (255 gal), w/wing racks - BUT - that is at full WEP and Combat GW with a lot more fuel than the Bearcat. . .

GregP · Apr 27, 2016

drgondog said:
The MP of the F8F was similar to F6F and F4U and exceeded that of the 1650-9 at MP and will always out climb the P-51H to the 15000 foot range and will do so at WEP/WI. After that altitude the P-51H will always have an advantage with respective combat load outs being equal. The wild card would be for the P-51H to carry full load of ammo but

When using 90"/WI the P-51H has a huge advantage in Power Available vs Power Required, lower drag and same approximate Gross Weight. An example is straight away speeds at SL where the P-51H is doing 409mph on WEP to the F8F-2 386mph. and 470mph at 22,500 to 450+mph for the F8F-2 .

The rated time for a P-51H to climb to 10,000 feet is 2,3 minutes and 6.7 to 25,000 feet. GW= 9485 which is full internal load of ammo and fuel (255 gal), w/wing racks - BUT - that is at full WEP and Combat GW with a lot more fuel than the Bearcat. . .

I thought anything except maybe a British fighter had more fuel than a Bearcat.

Let me think ... Spitfire, E.E. Lightning, Folland Gnat, they were all surely short-legged birds. I'm not sure a Gnat will make it around the pattern without external tanks, at least the one that flies locally (and is still in Red Arrows paint) can't go very far without tanks.

drgondog · Apr 28, 2016

That is true Greg. The F8F is second only to F4F for lowest Navy fighter fuel load but both the P-40 and P-39 carried less fuel.

The key point regarding P-51H versus F8F is to truly compare as much apples to apples with respect to the selected Combat Weights as well as engine performance.

Notably when comparing the P-51H to Bearcat, by today's standards, nobody is a.) running at Combat/WEP, b.) 150 Octane Fuel, c.) Water injection - all of which were used to squeeze more performance out of the Merlin 1650-9 Engine in comparison to P&W R2800-30W.

But - given the P-51H in interceptor mode, namely full ammo but only 180 gallons of fuel, and using the fully configured 1945-1946 set up when 150 octane fuel was still available, the 1650-9 at 90"/WI put out almost as much HP as the R2800-30WI at SL then more HP after 15,000 feet until FTH in the 22,000-23000 foot range.

At SL and FTH the 51H had about 20+mph speed advantage and the P-51H climbed better at both altitudes. With full 260 gallons in P-51H
the SL climb was 4990fpm and 3200fpm at 25000. The F8F per the same 1949 SAC data, with full 180 gallons at Combat power did 4465 at SL but no data for 25000 feet. Time to 25000 feet for P-51H at 9470 pounds GW (full 260 gallons) was 6.7 minutes. Time to 20,000 feet (full 180 gallons) was 5.5 minutes. At that comparison the F8 would have to climb the next 5000 feet in 72 sec - or near SL performance.

The P-51 with 180 gallons and full ammo would be at 8810 pounds for a WL of 37 - that combined with 35% less total drag than the F8F would also make the 51H a.) a Much better turner than the P-51B, b.) turn as well as the F8F or better, c.) climb even better than full internal fuel difference noted above, d.) accelerate better, e.) dive faster.

But F8F will always have better stall and low speed characteristics than the P-51H

grampi · Apr 28, 2016

drgondog said:
That is true Greg. The F8F is second only to F4F for lowest Navy fighter fuel load but both the P-40 and P-39 carried less fuel.

The key point regarding P-51H versus F8F is to truly compare as much apples to apples with respect to the selected Combat Weights as well as engine performance.

Notably when comparing the P-51H to Bearcat, by today's standards, nobody is a.) running at Combat/WEP, b.) 150 Octane Fuel, c.) Water injection - all of which were used to squeeze more performance out of the Merlin 1650-9 Engine in comparison to P&W R2800-30W.

But - given the P-51H in interceptor mode, namely full ammo but only 180 gallons of fuel, and using the fully configured 1945-1946 set up when 150 octane fuel was still available, the 1650-9 at 90"/WI put out almost as much HP as the R2800-30WI at SL then more HP after 15,000 feet until FTH in the 22,000-23000 foot range.

At SL and FTH the 51H had about 20+mph speed advantage and the P-51H climbed better at both altitudes. With full 260 gallons in P-51H
the SL climb was 4990fpm and 3200fpm at 25000. The F8F per the same 1949 SAC data, with full 180 gallons at Combat power did 4465 at SL but no data for 25000 feet. Time to 25000 feet for P-51H at 9470 pounds GW (full 260 gallons) was 6.7 minutes. Time to 20,000 feet (full 180 gallons) was 5.5 minutes. At that comparison the F8 would have to climb the next 5000 feet in 72 sec - or near SL performance.

The P-51 with 180 gallons and full ammo would be at 8810 pounds for a WL of 37 - that combined with 35% less total drag than the F8F would also make the 51H a.) a Much better turner than the P-51B, b.) turn as well as the F8F or better, c.) climb even better than full internal fuel difference noted above, d.) accelerate better, e.) dive faster.

But F8F will always have better stall and low speed characteristics than the P-51H

It's looking more and more like the P-51H is the most awesome plane, and certainly more awesome than the Bearcat...

MrMojok · Apr 28, 2016

Not true, poll has four YES votes and TWO affirmative votes!

grampi · Apr 28, 2016

MrMojok said:
Not true, poll has four YES votes and TWO affirmative votes!

Aren't they the same thing?

GregP · Apr 28, 2016

Good thing they're both on the same side, huh?

MrMojok · Apr 28, 2016

Yes the poll is quite obviously a joke

wuzak · Apr 29, 2016

tomo pauk said:
There was a story about the P-47 with contra-rotating props, the aircraft nicknamed as 'Double twister'. The fin/rudder assembly was canted couple of degrees on the usual P-47s, and somehoe people forget to installa the rudder with 0 deg inclination. So the Double Twister almost crashed on the 1st flight due to, now symetric thrust being applied with a non-symetric angle of the rudder.

One of the Hawker Tornadoes was fitted with a modified Vulture and de Havilland Contra-Props. It was said to be less stable as well. Maybe due to the fin/rudder incidence of the Tornado?

davparlr · Apr 29, 2016

I'm not sure anybody tried to break any records with the piston powered P-51H, which the AF already determined to be obsolete. The AF was really all wrapped up with the new jets while the Navy was struggling with their performance on carriers due to limited thrust. As such the Navy was still trying to sell there woefully underfunded service using all they really had available, piston powered fighters.

GregP · Apr 30, 2016

When you add more prop blades up front, you add more side area up front and need more fin and rudder area to compensate. Otherwise is destabilizes the aircraft. Adding a 4-bladed prop from a P-63 to a P-39 will make it almost unflyable. It killed air racing's Mike Carol and has raised it's ugly head on many past occasions.

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