F8F Bearcat Questions

[grampi]

If we're talking monstrous power in a small air frame than you'd have to go a long way to beat the Supermarine Spiteful and Seafang.

With 3,300+ hp in a 9,070 lb air frame, the Griffon 101 powered version of the Spiteful (RB518) had a maximum speed of 494 mph (Full Supercharger (FS) gear at 27,500 ft, 2750 rpm at +25lb boost). It had a rate of climb of 4,750 ft/min at that take off weight.

If the 'Bearcat' was the 'most awesome piston engine aircraft ever', then we'll need another word for the Spiteful

Cheers

Steve

Though the Bearcat wasn't as fast, it had a higher ROC, and was AT LEAST a match for the Spiteful in terms of maneuverability...

 

[drgondog]

Greg - you know a lot more about the racing info than I do. I learned a lot from your post above and have to ponder the small span wise bump on the upper leading edge. It seems clear that it provided a transition point for the boundary layer but I would have to see wind tunnel data to better understand the drag effects.

As to Ghost - I would be curious regarding the load analysis performed on the entire elevator and tab system at those Q Loads. Do you know if they modified the angle of incidence for the horizontal stab?

 

[stona]

Though the Bearcat wasn't as fast, it had a higher ROC, and was AT LEAST a match for the Spiteful in terms of maneuverability...

The Bearcat was 70 mph slower and had a rate of climb about 180 ft/min less than the Spiteful according to my data.

Data varies, so best just say that the two had similar rates of climb.

Cheers

Steve

 

[grampi]

The Bearcat was 70 mph slower and had a rate of climb about 180 ft/min less than the Spiteful according to my data.

Data varies, so best just say that the two had similar rates of climb.

Cheers

Steve

I've seen published climb rates for the Bearcat anywhere from 4500 fpm to 6300 fpm, so it's tough to say what its actual climb rate was...

 

[stona]

I've seen published climb rates for the Bearcat anywhere from 4500 fpm to 6300 fpm

Which doesn't inspire confidence The figure depends on a lot of variables.

At the weight I gave, clean, the Spiteful figure for that aircraft is from the A&AEE At least we know that is reliable

Cheers

Steve

 

[grampi]

Which doesn't inspire confidence The figure depends on a lot of variables.

At the weight I gave, clean, the Spiteful figure for that aircraft is from the A&AEE At least we know that is reliable

Cheers

Steve

I'm sure someone will chime in with some reliable references for the Cat...it's amazing what info these folks can come up with...

 

[Shortround6]

Trouble is you have two different Bearcats. The -34W engine was good for 2100hp for take-off and 1700hp at 16000ft military power in the -1 Bearcat and the -30W engine in the -2 bearcat with 2250hp for take-off (and military at sea level) and 1600hp at 22,000ft military.
All these ratings are "dry" and both engines had water injection. The 6300fpm sounds too good to be true without some sort of help or stunt while the 4500fpm may be bit low.
The -2 Bearcat was about 30-34mph faster than a -1 Bearcat.

 

[tomo pauk]

SAC for the F8F-2 is here: http://alternatewars.com/SAC/F8F-2_Bearcat_SAC_-_1_September_1949.pdf
Makes 4400+ fpm, uses 2500 HP (no ram).
Data sheets for the F8F-1 are posted here: link
Makes 4570 fpm, uses 2380 HP (no ram).

FWIW

 

[grampi]

Trouble is you have two different Bearcats. The -34W engine was good for 2100hp for take-off and 1700hp at 16000ft military power in the -1 Bearcat and the -30W engine in the -2 bearcat with 2250hp for take-off (and military at sea level) and 1600hp at 22,000ft military.
All these ratings are "dry" and both engines had water injection. The 6300fpm sounds too good to be true without some sort of help or stunt while the 4500fpm may be bit low.
The -2 Bearcat was about 30-34mph faster than a -1 Bearcat.

Just a guess here, but I'm wondering if the 6300 fpm figure is for the G-58A? That sounds way too high for the military version....

 

[GregP]

Hi Bill,

Find the pdf report of the Dago Red wing bump attached. Rather obviously, I missed the 50° from LE radius point claim. I plead guilty there as I last read this some 10 years ago.

I am not aware of the Ghost's incidence modifications, if any, but Jimmy was going faster than any non-modified P-51 I know of, so I suspect the incidence mods were done, without any proof of same. If they did the mods, the correct procedure for racers is to eliminate the downthrust and set both wing and tail to zero ° incidence, and eliminate the vertical fin incidence, too ---- make the airframe straight.

In doing so they sacrifice the good low-speed handling, but gain a LOT at the upper end of the envelope. The exact mods are sort of a Reno front runner secret, but you at least need to make such changes that will leave you some nose-down trim at 500+ mph IAS or there isn't much reason to make the mods. If you don't have at least a good 3,000+ HP, there isn't much point in making extreme mods.

Most really fast racers do more mods, but if you stand behind any P-51 on the ground, you can see the vertical fin incidence if you look for it. As I said, there are other mods that are required for various reasons and the complete list is sort of aircraft by aircraft. Good luck getting anyone to fully describe them all! I know that if a mod actually works, it becomes a closely-guarded secret. I'm sure you are aware that air leaks into and out of the fuselage cause a LOT of drag (you can probably write a text on it), so there is considerable effort expended to stop any fuselage (and wing & tail) leakage.

None of the front runners are running stock P-51 airfoils on the wing. All of the fast guys regardless of engine or airframe have profiled the wing and perhaps the horizontal tail as well. The front runners also run formula 1 canopies to decrease the canopy drag, and most are licensed in the Experimental Exhibition category. So they don't have to run conforming propellers. Most of the really fast P-51s are running props shorter than the minimum prop diameter for a Limited category aircraft, with the ability to get to coarser pitch angles.

I'll PM you about it.

As for the Bearcat being 70 mph slower, you must be talking about the F8F-1, not the F8F-2 (I posted this before I saw Shortround's post above). A stock F8F-2 could hit 455 mph at best altitude. At least that's what the pilot's manual says. All the Bearcat pilots I know say it will go faster, with or without the guns in the wings.

I believe the Navy SAC specs are for a Bearcat at gross weight, full ammo, full fuel, carrying a centerline fuel tank, if I recall right. Without the centerline fuel tank, it wasn't going to stay airborne much longer than a Spitfire, but was probably a blast while the prop was turning.

 

[stona]

SAC for the F8F-2 is here: http://alternatewars.com/SAC/F8F-2_Bearcat_SAC_-_1_September_1949.pdf
Makes 4400+ fpm, uses 2500 HP (no ram).
Data sheets for the F8F-1 are posted here: link
Makes 4570 fpm, uses 2380 HP (no ram).

FWIW

That is pretty much the data I had. So, the Spiteful tested at The A&AEE did indeed have a higher rate of climb at 4,750 ft/min,, as well as being much faster, than the Bearcat.
On the original posters scale of awesomeness that makes the Spiteful quite a bit more awesome

This was a Spiteful sent for assessment. It was equipped with service paraphernalia and I have given the take off weight, but an 'in service' aircraft might have been a bit heavier.

I like the Bearcat, it was a very good aircraft. Interestingly my own father was flying them as an advanced trainer at NAAS Kingsville in January 1953. It must have been fairly easy to handle as he only had a total on all types of just over 200 hours when he started flying the F8F-1.
He made his first carrier landings in various F6F-5s in June, maybe easier to get down on the deck?

Cheers

Steve

 

[drgondog]

Hi Bill,

As for the Bearcat being 70 mph slower, you must be talking about the F8F-1, not the F8F-2 (I posted this before I saw Shortround's post above). A stock F8F-2 could hit 455 mph at best altitude. At least that's what the pilot's manual says. All the Bearcat pilots I know say it will go faster, with or without the guns in the wings.

Greg - I didn't make any comment about slow or fast re: F8F to my recollection. The SAC for the -2 posts 448mph at 28000 feet with full internal fuel and external belly tank and wing racks for Combat power. The FTH for the R2800-30W is 23,500 at Combat power cited in the report for 1800 HP. Without racks it says +11kt more so the F8F entirely clean but full combat load internally seems to be about 459 mph.

I believe the Navy SAC specs are for a Bearcat at gross weight, full ammo, full fuel, carrying a centerline fuel tank, if I recall right. Without the centerline fuel tank, it wasn't going to stay airborne much longer than a Spitfire, but was probably a blast while the prop was turning.

The GW points to full internal combat load for Column denoted by (2) which points to the TAS above (448mph @28000) and 4465 rpm (SL) with 1110 pound of fuel. The very first column (1) at the top has an additional 900 pounds of fuel (150 gal external) and has the more demure 'best' of 398mph at 25000 feet and 2550 fpm at SL for Combat power.

 

[tomo pauk]

The listed FTH of the engine is for a static engine. High speed runs mean plenty of ram at those speeds (450 mph, give or take), so the FTH 'climbs' accordingly by almost 6000 ft.
The condition (2) is indeed for a clean aircraft, with racks that cost 11 kt at SL, 10 kt (~11.5 mph) at altitude. So we're going to have the 'rack-less' F8F-2 touching 398 kt = 458 mph.

 

[drgondog]

It is interesting to point out that none of our best Naval fighters would have served well as 8th AF escorts during WWII, save Penetration and Withdrawal. Both the F6F and F8F had at least 20% less internal fuel (250/180 gallons respectively) than the early P-47D's and only the F4U-1A&C had 360 (same as late model P-47D) but even it dropped to 237 for the F4U-1D.

The F4U-1A would have been as effective as the P-47D as far as range is concerned, maybe a smaller combat radius due to lower optimum cruise speed at 25K - but the P-47D-25 was in production at the same time, arriving in squadron level numbers by July, 1944 - so both were too late for ETO as far as target escorts.

 

[GregP]

I didn't re-address my comment, but they weren't aimed at you, Bill. I should have said Stona and I should have opened the SAC file before posting. The Bearcat is still faster than the manual says, according to pilots of same.

But I hope you noticed the attached file above on the aerodynamic "bump" that was fitted to Dago Red. I confess it didn't make a lot of sense to me, but the effect can be seen clearly on page 5 in the charts.

Dago Red has been taken down to bare metal and was being returned to stock configuration when I last got an update, so right now I do not know if there is any aircraft in the world with this modification that is flying, but it is there for people to look at. It is likely that bump was tailored specifically to the airfoil Dago Red was using, and would have to be investigated for any other airfoil, though I'm sure the bump could be applied too any laminar flow wing with some careful study. It might be applicable to a stock P-51 airfoil, too, but probably not the same shape or placement.

 

[drgondog]

That is pretty much the data I had. So, the Spiteful tested at The A&AEE did indeed have a higher rate of climb at 4,750 ft/min,, as well as being much faster, than the Bearcat.
On the original posters scale of awesomeness that makes the Spiteful quite a bit more awesome

This was a Spiteful sent for assessment. It was equipped with service paraphernalia and I have given the take off weight, but an 'in service' aircraft might have been a bit heavier.

I like the Bearcat, it was a very good aircraft. Interestingly my own father was flying them as an advanced trainer at NAAS Kingsville in January 1953. It must have been fairly easy to handle as he only had a total on all types of just over 200 hours when he started flying the F8F-1.
He made his first carrier landings in various F6F-5s in June, maybe easier to get down on the deck?

Cheers

Steve

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.

What are the equivalent spreads for the Spiteful? .

 

[drgondog]

Tha

I didn't re-address my comment, but they weren't aimed at you, Bill. I should have said Stona and I should have opened the SAC file before posting. The Bearcat is still faster than the manual says, according to pilots of same.

But I hope you noticed the attached file above on the aerodynamic "bump" that was fitted to Dago Red. I confess it didn't make a lot of sense to me, but the effect can be seen clearly on page 5 in the charts.

Dago Red has been taken down to bare metal and was being returned to stock configuration when I last got an update, so right now I do not know if there is any aircraft in the world with this modification that is flying, but it is there for people to look at. It is likely that bump was tailored specifically to the airfoil Dago Red was using, and would have to be investigated for any other airfoil, though I'm sure the bump could be applied too any laminar flow wing with some careful study. It might be applicable to a stock P-51 airfoil, too, but probably not the same shape or placement.

Thanks Greg - I will look at it in depth later today and email you later. It has to be a boundary layer trip (IMO - often wrong but rarely uncertain). The sketch positions it aft of leading edge so I misread your 50* as 50 degrees from LE nose

 

[stona]

What are the equivalent spreads for the Spiteful? .

Not given, just the take off weight of 9,070lbs. The original auw for the Spiteful was calculated at 9,000lbs and the auw of another Spiteful (RB515) rose from an initial 8,650 lbs to 9,222 lbs as bits were bolted on or heavier bits added.

RB518, to which the data pertains was the only Spiteful Mk XVI built and the only weights I have found for it are a tare weight of 7,556 lbs (with a different propeller) and that take off weight for the tests of 9,070lbs. It certainly had a significant load on board, but no external stores..

I think the fastest rate of climb for any British fighter would be the maximum rate for the Spitfire Mk 24 which the A&EE gave as 4,900 ft/min at 2,000 ft in MS gear.

Cheers

Steve

 

[drgondog]

I

But I hope you noticed the attached file above on the aerodynamic "bump" that was fitted to Dago Red. I confess it didn't make a lot of sense to me, but the effect can be seen clearly on page 5 in the charts.

Dago Red has been taken down to bare metal and was being returned to stock configuration when I last got an update, so right now I do not know if there is any aircraft in the world with this modification that is flying, but it is there for people to look at. It is likely that bump was tailored specifically to the airfoil Dago Red was using, and would have to be investigated for any other airfoil, though I'm sure the bump could be applied too any laminar flow wing with some careful study. It might be applicable to a stock P-51 airfoil, too, but probably not the same shape or placement.

One comments that immediately come to mind. The method of applying the fine mesh Navier Stokes flow CFM solution combined with the small change relaxation differentials to drive an airfoil section to explore shock wave mitigation is very interesting.

Comments about the results:

1.) looking at both the Cp distribution of bump modification it seems clear to me that it triggers a Boundary layer separation at the bump triggering an adverse pressure gradient - you can see Cp dip there and continue down. Presumably by the explanation, the perturbation at the bump influences the strength of the shock wave forming down stream, chord wise, from the 'bump'. One explanation, or question really, is whether the shock forms at the bump due to the upstream velocity gradient increase on the forward portion of the bump, perturbing the downstream formation near 45-50% Chord of the airfoil?

2.) Equally interesting to me is that the plots of CD vs Mach doesn't show a reduction in CD for the bump modified wing until ~ 0.745M
At 5000 feet and STP, 0.745 = 557 mph so unless my math is off (possible) for the Reno altitudes the benefit is not available in reduced drag until that range of speeds.

At SL it becomes useful at 568mph

I understand the approach on the math - as well as Calculus of Variations to specify a pressure distribution result desired for a three dimensional surface. That said I never actually did do a real world application of either math. Control Theory, Tensors, Calculus of Variations and Chaos Theory is as high as I got before feeling like I was in Really strange territory.

To me Engineering is the discipline which uses math as a tool to apply useless, incoherent gobblygook regurgitated by PhD math majors - to real world problems.

 

[drgondog]

Not given, just the take off weight of 9,070lbs. The original auw for the Spiteful was calculated at 9,000lbs and the auw of another Spiteful (RB515) rose from an initial 8,650 lbs to 9,222 lbs as bits were bolted on or heavier bits added.

RB518, to which the data pertains was the only Spiteful Mk XVI built and the only weights I have found for it are a tare weight of 7,556 lbs (with a different propeller) and that take off weight for the tests of 9,070lbs. It certainly had a significant load on board, but no external stores..

I think the fastest rate of climb for any British fighter would be the maximum rate for the Spitfire Mk 24 which the A&EE gave as 4,900 ft/min at 2,000 ft in MS gear.

Cheers

Steve

Thanks Steve - so the GW for the example of 4900 fpm was ? Did either Spiteful come equipped with external racks? The SAC reference for the P-51H demonstrated a spread of 850 fpm due to internal fuel load difference between 60 gallons and full internal fuel of 255 gallons as well as existence of racks, dropping top speed in the 10mph range from the ones cited.