Maneuverability vs Speed

Juha3 · Jun 21, 2023

BarnOwlLover said:
18 lbs boost/67 in/hg was what the Merlin was rated for as far as WEP until 115/145 and 150 octane fuel became common in 1944 (second half the year). This allowed Mustangs to run to 72in/hg/21 lbs, later 75 in/23 lbs, and later 80 in/25 lbs.

Point is that the Griffon with 18 lbs boost was still WEP. WEP/Combat power was intended primarily for that, emergency or combat. IE, evading an enemy, engaging and enemy, or carrying out an interception. ..

Yes, I knew that. And the fact is that when the overboosting first came into use in Merlin Spits, the order was that the pilot had to notify the ground crew immediately after landing its use, so that they could do an extra check on the engine. When it was noticed that the use was not always reported, the British introduced a wire that broke if the throttle was pushed to overboost, so the ground crew would know for sure that it had been used. The very fact that such a backup system was developed proves that it was used in combat situations. Likewise, when it first came into use, mentions of its use appeared in combat reports. So yes, at least British and CW front line sqns used it. And the use was allowed only for 5 minutes.

NeilStirling · Jun 21, 2023

Some Mustang examples of over boost,

Encounter Reports noting high boost obtained with 150 grade fuel

1st Lt. Raymond R. Flowers, 1 November 1944, 20th FG	"I closed steadily pulling over 70 inches."
1st Lt. James F. Hinchey, 14 November 1944, 353rd FG	"For fifteen minutes at 74" hg and indicating 600 mph…"
2nd Lt. Thomas R. Drybrough, 27 November 1944, 353rd FG	"I had been pulling over 70" H.G. and was indicating about 425 MPH at approximately 14,000 feet."
1st Lt. Charles E. Yeager, 13 September 1944, 357th FG	"I rolled over and was pulling around 70"Hg."
Capt. Charles E. Yeager, 6 November 1944, 357th FG	"I got behind him and was pulling 75" Hg."
Lt. Col. Roy A. Webb, 25 June 1944, 361st FG	"I closed very slowly and pulled as much as 70 inches of mercury."
1st Lt. Thomas H. Hall, 15 August 1944, 364th FG	"I put on 70 inches and gradually pulled up on them."
Lt. Col. Kyle L. Riddle, 24 December 1944, 479th FG	"I pulled about 70" to 75" mercury..."
F/Lt Pearson, 5 April 45, 65 Squadron	"Opening up to 70 inches I overtook him..."
F/Lt. G. M. Davis, 23 March 1945, 129 Squadron	"Opened up to +25 lbs of boost 3,000 revs and dived down to engage."

Neil

Shortround6 · Jun 21, 2023

Wild_Bill_Kelso said:
Not every air battle in WW2 boils down to 8th Air Force flying escorted heavy bomber missions out of England

Oh, yes, the after the BoB the British just sat around with their thumbs up their bums and waited for the 8th Air Force to show up and take over the air war in North West Europe.
So it didn't matter what the British and Germans were using in 1941/42. right?
Of course the 8th AIr Force doesn't even bomb Germany (they bombed France and the Low Countries) until Jan 1943 (?) so we can just discount any air combat over North West Europe until then right?

The Ki-43 and the A6M2 would not have shown up well over the eastern front in 1942,
Over 1100 LA-5s built in 1942.
310mph Ki -43 Is vs YAK-7s ?
List goes on.
Ki-43 I vs PE-2 bombers?
Ki-43s with two 12.7mm machine guns vs IL-2s?

Different theaters at different times were fought at different altitudes and different conditions. What allowed the Japanese to do well in the Pacific didn't work as well in other places.
In fact the Japanese were running into trouble late 1942. Once areas turned into slogging matches (the Solomons) the Japanese were in trouble. The Extra range of the lightly protected (or unprotected) Japanese aircraft became trap. It doesn't take much difference in losses to go from sustainable to unsustainable. Just a few percent, also depends on replacement rates.
Now this may not have been realized at the time by the forces involved on either side (see WW I when "one more push over the top" would have changed the war).

drgondog · Jun 21, 2023

GregP said:
I'm not too sure anyone was going 450 mph in 1944, except in testing. As I've argued before, using WER on a regular basis just wasn't part of normal operations. Nobody who wanted to get home cruised at max power for too long. The engines just weren't designed for it. WER was a thing used in factory testing and wasn't normally used except to save your own life when you were about to die. P-51D mustangs were supposed to have a top speed of 437 mph and that was at WER and 26,000 feet. Everywhere else it was slower than that. Merlins were very good at making continuous power but were never very good at running at high power for long periods without getting heat-soaked.

I have no doubt they could cruise at 315 mph TAS, but they weren't flitting about at 430 mph unless they were diving from altitude. If they did that, they were in pursuit or the escort was terminated and they were going to the deck to strafe on the way home.

Greg - contrary to popular belief the P-51D was faster than the P-51B for same loadout and external conditions. GW=9700 for D-15, 9335 and 9600 for B-15

P-51D-15 With Racks, at Military Power 61"/3000RPM = 438mph at 28000. At Max Continuous Power 46"/2700RPM =420mph @. At 67" = 442mph at 26,000 feet.

P 51D Performance Test

Contrast the P-51B-15 with same engine (1650-7) at same MP and WER of 61" and 67" respectively and with racks.
With Racks, at WER 67"/3000RPM =426mph at 24,000

P-51B Performance Test

For No fuse tank, no wing racks and a 1650-3 in P-51B-5. GW@takeoff = 9335
at 67"MP/3000RPM, top speed =420 at 24K, 442@29K

P-51B Performance Test

www.wwiiaircraftperformance.org

Summary - in combat condition with external racks and 60gal Fuse tank burned, but full wing fuel - the P-51D is faster in Military Power than the P-51B at WER.

The two major drag differences are a.) the wing racks (Delta = 6-8mph) and b.) canopy/windshield design for the D (~4-5mph)

I have one flight test for D-10 at Fighter condition takeoff GW of 8900 pounds (100gal ful), light oil, P-51B ammo loadout) where top speed at 67" and 25K is 452mph w/o racks and max ROC at 4200fpm - wich would have been best interceptor until P-47M in similar light condition.

yulzari · Jun 21, 2023

The RAF was well aware of the deficiencies and benefits in the aeroplanes it used. But used what it had when it had them as need arose which did not always coincide. eg they did not send Gladiators to France in 1939 because they were of good performance but because they were building up home defence with the latest monoplanes and, in particular, some of the 'airfields' (read fields) in France were marginal for Hurricanes but readily useable for Gladiators. The same applied to the defence of Plymouth in the BoB where only Gladiators could use the local airfield. Within 2 years they had built a new one higher up with the rubble of the destroyed city capable of taking all types up to 4 engined maritime reconnaissance types fully loaded. Hawker Henley's kept falling off the end of the airfield by Bude but the adjacent AA gunnery school still needed high speed target rugs so the Henleys kept on being used and lost.

The poor higher altitude performance of Allison engines but good low altitude resulted in the Tomahawk being first used in place of Lysanders by Army Cooperation squadrons for tactical reconnaissance and the Allison Mustang took over and was used all the way to the end of the war.

We look at the Top Trumps numbers but a real air force has to meet the threat and use what it can get not require performance X and wait until they have it. Type X might have more or less speed and/or maneoverability than its foes but it gets used if that is what you have.

Where the Axis countries all fell short was in pilot training. The only non mechanical force multiplier. The Commonwealth saw to this from before the start and built it further and further up as time passed. The USA saw this (indeed provided some of it) and planned and delivered on it. The Axis went for a race to the bottom.

SaparotRob · Jun 21, 2023

Wild_Bill_Kelso said:
Not every air battle in WW2 boils down to 8th Air Force flying escorted heavy bomber missions out of England

That's just crazy talk.

Greg Boeser · Jun 21, 2023

SaparotRob said:
That's just crazy talk.

Blasphemous, actually.

BarnOwlLover · Jun 21, 2023

drgondog said:
Greg - contrary to popular belief the P-51D was faster than the P-51B for same loadout and external conditions. GW=9700 for D-15, 9335 and 9600 for B-15

P-51D-15 With Racks, at Military Power 61"/3000RPM = 438mph at 28000. At Max Continuous Power 46"/2700RPM =420mph @. At 67" = 442mph at 26,000 feet.

P 51D Performance Test

Contrast the P-51B-15 with same engine (1650-7) at same MP and WER of 61" and 67" respectively and with racks.
With Racks, at WER 67"/3000RPM =426mph at 24,000

P-51B Performance Test

For No fuse tank, no wing racks and a 1650-3 in P-51B-5. GW@takeoff = 9335
at 67"MP/3000RPM, top speed =420 at 24K, 442@29K

P-51B Performance Test

www.wwiiaircraftperformance.org

Summary - in combat condition with external racks and 60gal Fuse tank burned, but full wing fuel - the P-51D is faster in Military Power than the P-51B at WER.

The two major drag differences are a.) the wing racks (Delta = 6-8mph) and b.) canopy/windshield design for the D (~4-5mph)

I have one flight test for D-10 at Fighter condition takeoff GW of 8900 pounds (100gal ful), light oil, P-51B ammo loadout) where top speed at 67" and 25K is 452mph w/o racks and max ROC at 4200fpm - wich would have been best interceptor until P-47M in similar light condition.

Kind of makes one wonder how useful the XP-51F or G, or the P-51H would've been as an interceptor--since improving rate of climb was one of the biggest objectives of the lightweight Mustang program. But then again, it seems that the P-51D would've been quite useful in that role on light fuel and with 75" or 80" boost that happened later in the war.

Wild_Bill_Kelso · Jun 21, 2023

Shortround6 said:
Oh, yes, the after the BoB the British just sat around with their thumbs up their bums and waited for the 8th Air Force to show up and take over the air war in North West Europe.
So it didn't matter what the British and Germans were using in 1941/42. right?
Of course the 8th AIr Force doesn't even bomb Germany (they bombed France and the Low Countries) until Jan 1943 (?) so we can just discount any air combat over North West Europe until then right?

I just think most of the Air Combat in 1941-1943 was in North Africa / the Med, Russia, the Pacific, and China. There were a few 'big shows' like Dieppe, and they did some daylight bombing and raids like at Eindhoven. Channel Dash. Various Fw 190 jabo raids and so on. But there was fighting over the ground / naval war in these other Theaters, which is a bit more consequential in this period.

Shortround6 said:
The Ki-43 and the A6M2 would not have shown up well over the eastern front in 1942,
Over 1100 LA-5s built in 1942.

I think Ki-43 and A6M, maybe with some Japanese bombers would have still done very well over the Russian front in 1942. It's an interesting scenario. It's a safe bet that Ki-43 > LaGG3, we know it's better than an I-16 or a Hurricane which were still in use then, and given how Ki-43 and A6M performed against P-39s I doubt La5 or Yak-1 would be impossible to overcome.

The vastly superior range of the Ki-43 and (especially) A6M would allow them to attack at locations the Soviets were not expecting to see fighters, like way behind the lines, remote or soggy parts of the front etc. Especially if you throw in some long range Japanese bombers ala G4M, Ki-48, Ki-49. I'd say the same also applies in reverse to the Germans.

Shortround6 said:
310mph Ki -43 Is vs YAK-7s ?
List goes on.
Ki-43 I vs PE-2 bombers?

That could be tricky I admit, hard for Ki-43 to catch a Pe-2 if it was cranked up to full speed. They did shoot down a few DB-7 / A-20s though so I guess there were ways... most of the other bombers active on the Russian Front in this period though would be within the performance limits of the Ki-43, and not particularly well defended either.

Shortround6 said:
Ki-43s with two 12.7mm machine guns vs IL-2s?

Two 12.7mm machine guns isn't a whole lot worse than a lot of Soviet fighters at that time. One 12.7 and one 20mm or one 7.62 and one 20mm were pretty common

The A6M was more heavily armed than most Soviet fighters in 1942.

Shortround6 said:
Different theaters at different times were fought at different altitudes and different conditions. What allowed the Japanese to do well in the Pacific didn't work as well in other places.

I don't think we know that for sure... you have some points here but I suspect the Japanese fighters would still be troublesome anywhere in the world in 1942.

Shortround6 said:
In fact the Japanese were running into trouble late 1942. Once areas turned into slogging matches (the Solomons) the Japanese were in trouble. The Extra range of the lightly protected (or unprotected) Japanese aircraft became trap. It doesn't take much difference in losses to go from sustainable to unsustainable. Just a few percent, also depends on replacement rates.

I agree the Solomons, and New Guinea, became a slog, but the Japanese air forces (Army and Navy) were still very much holding their own through 1942. It was beginning to turn into a 'slog' (attrition war) because, in part, fighting had become concentrated in a particular area, and the Allies were starting to adapt to the Japanese tactics and kit. But the same thing was happening in North Africa and in Russia too.

Shortround6 said:
Now this may not have been realized at the time by the forces involved on either side (see WW I when "one more push over the top" would have changed the war).

I would say broadly speaking, the Japanese and German warplanes were more suited to 'lightning war' than to attrition war. But I think it would take a bit longer for the technological advantages of other nations aircraft to pull ahead. But the truth is, this is indeed like the proverbial top of the trench, we don't know what would have happened. it's fun to speculate though!

Wild_Bill_Kelso · Jun 21, 2023

Elvis said:
Because the way to get out of a situation where you're pitted against a plane and/or pilot with superior manuverability/skills is to exit, post haste, so you want an airplane with superior top speed to your opponent's.
You also want a fighter that will climb as quickly as possible (hopefully, faster than your opponent's).
Finally, you want a fighter that has superior firepower and pilot protection to your opponent's.
Combine all these together and you start designing airplanes that aren't so much super agile, as they are high speed with a big punch that can climb like a monkey. Just like the aircraft that were developed later in the war.

I would note here that many later war fighters were agile - the Fw 190 was one of the fastest rolling fighters of the war, and the P-51 was not too far behind it. The Spitfire had the remarkable turn rate and the LF versions had excellent roll too. Most of the best Soviet fighters were also very good at roll (La 5, Yak 3) and pretty good at turning as well.

Dive also matters a lot...

Elvis said:
...and FWIW, there is a story floating around somewhere that an F2A (possibly a -1, but more likely a -2) shot down a Zero in a turn fight. Witnesses claimed the Buffalo was matching the Zero, turn for turn.

Might depend on the relative fuel states. They also stripped some F2A in the field to lighten them, in some cases down to 2 guns.

Wild_Bill_Kelso · Jun 21, 2023

Where I think the A6M and to a slightly lesser extent, Ki-43 would have really been telling is in the Mediterranean campaign, notably the convoy fights and the invasion of Sicily and Italy.

Wild_Bill_Kelso · Jun 21, 2023

drgondog said:
Greg - contrary to popular belief the P-51D was faster than the P-51B for same loadout and external conditions. GW=9700 for D-15, 9335 and 9600 for B-15

P-51D-15 With Racks, at Military Power 61"/3000RPM = 438mph at 28000. At Max Continuous Power 46"/2700RPM =420mph @. At 67" = 442mph at 26,000 feet.

P 51D Performance Test

Contrast the P-51B-15 with same engine (1650-7) at same MP and WER of 61" and 67" respectively and with racks.
With Racks, at WER 67"/3000RPM =426mph at 24,000

P-51B Performance Test

For No fuse tank, no wing racks and a 1650-3 in P-51B-5. GW@takeoff = 9335
at 67"MP/3000RPM, top speed =420 at 24K, 442@29K

P-51B Performance Test

www.wwiiaircraftperformance.org

Summary - in combat condition with external racks and 60gal Fuse tank burned, but full wing fuel - the P-51D is faster in Military Power than the P-51B at WER.

The two major drag differences are a.) the wing racks (Delta = 6-8mph) and b.) canopy/windshield design for the D (~4-5mph)

I have one flight test for D-10 at Fighter condition takeoff GW of 8900 pounds (100gal ful), light oil, P-51B ammo loadout) where top speed at 67" and 25K is 452mph w/o racks and max ROC at 4200fpm - wich would have been best interceptor until P-47M in similar light condition.

Wow man, very interesting. I always thought B/C was faster, and just in general, 442 mph is booking! 452 with 4200 fpm is unreal...

GregP · Jun 21, 2023

drgondog said:
Greg - contrary to popular belief the P-51D was faster than the P-51B for same loadout and external conditions. GW=9700 for D-15, 9335 and 9600 for B-15

P-51D-15 With Racks, at Military Power 61"/3000RPM = 438mph at 28000. At Max Continuous Power 46"/2700RPM =420mph @. At 67" = 442mph at 26,000 feet.

P 51D Performance Test

Contrast the P-51B-15 with same engine (1650-7) at same MP and WER of 61" and 67" respectively and with racks.
With Racks, at WER 67"/3000RPM =426mph at 24,000

P-51B Performance Test

For No fuse tank, no wing racks and a 1650-3 in P-51B-5. GW@takeoff = 9335
at 67"MP/3000RPM, top speed =420 at 24K, 442@29K

P-51B Performance Test

www.wwiiaircraftperformance.org

Summary - in combat condition with external racks and 60gal Fuse tank burned, but full wing fuel - the P-51D is faster in Military Power than the P-51B at WER.

The two major drag differences are a.) the wing racks (Delta = 6-8mph) and b.) canopy/windshield design for the D (~4-5mph)

I have one flight test for D-10 at Fighter condition takeoff GW of 8900 pounds (100gal ful), light oil, P-51B ammo loadout) where top speed at 67" and 25K is 452mph w/o racks and max ROC at 4200fpm - wich would have been best interceptor until P-47M in similar light condition.

Thanks, Bill.

I wasn't saying above that nobody ever went 450 mph in combat, I was saying that not many people did it frequently.

In the ETO, the P-51 flew about 213,873 combat sorties. Let's say the slice of 10 comments above was only 10% of the WER use. That means there were about 100 occasions when WER as used. That's 0.4 of 1% of the time, which qualifies as almost never. I never said it wasn't used. I said people who used it frequently maybe or likely didn't get home at some point in their exuberance. That's what many old pilot told me, anyway. They reserved heavy overboost for when they were in a bad situation. Not to go get kills on a regular basis.

Seeing a few encounter reports where overboost was used doesn't really change the impression. Now, if it turns out there was as much as, say, 5% of the time when overboost was used, then that sort of changes the narrative a bit. It doesn't mean the pilots I spoke with were wrong ... it means there were many people who operated differently from the guys I spoke with. I can live with that, should it prove to be the case. I just think that most pilots were rural boys, there being much more rural area than today in WWII, and rural boys generally know how to take care of an engine. The farm tractor is too valuable to abuse it unnecessarily. To me, who first learned to drive a Farmall Cub tractor, I learned not to use full throttle unless there was a good reason to do so. Most of time we used only enough over idle to get the job done. As a result, the tractor was still running great when it was 30 years old.

Translate that into a P-51 and I would have no problem running at high cruise and no problem going to Military power when combat was about to be joined. But I'd avoid overboost generally unless there was a need to use it. I wouldn't have an issue going to overboost for a minute or even a bit more in a pinch, but shoving it all the way forward and leaving it there for awhile just invites the engine to throw a scrap iron fit, and reasonably justly so.

In my Ford Mustang GT, I don't have a problem taking the Coyote engine out to 7,000 rpm ... but it isn't there long. Just long enough to get there and shift. My 2019 Ford Mustang is 4 years old now and the total time it has spent at more than 6,000 rpm can be measured in tens of seconds, and likely adds up to less than 1 minute total, especially since I don't street race.

I talked with warbird pilots a bit over the years. They generally don't have a problem taking off at Military power (or whatever power they get from 100LL, which is basically 100/130 fuel). But they don't leave it there. They take off and then throttle back after initial climbout, which really doesn't take long. If you operate the old engines by the book and run at economy cruise most of the time, you get good, long life from the engines.

Wild_Bill_Kelso · Jun 21, 2023

GregP said:
Thanks, Bill.

I wasn't saying above that nobody ever went 450 mph in combat, I was saying that not many people did it frequently.

In the ETO, the P-51 flew about 213,873 combat sorties. Let's say the slice of 10 comments above was only 10% of the WER use. That means there were about 100 occasions when WER as used. That's 0.4 of 1% of the time, which qualifies as almost never. I never said it wasn't used. I said people who used it frequently maybe or likely didn't get home at some point in their exuberance. That's what many old pilot told me, anyway. They reserved heavy overboost for when they were in a bad situation. Not to go get kills on a regular basis.

Seeing a few encounter reports where overboost was used doesn't really change the impression. Now, if it turns out there was as much as, say, 5% of the time when overboost was used, then that sort of changes the narrative a bit. It doesn't mean the pilots I spoke with were wrong ... it means there were many people who operated differently from the guys I spoke with.

I suspect this is probably the thing. One of the amazing things about the Mustang is that it was used all over the globe. Many different Theaters and situations. Tactical or strategic escort, interdiction, interception, CAS. There was probably a lot of variation. Mustangs were used in the Pacific and China a bit as well for example and I doubt they needed to hit WER there as much

GregP said:
I can live with that, should it prove to be the case. I just think that most pilots were rural boys, there being much more rural area than today in WWII, and rural boys generally know how to take care of an engine. The farm tractor is too valuable to abuse it unnecessarily. To me, who first learned to drive a Farmall Cub tractor, I learned not to use full throttle unless there was a good reason to do so. Most of time we used only enough over idle to get the job done. As a result, the tractor was still running great when it was 30 years old.

Translate that into a P-51 and I would have no problem running at high cruise and no problem going to Military power when combat was about to be joined. But I'd avoid overboost generally unless there was a need to use it. I wouldn't have an issue going to overboost for a minute or even a bit more in a pinch, but shoving it all the way forward and leaving it there for awhile just invites the engine to throw a scrap iron fit, and reasonably justly so.

In my Ford Mustang GT, I don't have a problem taking the Coyote engine out to 7,000 rpm ... but it isn't there long. Just long enough to get there and shift. My 2019 Ford Mustang is 4 years old now and the total time it has spent at more than 6,000 rpm can be measured in tens of seconds, and likely adds up to less than 1 minute total, especially since I don't street race.

I talked with warbird pilots a bit over the years. They generally don't have a problem taking off at Military power (or whatever power they get from 100LL, which is basically 100/130 fuel). But they don't leave it there. They take off and then throttle back after initial climbout, which really doesn't take long. If you operate the old engines by the book and run at economy cruise most of the time, you get good, long life from the engines.

GregP · Jun 21, 2023

drgondog said:
Greg - contrary to popular belief the P-51D was faster than the P-51B for same loadout and external conditions. GW=9700 for D-15, 9335 and 9600 for B-15

P-51D-15 With Racks, at Military Power 61"/3000RPM = 438mph at 28000. At Max Continuous Power 46"/2700RPM =420mph @. At 67" = 442mph at 26,000 feet.

P 51D Performance Test

Contrast the P-51B-15 with same engine (1650-7) at same MP and WER of 61" and 67" respectively and with racks.
With Racks, at WER 67"/3000RPM =426mph at 24,000

P-51B Performance Test

For No fuse tank, no wing racks and a 1650-3 in P-51B-5. GW@takeoff = 9335
at 67"MP/3000RPM, top speed =420 at 24K, 442@29K

P-51B Performance Test

www.wwiiaircraftperformance.org

Summary - in combat condition with external racks and 60gal Fuse tank burned, but full wing fuel - the P-51D is faster in Military Power than the P-51B at WER.

The two major drag differences are a.) the wing racks (Delta = 6-8mph) and b.) canopy/windshield design for the D (~4-5mph)

I have one flight test for D-10 at Fighter condition takeoff GW of 8900 pounds (100gal ful), light oil, P-51B ammo loadout) where top speed at 67" and 25K is 452mph w/o racks and max ROC at 4200fpm - wich would have been best interceptor until P-47M in similar light condition.

Hi Bill,

I am assuming best interceptor for U.S.A. I think the late Spitfires could outclimb it, but not by too much. I've seen 4,700 fpm ROC on test charts for a Spitfire XIV. Makes sense if it is a ton lighter.

BarnOwlLover · Jun 21, 2023

Depends I guess on sources. I've seen anything from 4100-4700 fpm for a Spitfire IX, and 4900-5100 for a Spitfire XIV (Griffon powered). The P-51H could outclimb the Spitfire XIV, but it had a better power to weight ratio, was using WEP, and other considerations.

GregP · Jun 21, 2023

BarnOwlLover said:
Depends I guess on sources. I've seen anything from 4100-4700 fpm for a Spitfire IX, and 4900-5100 for a Spitfire XIV (Griffon powered). The P-51H could outclimb the Spitfire XIV, but it had a better power to weight ratio, was using WEP, and other considerations.

That's why I assumed Bill meant best interceptor for the U.S.A.

We tended to make our planes a bit heavier than British planes of the same general variety. At least fighters, anyway. Not sure which was better overall, but the British Spits were always the cat's meow in performance, if a bit "delicate" by comparison.

BarnOwlLover · Jun 21, 2023

Also depends on if you want to look at the XP-51F/G as interceptors, or the P-51H. Of course, there's the annoying issue that the F/G were prototypes only, and the H basically missed the war.

drgondog · Jun 21, 2023

GregP said:
Hi Bill,

I am assuming best interceptor for U.S.A. I think the late Spitfires could outclimb it, but not by too much. I've seen 4,700 fpm ROC on test charts for a Spitfire XIV. Makes sense if it is a ton lighter.

drgondog · Jun 21, 2023

Well. not even striving for 'best' - just really very good performance at 67" when running light - and really good at 72" for 4-5 minutes if necessary. That would put the D in the conversation with the Spit XIV

USN very carefully flew against P-51B w/racks and 61/67"MP at full combat GW - while stoking their F4U to WI/65".. Had the racks been removed from the B and run at 72-75"MP, it would have smoked the F4U pretty much over the entire envelope for speed and ROC

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