1000-1200 HP: long range fighter vs. interceptor?

[tomo pauk]

Any evidence for that assertion?

The reasons for the RAF's eight gun armament were very carefully worked out in the mid thirties, both theoretically and experimentally. I very much doubt that Ralph Sorley would have agreed with your contention.

Not sure that assertions need evidences, maybe my command of English language is not that good I often think it is
At any rate, I'm increasing the rate of fire of the P-40B's BMG for about 1/3rd, by relocating it in the wings. The price to pay it is the loss of a LMG, so instead of two HMGs + 4 LMGs, we now have a pair of each per plane. The side effect is that weight will be lower, and few mph are to be earned.
OTOH, the 6-8 LMG battery for the perspective LR fighter does not look out of place either.

If you go with an interrupter system then you are also going to end up with different propellers on mid/late war fighters. It's one of the reasons that the Germans stuck with a three bladed propeller system.

I've already agreed that Merlins and gun synchronizers seem not to mix well. The 1000-1200 HP LR fighter for 1943 and beyond is a no-go anyway.

The MG 151/15 did NOT work perfectly. Under certain flight conditions the belt jammed and blocked the ammunition feed. A temporary fix was made by front line armourers inserting small wooden blocks but the problem was never completely solved until the advent of the MG 151/20. You could say that the cannon armament worked reliably from about mid 1941.
I think rather more serious issues with wing skin wrinkling, wings coming off, empennages detaching at frame 9 and other problems with the elevators have somewhat overshadowed problems with the armament

Cheers

Steve

Thanks for additional info.

 

[tomo pauk]

An interesting comparison can be made between the 6,965 lbs worth of Spitfire V and 7413 lbs worth of P-40N (the 1st, lightweight examples, with 100 imp gals of internal fuel in just two tanks and 4 HMGs). Both airspeed and RoC is in the ballpark.
The bulk of P-40Ns was, however, reverted at 3 fuel tanks and ~125 imp gals internal fuel and 6 HMGs, the weight went back up at 8300 lbs, and the speed was back at ~350 mph at best altitude.

 

[Shortround6]

An interesting comparison can be made between the 6,965 lbs worth of Spitfire V and 7413 lbs worth of P-40N (the 1st, lightweight examples, with 100 imp gals of internal fuel in just two tanks and 4 HMGs). Both airspeed and RoC is in the ballpark.
The bulk of P-40Ns was, however, reverted at 3 fuel tanks and ~125 imp gals internal fuel and 6 HMGs, the weight went back up at 8300 lbs, and the speed was back at ~350 mph at best altitude.

Spitfire was ballasted to represent four 20mm cannon. Weight difference of about 240lbs from a standard MK V. although other test MK Vs are even lighter.

P-40 not only lost a fuel tank and two machine guns but had restricted ammo 235rpg. It also had aluminium radiators and oil coolers, unlike ALL previous P-40s. Magnesium wheels, no electric starter for the engine and a much smaller battery for the electric system ( some sources say NO battery but that is a bit hard to believe.) Also the wing bomb racks were deleted.

The wing racks and drag for machine gun barrels and ejection slots probably have as much to do with the reduction in speed of the later P-40Ns as the weight increase. Weight gets blamed a lot for speed changes when other things were added/subtracted from aircraft that affect drag as much as they do the weight.

 

[tomo pauk]

Indeed, the lighter Spit Vs (eg. the one tested at 6525 lbs, 2 cannons and 4 LMGs) were better climbers, with some 20% better RoC, and the speed difference was some 5 mph.

 

[Shortround6]

And there is part of the problem with the long range fighters, even 400-500lbs can have a significant impact on climb performance and ceiling. The speed doesn't change much but the planes ability to operate at altitude does. Cobber Kain's first victory was against a Do-17 photo recon plane at 27,000ft in Nov 1939. Since nobody actually knew what altitudes most of the fighting would be done at in 1941-42 let alone the rest of the war OK'ing production of fighters you KNOW are going to be at a disadvantage at altitude (20-30,000ft) is a little suspect.
It is all very well to talk of tactics and tactics are important but the methods used by certain forces don't always apply to others. The Flying Tigers did well with poor climbing, poor turning fighters compared to the Japanese BUT they had a very considerable speed advantage, a very considerable dive advantage. They had an early warning system, not radar but ground observers often gave them 20-30 minutes warning. The Japanese having to fly over occupied land with a telephone system instead of water. There "mission" was a bit different too. Cause as much damage to the Japanese as possible while minimizing their own losses. Resupply was almost non-existent. The Chinese air force was almost totally non-effective so one or two good firing passes be each fighter per raid was actually doing pretty good. No disrespect or minimizing the situation intended. The Flying Tigers (and their ground crews) did an amazing job in difficult circumstances. They were also, on average, very experienced pilots and trying to provide some sort of defense over the long haul. A few big battles might have seen them wiped out so a slow battle of attrition was more suited to their situation even if the people on the ground suffered.

But turn it around. Even with more fuel and lighting the P-40s by several hundred pounds, could the Flying Tigers have escorted a Chinese (if it existed) bomber force or allied bomber force hundreds of miles into Japanese air space successfully with the Japanese having 20-40 minutes warning they were coming?

 

[tomo pauk]

And there is part of the problem with the long range fighters, even 400-500lbs can have a significant impact on climb performance and ceiling. The speed doesn't change much but the planes ability to operate at altitude does. Cobber Kain's first victory was against a Do-17 photo recon plane at 27,000ft in Nov 1939. Since nobody actually knew what altitudes most of the fighting would be done at in 1941-42 let alone the rest of the war OK'ing production of fighters you KNOW are going to be at a disadvantage at altitude (20-30,000ft) is a little suspect.

The weight difference can originate from other sources than fuel alone.
We might consider the Spitfire II with 8 LMGs and 100 imp gals of internal fuel + 45 imp gals in drop tank (MR/LR fighter) , going against Spitfire II with 2 cannons and 4 LMGs and 85 gals (interceptor with punch good enough to kill bombers). The extra 15 imp gals of fuel + additional protected tank will add maybe 120-130 lbs. The replacement of 4 LMGs with 2 Hispanos will add circa 150 lbs, too. So our MR/LR Spitfire II does not weight an ounce more than a Interceptor Spitfire, and it is at least good streamlined. The MR/LR Spit can cover 100 miles more on internal fuel (doing 6-7 mpg, at 300-260 mph), on the other hand.

It is all very well to talk of tactics and tactics are important but the methods used by certain forces don't always apply to others. The Flying Tigers did well with poor climbing, poor turning fighters compared to the Japanese BUT they had a very considerable speed advantage, a very considerable dive advantage. They had an early warning system, not radar but ground observers often gave them 20-30 minutes warning. The Japanese having to fly over occupied land with a telephone system instead of water. There "mission" was a bit different too. Cause as much damage to the Japanese as possible while minimizing their own losses. Resupply was almost non-existent. The Chinese air force was almost totally non-effective so one or two good firing passes be each fighter per raid was actually doing pretty good. No disrespect or minimizing the situation intended. The Flying Tigers (and their ground crews) did an amazing job in difficult circumstances. They were also, on average, very experienced pilots and trying to provide some sort of defense over the long haul. A few big battles might have seen them wiped out so a slow battle of attrition was more suited to their situation even if the people on the ground suffered.

Agreed completely.

But turn it around. Even with more fuel and lighting the P-40s by several hundred pounds, could the Flying Tigers have escorted a Chinese (if it existed) bomber force or allied bomber force hundreds of miles into Japanese air space successfully with the Japanese having 20-40 minutes warning they were coming?

The perspective opposition for the P-40 in the 1st half year after the Pearl would be the Nate and Oscar fighters. Nate would be a toast for the P-40 that is not at height disadvantage, and whose pilot does not want to engage in slow, turning fight. Nate is unable to withstand a burst from a P-40, unlike vice-versa.
Same things hold true for Oscar, though a speed difference is less pronounced here.
In case the Japanese have height advantage, the P-40 can dive and then zoom climb, the Japanese are ill able to follow the dive of it. The Japanese need to achieve full surprise if they're to succeec, and that also depends how a cooperative the P-40's drivers are.
Of course, if the Japanese are after P-40s, that means the bombers P-40s were escorting are free to do their job.
The early P-40 will exhaust maybe 1/3rd of it's internal fuel before entering the combat, so the weight would not be the problem.

 

[Shortround6]

You can't dive and zoom climb to gain more altitude than you had to begin with. That smacks of perpetual motion

The P-40s on defense could use speed and altitude to dive into/through the defenders and get to the bombers then could then use speed and/or dive to evade the defenders ( break the engagement) get out of range and then climb back up to altitude for another attack after catching the enemy formation while flying at the higher altitude. The climb back up is going to take a number of minutes.

On offence (bomber escort) you really can't use that tactic too well. While being tied too close to the bombers doesn't work well, speed alone doesn't give a lot of options. You can turn into the attackers for a head on pass. Just remember even a gentile (somewhat) 2 "G" turn will bleed off speed and a 2 "G" turn at high speed is going to be thousands of feet across. This is just to turn into an attack, not a circling dog fight. The tighter the turn the more speed that is bleed off. IF (repeat IF) the P-40 winds up with a Japanese fighter on it's tail it can dive and break away but if it does so it is out of the fight for a number of minutes. You don't loose the Japanese fighters by diving a few hundred feet. Take a look at even the P-40N charts again. Max climb is just under 2000fppm at 20,000ft and 1400fpm at 25,000ft. It takes 3 minutes to climb the 5,000ft using military power (plane won't give WEP at that altitude) and you wind up at 25,000ft doing about 190 mph, granted you can use the zoom climb to cut some of that time off but you will wind up at around 190 mph and climbing at 1400fpm near the end. It will now take you around 1 1/2 to 2 minutes to accelerate back up to max speed (flying straight and dead level) once you reach 25,000ft. Or use a shallower climb that gains high slower but allows for more horizontal speed.

The Japanese fighters, with a P-40 on their tail can try a quick turn ( they can turn tighter) and bleed of speed but watch the P-40 go by on the outside of the turn. The Japanese can try breaking up, turning and climbing. P-40 misses the shot, Japanese fighter winds up going slow but has altitude advantage and can dive to quickly regain speed while staying near the height of the bombers.

It's bit like the early P-47s. Certainly better than no escorts but many P-47s found themselves well below were the action was after the first engagement and would need a number of minutes to regain position.

If the P-40 has used 1/3 of it's internal fuel before combat it is in trouble. After combat allowance and a 30 minute reserve it has about 44 US gallons for the return trip. About 160-260 miles depending on cruising speed and the 260mile range is at a way to low air speed for safety.

 

[tomo pauk]

Expecting from an airplane to have all the cards is unrealistic, and a P-40 pitted against eg. CR.42 has some shortcomings. It's up to the commanders to order the pilots to play to own strengths, not to the enemy's. In this case, once in the airspace where enemy is expected to appear, the P-40s need to step up their cruising speed (using max continuous power now?), so their airplane is well into 300 mph range, and start essing so the bombers don't start to lag too much. Bombers should also step up their speed (B-25s were capable to cruise at 260 mph). That relegates Ki-27 (Nate) into a bay-stander, a lucky pilot might be able to hit something on head-on pass, but his luck my run out once it receives a bullet or two into fuel tank.
The Ki-43 I might also be in trouble if it does not have a favorable position and surprise is not achieved. It maxes out at 308 mph @13125 ft, barely faster than P-40B in fast cruise (307.5 mph were achieved with 725 HP at 15175 ft; 697 HP is max cruise, 930 HP is max continous; 335 mph was achieved on 910 HP used). So if the P-40s are flying at reasonable height (18-20000 ft) and speed (300-320 mph), the IJA fighters will be ill able to have their say about them.

The Japanese fighters that went after P-40s (though I'm not sure that would likely be the case, unless P-40's driver wants to give Japanese the chance) are not available to kill the bombers. Even in case they succeeded to drive away the escorts, will they be able to catch bombers? They have used maximum power to chase the escorts, they need to use lower setting now for 10-15 min, or the engines will overheat? Once they catch them, how good are their 7.7mm to kill them? The return fire is maybe greater than what they can fire.

The 160 US gals of internal fuel can enable good range, but I agree that it would took more to turn a P-40 into a better escort. The P-40C went for 187 gals, 52 gals being in drop tank.

 

[Shortround6]

Even the Mustang didn't hold all the cards, it just held enough or close enough that it had a number of options. The P-40 only held a few cards, the Ki 43 only held a few, but very different cards.

A P-40D/E used about 85 gallons an hour at just under 300mph at 15,000ft ( no need for 25-30,000ft cruises as the bombers don't have turbo chargers and don't fly as high as the B-17s.) I doubt the earlier ones burned much less.
But some of your escorts do need to fly in at least in the lower 20s to keep the formations from being bounced.

See : http://zenoswarbirdvideos.com/Images/P-40/P-40FOIC.pdf

The 28 gallons for warm up and take-off, climb to 5,000ft may be a bit excessive but may be part of the "reserve". it would be done (mostly) on internal fuel. the switch to the drop tank might take place at less than 5,000ft but NOT right after wheels up.
Of course you do have to form up your formations and rendezvous with the bombers.

See: http://zenoswarbirdvideos.com/Images/P-40/P-40TOCLC.pdf

Use the 8100lb line, about 40 gallons or a bit more for take-off and climb to 20,000ft ( in winter conditions, summer or tropics will need a bit more). An Allison could burn 135-140 gallons hour at the 1125hp military rating. and at Max continuous it burned 109 gal/hr for 1000hp at 2600rpm/ 39.2 in. Or about 38.5 gallons for 5 minutes at Military power and 15 minutes at max continuous for combat. It burned in the lower 30s for most economical flying so 16-18 gallons reserve for 30 minutes?

85-90 gallons used not included flying to target and back and 45 or more gallons after you drop the tank.

Basically even with the 52 gallon belly tank and 187 gallons total you have a 175 mile radius (at best). If you can fit a bit bigger belly tank it might help as you are going to burn close to 40% of the belly tank just climbing to altitude.

And again, the P-40s strengths (cards if you will) make it a better "interceptor" in spite of it's poor climb. It's high speed and good dive enable it to make high speed passes on the enemy escort fighters and break through to the bombers. It can't make many passes in one flight, however. This Strength doesn't work so well as an escort though.

 

[tomo pauk]

Even the Mustang didn't hold all the cards, it just held enough or close enough that it had a number of options. The P-40 only held a few cards, the Ki 43 only held a few, but very different cards.
And again, the P-40s strengths (cards if you will) make it a better "interceptor" in spite of it's poor climb. It's high speed and good dive enable it to make high speed passes on the enemy escort fighters and break through to the bombers. It can't make many passes in one flight, however. This Strength doesn't work so well as an escort though.

The things P-40 had as an interceptor vs. Ki-43 would imply that Ki-43 was not that a good interceptor itself. The level and dive speed were inferior than what P-40 had, the weak armament meant that more than one pass will be needed to actually kill a decent bomber, the return fire is likely to criple it in case it hits etc. In 1942, the Ki-43 was a slow fighter, compared with P-40. So we have a less-than-ideal escort vs. less than ideal interceptor. In case both are at cruise speed engine rating at 20000 ft, the P-40 is going 280-310 mph, the Ki-43 is at maybe 250 mph.
If the adversaries meet head-on, and Ki-43 plays it's strong card (climb maybe a thousand feet, so it can dive at P-40s), that means it's very likely it's about to loose the bombers. How well are the Ki-43s to coordinate it's attacks, since there was no radios aboard? (here, scroll down) The P-40s can help out each other, can the Ki-43, in a timely matter?

A P-40D/E used about 85 gallons an hour at just under 300mph at 15,000ft ( no need for 25-30,000ft cruises as the bombers don't have turbo chargers and don't fly as high as the B-17s.) I doubt the earlier ones burned much less.
But some of your escorts do need to fly in at least in the lower 20s to keep the formations from being bounced.

See : http://zenoswarbirdvideos.com/Images/P-40/P-40FOIC.pdf

The 28 gallons for warm up and take-off, climb to 5,000ft may be a bit excessive but may be part of the "reserve". it would be done (mostly) on internal fuel. the switch to the drop tank might take place at less than 5,000ft but NOT right after wheels up.
Of course you do have to form up your formations and rendezvous with the bombers.

See: http://zenoswarbirdvideos.com/Images/P-40/P-40TOCLC.pdf

Use the 8100lb line, about 40 gallons or a bit more for take-off and climb to 20,000ft ( in winter conditions, summer or tropics will need a bit more). An Allison could burn 135-140 gallons hour at the 1125hp military rating. and at Max continuous it burned 109 gal/hr for 1000hp at 2600rpm/ 39.2 in. Or about 38.5 gallons for 5 minutes at Military power and 15 minutes at max continuous for combat. It burned in the lower 30s for most economical flying so 16-18 gallons reserve for 30 minutes?

85-90 gallons used not included flying to target and back and 45 or more gallons after you drop the tank.

Basically even with the 52 gallon belly tank and 187 gallons total you have a 175 mile radius (at best). If you can fit a bit bigger belly tank it might help as you are going to burn close to 40% of the belly tank just climbing to altitude.

The V-1710-33 (for P-40C and earlier) have had 1040 HP at 13800 as mil power, using 115 gal per hour (9.6 gals for 5 min), max cont was 900 HP with 90 gals per hour (22.5 gals for 15 min) - for 20 min of combat, it would make 32.1 gals. Part of internal fuel was used for warm up, taxiing, take off and climb until drop tank can be engaged (P-40B was without a drop tank, of course) - 10 gals? So these two parts of flight will use some 42 gals. In the P-40C, that would leave the 'return home fuel' to 135-42=93 gals. Leave 17 gals for reserve (30 min), we're now at 93-17= 76 gals. At 75% of power (698 HP, making 306 mph at 15000 ft), the P-40B will consume 59 gals/hr, the really good mileage can be achieved with 202 mph, only 24 gals/hr. Of course, the further we're of friendly airspace, the higher speed need to be used; not too fast, that would mean bombers are left without defense. here and here
The 52 gals in drop tank can give maybe 1 hour at 67% of rated power, giving some 200-250 miles of ingress range? Again, a 75 gal tank will be of better use.

 

[nuuumannn]

But certainly in 1940-41 it [the Mitsubishi Zero] was the most effective long-range escort of its time taking the allies by nearly total surprise and who were only able to respond with obsolescent inadequately performing interceptors unable to counter its attacks.

I agree. In the timeframe we are discussing there was no better suited alternative that existed without extensive modification. Not the P-40B, not the Spitfire, not any other fighter. The Zero had the range in spades, its performance was sufficient to take on any existing fighter at the time and come off on top (depending on pilot experience - of course). As for its so-called structural weakness, I think we make more of this than as it actually served as a 'weakness' at the time. The Zero was a carrier based fighter; it had structural strength enough to withstand the rigours of sustained carrier operations - I know of no instance where the Zero's structure failed as a result of conventional carrier operations (although please correct me if there is such an example), so just because it displays a tendency to fall apart when struck by enemy gunfire doesn't constitute a weakness in combat. This is not how the Japanese saw this aeroplane; to them it was a master stroke of design and that structure we criticise enabled that aeroplane to be as good as it was, and let's face it, there was no better aircraft carrier fighter or land based fighter that the Zero was going to encounter that it could not defeat, not until the appearance of later aircraft outside of the scope of this discussion.

It was tactics, training and better awareness of the aircraft's strengths and wweaknesses that led to the erosion of its superiority (as opposed to its perceived invincibility) and this took time. It didn't happen overnight. We tend to dismiss the Zero because of the performance of fighters such as the F4U and F6F, but remember that these aircraft are of a different generation to the Zero with bigger, more powerful engines and different design philosophies. But it was supreme in the first year of the Pacific war in terms of pound for pound performance and capability and it carried out astonishing feats of endurance that Western fighters could not match, because of their design philosophies.

 

[tomo pauk]

Fine post there.
I've looked a bit at fuel tanks data of the P-40B and -C. Here are capacities in US gallons, B and C:
-front wing: 40 vs. 34
-rear wing:61 vs. 52
-fuselage: 57 vs. 50

Total 158 vs. 136; the 52 gal tank ups the total fuel for the -C at 188 US gals.

The Zero's ranges need to be put into a context. 1st, the altitude - the 1500 ft. Second - the speed - 152 mph (clean, 156 US gal ) or 147 (with 87 US gal drop tank attached; 243 gals total). In other words, not a flight regime one wight want to excercise over, say, German-held Europe, but certainly fine for many parts of Pacific/Asia. Ranges being 1130 or 1640 miles (with DT); mileages 7.7 or 6.75 mpg. Combat range, with drop tank, 476 miles, under conditions unknown to me. here Question to the knowledgeable - how good the Zero was when cruising at 15000 ft?
Let's see how P-40B fares: on 202 mph and at 15000 ft - between 805 and 1010 miles with 120 US gals aboard. Mileage 8.4 or 6.7 mpg. here Fill it full (+38 gals) and it will go some 30% further - 1050 to 1300 miles. Should beat the clean Zero, at least those that are not killed by light AAA The P-40C with 75 gal DT could equal the range of Zero that has drop tank attached?

 

[tomo pauk]

Doh
What have I did wrong, Steve?

 

[Shortround6]

A few things the Zero had going for it were the light weight armament (heavier than a Ki 43s but lighter than an early P-40) and the Sakae engine which was able to run for long periods of time at extremely lean conditions, some sources say 190 grams fuel per hp.hour. One source says 160 grams but that is really far from from the norm.
Against it are the lack of protection and the light construction. Adding protection to western standards might have added 200 (unlikely) to 400lbs ( more likely?). While we don't have reports of the Zero breaking while operating from carriers we do know it had a restricted diving speed (improved in later models) due to strength (early Hurricanes had a restricted dive speed). The controls becoming heavier at high speed may have prevented the pilots from over stressing the airframe too.

While adding 300-500lbs might have only cost 3-8mph (?) the loss of climb performance would have hurt much more.
later Zeros with more powerful engines had very modest increases in performance (at times lost performance) due to increased weight and drag caused by increased protection and armament.

 

[nuuumannn]

Thanks for the like Tomo

The Zero's ranges need to be put into a context. 1st, the altitude - the 1500 ft. Second - the speed - 152 mph (clean, 156 US gal ) or 147 (with 87 US gal drop tank attached; 243 gals total). In other words, not a flight regime one wight want to excercise over, say, German-held Europe, but certainly fine for many parts of Pacific/Asia.

SR makes a good point about the Sakae engine; it was very reliable, not only that, but if the Zero was your only option over Germany, then you'd send it. In hindsight it is easy to state that "we wouldn't want to send that aeroplane over there; it'd get shot to pieces...", but the RAF was sending bombers into German territory from the day the war began until its very end, on the whole without escort and most, to begin with were terribly vulnerable and were butchered as a result. Whatever the Brits had to do the job they wanted, they'd use.

Having given this a bit more thought, I still believe, despite protestations to the contrary that the British firms would have developed aircraft based on existing designs for their long range fighter, although it is highly likely that a similar path to what was developed to F.18/37 - a Spitfire/Hurricane replacement, would have been developed. Supermarine tendered the twin engined Type 324 and derivatives, up to the Type 327 that Wuzak mentioned earlier, Boulton Paul would have developed yet another Defiant derivative, as they did with so many of their entries to official requirements and Hawker might have pursued a Tornado/Typhoon derivative.

Against it are the lack of protection and the light construction. Adding protection to western standards might have added 200 (unlikely) to 400lbs ( more likely?). While we don't have reports of the Zero breaking while operating from carriers we do know it had a restricted diving speed (improved in later models) due to strength (early Hurricanes had a restricted dive speed). The controls becoming heavier at high speed may have prevented the pilots from over stressing the airframe too.

I once spoke to a fella (warbird pilot) who had flown one of the Zeroes in the States, also a F6F and F8F as well as other types including a P-51; he commented about these aspects of the Zero; it was by far the slowest fighter of all, but in fairness it had less powerful engines than these machines; the Zero was a pre war design (in my assessment equivalent in philosophy to the Hurricane as a bridge between old ideas and new), but he also commented on its dive speed, not because of structural weakness, but because it just would not go any faster. He did, however state that there was nothing that could outmanoeuvre it, possibly the F8F, although the Zero was much slower and as a result this was the biggest limitation on it. Structural strength was never, if I can recall (waiting for confirmation of examples of this) an issue encountered by the Japanese. The Zero's structure was not 'weak'; it was light, but strong enough for the rigours of day-to-day operations - there is a difference.

 

[Shortround6]

The American Navy had a requirement during the 30s (if not before) that it's aircraft had to perform a "terminal velocity dive". That is a vertical dive from a high enough altitude that a speed was reached at which the aircraft could NOT go any faster, Thrust and gravity equaled drag. This was a good test for biplanes and some early (high drag) monoplanes that enough drag to keep them from going so fast they got into trouble. They did break a few planes doing this and this was usually one of the last tests done ( if not the last) before acceptance. In some cases a special test pilot was hired for this test. The Brewster Buffalo and Grumman Wildcat may have been the last fighters "designed" for this test as speeds were getting high enough to introduce new problems unrelated to the strength of the aircraft, like compressability and mach tuck. Plus the Altitude needed for pull out was starting to get rather large. I could be wrong but I think the F4U Corsair was the first Navy fighter NOT required to pass this test.

Like the Hurricane ( which limited it's dive speed or VNE) that changed with the fitting of the metal covered wings, the Zero had it's VNE speed changed at least once, if not twice from the originals "limit" has heavier wing skinning was used and/or other changes made. This does not mean the Zero could dive like a late model American plane, just that it could dive at a faster speed than an early Zero, it might not have gained speed much faster.

Now one of our members who is an engineer may correct me if I am wrong but the forces acting on the wing go up with the square of the speed so a 10% increase in speed results in 21% for force acting on the wing and a 20% increase in speed results in 44% more force. going from 400mph to 450mph increases the forces acting plane/wing by 26.5% ANd that doesn't count things like local airflow separation causing disrupted airflow and introducing flutter or other problems.
If the Zero was flown within it's limits there was no problem, exceed them and ????

To be fair a number of Mustangs were reputed to have been "bent" with the coming of the American "G" suit which allowed the pilot to withstand more "G"s than the airplane could. Planes were claimed to be landing with several more degrees of dihedral than they took off with. I don't know if this is true or just a tall tale, but Mustangs were not noted as being "flimsy". Exceed design limits and you are in trouble in any airplane.

I would note that a model 21 Zero was only a few hundred pounds (300?) lighter, both empty and normal gross (no drop tank)than the Spitfire prototype and while that might not be quite fair comparing service plane to prototype it shows that the Zero was not quite the "light weight" it is often portrayed as.

 

[tomo pauk]

Looking at the document posted before (and here), the Ki-61 is a champion of the single engined fighters - more than 2000 miles @1500 ft with full internal fuel and 100 gals in drop tanks (299 US gals total), combat radius of 640 miles. The combat radius figures stated at that document are probable much closer to the USN requirements (involving lower altitude and speed) than USAF requirements (P-51D combat radius was 450 miles at 10000 ft altitude, on just internal 269 gals).

Now if only Mike Williams might find and post the document(s) connected with that table...

 

[Shortround6]

I would hazard a guess that much of the performance figures range from tests of captured aircraft to estimates based on limited testing to "WAGS"

Under remarks for the Frank we see that the dimensions let alone the performance are "subject to revision" and for the Jack "may be operational".

The Ki 61 was a low drag airplane (compared to some), it was lighter than some and it used a higher aspect wing ratio than most other fighters which helps efficiency (unknown if some other aspect of the plane cancels out the wing advantage).

However near miraculous range must be viewed with suspicion.

then compare the weight of armament for the Ki 61 to the possible weights of armament for other nations fighters. The Japanese Ho-103 gun weighing 6kg less than the American .50 cal per gun and it's ammo was enough lighter that 250 rounds (without links) weighs about what 183 rounds of US .50 cal weighs. the 6kg difference in gun weight is worth another 53 rounds of .50 cal ammo (without links) First Ki 61s had about 1/2 the weight in wing guns/ammo compared to a P-40B/C.

 

[nuuumannn]

while that might not be quite fair comparing service plane to prototype it shows that the Zero was not quite the "light weight" it is often portrayed as.

More evidence if needed that the Zero was not structurally weak. Granted it could not withstand as much punishment as your average Grumman built fighter (there weren't many that could!), but bursting apart after attack is not necessarily a sign of structural weakness. Regardless, although roughly the same size, the Zero being shorter by a few inches with a bigger wingspan than the early Spitfires (I to V) the Zero was generally speaking lighter than the Spitfire and yes; it seems a bit pointless to compare the Spit prototype with a production aircraft, why not choose a Spit I or II? Loaded weight (as opposed to MTOW) of an A6M2 Model 21 was (according to Japanese Aircraft of the Pacific War by Rene Francillon) 5,313 lbs compared to the Spit I's 5,784 lbs or the Spit II's 6,527 lbs. Compare with the Grumman F4F-4 at 6,100 lbs.

Regarding the Zero's diving speed the chappie I talked to, can't remember his name explained that the Zero redlined (VNE) at 300 kts, but he had never got the aircraft to that speed; in a dive, like you stated, SR, its controls became too heavy, but he could not get it to fly any faster than about 270 - 280, if I can remember. Saburo Sakai confirms these speeds in his book Samurai. This book also gives ample evidence that the Zero could and frequently did withstand a considerable amount of punishment without flying to pieces. Sakai recounts on one combat op that he and his colleagues returned with their aircraft riddled with .50 cal bullet holes.

the Ki-61 is a champion of the single engined fighters - more than 2000 miles @1500 ft with full internal fuel and 100 gals in drop tanks (299 US gals total), combat radius of 640 miles.

That's pretty impressive in anyone's books. Here's a passage from Samurai, where Sakai discusses the Zero's range and how the pilots learned to extend it:

"Clark Field was 450 miles away from our own air base and Nichols Field... ...was 500 miles distant from Tainan. That meant, considering the factors of still air range, fuel for fighting and fuel for reserv, that we would be required to fly nonstop for some 1,000 to 1,200 miles! No fighters had ever flown on such combat missions before, and there were vehement arguments among the air staff as to whether the Zero was capable of this performance."

"From then on we flew literally day and night to stretch the range of our planes. Apart from its range, the Zero was designed to remain in the air on a single flight for a maximum of six or seven hours. We stretched this figure to from ten to twelve hours and did so on mass formation flights. I personally established the record low consumption of less than seventeen gallons per hour; on the average our pilots reduced their consumption from thirty five gallons per hour to only eighteen. The Zero carried a normal fuel load of some 182 gallons."

"To conserve fuel we cruised at only 115 kts at 12,000 ft altitude. Under normal full power conditions the Zero was capable of 275 kts and when overboosted for short emergencies, could reach its maximum speed of about 300 kts. On our long-range flights we lowered propeller revolutions to only 1,700 to 1,850 rpm and throttled the air control valve to its leanest mixture. This furnished us the absolute minimum of power and speed and we hung on the fringe of losing engine power at any time and stalling."

 

[tomo pauk]

WAGS - wives and girlfriends?

Under remarks for the Frank we see that the dimensions let alone the performance are "subject to revision" and for the Jack "may be operational".

That would point out that document is a result of data available at early 1945?

The Ki 61 was a low drag airplane (compared to some), it was lighter than some and it used a higher aspect wing ratio than most other fighters which helps efficiency (unknown if some other aspect of the plane cancels out the wing advantage).

However near miraculous range must be viewed with suspicion.

Don't know. With drop tank, it featured twice as much fuel as a clean Zero, and it was surely a less draggy plane than Zero. The range was achieved on 1500 ft altitude (supercharger uses just a tad of power to turn?), the speed was 148 mph - all the ingredients for the superb range are here. OTOH, the P-51D was flying at 10000 at 210 mph IAS - that would mean 250 mph TAS, and supercharger is using more power there than at 1500 ft. The P-51D was using 59 gals per hour when flying 260 mph TAS at 10kft (range of 1500 miles on 269 gals - all internal), and, for same range on same fuel, it was using 39 gals per hour when flying at sea level at 220 mph.

Sure thing that other countries have had slightly lighter weaponry with no loss in firepower. The 8-LMG P-40s, anybody?