Maneuverability vs Speed

[JoblinTheGoblin]

If maneuverable fighters like the A6M Zero are considered to have been such capable fighters, if not the best in the world relative to contemporary fighters, why was it then that every single major power, including Japan itself, were committed to the development of increasingly faster and more powerful aircraft. Were improved anti-air defenses a factor in this? Escort role—keeping up with bombers? Why not increasingly larger wing areas (to a point, of course), along with other additions that could increase maneuverability? Was armor, and the survival rate of pilots in general, a large factor in any of this?

 

[PAT303]

The A6M was effective because it had speed climb and maneuverability advantages against early fighters such as the wildcat P40 P39, against higher performing aircraft such as the Spitfire Corsair Hellcat all the pilots had to do was not be lured into a slow speed turning fight but instead turn speed into energy and stay on the offensive. In a fight you can't keep turning, you need power to climb and speed to gain an advantage to attack on your terms, you also need speed to catch an opponent and likewise speed to get the hell out of Dodge if things don't go your way.

 

[rednev]

The important thing in aeroplanes is that they shall be speedy.

Manfred von Richthofen

 

[NTGray]

Remember that the Zero, which was considered in 1942 to be an amazing plane that outclassed its "inferior" opponents, did not actually do all that well in the real world. The Zero was always a "one trick pony" that had extraordinary maneuverability, but little else (except range, which didn't matter during actual combat). Even though our American pilots were initially impressed by the Zero's aerobatic capabilities, they did figure out ways to shoot it down, and those ways leaned heavily on teamwork, training, and the Wildcat's superior speed in a dive. Those "inferior" Wildcats actually gave better than they got, and the ratio became more and more in favor of the Wildcat with the passage of time, approaching 6:1 toward the end of the Guadalcanal campaign.

 

[pbehn]

If your opponent is much faster you have to shoot him down to escape, he can go home anytime he likes.

 

[Greg Boeser]

If your opponent is much faster you have to shoot him down to escape, he can go home anytime he likes.

Which brings up a third dimension of combat - endurance.
If I have more fuel, I can outlast my opponent, even if I can't outrun him.

 

[Thumpalumpacus]

Speed can allow the canny pilot to dictate the terms of engagement. Maneuverability only comes into play once the combat is entered.

A maneuverable airplane may give trouble to a fast airplane in-close, but the pilot of a speedy airplane can decide to engage or disengage. It follows that speed allows a pilot to enter or reject combat as circumstances fit. Tactics, tactics, and tactics. BnZ evolved for a reason.

 

[KAKI3152]

If the A6M zero had changed the engine to the 1,900 hp Ha-45, it would have been an awesome fighter. With this much power, the top speed would have been in 400+MPH, additional armor could have been fitted, and some heavier armament, making the A6M a truly dangerous opponent.

 

[Greg Boeser]

If the A6M zero had changed the engine to the 1,900 hp Ha-45, it would have been an awesome fighter. With this much power, the top speed would have been in 400+MPH, additional armor could have been fitted, and some heavier armament, making the A6M a truly dangerous opponent.

How much structural strengthening would that require and how would the extra weight affect performance?

 

[Greyman]

A big part of the Zero's problem vs. later Allied aircraft wasn't just the speed, but the maneuverability at speed. Above 250-300 mph it was at a distinct disadvantage.

Without a drastic redesign, more power would just exacerbate this problem. Best to do what Mitsubishi actually did and focus on a new fighter.

 

[Thumpalumpacus]

Without a drastic redesign, more power would just exacerbate this problem. Best to do what Mitsubishi actually did and focus on a new fighter.

Would reducing aileron size have helped the hypothetical newer, higher-powered model? My understanding is that the A6M's poor control-response at high speed was due to the large control surfaces. Am I misunderstanding something?

 

[PAT303]

Would reducing aileron size have helped the hypothetical newer, higher-powered model? My understanding is that the A6M's poor control-response at high speed was due to the large control surfaces. Am I misunderstanding something?

All fighters had control problems as speeds got higher, both the Spit and 109 suffered from it during the BoB as pilots pushed their planes to the limit.

 

[ThomasP]

Hey Thumpalumpacus,

Reducing the aileron area would help at high speeds to a degree (how much I do not know) as would modifying the mechanism. At the very least it would allow greater roll rates at higher speeds, but it would also reduce the roll rates at slower speeds. The A6M3 (with clipped wings and smaller ailerons) was supposed to have reasonable roll control upto about 350 mph, and could still roll slowly at VNE.

Fitting a 1900 BHP engine (if practical) would allow a significant increase in speed, though how much would be dependent on what altitude the new engine could produce that horsepower at. If the new engine produced that kind of HP at 13,780 ft (the rated altitude of the original Sakei 12 at 950 BHP) or higher, then you are correct the A6MX could reach ~400 mph+ (at an altitude above ~17,000 ft with RAM?), assuming no significant increase in drag. Not sure what the Mach effects would be at that speed.

Another significant increase in performance would be in climb. With that much excess power the ROC would go up to ~5000 ft/min (I think) assuming a climb power of 1500 BHP (~80% of 1900 BHP). Operational ceiling (ROC of 500 ft/min) would be over 40,000 ft?

Excess power to that level would also allow the A6MX to out turn (sustained) any propjob that saw combat during the war, at speeds upto about 350 mph (I think). This is all assuming a weight increase of ~500 lbs over the A6M2's TOGW of about 5550 lbs with full DT. At 6050 lbs TOGW the wing loading of the A6MX would be about the same as the early Spitfire and Hurricane at ~25 lbs/ft2. Using the A6M3's wing the A6MX's wing loading would go up a bit more, but it would still be relatively low compared to pretty much all the mid- to late-war Allied fighters. Obviously, if you add armour and SSFT the empty weight would increase even more, but if you use the A6MX as an interceptor and local area fighter (ie don't worry about the very long range capability) you could limit the TOGWmax and/or maneuver weight by not putting as much fuel in the plane - say 120 USgal internal instead of the original 141 USgal, plus the 87 USgal DT? Or take-off with full internal fuel but no DT (592 lbs with fuel)? Only straight flying and gentle maneuvers until the DT is empty or dropped?

As mentioned above by Greg Boeser the airframe would have to be strengthened significantly to handle the increased bending and torsional forces. And I doubt anything less than a 5-blade propeller of the same diameter could absorb the increased power. In the WWII period the maximum effective HP that the props could absorb was in the 5-6 BHP per blade per ft2 of the propeller disc. So if you keep the same Ø9' 6" for the propeller, you would end up with ~5.36 BHP/blade-ft2 for a 5-blade prop, which is a reasonable prop disc load. With a 4-blade prop you end up with ~6.7 HP/blade-ft2 - maybe a German 4-blade broad chord type prop could absorb that?

NOTE: The reason I used a basic increase of 500 lbs for the TOGW is that that is what occurred when the Spitfire jumped from the Merlin powered Mk V to the Griffon powered Mk XII. I realize this weight increase may be a significant underestimate, but I figure it is a good starting point.

[edited]

 

[Shortround6]

As ThomasP has written, there are number of problems with making planes go faster with larger engines. The Zero was harder than most as it was so well tailored to it's original speed regime. The Zero got wing strengthening at least twice in it's history and still had one of the lowest do not exceed speeds of any fighter of WW II.
Please note that the Zero lost a fair bit of maneuverability as it got older. This gets overlooked because it was so maneuverable to begin with. That and it could still out maneuver the American planes, just not by as much.
The Homare was just about 500lbs heavier than the two speed Sakae
The two speed Sakae engines got a 10 ft prop. Most of the Zeros after 1942 had shorter wings. You had 3 wings (?) on the Zero. The original long span round tip, The Clip wing Hamp (A6M3) and the short round wing A6M5s, They put a round tip on just about the same wingspan as the Hamp, they did not restore the full span. There were also changes to the ailerons.
The A6M7 (dive bomber) got reinforced tail surface/s to help handle the loads.
The A6M5c was about 600lbs heavier than the A6M5 and it had reduced sized fuel tanks and even a slightly smaller drop tank.

 

[Thumpalumpacus]

All fighters had control problems as speeds got higher, both the Spit and 109 suffered from it during the BoB as pilots pushed their planes to the limit.

The Zero's controls got incredibly heavy above 300 mph. Alternatively, the Wildcat would dive away from Zeros, knowing that it wouldn't have a useful roll-rate at high speed.

 

[Reluctant Poster]

Hey Thumpalumpacus,

Reducing the aileron area would help at high speeds to a degree (how much I do not know) as would modifying the mechanism. At the very least it would allow greater roll rates at higher speeds, but it would also reduce the roll rates at slower speeds. The A6M3 (with clipped wings and smaller ailerons) was supposed to have reasonable roll control upto about 350 mph, and could still roll slowly at VNE.

Fitting a 1900 BHP engine (if practical) would allow a significant increase in speed, though how much would be dependent on what altitude the new engine could produce that horsepower at. If the new engine produced that kind of HP at 13,780 ft (the rated altitude of the original Sakei 12 at 950 BHP) or higher, then you are correct the A6MX could reach ~400 mph+ (at an altitude above ~17,000 ft with RAM?), assuming no significant increase in drag. Not sure what the Mach effects would be at that speed.

Another significant increase in performance would be in climb. With that much excess power the ROC would go up to ~5000 ft/min (I think) assuming a climb power of 1500 BHP (~80% of 1900 BHP). Operational ceiling (ROC of 500 ft/min) would be over 40,000 ft?

Excess power to that level would also allow the A6MX to out turn (sustained) any propjob that saw combat during the war, at speeds upto about 350 mph (I think). This is all assuming a weight increase of ~500 lbs over the A6M2's TOGW of about 5550 lbs with full DT. At 6050 lbs TOGW the wing loading of the A6MX would be about the same as the early Spitfire and Hurricane at ~25 lbs/ft2. Using the A6M3's wing the A6MX's wing loading would go up a bit more, but it would still be relatively low compared to pretty much all the mid- to late-war Allied fighters. Obviously, if you add armour and SSFT the empty weight would increase even more, but if you use the A6MX as an interceptor and local area fighter (ie don't worry about the very long range capability) you could limit the TOGWmax and/or maneuver weight by not putting as much fuel in the plane - say 120 USgal internal instead of the original 141 USgal, plus the 87 USgal DT? Or take-off with full internal fuel but no DT (592 lbs with fuel)? Only straight flying and gentle maneuvers until the DT is empty or dropped?

As mentioned above by Greg Boeser the airframe would have to be strengthened significantly to handle the increased bending and torsional forces. And I doubt anything less than a 5-blade propeller of the same diameter could absorb the increased power. In the WWII period the maximum effective HP that the props could absorb was in the 5-6 BHP per blade per ft2 of the propeller disc. So if you keep the same Ø9' 6" for the propeller, you would end up with ~5.36 BHP/blade-ft2 for a 5-blade prop, which is a reasonable prop disc load. With a 4-blade prop you end up with ~6.7 HP/blade-ft2 - maybe a German 4-blade broad chord type prop could absorb that?

NOTE: The reason I used a basic increase of 500 lbs for the TOGW is that that is what occurred when the Spitfire jumped from the Merlin powered Mk V to the Griffon powered Mk VIII/XII. I realize this weight increase may be a significant underestimate, but I figure it is a good starting point.

The MkVIII was not Griffon powered it had the 2 stage Merlin. The XII had the 1 stage Griffon. The XII actually weighed less than the VIII.

 

[ThomasP]

Ooops! Thank you for the correction Reluctant Poster. I have corrected my post to Spitfire Mk IX and Mk XII.

 

[Reluctant Poster]

Ooops! Thank you for the correction Reluctant Poster. I have corrected my post to Spitfire Mk IX and Mk XII.

Sorry but it is still incorrect. The Mk VIII and IX weighted the the same, about 600 lb more the the single stage Merlin powered Mk V. The single stage Griffon powered XII weighed about 100 Lb less than the VIII or IX. The 2 stage Griffon powered MkXIV weighted about
700 lb more than the 2 stage Merlin powered VIII and IX.

 

[ThomasP]

Ooops again. (It is 0810 in the morning here and I have not gone to bed yet.)

Okay, edited it again and changed it to Spitfire Mk V and Mk XII?

 

[Reluctant Poster]

Ooops again. (It is 0810 in the morning here and I have not gone to bed yet.)

Okay, edited it again and changed it to Spitfire Mk V and Mk XII?

That works