MONSTER essay-post time. Buckle your seatbelts...
It's been said before, but speed
is maneuverability. Or, to give a fuller definition,
both speed and maneuverability are critical parts of positioning your aircraft into a killing position, and out of a position where it can be killed.
The Zero wasn't
solely designed for its low-speed turn performance, despite reputation: the entire aircraft was designed to be, for its time, a very fast and rapid climbing carrier fighter. It was generally accepted at the time that Carrier based fighters would be inferior to their land-based counterparts by a significant margin, for a number of reasons:
- Carrier aircraft must be designed with stronger, heavier landing gear than land-based aircraft, due to needing to touchdown at higher speeds to make a short landing (there's a half-joke still that the easiest way to tell what service an airline pilot flew in is to observe their landings). This adds extra weight to the design, robbing rate of climb
- Carrier aircraft must have a lower minimum control speed (that is, the lowest speed that a pilot still has reasonable authority over roll, pitch, and yaw) than land-based counterparts.
- Carrier aircraft must be able to fit on the carrier's elevator if they are to be stored below deck. This either limits maximum dimensions, forces additional weight and complexity due to folding mechanisms, or both
Consider that before the Brewster Buffalo and Wildcat, the primary US Carrier Fighter was the F3F, a Retractable gear Biplane: while Biplanes had inferior speed and range due to drag, their wings could be made shorter while still giving enough lift for a short takeoff run.
The Zero was an attempt to build a Carrier fighter that was an equal to, if not superior to, land-based fighters of its time. And to achieve this while still being acceptable for Carrier Operation, they needed to do several things:
- Empty weight needed to be kept to a minimum: with increasing aircraft weight, with other factors controlled, the following occurs:
- takeoff and landing distance increases
- rate of climb is reduced.
- The amount of lift needed to maintain a turn of a given "tightness" increases (try looking up "Load Factor" for more information)
- Internal fuel storage needed to be sufficient for long range operation, as the Zero would need to fight over the largest battlefield on earth. Running out of fuel over the Pacific Ocean could be a death sentence.
- The engine needed to be powerful engine to give good speed and climb, but light enough to not adversely affect weight, and efficient enough to not adversely affect range
- The Japanese Navy, having just started conflict with China, who was primarily using obsolete biplanes, anticipated a need for excellent control at low speeds, while still being fast enough to engage more modern aircraft.
here's a direct clip from the bane of all teachers, Wikipedia:
"Based on the experiences of the A5M in China, the IJN sent out updated requirements in October, calling for a speed of 270 kn (310 mph; 500 km/h) at 4,000 m (13,000 ft) and a climb to 3,000 m (9,800 ft) in 9.5 minutes. With
drop tanks, the Navy wanted an endurance of two hours at normal power, or six to eight hours at economical cruising speed. Armament was to consist of two 20 mm
cannons, two 7.7 mm (.303 in)
machine guns and two 60 kg (130 lb)
bombs. A complete radio set was to be mounted in all aircraft, along with a
radio direction finder for long-range navigation.
[8] The maneuverability was to be at least equal to that of the A5M, while the wingspan had to be less than 12 m (39 ft) to allow for use on aircraft carriers."
To meet these requirements, the designers took advantage of the following:
- The Zero used a newly developed ESD, or "Extra Special Duralumin" alloy for the airframe. This was noticeably lighter for comparable strength when compared to previously used alloys, and that meant the airframe of the Zero could be built lighter for a given load
- The Zero's wing was built as a single component, rather than 2 wings mated together. This made construction more difficult, but it also further improved strength to weight ratio
- The Zero's wingtips could be folded in to allow the plane to fit on Carrier Elevators. This was a compromise between the desire for a longer wing, the need to conform to the requirements of existing vessels, and the previously mentioned need for a strong wing
- Originally, Mitsubishi's own Zuisei engine was used, but this was swapped to Nakajima's competing Sakae engine for production. Both engines were incredibly light for the power they offered (by the standards of pre WW2, at least), only around 1,200lbs, while offering nearly 1,000hp in emergencies.
The end result was highly formidable, and I don't think I need to go over the details too heavily. That said, I WILL make note of something people often forget: Prior to 1943, the only other
true Carrier fighters ready for combat were the Brewster Buffalo, and the F4F Wildcat. The Sea Hurricane and Sea Spitfire were good performers, but neither was really suitable as a
carrier aircraft. The Seafire in particular suffered immensely due to its narrow undercarriage not being sufficiently strengthened for the high sink rates of deck landing. And Brewster had so many mismanagements at its company that it was accused of
sabotage, so I think for now, we should really only compare the A6M2 and the F4F-3 and -4:
- The Zero and both Wildcats are about equal in maximum level flight airspeed. I don't have details on speed vs altitude, but the differences are small enough to be ignored for this very broad discussion
- The Zero (empty weight roughly 1750kg, or 3,900lbs) is far lighter than both the F4F-3 (empty weight around 4,900lbs), and the F4F-4 (around 5,900lbs). In combat, all of these aircraft will be significantly heavier, due to the massive weight of fuel, but the Zero still comes out around 1,000lbs lighter.
- The Wildcats have more engine power at almost all altitudes, thanks to using a 2-stage, 2-speed system (this is where some small part of the weight of the Wildcat comes from). This advantage is greatest at altitudes above 16,000ft. However, this altitude band is somewhat less important in the Pacific Theater, where combat generally ranges from Sea Level to 15,000ft, rarely exceeding 20,000ft. Below 10,000ft, the Wildcat still has more power, but not by as much.
- Since the Zero is roughly as fast as the Wildcats despite having slightly less engine power, the Zero must have slightly lower parasite drag.
- Because of the lower weight, lower induced drag, and slightly lower parasite drag, the Zero has a greater maximum rate of climb (raw vertical speed, using measured ft/min), and a steeper maximum angle of climb (The steepest angle that the aircraft can maintain a climb at without losing speed, degrees from horizontal). These also translate to better overall acceleration. As such, the Zero will tend to gain both altitude and airspeed much faster than the Wildcat.
- The Zero has a slightly lower stall speed than the Wildcat. Not by quite as much as people would expect, but combined with the superior acceleration, it becomes clear why a US pilot would be told to "never dogfight a Zero": a fight below 200mph Indicated Airspeed (essentially how fast the plane "feels" like it's flying, since thin air gives less lift and drag) would blatantly favor the Zero.
- Above 190mph Indicated Airspeed, the Zero's ailerons would begin to stiffen, making it difficult to perform rolling maneuvers at high speeds. Servo tabs were installed later on to address this, but they were quickly removed when it became clear that this would overstress the aircraft. The other controls also stiffen at high speeds, although not to the same degree. Meanwhile, the Wildcat maintains relatively good authority at these speeds, meaning that above 200mph, the Wildcat can potentially outroll the Zero, and at even higher speeds, it can even pull tighter turns.
- Due to the low-speed lift design of the Zero, it suffers from a low maximum safe diving speed of 390mph Indicated. The Wildcats, meanwhile, can handle dives approaching 550mph, which even some late war fighters aren't capable of.
- The F4F-4 (Not the -3), was able to fold almost the entirety of its wings to the sides (yet another source of weight), which meant significantly more of them could be stored inside of a Carrier. This sounds like a small feature when looking at the "trading card" stats, but don't underestimate the power of being able to bring 50% more fighter cover to a carrier battle.
- Despite popular belief, the F4F-3 did not carry armor and self-sealing fuel tanks. These were added to the -4 model, which was the primary variant flying from the Battle of Midway onwards. The Wildcat was still more resistant to battle damage in many cases than the Zero, however: many systems of the F4F were so redundant and idiot proof, you could almost build a second plane out of them.
- While I'm struggling to find the specific sources for it right now, the Wildcat, iirc, had all trim tabs adjustable by the pilot in flight. This meant that he could simply dial the tabs to the desired setting when in cruise to let aerodynamic forces hold the control surfaces at the desired placement, making it much easier to maintain formation. The Zero's aileron trim tabs could only be adjusted on the ground.
- The F4F-3 had four wing mounted Browning Machine Guns, firing 12.7x99 ammunition. These guns were somewhat heavy for their caliber and rate of fire, but boasted high muzzle velocity, as well as retention of velocity over distance. They could also carry up to 400 rounds a gun, giving more than half a minute of combined firing time. The -4 model carried six of these guns, but due to the extra weight, along with the rounds per gun dropping to only 270 (enough for about 20 seconds of constant fire), this gun setup was unpopular with US pilots. Many -4 Wildcats were modified back to the four-gun setup
- The Zero, as mentioned in the IJN requirements, had twin 20mm cannons in the wings, and twin rifle calibers firing synchronized through the cowling. On paper, the high explosive rounds of the zero seem to place its damage above the Wildcats, but in practice, the combination of low ammunition count (60 rounds a cannon, only enough for 7 seconds on the trigger) and low muzzle velocity (around 2/3 that of the Browning) meant that it was far from uncommon for a Zero pilot to have to take on a Wildcat using only the Rifle calibers.
What all of this meant is that an F4F pilot could successfully engage a Zero IF he refused to engage in combat below 200mph IAS (Indicated Airspeed). Below this, the Zero had almost every advantage, but it couldn't really
force the fight to slow down if the Wildcat refused to do so. This is also where we finally get into what we call "Boom and Zoom" tactics, which are valuable in any situation, but are most noticeable here. If a group of Wildcats dived on a group of Zeroes at high speed, opened fire, and then use that speed to make a shallow climb back to high altitudes (or used it to continue in a very high speed dive), the Zeroes could not accelerate quickly enough to catch up and shoot them down. The Japanese used these same tactics earlier in the war, as well as over China, so it's not as if the tactic was born out of pure desperation.
We know
now that the Japanese overestimated the importance of low-speed control compared to high-speed control, but they weren't blind to the importance of other factors as well. It's merely that Air Combat is about positioning in a 3D space, and turn radius is just one part of that.