Some finds about the A6M and N1K1/2 Series

It would be a little bit of an overstatement if I said I found the source of the A6M's problem, but I think that I may have discovered one of the errors which contributes to the undermodeling of the A6M series.

Back when FH Version 1.60 was released, rgreat posted the usual thread about the changes to the FH software.

In this thread rgreat informed the community that the following change had been made to the software:

Through my research I have several times come across sources which stated that the A6M did indeed have a central fuel tank immediately in front of the cockpit.

What I have a problem with is the fact that the A6M already had a central fuel tank before this change was made.

To make sure of my belief I connected two computers in a head to head game in the basic non-FH Warbirds. I had one computer fly the A6M on reduced throttle while the computer I flew with used a Spitfire I to spray the A6M with .30 caliber bullets, so as to do only enough damage to damage the A6M's fuel. Sure enough, the central fuel became damaged in the first test.

Why the extra central fuel tank?

Some versions of the A6M had two fuel tanks within the fuselage, but none of these are modeled in Warbirds.

In Rene J. Francillon's book Japanese Aircraft of the Pacific War, there is a passage that describes A6M's with 2 central fuel tanks:

"The crushing defeat suffered during the battle of the Philippines resulted, on 23 July, 1944, in an urgent request from the Navy to modify the Reisen by (1) installing two additional 13.2 mm Type 3 machine-guns in the wing outboard of the cannon ; (2) mounting an armour plate behind the pilot's seat ; (3) fitting a 140 litre (30.8 Imp gal) self-sealing fuel tank behind the cockpit ; and by (4) installing wing racks for unguided air-to-air missiles."

This passage, however, describes the A6M5[highlight]c[/highlight], which is not modeled on the Free Host. Gold pilots, do not get excited about the air-to-air missiles, only 93 A6M5c's were ever made.

All Zero's which were built before the A6M5c (which includes all the A6M's on the Free Host) had a fuel arrangement as described on this site:

"Normal fuel capacity is 134 U. S. gal., with 20 in a 12 1/4-lb. fuselage tank set just aft of the firewall, and 57 gal. in each of two 24-lb. wing tanks set between spars and extending out 49 1/2-in. from the root. All the tanks are light welded aluminum, are not self-sealing or protected in .any way, and are not an integral part of the aircraft structure."

My research indicates that there should be only one central fuel tank in the A6M series, and that this fuel tank was already in the model of the A6M before version 1.60 was released. I think that it is a possibility that this second fuel tank could be the cause of the inferior flight performance of the A6M series.

About the N1K1/2 series, I have found information which suggest that it was a very impressive fighter aircraft.

Rene J. Francillon writes about its combat flap system in Japanese Aircraft of the Pacific War:

"Modifications were also made to the combat flap system, and, whereas flap extension was manually controlled on the Kyofu, the flaps were operated automatically on the land-based fighter." -the Kyofu was the seaplane predecessor to the N1K1.

This site goes into more detail about this combat flap system:

"A unique feature of the N1K1-J was its set of combat flaps. Whereas flap extension was manually controlled on the Kyofu seaplane, the flaps on the landplane version had the ability automatically to change their angle in response to changes in g-forces during maneuvers. This automatic operation freed up the pilot from having to worry about his flaps during combat, and eliminated the possibility of a stall at an inopportune time."

"Once in the air, the N1K1 was found to be an extremely pleasant aircraft to fly and it had remarkable maneuverability by virtue of its combat flaps."

In Japanese Aircraft of the Pacific War Rene J. Francillon also comments on the N1K1's exceptional maneuverability for a plane of its size and weight:

"The company test pilot also complained of poor visibility during taxi-ing, resulting from the exceptionally long undercarriage, and of excessive propeller torque during take-off. However, in flight the aircraft possessed pleasant handling characteristics and was almost as manoeuvrable as the Mitsubishi Reisen."

Outstanding maneuverability was apparently also a feature of the N1K2-J:

"In operation the N1K2-J revealed itself as a truly outstanding fighter capable of meeting on equal terms with the best Allied fighter aircraft."

The wing loadings of the N1K1-J and N1K2-J were 34 lbs/sq. ft. and 34.9 lbs/sq. ft., respectively. These wing loadings are good, but not optimal. The Laminar-flow wing and the automatic Fowler-type flaps are what made the N1K1/2 series the great turners they were.

If the A6M were to be restored to its pre-1.60 modeling, it would be a spectacular dogfighter. The N1K1/2 series, almost as maneuverable as the A6M, would then also be great dogfighters.

 

@N1K:

I recognise much of that data from sifting through it for the FH team in the past. The plane was very maneuverable indeed, but not to Japanese standards. Its qualities lay elsewhere. It wasn't so good at slow speed turning, even though it was a pleasant plane to fly. It was a good turner (when compared to American planes), but relied on heavier armor, making it much heavier and less of a turner. The Shiden was agile, but not nimble like a Zero. It's main quality was that it was able to compete with American fighters when turning at high speeds.

[source]

<Z>

 

The armor and additional weapons in the wings did not make it too much heavier. A good indicator is, of course, the wing loading. This excerpt from this site explains how the A6M's low wing loading was directly responsible for its maneuverability:

"It has a fairly high-lift, low-speed wing with a very low wing-loading, giving it a very low stalling speed, well below 60 knots. This is the reason for the phenomenal turning ability of the airplane, letting it out-turn any Allied fighter at the time. Turning ability is very simply the ability to "pull harder," and put more g-load on the wings before the accelerated stall occurs. If you have a Mustang with a stall speed of 80, and the Zero with a stall speed of 55, and the dogfight is at 140 knots, the Mustang can pull only 3g before stalling, and the Zero could pull 6.4g before the stall."

In other words, having more lift available for the plane's weight (the definition of low wing loading), allows a plane to pull more G's - to outmaneuver another plane.

Wing Loadings (lbs/sq. ft.)

A6M2 22.0
A6M3 24.2
A6M5 26.3
Ki-43-IIb 28.0
Ki-61-Ib 30.2
N1K1-J 34.0
F6F-5 34.1
N1K2-J 34.9
Ki-61-I-KAIc 35.1
Ki-84-Ia 35.1
Ki-44-IIb 37.7

The N1K1-J may be heavy by Japanese standards: 8,598 lbs loaded. Yet again, the wing's size was designed to create enough lift to allow it to turn better - 253 square feet. When this is combined with a plane that has Fowler flaps which automatically extend in combat, the wing produces even more lift than a normal wing of its size.

It is no wonder that Rene J. Francillon stated:

"...in flight the aircraft possessed pleasant handling characteristics and was almost as manoeuvrable as the Mitsubishi Reisen."

His book Japanese Aircraft of the Pacific War is very difficult to find, but it is the most sought-after book on this topic because, as the description of the book reads:

"The result of twelve years of painstaking research, this book was made possible by the co-operation of various US Government agencies which gave the author access to documents confiscated after the Japanese surrender."

So his statement that the N1K1/2 series was almost as maneuverable as the A6M probably was his conclusion after reading official Japanese reports about the flight tests of the N1K1/2.

My research about the wing loadings and combat flap systems of the Shiden series proves that this statement about the Shiden's performance is probably true.

Even your own source says this:

"Son génial système de volets de combat automatiques grâce à un système à dépression et tubes de mercure lui confère une maniabilité comparable à celle du A6M5."

The N1K1/2's wings are capable of flying at slow speeds with little effort from the pilot, but its engine also allows it to fly at slow speeds. Flying at a slow speed requires force to overcome the force of gravity. The engine is responsible for both of the forces which an airplane uses to overcome gravity - thrust and lift. The lift prevents the plane from stalling and the thrust provides the forward motion. If the plane has a lot of thrust available with a proportionally small weight (low power loading), a plane can create an unbalanced situation at low speed - in which the plane can accelerate in a climb.

Power Loadings (Loaded Weight/HP)
Ki-44-IIb 4.0
Ki-84-Ia 4.0
N1K1-J 4.4
N1K2-J 4.4
Ki-43-IIb 5.0
A6M3 5.0
A6M5 5.3
A6M2 5.5
Ki-61-Ib 5.53
F6F-5 5.7
Ki-61-I KAIc 6.48

Clearly the N1K1/2 have power loadings which help with their low-speed flying capabilities.

Zembla, my research shows that the N1K1/2 do indeed live up to the claims that historians make about their performances.

 

True, but the more hp the less "agile" the engine... in other words, it can only go through the rpm-band so quick. The more hp, the longer it takes to go through the whole rpm spectrum, this results in sluggish behavior at slow speeds.

Read this

My research shows otherwise. And that wasn't the only source that claimed it to be out of its league in slow speed maneuvring.

<Z>

 

Erm, what's this crap about the Shiden's "excellent speed" I read everywhere?? The Shiden had a top speed of 370 mph ... not too bad but hardly excellent. Even a Hellcat was faster than that.

 

It is interesting to note that there are many contradictions between Air Warrior and Combat Flight Simulator 2.

Air Warrior: "It is not, however, an especially good turning aircraft at low to medium speeds."

CFS2: "The Shiden climbs well and can turn very tightly at low to medium speed."


Air Warrior: "However, the George has far better high speed handling than the Ki, and is competitive with the Corsair in this regard."

CFS2: "It has good top speed, although its handling suffers above 250 knots."

It seems that both Air Warrior and Combat Flight Simulator 2 are guilty of ignoring history to some degree. Air Warrior's modeling of the Shiden, however, seems to deviate more from reality:

From this site:

"The plane is also very brittle, unable to withstand high G loads at speed, or take damage."

I think, however, that the N1K1/2 was a good low speed dogfighter for two reasons:

1. All the historical information seems to point to the N1K1/2 having the right technology to be a good low-speed dogfighter. The flight simulators which state otherwise do not provide an explanation why a plane with good wing loading and excellent flaps would not be a good stallfighter.

2. Air Warrior's description of the N1K1: "When it comes to a slow speed dogfight, the Hellcat, Ki, [highlight]P-38[/highlight], and, of course, the Zero can quickly make the George feel out of its element."

I would laugh if a P-38 could beat a N1K1 in a slow speed dogfight. The unfortunate death of Thomas Mcguire proves how much of a mistake it was to try to engage in any sort of dogfight with a maneuverable Japanese plane.

So, in this case, I think that we should focus our attention on the real technical data.

By the way, why the second central fuel tank in the A6M?

 

I disagree. When utilizing its superb flaps, a well-flown P-38 could be a dreadful opponent in a slow-speed turning fight. Of course this doesn't mean a 38 would stand the slightest chance of out turning such nimble planes as the A6M or the Ki-43, but against the less agile Japanese planes, a very good pilot could risk a turn or two. The reason for McGuire's death was kill greed and simple bad luck, not the Lightning's (nonexistent) lack of slow-speed turning ability. Had he ordered his flight to drop their fuel tanks before engaging the Japanese plane ... AND had that second Japanese plane not appeared right out of nowhere to bounce McGuire's flight, things would probably have worked out very differently.
McGuire's demise proves absolutely nothing at all about the P-38.

 

Red Ant it may sound strange, but I think we are thinking the same thing.

Yes, and I have a reliable source which states that the N1K1/2 was almost on par with the A6M5 with regard to maneuverability. The N1K1/2 must therefore also be a threat to the P-38 in a dogfight, but a P-38 has the advantage in raw speed, power and altitude performance.

Less agile Japanese planes include late-model Ki-61's, the Ki-44-IIb and the Ki-84-Ia. The P-38 could certainly afford to be more aggressive against these types.

As you and I both agree, it is a mistake for a P-38 pilot to dogfight against the maneuverable Japanese planes. Yet if it had been a Ki-44 which had ambushed Mcguire's group, he would not have had to turn his P-38 so quickly and he might not have stalled and crashed.

 

Afair it was a pair of ki-43's flown 2 very experienced pilots, both being flight instructors with combat experience. McGuire fell victim to his overconfidence...

 

One was a Ki-43, the other was a Ki-84.

 

this story is told a bit different every place i read it, but 1 thing is always the same: McGuire was hungry to beat Bong's number & that is why he lost his streak

 

Yes, this is very confusing. Babek posted a version which I have seen in many places. Then again, I have seen other versions in many places.

It seems that no one can agree on the number of Japanese planes present, the type of Japanese planes present or the names of the Japanese pilot(s).

I also did not know that Thomas McGuire crashed at 700 km/h. I had heard that he crashed in a jungle, not the sea... so confusing!

 

There were no Zeros involved at all, nor did a pilot named Shoichi Sugita take part in the engagement. No offense to Babek, but that version of the story is hogwash.

 

I have more information about the flaps of the N1K1/2.

Like the P-38's flaps, the Shiden's flaps were Fowler flaps - the most efficient type of flaps among WW2 fighters. Fowler flaps, as many know, increase both the area and curvature of a wing, resulting in a great addition to lifting capability. The P-38's Fowler flaps made it very maneuverable for a plane of its weight and wing loading. The same was true for the N1K1/2:




These Fowler flaps automatically extended in turns, meaning that, like a P-38 pilot, a N1K1/2 pilot could benefit from a dramatic increase in turning ability but be still be free from the task of controlling the flaps. The Shiden pilot would therefore be able to better concentrate on the dogfight.

The wing loadings of the N1K1-J and N1K2-J were 34 lbs/sq. ft and 34.9 lbs/sq. ft., respectively. Alone, this was not good enough to be in the same league as the A6M's maneuverability. It was the automatic Fowler flap system which made the N1K1/2 almost on-par with the A6M in turning.

-----

Exec, is there any word on why the second central fuel tank was added to the A6M?

 

if flaps add so much lift, how come planes climb better without flaps extended?
how is the effectiveness of control surfaces changed at near stall speed?

 

In combat flaps can aid climbing, because sometimes planes are climbing at speeds only slightly above stall speed. Flaps can help the plane fly/climb at these slower speeds. Still, the major distinction one must make here is this: flaps enable a plane to climb steeper, not faster. When pilots use flaps to help themselves climb they are sacrificing climb rate, but they may need those extra few degrees of climb to shoot the enemy.

When one is not under attack, flaps are not necessary. When a plane is climbing, its lift requirements are not much different from level flight's requirements. The weight of the aircraft does not change when the plane enters a climb. No extra g-forces are experienced by a plane in a climb. What extra lift do the wings need to provide, then? Perhaps the only difference is that a sustained climb is at a lower speed than level flight is. Because of this, the climbing wing needs a little extra angle of attack to be able to provide the same amount of lift at a lower speed. The angle of attack is not large enough and the speed not low enough to require flaps, however.

 

Re the A6M fuel tank, you said that you tested a non-FH version of WB. I suppose it is possible that the FH developers removed the central tank in an earlier FH release, then restored it in 1.60.

 

Let's suppose that this is true. What are the FH developers doing when they arbitrarily change the number of fuel tanks in a plane? That is exactly the kind of policy that has turned so many away from the game. Furthermore, from what this community has seen in the releases of the new versions, I am skeptical that the developers could remove a fuel tank, put it back in and still have the same aircraft. Look at what happened to the N1K1/2 when 1.64 came out. The only specific change made to the planes was the addition of a 4x50kg loadout, and what happened? The planes shook above moderate speeds.

I still think that the A6M has one fuel tank too many. In my opinion it is this modeling mistake coupled with the more recent elevator bugs which makes the A6M the substandard plane that it is, especially at low speeds.

 

Every day things change in the arena. No anouncement is ever made.

For one second do you think admins list EVERY change in each version on their little posts? I think not.

 

a6m, big plane with big wings, maybe it had very high induced drag. with it's full load of 3100km worth of gas it is crap (probably foward CG too, if all that petrol is in the wings), but fly it with 20% & it is ass kick. Big low loading wings aid flight on the back side of the power curve also, which is a poor place to do aerobatics. Wing tanks also provide also for a poor polar moment of inertia. I know of 1 aerobatcs plane that is certified on the aerobatic category only when the wing tanks are empty