The Zero's Maneuverability

[MIflyer]

There was a post about the stretchy control cables. I'm going nuts trying to remember the thread.

Yes, I heard about it from a friend of mine who had read a book covering that. However, that page from the Av Week article shows that the ailerons were controlled by control rods, not cables.

As for the elevator, Corkey says that BOTH the elevator and the ailerons were "like set in concrete" at 240 kts, which is about 275 mph. The USN report said the control forces got much heavier at above 200 kts, so Corky was going considerably faster than that. The rudder remained light and effective at high speeds, though, which is not a good thing. A rudder will get you in trouble fast, which is the reason the Ercoupe does not have rudder pedals.

 

[ThomasP]

Hey MIflyer,

As I said above "If the elevators locked up when Meyers was flying an A6M then the elevators were either damaged or sub-standard due to another cause."

If the elevators were locked up "like set in concrete" at 240 kts then no Japanese pilot would ever have survived a dive at the A6M's VNE since they would not have been able to pull out. The idea of the service A6M airframe not being able to pull out of a dive is silly - as is evidenced by the fact that they routinely pursued P-39s and F4Fs in dives. They did not always catch them, but chase them they did, and at over 400 mph IAS sometimes (according to the US pilots). If the elevators were locked up "like set in concrete" the Japanese pilots that survived the war would have written about it, but to date I have not run across anything like that mentioned.

Also, and think about this, if the elevators were "like set in concrete" at 240 kts then no A6M could pull up into a zoom climb at 240 knots plus, or roll (relatively slowly) into a turn and pull any Gs since the elevators would be "like set in concrete". All he would be able to do is slowly roll until he dropped below 240 knots. In order to begin any maneuvers quickly the A6M pilots would have to cut the throttle and wait until they slowed down to what? 230 knot? 220 knots? 210 nots? No sane Japanese pilot would ever fly the A6M at over 240 knots in a combat area since they would be dead meat if jumped due to being unable to do anything until the aircraft slowed down to below 240 knots.

Do you remember reading anywhere - written by a Japanese pilot - that they had to just coast along with the throttle cut back until they slowed down to less than 240 knots before they could do any maneuvering?

Maybe Corkey had weak arms?

 

[GregP]

You can climb or dive without using the elevator by adding or removing power. Most light aircraft do it that way. But you cannot do a loop or dive onto a target without using a LOT of elevator. And if the elevator is "frozen in concrete" you ain't doing that.

Now, as I understand it, the Zero was designed so that if the pilot tried to exert too much force the controls stretched to keep him from breaking the structure. And I have only read of one Japanese fighter breaking up in a dive and that was an Oscar fighting with P-51A over Burma, so the Zero did not seem to come apart very easily.

I don't think you climb or dive in combat by adding or removing power. That's for peacetime gentle flying. In combat, you don't do anything gently or you become a very good target, likely for the enemy you didn't see but who sees YOU.

 

[SaparotRob]

GregP : Do you recall a post about some amount of stretch in the Zero's control cables?

 

[Holtzauge]

About the Zero's elevator responsiveness and the cable stretch solutions: I noticed that this was mentioned earlier on in this thread and that someone was looking for a reference. There may of course be Allied reports saying the same thing, but the information can also be had from the horse's mouth so to speak :

In his memoir book Eagles of Mitsubishi, the Zero's Chief Designer Jiro Horikoshi actually dedicates a number of pages (pages 72 to 83) on this subject, and begins by stating that it was though that the Zero was actually TOO responsive in pitch at high speeds. That the roll response at high speed was poor is acknowledged in other parts of the book, but apparently the elevator was considered to be too responsive even at higher speeds. So while he confirms that stick forces in roll were too high, apparently they were not it pitch.

And those pages in the book also cover the solution, which was reducing the diameter of the elevator control cables from 4 to 3.5 and 3 mm in diameter. This introduced more flex in the elevator control circuit at high dynamic pressures, and it seems to have worked, because when they did flight trials, they concluded that not only did this fix the excessive responsiveness at higher speeds, but at the same time it did not mess with the low speed handling which still remained crisp.

Picture below from Jiro Horikoshi's book Eagles of Mitsubishi

 

[tyrodtom]

About the Zero's elevator responsiveness and the cable stretch solutions: I noticed that this was mentioned earlier on in this thread and that someone was looking for a reference. There may of course be Allied reports saying the same thing, but the information can also be had from the horse's mouth so to speak :

In his memoir book Eagles of Mitsubishi, the Zero's Chief Designer Jiro Horikoshi actually dedicates a number of pages (pages 72 to 83) on this subject, and begins by stating that it was though that the Zero was actually TOO responsive in pitch at high speeds. That the roll response at high speed was poor is acknowledged in other parts of the book, but apparently the elevator was considered to be too responsive even at higher speeds. So while he confirms that stick forces in roll were too high, apparently they were not it pitch.

And those pages in the book also cover the solution, which was reducing the diameter of the elevator control cables from 4 to 3.5 and 3 mm in diameter. This introduced more flex in the elevator control circuit at high dynamic pressures, and it seems to have worked, because when they did flight trials, they concluded that not only did this fix the excessive responsiveness at higher speeds, but at the same time it did not mess with the low speed handling which still remained crisp.

Picture below from Jiro Horikoshi's book Eagles of Mitsubishi


View attachment 795618

And that cable stretch could have been a maintenance item, cable checked often and maybe replaced at intervals.
Most of the allied flight test was on a small pool of captured Japanese aircraft, a lot of them rebuilt wrecks.
How many Zero tech manuals do you think the allies had?

I was a helicopter crew chief in the early 70's, kept the tech manuals close, and have never broke that habit after 50 years of working on cars. You can't do your best work on any mechanical system if you don't know the original manufactures specifications.

 

[MiTasol]

Spitfires didn't suffer this damage in actual combat with A6M's so having it happen in a mock dog fight is highly doubtful, still calling it BS.

All I can say is read this from the pilots son.

A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

My dad was the Spitfire pilot against the Hap and he bent the tail of the Spitfire 15 degrees (Dad's annotation) doing some pretty evasive 'high G' manoeuvering. He also flew a Kittyhawk against a Spitfire at Mildura during tests - parameters attached. In both cases the Volkes Filter diminished...

ww2aircraft.net

 

[GregP]

GregP : Do you recall a post about some amount of stretch in the Zero's control cables?

No, and the cables that came out of our A6M5 Model 52 Zero during overhaul were regular, normal twisted steel steel flying cables, as are the new ones in it now. They don't stretch and didn't. The rudder trim mechanism is very impressive with zero slop in it. It is simple and VERY effective.

I'll ask Steve Hinton about high-speed control forces in the Zero and he may tell me. I'm fairly sure he and the other pilots that fly it don't "run it hard" when demonstrating it. There is no real need and WE are paying for the airplane, so there is no need to extract the maximum performance from it and put the attending wear and tear on the engine / airframe. On the other hand, I'm sure they "play with it a bit" when they are away from the traffic pattern and the general airport area.

I would if I had the opportunity to fly it. Nothing too hard, mind you, but at least bend it around a bit to see how it flies. Since it is a fighter with almost legendary maneuverability, positive-g barrel rolls, 3-4 g loops, a few stalls, and a few steep turns should not be anything to worry about at cruise power levels without causing concern.

It's sort of like saying, "we don't do aerobatics, but we do practice recovery from unusual attitudes." I'm not saying they DO that. I'm saying someone who flies our Zero very likely knows how heavy the controls get up above 250 knots, and MAY tell me that if I ask. They also may NOT tell me, or they might tell me and ask that I not pass it along ... no, I don't know why that should be so, but it might be. Can't say for sure at this time. The old song goes, " ... goes to show you never can tell."

If I get requests like that from the museum, I honor them. I have many pics of the major overhaul we did back in 2016 on the Zero since I worked on it a small bit, but have been asked not to post them, so I don't. I have many cockpit pics of various airplanes that I have also been asked not to post them, so I don't.

Cheers, SparotRob!

 

[PAT303]

The A6M's elevators became heavy at higher speeds but did not 'lock up' or otherwise become ineffective, and according to the Japanese test pilots the effectiveness of the elevators was acceptable. This was as reported by the Japanese service pilots. If the elevators locked up when Meyers did the flying then the elevators were either damaged or sub-standard due to another cause.

Every Allied report of the A6M states the controls stiffened up as the speed increased to the point of being immoveable, the same with every other fighter as the speeds exceeded anything experienced in peacetime.

 

[PAT303]

All I can say is read this from the pilots son.

A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

My dad was the Spitfire pilot against the Hap and he bent the tail of the Spitfire 15 degrees (Dad's annotation) doing some pretty evasive 'high G' manoeuvering. He also flew a Kittyhawk against a Spitfire at Mildura during tests - parameters attached. In both cases the Volkes Filter diminished...

ww2aircraft.net

Spitfire pilots did things in combat that far exceed anything done in mock combat without bending their aircraft, I'm wondering whether the pilot did a heavy landing or the plane sustained previous damage.

 

[SaparotRob]

No, and the cables that came out of our A6M5 Model 52 Zero during overhaul were regular, normal twisted steel steel flying cables, as are the new ones in it now. They don't stretch and didn't. The rudder trim mechanism is very impressive with zero slop in it. It is simple and VERY effective.

I'll ask Steve Hinton about high-speed control forces in the Zero and he may tell me. I'm fairly sure he and the other pilots that fly it don't "run it hard" when demonstrating it. There is no real need and WE are paying for the airplane, so there is no need to extract the maximum performance from it and put the attending wear and tear on the engine / airframe. On the other hand, I'm sure they "play with it a bit" when they are away from the traffic pattern and the general airport area.

I would if I had the opportunity to fly it. Nothing too hard, mind you, but at least bend it around a bit to see how it flies. Since it is a fighter with almost legendary maneuverability, positive-g barrel rolls, 3-4 g loops, a few stalls, and a few steep turns should not be anything to worry about at cruise power levels without causing concern.

It's sort of like saying, "we don't do aerobatics, but we do practice recovery from unusual attitudes." I'm not saying they DO that. I'm saying someone who flies our Zero very likely knows how heavy the controls get up above 250 knots, and MAY tell me that if I ask. They also may NOT tell me, or they might tell me and ask that I not pass it along ... no, I don't know why that should be so, but it might be. Can't say for sure at this time. The old song goes, " ... goes to show you never can tell."

If I get requests like that from the museum, I honor them. I have many pics of the major overhaul we did back in 2016 on the Zero since I worked on it a small bit, but have been asked not to post them, so I don't. I have many cockpit pics of various airplanes that I have also been asked not to post them, so I don't.

Cheers, SparotRob!

So I guess it's: Stretchy cables-Myth Busted!

 

[Thumpalumpacus]

So I guess it's: Stretchy cables-Myth Busted!

Steel wire can and does stretch. Steel can and does suffer both plastic and elastic deformation. Elastic is the sort where the steel returns to its original shape. Plastic is the sort of deformation that imparts a permanent change in the steel's shape. That shape includes length.

Steel wires can snap, and that can be a direct result of stretching beyond the metal's lateral tolerances.

 

[tyrodtom]

Steel wire can and does stretch. Steel can and does suffer both plastic and elastic deformation. Elastic is the sort where the steel returns to its original shape. Plastic is the sort of deformation that imparts a permanent change in the steel's shape. That shape includes length.

Steel wires can snap, and that can be a direct result of stretching beyond the metal's lateral tolerances.

I helped a aircraft mechanic assemble the wings and tail surfaces of a aircraft I painted. He had tools to measure the tautness of the control cables and where to test them were in the AC assembly manual. They had turnbuckles to adjust the tautness.
Too loose and you'd have control surface slop, or worse flutter, too tight and you'd wear the pulleys out,
among other things.
Those control cables definitely stretched.

 

[Thumpalumpacus]

I helped a aircraft mechanic assemble the wings and tail surfaces of a aircraft I painted. He had tools to measure the tautness of the control cables and where to test them were in the AC assembly manual. They had turnbuckles to adjust the tautness.
Too loose and you'd have control surface slop, or worse flutter, too tight and you'd wear the pulleys out,
among other things.
Those control cables definitely stretched.

Anyone who's had to tighten up the gear-cables on an 18-speed mountain-bike knows steel cable can stretch.

 

[marathag]

No, and the cables that came out of our A6M5 Model 52 Zero during overhaul were regular, normal twisted steel steel flying cables

Same cable as the earlier models?

That said, my experience with wire rope, Steel wire is not rubber. Once it stretches, it doesn't go back to the original length. It's already been pre-stretched.

Did the earlier A6M have some separate spring loaded tensioner missing from the later craft?

 

[Greg Boeser]

As I said, the Corky Myer article as well as the USN reports of the tests on the Koga Zero.


Ahhhh, you missed the point entirely. They WERE NOT in frontline service BECAUSE they did not have armor, self sealing tanks, etc. The AVG was going to have some CW-21's but they ran into a mountain along the way, which reduced their combat effectiveness considerably. Countries like Thailand, China, and Argentina adopted some lightweight fighters, including the export fixed gear version of the Hawk 75, but had little choice.

The Dutch flew a few flights of Hawk 75s, CW-21B and B339s in the NEI.
The Curtiss planes faired poorly. The Brewsters did better.

 

[Greg Boeser]

Oops - I should have said Hurricane and bubble canopy Mustang.
The P-66 was a razorback like the Hurricane and the A6Ms all had a framed bubble canopy. I guess the difference between a straight line from the top of the canopy to the tail versus a straight line from the engine to the tail with a camel hump canopy is close enough for CGI. We all know how distorted AI (assinine intelligence) depictions of aircraft are.

Actually, I really enjoy the fantasy machines that keep popping up in ads for various "history" websites.

 

[GrauGeist]

Steel rope is twisted in a spiral pattern.

Yes, it will "stretch" to a certain degree under load. The larger the diameter, the less "give" under load.

If Jiro Horikoshi changed the control cables to a smaller diameter, then there is a good reason he did so.

If there was ever a solid, first-hand account for a source of information for the A6M, I'm pretty Mr. Horikoshi would be it.

 

[sotaro]

Yes, I heard about it from a friend of mine who had read a book covering that. However, that page from the Av Week article shows that the ailerons were controlled by control rods, not cables.

As for the elevator, Corkey says that BOTH the elevator and the ailerons were "like set in concrete" at 240 kts, which is about 275 mph. The USN report said the control forces got much heavier at above 200 kts, so Corky was going considerably faster than that. The rudder remained light and effective at high speeds, though, which is not a good thing. A rudder will get you in trouble fast, which is the reason the Ercoupe does not have rudder pedals.

I have a vague memory of a patent being filed for the way that the A6M2 ailerons were controlled in a variable manner and speed was a key determinant.

 

[GregP]

Every Allied report of the A6M states the controls stiffened up as the speed increased to the point of being immoveable, the same with every other fighter as the speeds exceeded anything experienced in peacetime.

Not really for every other fighter. The Fw 190 would do aileron rolls at 400 mph that would tear the wings off Allied fighters.

There is a very nice roll authority chart on WWIIaircraftperformance showing the Fw 190's roll authority quite well. The Spitfire is not thought of as a great roller, but apparently the later models were no slouches.

Several fightfers did pretty well at higher speeds. They were the ones with marginal stability at cruise speeds, unless I misremember. It's been known to happen ...