Why the early war Japanese fighters were structurally fragile and unarmored?

[FLYBOYJ]

I think it may be said that the design and manufacturing philosophy employed by Japan in the '30s and '40s has extended to their modern automobile industry: an emphasis on light weight and efficiency, which in the case of automobiles has made Japan what it is today thanks to oil prices.

I don't think it's fair to say that this philosophy was imposed upon Japan due to an inability of Japanese industry to manufacture powerful aircraft engines. The Nakajima Sakae that powered the Zero possessed an impressive power to weight ratio (much as their modern automotive counterparts do). In fact when restorers of Zeros today replace the Sakae with the best American-made replacement engines they can find, the performance of the aircraft suffers dramatically. There is simply no non-Japanese radial engine in the world capable of replacing the original - anywhere, by any manufacturer or nation.The Japanese adopted this philosophy in large part as the aviation industries of the world debated the value of light versus heavy fighters (and the British built the Defiant, unfortunately). It was certainly a natural choice for Japan to go the light fighter route for economic reasons, but that wasn't the only factor. The US experimented with light fighters as well, and the idea was behind the original Bf109 in Germany. Unlike the 109, however, the Zero was less able to adapt itself to more powerful engines and heavier equipment as the need for such measures became apparent. But for many months of the war the Zero ruled the Pacific.

The designers of the Zero also created the Raiden (or "Jack"), which was a heavy fighter/interceptor in every respect with impressive performance comparable to Allied designs. Ironically, most Japanese pilots disliked it immensely (Saburo Sakai saying "it flew like a truck"). The Japanese could do it, and do it well. But after 1942 their cause was lost.

Ron Cole

View attachment 198937



Cole's Aircraft Website:index

I believe only one restored Zero currently flies wth a US engine (R1830) and it's loacted at the CAF chapter in Camarillo, CA. I have met some of the pilots who have flown this aircraft and one of our mods on this site is a member of this CAF chapter. Never have I heard "the performance of the aircraft suffers dramatically, " so please if you have information on this, I'm all ears. Additionally I hope Eric sees this and maybe can chime in as we can hear "direct from the source."

Here's some basic info comparing the two engines...

Specifications (Sakae 21)
General characteristicsType: 14-cylinder air-cooled two-row radial engine
Bore: 130 mm (5.1 in)
Stroke: 150 mm (5.9 in)
Displacement: 27.8 L (1,700 in³)
Length: 1,600 mm (63 in)
Diameter: 1,144 mm (45.0 in)
Dry weight: 533 kg (1,180 lb)
ComponentsValvetrain: Overhead valve
Supercharger: Gear driven, two speed.
Fuel system: Nakajima twin choke carburettor, automatic mixture and boost control.
Cooling system: Air-cooled
PerformancePower output: 761 kW (1,020 hp) at 2,600 rpm at 6,400 ft (1,950 m)
Specific power: 30.2 kW/L (0.66 hp/in³)
Compression ratio: 7:1
Power-to-weight ratio: 1.43 kW/kg (0.87 hp/lb)

Specifications (R-1830-S1C-G)
Pratt Whitney R-1830 "Twin Wasp" (sectioned)Data from [2]

General characteristicsType: Fourteen-cylinder two-row supercharged air-cooled radial engine
Bore: 5.5 in (139.7 mm)
Stroke: 5.5 in (139.7 mm)
Displacement: 1,829.4 in³ (30 l)
Length: 59.06 in (1,500 mm)
Diameter: 48.03 in (1,220 mm)
Dry weight: 1,250 lb (567 kg)
ComponentsValvetrain: Two overhead valves per cylinder
Supercharger: Single-speed General Electric centrifugal type supercharger, 7.15:1 reduction
Fuel system: Two-barrel Stromberg carburetor
Fuel type: 95-100 octane rating gasoline
Cooling system: Air-cooled
Reduction gear: Epicyclic gearing, 2:3
PerformancePower output:

1,200 hp (895 kW) at 2,700 rpm for takeoff
700 hp (522 kW) at 2,325 rpm cruise power at 13,120 ft (4,000 m)
Specific power: 0.66 hp/in³ (29.83 kW/l)
Compression ratio: 6.7:1
Specific fuel consumption: 0.49 lb/(hp•h) (295 g/(kW•h))
Power-to-weight ratio: 0.96 hp/lb (1.58 kW/kg)

 

[evangilder]

The Nakajima Sakae that powered the Zero possessed an impressive power to weight ratio (much as their modern automotive counterparts do). In fact when restorers of Zeros today replace the Sakae with the best American-made replacement engines they can find, the performance of the aircraft suffers dramatically. There is simply no non-Japanese radial engine in the world capable of replacing the original - anywhere, by any manufacturer or nation.

Uh, no. I have personally witness 3 authentic Zeros fly, one with a Sakae and 2 without. There is a slight difference in the sound, but other than that, the aircraft performs pretty much the same. Aside from that, the Sakae 21 was truly a "Japanese" engine. The Sakae was pretty much a license built Gnome-Rhone 14K.

With any aircraft, there is a ratio of weight to power that will effect things like maneuverability and range. The Zero was built for range, and that it had. Below 250 MPH, nothing could out-turn it. Above that speed, the ailerons "turn to concrete", according to one of the pilots I know who has flown the Zero. Most allied pilot learned (sometime the hard way) that a slow speed turning flight with a Zero was not winnable.

There was one piece of armor in the Zero, believe it or not. It's about the size of a basketball in size and sits just behine the pilot in about the small of the back. Not a whole lot of help. The main windscreen is also very light. But if you put armor, self-sealing fuel tanks and a bullet resistant canopy on it, the weight increases, which causes performance and range to suffer. It's always a trade-off, and for the early years of the war, it worked well for the Japanese.

 

[Vincenzo]

i think that is a old mith that Sakae was a GR-14K.
the data of power for Sakae 21 were 1100 HP at 2700 rpm t +200 boost (nominal power ) at 2.850 meters, and 980 hp at 6.000 meters (1130 HP at TO with TO setting (2750 rpm +300 boost)
Twin Wasp S1C-G get 1200 HP to TO and only 1050 HP at nominal at 6.500 feet so is inferior in large parte of altitude and this is with 100 octane fuel, early Twin Wasp with 87 octane fuel get only 900 HP nominal (commonly at relatively low altitude). If you has a R-1830-76 of navy this get nearly same power of Sakae-21 at high altitude (ever with 100 octane fuel) but is larger and heavier (~200 kilos)

 

[tomo pauk]

I think it may be said that the design and manufacturing philosophy employed by Japan in the '30s and '40s has extended to their modern automobile industry: an emphasis on light weight and efficiency, which in the case of automobiles has made Japan what it is today thanks to oil prices.

...

What makes Japanese cars so great (and S. Korean, of course) is their utter reliability.
Italian and French manufacturers make many different low-consumption cars (just Fiat makes 4 models (more maybe?), from Grande Punto down), but those are strong only in the domestic markets. The British also had many low-consumption stuff, but their auto industry is in shambles for quite a while.

 

[FLYBOYJ]

i think that is a old mith that Sakae was a GR-14K.
the data of power for Sakae 21 were 1100 HP at 2700 rpm t +200 boost (nominal power ) at 2.850 meters, and 980 hp at 6.000 meters (1130 HP at TO with TO setting (2750 rpm +300 boost)
Twin Wasp S1C-G get 1200 HP to TO and only 1050 HP at nominal at 6.500 feet so is inferior in large parte of altitude and this is with 100 octane fuel, early Twin Wasp with 87 octane fuel get only 900 HP nominal (commonly at relatively low altitude). If you has a R-1830-76 of navy this get nearly same power of Sakae-21 at high altitude (ever with 100 octane fuel) but is larger and heavier (~200 kilos)

Even with this, there is no documented proof that I'm aware of that the restored CAF Zero flying with the R1830 installed has "the performance of the aircraft suffer dramatically" even with the increased weight.

 

[Vincenzo]

Is not a documented proof but with a heavier, larger and less powerfull engine is highly probable that the performance suffer, maybe not dramatically

 

[FLYBOYJ]

Is not a documented proof but with a heavier, larger and less powerfull engine is highly probable that the performance suffer, maybe not dramatically

Not really. A lot of equipment is removed from these aircraft during restoration, a big factor are the guns and radios, although I know many japanese aircraft did not have radios installed. I've been around several guys who have flown both the Camarillo and Chino Zero (the later has the Sakae engine)and never heard of any reports of the P&W Zero dramitically affected by the intallation of that engine. Keep in mind that both aircraft are not flown hard and are very well maintained from what I have seen.

Even with a larger and less powerful engine one has to look at the overall weight of the aircraft, the prop engine combination and the way its rigged. Mind you this dicussion centers around restored aircraft being operated in "today's" world.

 

[Vincenzo]

i can agree that flying them how they flying today the difference maybe negligible

 

[ColesAircraft]

Uh, no. I have personally witness 3 authentic Zeros fly, one with a Sakae and 2 without. There is a slight difference in the sound, but other than that, the aircraft performs pretty much the same. Aside from that, the Sakae 21 was truly a "Japanese" engine. The Sakae was pretty much a license built Gnome-Rhone 14K.

With any aircraft, there is a ratio of weight to power that will effect things like maneuverability and range. The Zero was built for range, and that it had. Below 250 MPH, nothing could out-turn it. Above that speed, the ailerons "turn to concrete", according to one of the pilots I know who has flown the Zero. Most allied pilot learned (sometime the hard way) that a slow speed turning flight with a Zero was not winnable.

There was one piece of armor in the Zero, believe it or not. It's about the size of a basketball in size and sits just behine the pilot in about the small of the back. Not a whole lot of help. The main windscreen is also very light. But if you put armor, self-sealing fuel tanks and a bullet resistant canopy on it, the weight increases, which causes performance and range to suffer. It's always a trade-off, and for the early years of the war, it worked well for the Japanese.

That's kind of a bizarre statement. In the first place none of these aircraft are pushed to their limits during airshow displays - especially the Chino Zero which is the only originally-powered Zero in the world and is flown very cautiously, as it should be. Secondly, how can anyone judge and compare performances of aircraft from the vantage point of the ground???

And, indeed, the myth that the Nakajima Sakae was a copy of any other engine originated in the bigoted environment of wartime when whites couldn't conceive that the Japanese were capable of independent ingenuity.

I didn't post my information to start an argument. Just thought I'd share what I know, since the question was posed. My friend Naburo Harada, who owns several restored Zeros in Japan and oversees the Harada Collection (The Harada Collection), knows more than anyone on earth about this engine, the power to weight issue, and the consequences of not using the original Sakae.

Ron Cole

 

[FLYBOYJ]

That's kind of a bizarre statement. In the first place none of these aircraft are pushed to their limits during airshow displays - especially the Chino Zero which is the only originally-powered Zero in the world and is flown very cautiously, as it should be. Secondly, how can anyone judge and compare performances of aircraft from the vantage point of the ground???

Then how can one say the P&W Zero's performance "suffered dramatically" by the intallation of that engine? Neither aircraft are pushed to their limits during routine flight and airshows. BTW, my query is based on comments by the pilots who have flown them, not from a ground vantage point.

 

[Jenisch]

The Japanese adopted this philosophy in large part as the aviation industries of the world debated the value of light versus heavy fighters (and the British built the Defiant, unfortunately).

That was not the desire of Jiro Horikoshi with the Zero. He states in Eagles of Mitubishi: the story of the Zero figher, that lack of more powerful engines not allowed the add of armor and structural strenght and keep up with the requeriments.

As for the Ki-43:


View: https://www.youtube.com/watch?v=u-eBmnpCO18

23s: "They tried too much to increase its range, and so made it fragile". Similar aircraft, similar problem, probably similar engineering challange than the Zero.

Conclusion: if the Japanese didn't have the long range requirement, we probably would see them with aircraft similar to the P-40 and Bf 109.

 

[FLYBOYJ]

Steve Hinton going through the Chino Zero's cockpit


View: https://www.youtube.com/watch?v=R6W9MBK1gJI

 

[FLYBOYJ]

View: https://www.youtube.com/watch?v=UmUseKNrh6Q

I think Eric, knows this guy. Says nothing about this aircraft's "airshow" performance being affected by the instllation of the 1830.

 

[ColesAircraft]

That was not the desire of Jiro Horikoshi with the Zero. He states in Eagles of Mitubishi: the story of the Zero figher, that lack of more powerful engines not allowed the add of armor and structural strenght and keep up with the requeriments.

As for the Ki-43:


View: https://www.youtube.com/watch?v=u-eBmnpCO18

23s: "They tried too much to increase its range, and so made it fragile". Similar aircraft, similar problem, probably similar engineering challange than the Zero.

Conclusion: if the Japanese didn't have the long range requirement, we probably would see them with aircraft similar to the P-40 and Bf 109.

Great video, but wrong conclusion.

Japanese Army fighters had few Army-specified range requirements as a rule. The reason for that was simple: they were designed to fight a continental war in China or Russia where range was not as critical an issue as it was in the Pacific. This made Army fighters, including the "Oscar", of little use in many Pacific campaigns. Remember that the Japanese Army and Navy were to an extent at cross purposes before the war - the Army equipped itself to fight Russia, while the Navy did likewise to fight America; very different enemies! That's why the Army Air Force played no role in the Guadalcanal battles while the Navy had to overextend its deployed G4Ms and A6Ms. They were the only aircraft that could get there and home. In fact the "Oscar" was an even better example of the Japanese 'light fighter' mentality that I mentioned earlier, as range was less an issue in its design than it was for the Zero. Saburo Sakai mentioned this situation to me when I knew him. The Navy pilots resented that the Army planners hadn't placed more emphasis on range, which left the Navy to fight alone in many circumstances.

The closest thing to a heavy fighter that the Army ever produced in quantity was the Ki-44 (the Ki-84 being more a compromise, I think). Again, an example of a good, powerful Japanese engine bolted to an aircraft of good performance. They served the Japanese well in China but were dogged with limited range in the Pacific, where they were seldom even deployed. By the time they were used as interceptors in home defense the type was obsolete and overwhelmed. But a good aircraft it still was, and again shows that the Japanese could do the 'heavy' thing when they wanted to.

The Japanese would have built P-40s??? Sakai expressed contempt for the P-40, as did most Japanese pilots who met them in combat. The Japanese Army actually operated a small unit of captured P-40s they obtained intact from the Philippines, but it was a very short lived experiment. I think it's a beautiful plane, but it wasn't an aircraft, or the embodiment of a concept, that the Japanese wanted to emulate.

Ron Cole

Ron Cole

 

[ColesAircraft]

Then how can one say the P&W Zero's performance "suffered dramatically" by the intallation of that engine? Neither aircraft are pushed to their limits during routine flight and airshows. BTW, my query is based on comments by the pilots who have flown them, not from a ground vantage point.

Easily, when the only person in the world who owns four Zeros says so. Granted, there may be some pro-Japanese bias on the part of the source, but I know how hard Mr. Harada fought for years to get an original Sakae for his airworthy example. It sat, otherwise completely restored, with no engine for close to half a decade.

There may likewise be some pro-American bias in this as well on the part of some pilots. I don't know. I just thought I'd help answer the questions posed in this thread with my experience.

The Sakae series of radials were amazing pieces of technology in terms of their weight in relation to their power output. It, and the similarly designed Mitsubishi powerplant that lost out to it in competition in 1939, were in large part responsible for the ultimate success of the Zero - so said Jiro Horikoshi. Since no other nation took the 'light fighter' concept to fruition as did the Japanese - nobody mass-produced comparable engines to the Sakae. Thus . . . today it's essentially irreplaceable and the performance of Zeros equipped with lesser (heavier) powerplants see their performance suffer. Now, it may be that the "suffered dramatically" opinion that originated with Nobuo Harada took into consideration fuel consumption - something that obviously would not play any role in an air show hop.

But, Jeez! Now I know why I avoid posting in forums. Put this effort into debating heath care or something.


Ron Cole

 

[ColesAircraft]

Jenisch wrote: "That was not the desire of Jiro Horikoshi with the Zero. He states in Eagles of Mitubishi: the story of the Zero figher, that lack of more powerful engines not allowed the add of armor and structural strenght and keep up with the requeriments."


The desire of Mr. Horikoshi was to meet the Navy specifications, which called for a light fighter capable of carrier deployment, long range, and extreme maneuverability. The A4M "Claude" was built with identical priorities in mind, and both envisioned aerial opponents similar to those met in China: the Russian I-16 Ratta, for example, all primarily light fighters. His book is an excellent resource - probably the best book ever written that details the development of a WW2 fighter aircraft - but he also wrote extensively for the Japanese-language magazine Koku Fan in the 1960s and '70s, where he goes into even more detail regarding the Zero's technical development.

It is true that the engine/airframe combination that was adopted in 1939 restricted the Zero when the Navy demanded heavier armament, bomb-carrying capabilities, and armor plate. I said that in my original post, and noted how, unlike the Zero, the Bf109 was better able to adapt itself.

It's also worth noting, since we're invoking pilot perspectives, that Japanese pilots during WW2 strongly preferred the lighter and less powerful A6M2-21 to any other later variant. They were coveted by units and their best pilots as their numbers dwindled. I've never heard similar claims from Luftwaffe pilots regarding the 'Emil'. This, again, bespeaks the point of my original thesis: there was a difference in philosophy regarding design and development between Japan and the West, and it still exists today. The Zero was as much a product of that as the Honda Civic Si, both dramatically different - by intent, not so much limitations - from the F4U Corsair and the Chevy Camaro.


Ron Cole

 

[Jenisch]

Japanese Army fighters had few Army-specified range requirements as a rule.

The Ki-43 Model 2 had 1,760 km of range, and 3,200 km of ferry range. The Ki-43 Model 1 (didn't found data for it) had more range, since it was ligther and with a less powerful engine. The data of the model 2 is probably with drop tanks, but even so the numbers clearly agree with Hinoki: there was a desire for long range in the Ki-43!

The Japanese would have built P-40s???

God, I didn't wrote this!

 

[ColesAircraft]

The Ki-43 Model 2 had 1,760 km of range, and 3,200 km of ferry range. The Ki-43 Model 1 (didn't found data for it) had more range, since it was ligther and with a less powerful engine. The data of the model 2 is probably with drop tanks, but even so the numbers clearly agree with Hinoki: there was a desire for long range in the Ki-43

I wrote that range wasn't a priority for the Army - not that it was never considered. And it's not "me" versus "Hinoki". Mr. Hinoki died in 1976, so I did not get to know him. But as I've studied and written about this subject since 1984, I did get to know Sakai, Satoru Anabuki (probably the ultimate "Oscar" ace), Misajiro Kuwato, Zenji Abe, Saburo Saito and others. I founded the first dedicated organization to promote the study of Japanese WW2 aircraft, JII and the Asahi Journal, in 1987 and that eventually became J-Aircraft.com. Please . . . before you regulars just assume that the new guy must be ignorant of the subject at hand - consider that I might actually know what I'm talking about, and you could stand to learn a thing or two.

I was just trying to help. I won't bother again.


Ron Cole

 

[Jenisch]

I wrote that range wasn't a priority for the Army - not that it was never considered.

And I just posted the interview of the pilot, and data of the Ki-43, both letting clear the Ki-43 was weaker structurally because the range requirement. In the case of the Zero, a notable drop in range can be constated in the models with self-sealing fuel tanks and armor of the aircraft.

To put the things in a better perspective: try built a WWII fighter with the range of the Ki-43 and specially the Zero, with power plants at around 1000 hp. Any designer in the world at the time would adopt the solutions the Japanese did. This is why I mentioned they would have aircraft SIMILAR to the P-40 and the Bf 109 - with self sealing tanks and armor - if they didn't have the range requeriment.

Mr. Hinoki died in 1976, so I did not get to know him.

As far as I know, it was in 1991.

But as I've studied and written about this subject since 1984, I did get to know Sakai, Satoru Anabuki (probably the ultimate "Oscar" ace), Misajiro Kuwato, Zenji Abe, Saburo Saito and others. I founded the first dedicated organization to promote the study of Japanese WW2 aircraft, JII and the Asahi Journal, in 1987 and that eventually became J-Aircraft.com. Please . . . before you regulars just assume that the new guy must be ignorant of the subject at hand - consider that I might actually know what I'm talking about, and you could stand to learn a thing or two.

Your personal experiences are welcomed to everyone here, but they don't have nothing to do with our discussion.

I was just trying to help. I won't bother again.

You wasn't bothering, but is clearly feeling persecuted - which is not the case.

 

[tyrodtom]

The pilot, good as he may be, didn't design the aircraft.

The stated range you give for the Ki-43 is about half of the range of a Zero. Ferry range has nothing to do with combat radius. Combat radius on a aircraft with drop tanks is how far the aircraft can fly after it gets rid of the drop tanks and engages in however many minutes of combat, and RTB on internal fuel.

Ferry range is how far you can fly on internal fuel and drop tanks, no combat. It will be a great deal more than just twice the combat radius.