N1K2-J Shiden-Kai Performance

[Laurelix]

There are many misconseptions and confusions regarding the real performance of this fighter. If you look at the Specification of performance of IJN Fighters table from 10th september 1945, or US TAIC for George 21 or sources like Francillon. They all state the Performance of the N1K2-J was 595km/h at 5600m and 7:22 to 6000m rate of climb.

But they are wrong. Its not feasable and my only explanation to those performance figures is if it had a big external fuel tank under its fuselage which wasnt uncommon for it to mount.
Why are these figures not believable?
N1K2-J has 3800kg loaded weight and a Ha-45-21 (1990hp engine)
Ki-84 has 3600kg loaded weight and uses the same Ha-45-21 (1990hp engine)

Ki-84 with Ha-45-21 had top speed of 674km/h (687km/h according to US TAIC calculations)
It could climb to 6100m in 5:48 (from US TAIC)

There is literally only 200kg weight difference between the two planes and we can see such huge difference in the rate of climb, nvm the top speed. Why would this plane with much better power to weight ratio compared to an A6M3 have a rate of climb worse compared to an A6M3? It makes no sense. Those performance figures just have to be with external fuel tank adding drag and the weight of it is definitly over 3800kg.

So then if they are wrong, what is the real performance of the Shiden-Kai?
Well luckily the N1K2 manual exists.

On the first image youll see a left and a right hand side with performance figures.
On the right hand side are the actual japanese flight tests results on the Prorotype N1K2-J which was using derated Ha-45-21 since the engine was suffering issues at the time. It achieved 611km/h at 6000m at military Power and it could climb to 6000m in 6:20 at military power. On the left hand side are the japanese estimated performance values for N1K2-J once the engine is running at its full 1990hp power setting, however its overoptimistic since the engine didnt have as much power at 6000m as they thought it would. They estimated 644km/h at 6000m at military power and 5:15 to 6000m at military power. The actual performance would be about 628km/h at 6000m at military power and 5:30 to 6000m at military power. At WEP the top speed would be about 652km/h

As you can see now it actually looks believable.
Top Speed: (WEP)
N1K2-J - Roughly 652km/h
Ki-84 - Roughly 672km/h

It's unsurprising the final result shows only 20km/h difference in top speed between N1K2-J and Ki-84 when both are using full power Ha-45-21 (1990hp) engine because
N1K2-J with de-rated Ha-45-21 engine achieved 611km/h at 6000m whilst Ki-84 with the same de-rated engine achieved 631km/h at 6000m at Military Power.

Note:
Taic used calcaulations to state Ki-84 top speed. the drag coefficient is a bit overoptimistic. I used the japanese Ki-84 manaul which states 624km/h at 6000m at military power top speed using the Ha-45-11 (1800hp) engine which is what the early Ki-84's had. 1460hp at 5700m = 624km/h at 6000m. With 1625hp at 6000m using this same drag coefficient gives you about 648km/h. At WEP youre looking at about 672km/h

—————————-

N1K2-J Shiden-Kai

Empty Weight: 2650kg
Loaded Weight: 3800kg
Wing Area: 23.5m2
Engine: Ha-45-21
WEP: 1990hp at Sea Level
Military Power: 1825hp at 1750m / 1625hp at 6100m

Max Speed: (Military / WEP)
Sea Level: 529kph / 550kph
1000m: 551kph / 574kph
2000m: 574kph / 597kph
3000m: 597kph / 606kph
4000m: 599kph / 603kph
5000m: 603kph / 628kph
6000m: 628kph / 652kph

Rate of Climb: (Military / WEP)
Time to 6000m: 5:30 / 5:06

Stall Speed: (Sea Level, No Flaps, 3800kg)
158km/h IAS

Sustained Turn Time: (360 horizontal turn, 1000m, No Flaps)
Military Power: 18 sec
WEP: 17 sec

Firepower:
4x 20mm Type 99 Mk 2 (225 rounds per gun)

 

[Schweik]

How about turn times?

 

[Laurelix]

How about turn times?

Sustained horizontal turn time at 0-1000m, no flaps:
Ki-84: 17 seconds
N1K2-J: 17 seconds (closer to 17.5)

 

[Schweik]

Estimates or from manual?

Maneuvering flaps are a big deal on the N1K2 right? Any idea how much that affected turn rate?

Also, do you have stats handy for the original N1K float plane fighter? The later non-float version is so popular that is all i can ever find but I'm interested in seaplanes and would like to know the stats for that one as it's probably the best seaplane fighter of the war, or certainly in the top 3.

 

[Laurelix]

Estimates or from manual?

Maneuvering flaps are a big deal on the N1K2 right? Any idea how much that affected turn rate?

Also, do you have stats handy for the original N1K float plane fighter? The later non-float version is so popular that is all i can ever find but I'm interested in seaplanes and would like to know the stats for that one as it's probably the best seaplane fighter of the war, or certainly in the top 3.

they are calculated but 17 sec is also whats stated in Ki-84 manual

 

[Schweik]

I got to see a Shiden Kai in the Pensacola Naval Air Museum a few weeks ago. Beautiful aircraft.

 

[Laurelix]

I got to see a Shiden Kai in the Pensacola Naval Air Museum a few weeks ago. Beautiful aircraft.

Both of these fighters have butterfly flaps. However whilst flaps help in intial turn, they dont improve the sustained turn rate because they create more drag and thats bad for the sustain.

Where N1K2-J has the advantage is that it had automatic combat flaps system which used mercury and it automatically set the flaps in ideal postion to give the plane the ideal and efficient improved turn performance. So Ki-84 pilot would constly have to play with his flaps during combat, the N1K2-J pilot didnt need to worry abiut it at all, it was all done for him.

 

[Laurelix]

Im not sure if Ki-84 had it but N1K2-J and late models of A6M5 also had automatic fire extinguisher system built in. On this F6F gun camera footage shooting an N1K2-J you can see the effectiveness of it. You can also see the external fuel tank mounted at the bottom of its fuselage as i mentioned at the start of the post.

 

[Ivan1GFP]

Hello Gentlemen,
There is also a Shiden-Kai at NASM Udvar-Hazy and we see it pretty regularly. It is a pretty big aeroplane.
My own belief is that N1K2-J was probably a bit faster than the numbers you are listing and the Ki-84 is just a bit slower.
There are other aspects that differ between the two aircraft that might make a difference in speed.
The propellers are different, the N1K2-J is noticeably fatter, the cowl is much cleaner on the Ki 84.

There was a long-running discussion about the speed of the Ki-84, when the reports came out, and when one was actually test flown. The first estimates of Ki-84 performance were with drag estimates from Ki-43 and just switching engine power, so they were not likely to be exact.

The N1K2-J didn't actually have "Butterfly Flaps". They were simply Fowler Flaps.

Be careful about comparing engine power between the two aircraft. They are very close, but not exactly the same. The notes by TAIC list slightly different numbers which I presume are due to differences in the induction system.

- Ivan.

 

[Laurelix]

Hello Gentlemen,
There is also a Shiden-Kai at NASM Udvar-Hazy and we see it pretty regularly. It is a pretty big aeroplane.
My own belief is that N1K2-J was probably a bit faster than the numbers you are listing and the Ki-84 is just a bit slower.
There are other aspects that differ between the two aircraft that might make a difference in speed.
The propellers are different, the N1K2-J is noticeably fatter, the cowl is much cleaner on the Ki 84.

There was a long-running discussion about the speed of the Ki-84, when the reports came out, and when one was actually test flown. The first estimates of Ki-84 performance were with drag estimates from Ki-43 and just switching engine power, so they were not likely to be exact.

The N1K2-J didn't actually have "Butterfly Flaps". They were simply Fowler Flaps.

Be careful about comparing engine power between the two aircraft. They are very close, but not exactly the same. The notes by TAIC list slightly different numbers which I presume are due to differences in the induction system.

- Ivan.

Nah US Horsepower for Ha-45-21 doesn't match Japanese. That's for both Ki-84 and N1K TAIC.

 

[Ivan1GFP]

Nah US Horsepower for Ha-45-21 doesn't match Japanese. That's for both Ki-84 and N1K TAIC.

Not quite sure of what point you are trying to make. The Ha-45 / Homare engine was used on quite a few Japanese aircraft and captured examples for bench testing would not have been all that hard to get. The US had at least two or three Ki 84 brought to the United States. One was tested pretty extensively at Middletown Air Depot in PA.
I uploaded the report on that test a couple years back.

The US also captured a number of flyable N1K2-J. The ferrying of the last aircraft under US fighter escort was described in Genda's Blade.

I would say that the US documentation at least on the engine output is probably pretty accurate for a repaired example of the Ha-45. Remember that these TAIC guys probably had better access to captured manuals than we do today. Do you have a more reliable source?

- Ivan.

-

 

[CORSNING]

Sustained horizontal turn time at 0-1000m, no flaps:
Ki-84: 17 seconds
N1K2-J: 18 seconds

Just an FYI, N1K2-J turn time at 4,000 m. is also 18 seconds.

 

[CORSNING]

From the USAF museum in Dayton, Ohio, USA.

 

[CORSNING]

they are calculated but 17 sec is also whats stated in Ki-84 manual

17 second is probable, but I would really like to see the page in the manual
that states this figure. I have never seen a turn time published in any Japanese
aircraft manuals.

 

[Laurelix]

17 second is probable, but I would really like to see the page in the manual
that states this figure. I have never seen a turn time published in any Japanese
aircraft manuals.

I can only copy and paste someones english translation of it:

A translation of a Ki 84 test:
"A function and the handling of Ki-84 fighter. 3rd January 1944 (Showa 19).

Chapter1 - Main Specification

Section 1 - Main Specification
This plane is All metal low wing single seat monoplane, here we have a spec:
Wingspan - 11.238m
Length - 9.870m
Height(horizontal) - 3.385m
Wing area - 21 m2
Dihedral angle - 6.0
Aspect ratio - 6.08
Flap area - 2.436 m2
Aileron area - 1.376 m2
Horizontal stabilizer area - 3.079 m2
Elevator area - 1.074 m2
Vertical stabilizer area - 0.761 m1
Rudder area - 0.889 m2
Empty load - 2712 kg
Full load - 3763.5 kg
Wing loading - 178kg/m2
Powerloading - about 2.5kg/hp
Fuel - Aviation 92 gasoline ( 697 l )
Methanol and Water - 130 l
Engine oil - 50l (Full capacity 80l)
Armament - 20mm x2, 13mm x2

Engine
Name - Ha-45
Type - Air cooled twin row radial 18cyl
Output - 1500hp/8500m

Propeller
Name - "Pe-32" electical constant speed propeller
Diameter - 3.10m

Max speed - 624km/h
Climb time - 12min 16sec to reach 8000m
Service ceiling - 11000m
Landing speed - 140km/h


Chapter 2 - Construction Functioning

Section 1 - Aircraft

�@�@ Subsection1 - Aerodynamic characteristics
1.Wing
The wing is capable of sustaining speeds of about 700km/h. The wing`s square shape is considered for stall and stability, contraction ratio 1.81 straight downhill tapered. To improve stall characteristic, as tip border to prevent early stall of wingtip we added 2 degree of twist down.

2.Tail
Vertical and Horizontal stabilizers both have thickest point at 40% chord length. The stabilizer area and position of balance is decided by consideration to the stability at high altitude and stability when controlling the flap.
The movement of horizontal stabilizer is mouted above the fuselage and angled + 3 degrees to improve the angle of attack against the draft from main wing.

3.Fuselage
The maximum width is decided from the engine`s diameter 1.180m, it is tapered smoothly to the tail.
Overall the shape of fuselage is shaped with simple curve, unlike straight shape so it can reduce drag.

4.Rudder
The chord length of ailron`s back is reaching 20% of main wing, its balance is 25%. controllable angle is 15degrees down, 20 degrees up.
Elevator is decided considering to the effectiveness at landing and takeoff, controllable angle is 30degrees for pull, 20 degrees for push, also have trim.
Rudder is decided considering to the effectiveness at takeoff, controllable angle is 30degrees for left and right.

5.Flaps
To improve the landing and takeoff performance of this plane which have high wingload, this plane is designed to use butterfly flap effectively enough to improve lift. The control angle of flap is 15degrees at takeoff, 30degrees at landing, Here we have the estimated maximum lift coefficiency:

Flap angle 0 degree: Max lift coefficient 1.46

Flap angle 15 degree: Max lift coefficient 1.70

Flap angle 30 degree: Max lift coefficient 1.92

Section 2 - Structure

1.Wing
Wing is all metal one side held single frame monocoque constructed, it have single wing, and its wingtip and cranial border tank can be dismounted.
For the center part of wing, it have 217L fuel tank, left and right wing have 173L fuel tank each, also split by 20mm cannons its outer cranial border it have 67L fuel tank.
Center wing cranial border have landing gear inside.
Ailerons are constructed with metal frame and fabric outer, it is perfectly balanced by counterweight placed on cranial border, and it have a correction rudder.
Flaps are fully metal constructed and it actuates by hydraulic, only used at takeoff and landing.

2.Tail stabilizers
Both the vertical and horizontal stabilizer are all metal construction.
Elevators are constructed with metal frame and fabric outer, and it have a metal constructed correction rudder. And it is perfectly balanced by counterweight placed on cranial border.
Rudder are also constructed with metal frame and fabric outer. And it is balanced by counterweight placed on lower cranial border. and it have a correction rudder on its caudal border.

3. Fuselage
It is metal constructed half monocoque construction, it can be separated into front and back part at 9th semicircle from the back of the seat.
Frontal fuselage is connected to wings by its lower mount base, and it have a pipeframe weld engine mount on front.
On the back of the cockpit the 12mm steel board is mounted to defend from bullet, and canopy have a emergency opening device.
It have a meintenance hatch on the bacl left side of the fuselage.

4. Landing gear
Main landing gear is completely retracted inside the wing`s cranial border by hydraulic, also it is fixed by hook at both the completely retracted and extended position.
Gear tower have a air/hydraulic absorber, it have a wheel and 650 x 170mm high pressure tyre. Brake is hydraulic.
Tail wheel have air/hydraulic absober tower, wheel and 200 x 75mm tyre, it can be both in fixed ...

1.This plane can perform each special flight easily, it doesn't have any bad characteristics.

2.Quick turn or roll maneuvers (such as quick roll, spins, etc) would give bad effect on the plane so it shouldn't be performed.

3.Oil pressure will be zero when at inverted flight, so do not try the inverted flight.

4.When pulling up on highspeed, the acceleration have to be within 4G.

5.When trying the special flight, because of this plane`s characteristics, try to always keep the altitude and speed before starting.

6.Because for being kind to the engine, do it on 2600RPM when at training.

7.With exception for when deep (vertical) dive, elevator tab should be in cruise mode.

8.Spin characteristic is good, and it doesnt enter to bad spin. When you`re at the spin, it will stop immediately if you place all rudders in neutral position.

9.To perform a loop, start at the speed of 400km/h, 2600RPM, Manifold pressure (+)100mmHg.

10.The point for chandelle is same as looping.

11.To perform a Immelmann turn, start at the speed of 400km/h, 2600RPM, Manifold pressure (+)200mmHg.

12.When at upsending invert roll , from the speed of 350km/h, rise in the angle of about 80degrees, open the Manifold pressure till (+)100mmHg, when you reach 150~160km/h start them as the usual process.

13.To perform slow turnover, switch the "pitch lever"to 2600rpm and keep the speed at 250(300)km/h and start them as usual process. The altitude loss is about 900m and the speed when returning at horizontal would be about 400km/h

14.To perform quick turnover, switch the "pitch lever"to 2600rpm and keep the speed at 250(300)km/h and when pulling the stick enough to the left(right) back, simultaneously stomp the rudder to left(right) enough and heading the nose swiftly to lower side, try not to invert the plane. The altitude loss is about 650(800)m and the speed when returning at horizontal would be about 350(400)km/h

15.To perform slow roll, try them from 2600RPM, speed 320km/h and start them as the usual process.

16.To perform quick turn, try them from 2600(2900)RPM, Manifold pressure (+)100mm Hg(+250), speed 380(400)km/h and start them as the usual process. left turn will force the nose down easier because of torque effect, right turn will force the nose up easier. When you keep turning, the speed defers by its tilt, horsepower, plane`s load, etc. The turn radius and time is as follows:
800~700 Altitude
360 degree 180degree Turn
Right Left Right Left Turn heading
20.00sec 17.05sec 8.55sec 9.15sec Turn time
260m 260m 260m 270m Turn radius(about)
2900RPM, Manifold pressure (+)250mmHg Notes

17.To perform quick ascend, you need a slow 3G to do this. If pull up were too rough, it will drastically decrease your gaining speed and lose your gaining altitude so be careful. So when you keep 2900RPM and maximum intake pressure when climbing, you can gain almost same climb as the descending altitude.

18.When diving in deep angle, do not over-use the elevator tab(trim?). The push for stick will be related against the speed and inversed getting heavier against the dive angle but, unless it is required you have to keep the tab within 5 degree down. When performing a dive, you have to take enough altitude and increase your speed slowly so you can learn enough, and then dive deeper within the limit speed. Here we have a sample for the deep dive.
-1.Entering
Start roll and dive with angle of 60degree, tab down 5 degree, Altitude 5000m, 2900RPM, Manifold pressure(-)100mmHg, Speed 350km/h
-2.While diving
Open the Manifold pressure up to (+)250mmHg
-3.Pulling back to horizon
Altitude 1300m, 2900RPM, Manifold pressure(+)250mmHg, Speed 750km/h

Note.
-1.Do not overrev the props unless when malfunctioning.
-2.Close the gas valve controller for about half
-3.Elevator tab are required to check severely before piloting.
-4.If the plane starts to vibrate when diving, full close the gas valve control and slowly pull up.

19.Vertical dive have to be done with the process of dive and these cautions. The speed increase when vertical diving is very fast and altitude loss required for pull-up is big so it need with caution.
Here we have a sample for vertical dive.
-1.Entering
Altitude 5000m, 2900RPM, Manifold pressure (-)100mmHg, Speed 300km/h
-2.While diving
Open the Manifold pressure up to (+)250mmHg
-3.Pulling back to horizon
Altitude 1300m, 2900RPM, Manifold pressure(+)250mmHg, Speed 750km/h

 

[CORSNING]

It is very odd, the 180 vs. 360 degrees of the turn do not seem logical.

Right: 8.55 / 20.00
Left: 9.15 / 17.05

 

[Laurelix]

It is very odd, the 180 vs. 360 degrees of the turn do not seem logical.

Right: 8.55 / 20.00
Left: 9.15 / 17.05

I think it's same with the BF-109. Something to do with the torque of the engine spinning one way. Dunno...

 

[Schweik]

A lot of planes turn quicker one way than the other, due to torque, but I'm not sure that's what he meant.

 

[Ivan1GFP]

I believe Corsning is making the observation that engine torque tends to create a tendency to pull to the LEFT at low speeds such as during a turn. To pull in the other direction is a bit odd.

 

[Schweik]

I don't know about this particular aircraft but not all WW2 aircraft engines rotated in the same direction