Sunday 16 December 2018

Nipponki '46 - EK-2 Experimental Single-Seat Destroyer

EK-2 Experimental Single-Seat Destroyer

Engine: Ryusei GV twin-row 18-cylinder radial
Max output: 3000hp with 4-step supercharger
Propeller: EK-P-1 constant speed, variable pitch, changing electrically, with full feathering and cuffs (propeller cuff : a fairing of suitable airfoil shape used to cover the shanks of propeller blades in order to reduce the aerodynamic losses - MW)
                     Max. speed: 712km/h
                     Cruising speed: 670km/h
                     Landing speed: 150km/h
Range at cruising speed: 2800km with drop tank
Ceiling: 1600 m (???)
Climbing at 1000m in 40sec
Wing area: 17sqm
Weight: 2669kg
Wing load: 157kg/sqm
Armament: 2 X 36mm cannon in the fuselage
                   4 X 20mm cannons in the wings
1. The radial engine is placed in the centre of gravity for better balance. The propeller is driven by an extension shaft for better cooling (???).
2. Although difficult for mass production the wings are tapered.
3. Twin flaps
Designed by: Sekikawa Eijiro from Kobe 
Featured in the June 1943 issue of "Hiko Shonen" (Airplane Youth)         

At first glance it looks like a very interesting combination of the Supermarine Spitfire and the Bell P-39 Airacobra. Quite intriguing as a proposal but things get bizarre with the radial engine choice. Radial engines placed that back in the fuselage and with a completely enclosed nose create huge problems with cooling.
Similar designs would be:
1. the Republic XP-72, with common features like the supercharger, the extension shaft for the prop and very similar armament
and is almost identical in concept with the
An unusual design that does not look Japanese at all and would have been much more straightforward with a liquid-cooled engine. Let's not forget the various problems "Raiden" had with the placing of the engine further back in the fuselage and the need for a fan for cooling. 


Michael Thurow said...

The way the nose cowling is shaped you would definitely expect massive problems with engine overheating. But let's not forget that there were no high-powered workable in-line engines in Japan at this time.
It's interesting to note the P-47M and N versions surpassed 700 kph even with their relatively blunt noses thanks to turbo-supercharging and laminar flow wing profiles - developments which were also in only a fledgling stage in Japan.
Great series, George - please carry on.

Anonymous said...

It is a common misconception that radial engine planes have poor drag coefficients, but that is not the case. A properly designed cowling can give a radial engine fighter as good aerodynamic qualities as any inline fighter, and the lack of air scoops for a radiator reduces drag even further. The P-47 and Corsair had drag numbers as good or better than other inline fighters of day. Japanese fighters also had minimal drag.

Wind Swords

Arawasi said...

I agree. The effort in this design is to reduce drag in the nose but this comes with a price. Large air intakes are needed to cool the engine as shown in all the similar US, British and italian designs which actually create even more drag and meriad other problems.
So, as Winds points out, a cleverly designed "traditional" cowling would offer less drag and complications
The liquid-cooled engines is another solution but not without their own cooling challenges. The Ki-64 with her water evaporation cooling system on the wings is a fine example.
Thanks guys. More coming up.

D. Chouinard said...

Yes, the engine placement is a bit odd on this one, especially for a radial. The location is very close to the cockpit thus leading to a very hot pilot, a problem for the prototype Fw-190.

Michael Thurow said...

For radials let's no forget the additional thrust from the heat emissions through a well constructed cooling flap blending, e.g. on the F4U, the Fw 190 and several Japanese fighters. Liquid radiators created thrust augmentation, too, but not at the same high air travelling speeds.
The relatively low drag coefficients of the F4U and P-47 resulted not only from good cowlings but mainly from smart wing construction.