Shiden Model 21 Shiden Kai
|Coastal Defense Ship||Destroyer|
|Light Cruiser||Torpedo Cruiser|
|Heavy Cruiser||Training Cruiser|
|Aviation Cruiser||Fast Battleship|
|Light Carrier||Standard Aircraft Carrier|
|Armored Carrier||Seaplane Tender|
|Submarine||Aircraft Carrying Submarine|
|Submarine Tender||Fleet Oiler|
|Repair Ship||Amphibious Assault Ship|
Considered one of the best Japanese planes, it was a heavily revised version of the Shiden. It was almost immediately put back on the drawing board to iron out the defects left over from the seaplane to land-based plane conversion. Such improvements include lowering the wings for shorter landing gear (also improved overall frame stability), strengthening the landing gear (the long gear caused many fatal accidents), lengthened fuselage (increasing fuel storage), redesigning the tail, simplifying the rail under the plane, 2 extra 20mm cannons on the wings (also increased ammo on all guns) and clearer cockpit visibility. The redesign resulted in a 500 lb lighter aircraft, slightly increased speed and simplified construction that also used the existing parts from the Shiden Model 11 that was currently in production. Being slightly faster than Shiden Model 11 and Raiden but slightly slower than Hayate and F6F fighters, it was adopted as the main interceptor fighter of the IJN. It was assigned to and made famous by the newly formed, most elite air group of the war, the 343 Air Group, formed by commander Minoru Genda.
- A unique Japanese invention featured on the Shiden Kai was the addition of automatic combat flaps that made it very agile and very deadly in dogfighting situations. On other aircraft, these flaps were manually controlled during turns, on Zero fighters specifically a pilot had to exert himself physically to engage the flaps. The automation freed up concentration for larger windows of opportunity to shoot at enemy planes. Veterans of Zero fighters were not too happy about them as they felt they were activated at the wrong moments but new pilots agreed it was a great advantage. Combined with its firepower and agility, it became one of the best dogfighting planes of the war.
- Although it could in theory destroy a B-29, its medicore climbing rate and high altitude speed was not exactly suited for bomber interception, but it didn't stop the IJN as the Shiden Kai was a more reliable plane than the hard to maintain Raiden.
- A few Shiden Kai were captured and tested by USN engineers after the war and found that if given high quality fuel, it would unlock the full potential of the Homare engine that could even outspeed a P-51 Mustang, demonstrating how much more dangerous it could have been if the IJN was under more favorable conditions.
- The fat frame of the Shiden Kai could easily be confused by an F6F Hellcat from afar and was on few occasions by both sides.