Kawazaki Ki-40 Tengu

The Kawazaki Ki-40 Tengu is a Yamataian carrier-based V/STOL military aircraft. The Ki-40 was developed as a naval fighter based heavily on the Chiseian for the Yamatai Imperial Navy, which was the primary user. The fighters were the first indigenous carrier-based aircraft developed by Yamatai since the Second Escar-Varunan War. The Ki-40 was later developed into the fourth-generation Kawazaki Ki-62 Tengu II, which was further optimised for carrier operations as the Imperial Navy expanded. The Ki-40 was retired from active service in 2006. Several Ki-40 aircraft were also sold to allied nations such as Shojin in the 1980s and Masuka in 2018, and remain in service in those countries.

The Ki-40s were briefly used as carrier-based aircraft on the aircraft carrier Hotaru prior to the Second Escar-Varunan War-era ship's decommissioning in 1981, replacing the older carrier-based fighters that had been purchased from Chisei and marking the first time since the Second Escar-Varunan War that the Hotaru operated with wholly Yamataian aircraft. In addition to carrier operations, the Imperial Navy positioned the fighters in coastal bases as rapid-response naval interdiction assets, taking advantage of its V/STOL capabilities to deploy the fighters outside of vulnerable airfields. After the decommissioning of the Hotaru, some fighters were also converted to operate from the, which were capable of carrying up to two fighters in lieu of the typical complement of three helicopters. The Ki-40 received criticism for having a high accident rate and for a time-consuming maintenance process.

In the late 1980s, the Imperial Navy began the Year 2000 Carrier-Based Fighter project in search of a replacement for the Ki-40 to operate from the projected supercarrier project. Kawazaki Aerospace embarked on a project to redesign the Tengu to design a fourth-generation V/STOL aircraft, resulting in the prototype of the Ki-62 Tengu II. Facing Mitsuhishi Aircraft Corporation's conventional but more capable Mi-6X, Kawazaki eventually won the contract when the supercarrier project was cancelled and replaced by the project after the 1997 Hasukuni earthquake. As the Sayashi-class design could only accomodate V/STOL aircraft and helicopters, the Ki-62 Tengu II was selected by the Imperial Navy. Parts of Mitsuhishi's Mi-6X would later be used in the project.

Operators
Current Operators Former Operators
 * Masuka: 6 aircraft in operation with the Masukan National Air Defence Force.
 * Shojin: ~30 aircraft in service with the Shojin Air Defence Force.
 * Yamatai: Yamatai Imperial Navy; Former primary operator with ~240 aircraft. Retired in 2006.
 * Meridon: Meridonian Navy; sold to Meridon as the "F4 Demon". Mainly operated by the 60 NFS.