A Japanese F-35A disappeared off the coast of Japan at about 7:30 pm Japan time on Tuesday evening. The plane departed Misawa air base and went missing about 30 minutes into the flight, 85 miles east of Misawa city in Aomori prefecture, over the Pacific Ocean. 

Japan launched a search mission for the plane and pilot and in the meantime suspended all F-35A operations. Remains of the tail section of the plane have now been found – but no sign of the pilot or the rest of the aircraft.

There are 12 remaining F-35As in Japan’s inventory. All are grounded for now. The aircraft that went down was on a training mission, flying with three other F-35s.  

According to NHK, the pilot did not radio any kind of distress call, or Mayday. The pilot as described as “in his forties,” suggesting he was well-experienced.

The aircraft was the first one co-produced in Japan by Mitsubishi Heavy Industries in a partnership with Lockheed.  

The radar signature

The plane was being tracked on radar and was probably using a transponder to “light up” its radar signature. If the transponder was turned off for any reason, and provided the plane did not have an external fuel tank, or a Luneburg lens device as a radar reflector, it would have disappeared from radar coverage. 

The Aviationist reported that the Japanese F-35s are possibly being flown without a Luneburg lens, which if true means the only radar tracking possible was based on the plane’s onboard transponder, assuming as we are told that the “normal” radar signature of the F-35A is too small to be tracked by a conventional military or civilian radar set without the transponder augmentation.

Transponders are used to identify aircraft and are required for air traffic control (ATC). US military aircraft have multi-mode transponders, and probably Japanese military aircraft have the same. This gives them the ability to operate in civil and also in dedicated military air space and to be directed by ATC to avoid other civil and military aircraft. 

Like civil aircraft, military aircraft broadcast a code, usually assigned by the ATC. In addition, most military aircraft are required to have Federal Aviation Administration approval in the United States, qualifying them to operate in civil air space. Presumably, Japan follows a similar protocol.

A total and complete power failure could shut down a plane’s electronics. In commercial aircraft, there are battery backups, but whether the F-35 has such a backup, and whether the backup covers the transponder, is not clear. 

Because the F-35 probably consumes more electrical power than most military aircraft, it may be that the backup systems are limited to critical elements such as the fly by wire system and other primary controls.

A transponder can also be turned off by the pilot. One would presume that in any combat scenario, when even theoretically in range of enemy air or ground-based missiles or encountering enemy aircraft, the transponder would be switched off.

In a training exercise involving tight formations, sometimes all but the lead aircraft turn off their transponders. But in those situations, the aircraft would be in visual contact with one another – formation flying – and that does not appear to be the case in Japan’s training exercise.

So what could have happened?

1. An engine failure without battery backup to the transponder.  

If the F-35 engine fails, this heavily electronics-driven aircraft would literally fall from the sky. An F-35 crashed last year at USMC Air Station Beaufort, South Carolina, but the pilot was able to safely eject.   

That aircraft was the US Marines’ version of the F-35, known as the F-35B. Before the Beaufort crash, at least one F-35 sustained an onboard fire originating in the weapons’ bay, but managed a safe emergency landing.

In the Beaufort crash, the reason was said to be faulty fuel tubes. All F-35s were grounded pending an inspection of all F-35 fuel tubes. While not explicitly stated, it seems some fuel tubes have known problems, others are regarded as acceptable.

One would presume that the fuel tubes supplied in the engines provided to Japan for its program have safe fuel tubes. But the fuel tube issue may not be the whole problem of the F-35 engine and it cannot be ruled out there are other anomalies in the engine that have not been isolated.

2. A catastrophic fire that destroys the electrical system.  

The electrical fire “mishap” also happened at the Marine Fighter Attack Training Squadron 501, in Beaufort, South Carolina, where another F-35B was involved. The cause was a bad bracket that caused chafing in the electrical wiring. The short circuit caused a fire in the hydraulic system of the aircraft.

While it is unlikely that the bracket problem could have been at fault on the missing Japanese F-35A model, it can’t be ruled out, nor can any other kind of fire resulting from an electrical problem or even a bird strike that can cause engine disintegration and cause a fireball if the fuel tanks were punctured by engine debris.  

Concorde Air France flight 4590 on July 25, 2000, blew a tire on take-off when one of the tires hit debris on the runway. The disintegration of the tire punctured the plane’s fuel tank and started a catastrophic fire. The Concorde crashed two minutes after take-off.

At present we have little knowledge about the lost F-35A in Japan. How many hours was the aircraft operated before the plane came up missing? Were there any reports of problems with the aircraft that required maintenance?  

The big challenge for Japan is in recovering the lost aircraft, especially the engine. If found, the engine will be a definite help in assessing what went wrong. How much of the rest of the plane might be intact is not known, but the likelihood is that much of the fuselage disintegrated based on the debris seen on the surface of the sea by Japanese search and rescue teams.

3. Pilot Suicide.

In October 1999, an Egypt Air Flight originating in Los Angeles with a stop at Kennedy Airport on Long Island and heading to Cairo, Egypt, disappeared about 60 miles south of Nantucket Island. There has long been speculation that one of the pilots, Gamil El Batouti – who was at the controls – crashed the plane into the sea. El Batouti was an experienced pilot who had flown combat jets in the Six Day War and the Yom Kipper War and after became a commercial pilot with Egypt Air. Allegations that this was a suicide operation perhaps linked to terrorism have never been proved.

There have been at least seven crashed commercial aircraft caused by pilot suicides of some indeterminate kind, although one of the seven pilots had stolen the commercial jet. There have been a larger number of other general aviation crashes involving alleged pilot suicides.  

Most recently, in 2014, the disappearance of Malaysian Airlines Flight 370 led some to allege that pilot Captain Zaharie Ahmad Shah from Penang may have carried out a suicide crash, but the allegation was investigated inconclusively and there is no hard evidence demonstrating this is what happened. The aircraft has never been found.

In regard to the F-35A disappearance, we have not yet been given any information on the pilot or his state of mind.  

But a highly trained active senior fighter aircraft pilot would not seem to be a candidate for a pilot suicide and there are no reported cases of active military pilots deliberately crashing their planes.

It is vital to find out what happened to the crashed F-35A since without precise knowledge the aircraft may remain grounded, depriving Japan of front line stealth aircraft it needs to confront the worsening pattern of aggressive Chinese and Russian air and naval operations in the East China Sea. 

Japan’s older F-15s, which have been repeatedly scrambled when Chinese and Russian aircraft, including bombers and spy planes, have operated in the area, are wearing out. The F-35s are supposed to take up the slack and be the replacement for Japan’s Self Defense Forces.