How does the F-35B STO on a carrier?

The F-35B vertical landing procedure seems pretty straight forward. It basically glides in, engages the blower at idle, and increases powers as the airspeed declines, ending in jet-borne flight.

But how does it do short take-offs on a carrier? Does it start the take-off run with the clutch engaged (= engaging at idle), or does it bring the engine up to full thrust and THEN engages the blower? Engaging the clutch and spooling up the blower is said to take around 7 seconds (the clutch is a uncertainty factor, its behaviour isn’t constant). For a conventional plane a typical take-off ground run takes maybe 12 to 15 seconds, so enough time to engage the blower during the take-off run. (More on the question of balance below).

A Harrier on a LHD takes off in between 5 and 7 seconds. For the F-35B that would just-so enable clutch engagement and blower spool-up *during* the take-off run, having full vertical thrust when going over the edge. Of course on a LHD that would mean take-off run from way back on the flight deck.

But then the question of balance: The blower’s thrust is completly dependent on engine rpm. The main nozzle swivels in around 3 seconds. On a STO run, there needs to be a considerable forward component for the main nozzle, at the same time it has to balance the roughly 8 tonnes of vertical thrust of the blower at full rpms.

So my assumption: STO with clutch engagement under full engine power. Take-off run starts with the nozzle strait back, full power, plane moves forward. As soon as the aircraft moves, the blower clutch is engaged, vertical thrust starts to build. After about four to five seconds the main nozzle starts to swivel downwards to compensate the nose-up moment from the blower, the angle is hard to estimate, I guess around 60° downwards. The blower vanes will be angled as much backwards as possible to produce maximum foward thrust and increase airspeed, otherwise the plane won’t fly wing-borne at the end of the take-off run. Then the blower is disengaged, and the main nozzle slowly swivels into the horizontal. One thing that helps is that the blower still provides thrust during spool-down, till the flaps close.

It will be quite interesting to see what moments and vibrations the engagement/disengagement under full rpms will cause. All in all very inflexible.

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