STO - AIR International F-35 Special Edition July 2014
AIR International has a good special edition July 2014 on the F-35. Some info is repeated but also updated. I have not read about the two position STO throttle before - I would be interested in any comments about that aspect please. Thanks. The article is very long whilst only a few STO paras are below:
Jumping Jack Flash July 2014 unknown author AIR International F-35 Special Edition
Quote:
“...STO-ing...
...There are three ways to conduct a short take off (STO) in the F-35B: stick STO, button STO – and auto STO. “That’s a completely automated way to STO the aircraft off the flight deck. You punch in a distance and the aircraft will auto rotate to its optimal fly-out condition. It’s all based on distance: we know where the aircraft is spotted [before it starts its take-off run] and where it should start its actual rotation,” explained Rusnok. “Unlike a Harrier, which launches off the end of the ship flat, the F-35 rotates at about 225 feet from the bow, sits on two wheels until it gets to the end of the ship and actually takes off, a much different process to a Harrier. From a pilot perspective, you lose some sight of the front of the ship; in a Harrier you can see all the deck. But that’s all part of optimising a 35,000lb aeroplane to get off the ship compared to the Harrier, which is only 16,000 to 25,000lb.”
With stick STO the pilot controls the take-off by pulling back on the stick, holding it there and then rotating to the optimal pitch angle to fly off. In button STO, the pilot uses a trim switch which rotates the aircraft when pushed in, activating it when the aircraft passes the yellow STO rotation line positioned 225 feet from the bow of the ship.
“That was a temporary marking applied on the flight deck for this trial and is now being permanently installed on the ship with lighting,” explained Rusnok. “It’s based on optimising the performance of the aircraft and its flying qualities, so we can get the aeroplane off with the maximum amount of nozzle clearance and performance. The STO line is our visual cue to either pull the stick aft or hit the button; or if you’re on automated STO you should start seeing the aeroplane’s flight controls moving by the line, otherwise the pilot can intervene and pull back on the stick. We’ve never had to intervene.”
The pilot also has command of the throttle. Two power setting options are available for take-off: Mil STO and Max STO [have not read about this before], as Maj Rusnok explained: “When you taxi to the tram line you stay in mode one, the conventional flight mode. You convert the aircraft into mode four, the STOVL flight mode, and it takes about 15 seconds or so for the doors to open up and the lift fan to engage.
“Then you push the throttle about halfway up the throttle slide into a detent position at about 34% engine thrust request. It sits there and you check the engine gauges: if the readings are okay you slam the throttle to either Mil or Max position and then release the brakes simultaneously. Pushing through to max is like an afterburner detent. But it’s not an afterburner – you can’t go to afterburner in mode four.
“It’s a very fast acceleration. The closest we would spot from the bow is 400 feet, so about 175 feet before we would actually start rotating the aeroplane [at the STO rotation line]; so very, very quick.”
One of the big test points for DT I was to ensure adequate nozzle clearance in all the different test conditions. The engine nozzle swings down and back up during the take-off in accordance with inputs from the aircraft control laws.
“It’s all automated,” said Rusnok. “The pilot is not in the loop whatsoever – either they’re pushing the button and letting the aeroplane do its own thing or pulling back on the stick to help it. Monitoring systems cue when something is wrong, so you have to rely on them to keep you safe because the flight controls are being moved unbelievably quickly.”
Maj Rusnok said the take-off was very much like that ashore, with very little sink off the end of the deck. “The aeroplane is ridiculously powerful in STOVL mode. Just raw, unadulterated power.”
AIR International F-35 Special Edition July 2014
Very interesting. There must be a different mode for the ski-jump launch. Would seem the software would be a bit different as there would not be the need for that rotation before reaching the end of the (flat) flight deck. Wonder how much deck run (and wind over deck) is needed for a max load take off?