About F-35C Control Laws Now and Possible Future + HMDS II Landing Aids (only some excerpts below)
Tailored to Trap 01 Dec 2012 Frank Colucci
http://www.aviationtoday.com/av/military/Tailored-to-Trap_77964.html"F-35C control laws give Navy pilots Integrated Direct Lift Control for easier carrier landings, and they open the door for future landing aids."...
"...Even with its innovative flight controls, the F-35C, from the pilot’s perspective, is relatively conventional coming aboard the carrier. “Determining where you are with respect to lineup and glideslope is all visual,” acknowledged Canin. “For lineup, you look at the ship and line up on centerline… easy enough if the ship’s heading is steady, but tricky if the ship is wallowing,” noted Canin. “As for glideslope, you have to watch the meatball and see small deviations. Then you have to put the ball back in the middle, with the right rate of descent so it stays there. None of that’s changed with this airplane, but what we’re giving the pilot is more responsiveness and bandwidth to do that.”
The F-35 uses a BAE Helmet Mounted Display (HMD) instead of a conventional Head-Up Display (HUD). Like a classic HUD, the HMD shows the pilot a flight path marker (or velocity vector), with a bracket to indicate if the aircraft is “on speed” or flying fast or slow. Meanwhile, a caret moves up or down in reference to the flight path marker to give an acceleration-deceleration cue.
Ashore, when the aircraft is on glideslope, the pilot simply puts the flight path marker by the meatball and the aircraft stays on that glideslope. “At the ship, since the landing area is moving through the water, the pilot needs to put the flight path marker out in front of it. He needs to put it where the landing area will be when he gets there, which again requires judgment. A better system would be put the velocity vector into the moving reference frame of the boat,” Canin said.
Though not currently part of the F-35 plan, implementing a “ship-referenced velocity vector” (SRVV) would allow the pilot to put the SRVV on the intended touchdown point to hold glideslope. “All we would need to know from the ship is its current velocity, so we can put the airplane symbology in that reference frame,” Canin said. Readily rewritten control laws have other possibilities. “With the current flight control law, the pilot commands pitch rate with the stick, and uses that pitch rate to establish a glideslope,” noted Canin. “There’s no reason, though, why the flight control system couldn’t establish a baseline glideslope, and allow the pilot to apply control stick pressure to command tweaks around that glideslope in response to ball deviations.” A “glideslope command” mechanization of this sort is not in the baseline airplane now, but is an example of the type of changes that could relatively easily be incorporated in the F-35 control system....
...The JSF test program currently has no autolanding requirement, but plans call for an F-35C autolanding capability based on the Joint Precision Approach and Landing System. “The F-35 will take more of a self-contained approach — an internally generated glideslope from GPS.”
IDLC is just one part of the F-35 test program which will now include tests of a refined tailhook for arrested landings. “We look at approach handling qualities every chance we get,” said Canin. “Where the rubber meets the road, though, is at touchdown. Until recently we haven’t had a loads clearance that allowed us to do carrier-type landings, but now we do, so now we’ll be able to look at our control precision to touchdown.”
Canin concluded, “Carrier landings, particularly at night, are still considered to be the hardest thing to do in aviation. But I think we now have an airplane, and the people in our control laws group, that can kill that notion forever. The carrier approach is a very well-defined problem, and there’s no reason why this airplane can’t completely change the game.”"
GRAPHIC ADDITION - SRVV Ship Referenced Velocity Vector example from:
Paddles Monthly August 2011
‘What the Future Beholds...’ Dan "Butters" Radocaj Test Pilot/LSO VX-23 Ship Suitability
http://www.hrana.org/documents/PaddlesMonthlyAugust2011.pdf“...We may also need to add another lens-type glideslope indicator. One idea is called a Bedford Array. You can see in Figure 1 that a Bedford Array is like a lens spread of over the length of the LA. Unlike an IFLOLS which has 12 cells that are always on to create a glideslope reference, the Bedford Array is a set of Christmas lights and only the light corresponding to current position of the touchdown point is illuminated. Just as the dynamic touchdown point moves across the deck on the LSODS screen, the Bedford Array lights would “move” forward and back across the deck corresponding to the dynamic touchdown point. Figure 2 shows what your HUD may look like. You keep the
ship stabilized velocity vector on top of the Bedford light that is illuminated. The datum is a reference line in your HUD.
As long as the 3 all line up you are on glide path. A Bedford Array & a ship stabilized velocity are indicators of glide-slope that will show you if you are off glide-slope more precisely but they still don’t make the airplane respond differently....”
