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Old 23rd May 2011, 23:44
  #2213 (permalink)  
Join Date: Jun 2009
Location: florida
Age: 77
Posts: 1,135
the "rest" of the story - F-16 FBW mods


To avoid further dispersions as to why a few military would dare to tread amongst this august group of heavy pilots and experts, I'll conclude the story about our development of the first operational FBW system AFTER it was deployed and flown for a few years. My goal all along has been to provide some perspective concerning new concepts and their implementation with a first-person account.

Once we discovered that we could enter a deep stall and had no way to recover, things got serious.

- We transferred fuel forward shortly after takeoff. About 1200 pounds if memory serves. This helped our c.g., hurt our pitch rate, and led to some unintended consequences after landing if we forgot to "re-balance" on the way home.

- We added the pitch override switch to bypass angle of attack limits used by the computer..... well, almost. The switch was not active unless our AoA was above 29 degrees or so. Considering the deep stall was at 50 - 60 degrees AoA, no problem.

So we could control the horizontal tail surfaces "directly" in proportion to stick inputs.

- Developed a bigger tail. So we added a few square feet to the stabilators. This moved the aero center of pressure slightly aft, but most importantly, it gave the computers more control surface area to work with. Also gave we dumb pilots better control at slow speeds. We then quit transferring fuel, as the procedure was a kludge and had some unintended effects upon pumps and after-landing characteristics.

- We added a new control law called Category III. Named after our external loadout, which was impressive compared to the basic air-to-air configuration. The new law limited AoA and roll rate. This helped to avoid entering a departure induced by the inertia and aero effects of all that crapola hanging on an otherwise pretty jet.

Bottomline: Our engineers and USAF admitted that we all could have done better anticipating "upset" conditions or outright stupid moves. The system worked exactly as it was designed. Sound like a PR release or rumor from last week?

The flight test folks and GD came up with a great mod and it has served us well for 30 years.

we now return to our regularly scheduled hypothesis cacaphony.

Old fart with no airline experience
Familiar with many planes
Extremely familiar with early operational FBW systems
Extremely concerned with flying in a safe, well-engineered airliner
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