Maintenance Lapse Identified as Initial Problem Leading to Lion Air Crash

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Salute FCeng!
Taking a rest now, but I have to clarify my definition of FBW for you and others to ponder. I take a harsh position concerning "augmentation" versus pure FBW. The Airbus inplementation is the closest system to what I flew, and even it has a control cable or two for one control surface. It also is a gee command, albeit biased by pitch and roll attitude. Still the closest system to the F-16 and shuttle.

Well before the Viper prototype we had the A-7D "control aug" component of our flight control system that used transducers in the stick control grip to talk to the autopilot. It did this when we did not have autopilot engaged, so-called "manual", but used the autopilot connections to move ailerons and elevator. On my FCF flights I would hold the stick between by legs and simply twist/tilt the grip to bank and pitch. It was functionally FBW, but not really.... heh he. What it did was allow very small, sensitive inputs to the pitch and roll control surfaces using minimal actual movement of the stick. It also used "inertial" sensors that I never bothered to locate, and assumed were in the autopilot hardware. The result was control surface movement when you had your hand completely off the stick! You could tell if the guy in front had "control aug" on because the ailerons and elevator would be twitching on every bump in the taxiway. This characteristic was very evident in the Viper, and you can even see it in the AB 320series. For we "light" types, it made for super close formation flying and very nice ILS approaches following the HUD and/or ADI steering bars. From what I have learned the past two months about the 737 is that even tho the pilots call it flying "manual" the plane still has Hal "helping", as in the STS system. And now the MCAS.

Other than some "x" planes and the captured saucer at Groom Lake, we had the first true FBW in the YF-16, although I beleive at the time the X-15 was pure FBW, and the shuttle was being developed with pure FBW. I cannot emphasize enuf, and have repeated over and over, there were zero mechanical connections to any control surface, period. Constant hydraulic pressure was supplied to the integrated servo actuators and electrical commands moved the small valves in the ISA's. If the electrical connections were gone, then we only had the nylon letdown. A few years later we saw the Enterprise glide down to the strip at Edwards, and it had zero mechanical connections of any kind to the control surfaces. We also saw a few test articles that did away with the hydraulic connection to the ISA's, and had pure electric jets. I dunno what they did with that saucer over near Wendover.

With respect to the point about "augmentation", it looks like we are defining terms and design features. My community used the term FBW meaning no mechanical connections., only electrical signals to the actuators regardless of them being electrically powered or using hydraulic pistons. The only FBW mode I have seen in any plane that has negligible "augmentation" is the "direct" law found in the ;bus, where stick position is turned into control surface position with minimal or little regard for dynamic pressure ('q") or other variables. It is entirely possible to have a functional FBW system with a surface movement corresponding to a stick position or pressure using a fixed "gain" - e.g. 30 degrees of deflection moves the aileron 10 degrees. No problem, and you see this every day with home hobby drones and high perforemance RC planes. However, that implementation is relatively coarse and can easily be "augmented" by bringing into play body rates, dynamic pressure, Aoa, gee and attitude. As with the 'bus, you can get a plane to feel really good and easy to put where you want it to go. The Viper was like that, and the interaction of all those variables came into play. For example, left/right pressure ( mainly pressure, but stick moves less than a eight of an inch) commands roll rate, not aileron deflection. Hal looks at dynamic pressure and AoA and ......, then commands the ailerons, rudder and the independent horizontal stabs to move at "x" rate to "y" degrees in order to result in commanded roll rate. The damned thing is like a video game except for the 9 gees and bouncing your head off the canopy when rolling too sharply.

I personally liked the "augmentation" in the Sluf, and I cannot imagine what a nightmare the Viper would have been without variable gains and rate functions, not to mention AoA inputs.

Thanks for all the tech stuff, FCeng, and we'll see each other later for sure..

Gums sends..