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Old 14th May 2011, 13:30
  #1331 (permalink)  
gums
 
Join Date: Jun 2009
Location: florida
Age: 77
Posts: 1,141
Salute!

Nuts is onto the original reason I joined the fray here two years ago.

Having flown the first "operational" full FBW system, I was a non-volunteer test pilot, as were all of us in those days ( 1979 and a few years thereafter). We only had a few hundred flights by then, and most were by Edwards "golden arms" and highly experienced fighter pilots. When we increased the sortie rate by an order of magnitude, we discovered flight conditions unforeseen by the engineers and the "golden arms". So we were flying several hundred flights a month versus the several hundred flown from 1974 to 1979 during F-16 development and testing.

We clever pilots can find ways to "beat the system". We can do things that the engineers and others never envision ( see Perpignan, for example, or the first crash with a high-time pilot making a low pass for public relations). Then there are actual flight conditions that the engineers have not planned for with all their control laws, limiters, reversion sequences.

Let's face it. The Viper has an operational envelope that waters your eyes compared to the 'bus. We had and have different priorities on our flight control logic, and gee was the easiest to implement. It was and still is the aero that causes problems. Our great engineers never envisioned us zooming up at extreme pitch attitudes, then trying to roll at max rate below 150 knots or so. NOBODY DID THAT!!! Simply because they couldn't until then. So now we have a jet that feels good, handles better than anything flying and we get spoiled. We "go where no man has gone before", heh heh. Hence, we discovered that exceeding the flight control laws wasn't all that hard. Especially with respect to the AoA protection. Then we discover that at 50 or 60 degrees AoA that we run outta nose down pitch authority. Well, hell Kemo Sabe, what are you doing at 50 deg AoA? The limiter was supposed to keep you from exceeding 25 degrees. So see the Code One article and read what we discovered and how to get outta a bad situation.

So my personal observation is that this accident will be found to be in the category of "unplanned flight conditions", possibly complicated by one or two sensor failures.

I also see a few modifications coming for the 'bus control laws. It's digital, right? So not a lotta hardware needed, just some good flight tests with modified control laws/reversion sequences.

Last edited by gums; 14th May 2011 at 14:39.
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