Originally Posted by
M2dude
VOR/LOC mode was even designed to capture a radial at Mach 2, where VOR course set error was modulated as a function of Mach number. What the designer was thinking of here is anyone's guess
I've wondered about that too....
I was part of flight test support at Fairford ('69 to '74) for the AFCS.
A LOT of time was spent (dare I say wasted) on exploring the full range of speed and capture angles for the VOR mode, and 'tweaking' the control loop parameters. With time constants in the tens of seconds, and each capture test taking minutes, I hate to think how many hours of test flying that took up in the end.
It was only later that I discovered almost nobody ever used VOR mode (not only not on Concorde, but elsewhere too) because of its inherent lack of precision!
Pilots would use TRK/HDG mode, display VOR on the HSI, and then made slight adjustments to the track or heading setting to stay on the desired VOR radial.
LOC of course was a different story.
And a small 'joke' on the same subject... because of all those big time constants in the lateral autopilot computer, it took about eight HOURS to test ONE computer on the ATEC (automatic test). Turned out the automatic test program slavishly followed the manual test specification, with each function tested separately and sequentially. I was given the job of doing something about it.... by doing a lot of the tests in parallel, I managed to bring the testing time down to one hour.
CJ
PS We (Elliott/SFENA) designed the electronics, but the original functional design spec was of course Sud/BAC, not us. And yes, me too, I never quite understood what they were thinking about...