Reply to post: Re: Particularly as a lot of them do test flights with large crews..playing with all the computers.

Take-off crash 'n' burn didn't kill the Concorde, it was just too bloody expensive to maintain

bazza Silver badge

Re: Particularly as a lot of them do test flights with large crews..playing with all the computers.

That said some of these were analogue computers, hard wired to take scaled voltages and currents, mash them through a bunch of operational amplifiers and drive some actuators. Good for near instantaneous response to certain parameters.

Well, you still have the group delay round the feedback loops, but that's it.

One subtle and now overlooked feature of analogue control avionics is that certification is far easier. No software. It's easy to prove an analogue circuit meets a specification both analytically and by testing. Digital is far harder, and especially so when you use digital electronics to run software...

I'll note it took 66 flights to plan the "schedule" of spike positions on the SR71. While Concorde's speed range was lower it was design to cope with "unstarts" where the inlet expels the shock wave (a potentially fatal event on the SR71 requiring immediate pilot action) automatically.

A big difference between Concorde and SR71 inlets is stability. Square sloped inlets such as Concorde, Tornado, F15, etc used are more tolerant of disturbances in the airflow into them. Maneuvering is unlikely to upset that airflow. Whereas the SR71 was all about absolutely maxing the pressure recovery (for which spike round inlets are the best), no compromises, and was much more on the edge whilst at high speed. Very exciting, if nerve wracking, ride!

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