Re: Strange 727 Flight

From:         weiss@hurricane.SEAS.UCLA.EDU (Michael Weiss)
Organization: School of Engineering and Applied Sciences, UCLA
Date:         10 Jul 93 02:01:45 PDT
References:   1 2
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In article <airliners.1993.482@ohare.Chicago.COM> (Robert Dorsett) writes:
>It's ATC's responsibility to maintain separation in IFR: they'll clear 
>aircraft below before they ask aircraft above to descend.

I think you misunderstood me.  The goal would be to get the bottom plane off
the stack as quickly as possible.  The next step would be to get the "new"
bottom of the stack to descend as quickly as possible, and so on up the stack.
This is not to imply that the airplanes would be descending simultaneously, but
rather that until the plane at the bottom descends, you can't tell the next one
up to do same.  The faster you move each member of the stack, the faster you
can get the next plane at the bottom cleared for landing, and the sooner you
can add a new plane to the stack.

>The 727 is a flying brick (apologies to F-4 fans): if you dropped the nose 
>ten degrees while holding, you could easily punch 4000 fpm (or even peg the
>IVSI at 6000), I would think.  This creates other problems, and isn't really
>desirable in a terminal environment.  

I doubt that it was truly a 10 deg difference, but I don't know enough about
the alphas for 727s, so I didn't bother to discount that assessment.

>It sounds more like porpoising: improper technique (hands-on or autopilot), a
>faulty autopilot, or some kind of a control system failure.

Good point.  I didn't think of that, but that could well be the cause.
Nonetheless, I would be surprised to find pilots porpoising much unless the
weather conditions were a bit abnormal.  Perhaps a "new" pilot (unfamiliar with
the 727, in relative terms)?

>Airline pilots are trained to "fly by the numbers."  Professional pilots will
>tend to politely decline ATC requests to "expedite" approaches, and will tend 
>to fly approaches safely, how they are trained to.

Granted.  Again, I think you misunderstood me.  Since each aircraft has an
envelope, pilots can fly anywhere in that envelope.  Some fly closer to the
edge than others, and those that do would be inclined to accept those ATC
requests.  I just gather this information from listening to ATC transmissions
during rush hour at LAX.  Anyway, my point is that he may have been on a flight
where the pilot felt safer nearer the edge of the envelope than most other
pilots.  It happens.

>It is ATC's responsibility to adapt to pilot requirements for safe flight, 
>NOT the pilot's responsibility to keep things "orderly" for ATC.

Nonetheless, sometimes reality doesn't match theory.  When things get tight
around major airports (O'Hare, for example) during rush hour, ATCs tend to make
somewhat unreasonable requests.
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-  Michael   |  School of Engineering & Applied Science  -
-   Weiss  |   University of California, Los Angeles   -
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