Ferg,
The finer points of altitude hold in a simplistic a/c need little explaining
because if any pilot places full reliance on any aid, it is Murphy's Law that
"s..t happens". We can find concerns in every aspect of aviating, but if you
want to fly along and fill out a deck log with an altitude hold, go for it.
Lets face it, whilst your bum is pointing down and it feels so, and your eyes
are engaged in peripheral mode, your ears are listening to the air noise of
your plane and you remember that the altitude hold is only an aid and shouldn't
be religiously trusted, well turn it on, relax, fill out your log or look out
the window and enjoy the view. I for one would be bitterly disappointed if my
Europa once it finally flies is not speed stable enough when flying at cruise
indicated airspeeds greater than 50 kts above stall speeds, to not be able to
lose a few knots and not recover them, rather than sliding down the backside of
the drag curve into a stall. Don't forget, this is supposed to be fun. I reckon
if I am going to have any form of autopilot the altitude hold would equally as
desirable as any track following.
Rg
Tony Renshaw
>Cheers,
> I see some discussion of Altitude Hold phase of Flight control
>management. While I am in no position to question builders/fliers on their
>experience, I feel it imcumbent to mention it if those unaccustomed to
>auto-control are contemplating its installation.
> The one phase of 'altitude hold' deserves careful consideration.
>In modern transport aircraft, this phase by itself is inherently unsafe,
>unless Airspeed Control is also imposed. While it's obvious that we don't
>want to hold altititude 'til the airspeed loss induces a cruise wing stall -
>it's happened - it IS possible that in this phase other distractions can
>make it happen.
> Even in modern transports (the L-1011 was most advanced at the
>time), the failure to monitor airspeed and guard against stall can be
>induced without warning. In the case of the TriStar, very often the aircraft
>was forced to climb higher for overriding reasons than ideal, which put it
>within so many knots of stall, and of Mach limits. Unforecast turbulence
>knocked the auto-pilot down a notch to permit it to smooth outcorrections in
>airspeed and height to play each against the other for a smoother flight.
>However, it knocked the auto-throttles off as well - so we were particularly
>sensitive to stall and Mach. An onboard diversion occurred which (only for
>seconds) took attention of one away from the 'watch' and the aircraft slowed
>to below minimum airspeed. Immediately, the descent in pre-satll was
>arrested, but the recovery was reallly delicate, and height was sacrificed
>for speed during power application. This cautionary manoeuvre was not best
>described in the manual. It was changed .........
> While over 35000 approaching Iceland westbound, and facing
>200knot winds (mechanical trubulence at that height and oscillating up- and
>down-drafts exceeded 2000 fpm) are rare events, it proves that not all
>conditions are covered - and altitude-hold can be a fool's paradise under
>rare circumstances.
> Thought I should share the idea.............
>Cheers, Ferg
>PS ....guess what I mean is - if the alt hold is 'on', make sure the hand is
>on the trhottle, the eye on the speed..........
>
>
Reg
Tony Renshaw
Builder No.236
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