From: rdd@cactus.org (Robert Dorsett)
Subject: Re: SubLOGIC's F.A.: ATP for Christmas
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date: Wed, 30 Dec 1992 04:29:41 GMT

In article <29DEC92.17324945.0027@UNBVM1.CSD.UNB.CA> U6IC <U6IC@UNB.CA> writes:
>	One comment though, a friend of mine who rode 'up
> front' in one of these jets some time ago, indicated that
> even altitude changes (can be/were being) controlled by the
> A/P through the use of a dial. I thought the use of an
> altitude 'bug' would be nice.
>
>Is this realistic though? The idea of one for heading is very
> convenient.

Most autopilot mode control panels permit one to dial in a selected altitude 
through a digital display.  How the airplane gets there depends on a variety 
of factors.  On older 727's, for instance, one essentially only had the option 
of adjusting airplane pitch.  So one would select an altitude, configure and 
trim the airplane to climb, and engage "pitch hold" and "altitude select."
When the airplane gets to within 1000' of the selected altitude, depending on 
rate of climb or descent, it starts to automatically level off.

Most later modes are variants on a theme.  For instance, vertical speed
mode really just dynamically adjusts the airplane's pitch for the pilot.
On the 747-200, one would use a thumb-wheel to command a greater or lesser
sink rate.  The distinguishing feature of this type of system is that if one
is climbing, and NOT in a V/S mode, the wheel still moves--this is so
that when you do select V/S, you'll have a smooth entry, and not have
to risk something like suddenly dipping into a 3000 fpm dive, from a 3000
fpm climb, for example.  

Other "pitch" modes are IAS and Mach hold, which also adjust pitch to
maintain an airspeed at a given thrust setting.

Most modern airliners climb in an EPR hold mode, with V/S changing 
throughout the climb, as the air gets thinner.  

When you add an autothrottle, procedures change somewhat. 

I don't see a place for an "altitude" bug on an altimeter, though.  What
intrigues me is the use of a V/S bug on the vertical-speed indicator.  I'm 
using something similar in my 727 simulator.  I was intrigued by the
apparent similarity of my system to a bug used on the Lear 55.


>    iii)  The planes can actually be flown!!!!
>
>          I never professed to be really adept at any of FS4's
> planes other than the Cessna. I felt badly about this until I
> read a review from the 'Gamers` forum which stated that the
> Learjet was virtually impossible to maintain at a particular
> altitude and attitude for any period of time. 

It takes practice, but it can be done.  It is clearly a case of learning
the manufacturer's interface, though, rather than any inherent problems
arising from flying a simulated Learjet.  I've actually found the FS4 
Learjet (both mac and pc versions) to be so unstable that it's helped me
more accurately control other types of PC simulators.  If you can control
FS 4's Learjet to the point of landing on the aircraft carrier (and taking
off again), you'll never have a problem with any other type of simulator.
:-)


> the ATP a/c's. Now whether I am always doing what I'm
> supposed to be doing (correct airspeed,altitude +/-200,
> proper cruise/climb/descent configuration etc.) is another
> matter.

Airline pilot checkride tolerances are +-20', no heading deviation.  Practice,
practice, practice...:-)


> FS4. With FS4, I tried to get as realistic in my flying as
> was possible, but not being a pilot, there are limitations to
> how much you can do and no book I ever came across really
> gave details on what is actually done inflight re: margins on
> error for altitude, speed etc. I also never really had an
> idea of typical cruise altitudes, rates of climbs and
> descents.

You might find _Fly the Wing_, by Jim Webb, of interest (Iowa State 
University Press).  Webb is an old Eastern Airlines instructor: he ignores
systems, and concentrates on "flight procedures."  I believe it's in print.


How good is the HSI?  Someone (John Mechalas?) mentioned that the new
version had an HSI with a movable compass card...





---
Robert Dorsett
rdd@cactus.org
...cs.utexas.edu!cactus.org!rdd
Newsgroups: rec.aviation.simulators