Re: Rate of climb and descent

Date:         19 Feb 98 01:34:41 
From:         Don Stauffer <stauffer@htc.honeywell.com>
Organization: honeywell
References:   1 2
View raw article
  or MIME structure

k_ish wrote:
> Stephan Stephany LAC-CC wrote:
> > I wonder what would be typical rates of climb and descent for airliners.
> > I suppose standard procedures provide for low figures in order to try to
> > make the ride as smooth as possible for the passengers.
>
> The standard glide slope angle to the runway is 3 degrees.  Of course,
> it may be steeper due to terrain, etc.  With initial approach speeds of
> 250 knots, some simple trig and unit conversion will give you the rate
> of descent.
>
> The desirable initial descent from cruise is as steep and rapid as
> possible (within passenger comfort, ATC, and pressurization controller
> limitations).  The idea is to keep the aircraft at higher, fuel
> efficient altitudes as long as possible.  Also, it is an instinct of all
> pilots to avoid "low energy" approaches (long and flat).  This goes back
> to basic flight training, where you should always be in an approach
> configuration where you can glide to the runway if the engine quits (not
> as big an issue in airliners).

Decent rate is limited by safety concerns.  The 727 had lots of drag
devices, and CAN provide a very high rate of descent.  There were a
series of crashes following its introduction.  The problem is, if you
are going down this fast, it takes considerable altitude to stop that
rate of descent.  The pilots did not start the transition to the glide
slope/final descent soon enough, and crashed.  So rapid descent is
limited to higher altitudes.

I do not know if other planes were certified to do this, but have ridden
on DC-8s a few times when the pilot got cleared to a lower altitude
unexpectly soon, and used reverse thrust while at high altitude.  The
pilots always warned passengers, 'cause it created quite a buffet!

--
Don Stauffer in Minneapolis
home web site- http://home1.gte.net/stauffer/
home email- stauffer@gte.net
work email- stauffer@htc.honeywell.com