Re: Flight Levels and Speed

From:         Aspen20@worldnet.att.net (RWS)
Date:         12 Jul 1999 15:59:35 -0400
Organization: AT&T WorldNet Services
References:   1
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There are o so many speed when taking flying.  
Common question: How fast does your jet go?
Common easy answer to general public:  None, - make up a number and sound
sure of your self.

Definitions:

Mach number - the ration of TRUE AIRSPEED to the speed of sound

True Airspeed - airspeed of an aircraft relative to undisturbed air.   True
airspeed is equal to equivalent airspeed multiplied by (po/p)

Indicated airspeed - means the speed of a aircraft as shown on its pitot
static airspeed indicator calibrated to reflect standard atmosphere
adiabatic compressible flow at sea level uncorrected for airspeed system
errors.

Calibrated airspeed - means the indicated airspeed of an aircraft,
corrected for position and instrument error.  Calibrated airspeed is equal
to true airspeed in standard atmosphere at sea level.  
 
Groundspeed - if there is zero wind Groundspeed equals True airspeed.

As you go up in altitude on MS flight sim, your indicating less because
there's less air molecules ramming into the pitot tube (part of airspeed
indication system).  These molecules are spread thin at high altitudes
(thin air).  For packman to eat 100 molecule per minute he needs to move
much faster when the molecules are spread out so thin.  So to maintain the
same true airspeed you will see a much lower indicated airspeed at high
altitudes.  

at 10,000ft  325 Knots indicated = about 350 Knots True Airspeed
at 20,000ft  325 Knots indicated = about 460 Knots True Airspeed
at 35,000ft  270 Knots indicated = about 485 Knots True Airspeed or about
M.82 - M.83

With regards to fuel, low altitude and climb power can produce four times
the fuel flow as high altitude cruise.  The old learjets burn the same rate
of fuel on the ramp at ideal as cruising at 45,000 feet.  There fuel flows
in the low altitude climb displayed that they would be dry in 30 minutes. 
After climbing to 45,000 in under 10 minutes they had a few hours of fuel. 


hope this helps, 

Falcon 50 driver


> Wouldn't it make sense for the airliners to fly at the lower altitude,
save
> the time, and turn around the aircraft faster?  This would allow the
> airlines to use less aircraft, less crews, and make more money with more
> paying passengers per aircraft per day.  (Provided, of course, fuel
> consumption stays constant at cruise.)
>