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Path: utzoo!linus!philabs!cmcl2!seismo!ut-sally!oakhill!oscar
From: oscar@oakhill.UUCP (Oscar Strohacker)
Newsgroups: net.aviation
Subject: Re: Trick Question
Message-ID: <537@oakhill.UUCP>
Date: Tue, 17-Sep-85 11:14:53 EDT
Article-I.D.: oakhill.537
Posted: Tue Sep 17 11:14:53 1985
Date-Received: Fri, 20-Sep-85 02:30:30 EDT
References: <30512@lanl.ARPA>
Reply-To: oscar@oakhill.UUCP (Oscar Strohacker)
Distribution: net
Organization: Motorola Inc. Austin, Tx
Lines: 56

In article <30512@lanl.ARPA> ths@lanl.ARPA writes:
>I have received a number of correct answers to the question "During a
>constant airspeed climb what is the relationship between the four primary
>forces of flight - lift, drag, thrust and weight".  They are equal.  The
>"trick" is why does the airplane climb?
>
>Ted Spitzmiller

False, Ted.  Before you set yourself up as an aerodynamics teacher
you ought to at least understand the definitions and the physics.
These are vectors.

              L
	       L
		L           T
		 L     T
		 >> 
             D    W
        D         W
                  W
                  W
                  W
		   
   Weight - the force exerted by gravity on the a/c. (In the vertical direction,
   obviously.  This is the only one which is constant in magnitude).

The OTHER three vectors are defined with respect to the flightpath of
the aircraft.

   Thrust - the force produced by the powerplant in the forward direction
   along the flightpath.

   Drag - the component of the total aerodynamic forces on the aircraft in the
   reverse direction along the flightpath.

   Lift - the component of the total aerodynamic forces on the aircraft 
   perpendicular to the flightpath.

In any condition of unaccelerated flight the vector sum of forces on the
aircraft is zero.  This includes a constant rate climb.  However,
in a constant rate climb, because of the fact that we have an angle
between the flight path and the horizontal, we have a vertical
component of thrust, a horizontal component of lift, and a vertical
component of drag.  Generally speaking, no two are equal in magnitude
in a constant rate climb.

Perhaps the area of confusion implicit in the question and answer
is a little sloppy thinking about mechanics: it doesn't take any 
more force to raise an object vertically than to hold it level (except
the initial vertical acceleration).  But to exert the same force
through a distance requires that work be done.

___________


Oscar Strohacker    Commercial,Instrument,ASMEL


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