Re: Rear Engined Aircraft

From: (Terrell D. Drinkard)
Organization: Boeing Commercial Airplane Group
Date:         03 Jan 95 01:40:40 
References:   1 2 3 4
Followups:    1
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In article <>,
Richard Shevell <> wrote:
>thrust line with respect to the flight direction does in fact provide lift
>equal to the thrust times the sine of the thrust incidence angle referred
>to the flight direction. This discussion  depends on the definition of
>thrustline incidence.  The thrustline incidence is generally defined with
>respect to the fuselage reference line which is an arbitrary line in the
>fuselage defined, in a transport, to be parallel to the floor.  Normally
>one selects the wing incidence such that the fuselage floor is level in the
>usual cruise configuration.  Therefore the thrust does provide a lift if
>there is a positive incidence angle.  Flight attendants do not appreciate
>puishing 100 lb. carts uphill so a substantial airplane incidence in
>cruise, defined by the fuselage reference line, is a negative, although it
>has happened sometimes.  In any case if the thrust has a positive incidence
>with respect to the reference line, a positive contribution to lift occurs
>compared to a zero incidence thrust line.
Well, I don't want to argue abstruse technical definitions with you (mostly
because they differ from company to company).  However, studies have shown
that 3 degrees is about all that the cabin crew will tolerate, and that is
what we design to, along with the aero group's demand for additional cheap
lift.  The floor is NOT level in cruise.  Check it out next time you fly,
but you may need to bring something like a carpenter's level with you.


"Anyone who thinks they can hold the company responsible for what I say has
more lawyers than sense."