Re: T-tail

Date:         16 Sep 97 02:37:12 
From:         "john r." <>
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In article <airliners.1997.2127@ohare.Chicago.COM>, Karl Swartz
<kls@ohare.Chicago.COM> writes
>>I understood one of the main disadvantages of a T tail aft engine mount
>>config is weight.
>While a T-tail and aft-mounted engines often go together, neither
>implies the other.  There are airliners with a T-tail which do not
>have aft-mounted engines (e.g., ATR-72) and airliners which have
>aft-mounted engines which do not have a T-tail (e.g., Caravelle,
>with the horizontal stabilizers mounted midway up the tail).

Short haul airliners have a different economics to longhaul. The
structure has tough to cope with many landings and weight is not quite
so critical as on long range airliners.
The fact that medium and long range airliners are all have wing mounted
engines and are getting very to tell apart must mean somthing. Even the
Russians are similar !

>The fuel pipes don't have to be that large, and many aircraft with
>wing-mounted engines have them anyway due to fuel storage in the
>horizontal and/or vertical tail -- optional on the 747-400, and
>available (optional or possibly standard) on the A310 and I think
>the A330 and A340, to name just a few.

Fuel pipes in pressurised zones have to be shrouded and are regularly
checked for leaks at the drain.
If its an apu system you can fly with a leak if you inop apu and can
lock the valves closed.
Four larger feeds to the engines can tolerate only very small leaks
befor they stop the plane. I used to work VC10s

>Air ducts for what?

Bleed air very hot and dangerous if it leaks, even more so if its in the
pressure hull. Many designs keep it out of the hull except for the APU,
which again, you can live without.

john r.