Re: What happened to the BAe146?

From:         J.M.Butt@aeromech.salford.ac.uk (The Time Technician)
Organization: University of Salford
Date:         25 May 96 14:40:20 
References:   1
Followups:    1 2
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In article <airliners.1996.770@ohare.Chicago.COM>,
   "R.S. Solene" <rsolene@sisna.com> wrote:
>Acavitt@mindspring.com (A.C.) writes:
>> The aircraft is a really nice aircraft.  Quiet, roomy, good all around
>> aircraft.  However the maintenance is the biggest problems that it
>> has.  Many parts are hard to get, expensive, and with 4 engines you
>> have 4X as many problems.  Sense there are few around and flying,
>> parts are not in great demand.  Sometimes it takes some time to get
>> those parts.  Unlike a 737.
>
>Why didn't the airplane's designer's realize that this aircraft would
>present 4X as many maintenance problems?  Why didn't the airlines?  Why
>wasn't the aircraft designed for just two higher thrust power plants?
>I remember asking myself these questions when I watched these planes
>enter service with PSA in large numbers and I couldn't help but wonder
>what its advantage was.
s
It's not that simple. You can't just put two engines on instead of four.
Using only two power plants instead of four would mean more powerful engines
 and hence, larger ones. This would lead to increased stressing and a larger
 amplitude of natural vibration of the wing(cantilever)[not to mention the
fact that they might not actually fit on]. Also there is the twisting effect
of the wing to be considered. Ever seen what happens when a wing twists too
far.....? This would all lead to extra support and strengthening of the
wing, thus increasing weight, taking up space, and possibly making the
design unfeasible. Also, higher powered engines would be noisy, the
Textron-Lycomings used are the quietest available - they have to be to meet
noise requirements. To be this quiet, they have to be (currently) rated at
32kN I think it is. The thrust requirements of the aircraft(skipping all the
detail) mean that there have to be four engines. Larger engines have larger
sfc's thus using more fuel, decreasing the range. Vibration could also be a
problem, not just for the airframe, but for the passengers' comfort. It must
be noted that a proportion of the noise in an aircraft does not come from
the engines, but from vibrations through the airframe, which is why Concord
is so noisy, you might be travelling twice as fast as sound in cruise, but
noise carries through metal a lot faster than through air.

As for maintenance, always a compromise has to be reached between
maintenance and feasible design. You can't have everything, at least not in
this business.

The Time Technician

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