RE: T-Tailed aircraft

From:         "William R. Hoscheit" <billh1@gramercy.ios.com>
Organization: Pacific Presentation Graphics
Date:         19 Apr 96 02:04:03 
References:   1
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John,

There are many factors that influence a specific aircraft's configuration.
 Specificially, t-tail aircraft have certain characteristics that are
beneficial to design.  For example, it can provide improved performance,
due to cleaner wing configuration on short or hot and high field
operations.

However, one of the penalties associated with t-tailed aircraft are
diminished low-altitude/low speed handling.  It can also affect weight and
balance, providing such a tight center of gravity that the IL-62 includes
a hydraulic "kick-stand" to support the plane's rear weight while loading
and unloading.

As powerplants have improved, there has been less of a need to implement a
t-tail approach to performance.  Also, due to the size of some of the
engines, the sheer design considerations of placement and support in the
tail section become a greater challenge.

One other factor that effects current design is the much-improved wing
structures.  With the arrival of light-weight composites, and a better
understanding of sweep, aspect-ratio, and super-critical features,
designers are able to extract performance on winged designs that
previously couldn't be acheived.

Also, engine maintenance is much easier on winged designs.  Accessing the
fans can be done from the ground, vs. elaborate scaffolding structures
that virtually all t-tail planes require.

Finally, economics have driven manufacturers to address the widest
possible customer appeals.  The CV-990, Trident, VC-10, and other examples
of market or carrier-specific designs have proven unprofitable.  There is
no longer the drive for the prestige of a "jet" aircraft, as they are now
the standard.  Many carriers weigh these maintenance and support costs
into their purchasing decisions, and fleet commonality has become and
increasing influence.  As the trend is toward wing-mounted design,
carriers have been able to reduce or eliminate some of the support
overhead associated with t-tails.

I hope this provides some useful insight into your question.

Regards,

Bill Hoscheit