Dorsett gets to correct himself again! (Re: 727 deep stall)

From:         rdd@cactus.org (Robert Dorsett)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date:         29 Mar 93 12:15:34 PST
References:   1 2 3
Next article
View raw article
  or MIME structure

In article <airliners.1993.277@ohare.Chicago.COM> I wrote:
>They did. :-)  The 727 followed the 111, and the designers were certainly
>aware of the problems the 111 had.

No!  The 727 (Feb, 1, 1964) was released before the 111 (April 6, 1965) or 
the Trident (March 11, 1964), although the Trident's design period predated 
the 727's by several years, which led to some bad feelings on British 
Aerospace's side.

As for the stabilizer (from _Case Study in Aircraft Design: The Boeing 727_,
AIAA Professional Study Series, Sept. 14, 1978, in the article "Requirements
and Major Decision Outline: Total Program," by J. E. Steiner, pp. 3-4):

"All previous Boeing jet airplanes had had low horizontal tails (except the 
B-47 mid-tail) and we were acutely aware of some of the problems that "T" 
tails can get one into. [...]

"[... a] 'conventional' [tail] was aerodynamically attracitve, and [...] 'low
horizontal' gave us serious problems with the installation of the third 
engine.  We finally decided on the "T" tail despite its difficulties.

"Among other things, we made very extensive flutter investigations with both
low and high speed flutter models.  This was our first experience with high 
speed flutter models [...].  Prevention of flutter is the reason for the 
727's horizontal tail anhedral.

"I noted earlier that we were familiar with "T" tail troubles and we were,
more or less.  However, the BAC-111 locked-in-stall accidents had not yet 
happened and neither we, no so far as we knew, had anyone else really tested 
at angles of attack approaching 40 degrees (we later did--both in the wind
tunnel and in flight).  However, we did have one previous experience with a 
configuration which tended to go to extreme angles of attack and coincident-
ally very high rates of descent, and I like to believe that this guided our 
elevator size and power selection.  The 727 never was capable of getting into 
the BAC-111 situation."





---
Robert Dorsett
rdd@cactus.org
...cs.utexas.edu!cactus.org!rdd