Re: A 777 with four engines.

Date:         10 Sep 98 03:04:33 
From:         Krish Chilukuri <krish@san.rr.com>
Organization: TWC Road Runner, San Diego, CA
References:   1 2 3 4 5 6 7 8 9 10 11
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I came in late to this particular thread and hence do not know if this
has already been discussed. Here are my impressions on this issue -
critique is most welcome.

As a result of the Lauda crash, a team of industry and FAA specialists
got together to discuss options prior to recommending new rules.

a) The latest certification requirement is that the probability of
in-flight reverser deployment should be extremely remote - three
independent lines of defense against deployment are required. Integrity
of reverser locks should be shown even in the event of a turbine rotor
disk failure.

b) Or else, the FAA will require in-flight demonstration that the
aircraft remains controllable after a single reverser deploys at take
off power. (earlier demonstrations were required only at flight idle
power).

Most new aicraft go the reliability route. I suspect that you will not
be able to find a test pilot who is willing to demonstrate aircraft
controllability with asymmetric reverser deployment under full engine
power!!

BTW, NASA conducted some flight tests on a DC8-72 aircraft, and deployed
both inboard reversers in flight. At high enough airspeeds, the reverser
plumes tucked under the wing. At low airspeeds, the plume went over the
wing, causing massive separation and loss of lift. The aircraft lost
altitude at the rate of almost 12000 ft/min when reversers were deployed
at cruise and about 30000 ft.

I also believe that the C-17 test flights routinely deploy reversers
during flight test, with much larger rate of  loss of altitude.

Krish Chilukuri