Broke From United States of America, joined Apr 2002, 1322 posts, RR: 3 Reply 3, posted (10 years 11 months 2 weeks 6 days 12 hours ago) and read 1808 times:
All of the early 747's, DC-10's, and L-1011's had the capability to reverse both the fan air (cold stream) and the gas generator (hot stream) air. In all applications the system was terribly unreliable for the hot stream portion of the reverser. I worked at EAL and inoperative thrust reversers on the L-1011 in the early 1970's were a common occurrence, often after shedding parts of the hot stream deflectors on the runway.
For EAL operations into LGA, all 3 reversers have to be operative. This was an EAL requirement and not regulatory. Since most of our LGA-Florida operations were L-1011's, we have a lot of reverser related delay and cancellations at LGA.
A big problem with the design of the L-1011 reverser system was that the sensors indicating the status and operation of the system were all tied to the hot stream portion of the system; so converting to a cold stream only system required some major redesign and modification work in order to accomplish it.
In addition, if you look closely at the tail cone angle on the L-1011's through the early years of operation (1972 on), you will notice that the angle changes. The early tail cones were the 22 degree configuration, later they went to the 15 degree design. The reason was drag reduction, but not much of an improvement was ever actually seen.