From: firstname.lastname@example.org (Bruce W. Watson) Date: 12 Feb 93 11:12:10 PST References: 1
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In article <airliners.1993.138@ohare.Chicago.COM> email@example.com (Mike Howells) writes: > >I've heard the DC-8 is approved to deploy its inboard reversers inflight to >slow itself down or whatever. Can anyone confirm this? > >Also, how much drag does it provide? I would bet a crapload. > >| Mike Howells | >| Commercial Pilot | >| Airplane Single and Multi-engine Land ave | >| Instrument Airplane | > > Yes, I can confirm this. I've had many conversations with (mostly KLM) ex-DC8 captains who all claim that reverse thrust is approved in flight. There are several prop and turbo-prop aircraft approved for this type of thing. As for the DC-8, it was usually used to increase rate of descent, maintaining constant airspeed. The amount of thrust permitted (as I'm told) is up to the spinup position (however that's measured on the DC-8 -- perhaps N2?), and not to be used inside the FAF. I suppose that there probably wouldn't be a problem using reverse on all 4, if you could get the turbines to spinup at the same rate. Unfortunately, not having the two outboards go to reverse simultaneously can be trouble - asymmetric thrust. This is something of a general problem; for example, in an older 747 you may have noticed (on takeoff) that you sat in position for a moment with the brakes set while all 4 engines were spun up (to 55% or 70% N1 depending on how the particular airline measures spinup) before releasing the brakes and applying (possibly derated) takeoff thrust. The same reasoning is why after applying reverse on the 747 commits to a full stop -- it's not possible to go back to forward thrust for a go-around without a major risk of severe yaw (I admit I only *know* this for the -200). Later, Bruce.