Newsgroups: sci.aeronautics.airliners Path: news From: rdd@cactus.org (Robert Dorsett) Subject: Yet more on the El Al crash X-Submission-Date: Mon, 14 Dec 92 00:56:54 CST Message-ID: Approved: kls@ohare.Chicago.COM Sender: kls@ohare.Chicago.COM X-Submission-Message-Id: <9212140656.AA22726@cactus.org> Date: 14 Dec 92 14:11:42 PST Today, I ran across a copy of a real, live, 747-200 Airplane Flight Manual. The AFM is the manufacturer's legal statement of airplane capabilities; it is custom-outfitted for each customer configuration, must be kept up to date, and is kept in the actual airplane: it's the bottom line for normal operations, , "outranking" even normal pilot Operations Manuals, which present processed data, based on the AFM, in a more user-friendly format. It contained some information which might be of interest to the net, particularly given the impression some people seemed to have of the ramifications of a two-engine failure. I'm also referring to the AvLeak of October 12 for particulars on the flight. The manual describes a 747-200, with CF6-50E engines, which produce a static thrust of ~52,000 lbs. The El Al airplane was powered with JT9D-7J's, which produce ~50,000 lbs of thrust). So it's not entirely applicable to the El Al crash, and I emphasize that the following is simply a "what-if," using the crash profile. We'll use a basic operating weight empty of 170,000 kgs, and the actual cargo load of 114,000 kg and the fuel load of 70,000 kgs. That gives us a gross weight of 354,000 kgs. The crash airplane achieved a maximum altitude of 5000' at 285 knots. It later achieved a maximum airspeed of 313 knots at 4900'. About six minutes after the initial failure, the captain reported problems with flaps. By the time the plane had descended to 2900', 25 seconds later, the crew issued a mayday call, indicating they were losing control; impact was 45 seconds after that. The slowest airspeed the airplane attained was 260 knots or so. The AFM gives some information that wasn't available during the original discussion. Such as: - 2-engine operation is *certainly* an in-envelope contingency. - It is possible to maintain altitude at up to 360,000 kgs. Some numbers. Draw your own conclusions: again, we're talking a different airplane, with different thrust capabilities. 1. Placarded flap speed limits. We can assume that if the crash airplane was following these limits, it was at flaps-up by the time the failure occurred. 1 275 knots 5 250 knots 10 238 knots 20 231 knots 25 205 knots 2. Gear-up stall speeds at 355,000 kgs: Flaps Speed 1 203 knots 5 153 knots 10 150 knots 20 144 knots 25 124 knots (landing flaps: assumes weight is down to 295,000 kgs). 3. At 355,000 kgs, *with two engines out*, our -200 would have been able to maintain level flight. It should also have been able to establish a climb gradient of 0.4% (175 ft./min) at 280 knots, the prescribed en route climb speed for this condition. --- Robert Dorsett rdd@cactus.org ...cs.utexas.edu!cactus.org!rdd