Deadly plunge (cont’d)

The accident mentioned in latest article, the Sriwijaya Air plane that crashed last month killing 62 people, has been explained in a preliminary report. To any regular airline pilot the explanation should be confusing. The auto-throttle systen has allegedly reduced power on the left engine while keeping normal thrust on the right. After climbing another some 3000 ft (from 8.150 to 10.900) with the autopilot engaged, it disengaged. It had obviously co-operated long enough, trimming away the unbalance until it could take no more. When disengaging, it caused – not surprisingly – a bank to the left; ”the plane rolled to the left more than 45 degrees and started its dive.”

Unless there is more to report, the available info is nothing but sensational. Asymmetric thrust (read engine failure) is by far the most common practice in simulators around the world in normal pilot training. There simply has to be more to this story, which makes it prudent to refrain from any judgement on the airline and its pilots at this stage.

Not really related, but in a way similar, and where the pilots did nothing wrong except falling asleep, an incident from long ago is worth mentioning. A 747 was plowing along in the night over the USA at 35.000 ft, when one engine stopped for an unknown reason, possibly fuel starvation since everybody was asleep. The autopilot did what it could to keep things straight and level for as long as it could. All available trim adjustments made and with the speed dropping, it finally gave up fighting, flipping the aircraft on its back and sending it into a vertical dive. With a 5G pull-up the crew (they were now awake) managed to stop the descent as 7.000 ft, loosing some airfoil surfaces, especially in the tail section, with all main gears torn from their up-latches crashing out through the landing gear doors, but remaining attached to the aircraft, and limped, badly bruised, into LAX, realizing again that the 747 was the sturdiest aircraft ever built.

Some more Boeing-lover news; Boeing delivered 26 aircraft in January, boosted by the clearing of the 737 MAX jet to fly again after a 20-month ban as it also won four new orders for its 747-8 freighters. The 747 is obviously still hanging in there.

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