MyCargo 747-400F crashes into Kyrgyzstan village

Russian investigators have recommended that Boeing change the autopilot logic to prevent another accident like this. Under the current logic, if the aircraft captures a false glideslope, it will maintain an inertial path, until or unless the crew intervenes or a valid glideslope is intercepted, until it reaches the flare point. In this instance, the aircraft reached the flare point before the crew decided to go around.

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According to the accident report, the aircraft gave the crew several warnings that they were too high before the crash. The glideslope deviation indicator was in the full down position. As they passed the outer marker, which was supposed to be at 2800 feet, they were still level at 3400 feet. They began to descend after passing the outer marker, but the aircraft had captured a false 9 degree glideslope reflection.

At the middle marker, 0.6 nm from the runway, they were passing through 3300 feet. The required altitude was 2290 feet, which would put them 235 feet over the airfield elevation. The aircraft wound up overflying the entire runway.

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Investigators detailed the descent that caused the aircraft to catch a false glideslope. The aircraft was at 18,000 feet over waypoint RAXAT, when they were cleared to descend to 6,000 to pass TOPKA. That gave them 27nm to lose 12,000 feet. A normal descent, following the airline's procedures would have allowed them to lose 9,000 feet in that time.

Instead of deploying speedbrakes, as they should have, the crew used various autopilot modes, and allowed the speed to increase to 317 knots. They were at 9200 feet and 270 knots over TOPKA. This resulted in them being high for the rest of the descent, and capturing a false 9° glideslope that took them over the airport and into the village.

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a reply to: Zaphod58

I mean WTF. Why would you dick around instead of SOP?

a reply to: FredT

That's the million dollar question.