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| Re: Investigation focuses on possible pilot error in crash landing of South Korean plane (1080202) | |||
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Re: Investigation focuses on possible pilot error in crash landing of South Korean plane |
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Posted by Dave on Mon Jul 8 17:29:50 2013, in response to Re: Investigation focuses on possible pilot error in crash landing of South Korean plane, posted by cortelyounext on Mon Jul 8 16:56:38 2013. I sent my neighbor (retired AA 777 captain) an e-mail asking a question. This was his answer:On Jul 8, 2013, at 7:20 AM, Dave wrote: << Reports are that the engines were at idle prior to the crash. Is that normal in the 777? I thought in jets, power was carried until over the numbers in order to minimize spool-up time in the event of a go-around? >> His response: http://navyflightmanuals.tpub.com/P-1231/P-12310081.htm One of the big buggaboos in the airline business is a thing called a "stabilized approach". What that means, in a nutshell, is constant airspeed, constant thrust, constant vertical speed. None of these factors are changing as the A/C approaches the runway. Airspeed is set by AOA or pitch angle, and vertical speed is controlled by thrust. Most non-aviation types have this concept backwards; they think changing the pitch changes vertical speed, and while it does to some extent, pitch is AS and thrust is VS. So to properly fly a stabilized approach, the aircraft has to be fully configured for landing by a certain point, 1000' AGL or the outer marker for example, and after that it is just maintaining the same airspeed all the way to touchdown at a constant rate of descent. Reference the above link it takes lots of power to fly this way, as opposed to a gliding, decelerating approach. Southwest were the biggest cowboys when it came to charging up to the final approach point with their hair on fire, idle thrust, pitch down the glide slope and configure and decelerate as you went down the glide slope until you were on speed for touchdown and then power was added to hold that speed and an acceptable descent rate. As you can probably surmise, this is a crap shoot, as each approach conditions would be different. I'm really surprised that they didn't have more landing accidents in their early years. It's like waiting to cross the threshold to take out the crab and hope you get it right as opposed to taking the crab out ala forward slip at about ¼ mile so you have time to adjust your lineup for centered touchdown, only decelerating approaches are a factor of 10 more dangerous. Procedure in the B777 was to carry power until the flare was established, which means a pitch change of about 4 degrees to minimize the descent rate, and then the throttles were retarded to idle. In a crosswind, I didn't retard the throttles until I felt the first gear touch. So if Capt Kim had the engines at idle, then he totally pissed in the kimchi. The investigation is most likely going to conclude that this was totally pilot error on both the Capt and the check airman or whoever the other person in the cockpit was. And yes, it does increase spoolup time for G/A if the thrust is somewhere above idle when you "cobb 'em" |
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