Posted on 07/08/2013 7:37:00 PM PDT by justlurking
I used the data for Asiana Flight 214 from FlightAware to create a series of graphs to help Freepers understand how the approach to landing deviated from the expected behavior.
This data is collected from the FAA computer systems. The location data is either calculated by the FAA radar or reported by the aircraft transponder. The altitude is reported by the aircraft transponder. The ground speed and vertical descent rate is most likely reported by the aircraft's Mode S transponder, but it's possible these were computed by the radar system.
This first graph is a plot of the latitude/longitude in the last 15 minutes of flight. Each blue dot is a reported position, the blue line connects them. The red line is runway 28L. North is at the top of the graph. The aircraft approaches from the northwest, crosses over the runway and makes a descending left turn to final:
Pilots will recognize this as a modified crosswind VFR approach to land. For non-pilots: the classic crosswind entry to the landing pattern is:
The aircraft was descending through this entire maneuver. The track didn't follow the crosswind pattern exactly, but the pilot would have been following ATC instructions. My point is this is a pretty standard maneuver, and you shouldn't think it is unusual or difficult.
The next three graphs are are stacked together, so that you can see how the different metrics change together. All start 14 nautical miles from the runway threshold when the aircraft is established on the final approach, and end about 1,000 feet from the threshold. This is the last data point that I believe to be valid, as the final data point in the FlightAware data appears to be post-impact.
Note that the altitude is reported in increments of 100 feet. So, there will be a bit of error introduced in the individual points, but the overall trend will be accurate.
The first graph is altitude. The blue line is the aircraft, and the red line is the 2.85 degree glide slope that would be projected by the PAPI lights on 28L, if they were in operation. There are conflicting reports whether the PAPI was in operation, but either way it is still a way to project where the aircraft should have been on the glideslope.
The second graph is ground speed, in MPH. Note this isn't the same as airspeed: if there was a 5 MPH headwind, add another 5 MPH to the ground speed to yield the airspeed. The red line depicts the 157 MPH landing speed typically used by the 777. Stall speed depends on the flap configuration and gross weight: I'll defer to someone more knowledgeable to provide that information.
The third graph is vertical descent rate, in feet per minute. A constant descent rate for this approach would have been about 700 FPM.
From these graphs, you can see several things:
I'll repeat that this track log ends about 1000 feet from the runway threshold. Passengers and observers have reported the aircraft was too low, but that was apparently at the very end of the final approach.
If this data is accurate, the aircraft was too low and too slow because it was too high earlier in the approach and the pilot over-corrected.
Die Hard
Change the reading to the altimeter and the pilot won’t be able to recover at the last minute
CC
Sounds like he screwed the whole approach up, starting 12 miles away.
Ping for your info, review, and commentary.
Should have “gone around” at 3nm ?
Over-compensated for the altitude and airspeed, and followed later with an “oh sh!t” moment, probably. That second increase in descent rate happens at the same time as a sharp drop in airspeed. Is that possible? And then finally it looks like a serious pulling up on the stick.
It was still recoverable at that point. But, the closer they got to the runway, recovery became more and more difficult.
In a smaller aircraft, it's easier to correct. But, a 777 has a lot of inertia, so you must anticipate, rather than react.
Compare a jet ski vs. an oil tanker. The difference between a Boeing 777 and a Cessna 150 isn't as large, but the principle is the same.
Excellent presentation of the pertinent data to show a story as old as the Wright Brothers: running out of airspeed and altitude combine to become non-optimal career disintegration factors.
I would be interested in how far he was behind a heavy and what his flight profile was in relation to the aircraft he was following.
If he was slow and if he allowed the aircraft to get below the flight path of the heavy ahead, wake turbulence could have been a factor.
I am surprised that a cockpit full of highly experienced pros got caught in this trap. Too high too close is one of the oldest traps.
Instrument pilots know very well that if the aircraft is not in proper configuration four miles from touchdown: Power settings, aircraft config, speed and rate of descent stabilized, the landing will not be a good one.
Much has been made of the fact that the ILS was out, as was the VASI.
I quit flying quite a few years ago, so I no longer subscribe to Jepps, but I suspect that LAX has a GPS approach. Even if it does not, a prudent pilot with GPS or an inertial nav system would set up the touchdown point in the GPS and have from that a “glideslope” that would allow him to set up an approach that was proper.
That would have made landing at an unfamiliar airport much easier.
In other words, xx miles out at xxxx altitude would require a rate of descent of xxx.
Depending on aircraft type and how “slick” it is, one would pick a point 3 to 5 miles outside of the point at which he wished to start the final descent and at that outside point slow the aircraft, set approach flaps and power and have all check lists completed.
In a recip engine aircraft, which is all I ever flew, one would only have to pop the gear and slide down the proper path.
He was already at stall with nose high trying to maintain altitude.
W the throttles, instead of giving it forward yoke the engines kicked the nose up further and he stalled out!
Actually he should have executed a missed at least 4 miles out when he couldn't even come close to captuering the glide slope.
I used to fly a single into LAX twice a week and they always had me keep my approach speed to 150k minimum until crossing the numbers.
Remember that is ground speed, not air speed. Now, consider what happens if the aircraft is maintaining roughly constant velocity, but that velocity vector suddenly points down at a steeper angle, rather than forward and down. As if someone were diving for the glide slope... Vertical decent rate goes up while horizontal ground speed decreases. The aircraft was traveling more down than forward. Or at least the proportions of forward and down changed significantly. Dirtied up though the aircraft wouldn't have gained much actual airspeed to trade back for altitude later. Just scrubbing off energy...
Yes, if they reduced power and raised the nose.
Fortunately, the new digital flight controllers record all that information, and the NTSB will be able to recreate every action (and the change in aircraft attitude/speed) during the approach.
And it will be a lot more accurate than this data.
So you think that second dip in vertical speed was the actual stall?
There is no question the glideslope was out of service. The localizer was operating.
However, there is some dispute whether the PAPI was operational. The posted NOTAM is a few hours after the crash.
I went through a thread about flight 214 on a professional pilot's forum, and one pilot reported the PAPI was working the night before the crash, and another reported it was working only a few hours before the crash. But, it had been out of service earlier, which I think is confusing the issue.
what was the data entered re: elevation of SFO. I remember back in 2004/5 a 767 plowed into the ground b/c the elevation of destination was entered 40’ or so above actual. Fly by wire is good as long as data entered is accurate
As bad as it was, at least this pilot MADE it to the runway! I recall a commercial jet in the late 60s or early 70s that ended up landing in SFO bay about 1/4 mile short of the same runway that the Asiana Airways jet smacked.
The earlier jet spent a week or two in the water before a barge was brought in to lift it out and take it the last 1/4 mile to the asphalt!
Way past bedtime for a look-see...will ping tomorrow, PM. Thanks much.
Friends and I have been chatting this last couple of days. With all the pilots on the deck nobody said “too low” until the last minute when nothing could be done? Even going max power the plane doesn’t accelerate like the old prop jobs did. There’s sink rate involved and inertia to overcome before anything happens. A couple seconds to recover???? Good Grief!!! What did they say? “Gee that’s pretty water down there and oh my, look how close we are to it - hey lookit! A shark/whale/tsunami debris”
He was already in trouble and trying to save it from a stall is my guess.
At that point, he’s lost it and should execute a mised and try another approach.
He doesn’t have to ask for a missed, it’s his decision and all he has to do is announce it and execute it.
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