A lot of possible possibilities.
I'll try to collect some "objective facts" in more-or less chronological order.
1) Plane was approaching 01 normally
2) ATC transmitted warning for bird activity
3) A witness reported seen approaching 01 normally with gear extended (and certainly maybe not 30 or 40 yet but at least a good chunk of flaps extended, since the ground speed was about 154 kts which with almost zero wind and at almost sea level means that the airspeed must have been about that too, which slow enough to absolutely require at least some flaps).
4) Same witness reported seeing the plane cross a flock of birds and hearing 2 or 3 pops, possibly due to an engine ingesting birds.
5) Plane announces to ATC that they are going around
6) Same witness reports that plane started a go around and climbed first, but then was unable to continue climbing.
7) ADS-B data stops being received when the plane was still in the approach path and at 900 ft.
8 ) A video shows a plane still on the approach course to 01, with the gear up and some flaps, where the #2 engine (right side) emits a brief flame and a puff of smoke. This must have been after the go around was initiated since the gear was extended before and now it is retraced. It also means that this is a new "event" different from the one the witness reported in point 4).
9) Crew declares mayday and request to land in RWY 19 (same runway than 01 but opposite direction), and ATC approves.
10) Plane is seen in the flare of RWY19 coming fast, floating long, and touching down well past the normal touchdown zone still going too fast. Landing gear is up, flaps are totally or mostly up, no spoilers. #2 engine (same one that the previous video shows the surge) is still blowing air (i.e. producing at least some power) during the flare. No evidence to tell if #1 is working or no.
11) During the skidding the reverser for the #2 engine is seen open.
12) Plane skids past the end of the runway still at very high speed, skids along 125m of paved stopway plus 125m of grass and slams into a concrete and earth embankment that acts as the base of the ILS localizer antenna.
13) The impact destroys most of the plane and causes an immediate fireball.
14) Only the rear of the plane (from the rear doors to the tail) remains relatively intact. From there 2 flight attendants are extracted alive. These are the only survivors.
Many scenarios can fit these facts. Things that we don't know:
a- Was no engine, one engine, or both engines significantly affected due to birds ingestion or other issues?
b- Did the pilots attempt to shut down any engine, and if so was it one that was still producing useful thrust?
c- What was the ADS-B data lost on the first approach at 900ft? Did the transponder stop working? If yes, was that due to a loss of electrical power, or maybe by accident when the pilots attempted to squawk 7700? (Note: ADS-B data for other planes in the same airport before the accident was still being received after landing and during taxi). I fear that if this happened as a result of a total electrical failure (except perhaps for the battery-powered essential bus), the CVR and FDR would have stopped recording at that point too so a lot of information of what happened during the second approach and landing would be lost forever.
d- Why didn't the pilot extend the flaps for the second landing? Options are they forgot under stress, they lost all hydraulic and electrical power, they lost hydraulic system A (left side) which powers the flaps and didn't have time and mental bandwidth to deal with the slow and higher workload electric alternate extension, or they elected to leave them up perhaps to reduce drag and extend the glide or be able to fly with deteriorated thrust.
e- Why didn't the pilots extend the landing gear? The landing gear can be extended with the alternate method (purely mechanic) even after a total loss of all hydraulic and electrical power. Forgot? Didn't have time? Or intentional to reduce drag?
f- Did the pilots actuate the reverser of right engine? Or was it a mechanical failure as a consequence of sliding on the engine cowlings?
I'll try to collect some "objective facts" in more-or less chronological order.
1) Plane was approaching 01 normally
2) ATC transmitted warning for bird activity
3) A witness reported seen approaching 01 normally with gear extended (and certainly maybe not 30 or 40 yet but at least a good chunk of flaps extended, since the ground speed was about 154 kts which with almost zero wind and at almost sea level means that the airspeed must have been about that too, which slow enough to absolutely require at least some flaps).
4) Same witness reported seeing the plane cross a flock of birds and hearing 2 or 3 pops, possibly due to an engine ingesting birds.
5) Plane announces to ATC that they are going around
6) Same witness reports that plane started a go around and climbed first, but then was unable to continue climbing.
7) ADS-B data stops being received when the plane was still in the approach path and at 900 ft.
8 ) A video shows a plane still on the approach course to 01, with the gear up and some flaps, where the #2 engine (right side) emits a brief flame and a puff of smoke. This must have been after the go around was initiated since the gear was extended before and now it is retraced. It also means that this is a new "event" different from the one the witness reported in point 4).
9) Crew declares mayday and request to land in RWY 19 (same runway than 01 but opposite direction), and ATC approves.
10) Plane is seen in the flare of RWY19 coming fast, floating long, and touching down well past the normal touchdown zone still going too fast. Landing gear is up, flaps are totally or mostly up, no spoilers. #2 engine (same one that the previous video shows the surge) is still blowing air (i.e. producing at least some power) during the flare. No evidence to tell if #1 is working or no.
11) During the skidding the reverser for the #2 engine is seen open.
12) Plane skids past the end of the runway still at very high speed, skids along 125m of paved stopway plus 125m of grass and slams into a concrete and earth embankment that acts as the base of the ILS localizer antenna.
13) The impact destroys most of the plane and causes an immediate fireball.
14) Only the rear of the plane (from the rear doors to the tail) remains relatively intact. From there 2 flight attendants are extracted alive. These are the only survivors.
Many scenarios can fit these facts. Things that we don't know:
a- Was no engine, one engine, or both engines significantly affected due to birds ingestion or other issues?
b- Did the pilots attempt to shut down any engine, and if so was it one that was still producing useful thrust?
c- What was the ADS-B data lost on the first approach at 900ft? Did the transponder stop working? If yes, was that due to a loss of electrical power, or maybe by accident when the pilots attempted to squawk 7700? (Note: ADS-B data for other planes in the same airport before the accident was still being received after landing and during taxi). I fear that if this happened as a result of a total electrical failure (except perhaps for the battery-powered essential bus), the CVR and FDR would have stopped recording at that point too so a lot of information of what happened during the second approach and landing would be lost forever.
d- Why didn't the pilot extend the flaps for the second landing? Options are they forgot under stress, they lost all hydraulic and electrical power, they lost hydraulic system A (left side) which powers the flaps and didn't have time and mental bandwidth to deal with the slow and higher workload electric alternate extension, or they elected to leave them up perhaps to reduce drag and extend the glide or be able to fly with deteriorated thrust.
e- Why didn't the pilots extend the landing gear? The landing gear can be extended with the alternate method (purely mechanic) even after a total loss of all hydraulic and electrical power. Forgot? Didn't have time? Or intentional to reduce drag?
f- Did the pilots actuate the reverser of right engine? Or was it a mechanical failure as a consequence of sliding on the engine cowlings?
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