Musician
July 18, 2025, 05:18:00 GMT
permalink Post: 11924846

Thank you for your reply, appruser , and apologies fur cutting most of it:

Quote:

Originally Posted by appruser

Big questions in my mind:
1. If the loss of ADSB corresponds to the E1/E2Fuel Cutoff switches being moved from RUN -> CUTOFF, why is the airspeed declining for the prior 4 seconds?
2. In 4 seconds, why is there only 50ft of altitude gain? that seems odd.
3. To account for only 50ft of alt gain, if we assume the 1st reading is on the runway just before rotation, the intermediate +25ft alt gain is at rotation (Nose up but MLG still on the runway), and the last 4 readings are in the air (nose up an additional 25ft), that means that 1 second or less after lift-off, ADSB was lost - this is before E1/E2 FCO RUN-> CUTOFF.

It's just weird .

1. I don't know that the transponder lost power, because I don't have knowledge which electrical bus it is powered from on the 787. It may well have been powered from the main battery the whole time. The FR24 receiver may have stopped receiving data because it could no longer "see" the aircraft‐‐we know there are issues because it didn't even see the eastern half of the runway.
2. Altitudes are rounded, so this could be close to 75 feet gain‐‐or a gain and decline, if the data covers the top of the trajectory.
3. The first reading is definitely in the air, after rotation. FR24 does not report the altitude when the ADS-B data indicates that the aircraft is on the ground, and their data download confirms that.

The best bet to establish timing is to use rotation as datum, and then match the altitude/time estimates from the CCTV with position/time from the ADS-B and the estimated ground speed of the aircraft.

The fact that the ground speed is declining throughout the data sequence strongly suggests that it begins some time after the point, or at the point, when thrust was lost. And we know that didn't begin to happen until the aircraft was 3 seconds into the air.

Last edited by Musician; 18th July 2025 at 05:38 .

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