Polish Presidential Flight Crash Thread

[SadPole]

One more thing to remember is that whatever the hell the crew was trying to do, they did the whole thing on Tu-154 autopilot. Yes, some spoken info might have been distorted on the CVR, but there is very little chance that the autopilot sound signals were not recorded and recognized clearly.

So yes, while some can fantasize that the CVR has been tampered with, I will assume that it was not, at which point we arrive at following facts:

• The autopilot was NOT disengaged till 10:40:59 or 5 seconds before the plane came in contact with trees
• The autopilot was in control all the way until after the navigator read 20 meters as altitude.
• The only major intervention into the autopilot might have happened at 10:40:51 when the 2nd pilot issued the goaround command and therefore possibly changed the autopilot mode to goaround.
• As far as I could tell from available documents, entering the goaround mode does not result in any specific sound signal being emitted.
• The Tu-154 radar altimeter clearly has means to set altitude and they are on CVR setting it to 100 meters. And yet, no alarm sounds till they are at around 70 to 60 meters
• Note, however, that this alarm sounds right after the 2nd pilot possibly placed the autopilot in the goaround mode. Why? Is it perhaps that (as I suspect) they stupidly were flying on that radio altitude hold "ground hugging" mode.
• It appears that after entering the radio altitude hold mode, the autopilot will drive the plane into "locking" onto entered altitude and no sound signal is issued after it happens, only the H button will light up when the target altitude is reached.
• However, if the autopilot is switched into the goaround mode, the radio altimeter is no longer used as the control signal, at which point it would sound the alarm if the plane was below the entered value of radio altitude, and this is exactly what happened per CVR.

Please note that it isn't too unlikely that the Tu-154 crews got used to using that H hold autopilot mode even if they did not understand completely what it was for. As in: enter the "decision height" as the target radio altitude and let the autopilot fly the plane down to that height and lock into it. It would work at every airport that has 1000-2000 m reasonably flat terrain before the airport. One problem that I see with that procedure is that regardless of terrain, the descend path is got to be pretty steep if the purpose of that mode was "ground hugging" and not safe landing. The other problem is that if you do ground hugging toward a cliff, it is not going to work out too well. (See Tu-154 crash pictures).