Originally Posted by
megan
fdr, thanks for putting me straight, you'd think a FW (prop) carrier qualified guy would have thought of that.
You asked re USAir 1549's impact. The NTSB report does not provide the DFDR readout however the following is the basic info:
last recorded speed at 12' 128kts. (not specified as CAS or GS, either could have been used in the reconstruction).
Time to stop from impact: 5 seconds approximately
Sink rate at touchdown 12.5 FPS (750FPM)
Certified ditching sink rate 3.5FPS (210FPM)
Wind was a crosswind (recorded at central park)
2.2g average deceleration gives 200 meter from impact to stop. Peak longitudinal g loads would occur at first contact and at the point the nose enters the water. vertical load was substantial at touchdown, the aircraft was in alpha protection, about 3 deg AOA less than stall AOA and being protected by the control laws.
Video from approximately normal to the flight path shows the aircraft comes to a halt in around 5 to 6 fuselage lengths, the fuse is 37.57m in length.
Sully's decision to go into the river was a good decision. The consequence of a failed attempt back to LGA or to try for TEB would have been devastating to the pax and to the city. The ATSB report shows that with the decision time needed for real crew to respond to a sudden emergency, LGA/TEB were not likely to be successful.
In Lion Air and PX, we have seen the results in inadvertent ditching (crashing into the water) with the gear down. In both cases, the outcome has been much better than would be expected from a gear down ditching.
In your turboprop, there is a near certainty that the props are going to take the gearbox and prop off the front of the engine unless feathered. If there is power on at impact, they are going to go walking, and a US type RH rotation prop is going to to have the left side props walk off towards the fuselage.
