Indonesian B737 runway overrun/crash

[Sinbad1]

Flap Position

PK-KAR
Some insight

Mechanical failure of the transmition;

Retraction of the flaps due to air loads is prevented by a no-back friction brake in the inboard transmission assembly at each flap. If transmission assembly should fail, a torque limiter in the remaining transmission assembly on that flap will stall the flap drive system to prevent structural damage. Stopping the drive system also prevents operation of the remaining flaps, thus maintaining the airplane in normal flight attitude.

Flap Lockouts;
The flap drive system is most susceptible to lockouts in the flaps 30 to 40 range where the highest air loads exist. If the lockout occurs in the flaps 0 to 25 range structural interference, drive gearing failure, jammed transmissions, foreign object damage or hydraulic system failure are the most probable causes If the Flaps did not extend hydraulically or electrically in flaps 0 to 25 range in-flight then Structural failure and/or interference is the probable cause. When the trailing edge flaps are between 1 and 5 units, the control valve fully extend the leading edge flaps and extend all leading edge slats to the intermediate position. When the trailing edge flaps are positioned to 10 units or more, the control valve ports pressure to fully extend all leading edge slats.
If system B hydraulic pressure drops to 2000 psi, the flap and slat actuator blocking valves will hydraulically lock the actuators in the position at which the loss of pressure occurred. This locking action prevents aerodynamic blow back of the leading edge flaps and slats.

T/E Flap must have been selected other wise the slat and the Kruger's will NOT be able to extend.

Flap Load Limit System;

The system is armed When the airspeed switches or the ARINC 429 receiver senses an airspeed in excess of a range of 158 to 162 knots, the hydraulic solenoid valve positions the trailing edge flap control valve to the 30-unit position, As airspeed decreases to below a range of 153 to 157 knots, the solenoid valve is de-energised.

For the flap load system to operate, the Flap Lever must be in the 40 unit detent.

The problem of the Flap last selected position to what ever unit it was, is simply resolved by going to the remaining bits of the Cockpit and you will see the last selected position of the Flap Lever as well as the Flap gauge. I believe the cockpit was not affected, at least that was my understanding.

Having said all that I wonder if we were in the flight crew position, how we would all reacted to all these possibility in the span of few minutes.!! I am sure the flight crew regret some of their decision.