Boeing 737-400 belong to Adam Air with flight number DHI-574 missing in flight route between Surabaya and Manado in 1st January 2007 reported by KNKT, Indonesia Safety Transportation Commission in Jakarta 25/03/08. According to Mr. Tatang Kurniadi, the head of department, the situation was started from bad weather and onboard IRS navigation system in malfunction. The IRS(Inertial Reference System) usually used to locate aircraft postion and speed measurement. The captain pilot, Refri A Widodo and Copilot Yoga tried to eliminate the IRS malfunction and ignored other instruments. In ussual condition, need only one pilot to fix the problem not both of them.
The red light beam warned the pilot if there is something wrong with the System. The pilot found that the IRS cause the flash light on the cockpit and try to eliminate it. He turned off the navigation system to attitude which mean the autopilot is being disengage. The plane was slowly roll to the right. Both the pilot was in spatial disorientation state and didn’t realize the airplane roll. When the airplane in 35 degrees to the right angle, warning flash light shouted in the cockpit. The pilot was doubt to turn the wheel drive to the opposite/cross side and turn the wheel to the same angle made it in 100 degree angles to the right. When The aircraft in 100 degree in right angle, the airplane was automatically making a steep dive to 60 degree of angle with autopilot disengage. The airplane rolled to the right for every 1 degree/seconds. The airplane was flown in less than 35,000 feet when entered the IRS malfunction.
In the situation, the pilot must do an opposite roll to balance the airplane when reaching 60 degrees to the right/left angle.
Due to accidentally or not, the pilot didn’t try to reduce the airplane speed. The airplane was cruising in fast heading to the ground(wide opened sea) uncontrollable. The speed was reaching Mach 0.926(+/- 1,100 km/h) which normally allow was Mach 0.82(+/- 900 km/h). Few minutes later, both the horizontal and vertical tails were ripped off. The aircraft was experiencing structural severe damage and out of control. The airplane hit the sea in more than 60 degree of steep dive and 100 degree to the right angle in almost reaching sound of speed.
Follow Up Action
According to KNKT investigation, lack and might out of maintenance procedure by airline are pushing the matter to the surface. DEPHUB(Departemen Perhubungan) said they will inspect the airplanes components maintenance in every 3 months. And others are training the pilot crew how to handle the critical situation during flight. In Adam Air case, the navigation system error has been reported for 154 times without taking any repairmen action by the firm.