Page:CAB Accident Report, Slick Airways Flight 25C.pdf/10

-10- instance, at the middle marker. The controller shall then continue to monitor the aircraft's position and so advise the pilot whenever a radar observation reveals situation which, in the judgment of the controller, is likely to affect the safety of the flight.

The transcript of communications of the PAR controller and Slick 40Z disclaim that the flight did not report having the approach lights or runway in sight and that the PAR controller failed to advise the flight that radar advisories were be terminated.

The aircraft first struck the approach lights at a point which was 109.3 from below the glide slope and 1,100 feet from the end of the runway. Had the controller been monitoring the approach as he stated, he should have observed the aircraft dangeroux descent below the glide slope and should have advised the crew. There it can only be concluded that he failed to monitor the flight during that portage of the approach from the middle marker to the point of contact with the approach light, an estimated 11 seconds.

It is apparent that the flight continued to descent following passage of the middle marker and was following the approach lights while entering a condition of restricted local surface visibility. Although the aircraft was aligned with the runway of intended landing, the crew did not have adequate visual reference during this phase of the approach due to the fog condition and permitted the aircraft to descend into the approach lights.

Another factor which may have contributed to the accident was the possible of functioning sequence flashing lights. From 1140, when weather improved sufficiently along runway 28R for additional approaches, until 1207, the time of the dent, three air carrier aircraft made instrument approaches to runway 28R. The crews of these aircraft reported that the high intensity lights of the ALDS were lighted, but none remembered seeing the SFL in operation. When Slick 40Z struck the approach lights at 1207, substantial damage to the lights occurred and the tire light system went out. This should have activated the alarm on the control panel in the tower cab, but investigation revealed that the warning buzzer was heard by controller personnel in the tower. Tower personnel were not aware of malfunction of the ALS/SFL System until approximately 3 hours and 20 minutes after the accident, at which time they were notified by an FAA technician that the ALS had been damaged and was inoperative. FAA personnel who checked the ALS/SFL System after the accident established that no malfunction was found in the alarm system. The Board believes that the outages of the ALS/SFL System were not discovered by tower personnel because the buzzer was turned too low; hence, a failure of the prior to the time of the accident would have been undetected for the same reason.

The pattern of heavy damage inflicted by the main and nose landing gears of the aircraft struck the approach lights corresponds to an aircraft bank angle 3 degrees right wing down at a nearly nose level attitude. The fracture angle the nose gear sliding door to the nose gear strut fairing attachment hinge beat indicates a rearward movement of the nose gear strut to at least 35 to 40 degrees from the vertical. Since the strut, in its down and locked position, has a form rake of 12 degrees, the total rotation of the strut was 47 to 52 degrees. This amount of rotation was sufficient to penetrate the flight deck flooring, causes substantial damage to the control cables and hydraulic lines which are routed in this area. Therefore, it is concluded that following initial impact with the approach lights, the airplane was no longer fully controllable.