Qeshm RJ1H at Tehran on Aug 31st 2015, nose gear collapse on landing
Last Update: December 13, 2017 / 20:36:41 GMT/Zulu time
On Dec 13th 2017 Iran's CAO released their final report concluding the probable causes of the serious incident were:
Cause of the collapse of the nose landing gear:
The current information indicates that the likely reason for the collapse of the nose landing gear was that returning the Emergency landing gear lever to its stowed position in the floor by the crew. The main cause of the serious incident was human factor which the pilots did not follow QRH of the aircraft and its precaution. They should evacuate runway with armed Emergency Landing Gear Lever in “up position” to reaching parking area. The installation of the pin in the parking was recommended by the manufacturer to prevent collapse of L/G. The CVR containment confirmed the conclusions.
Cause of the nose landing gear failure:
The leakage from the related internal seal of L/G selector valve caused contamination with hydraulic fluid, which had led to failure of the electric motor to extend L/G completely.
The CAO reported three pilots and two cabin crew were on board of the aircraft only during the test flight. The captain had accumulated 7800 hours total and 4000 hours on type, the first officer 500 hours total and 400 hours on type, the observing pilot had accumulated 8400 hours total and 3500 hours on type. The aircraft had undergone maintenance and was returning to the airline's base.
The crew was on approach to their base when they selected the landing gear down, the landing gear however did not extend. The crew selected the gear lever up and down again, however, again the landing gear did not extend. The crew therefore activated the emergency gear extension causing the landing gear to extend in free fall by gravity. The landing gear was now observed to extend, however, the crew did not receive a down and locked indication for the nose gear on the main indications. Mehrabad Tower confirmed to the crew that all landing gear appeared to be down and in position prior to landing. The aircraft landed normally on main gear and nose gear and slowed, slowing through 35 knots a warning horn began to sound followed by the nose gear's sudden collapse.
The aircraft sustained damage to the nose gear doors and scratches to the forward fuselage. The CAO rated the occurrence a serious incident.
The CAO reported that there is another set of gear indications in the emergency lever compartment. The CAO wrote: "In the event that one of the landing gears is not locked down a continuous horn sounds if the airspeed is less than 145 kt and the flaps are at the LAND setting."
The CAO continued to write: "The landing gear was observed to extend on the Emergency System; however there was no green nose gear ‘DOWN AND LOCKED’ indication on the indicator lamp in the lever compartment. The aircraft touched down normally but, during the landing roll, at a speed of approximately 35 kt, the nose landing gear suddenly collapsed. The noise resulting from the nose underside striking the runway can be clearly heard on the CVR. Also clearly audible is a continuous horn, which started immediately before the collapse. After landing nose L/G collapsed so aircraft stopped on the runway."
The landing gear selector valve was suspected faulty and was sent for analysis. Tests revealed that the selector valve did not move, a failed actuator (motor) was identified. The valve itself was found in working condition. A disassembly of the motor found a significant amount of hydraulic fluid that had leaked into the motor. The CAO wrote: "The origin of the fluid contamination was not determined, although it is unlikely to have been passed via the valve shaft, as the valve seals were in good condition. However, there as a possibility that the actuator became contaminated from a leaking valve to which it was attached during earlier service on a different aircraft."
The CAO analysed referencing the emergency landing gear lever:
The aircraft has landed on RWY 29L. The recorded audio files of the CVR showed that the observer pilot asked the pilot to lower the handle but he refused it, but just seconds later he got permission to lower it. Also the recorded files of the CVR confirm that copilot offered using QRH but both instructor pilots did not commence following the QRH. also knew about lack of Nose Steering.
The abnormal check list of the aircraft Quick Reference handbook (QRH) had some introductions for the pilots for emergency lowering of the landing gears with a simple precaution. Also Flight Crew Operating Manual (FCOM) and other aircraft manuals have some brief review of the landing gear system but have not enough warning or prohibition of stowing emergency handle to prevent landing gear collapse.
The Nose landing gear collapsed just after lowering the handle and aircraft nose scratched on the RWY and stopped.
Three safety recommendations were issued as result of the investigation.
This article is published under license from Avherald.com. © of text by Avherald.com.
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