Synopsis
On a repositioning flight from Jeddah to Riyadh (RUH), a Saudi Arabian Airlines MD-90 was substantially damaged during a runway excursion. The seven crew members escaped unhurt. The incident occurred on runway 15 Left at Riyadh.
Flight and Crew Actions
During the flight, the captain discussed the use of manual spoilers with the first officer. The captain stated that, having only approximately 400 hours in the aircraft as a captain, he wanted to see the effect of landing with manual spoilers. Because it was a repositioning flight and the weather and dry runway conditions were ideal, he elected to land with the auto ground spoiler system unarmed. The approach was uneventful. The Landing Checklist, which included arming the auto ground spoiler system, was completed, but the captain subsequently disarmed the system. The auto braking system was also not armed prior to landing.
Landing and Spoiler Malfunction
Touchdown on runway 15L occurred at an airspeed of 135 knots CAS. The captain manually extended the spoiler/speed brake lever but did not latch it in the fully extended (EXT) position. He then removed his right hand from the lever to deploy the thrust reversers. The first officer observed the lever movement and called "Spoilers Deployed." However, because the lever was not fully pulled aft and latched upwards, it automatically returned to the forward retracted (RET) position. Neither crew member noticed this. The ground spoilers re-stowed before fully deploying, and a speed brake/flap configuration (SPD BRK/FLP CONFIG) Level 1 Amber Alert occurred as the aircraft was not yet fully weight on wheels. Six seconds after touchdown on the right main landing gear, the nose gear touched down, transferring the aircraft to a ground condition and extinguishing the alert.
Runway Excursion
After touchdown, the aircraft banked right and began to drift right of the runway centerline. The captain applied left rudder, deployed thrust reversers, and applied left aileron, but with no noticeable effect. Seeing the approaching G4 taxiway exit, the captain decided to direct the aircraft toward the taxiway to avoid leaving the runway surface beyond that point. He applied right rudder, causing a rapid sweeping turn to the right. The aircraft left the runway at high speed, traversed the full width of the G4 taxiway, and exited the surface at its southern edge. It then entered a sand section and traveled the distance between the edge of the G4 taxiway and the adjacent taxiway GOLF. During this time, the left main landing gear collapsed. The aircraft came to rest on taxiway GOLF. There was no post-impact fire.
Probable Cause
The investigation identified the following cause-related findings: 1. The Captain decided to land with manual ground spoilers when the auto ground spoiler system was fully operational. 2. The initiative by the Captain to conduct this improvised exercise contravened the Standard Operating Procedures (SOPs) and the Flight Operations Policy Manual (FOPM). 3. The auto ground spoiler system was disarmed prior to landing. 4. The spoiler/speed brake lever was partially applied manually after landing. 5. The spoiler/speed brake lever was released before it was fully extended and latched. 6. The spoiler/speed brake lever automatically retracted as per design. 7. The ground spoilers never fully deployed. 8. The loss of lift and aircraft deceleration were greatly reduced by the lack of ground spoiler deployment. 9. Brakes were not used in an attempt to control or slow down the aircraft. 10. The Captain applied a large right rudder input with the intention of directing the aircraft onto the G4 taxiway exit. 11. The aircraft exited the runway at high speed and was travelling too fast to successfully negotiate the right turn onto the G4 taxiway.