Created Tuesday, Sep 28th 2021 15:32Z, last updated Tuesday, Sep 28th 2021 15:32Z
An ASL Airlines Ireland Boeing 737-400, registration EI-STM performing positioning flight AG-2382 from Leipzig to Cologne (Germany) with 2 crew, was enroute at FL280 when the crew detected that the autopilot could not maintain altitude, switched the autopilot off and attempted to trim the aircraft, however, the stabilizer trim could not be moved electrically or manually (with the trim wheel). The crew worked the related checklist, used the trim cut out switch and continued the flight manually to Cologne using higher than normal control forces. On approach to Cologne the crew found they could not move the flaps beyond position 1, when they attempted to select flaps 5. The crew computed the landing performance at Vref+40=158 KIAS and continued for a safe landing on Cologne's runway 14L.
On Sep 28th 2021 Germany's BFU reported the captain (49, ATPL, 11,980 hours total, 11,750 hours on type) was pilot monitoring, the first officer (29, CPL, 2,084 hours total, 109 hours on type) was pilot flying.
A post flight inspection revealed the mechanism to control the horizontal stabilizer trim was not connected via the relevant cog wheels, the chain and the chain joint/lock were found separated in the forward equipment compartment. Chain and joint did not show any kind of damage.
Prior to the flight there had been maintenance works including works at the horizontal stabilizer manual trim, which should be concluded with an appropriate test. The relevant maintenance work cards were stamped showing the works and tests were completed and checked.
The occurrence was rated a serious incident and is being investigated by the BFU.
