Investigation Summary
The accident sequence began at 16,500 feet when a short circuit in the right engine oil pressure warning system triggered a master caution. Although the oil pressure gauge showed levels above 30psi (within safe limits), the captain retarded the right engine throttle to flight idle as a precautionary measure before the First Officer could verify the Emergency Checklist (ECL). This action caused the oil pressure to drop further due to the lower engine speed, which the crew misinterpreted as confirmation of a mechanical failure. The captain elected to return to Schiphol rather than continue to Cardiff. During the final approach to Runway 06, the aircraft was in an asymmetric thrust state with the right engine at idle and the autopilot disengaged. The crew struggled to maintain the glideslope and airspeed, relying on ailerons rather than rudder to correct for the pull of the operating left engine. At an altitude of 90 feet, the aircraft had already veered to the right of the extended centerline due to this improper rudder use and the 8-knot tailwind. At 45 feet above the ground, dissatisfied with the approach, the captain initiated a go-around by advancing the left throttle to 98% torque while leaving the right engine at idle. This sudden increase in asymmetric thrust caused the Saab 340B to roll 80 degrees to the right and stall. The aircraft struck a field 560 metres from the runway threshold.
Final Conclusions
The Netherlands Aviation Safety Board (RvdL) concluded the primary cause was the inadequate use of flight controls during an asymmetric go-around, resulting in a loss of control. Contributing factors included the crew's insufficient understanding of the Saab 340B engine oil system, a lack of awareness regarding the consequences of flying with one engine at flight idle, and poor crew resource management. The investigation also noted that the captain had a history of poor performance in engine-out training scenarios, having failed two previous checks and receiving the lowest possible passing grade on his most recent evaluation.
Photographic Evidence (1)
Video Analysis
This Plane Was Flying at a Dangerously Slow Speed — A detailed breakdown of KLM Cityhopper Flight 433, exploring how a false warning light and subsequent pilot errors led to a fatal loss of control during a go-around at Schiphol Airport.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Aged 37; had failed two previous engine-out checks.
First Officer
Aged 34; survived the crash with serious injuries.
Systems & Failure Modes
Engine Oil Pressure Warning System
A system designed to alert pilots to low oil pressure; in this case, a short circuit caused a false positive light despite normal pressure readings on the gauge.
CT7-9B Turboshaft Engines
The Saab 340B is powered by two General Electric engines; the asymmetric thrust produced when one was at idle and the other at full power led to the roll.
Stall Warning System
The system activated during the go-around as airspeed decayed to 105 knots and continued until impact.
Interesting Facts
- 01The aircraft, PH-KSH, was named 'City of Hamburg'.
- 02The right engine oil pressure warning was false, caused by a short circuit in the switchboard.
- 03The captain had previously failed two engine-out proficiency checks during training.
- 04The captain's death was attributed to not wearing his shoulder restraints during the impact.
- 05The first officer survived but suffered from amnesia regarding the accident events.
- 06The aircraft had flown 6,558 hours at the time of the accident.
Safety Actions & Advisories
Training Improvements
Recommendations were made to KLM to improve Crew Resource Management (CRM) and pilot assessment techniques.
Operational Guidance
The investigation recommended improved guidance and training for pilots on flying and landing with an engine at flight idle.