Incident Overview
An aircraft on a planned flight from Avignon Airport, France to Blackpool Airport, UK, with two flight crew and two passengers, encountered a hydraulic system malfunction during descent. The crew reported fluctuating hydraulic pressure and intermittent low pressure cautions. The aircraft overran the runway after landing, resulting in substantial damage but no injuries to occupants.
Flight Sequence
The co-pilot performed external checks, including hydraulic reservoir fluid level as per the pilot checklist. The aircraft was refueled to 3,000 lb and departed uneventfully. Prior to descent, the crew noted ATIS information for Runway 10: wind 150° at 18 kt, visibility 9 km, few clouds at 2,000 ft, temperature 11°C, dew point 8°C, QNH 1021 hPa, runway damp. The commander planned an NDB approach with autopilot engaged.
Hydraulic Issues
While descending through FL120, left then right hydraulic low pressure cautions illuminated. The hydraulic pressure gauge showed pressure cycling, mostly around 2,800 psi (green arc). Cautions intermittently appeared and extinguished, left more often than right. The co-pilot initiated the HYDRAULIC PUMP FAILURE checklist, which stated flight could continue if pressure was at least 2,800 psi.
Near the Blackpool NDB, the commander remarked "it's dropping," followed by roll fail and speed brake fail cautions. The co-pilot actioned applicable checklists, indicating landing distance required (LDR) increases of 65% and 21%. Using the larger 65% increase, the crew calculated LDR of 5,950 ft; runway LDA was 6,131 ft, so they continued. The roll fail checklist required a flaps-up landing, with VREF of 132 kt including a 20 kt increment.
Landing and Overrun
At about 4 nm on final, the co-pilot lowered landing gear on commander's request. About 8 seconds later, the commander said "just lost it all" regarding aircraft state. The landing gear unsafe aural warning sounded as main gear did not indicate down and locked. Descending through 1,000 ft, the commander asked for alternate gear extension checklist, then discontinued approach by selecting ALT HOLD and increasing thrust. Before the checklist could be actioned, the main gear indicated down and locked. The commander disconnected autopilot and continued.
ATC cleared the aircraft to land with wind 140° at 17 kt (headwind ~10 kt, crosswind ~12 kt). At 500 ft MDA, 1.5 nm from threshold, the commander instructed co-pilot to advise ATC of hydraulic problem and request RFFS standby. The aircraft touched down about 1,500 ft from paved surface start at 132 kt airspeed (124 kt groundspeed). The commander applied toe brakes but felt no significant retardation; no emergency brakes were applied. The co-pilot attempted lift dump, but it failed due to lack of hydraulic pressure. A MAYDAY call was made while on the runway. As overrun seemed likely, the commander shut down engines. The aircraft overran the end at about 80 kt groundspeed. The commander later reported being in a "state of panic" and unsure whether he applied emergency brakes. After leaving pavement, he steered slightly right to avoid a downslope. The aircraft crossed rough ground, causing nose gear collapse and severe damage to wing-to-fuselage attachments. Occupants vacated via entry/exit door and moved upwind; RFFS arrived shortly after.
Probable Cause
The official findings stated that the crew performed the reservoir level check per checklist and found it correct. Evidence of hydraulic leakage was visible in the left engine nacelle. Hydraulic pressure fluctuations and intermittent cautions occurred. When landing gear was lowered, hydraulic pressure dropped completely due to cavitation and leakage. Pump port cap failure with multiple-origin cracking propagating from thread root pitting was identified. The load from the compensator plug fitting placed the thread under constant tensile stress during operation, leading to failure.