After an (unscheduled) engine change at Groningen Airport (the Netherlands), a Douglas DC-3 had made an uneventful flight to Linköping Airport (Sweden). After landing the aircraft was inspected, and special attention was paid to the left engine, which was changed prior to the flight. The left engine hydraulic pump had been removed previously from the accessory compartment, with the relevant hydraulic lines capped. (this was not recorded in the aircraft technical log, but the crew was informed about this).
The fire damaged engine (© SHK)
The subsequent flight would fly th aircraft back to its home base, Stockholm/Västerås Airport (Sweden). Onboard, two pilots and three engineers.
The engines were started and the necessary checks were carried out, (without remarks) according to current procedures. At 17.51 lt (local time) the aircraft lifted off from runway 11 at Stockholm and climbed out on an easterly heading. During the take-off, the captain heard an unfamiliar sound, which he attributed to a cockpit window or his active noise reduction headset. After landing gear retraction the engine thrust had been reduced to climb thrust, the co-pilot remarks that he smelled something abnormal. Less than a minute later the captain noticed a rattling sound.
As the aircraft climbed through 1000 feet the left engine fire warning was activated, two minutes had passed since take-off. The left engine was confirmed as the engine with the fire warning and power was reduced accordingly. The co-pilot contacted ATC, and after a slight confusion, the flight was cleared to land back at runway 11. The crew never declared an emergency. The engineers in the cabin reported to the flightdeck that they saw flames from the left engine (which was filmed on a mobile telephone). The necessary checklists were completed and a visual approach was flown to runway 11, but the approach was aborted. They were high on speed and the gear was not locked down in time. A new circuit was flown, this time for runway 29, the captain took over control from the co-pilot who had been the pilot flying up to that time. After the engine fire warning had continuously been sounding for close to four minutes one of the engineers turned off the aural wire warning. ATC asked if they needed any assistance, and the crew requested the fire brigade to meet them, as small flames were still visible on the number #1 engine, although the emergency checklist was completed. After the landing, the crew noted that the brakes were not working, and they, therefore, activated the manual hydraulic pump and shut down the running engine. Since the brakes were still not working, it was not possible to steer the aircraft for the last part of the landing roll. This meant that the aircraft came off the runway to the right, and stopped a few metres out on the strip that is covered in grass.
Fire damage in engine zone 2, compared to an undamaged zone 2 (© SHK)
The captain ordered the evacuation of the aircraft, checked if both engines were off and shut down the aircraft. The checklist for an emergency on the ground was not completed. All occupants safely left the aircraft. Within one minute after the arrival of the fire brigade, the fire was extinguished.
An investigation was launched by the Swedish Accident Investigation Authority (Statens Haverikommission - SHK). In addition to the fire damage, it was noted that there were screw joints missing on three of the exhaust collector attachments, which contributed to it coming loose from several connections. The screw and bolt were missing completely in these locations (see figure 6). In the other fittings, the screw joints were correctly installed. The SHK concluded that the incident was caused by the engine change being carried out without following the operator’s established procedures for specially planned repairs. The following factors contributed to the extent of the fire:
The design of the existing hydraulic system does not allow the hydraulic oil to be isolated from engine zone 2.
The failure to close the operating valve of the cowl flaps (item “trail-off” in the engine fire emergency checklist)
No safety recommendations were made. The SHK investigation report is available for the readers' reference by clicking on the .pdf file below;