ASN Wikibase Occurrence # 318035
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| Date: | Friday 4 July 1958 |
| Time: | 18:45 |
| Type: |  Sikorsky S-58C |
| Owner/operator: | SABENA |
| Registration: | OO-SHK |
| MSN: | 58-363 |
| Fatalities: | Fatalities: 0 / Occupants: 8 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Glabbeek -
 Belgium
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Köln Heliport (Venloerstrasse) |
| Melsbroek (EBBR) | |
| Investigating agency: | AAIU Belgium |
SABENA H917 was a scheduled passenger helicopter flight, linking Köln Heliport (Venloerstrasse) via Brussels International Airport (then at the Civilian terminal on the Melsbroek side - the current Civilian terminal at the Zaventem side would be inaugurated the next day on July 5th) to Brussels City Heliport (Groendreef/Allée Verte). It was the return flight of that day's flight H916 (Brussels City Heliport - Brussels Expo Heliport - Brussels Airport - Köln Heliport).
The accident flight was carrying a single pilot and 7 passengers. About one hour after take-off out of Cologne, the engine suddenly stopped and recaught in flight. Checking his instruments, the pilot saw the engine RPM fluctuate between 2500 and 0 before stabilising once more at 2500 RPM. He switched on the fuel boost and set the fuel mixture to rich, but when the engine RPM started to decline once more, he selected a landing spot, reduced the throttle and commenced an autorotation. Just prior to touch-down, the engine suddenly revved up to 2700 RPM before ceasing after which a flame burst out of the hood. Moments later the aircraft made a hard landing. The pilot pulled the fire suppression switches, cut the mixture and fuel, and switched off the switches and magnetos.
The aircraft sustained major damage as a result of the hard landing. The right main landing gear collapsed; and the main rotor hit the tail, causing the tail assembly and tail rotor to depart the air frame, and three of the four main blades to be destroyed. However neither crew nor passengers sustained any injuries in the accident.
Inspection of the engine showed that piston no.4 had seized in its cylinder. Wear to the piston pin snap ring had allowed the piston pin to work itself loose, until it jammed between the piston boss and sleeve. This seizure caused the connecting rod to fracture.
With no way to tell the damage that the engine had incurred, the pilot initially suspected fuel issues. In response, he enabled the fuel boost pump and set the fuel mixture to rich. However when the RPM then started to decline, he set in an autorotation landing, forgetting about the fuel settings. At the moment he flared the helicopter for landing, the fuel settings caused the engine to resume, destabilising the aircraft. The next moment the engine stalled and the aircraft made a hard touch-down.
CAUSES OF THE ACCIDENT.
The initial cause of the accident was engine failure due to piston seizure.
The main cause is to be found in the sudden recovery of the engine at the moment of the "flare". The torque introduced at this time, unbalanced the aircraft, which, near the ground, could not be stabilised in time and crashed to the ground.
RECOMMENDATION.
Helicopter Flight Manuals should indicate clearly that in the event of an autorotation, the pilot must cut its engine completely, i.e. cutting off the gas, the mixture, the magnetos and close the "shutt of valves".
Following the accident, OO-SHK was rebuilt and re-entered service. However the aircraft was written off after a subsequent accident during a test flight at Evere on May 5th 1961.
Accident investigation:
 |
|
Sources:
https://www.helispot.be/hs/documents/ongevallen/oo-shk.pdf
SABENA Timetables and fares No. 2 - Summer 1958 for flight number and route - http://www.timetableimages.com/ttimages/complete/sn58/sn58-03.jpg
History of this aircraft
Other occurrences involving this aircraft
| 11 March 1958 | OO-SHK | Sabena | 0 | near Hürth |  |
sub |
| 5 May 1961 | OO-SHK | Sabena | 0 | Evere, Brussels | |
w/o |
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Jul-2023 19:46 | Anon | Added |
| 15-Jul-2023 19:46 | harro | Updated |
Corrections or additions? ... Edit this accident description
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