ASN Wikibase Occurrence # 187457
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| Date: | Thursday 9 September 1993 |
| Time: | 07:10 |
| Type: |  Aérospatiale AS 350B1 Ecureuil |
| Owner/operator: | PLM Helicopters Ltd |
| Registration: | G-PLME |
| MSN: | 2105 |
| Year of manufacture: | 1988 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Lesmahagow, near Douglas, Strathclyde -
 United Kingdom
|
| Phase: | Initial climb |
| Nature: | Cargo |
| Departure airport: | Lesmahagow, near Douglas, Strathclyde |
| Lesmahagow, near Douglas, Strathclyde | |
| Investigating agency: | AAIB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Written off (destroyed) 9-9-1993 when crashed at Lesmahagow, near Douglas, Strathclyde. The pilot (the sole person on board) was seriosuly injured. According to the following extract from the official AAIB report into the accident:
"The helicopter had been engaged in removing sections of dismantled power line pylons as under-slung loads. On the third lift, the helicopter climbed away steeply to clear a power line which was directly ahead. After clearing this, and at a height of about 100 to 120 feet agl., the pilot heard a 'bang' followed by a slight yaw; the ground crew also heard this 'bang' followed by a high pitched whine or whistle.
Almost immediately the low rotor RPM warning sounded and the pilot lowered the collective lever as the helicopter descended rapidly. Although he applied collective pitch again to cushion the landing, the helicopter struck the ground with a high rate of descent but little forward speed.
The engine was examined and revealed that a single blade from the 2nd stage turbine of the gas generator had separated from the disc. After separation the blade had passed rear wards through the power turbine, damaging or breaking off the outer part of every power turbine blade.
The subsequent imbalance in the gas generator rotating assembly was sufficient to break up the rear bearing support structure and cause blade tip rubs throughout the gas generator section of the engine. The damage observed in the engine was sufficient to cause an immediate and complete loss of power.
Examination of the fracture of the blade showed that it had failed initially by fatigue from an origin in the trailing edge side of the aft face of the fir-tree root, at the first serration below the platform. The failure had progressed by a fatigue mechanism forwards and upwards from this point until it had penetrated the platform, after which the final separation of the blade had occurred by fast rupture through the remainder of the blade section.
Examination of the other blades in this turbine assembly showed that a further 7, of the total 27 blades, had started to crack at the same location on the fir-tree root and an 8th had a crack starting on the 3rd fir-tree root serration. It was also noted during this examination that the injection wheel was cracked.
These cracks were not associated with any material defects or deficiencies and the interpretation placed on these findings by the manufacturer was that the engine had experienced a very large number of operating cycles since overhaul and that the turbine blade set had exceeded its safely usable life. Although the 2nd stage turbine blades are not stated to have a specific life, the manufacturer's experience and development testing had indicated that these were satisfactory for two lives of their turbine disc, by implication 12,000 cycles. During the metallurgical examination, the manufacturer established, using a technique they consider reliable, that the turbine blades had run a minimum of 11,820 cycles, evenly divided between two overhaul lives. Research indicates that this was probably the 'lead' engine in the fleet, in terms of 'cycles' and very high time in 'hours'"
Damage sustained to airframe: Per the AAIB report "Aircraft destroyed; structure partially collapsed vertically on impact with the ground". As a result, the registration G-PLME was cancelled by the CAA on 27-10-1993 as "destroyed"
Accident investigation:
 |
|
Sources:
1. AAIB: https://assets.digital.cabinet-office.gov.uk/media/5422eac6e5274a131400002f/AS350B1_Ecureuil__G-PLME_02-94.pdf
2. CAA: http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=14716
3. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=14716
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 20-May-2016 17:24 | Dr.John Smith | Added |
| 20-May-2016 17:45 | Dr.John Smith | Updated [Aircraft type] |
Corrections or additions? ... Edit this accident description
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