ASN Wikibase Occurrence # 173133
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| Date: | Friday 1 October 1976 |
| Time: | 15:36 LT |
| Type: | Brantly 305 |
| Owner/operator: | Freemans of Bewdley (Aviation) Ltd |
| Registration: | G-ATLO |
| MSN: | 1028 |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Astley, Stourport-on-Severn, Worcestershire -
 United Kingdom
|
| Phase: | En route |
| Nature: | Test |
| Departure airport: | Astley, Stourport-on-Severn |
| Investigating agency: | AIB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
The aircraft was conducting a post-maintenance test flight which departed from Freemans private airstrip at Astley, Stourport-on-Severn, Worcestershire, on 1st October 1976 to investigate abnormal levels of vibration. At some point during the flight the Brantly encountered 'extreme vibration' followed by a loss of control resulting in a crash into a copse.
The accident report reads: "The first impact was with trees which tore away the main rotor assembly together with its gearbox from the aircraft. The fuselage then continued for a short distance through the trees before striking the ground slightly nose down a few yards further on. Although all of the occupants were wearing seat belts, the pilot was knocked unconscious in the impact, the observer was slightly injured and the other passenger was thrown clear into some light vegetation. Immediately after impact the aircraft caught fire but the less injured of the two passengers was able to extricate the pilot before the fire developed. The other passenger made his own way away from the wreckage. The aircraft was severely broken up during the impact sequence and much of its structure was destroyed in the ensuing fire."
The investigation was to discover that the front right main gearbox attachment bolt had failed due to fatigue. The report reads: "The fracture occurred at the shank of the bolt remote from the threaded portion and within the bore of the gearbox flange. A corrosion pit was present at the origin of the fracture. The fatigue exhibited a smooth acceleration in the spacing of the striations to the final instantaneous fracture which was of a tensile nature. The fatigue markings were of a course, banded type and their uniform appearance suggested that they were associated with 'stop-start' transitions in the loading pattern and probably representative of individual flights. A count of the fatigue bands suggested that 90% of the fatigue growth was achieved in 20 to 30 loading cycles. No certainty could be applied to the number of cycles in the first 10% of growth but it was estimated that they amounted to no more than 200 and possibly much less. It was not possible to determine whether the fatigue had been present during the aircraft's long period of storage. A hardness test on the half of the bolt which had not been fire damaged yielded a tensile strength of 74 tons PSI which is within the required specification. The contact face between the gearbox flange and its airframe mounting point showed evidence of hammering which was absent from the other gearbox attachment points."
The registration G-ATLO was, however, belatedly cancelled by the Civil Aviation Authority on 5th December 1983 (over seven years later) as "destroyed". (Presumably, the belated cancellation was due to the CAA's occasional "clean-up/census" of the UK civil aircraft register)
Accident investigation:
 |
|
Sources:
1. http://www.caa.co.uk/docs/HistoricalMaterial/G-ATLO-2.pdf
2. https://www.pprune.org/rotorheads/419023-rotary-nostalgia-thread-16.html#post6174713
3. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=14304
4. https://assets.digital.cabinet-office.gov.uk/media/5422ef22ed915d1374000271/5-1978_G-ATLO.pdf
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 19-Jan-2015 20:38 | Dr. John Smith | Added |
| 19-Jan-2015 20:45 | Dr. John Smith | Updated [Aircraft type] |
| 18-Jul-2015 23:04 | Dr. John Smith | Updated [Time, Source] |
Corrections or additions? ... Edit this accident description
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