ASN Wikibase Occurrence # 76705
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| Date: | Tuesday 27 December 1994 |
| Time: | 14:34 LT |
| Type: |  Robinson R22 Beta |
| Owner/operator: | B. B. Helikopter AG |
| Registration: | HB-XZW |
| MSN: | 2387 |
| Year of manufacture: | 1993 |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Zürich-Wiedikon -
 Switzerland
|
| Phase: | Approach |
| Nature: | Private |
| Departure airport: | Zürich - LSZH |
| Zürich - LSZH | |
| Investigating agency: | BFU Switz. |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
On December 27, 1994, about 1434 local time, a Robinson R22 Beta helicopter, registered in Switzerland as HB-XZW and operated by B. B. Helikopter, crashed into an apartment building in Zurich, Switzerland, after an in-flight separation of the tail boom. The pilot had been operating the helicopter on a private/pleasure flight.
Witnesses reported that they observed the helicopter roll right and then left, and the tail structure "wig-wagged." The witnesses then heard a loud bang and observed pieces of the tail structure separate from the structure. The helicopter was then observed to pitch forward and fall vertically onto the upper balcony of the apartment building. Pieces of the tail boom and tail rotor were found about 1/4 mile from the accident site.
The private pilot and passenger were killed, and the helicopter was destroyed. The NTSB and FAA participated in the Swiss AAIB's investigation of the accident.
The pilot's experience included 91 flight hours, all in helicopters, with 30 hours in the R22. The pilot had received his type rating in the R22 on December 17, 1994, and had accumulated 5 hours in the R22, 2 weeks before the accident. Zurich ATC had cleared HB-XZW to the Katzensee VFR check point on the pilots' approach to Zurich airport.
Before the crash, witnesses observed the helicopter in level flight at about 1,000 feet agl, and stated that the
helicopter's engine sounded normal. Radar data indicate that the helicopter was traveling at approximately 80 knots before the event. Winds at Zurich, at the time of the accident, were reported from 250 degrees, at 18 knots, gusting to 36 knots. The pilot had acquired a weather report before his flight that indicated that winds were 12 knots; however, the report was a general weather report for all of Switzerland, and not specific to Zurich.
Examination of the wreckage revealed that one of the main rotor blades exhibited red paint transfer that matched the color of the tail boom, 1 inch from the blade tip and extending 52 inches inboard along the leading edge of the blade. The tail boom exhibited compression of bays 3-5 and a swipe on the right side of the boom, which resulted in missing and chipped red paint.
The spindle tusks were fractured and exhibited overload separation fractures. Both pitch change links were fractured at the upper adjustment threads, and one arm of the stationary swash plate was fractured; however, the corresponding pitch change link remained attached to the fractured arm. The pitch change link and swash plate arm fractures exhibited overload separations, and no evidence of fatigue.
A preliminary examination of the engine revealed that the flywheel exhibited damage to the teeth consistent with the engine operating at impact. The governor switch (located on the pilot's collective control) was in the "on" position, and the cyclic control was fractured at the inboard side of the pilot's "T" handle control.
Examination of the helicopter's control tubes revealed no evidence of pre impact failure or fatigue. Small specimens of bird feathers were found at two remote locations on the main rotor blade, which exhibited red paint transfer, and on the engine casing. No other evidence of bird remains or bird blood was found adjacent to the feathers or on any other location of the helicopter. In addition, there was no report of birds in the vicinity at the time of the accident.
The reason for the main rotor divergence that led to the contact with the tail boom has not been determined and the investigation of the accident is continuing. The NTSB received the Swiss AAIB's draft factual report on April 2, 1995.
Accident investigation:
 |
|
Sources:
1. http://www.sust.admin.ch/pdfs/AV-berichte//1658.pdf
2. http://www.swissheli.com/history/hb-xzw.htm
3. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=19878
4. http://www.sust.admin.ch/pdfs/AV-berichte//1658.pdf
5. [LINK NOT WORKING ANYMORE:http://coptercrazy.brinkster.net/search/r22show.asp?start=2351&count=50]
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 04-Sep-2010 12:03 | Alpine Flight | Added |
| 25-May-2016 15:32 | Dr.John Smith | Updated [Time, Operator, Location, Source, Narrative] |
| 25-May-2016 15:33 | Dr.John Smith | Updated [Narrative] |
| 25-May-2016 15:34 | Dr.John Smith | Updated [Narrative] |
| 25-May-2016 15:35 | Dr.John Smith | Updated [Narrative] |
| 22-Sep-2016 13:36 | Dr.John Smith | Updated [Source] |
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