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| Date: | Saturday 26 April 2025 |
| Time: | 09:52 UTC |
| Type: |  Piper PA-18 |
| Owner/operator: | Aéroclub de Genève |
| Registration: | HB-OKB |
| MSN: | 18-8884 |
| Year of manufacture: | 1970 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Colle Sesia -
 Switzerland
|
| Phase: | Take off |
| Nature: | Private |
| Departure airport: | |
| Investigating agency: | STSB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
A Piper PA-18 Super Cub (registration HB-OKB), owned by the Aéroclub de Genève, while conducting a flight in the Monte Rosa massif in the Swiss Alps performed a landing on a snow and ice-covered slope near Monte Rosa. During the subsequent takeoff maneuver, the aircraft passed in close proximity to a group of ascending ski mountaineers traveling in a single-file formation.
The pilot and the passenger had been on a private alpine flight since early morning, flying to various glacier landing sites. The flight, including several breaks, lasted about 2½ hours and was performed at an altitude of over 10,000 ft AMSL. The occupants did not use oxygen. The pilot then landed on Colle Sesia at around 14,000 ft AMSL. The subsequent take-off run down the glacier slope took more than twice as long as expected by the pilot, and the aircraft crossed a group of ski tourers who were taking part in an alpine competition with finish point Capanna Margherita.
Light katabatic winds (cold downdrafts) prevailed on the glacier at Colle Sesia.
Hypoxia (oxygen deficiency) and its consequences can occur at altitudes as low as 6,000 ft AMSL with varying degrees of severity. A rapid climb can exacerbate the symptoms. Among other things, hypoxia can lead to a reduction in brain performance that is not noticed by the affected person.
Sources:
https://comunicati.enac.gov.it/it/announcement/attachment/14583
https://www.rsi.ch/info/svizzera/Monte-Rosa-aereo-sfiora-scialpinisti-parte-un%E2%80%99indagine--2787334.html
https://torino.corriere.it/notizie/piemonte/25_aprile_27/monte-rosa-aereo-ultraleggero-atterra-a-pochi-metri-dagli-scialpinisti-che-imprudenza-s-e-rischiata-la-tragedia-c57ba733-5f5b-4616-ab07-65ebe1698xlk.shtml
https://www.sust.admin.ch/inhalte/AV-Praeventions-Bulletins/Praeventions-Bulletin_2025_2_e.pdf
History of this aircraft
Other occurrences involving this aircraft
| 26 May 2025 | HB-OKB | Aéro-club De Genève | 0 | Mens Altisurface |  |
sub |
Location
Media:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 07-May-2025 07:37 | YacineBoussoufa | Added |
| 15-Aug-2025 07:04 | ASN | Updated [Time, Total occupants, Location, Source, Narrative, ] |
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