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| Date: | Thursday 21 April 2022 |
| Time: | 15:31 |
| Type: |  Robin DR.400/180R |
| Owner/operator: | Private |
| Registration: | HB-KBK |
| MSN: | 779 |
| Year of manufacture: | 1973 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | 2 km SSE of La-Tour-de-Peilz -
 Switzerland
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Epagny-Gruyères Airfield (LSGT) |
| Epagny-Gruyères Airfield (LSGT) | |
| Investigating agency: | STSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
A Robin DR.400/180R (HB-KBK) and a Socata TB10 (HB-KAU) were involved in a serious airprox incident (ICAO Cat A) near La-Tour-de-Peilz over Lac Léman (Lake Geneva), Switzerland.
The pilot of the Socata TB10 aircraft took off at 14:41 from Grenchen (LSZG) heading towards the Bernese Oberland with a passenger in the right seat. The planned flight route passed through Langnau, Thun, the Gemmi Pass, then through the Rhone Valley to Martigny and Gruyères before returning to Grenchen. Due to more clouds than expected in the Bernese Oberland, the pilot decided to take an alternative route from Thun to Bulle and continued towards Vevey. When HB-KAU reached Lake Geneva, the pilot decided to make a long loop over the Lake Geneva basin near Montreux to show his passenger the Chillon Castle.
At around 14:43, the pilot aboard the Robin DR.400 took off from Gruyères airfield for a local flight. The flight route of HB-KBK passed through Charmey and south of the Col du Jaun. It continued towards Gstaad, the Tsanfleuron Glacier, and the Dents-du-Midi. Above Val d'Illiez, the pilot headed towards Grammont and flew over it in a slight descent at 15:18 at an altitude of 7500 ft AMSL.
Shortly after flying over the southern shores of Lake Geneva, HB-KBK, flying at an altitude of about 6800 ft AMSL, crossed HB-KAU at 15:21, which was approaching from the left at an altitude of about 6700 ft AMSL approximately 2 km south-southeast of Tour de Peilz. At the time of the encounter, the minimum distance between the two aircraft was 31 m vertically and 32 m horizontally.
According to the pilot of HB-KBK, his aircraft's PowerFlarm emitted only a brief audible warning at the moment the two aircraft crossed paths. The pilot of HB-KBK only spotted the other aircraft shortly after the crossing. The pilot of HB-KAU was unaware of the crossing of the two aircraft. Only the passenger of HB-KAU noticed what she thought was a shadow as the two aircraft approaching but was unable to attribute it to a specific danger in flight.
The pilot of HB-KBK indicated that, for the flight over the Lake Geneva region to Châtel-St-Denis, he was listening on the frequency of the Geneva Flight Information Centre (FIC). He also indicated that he either switched to the frequency of the nearest airfield or listened to the Geneva Information frequency and would contact them if necessary. The pilot of HB-KAU was on the frequency of the Lausanne airfield during the crossing. According to him, he always switched to the frequency of the nearest airfield.
After the crossing, both aircraft continued their flight without incident.
Conclusions
The serious incident in which the two aircraft dangerously approached each other was due to the failure of the "see and avoid" concept. Indeed, the two pilots did not detect each other early enough.
The passive behavior of the pilots on different radio frequencies and the absence of two compatible collision warning systems are contributing factors.
Accident investigation:
 |
|
Sources:
STSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 22-May-2024 10:43 | ASN | Added |
Corrections or additions? ... Edit this accident description
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