ASN Wikibase Occurrence # 248832
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| Date: | Monday 6 May 2019 |
| Time: | 14:41 |
| Type: |  Piper PA-28-161 Cadet |
| Owner/operator: | Fliegerschule Birrfeld |
| Registration: | HB-PMI |
| MSN: | 2841111 |
| Year of manufacture: | 1989 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Birrfeld Airport (LSZF) -
 Switzerland
|
| Phase: | Approach |
| Nature: | Training |
| Departure airport: | Birrfeld Airfield (LSZF) |
| Birrfeld Airfield (LSZF) | |
| Investigating agency: | STSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On the day of the serious incident, 6 May 2019, the sky was cloudy and isolated clouds caused downdrafts due to evaporated rain in the vicinity of Birrfeld Airfield (LSZF). Visibility was 25 km and a light wind was blowing from the north-north-west.
The Cessna F172N Skyhawk, registered as HB-CNY, was on its way back towards Birrfeld Airfield after a local flight. At 14:38, the HB-CNY flew at an altitude of approximately 3400 ft AMSL into the entry sector West. The crew consisting of a flight instructor and a pilot, who was performing her annual check flight and was seated in the left seat, reported the crossing of sector West on the Birrfeld aerodrome frequency.
At the same time, a Piper PA-28-161 Cadet, registered HB-PMI, was north of the north entry sector and overflew it at 14:39 at an altitude of about 4000 ft AMSL. The crew in this aircraft consisted of two flight instructors, with the pilot seated on the left conducting her training flight for the renewal of her class rating for single engine piston powered aircraft. The entry into Sector North was reported on the Birrfeld aerodrome frequency. The crew stated that they heard the HB-CNY's position reports over Sector West and further into the aerodrome area and saw the other aircraft relatively early and kept it in view.
One minute later, at 14:40, HB-CNY entered the entry circle over the airfield buildings at an altitude of 2790 ft AMSL, which was reported on the airfield frequency according to its crew. Similarly, the crew advised by radio that they would remain in the entry circle as there was another aircraft below them at that time. The centre of the HB-CNY's circle, which was flown to the left, was approximately 400 m west of the entry circle shown on the Visual Approach Chart (VAC). HB-CNY passed the northern apex of this circle at 14:40:34 at an altitude of 2720 ft AMSL.
HB-PMI, which was flying at a ground speed of about 110 kt in the direction of the entry circle, was still about 500 m to the north at the same altitude as HB-CNY at this time. At about this time, warning messages concerning the other aircraft were issued for the first time on both Flarm systems, which were perceived by both crews.
Seven seconds later, HB-PMI crossed the preceding flight path of HB-CNY at an altitude of 2480 ft AMSL. The HB-PMI crew had the HB-CNY in sight slightly to their right, which had already flown a quarter circle further during this time and was now in a southerly flight direction at 2590 ft AMSL.
The pilot of HB-CNY heard the crew of HB-PMI reporting at an altitude of 2600 ft AMSL in the inbound circle and immediately kept a lookout for the other aircraft.
It appeared to the HB-PMI crew that the HB-CNY was higher than them and slightly south-west of the runway axis. They subsequently flew a left turn according to the VAC's entry circle, overtaking the HB-CNY on the left. The crew of the HB-CNY, who had no visual contact with the HB-PMI up to this point, noticed the faster and slightly lower flying aircraft in the immediate vicinity and thereupon flattened the turn slightly in order to avoid the other aircraft.
The closest approach occurred at 14:40:52 with a lateral distance of approximately 200 m and a vertical distance of approximately 30 m. The HB-CNY remained in the vicinity of the other aircraft. The HB-CNY subsequently remained in the approach circle, crossing the flight path behind the HB-PMI.
The crew of HB-PMI flew directly into the counter-approach of runway 26 after half of the approach circle and performed an uneventful touch-and-go landing followed by a landing on runway 26. The crew of HB-CNY also entered the counter-approach of Runway 26 after two complete approach circles and then performed an uneventful touch-and-go followed by four further aerodrome circuits.
Conclusions
The serious incident in which two aircraft came dangerously close to each other over Birrfeld airfield (LSZF) can be attributed to the combination of the following factors:
- The crew of the first aircraft to enter the entry circle flew this circle 400 m to the west, contrary to the instructions on the VAC.
- The subsequent aircraft entering the entry circle overtook the other aircraft and did not follow the procedure with one entry circle.
- The overtaking manoeuvre was carried out without a corresponding agreement between the aircraft.
Accident investigation:
 |
|
Sources:
STSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 15-Mar-2021 19:44 | harro | Updated [Aircraft type, Registration, Cn] |
Corrections or additions? ... Edit this accident description
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