What happened
On Saturday, November 19, 2011, at 15:30 local time, a Cap 10, registration F-GDTA, was performing aerobatic training maneuvers vertically above the Grenoble Le Versoud aerodrome. After 17 minutes of maneuvers, the pilot observed another aircraft to the left at an altitude of 4,500 ft. The pilot immediately leveled the wings to identify the aircraft and executed an upward and rightward avoidance maneuver. Following the maneuver, the pilot attempted to close the distance to identify the other aircraft's registration and subsequently contacted the aerodrome controller to report the airprox.
Simultaneously, a Robin DR250, registration F-BMZK, was conducting a local flight departing from Annecy. The aircraft was cruising at 4,500 ft, traveling from south of Grenoble toward its departure point. The pilot of the Robin DR250 noted that while they had selected the Le Versoud tower frequency prior to passing over the aerodrome, the frequency was heavily congested. Consequently, the pilot did not identify any announcements regarding aerobatic activity and chose not to contact the controller. The pilot observed the Cap 10 descending from above at a distance of approximately 200 meters but did not perform an avoidance maneuver, deeming it unnecessary.
Video footage from a camcorder installed in the Cap 10 confirmed the close proximity during the avoidance maneuver, establishing a vertical separation of only 31 m and an oblique distance of 107 m.
The investigation
The investigation examined the aeronautical information available to both pilots. The Grenoble Le Versoud aerodrome operates in Class G airspace. The aerodrome's VAC chart explicitly includes a pictogram for aerobatic activity between 2,700 ft and FL070. While this activity was also noted on the SIA 1/250,000 VFR chart, it was absent from the 1/500,000 IGN chart used by the pilot of the Robin DR250. The SIA noted that due to the high density of information on 1/500,000 scale charts, not all specific local activities are represented, which is consistent with ICAO Annex 4 standards.
Findings
- The primary cause of the near-collision was the failure of the pilot of the Robin DR250 to establish radio contact, which prevented them from becoming aware that aerobatic training was in progress.
- The pilot of the Robin DR250 did not identify any specific announcements regarding aerobatic maneuvers due to high frequency congestion.
- Discrepancies in aeronautical chart coverage meant the pilot of the Robin DR250 was unaware of the specific aerobatic activity zones via their primary navigation chart.
Safety action
Since the occurrence, aerobatic activity at the Grenoble Le Versoud aerodrome is now specifically announced via the aerodrome's ATIS.