What happened
On May 15, 2022, at 10:12 UTC, a Cessna 172R, registration EC-LJM, and a Beechcraft F33A, registration EC-ESU, experienced a near-collision approximately 11.2 NM west of Cuatro Vientos Airport (LECU). Both aircraft were operating under Visual Flight Rules (VFR) in Class G airspace.
The Cessna 172R was conducting a flight instruction mission, departing from LECU and heading away from the visual approach point W at 2,800 ft. The Beechcraft F33A was on a private flight, returning to LECU and descending from 3,200 ft to 3,000 ft toward approach point S.
As the aircraft trajectories converged, the instructor in the Cessna 172R observed the Beechcraft F33A approaching from the right. To avoid a collision, the crew of the Cessna 172R performed an immediate nose-down maneuver as the other aircraft passed overhead. The pilot of the Beechcraft F33A reported that the visibility of the other aircraft was difficult due to the altitude difference and did not realize a collision was imminent until the maneuver occurred.
The investigation
The CIAIAC investigation examined radar data, flight plans, and pilot statements. The investigation established that the two aircraft were flying at similar speeds and converged at an angle of approximately 71 degrees. Radar data confirmed that at the moment of closest vertical alignment, the Beech and F33A was passing beneath the Cessna 172R.
The investigation also looked into the use of the 131.975 MHz radio frequency. While the instructor in the Cessna 172R had broadcast intentions on this frequency three times, the pilot of the Beechcraft F33A was focused on other frequencies (123.500 MHz, 118.225 MHz, and 121.800 MHz) and did not monitor the unassigned 131.975 MHz frequency. This frequency is used informally by local pilots but is not officially regulated or published in the AIP.
Findings
- The primary cause of the incident was the insufficient external vigilance maintained by both pilots to minimize collision risk.
- The geometric design of the aircraft contributed to the difficulty in detection; the high-wing Cessna 172R had limited upward visibility, while the low-wing Beechcraft F33A had limited downward visibility.
- The use of the unauthorized 131.975 MHz frequency created a communication gap, as the pilot of the Beechcraft F33A was not monitoring it.
- There were no injuries and no damage to either aircraft.
Safety action
- The investigation issued safety recommendation REC 07/24, advising AESA to study and adopt measures to correct the security deficiency regarding the use of the unassigned 131.975 MHz frequency.