What happened
On April 3, 2009, a Zephyr 2000 ultralight aircraft, registration CS-UOE, departed from Castelo Branco, Portugal, on a recreational flight to Robledillo, Spain. The pilot initially maintained contact with Lisbon Flight Information Service (FIS) and was assigned transponder code 4746. Upon approaching the Monfortinho FIR boundary, the pilot was instructed to contact Madrid Control on frequency 136.525 MHz.
While the pilot could clearly receive all transmissions from Madrid, he was unable to establish bilateral radio communication with Madrid Control or any other station. As the flight progressed through mountainous terrain, the pilot increased the aircraft's altitude to clear the rising terrain, eventually reaching 9,500 feet. At approximately 10NM north of Navas Del Rey, the aircraft's altitude of 9,500 feet resulted in a loss of separation with IFR traffic operating at 10,000 feet within the Madrid TMA.
Following the incident, the pilot landed at Robledillo, where he was questioned by local authorities and provided all necessary documentation and explanations.
The investigation
The GPIAAF investigation, conducted in coordination with the Spanish authority CEANITA, examined air traffic control recordings and the aircraft's flight plan. The investigation confirmed that the pilot had filed an ATC flight plan with the Lisbon ARO, which was transmitted to the relevant Spanish authorities, including Madrid Control. However, Madrid Control reported having no knowledge of the flight plan.
Technical inspections of the aircraft's communication equipment confirmed that the radio was functioning normally and was capable of transmitting on all tested frequencies. Furthermore, the transponder was operating correctly; Madrid Control confirmed they were receiving the aircraft's signal in Mode C, even though no verbal contact was established.
Findings
- The pilot increased altitude from an initial 3,000 feet to 9,500 feet to navigate around increasing terrain elevations.
- The pilot could not establish bilateral radio communication with Madrid Control, despite being able to monitor all transmissions from the controller.
- The pilot attempted to contact various aerodrome frequencies while overflying them, but received no response from any station.
- Evidence from other operators suggested a systemic issue where Madrid Control frequently does not respond to radio calls from VFR traffic, leading pilots to switch to secondary aerodrome frequencies and subsequently lose monitoring of the primary Madrid frequency.