On May 21, 2010, a CESSNA C152 (registration CS-ASQ) operated by Private was involved in an aviation accident near Cascais, PT. No fatalities were reported. Investigators recorded the probable cause as: The incident was caused by the unauthorized entry into the active runway, as the pilot did not understand and internalize the content of the message he had received and of which he gave the understood. This summary draws on records from the Portuguese Office for the Prevention and Investigation of Accidents in Civil Aviation and Rail (GPIAAF).
On 21 May 2010, a Cessna 152 (CS-ASQ) entered a runway without authorization at Cascais Municipal Aerodrome, forcing an aircraft on final approach to execute a go-around. The incident was classified as serious.
Incident Overview On 21 May 2010 at 12:32 UTC, a Cessna 152, registration CS-ASQ, operated by Gestair Flying Academy, entered a runway without authorization at Cascais Municipal Aerodrome. The aircraft was conducting a local training flight with a student pilot flying solo. The unauthorized entry forced another aircraft on final approach to perform a go-around. No injuries or damage were reported. ## Flight History The student pilot contacted Ground Control at 12:08 UTC to request engine start authorization for a local flight in the Cascais area. Approximately ten minutes later, the pilot requested taxi instructions. The controller issued instructions to taxi to the holding point for runway 17 via G and hold short of the runway. The pilot was unable to provide a correct readback, citing radio equipment problems, and requested the instructions again at 12:20 UTC. The controller repeated the authorization, but the pilot again failed to read back correctly, responding only with “copy.” At 12:28 UTC, the pilot reported ready for departure. The controller provided departure instructions to turn right to Cascais Bay and climb to 1,000 feet. At 12:29 UTC, the controller instructed the pilot to hold short of the runway and contact Tower on 120.3 MHz. The pilot first contacted Tower at 12:30 UTC, reporting at the holding point for runway 17 and ready for departure. Tower, handling heavy traffic, instructed the pilot to hold short of the runway. At 12:31:49 UTC, the pilot reported at the holding point and ready for departure, and provided a correct readback of the instruction to hold short. Without receiving further instructions, the aircraft entered the runway and taxied to the takeoff position. Tower called attention to the unauthorized entry in Portuguese and instructed another aircraft to perform a go-around due to the runway obstruction. After takeoff, communication difficulties continued, and the school requested that the pilot be instructed to return to the aerodrome for a final landing. ## Aerodrome Cascais Municipal Aerodrome is part of the national aerodrome network and is available for all VFR and IFR traffic, as well as ultralight operations, within published hours. It provides flight information services, meteorological information, and fire-fighting category 3. The aerodrome is controlled, and aircraft must be capable of maintaining two-way communications with Tower and Ground Control. The Cessna 152 was parked at ramp B2, which serves the school to which it was assigned. The aircraft was authorized to taxi along the route shown in green in Figure 1 of the report. From the holding point for runway 17, the aircraft was to transfer to Tower control and await authorization to enter the runway and proceed to the takeoff position (backtrack). Without receiving such authorization, the aircraft entered the runway and interfered with traffic on approach, forcing one aircraft to perform a go-around and causing delays to other aircraft on approach. ## Pilot The pilot in command was a 38-year-old Portuguese male student pilot authorized to attend the ATP(A) 02/09 EAA pilot training course conducted by Gestair. He had completed an aeronautical medical examination on 4 February 2010 and obtained a class 1 medical certificate valid until 26 February 2011, without restrictions or limitations. His academic record showed a total of 15.77 flight hours, of which 1.58 were solo, with a total of 69 landings. His performance was normal, and he had been released with 10.94 hours and 42 landings. In the theoretical portion, he had successfully completed the approved syllabus and obtained the following grades in various subjects, as shown in Figure 2 of the report. ## Analysis ### Radio Communications The flight was part of the course program and had been properly planned and authorized by the responsible parties. According to school regulations, communications between aircraft and air traffic management units were to be conducted in English using ICAO-recommended phraseology. The student pilot had completed the study of communications-related subjects and had obtained approval from the regulatory and licensing authority, but had some difficulty mastering the English language. Analysis of the communication records highlighted the pilot's difficulty in understanding and expressing himself in English. He showed knowledge of the most common expressions used in aeronautical phraseology, pronouncing them clearly and promptly, but at the same time showed signs of slowness in assimilating the phrases directed at him, possibly because these were concrete, directly associated with the situation, and not abstract, as they usually appear in manuals. This difficulty was compounded by the fact that the Ground Control controller spoke very quickly, which made it even more difficult to understand his messages. In the situation, the pilot should have asked the controller to speak more slowly or reverted to communications in Portuguese, where he would have more ease of assimilation. In turn, the controller, faced with the difficulties manifested by the pilot, should have altered his diction, speaking more slowly, so as to allow the pilot to understand the messages, especially since the volume of traffic at that time (on that frequency) was relatively low. In an extreme case, he could have suggested a change to Portuguese or, as a last resort, sent the pilot back to the parking area. The controller on duty at the Tower position had a more friendly approach. Despite having a lot of traffic in the aerodrome area and maintaining fluid control, using clear and rapid language, upon becoming aware of the pilot's difficulties, he began to speak more slowly, so as to be understood and obtain correct readbacks, even switching to Portuguese when he needed to draw the pilot's attention to the seriousness of entering an active runway without proper authorization. Considering that the pilot provided a correct readback of the Tower instructions, his entry into the active runway seems to be justified only by not understanding what was being transmitted to him, limiting himself to pronouncing the “standard” responses from the manuals. ## Conclusions ### Established Facts 1. The flight was authorized and was part of the program of the course attended by the student pilot. 2. The student pilot was duly authorized to attend that course and was complying with his schedule of training flights. 3. The student pilot was conducting a solo flight and all radio communications were made in English. 4. From the first communications, the student pilot demonstrated difficulty in assimilating the messages directed at him. 5. The controller on duty at the Ground Control position used a very high rate of diction, which further complicated the student pilot's understanding. 6. On several occasions, it was necessary to repeat the instructions before the student pilot gave a conforming and acceptable response. 7. When the aircraft reached the holding point for runway 17, the student pilot, despite having repeated the authorization that limited his entry to the runway after receiving explicit instructions to do so, did not correctly interpret that message and entered the runway without express authorization. 8. This intrusion forced an aircraft, which was on final approach, to perform a go-around maneuver, as a traffic conflict was created between aircraft. ### Causes of the Incident The incident was caused by the unauthorized entry into the active runway, as the pilot did not understand and internalize the content of the message he had received and of which he gave the understood.
Probable cause
The incident was caused by the unauthorized entry into the active runway, as the pilot did not understand and internalize the content of the message he had received and of which he gave the understood.