What happened
On 15 July 2010, at approximately 0930 hours, a runway incursion occurred at Singapore Seletar Airport involving a Cessna 172 (registration 9V-FCI) and a Piper 28A (registration 9V-BON).
The Cessna 172 was holding at the northern end of Runway 03/21, awaiting takeoff clearance. Simultaneously, the Piper 28A, operated by a student pilot on his twelfth solo flight, was taxiing on Taxiway W2 toward the same runway.
A simultaneous transmission from both aircraft created a cross-communication. While the Tower Controller heard the readback from the Piper 28A, the Cessna 172 had also received the takeoff clearance and began its takeoff roll. The student pilot, despite noticing that the clearance lacked the standard instruction to backtrack, mistakenly believed the takeoff authorization was intended for him and proceeded toward the runway.
Upon observing the Piper 28A entering the runway, the Tower Controller cancelled the takeoff clearance for the Cessna 172. Both aircraft managed to come to a halt approximately 100 meters apart. There were no injuries and no damage to either aircraft.
The investigation
The investigation focused on the breakdown in radio communications and the decision-making processes of both the pilot and the controller. Investigators examined the student pilot's actions, noting that he had experienced a discrepancy between the controller's instruction and his school's standard operating procedures but chose not to seek clarification.
Regarding the Tower Controller, the investigation looked at the delay in responding to the incorrect readback. While the controller identified that the readback originated from the Piper 28A, there was a 10-second delay before the takeoff clearance for the Cessna 172 was revoked.
Findings
- The primary cause of the incursion was the student pilot's decision to proceed with a takeoff clearance that he found suspicious and inconsistent with standard procedures.
- A cross-communication error prevented the Tower Controller from immediately identifying that the takeoff clearance was being incorrectly acknowledged by the wrong aircraft.
- The student pilot failed to seek clarification despite the absence of a required backtracking instruction.
- The Tower Controller did not immediately correct the readback discrepancy, which is required by the Air Traffic Services Manual.
- The lack of line-of-sight between the Taxiway W2 holding area and the Runway 21 threshold contributed to the difficulty in maintaining situational awareness.
Safety action
Following the incident, the flying school implemented a new requirement for solo student pilots to hold one aircraft length behind the stop line at taxiway holding areas to provide extra braking distance. Additionally, the air traffic control authority has reiterated to all controllers the necessity of correcting any incorrect readbacks immediately.