What happened
On July 21, 2005, at 16:22 UTC, a Cessna C550 Citation, registration CS-DDV, operated by AIR JETSUL, was performing a positioning flight from Faro Airport to Cascais Municipal Aerodrome. The aircraft, carrying two crew members, landed on runway 35 within the normal landing zone.
Upon touchdown, the right main tire suffered a sudden burst approximately two meters ahead of the contact point. The impact caused significant wear to the tire surfaces, with the right tire bursting and the left tire showing heavy surface abrasion. The pilot immediately released brake pressure and used the rudder and nose steering to maintain the aircraft within the runway centerline. The aircraft rolled to a stop near the opposite end of the runway, which caused a temporary closure of the aerodrome until the damaged tire could be replaced.
There were no injuries to the crew and no damage to the aircraft or third parties.
The investigation
The GPIAAF examined the wreckage and the aircraft's maintenance records. Inspection of the right main tire revealed heavy friction wear and cuts through the outer eight plies, characteristic of a locked-wheel condition. The left tire showed similar, though less severe, surface wear.
Maintenance personnel conducted a thorough examination of the braking system, including the anti-skid unit, and found no mechanical anomalies or malfunctions. The aircraft's documentation showed no previous history of braking or anti-skid system failures. The investigation also confirmed that the anti-skid system was armed and functional, but it could not engage because the system only activates once the wheels reach a speed of at least 35 knots.
Findings
- The pilot in command was resting their feet on the brake pedals with enough pressure to actuate the master cylinders during the landing roll.
- This pressure caused the wheels to lock immediately upon touchdown.
- Because the wheels were not rotating at the moment of contact, the anti-skid system could not activate, as its sensors require a minimum wheel speed of 35 knots to function.
- The resulting wheel lock caused intense friction and abrasion, leading to the burst of the right main tire.