History of Flight
On June 15, 2022, about 1620 central daylight time, a Cirrus SR22, registration N432CD, was substantially damaged in an accident at Gulf Shores International Airport/Jack Edwards Field (JKA), Gulf Shores, Alabama. The pilot and passenger were not injured. The flight was operated as a personal flight under 14 Code of Federal Regulations Part 91 and was destined for Destin Executive Airport, Florida.
The pilot had experienced brake issues on a previous visit to JKA. On April 7, 2022, after landing, he noted soft brakes and requested maintenance. The shop bled the brakes and reported them operational. However, when the pilot returned, he found the brakes dragging and the pedals going to the floor. The shop then rebuilt both brake calipers, replacing O-rings and brake pads.
Following the rebuild, the pilot flew the airplane on about 21 flights. On May 27, 2022, he returned to the same shop for an annual inspection, during which the brake pads were replaced again and the system bled. The logbook entry noted "Operational check good" and "No further defects noted."
On the accident day, the pilot picked up the airplane after the annual inspection. During taxi to the runway, he felt the airplane was sluggish. After applying takeoff power, acceleration was poor, so he aborted the takeoff and taxied off the runway. He called the shop, which asked him to taxi slowly back. When he attempted to move forward, braking effectiveness was lost. He shut off the magnetos, and the airplane rolled to a stop near a taxiway. Smoke appeared from under the airplane; the pilot and passenger evacuated. A fire was observed on the right main landing gear, which the pilot partially extinguished with a hand-held extinguisher. The left main landing gear also caught fire, and attempts with water bottles failed. The pilot called 911 and moved away.
Aircraft Information
The Cirrus SR22 features a free-castering nose wheel, requiring aerodynamic forces and differential braking for directional control during taxi.
Wreckage and Impact Information
Postaccident examination by the NTSB revealed substantial fire damage to the left side of the fuselage and left wing. The hydraulic fluid reservoir contained brake fluid. The parking brake was functional and not engaged. Cockpit hydraulic plumbing showed no leakage; all four master cylinders were intact.
The right main landing gear wheel rotated freely; the brake caliper had surface discoloration on the top third, and the brake line fitting could be moved by hand. The left main landing gear wheel was separated due to thermal damage; the tire, caliper, and brake pads were fire-damaged or missing. The brake line swage fitting required minimal torque to remove.
Flight Recorders
The airplane was equipped with an Avidyne Entegra avionics suite capable of recording flight data. Data showed the airplane powered up at about 1559, began taxiing at 1609, and proceeded to runway 27. During taxi, higher-than-normal power settings were observed, and ground speeds indicated possible brake drag. At 1618, the airplane began a takeoff roll but decelerated after reaching 62 knots airspeed, exiting the runway at 1618:52.
Tests and Research
Brake System Description
The main wheels had hydraulically operated, single-disc brakes with a parking brake mechanism. Depressing the top of a rudder pedal applied the respective main wheel brake. The system used MIL-H-5606 hydraulic fluid.
Examination of Brake Assemblies
Examination at Aircraft Wheel and Brake LLC revealed both brake housings showed extreme heat exposure. The left brake assembly had metallic linings (inferred from lining pins) but the brake disc was part number 164-01501, designed for organic linings, not metallic. This disc was measured below the minimum wear limit for the metallic-lining disc (164-02504). The right brake assembly also had metallic linings and an organic-lining disc (164-01501) similarly worn below limits. The right brake linings were new. The right brake included an aluminum shim (not OEM); the correct shim for metallic linings is insulative and thicker. Pistons from both brakes were designed for organic linings, lacking the recess for piston insulators used with metallic linings.
Maintenance History
Review of maintenance records showed that Cirrus Service Bulletin SB 2X-32-13 (for upgrading to metallic brake linings) had not been documented as performed. The brake discs had been replaced in 2005 and 2017; part numbers were not always recorded. Brake linings were replaced during the June 2021 annual inspection and again the day before the accident, but part numbers were not recorded.