Accident Overview
On November 12, 2016, at about 1215 Alaska standard time, a Cessna A185F airplane, registration N4918Q, sustained substantial damage during the landing roll at Ninilchik Airport in Ninilchik, Alaska. The airplane was equipped with a tailwheel and was operated by the pilot under visual flight rules (VFR) on a Part 91 personal flight. A VFR flight plan had been filed, and visual meteorological conditions prevailed at the time of the accident. The flight originated from Soldotna Airport, Soldotna, Alaska, approximately 15 minutes earlier.
Injury and Damage
The certificated airline transport pilot, who was seated in the right seat, and the pilot-rated passenger were not injured. The airplane incurred substantial damage to the right wing and the right horizontal stabilizer.
Landing and Brake Failure
The pilot reported that the touchdown on runway 10, which had a slightly wet gravel surface, was uneventful. However, during the landing roll, the right-side brake system did not function as designed, leading to asymmetrical braking. The airplane subsequently ground looped to the left, and the right wing and right horizontal stabilizer impacted the runway surface. The airplane came to rest on the runway without further incident.
The pilot noted that the previous landing, performed by the passenger, involved no reported brake issues. At the time of the accident, the wind was from the north at 10 to 15 knots.
Post-Accident Examination
A Federal Aviation Administration (FAA) aviation safety inspector examined the airplane's brake system on November 16. The right brake pedal traveled to its full stop when actuated. The inspector removed the right brake master cylinder filler plug and, using a small tie wrap as a dipstick, found no fluid. No fluid leaks were observed on the bottom of the fuselage or the right brake caliper. The pilot stated he had previously checked for fluid leaks under the brake calipers and saw none. The runway was in usable condition, and ice patches on the sides were not a factor.
Subsequent Testing and Repairs
On December 20, the pilot reported that the entire brake system was tested. The right brake showed an extremely small leak—one drop from both o-rings at a pressure of 500 pounds per square inch. The rest of the system appeared normal, and no brake fluid was found on the underside of the fuselage. The pilot assumed the leak was small and only evident under pressure, explaining why preflight checks did not detect it. The o-rings on both calipers were replaced, after which no further leaks were observed.
Further investigation on April 4 revealed that after replacing brake lines, the right brake did not readily accept fluid when pumped from the caliper. The right brake master cylinder was disassembled, and a deformed spring was found. In certain positions, the spring blocked fluid flow.
Pilot's Recommendation
In the recommendation section of the NTSB Accident/Incident Reporting Form, the pilot stated the accident may have been avoided if he had depressed the brakes before landing to confirm both were functioning.
Weather Information
An Aviation Routine Weather Report (METAR) from Homer Airport, approximately 1153, reported wind from 080 degrees at 17 knots gusting 24 knots, visibility 6 statute miles, broken clouds at 3,600 feet, temperature 45°F, dew point 37°F, and altimeter 29.11 inHg.
Additional Information
The FAA's Aviation Maintenance Technician Handbook – Airframe FAA-H-8083-31 (2012) discusses the importance of brake seals, noting that heat and pressure can cause seals to harden and leak. It recommends replacing all seals in a brake assembly with new seals from a reputable supplier, checking that they have not exceeded their shelf life (typically three years from cure date).