Accident Overview
On August 2, 2021, at approximately 1554 mountain daylight time, a Cozy Mark IV experimental airplane, registration N1361S, was substantially damaged during a forced landing near Rushville, Nebraska. The commercial pilot and passenger sustained serious injuries. The flight was operated under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot's Account
The pilot reported that after takeoff, all four cylinder head temperatures (CHTs) were higher than expected as indicated on the engine monitoring device. The CHTs never stabilized or decreased after takeoff. The outside air temperature was 91°F, and the airplane was traveling at about 130 knots. The pilot attempted to reduce the high CHTs using the throttle and mixture controls, but the temperatures continued to rise. The pilot decided to return to the departure airport, but during the flight back, the CHTs kept increasing and the engine ceased producing power.
Forced Landing and Damage
The pilot maneuvered the airplane for a forced landing into an open grass field surrounded by rolling prairie and trees. During the landing, the nose wheel and main landing gear collapsed from impact, and the airplane came to rest on its fuselage. The pilot and passenger egressed without further incident. The composite fuselage sustained substantial damage. The airplane was equipped with a parachute system, which was not activated during the emergency.
Postaccident Examination
Postaccident examination confirmed flight control continuity and airframe-to-engine control continuity. The landing brake, also called the airbrake, located on the bottom of the fuselage forward of the engine, was tested. With power applied, the brake would not fully extend to its normal 45° angle downward. Scraping was observed on the underside of the brake, and the actuator extension tube had play when moved by hand. The airplane had no cockpit indicator for the landing brake position, which was not required.
Further examination of the landing brake actuator at the NTSB Materials Laboratory found the extension tube positioned midway between extended and retracted. The nut inside the actuator was against the lower mechanical stop in the fully extended position, with fractured flanges. No preexisting damage or cracking was observed. The brush attached to the nut was found in the fully retracted position.
Engine examination revealed internal continuity and no signs of fire. The plastic thrust buttons on the rocker shafts were found melted.
Landing Brake Manual Information
The Cozy Mark IV owner's manual states that the belly-mounted landing brake allows a steeper approach and more deceleration in the flare. It is deployed via an electric switch and normally extended on final approach after gear extension, left down until after landing. Maximum allowable speed with the brake down is 90 KIAS. The manual warns that the brake significantly interferes with airflow into the engine cooling NACA duct, and engine temperatures will likely exceed safe limits if the throttle is set above 1500 RPM with the brake extended.