Accident Overview
On May 27, 2024, at 1145 central daylight time, a Piper PA-28, registration N56466, was substantially damaged during an accident near Taylor, Texas. The aircraft was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91. The pilot and one passenger sustained minor injuries, while another passenger was uninjured.
Events Prior to the Accident
The pilot reported that during the engine run-up, the carburetor heat check produced a backfire-like sound followed by a loss in engine rpm. A second carburetor heat check resulted in normal engine operation. After takeoff, during the initial climb, the pilot noted a decrease in engine rpm. He confirmed that the engine controls were at full forward position and executed a forced landing in a field. During the landing, the aircraft struck the top of a berm, causing substantial damage to the fuselage.
Post-Accident Examination
A review of maintenance records found no entries pertinent to the accident. Visual examination of the engine revealed several discrepancies: the No. 3 cylinder exhaust pipe was missing a mounting stud and associated hardware; the gascolator was not properly safety wired and its fuel bowl showed impact damage; and the carburetor heat valve operated normally but exhibited excessive play in its mounting shaft. The carburetor heat valve's range of motion was limited due to impact damage. Spark plugs were black and sooty, consistent with carbon fouling, and several showed signs of wear with football-shaped center electrodes. Cylinder borescope inspection revealed blackened tops, consistent with a rich fuel-air mixture.
Engine Test Runs
Six engine test runs were conducted; the engine started normally each time, and magneto checks were unremarkable. Throttle movements from idle to full power, both smooth and abrupt, did not cause hesitation or stumbling. During one test run, the carburetor air inlet hose was installed to simulate a collapsed condition. The hose installation was not documented in maintenance records. The damaged engine cowlings and mounts prevented full system assembly; the tube was attached to the carburetor heat box but hung loose. The engine started normally, but the cuffed end of the intake tubing folded inward, restricting airflow and causing a 100–200 rpm drop. This loss could be restored using the mixture lever, though the lever was near the idle cut-off position.
Carburetor Air Inlet Hose Analysis
The carburetor air inlet hose from the accident airplane was sent to Piper Aircraft for examination. It was determined not to be the correct part; it was likely fashioned from a longer section of tubing not meeting Piper's specifications. Compared to a stock part, the accident hose had a hand-cut uneven end, while the stock hose was uniformly cut with a cuffed end and a wire stiffener ending at the cuff. The accident hose's wire appeared to extend to the end. Additionally, its wall thickness was 53% thinner than the correct part, suggesting single-ply material instead of the required double-ply. The correct part is rated for a negative pressure of -24 inches of mercury.
Related Advisories and History
FAA Special Airworthiness Information Bulletin (SAIB) CE-114-23, published August 6, 2014, addresses carburetor air inlet hoses on Piper models PA-28, PA-32, PA-34, PA-44, and PA-46. The SAIB references an accident where a non-approved hose collapsed, restricting airflow and causing engine power loss. It recommends owners verify that an approved Piper hose is installed and in serviceable condition. A review of NTSB data showed three additional accidents (ERA17LA128, CEN17FA139, CEN22LA377) since the SAIB's publication where the carburetor air inlet hose was causal or potentially causal to an engine power loss event.