Piper PA22 N3604A accident near Soldotna, Alaska

Probable cause

The delamination of the fabric material from the fuselage above the windscreen due to failed adhesive, which resulted in disrupted airflow and a subsequent hard landing.

NTSB analysis

In cruise flight, the private pilot heard and felt a “pop” emit from the airplane. He immediately noticed the airplane descending but verified he still had elevator continuity. Unable to maintain altitude, the pilot made an emergency landing on a nearby paved road; however, the airplane landed hard, and the main landing gear collapsed.

Postaccident examination revealed control continuity, but it was noted that the adhesive adhering the fabric above the windscreen had separated.

FAA Airworthiness Directive (AD) 74-17-04 applies to certain Piper airplanes, including PA-22 series airplanes that are covered with cotton or linen, and was issued to prevent the sudden failure of the material at the top of the windshield by requiring the installation of a reinforcement metal strip. Because the accident airplane was covered in a heavy-duty polyester material, the hardware specified in the AD was not required for installation on the airframe nor was it installed.

It is likely that the adhesive adhering the fabric above the windscreen delaminated and disrupted the airflow over the airplane. It was not determined why the adhesive failed/delaminated.

Text from the NTSB. Open the NTSB docket for ANC20LA064 for the full record.