“PA-28 AND PA-32 WING SPAR CRACKS: What You Should Know” by Steve Ells
Piper Aircraft Service Letter No. 997, “Wing Removal and Reinstallation”
Piper Aircraft Service Bulletin No. 886, “Wing Spar Inspection”
Piper Aircraft Service Bulletin No. 978A, “Wing Spar Inspection”
and NTSB Preliminary Report (Accident Number ERA18FA120) dated April 4, 2018
