PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Flight Crew Commercial
Situational Awareness; Workload
Aircraft Equipment Problem Critical
Flight Crew Took Evasive Action; Flight Crew Landed As Precaution; Flight Crew Diverted; General Maintenance Action
Aircraft
After nearly 2 hours of flight during the descent to my home airport the engine began to shake violently and had a very loud slap/knock. A reduction of power reduced the noise and vibrations. A power setting of about 1300 RPM or more the engine began to shake so violently that it was a concern in my opinion to the airframe. I decide to divert to a nearby airport because it was closer; had more favorable crosswind; and the terrain was lower. The engine instruments and tachometer were normal the tachometer was not indicating a change in or unstable RPM. After landing I check oil level it was still at 6 quarts during the preflight the oil was at about 6.75-7 quarts. There was no obvious external damage to the aircraft.
A PA28-181 Instructor reported a violent; very loud slapping noise during descent with the engine instruments indicating normally so he diverted to a nearby airport for a safe landing.