What was found
WHEN AIR CONDITIONING BLEED AIR TRANSFERRED FROM APU TO ENGINES, REVERBERATIONS COULD BE HEARD AND FELT IN CABIN. UNCLOGGED WATER SEPERATOR DRAIN LINES.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
WHEN AIR CONDITIONING BLEED AIR TRANSFERRED FROM APU TO ENGINES, REVERBERATIONS COULD BE HEARD AND FELT IN CABIN. UNCLOGGED WATER SEPERATOR DRAIN LINES.