Incident Overview
A pilot purchased a helicopter equipped with an undocumented modification designed to restrain the collective. Reportedly, the pilot received no guidance regarding the use of this collective hold-down device. According to the aircraft manufacturer, there existed no Enstrom-approved collective hold-down devices other than the installed friction lock.
Sequence of Events
After engine start, the pilot used two hands to release the collective friction. The Enstrom F28 'Before Takeoff' checklist warns pilots to "keep hand on collective and maintain down position when (collective) lock is disengaged." After releasing the lock, the pilot stated that the collective sprang to the full up position. The aircraft subsequently rolled to the left about its longitudinal axis.
Pilot's Reliance on Modification
The pilot stated that he relied on the modification—a collective hold-down chain—to keep the collective secure. The device was not documented, and its use was not guided by any manufacturer or regulatory instruction.