20170608008119I

The rt main landing gear (MLG) began to collapse at t/o rotation on rwy 27L, and the rt engine prop struck the runway several times. The plt continued the rotation and t/o, then returned back to mlb for ldg. The acft landed on rwy 27R and taxied back to the FBO ramp it had departed from (near the appch end of rwy 27L) without further incident.

The acft was departing on a local mx flight. A short video taken during the t/o roll by the rt-front seat pax revealed that the gear warning horn was sounding just before rotation and liftoff. The acft then appeared to be starting to rotate when the rt wing began to settle and the prop struck the rwy. The rt engine slowed briefly then regained power as the acft lifted off and began to climb.

The plt rptd that the gear unsafe lt had illuminated when he turned on acft master switch prior to the flt, then went off after he recycled the master switch. He noted that he had visually verified the gear handle was in the down position as part of his ?pre-flight flow?. He went on to state that only the a/c door light was illuminated during the subsequent taxi out to the rwy, and that went out when he shut the a/c off just before t/o. he estimated that gusty wind conditions of 15-22 KTS from 210-220 deg existed during the t/o roll. (The rptd wind at mlb 22 minutes before the mishap was from 210 deg at 15 KTS.)

When asked about the gear horn sounding during the t/o, the plt stated that he was wearing a headset at the time and did not hear it. He expressed his belief that the rt MLG collapsed because the rt MLG gear down microswitch was out of adjustment and the downlock was not fully engaged, which allowed the gear to collapse when he encountered a wind gust from the left side of the acft.

The rt seat pax, a non-certificated mechanic?s helper, rptd that he had observed the plt tap the unsafe gear light, and that the three gear lights were illuminated when the plt pointed them out to him prior to taxi and t/o. the pax noted that gear unsafe light remained on during subsequent taxi and t/o. the pax did not notice if the adjacent gear handle was in the up or down position though.

The rptd purpose of this mx flight was for the pax / mechanic?s helper to mark the throttle positions with tape at a specific low power setting per Piper PA-34-220T m/m procedures, so that the gear warning microswitch in the throttle quadrant could be adjusted by mx personnel after the flt. This was being done to address a prior discrepancy write up where the PIC rptd the horn as sounding during flight.

Subsequent troubleshooting and gear swings by mx personnel with the acft on jacks 2 days before this flt had revealed that the gear warning horn system microswitches required adjustment to the proper setting which led to this flt. The mechanic who performed the troubleshooting rptd that it was only diagnostic and that no gear repair or adjustments were performed at that time. He noted that he visually verified the gear handle was in the down position before the acft was removed from the jacks and moved.

An examination of the acft ldg gear system the day after the incident was performed by an FAA ASI with the assistance of mx personnel, after the acft was placed on jacks. The ldg gear system was operated several times: the gear extended and retracted normally during each test without any issues, and the gear down lights illuminated as each gear locked down. The rt main ldg gear overcenter lock mechanism was also observed closely during of the several gear extensions, and it functioned correctly each time with the downlock hook fully in the locked position and contacting the downlock pin.

A review of the two available taxi paths to rwy 27L from the departure ramp revealed that the acft would have had to make at least one left turn on either path. The rt seat pax reported that the acft made 2 left turns, a 180 degree turn on the ramp and a 90 degree turn on to the taxiway.