Date: 201405
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: Citation X (C750)
Operator: Fractional
Operating under: Part 91
Flight phase: Takeoff / Launch
Aircraft component: Squat Switch
Component problem: Improperly Operated
Reporter organization: Fractional
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Time Pressure; Situational Awareness; Communication Breakdown; Confusion; Distraction; Workload
Second reporter function: Lead Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Other Takeoff Roll
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Equipment / Tooling; Human Factors; Procedure
Primary problem: Human Factors

Narrative: Two Airframe/Powerplant (A/P) Technicians (X and Y) were working a Cessna Citation 750 aircraft at night April 2014 and needed to troubleshoot a system while the aircraft's Weight-On-Wheels (WOW) switch was in the 'Air' Mode. Technician X had installed the WOW switch wedge to simulate this 'Air' Mode/condition. Technician Y was working another item on the same aircraft. Another company aircraft needed immediate maintenance with time restriction for Technician X to arrive onsite that night. The Left-Hand (L/H) Main Landing Gear (MLG) WOW switch wedge was left installed after that particular item was completed. Technician Y 'Released' the aircraft after all maintenance was complete; unaware that the L/H WOW wedge had been installed. Technician X was at another airport working a different tail number as requested.Technician X woke up late the next morning at the away-from-home-base hotel. While driving back to home base; he recounted the previous night's tasks and did not remember pulling the WOW switch wedge. Technician X immediately called Technician Y to see if he had pulled the WOW wedge; he had not. Technician X immediately drove to the home base airport while attempting to call Site Manager to notify him of error. He left voicemails and sent text messages to Site Manager. The Site Manager was working another critical item and was not able to answer. Technician X tried to call Air Carrier Maintenance Control; but had no answer due to their workload at the time. Technician X arrived on site; unaware aircraft had an issue while trying to depart. Technician X removed the wedge and came into the Maintenance office to notify Site Manager and finally spoke to him. The Site Manager notified the Cessna 750 Representative; added a status note into company maintenance computer and recommended to Technician X that he file an NASA/ASRS report. Cessna Technicians who recovered the aircraft were also notified of the error and found that the WOW wedge would cause this failure if left installed. The aircraft was returned to service.[Recommend] attaching red 'Remove before flight' streamer flag to each WOW simulation wedge in tool inventory. Improve turnover/communication between technicians- 'slow down and talk through what work has been done and write all maintenance performed into the discrepancy work detail'. Openly discuss what happened and how to prevent it between all technicians. Maintenance Manager. Takeoff roll; FADEC fault caused by RAT probe heat turning on while on the ground.


Second narrative: Two  Airframe/Powerplant (A/P) Technicians (Tech X and Y) were working a Cessna Citation 750 aircraft at night; April 2014 and needed to troubleshoot a system while the aircraft's Weight-On-Wheels (WOW) switch was in the 'Air' Mode. Technician X had installed WOW switch wedge to simulate this 'Air' Mode/condition. Technician Y was working another item on the same aircraft. Left Main Landing Gear (MLG) WOW switch wedge was left installed after that particular item was completed.


Synopsis: A Maintenance Manager and Lead Technician report how distractions and the lack of adequate communications between two Aircraft Maintenance Technicians (AMTs) contributed to a Weight On Wheels (WOW) switch wedge not being removed from the left Main Landing Gear (MLG) and causing a Cessna-750 (Citation X) to abort a takeoff roll.