Date: 201202
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Night
Aircraft: B727-200
Operator: Air Taxi
Operating under: Part 135
Mission: Cargo / Freight / Delivery
Flight phase: Parked
Aircraft component: Attitude Indicator(Gyro/Horizon/ADI)
Component problem: Malfunctioning
Reporter organization: Contracted Service
Reporter function: Inspector; Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown; Troubleshooting; Situational Awareness; Confusion
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; General Maintenance Action
Contributing factors: Incorrect / Not Installed / Unavailable Part; Manuals; Procedure; Chart Or Publication; Human Factors; Aircraft
Primary problem: Manuals

Narrative: B727 had an inbound write-up - First Officer Attitude [Direction] Indicator (ADI) had gyro flag in view. Maintenance Control and the local representative for aircraft X agreed to have us change the #2 vertical gyro. The aircraft departed two days later and the [flight] crew wrote up; out-base; [that] the First Officer ADI failed; OK in alternate; out-base placed write-up on DMI. Once in our station; the next night; we again changed the #2 vertical gyro and cleared the deferred MEL. The aircraft flew normal out and back. Inbound on the following night; the crew wrote up: 1) Radar stabilization erratic.2) Autopilot porpoises wildly in Mode-A; in level cruise flight and mildly in B-Mode.3) Captain's airspeed indicator shows VMO flag at all times. The avionics crew discussed this and it was agreed upon by [our] company Avionics Engineering; the local aircraft X representative and their Maintenance Control to change the #1 vertical gyro. The thought was this could cause both problems. Avionics Technician X changed the #1 vertical gyro while Avionics Technician Y and Z changed the Captain's airspeed indicator and pumped the pitot System. Avionics Technician X asked me to get another bolt for the gyro because one was missing. I went to Aircraft X's Stores [Parts] and got him another bolt; with a -8 length. He finished installing the gyro with no difficulties. The [Avionics] crew advised me all three write-ups operational checks [were] good. Aircraft X's Maintenance Control advised us the aircraft had diverted. Aircraft diverted due to both ADIs banked at 10-degrees in level flight. After the other stations Maintenance investigated; they found the #1 vertical gyro had no washers under the head of the bolts; allowing the vertical gyro to move slightly in the rack. While that may have lead to an erratic Captain's ADI indication; it had nothing to do with the First Officer's ADI. Avionics Technician X had installed the #1 vertical gyro and missed putting washers under the heads of the bolts. When all repairs were complete; Avionics Technician Y showed me the operational check of the ADI. Technician Y signed the logbook and I signed the RII block. The other stations Maintenance changed both #1 and #2 vertical gyros. The vertical gyro should have been checked for being secure in the [electronics] rack and I should have checked for it being secure also. I only looked in the E/E [Compartment]; seeing [that] the vertical gyro was in the rack.


Second narrative: A B727 came in with write-ups for radar stabilization erratic and autopilot porpoising. The Representative for aircraft X told us they wanted the #1 vertical gyro changed for this. I; Line Avionics Technician X; changed out [replaced] the gyro and Avionics Technician Y signed it off and Inspector X did the RII. We found out the next night that the gyro was missing washers. Gyro was installed in accordance with Maintenance Manual procedures; Chapter 34-22-21 Removal and Installation. [Procedures were] provided by the Aircraft X's Company. These procedures make no mention of washers and Figure-401 does not show or mention washers.


Synopsis: Two Contract Maintenance Technicians were informed a B727 aircraft had diverted after they had replaced the #1 and #2 vertical gyros.