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 east/east [compartment]; seeing [that] the vertical gyro was in the rack.

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Original NASA ASRS Text

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

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.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.