190-01182-02
GTR 225/GNC 255 TSO Installation Manual
Rev. F
Page viii
GTR 225/GNC 255 HARDWARE MOD LEVEL HISTORY
The following table identifies hardware modification (Mod) Levels for the GTR 225, GTR 225A,
GTR 225B, GNC 255A, and GNC 255B. Mod Levels are listed with the associated service bulletin
number, service bulletin date, and the purpose of the modification. The table is current at the time of
publication of this manual and is subject to change without notice. Authorized Garmin sales and service
centers are encouraged to access the most up-to-date bulletin and advisory information at Garmin’s
using their Garmin-provided user name and password.
Mod
Level
Service
Bulletin
Number
Service
Bulletin
Date
Purpose Of Modification
1
SB 1404
2/7/14
Some GNC 255 units may require upgrade to MOD 1 to
prevent incorrect VOR or Localizer deviation indication in
certain limited conditions.