BT-1426

Function in the AP-28 autopilot

For the documented 1426A execution, the trim unit enables the electric trim actuator when the autopilot commands a sustained control input, provides the applicable trim indication, introduces the specified time logic and participates in disconnecting the autopilot when control displacement exceeds the permitted condition. It works as one block in the automatic-control chain rather than as a trim motor itself.

Aircraft and system application

AP-28 family documentation and supply records associate the 1426A trim unit with An-26, An-24 and An-32 installations. Applicability can differ by aircraft modification and autopilot execution. The block must therefore be matched with the installed AP-28/AP-28L1 equipment list, the trim actuator and the aircraft wiring diagram.

Identification and compatibility

BT-1426, 1426A-BT and БТ-1426 are useful search forms, but the letter suffix, series and drawing number remain decisive. The related AP-28 system contains other control, amplification and switching units; none is a direct replacement for the trim block. Confirm connector keying, mounting, aircraft effectivity and the full data-plate line before installation.

Inspection and ordering

Inspect the housing, rack fixtures, connector contacts, seals and nameplate. Bench checks must use the approved AP-28 procedure because testing the output logic without the associated circuits can give an invalid result. Specify the complete designation, suffix, aircraft, autopilot version, quantity, condition and required documents in the enquiry. Browse other Electronic Control Units for related system components.