Applicability: SAAB SF340A -004 through -159, SAAB 340B -160 through -459 except -342.-379,-395,-409.-431 and -455.

Effective date: April 20, 2000

Compliance: Required as indicated in SAD No. 1-155.

Remarks: The compliance of this AD must be recorded in Aircraft Logbook, where applicable the requirements of this AD must be integrated into Aircraft Technical Documentation. Address inquiries concerning this AD to: Civil Aviation Authority, Airworthiness Division, Ruzyne Airport, 160 08 Prague 6, Czech Republic, tel: 420 2 33320922, fax: 420 2 20562270.

AIRCRAFT TYPE: SAAB SF 340A and SAAB 340B

SERIAL No's AFFECTED: SAAB SF340A -004 through -159, SAAB 340B -160 through -459 except -342.-379,-395,-409.-431 and -455

SUBJECT: Landing gear - Extension and retraction system - Installation of new circuit breaker for the landing gear function.

BACKGROUND: A number of occurrences have been reported when emergency extension of the landing gears was necessary due to a popped circuit breaker, not possible to reset. That circuit breaker is also common for the Weight on Wheel and Landing Gear Locked Down signals to other systems (i.e. Nose Wheel Steering and Flight Idle Stop).

As a consequence Thereof the Nose Wheel Steering was lost, which in turn reduced the ability to steer the A/C on ground.

To eliminate this type of occurrence a new circuit breaker, supplying 28VDC to the relays that provide the WoW and Landing Gear Locked Down signals to other system, will be added.

REFERENCE DOCUMENTS: Saab Aircraft AB Mandatory Service Bulletin Saab 340-32-120 dated 25, January, 2000

ACTIONS: Perform actions described in Saab Aircraft AB Mandatory Service Bulletin SAAB 340-32-720 dated 25 January, 2000 or later revision

COMPLIANCE TIME: To be performed within 6 months from effective date of this SAD

EFFECTIVE DATE: 2000-02-28