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.

BLA nr. 1999-154 (A)

Date: November 30, 1999

FOKKER SERVICES B.V.

(formerly Fokker Aircraft B.V.)

Model F.27 Mk. 100 thru 700 series

RLD Type Certificate Nrs.: A22F

Description:

RLD have received a report from an F.27 operator concerning an incident that occurred during a descent to Flight Level 160 where the crew noticed fluctuations of RPM, torque and TGT, as well as zero fuel pressure on the RH engine. Fuel booster pumps low pressure and fuel filter-ice warning lights did not illuminate and the crew decided on a in-flight engine shut-down. The following investigation revealed that both (1 each on RH and LH engine) Fuel Differential Pressure (FDP) switches were inadvertently installed upside-down and that, as a result, the fuel pressure sensing lines were cross-connected to each FDP switch. The subsequent check on other aircraft in the same operator's fleet uncovered three more FDP switches that had apparently been fitted upside down in their mountings during maintenance.

This condition, if not corrected, can result in inadvertent cross-connection of the fuel pressure sensing lines, inhibiting the function of the fuel filter icing warning system. This could leave an ice-blocked fuel filter undetected, leading to fuel starvation and engine flame-out. Since an unsafe condition has been identified that is likely to exist or develop on other aircraft of the same type design, this Airworthiness Directive (BLA) requires a onetime inspection for the correct installation of FDP switches and fuel pressure sensing lines and the reporting of all findings to Fokker Services.

Applicability: Fokker Aircraft B.V. Model F.27 Mk.100 thru 700 series, all serial numbers.

Effective date: December 20, 1999

Compliance: Required as indicated, unless accomplished previously.

(a) Within the next 2 calendar months after the effective date of this directive, inspect all FDP switches and fuel pressure sensing lines for proper installation in accordance with Part 2. Accomplishment Instructions of Fokker Service Bulletin (SB) F27/28-63 dated November 21, 1999 or a later RLD-approved revision;

(1) If the FDP switches and fuel pressure sensing lines are correctly installed, no further action is required and the aircraft may be returned to service.

(2) If FDP switches and/or fuel pressure sensing lines are incorrectly installed, before further flight, re-install in accordance with Part 2.A(4) Accomplishment Instructions of Fokker SB F27/28-63 dated November 21, 1999 or a later RLD-approved revision;

(b) Within ten days after the inspection and/or re-installation as required by paragraph (a) of this directive, report all findings to Fokker Services, address indicated below.

Remarks:

- Operators of the affected aircraft may obtain copies of the referenced service information upon request directly from Fokker Services B.V., Technical Services Dept., P.O.BOX 231, 2150 AE Nieuw-Vennep, The Netherlands, telephone (31) 252-627-350, facsimile (31) 252-627-211.

- Compliance with this AD must be recorded in the proper Aircraft Log Book(s).