AIRWORTHINESS DIRECTIVE

CAA-AD-023/2002

Date of issue: February 21, 2002

AIRCRAFT - PROPELLERS - PITCH CHANGE SYSTEM COMPONENT (ATA 61) - REPLACEMENT

Applicability: ATR 72-101, -102, -201, -202, -211, and -212 model aircraft.

Effective date: April 18, 2002

Compliance: Required as indicated in DGAC AD 2002-073-063(B).

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.

Ing. Pavel MATOUŠEK

Director of Airworthiness Division

CAA CZ

DGAC AD No.: 2002-073-063(B)

ATR

ATR 72 aircraft

Propellers - Pitch change system component (ATA 61)

1. APPLICABILITY:

ATR 72-101, -102, -201, -202, -211, and -212 model aircraft.

2. REASONS:

During years 1999 and 2000, three cases of propeller pitch lock during final approach, have been experienced on ATR fleet. During two of these events the asymmetric power resulting from the propeller pitch lock was not recognized by the crew during landing and the aircraft veered off the runway after selection of reverse power while the "Low Pitch" condition was not effective for both engines.

On one case the investigation led on the suspected components of the propeller pitch control system showed significant anomalies on a Pitch Control Unit (PCU) servo ball screw. The hang up and the loss of efficiency noticed on the test bench are due to ball screw contamination. On aging PCU fitted on 14SF11/14SFL11/247F-1 Hamilton Sundstrand propellers, these anomalies could contribute to a pitch lock condition especially when they combine with another propeller component failure of the pitch control system.

The actions rendered mandatory by this Airworthiness Directive (AD) are intended to clean the ball screw in order to avoid a propeller pitch lock situation and reduced controllability of the aircraft during landing.

3. ACTIONS:

The following measures are rendered mandatory from the effective date of this AD.

Before reaching 10,500 FH since new or since last Critical Parts Inspection (CPI) or in case of contamination or following anomalies noticed during Production Acceptance Tests (PAT), perform, according to the temporary revision No. 61-6 of the PCU Component Maintenance Manual 61-21-07, the ultrasonic cleaning of PCU servo ball screw installed on HAMILTON SUNDSTRAND 14SF11/14SFL11/247F-1 propellers.

Note: The actions mandated by this AD complete the prescriptions of the AD 2002-072-064(B).

REF.: HAMILTON SUNDSTRAND CMM 61-21-07.

EFFECTIVE DATE: FEBRUARY 02, 2002