Attention:
Operators and maintainers of de Haviland Dash-8-400 And Dash-8-100/-200/-300 Series aeroplanes centre wing flight control pulley and bearing systems.
| File Classification No.: | Z 5000-35 |
|---|---|
| RDIMS No.: | 20681910 |
| Document No.: | CASA 2025-11 |
| Issue No.: | 01 |
| Effective Date: | 2025-10-22 |
Purpose:
The purpose of this CASA is to provide awareness to Operators and Maintenance personnel of a corrosion condition affecting certain flight control pulleys and pulley bearing assemblies installed on the Dehavilland Canada (DHC) DASH 8 100/200/300/400 series aeroplanes.
Contexte :
A number of service difficulty reports (SDR) have highlighted concerns with corrosion of flight control pulleys and pulley bearing assemblies as follows
- SDR 20230808002 - The flight crew reported the autopilot disconnected in flight, subsequent operation of the aeroplane manual roll control presented with some resistance. The flight continued and the aeroplane landed without further incident. Inspection found corroded/failed bearings on both the upper and lower pulleys on the RH wing aileron cable. The upper and lower pulleys were found contacting each other.
- SDR 20230724008 - Roll control reported to be very stiff during a ground run. Inspection revealed pulleys aft of the aileron FWD quadrant, and both aileron and spoiler pulleys above fuselage, needed replacement due to excessive corrosion.
- SDR 20230530004 - Aileron and spoiler pulleys in center wing were found corroded during maintenance.
Similar incidents were investigated in 2021 on multiple DHC-8-400 series aeroplanes where stiff roll control movement was reported, typically after returning to service following storage. Inspections of the aileron and spoiler systems in the center wing area had found seized aileron and spoiler pulleys, P/N MS20220-3. This pulley is a military standard part used in many locations in the aeroplane. Since the conclusion of the 2021 assessments there were 12 more reported pulley seizure/failure cases (including the 3 cases above) across the fleet of DHC-8-100/200/300 and DHC-8-400.
Figure 1 depicts the installation:
Figure 1 – pulley installation
Recommended action:
De Havilland Canada has released Service Bulletins (SB) for DHC-8 100/200/300 Series and DHC-8 400 series aeroplanes to replace quantity eight (8) of P/N MS20220-3 pulleys installed in the center wing area with equivalent D1310001-03 pulleys which use CRES (stainless steel) bearings. These are one-way interchangeable standard parts requiring no other modifications to the aeroplane. SB references are as follows:
- Dash 8 Series 100/200/300:
- SB 8-27-126 Rev NC - Flight Controls – Wing – Aileron and Spoiler Pulleys with Enhanced Corrosion Resistance – Retrofit – ModSum 8Q110350
- Dash 8 Series 400:
- SB 84-27-76 Rev NC - Flight Controls – Wing – Aileron and Spoiler Pulley with Enhanced Corrosion Resistance – Retrofit – ModSum 4-114089
It is highly recommended that operators incorporate SB 84-27-76 for the DHC-8-400 series aeroplanes or 8-27-126 for the DHC-8-100/200/300 series aeroplanes as required across their affected fleet and for aircraft model maintainers to exercise maximum caution while servicing the affected model DASH 8 flight control system.
Contact office:
For more information concerning this issue, contact a Transport Canada Centre; or contact Philip Lynch, Continuing Airworthiness in Ottawa, by telephone at 1-888-663-3639 or by e-mail at TC.CAWWEBFEEDBACK-retroactionWebMDLN.TC@tc.gc.ca.
Original signed by
Jenny Young
Chief, Continuing Airworthiness
National Aircraft Certification
The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.