Civil Aviation Safety Alert (CASA) No. 2011-04

ATTENTION:
OWNERS AND MAINTAINERS OF ZENAIR CH2000 SERIES AEROPLANES

Issuing Office: National Aircraft
Certification Branch
Document No.: CASA 2011-04
File Classification No.: Z 5000-35 Issue No.: 01
RDIMS No.: 4965407 Effective Date: 2011-09-02

ZENAIR CH2000 NOSE LANDING GEAR WELD CRACKING

PURPOSE:

This CASA is issued to inform owners and maintainers of the CH2000 series aeroplanes of a potential unsafe condition regarding the cracking of the Nose Landing Gear (NLG) weld.

BACKGROUND:

The Federal Aviation Administration (FAA) informed Transport Canada Civil Aviation (TCCA) of a NLG weld failure and crack findings of another NLG weld of a CH2000 aeroplane.

The incident report states that the first landing by a flight instructor and student was smooth and uneventful.  While the second landing was also smooth, when the nose touched down, the instructor noticed the nose gear fork exit on the left side of the aeroplane and shot past the nose of the aeroplane. The remaining nose gear leg contacted the runway surface and supported the nose but the reduced clearance allowed the propeller blades to contact the runway.

Inspection of the aeroplane showed that the plate welded onto the bottom of the nose gear leg (Photo 1) failed, causing the nose gear fork to separate from the nose gear leg.

Photo 1: Nose Landing Gear Assembly

Photo 1: Nose Landing Gear Assembly
Additionally, the operator found cracks developing in the weld of another CH2000 aeroplane’s NLG (Photo 2).
 

Photo 2: Cracking on the NLG leg and plate weld

Photo 2: Cracking on the NLG leg and plate weld
A review of Service Difficulty Reports did not find additional occurrences. An investigation by Zenair did not reveal a root cause. It is believed that the weld cracking is due to “excessive hard NLG landing, exceeding the design limits. The nose wheel fork may flex and bend the square steel plate welded to the structure resulting in possible metal fatigue and eventual cracking.”

TCCA Comments:

The Design approval holder, Zenair Ltd., has investigated the issue and has published a Service Bulletin in February 2011 that details preventative measures and initiates a visible and/or fluorescent liquid penetrant inspection of the nose land gear weld.  These measures are also incorporated in the Zenair Ltd. Service Manual.

RECOMMENDED ACTION:

TCCA strongly recommends all affected owners and operators pay close attention to the NLG weld area both during scheduled maintenance activities and following every hard landing per Zenair Ltd. Service Manual instructions.

Defects, malfunctions and failures occurring on aeronautical products are to be reported to Transport Canada, Continuing Airworthiness in accordance with CAR 521 mandatory Service Difficulty Reporting requirements.

CONTACT OFFICE:

For related service information, contact :

Zenair Ltd.
Huronia Airport
Midland, ON  L4R 4K8
CANADA
Tel: 705 526-2871
Fax: 705 526-8022

For further information, contact a Transport Canada Centre, or Ms. Yosha Mendis, Continuing Airworthiness, Ottawa at 613-952-4357, facsimile 613-996-9178, or email CAWWEBFeedback@tc.gc.ca

Note: 
For the electronic version of this document, please consult the following Web address:
www.tc.gc.ca/CivilAviation/certification/menu.htm

For the Director, National Aircraft Certification

ORIGINAL SIGNED BY

Philip Tang
Acting Chief, Continuing Airworthiness

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.

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