51-002 - Robinson R44 Hydraulic Hoses – Clearances from Adjacent Structure

ATA Chapter: 51

Subject:

This Continuing Airworthiness Notice (CAN) is issued to draw operators and maintainers' attention to the potential for contact between the fuel tank supporting structure and the braided hydraulic line.

Applicability:

All Robinson R44 Helicopters.

Purpose:

This Continuing Airworthiness Notice (CAN) is issued to draw operator’s and maintainers attention to the potential for contact between the fuel tank supporting structure and the braided hydraulic line.

Background:

This CAN is prompted by a recent incident where an R44 engineer found evidence of chaffing between the aircraft fuel tank support structure and the stainless-steel braiding of the hydraulic pump suction hose. Refer to Figure 1 in this CAN for bladder fuel tank chaffing damage.

It appears that the hydraulic pump fittings, to which the hydraulic hoses attach, were incorrectly orientated on installation. This resulted in insufficient clearance between the hydraulic suction hose and the fuel tank.

The chaffing could have resulted in rupture of the bladder fuel tank if the insufficient clearance between the hydraulic suction hose and the fuel tank had remained undetected.

Recommendation:

Maintenance engineers are reminded of the following:

• The importance of correctly orientating the hydraulic fittings on the hydraulic pump. Refer to figure 2 in this CAN for hydraulic pump fitting orientation.
• The clearance requirements between the fuel tank structure and the adjacent hydraulic lines as detailed in the R44 maintenance manual.
• Ensure that appropriate clearances are maintained when installing fuel tanks. Refer to figure 3 for a pictorial of the R44 hydraulic flight control system.

Note:
If any hydraulic hose and fuel tank chafing damage is found, complete a CA005 Defect Report form and submit the completed form to the CAA at CA005@caa.govt.nz or report findings via the online reporting system.(external link)

Please include all findings and any other relevant technical information. A CA005D Defect Report form can be obtained from https://www.aviation.govt.nz/about-us/forms/Filter/?SearchTerm=&Rule=8

Figure 1. Damaged fuel tank structure

Fig 2. Example of correct orientation of the fittings and hoses

Figure 3: R44 8-1A Hydraulic flight control system