CSS Posted to Address Abrasion Strip Cracking

The Issue

A few operators of VHA 206L main rotor blades (P/N 20633000-101) have found cracks in the leading edge abrasion strips (either inboard or at the tip) within the first 1,000 hours of flight.

We believe this issue applies mainly to the 206L main rotor blades, likely confined to serial numbers A043, A044, A078, A079, A083, and A084. There has also been one report of similar cracking on a 206B main rotor blade abrasion strip, but that seems to have been an isolated issue.

The 206B/L main rotor blades contain three overlapping abrasion strips covering the entire length of the leading edge. The inboard and middle abrasion strips are made from roll-formed stainless steel; the outboard tip abrasion strip is electroformed in-house at VHA.

These abrasion strips are non-structural components of the main rotor blade assembly and serve to protect the underlying composite material from impact and erosion damage. The abrasion strips are designed to remain installed and in service even after sustaining damage due to erosion, impact, or cracking as long as no underlying void or debond has occurred (in the case of an impact).

During certification testing, an inboard section of the main rotor blade with a bonded inboard abrasion strip was tested to the equivalent of the full life of the blade. The test showed that even when cracks appeared in the abrasion strip, the underlying composite structure was not compromised.

Repair Requirements

Cracks in any abrasion strip require a tap inspection upon discovery. If no voids or debonds are found on either side of the crack, cover the cracks with polyurethane tape. See the Instructions for Continued Airworthiness (ICA) document VMM-MR-206L-501_RevB and Customer Support Specification (CSS) CSS-501.

If any voids or debonds are found, this likely indicates impact damage. Contact Van Horn Aviation immediately for repair guidance.

VHA Solutions

Van Horn Aviation has taken the following steps to resolve this issue:

  1. We revised the appropriate ICA with inspection and repair procedures and posted the new ICA on our Documents page.
  2. We created a new Customer Service Specification (CSS-501) to provide procedures for the 3M Polyurethane Tape Installation.
  3. We are contacting operators with the products and serial numbers that may be affected by this issue. Those operators who have turned in warranty cards for the serial numbers identified have been or will be contacted by VHA regarding the issue and the appropriate documents.
  4. We are also letting operators know through our newsletter and social media channels.
  5. We have received FAA approval to replace the stainless steel abrasion strips with Inconel (a nickel-chromium alloy). New main rotor blades manufactured after June 2021 will contain the Inconel abrasion strips.