The product manufacturers, supported by EASA, have on several occasions attempted to make clear that only parts that are manufactured under control of the Type Certificate Holder (TCH) or Supplementary Type Certificate Holders (STC) control are eligible for installation on their respective helicopters. Where a part does not meet these criteria, then it should be replaced with a part conforming with the TCH or STC holders requirements. 

This policy is supported by Information Letters issued by the Type Certificate holders for both aircraft types, clarifying their individual positions concerning the eligibility requirements for replacement parts.

• Agusta Westland Information Letter (15 November 2006) 
• Bell Helicopters Information Letter No. GEN-99-65 (15 January 1999, revised 2 June 2006)

Parts manufactured by or for Bell under their production approvals are not normally eligible for installation on Agusta/Bell manufactured helicopters. Parts produced by or for Agusta are not eligible for installation on a Bell manufactured helicopter.

Original Bell Helicopters parts may only be installed on the Agusta Bell 206 when the part is supplied and authorised by Agusta, now Leonardo S.p.A. Authorisation may be provided by Leonardo S.p.A through their EASA design organisation approval.

The Augusta Bell 206 and the Bell 206 helicopters are separately type certificated and have different instructions for continuing airworthiness (Life limits, maintenance manuals, repair data etc) that are approved by their respective States of Design i.e. EASA and Transport Canada. Consequently, there are several differences between the ICA's (Instructions for Continuing Airworthiness). Great care must be taken to ensure that the correct airworthiness directives, maintenance data and other instructions which form part of the ICAs' for the type are available and used.

In summary, there has been no change to the status of the information letters published by the type certificate holders for some years. There are no changes being considered that may alter the position that the letters describe.

The helicopters must comply with their applicable Type Certificate, be constructed from correctly configured conforming parts and be maintained using the correct instructions for continuing airworthiness. Failure to ensure that the helicopter is correctly configured and maintained will result in an unairworthy aircraft and invalidate its certificate of airworthiness. 

The Bell 206 was certified by the TCCA and subsequently an EASA Type Certificate was issued Ref. EASA.IM.R.512.  Prior to the issue of this Type Certificate the type had been certified by the individual European authorities.

The Agusta Bell 206 (Leonardo S.p.A) was certified by ENAC on 8 August 1967 and subsequently an EASA Type Certificate was issued Ref.  EASA.R.140.