The asymmetric horizontal stabiliser design in the Robinson R22, R44 and R66 models significantly contributed to the uncommanded right roll rate during low‑G conditions and the risk of an in‑flight break‑up.
Response by Robinson Helicopter Company
Robinson Helicopter Company (RHC) has developed a symmetrical horizontal stabiliser with the intention of reducing the uncommanded roll rate if a low-G condition is encountered, allowing pilots more time to recognise and respond to the low-G condition. The symmetrical stabiliser is being fitted to new Robinson models, and is available as a modification to all in-service aircraft. Further, as the original R44 and R66 stabilisers reach their overhaul life limit, they are being replaced with the modified items.
ATSB comment
The ATSB welcomes the development of an improved horizontal stabiliser that reduces the risk associated with encountering a low-G condition. The action taken by RHC, intended to maximise the fitment of the modified stabiliser, addresses the safety issue.
The ATSB strongly encourages all operators of Robinson helicopters to fit the symmetrical horizontal stabiliser.
