Project: Helicopter Stringing Equipment Delivery & Commissioning
Location: Yass, NSW
Sector: Transmission Infrastructure
Client: Genus / Acciona
Services Provided: Equipment Supply, On-Site Commissioning, Operator Training
Equipment Used: OMAC T30.H Helicopter Tensioner, OMAC F155.H.070 High Speed Helicopter Stand
Project Overview
Helicopter stringing is the method of running new conductor using a helicopter rather than ground-based pulling equipment, typically used where terrain, access or program constraints rule out conventional stringing. On the Humelink East Transmission Project in Yass, NSW, Legend Hire supplied and commissioned the OMAC T30.H Helicopter Tensioner and F155.H.070 High Speed Helicopter Stand for Genus/Acciona, supporting safe, controlled conductor payout during live aerial stringing operations.
The Challenge
Standard ground-stringing tensioners operate with a negative response: if the machine fails, the brake locks and tension is held. On the ground, this fail mode is manageable. Beneath a helicopter in live stringing operations, a locked brake turns the wire into a fixed, tension-loaded anchor point, a critical hazard to the aircraft and pilot. Genus/Acciona required equipment purpose-built for aerial operations, with a failure mode engineered specifically around helicopter safety, not adapted from ground-based machinery.
The Engineered Solution
Legend Hire supplied the OMAC T30.H Helicopter Tensioner and F155.H.070 High Speed Helicopter Stand, equipment designed from the ground up for aerial stringing rather than adapted from ground-stringing systems. The T30.H’s core design principle is the inverse of conventional tensioners: there is no negative. If the machine fails for any reason, it continues to pay out. It will not lock up.
This principle underpins every safety feature of the system:
- Open-brake fail-safe design: the braking system defaults to open, not locked, in a failure scenario, ensuring the helicopter can continue flying without the wire becoming a fixed load.
- Controlled payout at 20–25 km/h: matched to helicopter operational speeds during stringing, maintaining consistent tension without shock-loading the aircraft or conductor.
- Aircraft-first fault response: in any fault condition, the system is engineered to protect the helicopter and pilot above all else.
This reflects a broader shift toward purpose-built helicopter stringing equipment, moving away from adapted ground-stringing machines whose failure modes were never designed with aerial operations in mind. Legend Hire supplies and commissions OMAC stringing and winching equipment, including hydraulic tensioner systems and helicopter-rated stringing systems, for transmission and utility projects across Australia.
Equipment Used
T30.H OMAC Helicopter Tensioner
Purpose-built for helicopter stringing operations. Delivers controlled conductor payout at 20–25 km/h with a fail-safe open-brake system. No negative – in machine failure, the conductor continues to pay out freely, eliminating the risk of sudden tension lock-up that could compromise the helicopter.
F155.H.070 High Speed Helicopter Stand
Works in conjunction with the T30.H, providing the correct drum handling and feed geometry for high-speed aerial stringing. Engineered for the operational demands of large transmission projects.
Engineering Considerations
The defining engineering decision on this project was prioritising aircraft safety in the failure mode itself, rather than relying on operational controls alone. An open-brake, no-negative design removes the failure scenario that matters most in aerial stringing – sudden tension lock-up – at the equipment level, before it ever becomes a procedural risk. Payout speed was matched to helicopter operating speed (20–25 km/h) to prevent shock loading of either the aircraft or the conductor under normal and fault conditions.
On-Site Commissioning & Training
Legend Hire’s delivery was supported by Filippo, OMAC’s Technical Director, who joined the team on site to commission the equipment and deliver operator training to the Genus/Acciona crew. Training covered:
- Risk assessments: hazards specific to helicopter stringing and the mitigations built into the OMAC system
- Operator use: hands-on familiarisation with controls, monitoring and operational procedures for both the tensioner and helicopter stand
- Anchoring: correct setup and verification of machine anchoring under tension loads
- Key safety features: the open-brake fail-safe design, payout speed control, and emergency response procedures
The training was structured around system intent, not just operation, so that in a high-pressure scenario, operators understand why the equipment behaves the way it does and can respond accordingly.
The Outcome
The OMAC T30.H and F155.H.070 were commissioned and operational ahead of live stringing works on Humelink East, with the Genus/Acciona team fully trained on fail-safe operation, anchoring verification and emergency response procedures. The equipment’s open-brake, no-negative design ensured helicopter safety was engineered into the system itself, rather than relying solely on operational controls, supporting safe aerial stringing on one of NSW’s major transmission infrastructure projects.
Frequently Asked Questions
A helicopter tensioner like the OMAC T30.H uses a fail-safe open-brake design – if it fails, it pays out conductor rather than locking under tension, which would otherwise create a dangerous fixed anchor point beneath the aircraft.
Because a locked brake on failure would hold the conductor under tension, putting the helicopter and pilot at risk. The open-brake design ensures the aircraft can continue flying safely in any fault condition.
The T30.H is designed for controlled payout at 20–25 km/h, matched to typical helicopter stringing speeds to avoid shock-loading the aircraft or conductor.
Helicopter stringing is used where terrain, access constraints or project program make ground-based pulling impractical, common on large transmission projects such as Humelink East.