US firm CW Aerotech Services is working to certificate a new landing gear that uses silicon fluid instead of hydraulic fluid. The benefits include fewer leaks, safer handling, reduced viscosity variation and low contamination risk.
The firm is seeking supplemental type certification for the nitrogen-hybrid landing gear on the Eurocopter AS365N and AS366G Dauphin helicopters, although this is still 18-20 months off. It has already gained US Federal Aviation Administration Form 8110 clearance for the types, meaning approved repair centres can perform the work if the operator then applies for FAA field approval.
CW Aerotech executive vice-president Bob Wehr says the modification has already undergone military airworthiness qualifications and has flown the first part of an operational evaluation for the US Coast Guard, ahead of a wider-ranging trial on their Eurocopter HH-65 Dolphins. Wehr values this potential 98-aircraft contract at around $18 million.
The landing gear, which is manufactured by Houston-based Texas Air Services, uses nitrogen in the upper chamber and silicon fluid in the cartridge interior. The idea of using silicon fluid in landing gears dates to the Second World War. In these original "liquid spring" tests, the fluid was used for both the spring and dampening functions of the gear.
While silicon fluid is a good dampener, it is ineffective as a spring. In the hybrid version this is achieved by the nitrogen.
In the case of the coastguard gears, 50-60 parts can be removed and replaced by just 15. "One of the benefits of this is the simplicity of the installation," says Wehr. "You take it out and slide the new cartridge inside."
Another project for which CW Aerotech is looking at performing a feasibility study and adaptive tests is a US Army contract, which could cover more than 2,000 Sikorsky UH60 Black Hawks. The work will begin this summer. CW Aerotech is also eyeing a deal with the police for around 20 HH-65s.
Wehr is confident that the technology could be applied to civil aircraft and other aircraft parts that rely on hydraulics for absorption. He says a small Canadian manufacturer has invited CW Aerotech to participate in the gear for a new-design 5,000kg (11,000lb) fixed-wing aircraft, which he believes will be intended as a freighter. "This is our first opportunity to design from ground zero," he says.
Source: Flight International
