When Boeing asked Avtron Aerospace Inc. to design a test stand for its 787 Dreamliner, there was one major hurdle to overcome: the type of hydraulic hose needed to plumb the test stand did not exist. No manufacturer offered a hose compatible to the application that could withstand the increased hydraulic pressures. To meet its needs, Boeing searched for a manufacturer willing to design and deliver a new type of hose within the constraints of its extremely demanding production schedule.
The Dreamliner test stands, built by Avtron, are designed to test the hydraulic function of the Dreamliner on the assembly line, and some of the test stands are mobile for testing on the runway or tarmac.
Because the Dreamliner features higher hydraulic pressures than most commercial aircraft, Boeing requested a 6000-psi hose. This would allow for testing of the aircraft functions while accounting for pressure drop in the test system and a safety factor.
The problem was that this 6000-psi hose also had to be compatible with Skydrol fluid, a phosphate-ester fluid. For a hose to withstand Skydrol fluid, it must be made primarily of EPDM rubber.
At the time, no manufacturer offered an EPDM hose rated up to 6000 psi. One of Parker Hannifin’s hose options was a high-pressure thermoplastic hose. This hose did not meet the necessary bend radius requirements and was rated for pressure much higher than needed in this application. The other existing option was a Parker rubber hydraulic high-pressure hose that is not rated for phosphate-ester. As a result, this hose would deteriorate quickly because of the fluid incompatibility. The cost of regular replacement made this option cost-prohibitive.
All other existing options were ruled out by Boeing’s design specifications. For example, the mobile test stands required hose to be on reels for manual attachment to the plane. Avtron could have used a very-high-pressure hose (10,000 psi), but its limited bending capability (bend radius) would be too stiff. To put this kind of hose on a reel, the reel would have been bigger than the test stand itself. Avtron also looked at welded pipe but determined it was much too time-consuming, heavy, and bulky to work with.
To develop a hose up to the challenge, Boeing, through Avtron, turned to Parker Hannifin. Parker successfully created a new hose specifically for this application, called the F42 hose. The development included creating an EPDM-based solution rated to the necessary pressure requirements. Parker’s F42 hose uses No-Skive fittings, giving users the advantage of not having to remove the cover or inner tube to attach the crimped fitting directly to the hose reinforcement, which saves setup time.
Parker had the F42 hose designed, tested, and in production in less than four months to meet Boeing’s tight timeline.
The F42 hose passed Boeing/Avtron’s rigorous testing and could be produced for much less per foot than the only other viable option on the market (which would have required regular replacement). Parker saved Boeing approximately $5700 for each test stand.
The F42 hose is a product key to the aviation industry because of its capacity to handle Skydrol fluid at increased pressures. The hose features a tighter bend radius and smaller outside diameter compared to other potential solutions. Additionally, less weight per ft (F42 hose weighs 1.4 lb per ft for size -16) reduces wear on both the test stand and the operator as he manually unreels the hose and attaches it to the plane. And the F42’s no-skive design means the user does not have to skive (take off a portion of the cover or inner tube) to attach a fitting to the hose, which can be a dirty and time-consuming job, meaning crimping the hose can be done quickly and easily, saving setup time.
In addition to Dreamliner test stands, F42 hose will be used on all ground-support equipment for the new plane. Because of the higher pressures on the 787, it will require its own ground-support equipment capable of testing the higher-pressure system.
“The F42 is a great solution and takes a lot of the weight off of our shoulders in terms of needing to design and build systems in the future that can withstand the increasing pressure ranges of the aircraft industry,” said Brian Cooper, hydraulic manufacturing engineer for Avtron. “Knowing that this hose is available helps us tremendously.”
Greg Reardon, Business Development Manager, Parker Hannifin, wrote this article for Aerospace Engineering & Manufacturing.