A day after revealing its intention to obtain approval to operate its R44 and R22 piston engine helicopters on unleaded fuel (see article on page 10), Robinson Helicopter (Booth No. C23) shared its strategy for doing so. CEO Kurt Robinson and engineering vice president Pete Riedl spelled out the steps required and the technical issues involved.
Engine maker Lycoming needs to obtain FAA approval to burn unleaded fuels in its engines while Robinson must perform airframe testing with the fuels on board for each of its relevant helicopter models. Riedl said the test plan involved required “hitting a lot of points, with the most significant being establishing compatibility with relevant parts such as fuel bladders and O-rings, because the no-lead fuel has different components in it compared to leaded fuel. I think it will be fine but we need to demonstrate that.”
He said the other main technical issue is that “the fuel we intend to use has a higher vapor pressure.” Riedl said the fuel is identified in Lycoming Service Instruction 1070 and is based on a blend already used in Europe, UL91. “It is a modified autogas and is under the same spec as autogas in the United States, ASTM D4814. It is a pretty broad spec and you need to define the octane rating, and that is AKI93, the vapor pressure, with no methanol or ethanol added.”
Engine modification will not be required and the engines will be able to operate on either the specified no-lead fuels or traditional leaded 100LL.
“I am going to push this,” said Kurt Robinson. “The FAA is well on-board.”
Riedl said Lycoming already has discussed the issue with the FAA and fuel companies.
“In Europe this unleaded fuel is going to be easier to obtain that the leaded fuel,” Robinson said. “What is frustrating to me is that we have been talking about this for years and it should be done by now.”
Riedl said straight automotive unleaded fuel is unsuitable for aircraft piston engines because of the specific vapor pressure and the amount of water and alcohol in automotive fuels. “We have to show that these fuels won’t cause vapor lock,” he said. “These engines were designed to run on really high-octane fuel at high temperatures.” He characterized D4814 fuels as a slight modification of automotive fuel.
Riedl said he would welcome discussions with other aircraft OEMs to promote the initiative and is working with the FAA’s “AIR-20” Fuels Program Office in Washington, DC.
“This is one of those things you look at, and you know we are all going to have to do it,” said Kurt Robinson. “Why does everybody drag their feet? Why not lead the way?”