Shell Introduces its Unleaded 100 Octane Fuel Featured

Written by Steve Ells
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February 2014-

Shell Oil issued the following press release on Dec. 1, 2013:


Shell today became the first major oil company to develop a lead-free replacement for Aviation Gasoline (Avgas 100 and 100LL), which will now begin a strict regulatory approvals process. Avgas is one of the last common transportation fuels to contain lead and is used by light aircraft and helicopters. Shell's new lead-free formulation comes after 10 years of exhaustive R&D, as well as successful initial testing, carried out in the last two months by two original equipment manufacturers (OEMs).

Xinsheng (Sheng) Zhang, vice president of Shell Aviation, said, "We are proud of this first for Shell Aviation. This advanced product is the latest milestone in our long history of innovation. We believe that with industry support, a stringent approvals process can be completed for this new lead-free product within a short timeframe. We look forward to working alongside our technical partners and authorities to progress the necessary approvals needed to make this product a reality for use in light aircraft engines of all types."

I interviewed Dr. Tim Shea, Ph.D., Aviation Gasoline Development Manager for Shell Projects and Technology (U.S.) on Dec. 20, 2013. Here is a transcript of our conversation.

SE: What is your degree?
TS: My degree is in chemistry.

SE: How long have you been with Shell?

TS: I was originally with Pennzoil-Quaker State, and we merged with Shell back in 2003—so it's been about 10 years now.

SE: Are you a pilot?

TS: I'm not, although I've always [been] a bit of an aviation buff; it's something I might get into. Of course, right now I've got my hands full with this Avgas... It might be in the cards.

SE: Well, if you have an interest and can afford it, there's really nothing else like it.

TS: Yeah, my boss has even told me that they would give me the time off to go do it and everything. It's just a matter of when.

SE: Do you have small kids at home?
TS: Yeah, I've got an eight-year-old and a six-year-old.

SE: Well, you've got your hands full. During the time I worked as a tech rep for an owners association, it wasn't unusual to get calls from men that wanted pointers on how to get started [on attaining their private pilot certificate] because it was now their time... the kids were out of college, and the dog died.

TS: (Laughs.) Yeah, that might be me!

SE: As I understand it, Shell has not been in the Avgas business here in the United States for some time.

TS: We've been in the Avgas business; we're actually one of the top producers of Avgas. In the U.S. we're not so well known because we don't actually manufacture in the U.S. currently. We distribute through Eastern Aviation, so our footprint in the U.S. is relatively small.

Our primary manufacturing is based overseas. We have a refinery in Australia and [another refinery in] South Africa.

SE: So you're familiar with the 100LL game?

TS: Oh yeah.

SE: The industry—and that includes the regulators—has finally concluded that none of the unleaded 100 octane replacement fuels will ever completely comply with ASTM standard D910, the standard that exists for 100LL Avgas. So that search is over, and the industry is starting from scratch.

The FAA now has funding to implement a program that they have labeled the Piston Aviation Fuel Initiative (PAFI) and has set up an FAA Fuels Program Office.

Under Phase One of the two-phase program, the FAA has opened a window to accept for testing up to 10 of the most promising unleaded 100 octane Avgas formulations. The window closes in July 2014.

SE: Will Shell be submitting its fuel to PAFI?

TS: Well, it's not confirmed that we will. Our problem right now with PAFI—and there's a lot of engagement going on with FAA around this—is the timeline.

They're not flexible enough about speeding things forward. We believe we can complete our program sooner than PAFI would. PAFI is really generating the data set to get an ASTM specification, which leverages the fuels toward certification. Waiting until the end of 2018 and beyond just to get your data set seems rather long.

SE: The Shell press release indicated that Shell thought they could make this happen pretty quickly.

TS: Yeah, we have a very aggressive timeline that we're working under, and we fully understand that it's very aggressive, but that would call for being able to commercialize the fuel within a two-year timeframe.

Now, there's a lot of assumptions that go into that, and that are likely to flip, but we tend to aim high.

SE: Someone told me that one reason the FAA has established the lengthy timeline is simply job security.

TS: We have gone and met with the FAA leaders at PAFI and the problem that we're really struggling with—and PAFI still hasn't addressed this—is how do you get from there [PAFI's approval of data for an ASTM specification] to fleet-wide certification.

That's not been worked out, and that's what our major focus with the FAA on that front is. How do you connect the dots?

SE: Are you saying that even if a fuel or fuels are approved, how do we legally get them into the fleet?

TS: Let's say that there's funding to do airframe and engine testing for two fuels, and let's say that both fuels are successful, so then you have two fuels that have gone through their rigorous tests and that they're happy with, and they're comfortable with those fuels and would support certification. You have to take that data and go into ASTM for a production spec. Assuming that data set is robust, you should be able to do that without too much problem.

And then the question is once you've got that certification specification, you go back to the FAA Fuel Programs Office... and how do you turn that into a fleet-wide certification? That's not clear yet.

SE: I talk to a lot of people in the industry and although I haven't been to an ASTM meeting, it appears that these are issues that still aren't clear to the insiders in the industry.

TS: That's exactly right. In fact, we just feel like we're beating our heads against the wall, to be honest.

Part of the issue the FAA has is this PAFI thing has gone down a competitive contracting route. Now they're kind of beholden to the contracts people. So whenever I ask the FAA official at the Fuel Programs Office or ask the head of FAA Fuels testing over at Atlantic City questions, they struggle to answer, because they don't know what they can and can't do within the framework of the contracting process. That makes things even more difficult to get clear answers around.

SE: So everybody is beholden in some way to somebody?

TS: Exactly. When FAA got up to give a presentation at ASTM on Monday afternoon and the the contracts person [was] there, most of the questions [were] funneled to them.

SE: I know that Shell makes a high octane unleaded racing fuel for race cars. Is this anything like that?

TS: My background was retail fuels; I used to do road fuels for the U.S. motorsports group that developed that portfolio for the same purpose. And we have currently three different types of [Avgas] fuels that we think are viable, and one of the fuels is based very much on that racing fuel.

SE: So Shell has three fuels that you think will do the trick?

TS: Yeah, and they're very distinct from each other; see, the idea was that we anticipate that as we go through the testing process and drive toward certification, there's likely to be some obstacles that can't be overcome. So rather than focus on one from the beginning, we kind of hedged our bets.

Right now, we're trying to get down to the best one. We think we can get that in the next month or so. (This interview was conducted on Dec. 20, 2013. —Ed.)

SE: Has Shell done any real-world testing in engines or in flying airplanes?

TS: Lycoming's been helping us out with our three chemistries. They haven't completed the matrix yet but they've completed two, and they've had some downtime for some other reasons, but they're running a 540-J2B—and effectively just running the standard mixture sweeps and detonation test protocols and trying to compare it to 100LL.

It's a 101 MON [Motor Octane Number] LL reference fuel they're using. They're trying to see if there's anywhere that the [Shell] fuels fall short in terms of the 100LL comparison over the entire envelope of the engine. And so far there have been no issues.

The data sets aren't complete but [for] the fuels [test results] that we have got back, we are equivalent and in the areas we're not equivalent, we tend to be slightly better than the current product.

The Lycoming detonation testing is then being funneled into Piper Aircraft so that they will be flying the fuel once they get the O.K. from Lycoming that the detonation is fine. So they've flown the first fuel that was tested prior to the [press release].

SE: Are you saying that Piper flew it at its factory?

TS: Yes, at the factory.

SE: In what engine?

TS: It was a Saratoga, but I don't recall the exact engine. It was not a very demanding engine.

The problem we had was since we don't have STCs they had to fly under experimental, and the plane they really wanted to fly was the Mirage, but their experimentally certificated aircraft doesn't have the Lycoming engine in it right now. The goal is to go back and redo the test once the Lycoming engine is in it.

Right now the flights are more of a demo test because the Lycoming test was lagging and we needed to get a public announcement prior to ASTM because we were going in to ASTM asking for permission to put together a test specification and a research report.

That way, everybody would be aware why we're doing it because that was the timing driver there—so we scaled back that flight to accommodate that timeline.

The plans are not limited to Lycoming and Piper; we have more of an OEM alliance here, so we're also working out our testing plans with folks like Continental, Cirrus and Robinson Helicopter, so it will be fairly diverse group of folks we're getting data from.

SE: I've had some dealings with Robinson Helicopter and I really like the way they do business.

TS: Yeah, I've talked to Kurt [Robinson, president at Robinson Helicopter] off and on for months trying to sort it out and... they're ready to go, but we're still trying to down select our favorite fuel. So between now and the next couple of months—say, the February timeframe—we should have that selection completed. Then we will be in the position to get them the fuel and get it tested.

SE: So are you saying that by February you will have the most favorable of your three chemistries selected?

TS: Yeah, that's what we expect—but the overall strategy hasn't been worked out yet for ASTM, so we're debating how to best approach that.

In terms of specifications, there's not enough potential to put all three fuels into one specification because they're that different. Two of them could be, but then the specification would get rather wide, so we're debating whether we just go ahead with one and see how it goes, or we do two or potentially three of them.

SE: Tell me about the energy content and the weight.

TS: The fuel, in terms of D910... we meet all the properties except for two. (D910 is the spec for 100LL and lists 44 properties that must be met to comply with the spec. —Ed.) Well, two of the fuels meet everything but two; one of them meets everything but three.

The areas where we fall out are final boiling point—we're within about 10 degrees; we're at 180 [and] the spec is 170 [degrees F], and heat of combustion—there, we're within 2 or 3 percent of the D910 number, so we're not very far off; however, the density of our fuel is higher. The heat of combustion number is mass based, so if you use a volume-based measurement, our fuel is actually more energy dense per gallon.

So the calculations we've done so far indicate aircraft range is probably equivalent, but when we get farther into flight testing we're going to prove that out. The final one has a fairly high electrical conductivity value, however it's still significantly lower than the values where history suggests there would be any problems with that sort of thing.

So we don't anticipate any problems, but in terms of D910 values, it's a little high.

SE: How about weight?

TS: The mass of the fuel is a bit higher. Each fuel has its own density. We will certainly be heavier than 100LL. I have a feeling every unleaded 100 octane fuel will be heavier than 100LL, because lead allows you to keep the fuel very light.

So probably if you think of 100LL of being in the .7 or .72 range, we're probably in the .75 or .78 area. For comparison, Swift would be the extreme example: they're at .80.

SE: Someone told me that the Swift presentation at ASTM was revealing.

TS: Yeah, they have a significant series of hurdles to climb around materials compatibility, mainly because of the composition of the fuel. They've got a lot of proving to do.

For example, the aromatics. They disclosed all this publicly at ASTM, so it's no secret; the patents say the same thing. Their aromatics are up in the 70 to 80 percent range, and those are particularly aggressive toward the natural rubbers, so things like fueling hoses which are usually rated for about 40 to 45 percent aromatics, you're basically doubling that—and you're going to run into problems.

SE: Everyone is looking for a drop-in replacement fuel.

TS: That's what our goal is, that nothing should need to be changed. No parts should need to be changed; that's what we're shooting for.

SE: So you're not seeing any need to change anything on the airplane, or the need for the pilot to adopt any new procedures as far as how he flies the airplane? I expect there may be a little change in weight and balance calculations due to the weight of the fuel, but nothing else?

TS: Yeah, so far, that's the only thing that's been tossed around when we talked to Piper—and they know that there are differences, but they were saying that the feedback already is that they're unconcerned about it. There's potentially some calculations that need to be made but so far, we aren't getting any feedback that sounds anywhere near a concern-type level.

Again, we've got a lot more flying to do, so we'll see how that evolves. One of the big keys since our density is higher is what is the effect of that, and what is the feedback from the OEMs? We do plan on getting a sort of a position statement from the various OEMs that collate all that information in one place and put that as part of our package to present to ASTM with our application.

SE: It sounds like you have reached out to a lot of OEMs and manufacturers. Am I correct in assuming that everyone has been happy to play along?

TS: I don't think anyone has told us no so far. The negotiations are always around what level of commitment they can afford and are willing to entertain; we always have to negotiate that bit, but no one has come out and said they're not interested.

SE: What was your opinion of the [latest] ASTM meeting? Was it productive?

TS: I think it was extremely productive, particularly because of getting ourselves kicked into the ASTM process, it was a good chance to get our current network of OEM folks together and to get a pre-working group meeting—to get everybody there and at least initiate that process. Because, like I said, we have a very aggressive timeline and it really calls to get through this test specification very quickly, and essentially have it approved by the next meeting in June [2014], then we can focus on the production spec—which is really the final hurdle where a lot of the difficult questions are going to come up.

So it's going to be critical to have those folks and the input that they can provide and the feedback and any negative votes so we can turn them into positive territory. I'm a fuels guy so a lot of these questions come down to airframe and engine type questions, and we're not the best place to convince people, so we've recognized early on that we really need the OEMs' support.

SE: Let's go over the path one more time.

TS: You get a production spec approved. Once you have that, then you can go to the FAA and get STC approvals or product certification or whatever. You can't do anything until you get that production spec, so you talk to Kraft [Michael Kraft, Lycoming's senior vice president and general manager] and he says we're going to run your fuel in a 540 K or something like that, but you can't take that data to the FAA until you have a production spec—you can't formally certify it.

SE: It sounds like the path to getting to the fuel is pretty well understood. But the path to getting the "new" 100 octane unleaded fuel approved for use in the fleet—especially for airplanes that are orphaned and so don't have a strong OEM presence—is still foggy. Even strong OEMs may not be willing to accept the responsibility that goes with approving the use of unleaded fuels in airplanes that they produced 50 years ago.

TS: Yes, that's going to have to be an FAA responsibility, to deal with that. And part of their PAFI program versus the ASTM path; PAFI is primarily focused on the legacy fleet because anybody can go out to the OEMs right now and get data on production airplanes. That's one of the things they've said and we'll see if this happens.

I think EASA just did this in Europe. [They said] that if your [engine] octane [requirement] is low enough to run UL 91, you're good to use this fuel. FAA has said they're planning on doing the same thing in the U.S. as sort of dry run for the high octane unleaded fuel.

(Editor's note: Shea is referring to a surprising move in May 2012 when the European Aviation Safety Authority (EASA) issued Safety Information Bulletin (SIB) 2011-01R2, which cited that Avgas 91 UL may be used if approved for the particular engine type. The surprising part was that EASA said no additional approval was required for the airplane provided that the airplane was already approved for operation with Avgas or mogas and the engine was already approved to use Avgas 91 UL. Both Lycoming and Continental have been issuing service information and updating Type Certificate Data Sheets approving the use of Avgas 91UL in recent years.)

SE: Really!

TS: Which would be a step in the right direction, because they would obviously be assuming the liability to do that. Our struggle is the FAA is saying they're going to be flexible, open-minded, the whole thing... but we're struggling right now to see tangible evidence of that, so that's what we're trying to get a little more comfortable around.

The head of the FAA Fuels Program Office has said he understands our issues with the timeline and he said he's open to reopening that door, so [what] I'm trying to do right now is pull in all the details of our testing and work out the timeline of what we're comfortable with and give it to him and see if he's free to negotiate some of those timeline issues.

He's said he's open to it, so we'll see.

The FAA doesn't have a strong driver to move this forward. The EPA has been sued. The FAA's responsibility is to insure a safe replacement, so if they wanted to drag their heels they could easily curl themselves up in the blanket of saying 'we don't feel it's safe yet.' It's going to be a multi-year process and there will be plenty of milestones along the way.

SE: I guess they could do that by [continuing to ask] for more data?

TS: Yeah, then we would keep going around in circles, and they could easily do that. And we want to make sure we have a line of sight on how we get to the goal.

Steve Ells has been an A&P/IA for 39 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He's a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation ( and lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to .