www.PSFmagazine.com | December 2016-January 2017 | 13 12 | December 2016-January 2017 | Powered Sport Flying LAMA & USUA electricity is not typically measured in gallons. Neither are electrons, for that matter. In 2012, a legal interpretation was requested regarding batteries and fuel by Brian Carpenter. The main thrust of the request was that: “In summary, our current interpretation of both the letter of the law as well as the intent indicates that there is no restriction on the amount of batteries that may be carried on board the aircraft as part of the aircraft useful load. And that the empty weight of the aircraft without batteries remains at 254 pounds.” The Office of the Chief Counsel did not agree. In fact, the occ had a completely opposite opinion, stating that batteries did not count as fuel, but instead counted against the empty weight of an ultralight. The official faa response is included with this white paper. It would seem that both sides staked out extreme positions on this issue. The language in the request was extreme because it claimed there should be no limits of any kind on the number of batteries on board an ultralight. That, in spite of the fact that the faa made it clear in the preamble to Part 103 that some kind of limitation on both empty weight and fuel capacity was necessary in the definition of an ultralight. For its part, the Office of the Chief Counsel seemed to ignore the fact that the source of energy for an electric aircraft (its fuel) is the batteries themselves. Their argument was confusing in that they seemed to believe that it was relevant that thermal fuels were expended during flight, when that is not spelled out in Part 103, the preamble to Part 103, or in any other obvious faa documentation. That extreme position makes sense since the Office of Chief Counsel was only asked to interpret the rule in a narrow sense. And perhaps the perceived risk of unlimited battery power tainted the process. This leaves electric aircraft in a unique position of having a definite source of power that seems to have an unclear status in the regulations. And in fact this newer, cleaner source of energy is penalized for not having the exact same nature as fossil fuels. That is because a completely ‘fueled’ Part 103-legal electric ultralight may only weigh 254 pounds compared to the completely fueled thermal engine weighing 284 pounds or more. Nominally that is a difference of 30 pounds. A gasoline-powered ultralight may weigh almost 12% more than an electric-powered ultralight. The other part of the problem is that the energy density of batteries is far lower than that of carbon-based fuels. Fred Schlachter, writing for the American Physical Society’s aps News 1 stated: “Stored energy in fuel is considerable: gasoline is the champion at 47.5 MJ/kg and 34.6 MJ/liter; the gasoline in a fully fueled car has the same energy content as a thousand sticks of dynamite. A lithium-ion battery pack has about 0.3 MJ/kg and about 0.4 MJ/liter (Chevy VOLT). Gasoline thus has about 100 times the energy density of a lithium-ion battery.” Mr. Shlachter goes on to say that there are some efficiencies to be had in electrical power systems, but that we are nowhere near attaining the effective range of gasoline 103.1 Applicability This part prescribes rules governing the operation of ultralight vehicles in the United States. For the purposes of this part, an ultralight vehicle is a vehicle that: (a) Is used or intended to be used for manned operation in the air by a single occupant; (b) Is used or intended to be used for recreation or sport purposes only; (c) Does not have any U.S. or foreign airworthiness certificate; and (d) If unpowered, weighs less than 155 pounds; or (e) If powered: (1) Weighs less than 254 pounds empty weight, excluding floats and safety devices which are intended for deployment in a potentially catastrophic situation; (2) Has a fuel capacity not exceeding 5 U.S. gallons; (3) Is not capable of more than 55 knots calibrated airspeed at full power in level flight; and (4) Has a power-off stall speed which does not exceed 24 knots calibrated airspeed. The current interpretation of the regulations means that the difference in the legal takeoff weight (minus pilot) for a ‘thermal’ powered ultralight (one that burns a fuel) vs. an electric powered ultralight is striking. Support Our Advertisers powered engines. That means that in order to attain similar performance numbers, more weight for electric-powered ultralights is justified, not less. The graph above shows that there are a variety of allowed weights for legal ultralight aircraft, depending on their configurations. It is important to understand that these configurations are allowed for both in the regulations and in AC 103-7. Allowing for greater empty weights for powered ultralights would require at least an exemption from the rules, or in the long term a regulation change. Regulation change is not an approach that usua or lama recommends. Possible Solutions There are a number of possible solutions for addressing the disparity between electric and thermal engine ultralights: Regulation Change is the least favored approach. It seems unnecessary and is a difficult process with little chance of success. Manufacturer Exemptions could be applied for on a model-bymodel basis. This would increase the burden on both manufacturers and the faa. Organization Exemptions could be applied for and administered by member organizations. This is a viable route and might be a valid approach. This could offer more indirect control by the faa for either the manufacture or the training (or both) for electric aircraft. However, a good approach would be to go back to the black letter of the law. The regulation says specifically “Has a fuel capacity not exceeding 5 U.S. gallons.” Understanding that the reality is that batteries are indeed the fuel source for an electric aircraft, it seems to make sense to address that reality and simply use 5 U.S. gallons of batteries as the fuel limit for an ultralight. Doing this would add clarity to a confusing situation. Prior to 2012, the faa actually made a statement at AirVenture saying that 5 gallons of batteries would be considered 5 gallons of fuel and electric ultralight builders have been using that as the standard since then. The overreach built into the request for a legal interpretation and the resulting overreaction to that overreach has confused designers and pilots alike. 5 U.S. gallons of batteries does not give the industry everything that they want or need, but it gives the This bar graph illustrates that the on-the-runway, ready-tofly legal weights for ultralights vary quite a bit depending on how they are equipped and what kind of fuel they use. The current legal interpretation for electric ultralights puts electric ultralights at the lowest maximumweight for a powered ultralight.
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