Building an airplane – the backstory

In mid-September, 2015, I first seriously broached the subject with colleagues of acquiring a manned ultralight airplane for research use. My sales pitch was that an ultralight aircraft could be flown inexpensively and at low speeds and altitudes (relative to conventional airplanes) and thus open the door to routine airborne observations and measurements by UW-Madison researchers. Examples include measurements of surface-air exchange processes, remote sensing and imaging experiments, and support for meteorological field experiments requiring information collected at altitudes well above the surface.

By definition (in the U.S.), an ultralight aircraft is one that weighs less than 254 lbs. empty, carries only one person (the pilot), and is capable of flying at speeds as slow as 28 mph or even less (for the complete rules pertaining to recreational use of ultralights, see Part 103 of the Federal Aviation Regulations).

Unmanned aerial vehicles (UAVs, or drones) are – for good reason – getting a lot of buzz these days for both commercial and research applications. But small UAVs – the only kind within reach of most research users – have significant practical limitations, including regulatory restrictions on how and where they may be flown as well as a typical maximum payload capacity of only a few pounds.

Unlike drones, a manned ultralight aircraft can be flown without the 400 foot altitude restriction and without the need to remain within line of site of an surface-based observer, adding considerable flexibility to the missions it can undertake. And 20 or so pounds of payload in addition to the pilot should not be out of the question.

We are certainly not the first to recognize the unique role that manned ultralight aircraft can fill in the atmospheric and environmental sciences. For example, Wolfgang Junkermann and associates at the Fraunhofer Institut für Atmosphärische Umweltforschung in Garmisch-Partenkirchen, Germany, began using a weight-shift “trike”-style ultralight to measure radiation and chemical constituents aloft over 17 years ago (e.g., Junkermann 2001).

There was another angle to ultralights that fascinated me, though, and that was the possibility of electric-powered flight for manned airborne research. Unlike a two-stroke gas-powered engine – the conventional powerplant for ultralights – an electric motor drive would produce less noise and less vibration, and no pollutants like volatile organic compounds or particulate matter to contaminate the environment being measured – an important consideration when air quality measurements are the specific purpose of the flight. Moreover, modern electric motors are far less susceptible to sudden failure than two-stroke gas engines, meaning that extremely low altitude surveys could be flown more safely over forested areas or other rough terrain lacking open fields for emergency landings.

Why haven’t electric motors been used routinely on ultralights before now? The reality is that only very recently has battery technology advanced to the point where it can deliver a high enough energy density (energy per unit weight or volume) to be useful for manned aircraft. Even then, it’s really only an option for a lightweight aircraft that requires relatively little power. An ultra-slow ultralight is the perfect candidate.

After considerable red tape, we ultimately obtained permission from the State of Wisconsin to purchase an ultralight for the University of Wisconsin–Madison. Four partners – Profs. Ankur Desai and Tristan L’Ecuyer, the Space Science and Engineering Center (SSEC), and I – teamed up to fund the purchase of a Zigolo MG-12 ultralight kit from Aeromarine LSA in Lakeland, Florida, the U.S. dealer for the Italian manufacturer of the kit.

The Zigolo MG12 ultralight aircraft.

Because of its light weight, ultra-low speed, and consequent low power requirement, the Zigolo was identified by Chip Erwin of Aeromarine LSA as an exceptionally suitable candidate for electric drive. He and his team have been working on developing an electric drive system optimized for this platform. Flight times of up to one hour may be possible on a single charge, depending on weight and other conditions.

We will be working with Chip to replace the gas engine with the electric motor as soon as his conversion package is ready for market (the plan is keep the gas motor on hand for missions requiring longer time aloft and where exhaust emissions and vibration are not important concerns).

The order was placed in February 2017, and the kit is finally scheduled to arrive after many long delays (e.g., a port strike in Spain!) tomorrow, June 30, 2017! Subsequent blog posts will be devoted to documenting highlights from the build as well as subsequent testing and field deployments.

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