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MIT Department of Aeronautics and Astronautics

AeroAstro Magazine Highlight

The following article appears in the 2005–2006 issue of AeroAstro, the annual report/magazine of the MIT Aeronautics and Astronautics Department. © 2006 Massachusetts Institute of Technology.

Transition: this personal vehicle’s future is in the air — and on the road

By Carl Dietrich

Common wisdom suggests that any vehicle design combining two disparate modes of transportation — flying and driving — will always result in a compromise that will do each task poorly, and, consequently, be unattractive to the marketplace. Advocates say that the potential benefits of such a vehicle could outweigh the performance compromises. Of course, such a bimodal vehicle presents a tremendous engineering challenge, and the devil is in the details. Only those details of the compromise will determine which school of thought is correct.

In Aero-Astro’s Wright Brothers Wind Tunnel, graduate student Anna Mracek, recent alumnus Dr. Samuel Schweighart (left), and doctoral candidate Carl Dietrich run tests on a model of Transition, the roadable airplane they hope to manufacture. (William Litant photograph)

Flying car team 1

In 1918, Felix Longobardi was issued the first U.S. patent for a vehicle capable of flying through the air and driving on the ground. In the ensuing 82 years, there have been nearly 100 published designs for vehicles that combine some of the features of a car with some of the features of an airplane. Some of these vehicles were actually built, and a handful of prototypes were even certified by the FAA. However, all of these ventures were commercial failures: the compromises that were sufficiently simple to prototype and certify, were operationally impractical. To date, not one of them has been successfully developed and certified.

Three graduate student/pilots from the MIT Department of Aeronautics and Astronautics believe that now is the time to make a truly practical dual-mode general aviation vehicle. They think that they know what sort of compromise will find commercial success. Anna Mracek, a graduate student in TELAMS; doctoral candidate Carl Dietrich, winner of the 2006 Lemelson-MIT Student Prize; and recent alumnus Dr. Samuel Schweighart have formed a venture they call Terrafugia — derived from the Latin for “escape the earth” — to develop a novel roadable aircraft design for the general aviation community.

Why would they see a need for a vehicle with implicitly compromised performance? To put it simply, they see a demand from the general aviation community for this type of vehicle.

In 2002, Troy Downen and Professor R. John Hansman of the MIT Department of Aeronautics and Astronautics published “User Survey of Barriers to the Utility of General Aviation.” In their paper they identified four primary barriers:

  • weather
  • expense
  • mobility at destination
  • doorstep to destination travel time

Expanding the general aviation market will be enabled by vehicles or systems that mitigate the impact of these barriers. Building a vehicle with just improved performance (faster and perhaps marginally more efficient) than existing GA aircraft certainly attacks the travel time barrier — and this has been the normal progression of GA to date. The market for single engine piston aircraft has fluctuated tremendously over the years, but advances in performance have not fundamentally expanded the market for new GA single engine planes. According to pilots — the primary GA users — improved performance does little to reduce the first three barriers to the more widespread use of general aviation.

component commonality

In Aero-Astro’s Wright Brothers Wind Tunnel, recent alumnus Dr. Samuel Schweighart (left), doctoral candidate Carl Dietrich, and graduate student Anna Mracek, with Transition, the roadable airplane they hope to manufacture. (William Litant photograph)

The introduction of a practical roadable  aircraft could directly reduce the effects of all four barriers (this is axiomatic — if it is practical, it will by definition address these barriers). An integrated roadable aircraft clearly improves a pilot’s mobility at their destination — eliminating any dependence on a rental car or taxi infrastructure, which does not exist at the vast majority of the 5,000-plus public use GA airports across the country. Even if these vehicles suffer a performance penalty in the air, doorstep-to-destination travel time could also be improved because of elimination of a need to secure another vehicle at the destination, and transfer people and bags between air and ground vehicles. Eliminating need for transportation changes at the destination airport would translate directly into time savings due to reduced planned time buffers.

A potential for reduced expense is an advantage of the new FAA light sport aircraft rule. This rule substantially reduces the barriers to certification of certain GA aircraft that fit within specified performance limitations. If there is a marked need for this sort of vehicle, costs per vehicle may be reduced as manufacturing rates increase in response to the demand. Finally, the biggest advantage of a roadable aircraft is a new relative insensitivity to weather conditions: if a storm threatens, the pilot can divert to the nearest field and drive safely under the weather. This fundamental improvement in safety by giving VFR pilots more acceptable options for safe travel, is perhaps the biggest advantage of the a road-worthy aircraft.

Terrafugia anticipates that pilots of the Transition Personal Air Vehicle — the name chosen for the new airplane-car — will be less-susceptible to “get-there-itis” (one of the most common reasons pilots put themselves in bad situations) than their GA counterparts. This safety advance is really an implementation of a combination of technologies based on an understanding of pilot psychology. Most GA accidents could have been avoided if the pilot had made at better decision at some point in time. By giving pilots more acceptable options for how to get where they want to go, Terrafugia believes that they will help GA pilots make better decisions – and save lives in the process.

Terrafugia is developing the Transition to satiate this perceived need in the general aviation community for a dual use vehicle. The Transition will be a two-place roadable aircraft designed to follow both National Highway Traffic Safety Administration guidelines and the newly implemented FAA Light Sport Aircraft consensus standards. These new FAA regulations substantially reduce the barriers to bringing a certified “light sport aircraft” to the general aviation market.

Terrafugia will benefit from more resources than its predecessors in addressing the roadable aircraft compromise. Since its inception shortly after the official announcement of the Light Sport Aircraft/Sport Pilot rule in September of 2004, Terrafugia has drawn technical and business lessons from previous attempts. It has developed four key pieces of intellectual property (patents pending). Vortex-lattice computer models have been built, more than 50 iterations of the vehicle’s outer mold-line analyzed, and currently a second round of wind-tunnel data is being collected in Aero-Astro’s Wright Brothers Wind Tunnel. Two pilots from the MIT Sloan School of Business have joined the core team, and Terrafugia is assembling a top-notch board of technical and business advisors from the ranks of the MIT Department of Aeronautics and Astronautics, the MIT Entrepreneurship Center, and the MIT Venture Mentoring Service.

The Terrafugia team and the Transition vehicle are examples of Aero-Astro at its best: an exciting, visionary project, assembled by a talented crew that’s benefited from the unique education and resources only MIT offers.

Carl Dietrich, non-current private pilot, received both B.S. ’99 and M.S. ’03 degrees from the MIT Department of Aeronautics and Astronautics where he is currently a doctoral candidate. Dietrich was winner of the 2006 Lemelson-MIT Student Prize for his inventive career. He may be reached at More information about Terrafugia and the Transition can be found at

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