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Terrafugia Inc.

23 Rainin Road 

Woburn, MA 01801

T: +1-781-491-0812

F: +1-781-491-0282

www.terrafugia.com

May 4, 2016

US Department of Transportation Docket Management System

West Building Ground Floor, Room W12-140

1200 New Jersey Avenue, SE

Washington, DC 20590

Re: Amendment to Exemption Number 13492 Pursuant to Section 333 of the FAA Reform Act 

and Part 11 of the Federal Aviation Regulations; Regulatory Docket No. FAA-2015-1382

Dear Sir or Madam:

Terrafugia, an operator of Small Unmanned Aircraft Systems (sUAS) for research and development, 

hereby applies for an amendment to the referenced Section 333 exemption that the FAA granted on 

October 22, 2015, allowing commercial operations of Terrafugia’s sUAS.

The requested amendment clarifies flight operations under paragraph 8 of the FAA’s grant of 

exemption dealing with functional test flight operations, and it aligns paragraphs 18 and 20 with 

the developmental nature and capabilities of Terrafugia’s sUAS. The requested amendments and 

rationale are discussed in Appendix A. These amendments do not change the intent or the 

equivalent level of safety provided by the original exemption letter. These clarifications preserve 

the FAA’s rationale for finding that the grant of exemption is in the public interest as stated on page 

2 of the referenced grant of exemption. That is:

“...enhanced safety using an unmanned aircraft (UA)...carrying no passengers or crew, 

rather than a manned aircraft of significantly greater proportions, carrying crew in 

addition to flammable fuel, gives the FAA good cause to find that the UAS operation 

enabled by this exemption is in the public interest.”

The name and address of the applicant are:

Terrafugia, Inc.

Attn: Kevin Colburn

23 Rainin Road

Woburn, MA 01801

Ph: 781-491-0812

Email: kcolburn@terrafugia.com
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If any additional information is needed, please contact me at 781-491-0812 or 

kcolburn@terrafugia.com.

Thank you for your consideration.

Sincerely,

Kevin Colburn

Chief Operating Officer

Terrafugia, Inc.

23 Rainin Road

Woburn, MA 01801
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APPENDIX A

BACKGROUND

The grant of exemption assumes an sUAS vehicle that is fully developed and allows for functional 

test flights under paragraph 8. Since the Terrafugia TF-XTM sUAS is in development, Terrafugia is 

requesting expanded language under paragraph 8 to more clearly cover developmental test flights. 

At a minimum, these test flights will be developing the capabilities addressed in paragraphs 18 and 

20. Terrafugia is requesting Equivalent Level of Safety amendments to those paragraphs to 

facilitate development.

Terrafugia believes that these changes are within the spirit of the functional test flights allowed by 

paragraph 8 of the grant of exemption and requests the following amended language to make the 

spirit more explicit.

PARAGRAPH 8

REQUIREMENT AS WRITTEN

8. Any UAS that has undergone maintenance or alterations that affect the UAS operation or flight 

characteristics, e.g., replacement of a flight critical component, must undergo a functional test flight 

prior to conducting further operations under this exemption. Functional test flights may only be 

conducted by a PIC with a VO and must remain at least 500 feet from other people. The functional test 

flight must be conducted in such a manner so as to not pose an undue hazard to person and property.”

REQUESTED AMENDED LANGUAGE

8. Functional flight tests must be conducted for any UAS that has undergone maintenance or 

alterations that affect the UAS operation or flight characteristics, e.g., replacement of a flight critical 

component, prior to conducting further operations under this exemption. Developmental flight 

tests may be conducted by the manufacturer to facilitate the development and incorporation of new 

or modified systems and/or capabilities into the UAS. Functional and developmental flight tests 

may only be conducted by the minimum essential personnel as specified in an accompanying test 

plan and must remain at least 500 feet from other people. Due the nature of functional and 

developmental test flights, it may not be possible or practical for all of the provisions of this 

exemption to be met. As necessary for a given paragraph, the manufacturer may include alternative 

provisions in a functional or developmental flight test plan that maintains an equivalent level of 

safety for these test flights.

RATIONALE

The amendment expands paragraph 8 to cover both functional and development test flights. The 

original paragraph 8 requires that these flights may only be conducted by a PIC and VO. The 

amended language requests a change to “minimum essential personnel.” Because of the sequence 

of testing, functional and developmental test flight operations require other essential personnel in 

addition to the PIC and VO. These test flights will evaluate basic flight characteristics of vertical 

flight and transition to horizontal flight. Collecting data from the vehicle may require technicians 
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within 500 feet. Manipulation of the flight controls for specific test events during functional test 

flights will at times be accomplished by highly skilled engineers (experienced radio control aircraft 

operators) via a “buddy-box” control set up with the PIC in overall control. The PIC will always 

have the ability to assume control and ensure that the requirements of the COA will not be violated. 

These procedures provide an equivalent level of safety to the original language.

PARAGRAPH 18

REQUIREMENT AS WRITTEN

18. If the UAS loses communications or loses its GPS signal, the UA must return to a pre-determined 

location within the private or controlled-access property.

REQUESTED AMENDED LANGUAGE

18. In the event of a loss of communications signal, a means must be provided to ensure that the 

UAS remains within the private or controlled-access property until the flight can be safely 

terminated. The nature of those provisions shall be documented in the applicable test plan and/or 

UAS documentation.

RATIONALE

The TF-XTM sUAS is a scale model of a future full-scale powered lift/tilt-rotor category aircraft that 

will take off vertically and transition to horizontal flight. It is being designed and built by 

Terrafugia (the sUAS operator). The first flights will be manually controlled hover, just off of the 

ground. Terrafugia is requesting a change to Paragraph 18 to allow functional and test flights 

without the “return” capability because GPS guidance and thus the ability to “return” will not be 

added until later flights.

In the event of loss of signal during these manually controlled functional and developmental test 

flights, the UA will automatically reduce power and land immediately. These test flights will be 

procedurally limited so that in the event a loss of signal the UAS will land within the protected

access area where these tests will occur, thus providing an equivalent level of safety to the original 

language. 

Even after Terrafugia develops the “return” capability, the TF-X will be guided by GPS unless and 

until additional positional awareness systems may be developed. Thus, it will not be able to 

“return” in the event of a loss of GPS signal. As with the manually controlled flights, in response to a 

loss of GPS signal, the UAS will automatically reduce power and land immediately. Test flights will 

be procedurally limited so that in the event of a loss of signal, the UAS will land within the protected

access area where the tests will occur, thus providing an equivalent level of safety to the original 

language. 
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PARAGRAPH 20

REQUIREMENT AS WRITTEN

20. The PIC is prohibited from beginning a flight unless (considering wind and forecast weather 

conditions) there is enough available power for the UA to conduct the intended operation and to 

operate after that for at least five minutes or with the reserve power recommended by the 

manufacturer if greater.

REQUESTED AMENDED LANGUAGE

20. The PIC is prohibited from beginning a flight unless (considering wind and forecast weather 

conditions) there is enough available power for the UA to safely terminate its flight within the 

private or controlled-access property area in the event of a malfunction. In the absence of an 

alternate power reserve being specified within the applicable test plan and/or UAS documentation, 

a reserve of five minutes will apply.

RATIONALE

The TF-XTM sUAS is being designed and built by Terrafugia (the sUAS operator). The first functional

and developmental test flights have limited objectives — e.g., a one-minute stable hover. Thus it 

will not have the battery capability to comply with paragraph 20 (5 minutes of battery reserve). 

These flights will establish battery life (estimated to be approximately 5 minutes). The test flights 

will be procedurally limited so that in the event of battery failure, the UA will land within the 

protected access area, thus providing an equivalent level of safety to the original language.