Zee.Aero Inc.

2700 Broderick Way, Mountain View, CA 94043

(650) 964-4570

October 20, 2014

U.S. Department of Transportation

Docket Operations

West Building Ground Floor, Room W12-140

1200 New Jersey Avenue, SE.

Washington, DC 20590

Dear Sir or Madam:

Zee.Aero was founded in 2010 to develop environmentally friendly airplanes for practical 

personal transportation. The company is exploiting technology advances in electric energy 

storage and motor systems, augmented flight controls, and composite structures. 

We request an exemption to 14 CFR 91.151(a)(1) to allow our manned aircraft using electric 

propulsion to fly with a reduced “fuel” reserve during our FAA-approved research and 

development flight test program. The specific sections of 14 CFR from which Zee.Aero seeks an 

exemption are as follows:

§91.151 Fuel requirements for flight in VFR conditions.

(a) No person may begin a flight in an airplane under VFR conditions unless (considering 

wind and forecast weather conditions) there is enough fuel to fly to the first point of intended 

landing and, assuming normal cruising speed—

(1) During the day, to fly after that for at least 30 minutes.

Rationale for request

The aircraft under development incorporate unique design and system features that provide an 

equivalent or higher level of safety compared to liquid-fueled spark ignition propulsion systems. 

During all test flights, the aircraft will be flown under a tightly controlled set of conditions, and a 

test team will monitor airport traffic conditions, weather conditions and the health of aircraft 

systems. These procedures will mitigate local air traffic conflicts and protect persons and property 
Zee.Aero	14	CFR	91.151(a)(1)	exemption	request 2

on the ground. Relevant aircraft and operational parameters and safety features include:

Aircraft Safety Characteristics

• The Zee.Aero electric propulsion system (EPS) utilizes solid-state electronics and 

redundancies with few moving parts. This is in contrast with a carburetor/fuel injector

system, fuel lines and associated metering systems with the inaccuracies inherent in a 

traditional liquid fueled propulsion system.

• A battery and energy flow management system provides precise real-time state of energy

remaining and time-remaining warnings to the pilot.

• An independent health monitoring system and proprietary battery architecture assures a 

high level of protection from thermal runaway or other electrical system failure.

• A ballistic recovery parachute is available to recover pilot and vehicle in an emergency.

Operational Safety Plans

• Detailed failure scenario fight planning enable the pilot and flight test team to ensure that 

the planned reserve is always available and that communication of planned landing will 

be accurate and complete. This type of planning includes, but is not limited to;

o A safe cone of operations established for each flight that enables an engine out 

glide to a runway for either an upwind or downwind landing.

o Ground station and cockpit monitoring to keep flight operations within the safe 

cone of operations at all times.

o Takeoff, departure, and landing profiles that prescribe landing options as a 

function of altitude and aircraft position.

• The EPS is continuously monitored both in the cockpit and via a ground test station. 

Hardware redundancy and operational restrictions have been established to mitigate the 

effects of EPS failures.

• All test flights will be conducted outside controlled airspace, within sight of the base 

airport and only when sustained winds are 10 knots or less.

• The aircraft will only be flown by highly qualified test pilots listed in the approved flight 

test program.

With these aircraft safety features and operational controls, Zee.Aero is confident that its airplane 

can be operated as safely as traditional gas-powered airplanes operating under §91.151.
Zee.Aero	14	CFR	91.151(a)(1)	exemption	request 3

The request for a lower fuel reserve is also based on endurance restrictions due to the significant 

weight penalty of currently available battery systems. State of the art batteries for this type of 

application have, at best, nine times less energy density by weight than aviation gasoline. 

Therefore, to stay within safe design limits, the energy storage system in the initial Zee.Aero test 

airplanes will only allow a maximum 25-minute flight at cruise power with a 5-minute reserve.

Adding more batteries to extend flight time will not be feasible during the test phase.

Based on the above information, Zee.Aero requests a minimum 5-minute fuel reserve. This would 

allow time for contingencies such as loitering for traffic and at least one go around.

Public Interest

Zee.Aero is leading the development of new technologies to advance the safety, capability, userfriendliness and public acceptance of personal aircraft. Grant of the exemption to CFR 

91.151(a)(1) will allow Zee.Aero to conduct flight-testing in controlled conditions to demonstrate 

the viability of these new technologies. The results of this work will confirm that the technologies 

are viable and can benefit the public. This will lead to a higher level of safety and increased 

accessibility to the benefits of personal flight than is currently available with traditional General 

Aviation aircraft. 

For the Federal Register

Zee.Aero requests an exemption to 14 CFR 91.151(a)(1) to allow its manned aircraft using 

electric propulsion to fly with a reduced “fuel” reserve during its FAA-approved research and 

development flight test program.

We look forward to a positive response. Please feel free to contact me at 

tom.gunnarson@zee.aero or 301-471-1923 with any questions concerning this request.

Sincerely,

Tom Gunnarson

Lead of Certification and Regulatory Affairs