AFS-15-093-E

Exemption No. 11320

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

WASHINGTON, DC 20591

 

In the matter of the petition of 

 

ZEE.AERO, INC Regulatory Docket No. FAA-2014-0882

 

for an exemption from § 91.151(a)(1) 

of Title 14, Code of 

Federal Regulations 

 

DENIAL OF EXEMPTION

By letter dated October 20, 2014, Mr. Tom Gunnarson, Lead of Certification and Regulatory 

Affairs, Zee.Aero Inc. (Zee.Aero), 2700 Broderick Way, Mountain View, CA 94043 

petitioned the Federal Aviation Administration (FAA) on behalf of Zee.Aero for an exemption 

from § 91.151(a)(1) of Title 14, Code of Federal Regulations (14 CFR). The proposed 

exemption, if granted, would allow its manned aircraft using electric propulsion to fly with a 

reduced “fuel” reserve during their FAA approved research and development (R&D) flight 

test program.

The petitioner requires relief from the following regulation[s]:

Section 91.151 Fuel requirements for flight in VFR conditions prescribes, in pertinent part, 

that 

(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.
2

The petitioner supports its request with the following information:

The petitioner states the aircraft under development incorporates unique design and system 

features that provide an equivalent or higher level of safety compared to liquid-fueled spark 

ignition propulsion systems. The petitioner states that 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 during all test flights. Additionally, Zee.Aero 

states that these procedures will mitigate local air traffic conflicts and protect persons and 

property on the ground. Relevant aircraft safety characteristics, operational controls, and 

safety features listed by Zee.Aero 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 enables 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.
3

• All test flights will be conducted in visual meteorological conditions under day visual

flight rules, 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. Pilots will also receive mission simulation and flight training in a 

Z-P101 specific fixed base, immersive aircraft simulator with realistic flight 

instruments, control stick and throttle, and aerodynamic performance modeling.

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.

The petitioner states that the request for a lower fuel reserve is also based on endurance 

restrictions due to the significant weight penalty of currently available battery systems. 

Further, Zee.Aero has determined that the 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, according to the petitioner, allow time for contingencies such as loitering for traffic 

and at least one go around.

Public Interest

Zee.Aero states that its company is leading the development of new technologies to advance 

the safety, capability, user- friendliness and public acceptance of personal aircraft. The results 

of this work, Zee.Aero believes, will confirm that the technologies are viable and can benefit 

the public and 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.

A summary of the petition was published in the Federal Register on December 12, 2014,

(79 FR 75610). No comments were received.

The FAA’s analysis is as follows:

The FAA agrees with the petitioner that alternative methods of propulsion would serve the 

public interest by reducing or eliminating consumption of traditional fuels, providing a more 

cost effective and environmentally friendly benefit to personal flight. However, the FAA 

believes that Zee.Aero does not substantiate the necessity of a grant of exemption to conduct 

flights in electric, battery powered aircraft without the minimum fuel reserve for day VFR 

flight.
4

Zee.Aero is not unique in that electric, battery powered aircraft currently operate worldwide. 

European designs include battery powered electric motor-gliders, as well as single and 

multiengine aircraft. Unmanned Aircraft System (i.e. drone) aircraft also utilize non-fueled, 

electric motors with battery power. As an example, GreenWing International designs an 

experimental, amateur built aircraft with battery powered electric motors that meets the 

requirements of Section 91.151(a)(1). Additionally, Aero Electric Aircraft Corp (AEAC) has 

developed a solar-electric powered aircraft. The AEAC Sun Flyer airplane is currently 

involved in initial R& D flight test operations at Centennial Airport near Denver, CO. These 

non-fuel operated aircraft do not require an exemption from Section 91.151(a)(1) because they 

operate with the VFR 30 minute reserve required by regulation. 

The petitioner states that the request for a lower fuel reserve is based on endurance restrictions 

due to the significant weight penalty of currently available battery systems. The petitioner’s 

reasoning that weight limitations prevent longer sustained flight is insufficient for the FAA to 

grant an exemption. Similar airplanes have conducted R&D flight operations without relief 

from 91.151(a)(1). 

The FAA notes that the airfield chosen by Zee.Aero, Inc. for R&D flight tests has significant 

general aviation flight activity according to information displayed in the U.S. & Territories 

Airport Lookup on the FAA.gov website 

(https://nfdc.faa.gov/nfdcApps/airportLookup/index.jsp?category=null) as well as 

AeroNav.Com. AeroNav.com displays the following operational statistics for a 12-month 

period ending 12 August 2014:

Aircraft based on the field: 178

Single engine airplanes: 99

Multi engine airplanes: 7

Jet airplanes: 5

Helicopters: 2

Gliders airplanes: 45

Ultralights: 20

 

Aircraft operations: avg 144/day 

57% local general aviation

41% transient general aviation

2% military

General Remarks:

• MODEL ACFT CLUB CONDUCTING FLT OPNS 3 MILES WNW OF ARPT 

HEADING OF 290 DEGREES FM ARPT SURFACE TO 500' AGL.

• CAUTION-WATCH FOR FIRE FIGHTING ACFT JUNE THRU OCTOBER
5

.

• GLIDER ACTIVITY ON AND INVOF ARPT.

The petitioner did not submit a plan to communicate their R&D activities to non-participating 

aircraft nor did they submit a substantial risk mitigation plan designed to minimize exposure 

to non-participating aircraft.

The FAA’s Decision:

In consideration of the foregoing, I find that a grant of exemption would not provide a level of 

safety at least equal to that provided by the regulations. Therefore, pursuant to the authority 

contained in 49 U.S.C. §§ 106(f), 40113 and 44701, delegated to me by the Administrator, the 

petition of Zee.Aero Inc. for an exemption from 14 CFR § 91.151(a)(1) is hereby denied. 

Issued in Washington, D.C., on April 13, 2015. .

//s//

John S. Duncan

Director, Flight Standards Service