Aviation Week & Space Technology - January 15, 2015

AviationWeek.com/awst AVIATION WEEK & SPACE TECHNOLOGY/JANUARY 15-FEBRUARY 1, 2015 33

Graham Warwick Washington

Weighty Matter

Terrafugia wants FAA to waive limits so its

flying car can still be called a light sport aircraft

D

esigning a flying car capable

of meeting both aviation and

highway safety requirements

is proving a weightier challenge than

imagined by startup Terrafugia when

it launched development of the Transi-

tion roadable aircraft in 2006.

The company has petitioned the FAA

for a waiver of the gross-weight and stall-

speed limits on the light sport aircraft

(LSA) category, arguing the design’s au-

tomotive crashworthiness features and

ability to land and drive through bad

weather will increase safety.

Terrafugia is requesting permission

for the two-seat Transition to have a

takeoff gross weight of 1,800 lb. and

stall speed of 54 kt., yet still be treat-

ed as an LSA that can be self-certified

by the manufacturer against industry

standards accepted by the FAA.

LSA rules limit landplanes to a max-

imum weight of 1,320 lb. and stall speed

of 45 kt. In 2010, to accommodate

road-safety features such as airbags,

Terrafugia successfully petitioned the

FAA to certify the Transition with a

gross weight of 1,430 lb., the limit for

seaplane LSAs.

“We now have quite a bit more infor-

mation about what it will actually take

to meet the level of safety that we be-

lieve is appropriate for this type of ve-

hicle, and it simply takes more weight

than we were previously allowed,” says

CEO Carl Dietrich.

“The Transition was designed to be

very simple to operate, in the spirit of

the LSA rule,” he says. “In my view, it

would be silly and unfortunate to allow

an arbitrary weight number associated

with a category to inhibit meaningful

improvements in safety and techno-

logical advancement.”

Established in 2005 in a bid to re-

vitalize general aviation by lowering

the cost of aircraft ownership and

pilot training, the LSA rule defines a

simple, low-performance aircraft that

the manufacturer can self-certify at a

significantly lower cost than for FAA

Part 23 certification.

Terrafugia states that even at a high-

er weight, the Transition “still belongs

in the LSA category. It is easy to fly,

maintains a comfortable stall margin

and benign stall characteristics, and

embodies the original intent of LSA

as a means to encourage innovation

and growth in the aviation industry.”

Since 2010, the FAA has granted

Icon Aircraft an exemption to LSA

rules to increase the maximum take-

of weight of its amphibious Icon A5

by 250 lb. to 1,680 lb. to accommodate,

among other features, a spin-resistant

airframe design.

“In 2010 the FAA did not want to set

a precedent beyond 1,430 lb. They have

now broken that rule and set a new

precedent with Icon at 1,680 lb.,” says

Dietrich. “In my view, our case is even

more compelling than Icon’s in terms

of improving safety and the clear con-

nection between the safety improve-

ments and weight requirements.

“I believe it would be a mistake

for the FAA to prevent this product

from coming to market as an LSA.

With LSA treatment, we will be able

to bring our safety improvements to

more people faster, so this exemption

request should be in line with the high-

level mission of the FAA.”

The Transition is being designed

to meet federal safety standards for

multi-purpose passenger vehicles, and

as a result “will set the highest bar for

occupant safety in general aviation,”

Terrafugia states in its petition. But

occupant-protection features add 121 lb.

A ballistic recovery parachute for im-

proved flight safety adds 36 lb., while the

aircraft’s roadability features, including

the ground drive system, add 266 lb.

“The primary driver for the additional

weight is the incorporation of the sys-

tems and structure necessary for safe

road use in general and crashworthiness

in particular,” says the petition. Meet-

ing frontal-impact standards requires a

safety cage that adds 44 lb. to the com-

posite structure, and a crumple zone and

bumpers that add 25 lb. Airbags, knee

bolsters, head-impact protection, self-

tensioning and load-limiting seatbelts,

and other features together add 52 lb.

Explaining the request to increase

stall speed, the petition states: “Due

to the dimensional constraints of road

use... it is not feasible to simply in-

crease wing area proportionally to the

increased weight. Based on a spectrum

of pilot experience, Terrafugia believes

the necessary stall speed increase will

not afect the underlying safety intent

of an easy-to-fly LSA.” c

TECHNOLOGY

NASA

The need to fold the wing for

road driving means Terrafugia

cannot increase the Transition’s

wingspan to maintain stall

speed at an increased weight.