Jetrader - Spring 2015 - 32

aviation history

Pitcairn's Autogiros:
An Idea Whose Time
Came and Went

By Jack Feir, Administrative Director, ISTAT Appraisers' Program

How Does the Autogiro Work?
Like a conventional airplane, the
original autogiros were powered by an
engine which turns a propeller to provide forward thrust. A three- or fourblade rotor turned freely on a simple
spindle, providing lift. There was no
need for a transmission and driveshaft
to turn the rotor, nor a gear box to drive
a tail rotor to counteract torque from
the main rotor.
To take off, the autogiro would taxi
to a position facing into the wind, and
if the wind was anything more than a
light breeze the rotor would automatically begin to spin. Then, with full power
applied to the propeller the aircraft could
be airborne at a leisurely forward speed
after a very short ground roll. If there
was only a light wind, the ground roll
would be a longer as the forward speed
brought the rotor up to the required rpm.
To land, power was reduced and the rotor
continued to spin so that the gliding
speed was very low, and the autogiro
could touch down and roll to a stop
within its own length.
Directional control was via a conventional rudder, and roll control was
achieved by ailerons on the stub wings.
The wings themselves provided practically no lift; they were there primarily to
be something to which the ailerons could
be attached. In later models, the pilot
could tilt the rotor directly so the wings,
elevators and ailerons were not needed.

In the Beginning: The First Autogiro
Juan de la Cierva, a Spanish engineer and inventor, was the first to conceive of
the basic principles of the autogiro. Freely rotating airfoils generated aerodynamic
forces, producing lift from the air flowing up through the rotor disc, and at the
same time the aerodynamic forces automatically kept the rotor turning, a process
that he described as "autorotation." After several attempts he achieved the world's
first autogiro flight at an airfield near Madrid in early 1923. In 1925 Cierva moved
to England, formed Cierva Autogiro Ltd., and devised further improvements to the
autogiro concept.

Harold Pitcairn
Like Juan de la Cierva in Europe, in the U.S. Harold Pitcairn was also an engineer
and inventor with a flair for aviation.
In 1924 he founded the Pitcairn Flying School and Passenger Service, and in 1927
he won the government air mail contract for the New York to Atlanta route, but soon
realized that the available aircraft in those days were not up to the job. Pitcairn's
solution was to design his own aircraft, which emerged as a sleek biplane that was
faster, safer and more efficient than any other on the market. Known as the Pitcairn
Mailwing, it was so successful that other air mail operators lined up to buy them for
their own fleets.
In 1929, he sold the airline, then known as Pitcairn Aviation, to a syndicate of
Curtiss Wright and General Motors for $2.5 million. The airline's name was changed
to Eastern Air Transport, later to become Eastern Airlines. Meanwhile, the Pitcairn
Aircraft Company, which he retained, continued to manufacture the Mailwing biplanes
for the airlines, as well as "sport" versions for private owners, providing Pitcairn
with steady cash flow for several more years.

The Search for a Safe Aircraft
Pitcairn's prime objective was to develop safer and easier-to-fly aircraft than those
available in the 1920s. He observed that most crashes then (and still now) occurred
during takeoffs and landings, and he reasoned that such crashes would be less likely,
as well as less deadly, if takeoffs and landings could be performed at much lower
speeds. The problem was that conventional wings needed high speeds in order to
develop enough lift to take off. But what if the wings were moving faster than the
airplane? What if they whirled around like a pinwheel, creating lift? Would this be
possible without resorting to the daunting complexity of a helicopter, a concept
that was so far impractical? Indeed, it was possible, and with the money from the
sale of the airline, Pitcairn set to work.

32 The official publication of the International Society of Transport Aircraft Trading

Jetrader - Spring 2015

Table of Contents for the Digital Edition of Jetrader - Spring 2015