The aircraft systems (the fuel system, hydraulic
system, electrical system, pneumatic system, etc.)
were all relatively conventional except, perhaps,
for the landing gear and the flying controls system.
The tricycle landing gear consisted of a forward
retracting nose gear with dual wheels, and main
gear with twowheeled bogies, which retracted
inboard and forward into the wing.
Cockpit control was by means of a lever in the
shape of a wheel, located on the left-hand forward
panel, and it was operated by a simple up or down
motion.
Emergency lowering of the landing gear was by
a 5,000-psi nitrogen bottle, which, when activated,
released the door and gear uplocks, and the gear
then fell in a normal manner by gravity, aided
by air loads.
The problem with the CF-105 landing gear was
one of stowage. Because of the high, thin wing
the gear was relatively long. In order to
stow the gear, it had to be shortened and twisted
as it retracted. On June 11, on the 11 th flight
of the first airplane, the gear failed to extend
completely, even though cockpit indicators showed
it down and locked. The landing was made with the
left main gear cocked approximately 30° to
one side. In other words, it had not fully untwisted.
The landing roll was about 4,000 ft., and, of course,
with the port leg twisted it pulled the aircraft
to one side. As the aircraft left the runway and
came in contact with soft ground, the undercarriage
snapped. The aircraft came to rest on its
right gear and left wingtip.
Because of the excellent photographic coverage,
the cause of the accident was quickly determined.
Avro had the airplane flying again approximately
four months later, and flight procedure from that
time was to have a chase-plane check gear extension
prior to landing. Zurakowski was the pilot,
and I know that if he had only had some indication
of a problem, the accident would never have
occurred.
The CF-105 flying control system was a fully
powered, irreversible, artificial feel control
system. There were three modes of operation: a
normal mode, an automatic mode, and an emergency
mode. The automatic mode was not installed in the
early aircraft.
Two independent hydraulic systems provided the
muscle, each with two engine driven pumps.
The supply was 4,000 psi. Also, a ram air turbine
was to have been installed on later aircraft for
use in the event of a two-engine flameout.
In the normal mode, a damping system provided
stability augmentation for all three axes, and
co-ordinated rudder movement with movement of the
ailerons and elevators. Artificial feel was
provided by an electrical system in such a way
that stick force required was made to feel proportional
to the amount of g's
pulled. Stick force per g was constant, irrespective
of speed or altitude.
When the pilot exerted a -force on the control
column to move the elevators, a force transducer
on the control column transmitted electrical signals
to a series of servos, which converted the electrical
signals into mechanical movement by means of hydraulic
pressure. The electrical output at the transducer
was directly proportional to the force exerted
at the grip. The control column would move as the
force was exerted, as with a conventional flying
control system, but it was not moved directly by
the pilot. Movement of the control column
followed the positioning of the elevators. The
response of the system was instantaneous, and it
therefore appeared as if the control column
were moved by the pilot.
In the emergency mode, the force transducer was
taken out of the loop. The control column was linked
by cable directly to the hydraulic actuators, which
controlled the elevators. Artificial feel was provided
by a spring-loaded assembly along with a bob-weight,
which induced loads on the control column
and made control column movement progressively
heavy as g's were applied.
Operation of the ailerons and
the rudder by means of electrical signals, or by
cables, was very similar to operation of the elevators.
Components in the systems differed slightly, but
from the pilot's point of view, the systems operated
in a similar manner. The damping system was duplicated
in yaw, however, as this was the critical axis
and of major importance to the safety of the airplane
in the high-speed range. The airplane in the lateral-directional
axis was naturally unstable. It was designed
that way, by necessity, to meet performance guarantees
specified by the RCAF.
