December 7, 1992
DUAL BRAKE BRAKING PROBLEMS
Kitfox™ OWNERS WITH THE DUAL BRAKE OPTION
SKYSTAR AIRCRAFT CORPORATION
pilots have discovered a potential problem with the standard dual brake
set up. Under a certain set of conditions, the brakes of the aircraft
can lock—up and do not release with out bleeding pressure from the
brake line to the caliper. This phenomenon occurs when the copilot’s
brakes are applied, then the pilot’s brakes are applied (while the
co-pilot is still applying pressure on his brakes), and then the copilot
releases his brakes with the pilot’s brakes still applied. With this
condition, the master cylinder and “slave” cylinder configuration of
Matco brakes, traps the pressure and does not allow the pressure to be
released. The brakes remain locked.
the “slave” cylinder is depressed first (co—pilot’s side),
pressure is created by the piston moving down the cylinder to the
caliper. If the master cylinder is depressed after the slave, it’s
piston moves just a fraction of the distance, because the slave has
already extended the calipers. Now when the slave is released, the
master’s piston force increases against the master’s shaft, with
very little shaft upward movement to allow a decrease in the pressure
pushing against the master’s piston. When the master’s piston
reaches its “stop”, the fluid pressure against this piston is
greater than the spring retaining the “stop”. Therefore, the
“stop” can not allow the shaft to open the bleed hole in the piston
to release the pressure: thus, brake lock occurs.
engineering representatives are currently in contact with the brakes
manufacturer, and are trying to resolve this problem. This Service
Letter will be followed up with a Bulletin on specific instruction. Until
such time. it is recommended
that one person only
braking control of the aircraft.
Please call SkyStar’s Technical Department if you have questions regarding the installation of dual brakes. Ph: 208—466—1711 or Fax: 208—466—7194.