(fig. 2-13). Since air pressure applied to this
fitting bypasses the system regulator, the air
source must be controlled to less than 20 psi to
avoid rupturing the seal.
NOTE: Some aircraft are equipped with
canopy rain seals that protect the cabin area. In
aircraft so equipped, the canopy seal does NOT
have to be inflated for the cabin to be protected.
Rain seals do not maintain cockpit pressurization.
Troubleshooting charts similar to the one in
table 2-1 are found in most aircraft MIMs. The
troubleshooting chart is provided as an aid in
determining the cause, isolation procedure, and
remedy for the more common malfunctions
within the canopy seal system. When a mal-
function is suspected, always ensure that the
proper controls have been activated to provide
operating potential to the unit to be inspected.
Removal and Installation Procedures
The MIM provides the instructions and visual
aids necessary to remove and install the various
components of the canopy seal system. In
addition to instructions, information such as
disposition of defective parts, tools and equipment
requirements, and quality assurance instructions
is provided. When removing a unit from the air-
craft, always ensure that proper measures are
taken to prevent the entry of dirt and foreign
material into ports and ducts that have been
opened to accommodate removal.
Learning Objective: Recognize the purpose
and operation of a frangible escape system.
A frangible escape system is an explosively
operated system that cuts an exit through the
canopy directly over the head of each occupant.
The S-3A canopy removal system is an example
of this type system, and it employs shielded mild
detonating cord (SMDC) in lieu of hot gas and
flexible linear shaped charge (FLSC) in lieu of
actuators found in other hot gas explosive
Normal entry and exit of the S-3A aircraft is
through an entrance hatch vice a canopy, as in
other ejection seat type of aircraft. Therefore, the
S-3A canopy removal system is used primarily for
emergency ground egress and water rescue.
Normal seat ejection is through the canopy glass
for the front seats and through the hatch glass
for the rear seats. In both cases, exit is made
without benefit of having the glass removed or
cut because the seats are equipped with glass
crashers. Breaker plates are installed on each
canopy and hatch to assist the seat during
ejection. A brief description of the frangible
escape canopy system components is provided in
the following paragraphs.
EXTERNAL CANOPY AND HATCH
Two external jettison initiators are installed
inside access doors, one on each side of the
aircraft just below and forward of each windshield
Figure 2-13.Ground inflation of the canopy seal system.