CHAPTER 2
DESCRIPTION OF PROPELLANT ACTUATED DEVICES
demonstrate their interrelationship in actual systems.
6. General. a. The first aircraft pilot catapults and
The various means of transmitting energy from device
associated devices powered by propellants were called
to device in a system and proposed energy transmission
"Cartridge Actuated Devices" (CAD), a name which
methods also are discussed.
arose from the similarity in appearance between their
propellant containers and the cartridge case for an
7. Gas-Generating Devices. a. There are two basic
ordinary rifle. As new applications were developed, this
types of gas-generating devices: short duration
similarity disappeared, but the name continued to be
"initiators" and long duration "gas generators." These
used. Many of the older records will show this name.
devices consist of vented chambers containing
OTCM 37418 dated 12 April 60 was published to change
cartridges and firing mechanisms.
The firing
the name of future developments of these items to
mechanisms may be operated electrically, by gas
"Propellant Actuated Devices" (PAD), it being
pressure, or mechanically.
considered that this name more nearly expresses their
b. Initiators are designed primarily to supply gas
principal characteristic.
pressure to operate the firing mechanisms of other
b. The propellant actuated devices described in
propellant actuated devices, but they may be used as
this chapter have been divided arbitrarily into three
sources of energy for operating piston devices such as
categories: gas-generating devices, stroking devices,
safety-belt releases and safety-pin extractors. Initiators
and special purpose devices. Although special purpose
are used extensively in aircraft to operate the firing
devices could be classified as essentially gas generators
mechanisms of propellant actuated devices, since they
or stroking devices, they have been separated because,
eliminate cumbersome cable-pulley systems and
of specific applications.
provide a more reliable method of triggering.
In
systems where the propellant actuated device is remote
c. Various tables list data on the physical and
from the initiator, intermediate initiators (gas-actuated)
performance characteristics of propellant actuated
are used as boosters. For systems where propellant
devices already developed. Although rocket-assisted
actuated devices are fired in a sequence, initiators or
catapults are beyond the scope of this manual, the
other PAD's may contain combustion train elements
performance possible with these devices is compared to
(delay elements) to delay propellant ignition for a
that of conventional catapults.
specific time to permit completion of another operation.
d. Some propellant actuated devices combine the
A typical initiator is shown in figure 1. Comparative data
operations of several subdevices. Such a device is the
for several existing initiators are given in table II.
T28 initiator which combines release with a
c. Gas generators differ from initiators since an
mechanically operated initiator. The operation of this
initiator supplies gas for much less than 1 second, while
and other devices incorporating separate functions is not
a gas generator may supply gas for several minutes.
described, since an understanding of the individual
Gas generators (fig. 2) have been used to supply gas
functions is all that is necessary to understand the most
flow to spin turbines as well as for supplying pressure to
complex of these devices.
operate pumps which supply hydraulic pressure to
e. Several aircraft escape systems and missile
missile controls. Comparative data for gas generators
systems are described in order to illustrate the
are given in table III.
application of propellant actuated devices and
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