Chapter 2. DESCRIPTION OF PROPELLANT ACTUATED DEVICES

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.

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