Accumulators and Actuators

Question 1

dampen and absorb surges

maintains constant pressure in the hydraulic system

used in brake systems to provide backup braking and parking brakes

Answer 1

Purpose of accumulators

Question 2

3 Primary types of Accumulators:

Answer 2

Piston

Bladder

Diaphragm

Question 3

Accumulator type that is like a cylinder that is divided into two.

one side is hydraulic fluid and and other side is gas (nitrogen/helium)

Answer 3

Piston Type Accumulator

Question 4

Latest technology, eliminates elastomeric seals, which will eventually break down and leak

stainless steel design impervious to corrosion, capable of 8,000psi

MAINTENANCE FREE

Answer 4

Metal Bellows-Type Accumulator

Very high pressure

Question 5

2 Types of Actuators:

Answer 5

Linear

Rotary

Question 6

Type of Actuator that produces a straight line movement and consist a cylinder and piston.

Answer 6

Linear Actuators

3 types:

• SINGLE-ACTING
• DOUBLE-ACTING Unbalanced
• DOUBLE-ACTING Balanced

Question 7

Type of Linear Actuator that hydraulic pressure moves piston in one direction only

piston is returned by a spring

eg. shoe-type brakes:

Answer 7

Linear Actuator - Single Acting

Question 8

Linear Actuator that is normally used for such applications as flight controls and landing gear operations

for example, the large area of the piston is used for gear retraction

the smaller area of the piston is used for gear extension

Answer 8

Linear Actuators - DOUBLE ACTING UNBALANCED

Question 9

Linear Actutaor used for applications that require the same amount of force in both directions

Answer 9

Linear Actuator - Double Acting Balanced

Question 10

Actuator ‘cushions & slows’ piston travel at-or-near fully retracted position by restricting fluid flow.

‘Cushioning’ occurs during both ‘up & down’ selections when actuator is near its fully retracted pos’n.

Answer 10

Linear Actuator – Cushioned Gear-Type Actuator

Question 11

Linear Actuators – Lock-Type Actuator

Answer 11

The actuator has internal mechanical and hydraulic mechanism to ‘Lock’ the actuator.

Question 12

2 Types of Rotary Actuators:

Answer 12

rack and pinion

hydraulic motor

Question 13

one of the simplest forms of rotary actuators

piston has a rack of teeth cut into its shaft that mesh with those on a pinion gear

linear motion of the piston turns the pinion shaft, which raises and
lowers the landing gear

rotary motion is limited to the actuator linear travel

a gear system that converts linear motion of a hydraulic piston into rotary motion of a pinion gear

Answer 13

Rotary Actuator - RACK and PINION

Question 14

Rotary Actuator used where a continuous rotational force is required

Answer 14

Rotary Actuator - Hydraulic Motor

Applications:

• Power Drive Unit (PDU’s)
• Power Transfer Unit (PTU’s)

Question 15

leaks can occur external or internal

most leaks can be detected by visual inspection

it can be verified by:

Answer 15

• the applicable actuator
• will be warmer or hot
• ultrasound (NDT)
• pressure decay check
• shop bench test