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What should the inner diameter surface be checked for on an O-ring? (3)

small cracks, particles of foreign material, or other irregularities that cause leakage or shorten the life of the O-ring.

What are the two types of accumulators?

spherical and cylindrical.

Boeing 777 Hydraulic System, reservoir: The EDP draws fluid through a ___________. The ACMP draws fluid from the ___________________ reservoir.

standpipe. bottom.

O-Ring Installation: The slight ___________________ of the ring when it is rolled inside out helps to reveal some defects not otherwise visible.

stretching

O-ring Color Coding, What are the two difficulties of Manufactures color coding of O-rings?

the color coding system provides no means to establish the age of the O-ring or its temperature limitations.

If an excessive amount of foreign matter, particularly oil, is exhausted from any one system, what maintenance action should be done?

the lines and components should be removed and cleaned or replaced

Pneumatics System components, what is the purpose of the chemical dryer?

to absorb any moisture that may collect in the lines and other parts of the system.

What is the purpose of the heat exchanger in a hydraulic system?

to cool the hydraulic uid from the hydraulic pumps.

Both pneumatic systems and hydraulic systems are similar units and use confined fluids. What does the word confined mean?

trapped or completely enclosed.

In terms of linear actuators, How can a double acting cylinder hold load in a position?

uid pressure enters the right chamber, forcing the piston toward the left. As the piston moves toward the left, it pushes return uid out of the left chamber and through the selector valve to the reservoir.

What separate the nitrogen and hydraulic fluid in an accumulator? (2)

A synthetic rubber diaphragm, or bladder, is installed in the sphere to create two chambers.

Describe Backup rings made of Teflon™? (3)

Backup rings (MS28782) made of Te onTM do not deteriorate with age, are unaffected by any system uid or vapor, and can tolerate temperature extremes in excess of those encountered in high pressure hydraulic systems.

What are the 2 materials that seals for Skydrol are made of?

Butyl rubber or ethylene-propylene elastomers

How do you inspect the inner diameter of a surface of an O-Ring?

By rolling the ring on an inspection cone or dowel

Which lights illuminate if a low pressure is detected in the A and B hydraulic system?

Master caution and low pressure light

Which lights illuminate if a overheat is detected in the A and B hydraulic system?

Master caution and overheat light on the flight deck.

What turns the blades of a RAT?

Ram air turn the blades of a turbine which operates a hydraulic pump and generator.

What do relief valves protect a pneumatic system from?

Relief valves are used in pneumatic systems to prevent damage.

What type of pumps do low pressure systems obtain a supply of low-pressure air from?

vane-type pumps.

The word fluid implies such liquids as _________________

water, oil, or anything that ows.

Boeing 777 Hydraulic System, pumps: When does the EDPs operates?

whenever the engines operate.

Low-pressure systems are used for ______________

wing deicing boot systems.

In terms of linear actuators, What happens when pressure on the fluid is released in a single-action actuating cylinder?

When pressure on the fluid is released to the point it exerts less force than is present in the compressed spring, the spring pushes the piston back out.

Boeing 777 Hydraulic System: Can the module be bypassed if the filter clogs, and a visible indicator pops to indicate a clogged filter?

YES

The inspection of backup rings should include: (3)

a check to ensure that surfaces are free from irregularities, that the edges are clean cut and sharp, and that scarf cuts are parallel.

What do V-ring packings must have?

a male and female adapter to hold them in the proper position after installation.

Reservoirs: How are the AC pumps controlled?

a switch in the cockpit

In terms of accumulators, what is the initial charge referred to?

accumulator preload.

Seals are used to prevent fluid from passing a certain point, and to keep _____________ and ______________ out of the system in which they are used.

air and dirt.

Aircraft Pneumatic Systems: Such systems operate a great deal like hydraulic systems, expect they employ _____________ instead of a _____________ for transmitting power.

air. liquid

Some of the more common gasket materials are (4)

asbestos, copper, cork, and rubber.

O-Ring Installation: What should be avoided during the installation of an O-ring?

avoid rolling and twisting the O-ring to maneuver it into place.

O-Ring Installation: What should you be careful of while using the seal removal and the installation tools?

avoid using pointed or sharp-edged tools that might cause scratching or marring of hydraulic component surfaces or cause damage to the O-rings

Hydraulic Motors are either of the, (2)

axial inline or bent-axis type.

The standby hydraulic system is provided as a ___________ if system A and/or B pressure is lost.

backup

O-Ring Installation: Each replacement O-Ring should be removed from its sealed package and inspected for defects, such as: (4)

blemishes, abrasions, cuts, or punctures.

Pneumatics System components, each chemical drier contains a cartridge, what colour is the cartridge if it is serviceable?

blue in color.

The O-ring packing seals effectively in _________________. This sealing is done by _________________ of its elastic compound.

both directions. distortion of its elastic compound.

Gases are highly ________________

compressible

Pneumatics System components, Desiccant/Moisture Separator: Its purpose is to remove any moisture caused by the ____________

compressor.

Filter units: Filters have a ____________________ that _________________ when the filter is dirty and needs to be replaced.

differential pressure indicator. pops out

In terms of linear actuators, The operation of a _______________ is usually controlled by a four-way selector valve.

double-action actuating cylinder

These low pressure pumps are driven by _________________ or by the ______________.

electric motors or aircraft engine

The Ram Air Turbine (RAT) is installed in the aircraft to provide___________ and _____________ power if the primary sources of aircraft power are ___________.

electrical. hydraulic. lost.

Gaskets are used in fluid systems around the ________________ of actuating cylinders, valves, and other units. The gasket generally used for this purpose is in the shape of an ______________, similar to __________________.

end caps. O-ring. O-ring packings

The __________________ pump draws fluid through a standpipe in the reservoir and the _______________ pump draws fluid from the bottom of the reservoir.

engine driven. AC motor

This process is often called bleed air and is used to provide pneumatic power for what five things?

engine starts, engine deicing, wing deicing, and in some cases, it provides hydraulic power to the aircraft systems (if the hydraulic system is equipped with an air-driven hydraulic pump).

What should you do before disassembling any accumulator?

ensure that all preload air (or nitrogen) pressure has been discharged. Failure to release the preload could result in serious injury to the technician.

In terms of O-rings, the cross-section is truly round and has been molded and trimmed to ________________________.

extremely close tolerances

In terms of linear actuators, What happens to the piston with respect to the housing, when a double acting actuator EXTENDS?

fluid is admitted under pressure to the left-hand chamber of the actuating cylinder.

An actuating cylinder transforms energy in the form of_____________ into __________________, to perform work.

fluid pressure. mechanical force or action

The heat exchangers use aluminum finned tubes to transfer heat from the ______________ to the _____________.

fluid to the fuel

Describe Air Force-Navy (AN) Hydraulic O-rings.

for use in uid at operating temperatures ranging from -65 °F to +160 °F. When new designs raised operating temperatures to a possible +275 °F, more compounds were developed and perfecte

After the O-ring is placed in the cavity provided, what should you do?

gently roll the O-ring with the fingers to remove any twist that might have occurred during installation.

When selecting an O-ring for installation, what is the most reliable way to identify O-ring?

he basic part number on the sealed envelope provides the most reliable compound identi cation.

The hydraulic case drain fluid that lubricates and cools the pumps return to the reservoir through a _______________.

heat exchanger

In terms of Hydraulic Motors, Piston-type motors are basically the same as ___________________ except they are used to convert _________________ energy into_______________________ energy.

hydraulic pumps. hydraulic. mechanical (rotary).

O-Ring Installation: What should do after inspection and prior to O-ring installation?

immerse the O-ring in clean hydraulic fluid.

Liquids are practically ____________________

incompressible

How are O-rings Packaged? (2)

individual hermetically sealed envelopes labeled with all pertinent data.

Pneumatics System components, filters: Normally, air enters the___________, circulates around the cellulose cartridge, and flows to the ___________ of the cartridge and out the ____________ port.

inlet. center. outlet

What type of pressure are U-ring packings used in?

low pressures of less than 1000 psi

What must you check on a Teflon™ spiral back?

make sure that the coils do not separate more than 1⁄4 inch when unrestrained.

For high pressure systems, what is the air usually stored in?

metal bottles

Wipers may be either ______________ or ______________. They are sometimes used together, a felt wiper installed ____________ a metallic wiper.

metallic. felt. behind.

O-Ring Installation: If possible, keep the position of the O-ring's _________________ constant

mold line

How do you identify backup rings?

must be identifed from package labels.

For systems that use MIL-H-5606, what are the 2 materials the seals are made of?

neoprene or Buna-N

EMER LDG GEAR. Pulling the handle fully upward opens the outlet valve, releasing compressed ______________ into the landing gear extension system. Pushing the handle fully downward closes the outlet valve and allows any _____________ present in the emergency landing gear extension system to be vented overboard. Landing gear system is isolated from the remainder of the hydraulic system.

nitrogen. nitrogen.

Are Backup rings color coded?

no

Seals used for MIL-H-5606 hydraulic fluid are ___________________ with Skydrol.

not compatible

In terms of linear actuators, a three way control valve is normally used for controlling the operation of a ____________________

of a single-action actuating cylinder.

Describe Military Standard (MS) hydraulic O-rings.

offered improved low-temperature performance without sacrificing high- temperature performance. These O-rings are now standard for systems where the operating temperatures may vary from -65 °F to +275 °F.

V-ring packings are _________ seals and are always installed with the ___________ of the V facing the ______________.

one-way. open end. pressure

The U-ring and U-cup seals pressure in ____________ direction; therefore, the lip of the packings must face____________.

only one. toward the pressure

What is the disadvantages of a bottled air system that cannot be recharged during flight?

operation is limited by the small supply of bottled air. Such an arrangement cannot be used for the continuous operation of a system.

What are the three main classes that seals are divided into?

packings, gaskets and wipers.

On aircraft, what is installed to recharge air bottles whenever pressure is used for operating a unit?

permanently installed air compressors have been added to recharge air bottles

What does the positive pressure in the reservoir ensure?

positive flow of fluid to the pumps.

The PTU can only transfer __________ and cannot transfer_____________.

power. fluid.

Power Transfer Unit (PTU) The PTU is able to transfer ______________ but not_______________. It transfers power between two __________________. The two units, _____________________ and _________________, are connected via a single drive shaft so that _______ can be transferred between two systems.

power. fluid. hydraulic systems. hydraulic pump. hydraulic motor. power.

In terms of the operation of an accumulator: The compressed-air chamber is charged to a _______________________ pressure that is somewhat ________________ than the system operating pressure.

predetermined. lower

What is the purpose of the standpipe on the reservoirs?

prevents the loss of all hydraulic uid if a leak develops in the engine-driven pump or its related lines.

When the O-Ring installation requires spanning or inserting through sharply threaded areas, ridges, slots, and edges use ___________________, such as: (3)

protective measures

Pneumatic Power System Maintenance: The pneumatic system should be __________________ periodically to remove the contamination, moisture, or oil from the components and lines.

purged

Boeing 777 Hydraulic System: How is hydraulic power generated under emergency conditions?

ram air turbine (RAT), which is deployed automatically and drives a variable displacement inline pump. The RAT pump provides ow to the center system ight controls. [Figure 12-66]

Pneumatic Restrictors: The small outlet port reduces __________________ and the ________________ of an actuating unit.

rate of flow. speed.

Pneumatic systems do not utilize what five things?

reservoirs, hand pumps, accumulators, regulators, or engine-driven or electrically driven power pumps

What are two major types of Actuating cylinders?

single action and double action.

The low pressure pump delivers to the pneumatic sysyem a continues supply of compressed air from ______________ to _________ psi

1 - 10

What pressure ranges in considers high pressure systems?

1,000 to 3,000 psi,

Pneumatic systems are sometimes used for: (4)

1. Brakes 2. Opening and closing doors. 3. driving hydraulics pumps, alternators, starters, water infection pumps eat. Operating emergency devices

What three types of filters are in the 777 hydraulic system?

1. Pressure filter module 2. Case drain filter module 3. return filter module

What are wipers used for? (3)

1. Wipers are used to clean and lubricate the exposed portions of piston shafts. 2. They prevent dirt from entering the system and 3. help protect the piston shaft against scoring.

Boeing 777 Hydraulic System: What indications are sent to the flight deck? (3)

1. pressure, 2. temperature, 3. quantity signals to the ight deck.

The boeing 737 next generation has three __________ psi hydraulic systems: system ___________, system____________ and _______________. The standby system is used if ____________________________.

3000. A. B. standby. system A and/or B pressure is lost.

Such flaws are difficult to detect, and one aircraft manufacture recommend using a ________________ magnifying glass with adequate _________ to inspect each ring before it is installed.

4 power (5 minimum in nz). lighting.

What are the 2 valves found on a high pressure air bottle?

A ground-operated compressor can be connected to this valve to add air to the bottle. The other valve is a control valve. It acts as a shutoff valve, keeping air trapped inside the bottle until the system is operated.

What pressures are are considered a medium-pressure pneumatic system?

A medium-pressure pneumatic system (50-150 psi) usually does not include an air bottle.

Boeing 777 Hydraulic System: What protects the EDP filter module against over pressurization?

A pressure relief valve

Pneumatics System components, filters: Describe a screen type filter.

A screen-type lter is similar to the micron lter but contains a permanent wire screen instead of a replaceable cartridge.

Be certain that backup rings are installed ____________ of the O-Ring.

Downstream

Both A and B hydraulic systems have an _______________ and an ______________________.

Engine driven pump. AC motor pump (ACMP)

What type of valve is installed on the nitrogen side of the accumulator?

Gas Servicing Valve

Describe a Gasket?

Gaskets are used as static (stationary) seals between two at surfaces.

Describe gaskets.

Hydraulic seals used between nonmoving ttings and bosses are normally called gaskets.

Describe packings:

Hydraulic seals used internally on a sliding or moving assembly are normally called packings.

Pneumatics System components, What happens if the cartridge in the chemical drier is any other color than it should be?

If otherwise noted, the cartridge is to be considered contaminated with moisture and should be replaced.

Pneumatics System components, filters: What is the purpose of the handle in the screen filter?

In the screen filter, a handle extends through the top of the housing and can be used to clean the screen by rotating it against metal scrapers.

Medium-Pressure Systems do not usually include an air bottle, so where does it generally draw air from?

Instead, it generally draws air from the compressor section of a turbine engine.

Reservoirs: Pressure switches, located in the EDP and ACMP pump output lines, send signals to illuminate the related __________________ light if the pump output pressure is low.

LOW PRESSURE

How is purging the system accomplished?

Purging the system is accomplished by pressurizing it and removing the plumbing from various components throughout the system.

Hydraulic Motor-Driven Generator (HMDG) What is a HMDG?

The HMDG is a servo-controlled variable displacement motor integrated with an AC generator. In case of an electrical failure, the HMDG could provide an alternative source of electrical power.

What does the PTU consist of? (2)

The PTU unit consists of a hydraulic motor and hydraulic pump that are connected through a shaft.

What is Pneudralics?

The nitrogen is not directly used to actuate the landing gear actuators or brake units but, instead, it applies the pressurized nitrogen to move hydraulic uid to the actuator.

How are reservoirs pressurized?

The reservoirs are pressurized by bleed air through a pressurization module.

What do Backup rings dash numbers indicate?

Their dash numbers indicate not only their size but also relate directly to the dash number of the O-ring for which they are dimensionally suited.

What must the fuel in the tanks, that contain the heat exchangers be maintained at?

They msg be maintained at a specific level to ensure adequate cooling of the fluid.

The function of an accumulator is to... (4)

• Dampen pressure surges in the hydraulic system caused by actuation of a unit and the effort of the pump to maintain pressure at a preset level. • Aid or supplement the power pump when several units are operating at once by supplying extra power from its accumulated, or stored, power. • Store power for the limited operation of a hydraulic unit when the pump is not operating. • Supply uid under pressure to compensate for small internal or external (not desired) leaks that would cause the system to cycle continuously by action of the pressure switches continually kicking in.