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021 03 01 00 Hydromechanics: basic principles
021 03 01 01 Concepts and basic principles
(01) X Explain the concept and basic principles of hydromechanics
Syllabus reference BK Syllabus details and associated Learning Objectives
“including:
— hydrostatic pressure;
— Pascal’s law;
— the relationship between pressure, force and area;
— transmission of power: multiplication of force, decrease of displacement.”
021 03 02 00 Hydraulic systems
021 03 02 01 Hydraulic fluids: types, characteristics, limitations
(01) X “List and explain the desirable properties of a hydraulic fluid with regard to:
— thermal stability;
— corrosiveness;
— flashpoint and flammability;
— volatility;
— viscosity.”
(02) X State that hydraulic fluids are irritating to skin and eyes.
(03) “List the two different types of hydraulic fluids:
— synthetic;
— mineral.”
(04) State that different types of hydraulic fluids cannot be mixed.
(05) X State that at the pressures being considered, hydraulic fluid is considered incompressible.
021 03 02 02 System components: design, operation, degraded modes of operation, indications and warnings
Syllabus reference BK Syllabus details and associated Learning Objectives
(01) Explain the working principle of a hydraulic system.
(02) Describe the difference in the principle of operation between a constant pressure system and a system pressurised only on specific demand.
(03) State the differences in the principle of operation between a passive hydraulic system (without a pressure pump) and an active hydraulic system (with a pressure pump).
(04) X “List the main advantages and disadvantages of system actuation by hydraulic or purely mechanical means with respect to:
— weight;
— size;
— force.”
(05) List the main uses of hydraulic systems.
(06) State that hydraulic systems can be classified as either high pressure (typically 3000 psi or higher) or low pressure (typically up to 2000 psi).
(07) State that a high-pressure hydraulic system is typically operating at 3000 psi but on some aircraft a hydraulic pressure of 4000 to 5000 psi may also be used.
(08) Explain the working principle of a low-pressure (0–2000 psi) system.
(09) Explain the advantages and disadvantages of a high-pressure system over a low-pressure system.
(10) “Describe the working principle and functions of pressure pumps including:
— constant pressure pump (swash plate or cam plate);”
Syllabus reference BK Syllabus details and associated Learning Objectives
— pressure pump whose output is dependent on pump revolutions per minute (rpm) (gear type).
(11) “Explain the following different sources of hydraulic pressure, their typical application and potential operational limitations:
— manual;
— engine gearbox;
— electrical;
— air (pneumatic and ram-air turbine);
— hydraulic (power transfer unit) or reversible motor pumps;
— accessory.”
(12) “Explain the following different sources of hydraulic pressure, their typical application and potential operational limitations:
— manual;
— engine;
— gearbox;
— electrical.”
(13) “Describe the working principle and functions of the following hydraulic system components:
— reservoir (pressurised and unpressurised);
— accumulators;
— case drain lines and fluid cooler return lines;
— piston actuators (single- and double-acting);
— hydraulic motors;
— filters;
— non-return (check) valves;
— relief valves;”
Syllabus reference BK Syllabus details and associated Learning Objectives
“— restrictor valves;
— elector valves (linear and basic rotary selectors, two and four ports);
— bypass valves;
— shuttle valves;
— fire shut-off valves;
— priority valves;
— fuse valves;
— pressure and return pipes.”
(14) Explain the function of the demand pump installed on many transport aeroplanes.
(15) Explain how redundancy is obtained by giving examples.
(16) Interpret a typical hydraulic system schematic to the level of detail as found in an aircraft flight crew operating manual (FCOM).
(17) Explain the implication of a high system demand.
(18) List and describe the instruments and alerts for monitoring a hydraulic system.
(19) “State the indications and explain the implications of the following malfunctions:
— system leak or low level;
— low pressure;
— high temperature.”