Chp 3 ( Engine Controls) Flashcards
What are typical controls found on a helicopter Gas Turbine Engine?
HP Cock, Throttle (Fuel Control Unit), Centrifugal Governor.
What is the function of the HP Cock?
It allows fuel to enter the combustion chamber and must be opened for operation.
How is the HP Cock operated?
The pilot operates the valve using a lever or switch in the cockpit.
Is the HP Cock a throttle?
No, it is not a throttle and must be rigged to avoid fuel restriction.
What does the throttle (Fuel Control Unit) control?
It controls the speed of the engine from Ground Idle to Flight Idle.
What is the role of the Centrifugal Governor?
It monitors and maintains the engine RPM set by the Throttle and prevents engine overspeeding.
What were traditional control systems comprised of?
Different types of cable loops connected to rods, pulleys, and levers, rigged to fixed stops.
What are the types of control cables?
Bowden cables, typically used for lightly loaded components in the pull mode.
What is Teleflex?
Teleflex is a cable system that has an inner cable and outer conduit. The cable features an inner core with a wire helix wrapped around it and operates in both tension and compression, allowing it to push and pull levers. The system is lubricated.
What is Bowdenflex?
Bowdenflex is a type of cable that can withstand both compression and tension. It has a flat rod running on bearings and can withstand heat without lubrication.
A Bowdenflex cable has an ‘O’ and ‘|’ stamped on the end, indicating the Outside and Inside of the radius used when the cable routing requires a bend.
What must control runs be free from?
Control runs must be free from restrictions. Lubrication must be carried out as required according to the relevant publication.
What should be ensured to prevent fuel restrictions?
Control runs should be correctly rigged to ensure fuel restrictions do not occur and to ensure correct throttle operation.
When should rigging be carried out?
Rigging must be carried out in accordance with the relevant Aircraft Publication when a component has been changed or disturbed.
What can wear on control stops cause?
Wear on control stops (also called Undercutting) can cause incorrect rigging and chattering of controls.
What is a visual indication of milling on control stops?
A visual indication of milling could be a ‘step’ in the surface of the stop.
What should be checked before signing off on control work?
Before signing off on any work, exercise the controls to check that they move freely and easily, and in the correct direction(s).
What should be done after maintenance that disturbs the HP Cock?
A leak check should be carried out following any maintenance activity that disturbs the HP Cock.
Who must carry out an independent check after maintenance on control systems?
An independent check must be carried out by an authorised person who has had nothing to do with the task.
What are newer aircraft increasingly replacing in control systems?
Newer aircraft are increasingly replacing FCU, Governor, and other types of controls with fully electronic systems via the EEC (Electronic Engine Control) and FADEC.
What does the cockpit interface typically resemble in modern systems?
Whether electronic or mechanical in operation, the cockpit interface still tends to be in the form of a lever.
