AMT2104: HELICOPTER OPERATION AND MAINTENANCE - Midterms

CYCLIC 

Located between the pilot’s legs 

Commonly called cyclic stick or cyclic

Similar to joystick

Robinson helicopters

have unique T-bar cyclic control system 

To tilt the rotor disk in a particular direction

It vary the pitch of the rotor blades throughout each revolution of the main rotor system

COLLECTIVE 

Located on the left side of pilot’s seat

Changes the pitch angle of all the main rotor blades 

All the blades change equally 

THROTTLE 

To maintain enough engine power to keep the rotor rpm within allowable limits to produce enough lift 

ANTI-TORQUE PEDALS 

Located in the same position as the rudder pedals 

Given direction changes the pitch of the tail rotor blades 

HOVERING FLIGHT 

Used to eliminate drift in the horizontal plane 

Used to maintain altitude 

Pedals are used to control nose direction or heading 

Most challenging part of flying a helicopter  

SIDEWARD FLIGHT 

Tip-path plane is tilted in the direction that flight is desired 

Can be very unstable condition due to parasitic drag 

FORWARD FLIGHT

 

Once the tip-path plane is tilted forward, the total lift-thrust force is also tilted forward 

REARWARD FLIGHT 

Tip-path plane is tilted rearward, which in turn tilts the lift-thurst vector rearward

 

TURNING FLIGHT

When the helicopter is banked, the rotor disk is tilted sideward resulting in lift being separated into two components

VERTICAL FLIGHT 

Increasing the angle of incidence of the rotor blades (pitch) while keeping their rotation speed constant generates additional lift and the helicopter ascends.

HELICOPTER ROTOR SYSTEM

 

rotating part of a helicopter that generates lift. 

Mounted horizontally and vertically 

ROTOR MAST

- hallow cylindrical metal shaft and sometimes supported by the transmission 

ROTOR HUB

- at the top mast is the attachment point for the rotor blades 

ROTOR BLADES

- long airfoil that considered as the rotating wing 

BLADE TWIST

- to alleviate internal blade stress and distribute the lifting force

TIP

- farthest outboard section

ROOT

- inner end of the blade and is the point attaches to the hub

TWIST

- change in blade incidence from the root to the outer blade 

BLADE PITCH HORNS

- to serve as lever, decreasing force it takes to change the blade angle 

PITCH CHANGE LINKAGES

- can be adjusted to set the angle of incidence of the blade during tracking and balance 

SWASH PLATE

- device or mechanism that translates the input controls into motion of main rotor blades

RIGID

- mechanically simple but structurally complex bc operating load must be absorbed in bending rather than though hinges 

Adv: simple design, crisp response 

Disadv: higher vibration than articulated rotor 

SEMI-RIGID

- composed of two blades that are rigidly mounted to the main rotor hub 

Teetering hinge - called to the free to tilt with respect to the main rotor shaft 

Adv: simple, easy to hangar

Disadv: reaction to control input not as quick 

FULLY ARTICULATED

- allow each blade to lead/lag, flap independent of the other blades 

Found on helicopters with more than 2 main rotor blades 

Adv: good control response

Disadv: high aerodynamic drag, more complex, greater cost 

TRANSMISSION SYSTEM

- transfers power from the engine to the main, tail and other accessories 

MAIN ROTOR TRANSMISSION

 to reduce engine output rpm to optimum rotor rpm 

TAIL ROTOR DRIVE SYSTEM

essential components of helicopter 

Designed to counteract the torque produced by the main rotor 

CLUTCH 

allows the engine to be started and then gradually pick up the load of the rotor 

BELT-DRIVE CLUTCH

-  to transmit power from the engine to the transmission 

consists of a lower pulley attached to the engine, an upper pulley attached to the transmission input shaft 

CENTRIFUGAL CLUTCH

- made up of an inner assembly and an outer drum 

FREEWHEELING UNIT 

Automatically disengages the engine from the main rotor when engine rpm is less than main rotor rpm 

TAIL ROTOR SYSTEM 

used to eliminate torque produced by the main rotor system 

ANTI-TORQUE SYSTEM

- typically supplies a thrust at the tail of the aircraft 

TAIL ROTOR

- smaller rotor mounted vertically or near vertically on the tail of traditional single rotor heli 

FENESTRON (FAN-IN-TAIL)

- a series of rotating blades shrouded within a vertical tail. 

common term used to describe the fan-in-tail rotor 

 

NOTAR (NO-TAIL-ROTOR)

- provides safe, quiet, responsive, FOD resistance directional control 

Piston Engine

- widely used on smaller types of helicopter 

Turbine engines

- more powerful and used in a wide variety of heli

Tachometer

- used to show both engine and rotor rpm or percentage of engine and rotor rpm