Flight Control Sysytem

Question 1

The flight control system can be divided into three sections:

Answer 1

1. Mechanical control system.
2. Flight control servo system.
3. Automatic flight control system.

Question 2

How are control inputs routed to the control surfaces (rotor and tail rotor)

Answer 2

The cyclic, collective, and tail rotor pedal flight controls are routed aft and outboard of each pilot seat, vertically up each side of the aircraft, and are combined for each axis at the overhead torque shafts inside the hydraulics bay. The overhead torque shafts transfer inputs from the trim servos and flight controls through the pilot assist servos and the mixing unit. From the mixing unit, fore, aft, and lateral inputs are transferred to the swashplate assembly via the primary servos and the bridge assembly. The yaw inputs to the tail rotor servo are transferred from the mixing unit aft to the tail rotor quadrant through the tail rotor cables.

Controls/trim servos->outboard and up to the overhead torque shafts->pilot assist servos & mixing unit->primary servos->bridge assembly-swashplate

Question 3

How does the tail rotor servo work? How is pitch changed?

Answer 3

The tail rotor servo is mechanically actuated, but requires hydraulic pressure to operate the pitch change shaft, which moves the tail rotor pitch change beam, changing blade pitch angle through the pitch-change links.

Question 4

___________ connected to the quadrant allow cable tension to be maintained if either tail rotor cable becomes severed.

Answer 4

Two spring cylinders

Question 5

If both cables are severed, __________ will counter the _____________ positioning the tail rotor to a neutral setting to provide a fly-home capability.

Answer 5

Two separate centering springs, tail rotor servo pilot valve

Question 6

Should one primary servo stage become inoperative due to pressure loss or a jammed input pilot valve,_______________________, and the #1/#2 PRI SERVO PRESS caution will appear.

Answer 6

a bypass valve within the affected stage will automatically open

Question 7

What makes up the pilot assist servo assembly?

Answer 7

The pilot-assist servo assembly contains the boost servos, SAS actuators, and hydraulic (pitch and roll) trim actuators.

Question 8

What type of main rotor system do we have?

Answer 8

Fully articulated

Question 9

The four main rotor blades attach to _______ and are retained by_____________.

Answer 9

Hinged spindles, elastomeric bearings contained in the hub

Question 10

What do the elastomeric bearings allow the blade to do?

Answer 10

The elastomeric bearings per blade enable the blades to flap, lead, and lag and also permit the blade to move about its axis for pitch changes.

Question 11

What do the main rotor dampers do? And where are they installed?

Answer 11

Main rotor dampers are installed between each of the main rotor spindle modules and the hub to restrain lead and lag motions of the main rotor blades during rotation and to absorb rotor head starting loads.

Question 12

Each damper is supplied with ____________ from a reservoir mounted inside the main rotor shaft.

Answer 12

Nitrogen-pressurized hydraulic fluid

Question 13

What does the lower pressure plate do?

Answer 13

The lower pressure plate, in conjunction with the main shaft nut, secures the shaft extension to the main shaft. The lower pressure plate also provides an attachment for the swashplate assembly.

Question 14

The swashplate has ______ and ______ separated by a bearing.

Answer 14

Stationary and rotating discs

Question 15

How do flight control inputs go from the swashplate to the rotor?

Answer 15

It transmits flight control movement to the main rotor through four pitch control rods. The swashplate slides around the main rotor shaft and tilts in the direction of the flight controls on a Teflon-coated uniball. Four pitch control rods extend from the rotating swashplate to the pitch change horn on each spindle. The pitch control rods transmit all movement of the flight controls from the swashplate to the main rotor blades.

Swashplate->pitch control rods->pitch change horns on spindle->main rotor blades

Question 16

What do droop stops and flap restraints do?

Answer 16

The droop stops and flap restraints prevent extremely high or low blade flapping at low Nr .

Question 17

When do the anti flapping restraints get pulled out and what does this allow?

Answer 17

When the main rotor is at 35 percent Nr or greater, centrifugal force pulls the antiflapping restraints outward and holds them in position to permit flapping and coning of the blades.

Question 18

When do droops come out and when do they go in?

Answer 18

Centrifugal force pulls the droop stops out at approximately 70 percent Nr and permits increased vertical movement of the blade. On shutdown, droop stops will seat at approximately 50 percentr Nr.

Question 19

What makes up each main rotor blade?

Answer 19

Each blade has a pressurized hollow spar, honeycomb core, outer skin, abrasion strips, electrothermal deicing mats, and a removable swept back tip fairing.

Question 20

What degrees are the rotor blades swept back and what does that supply?

Answer 20

20 degrees, sound attenuation and increased rotor efficiency

Question 21

How does BIM work? (Blade inspection method)

Answer 21

The spar of the main rotor blade is pressurized with nitrogen. If the blade is damaged and the structural integrity of the spar is impaired, nitrogen will escape and cause the Blade Inspection Method (BIM ® ) pressure indicator to show a black, or unsafe, indication

Question 22

How is each rotor blade connected to the spindle outboard of the blade fold hinge?

Answer 22

Each rotor blade is connected to the spindle assembly outboard of the blade-fold hinge by means of a bolted flange.

Question 23

What does the TR indexing system do?

Answer 23

The tail rotor indexing system positions the tail rotor blades during pylon fold operations and prevents the tail rotor from windmilling in winds up to 60 knots with the tail in the folded position.

Question 24

Where is the TR quadrant and what does it do?

Answer 24

The tail rotor quadrant, mounted on the tail gearbox, transmits tail rotor cable movements into the tail rotor servo.

Question 25

Two spring cylinders are connected to the quadrant. In the event a cable is broken,____________. The related microswitch mounted on the quadrant will illuminate the TAIL ROTOR QUADRANT caution.

Answer 25

the quadrant will operate normally by controlling the remaining cable against spring tension

Question 26

What type of TR system and how does it work?

Answer 26

Bearingless crossbeam. The tail rotor blades are built around two composite spars, running from tip-to-tip and crossing each other at the center to form the four blades. The two spars are interchangeable and may be replaced individually. The blade spars are clamped between the two hubs by a retaining bolt.