Tail Rotor Flashcards
Provides directional control by
varying pitch of TR blades
TR is __ actuated, but requires __ to operate the pitch change shaft, which moves the ___, changing blade pitch angle through ___
mechanically; hydraulic pressure; pitch change beam; pitch change links
TR quadrant transmits TR cable movement to the
TR servo
__ connected to the quadrant allow cable tension to be maintained if either TR cable becomes severed
2 spring cylinders
if both cables are severed, __ will counter TR servo pilot valve to position TR to neutral for fly home capability
2 separate centering springs
positions pedals
Describe the TR
bearingless, crossbeam TR blade system
TR flexible spar allows
tail rotor blade flap and pitch change
Blades are canted
20 degrees upward
TR provides __ % of lift in a hover which helps __
2.5; lower nose attitude in hover because the TR is aft of the aircraft CG
TR indexing system
positions blades during pylon folding and prevents TR from windmilling in winds up to 60 knots when tail folded
Describe TR blades
built around 2 composite spars to form 4 blades
Nose snap with loss of drive is less noticeable at __ airspeeds
faster
Indication of functioning TR when attempting to verify drive failur
application of right pedal brings nose right
3 types of TR Control Malfunctions
- Cable failure
- Servo failure
- Restricted flight controls
Cable failure indications
TR QUADRANT light
Cable failure airspeeds for GW 19,500 lbs
25 AND 145 KIAS
Cable failure below/above 25/145; between 25/145
Nose yaws right; nose yaws left
TR Servo Failure indications
Lose No 1 Hyd Pump and Backup Pump; retain boost and mechanical system
TR Servo Airspeeds
40 TO 120
Servo Failure Recommended Landing
Running landing above 40 KIAS
Restricted Flight Control Scenarios
FOD, mechanical failure, servo hardover
Hardover failure can put __ lbs of force on pedals
250 lbs
Stuck left
high power setting; normal landing
Stuck right
low power setting, running landing/auto
LTE
inability of TR to provide sufficient force to maintain yaw controllability
LTE occurs when
full pedal input is insufficient to provide directional control
Tail rotor thrust is a function of
operating rpm and tail rotor AOA
Two primary directional control mechanisms of TR
AOA and weather vaning tendency of fuselage
LTE and winds from the right
- winds from right decrease AOA of TR, reducing effectiveness and requiring additional left pedal to maintain heading
- additional left pedal depletes main rotor power and reduces directional control authority
- so, in high power, right crosswind situations, may lose TR effectiveness
LTE and winds from the left
- winds from left increase AOA of TR –> increase TR AOA –> increase in TR effectiveness
- if left wind excessive, disturbed airflow around TR may develop, resulting in loss of effectiveness
Weather Vaning
winds in 120 to 240 region
nose will weathervane into wind
TR VRS
- 210 to 330
- can cause TR to operate within its own recirculated airflow
- causes TR thrust variations that can initiate yaw rates
- if right yaw builds from this, may get into weather vaning and see yaw rate accelerate
Main Rotor Disc Vortex Interaction
- 280 to 330, less frequently 30 to 80
can cause main rotor vortex to be directed onto TR, resulting in changes of AOA to TR - TR thrust can vary unpredictably
Loss of TL
- results in increased power demand and additional anti-torque requirements
- if occurs in right turn, right turn will be accelerated; if near max power available –> Nr decay
- can be caused by insufficient attention to wind direction and velocity
Right sideward flight and LTE
same effect as right crosswind
Factors increasing likelihood of LTE
high gross weight, high DA, arresting high descent rate
Recovering from LTE
- Lower collective to reduce tq/arrest right yaw (if too high of descent rate, arresting descent may reinitiate LTE)
- Forward cyclic to increase airspeed, and if necessary, turning in direction of rotation (causes reduction in TR thrust req and produces streamlining effect)
- At low speeds/hover, full left pedal may stop right yaw (may take a few seconds/rotations to work). Neutralizing pedals or adding right pedal will only accelerate yaw rate
Spring tension feature
with loss of both cables, provides positive pitch on TR equivalent to the antitorque requirements (left pedal) for a midposition collective setting
