Rotor System, Contol System, XMSN Flashcards
What is the route of the mechanical flight controls (pilot input to main rotor)
Controls (cyclic, collective, pedals) ➡️ force-axis combined in overhead torque shaft (hyds bay) ➡️ pilot assist servos (PAS) ➡️ mixing unit (MU) ➡️ fwd, aft, lateral primary hydraulic servos ➡️ control rods ➡️ swashplate assembly ➡️ rotating swashplate ➡️ pitch control rods ➡️ pitch change horns
What is the mechanical route from the pilot control input to the tail rotor (mechanical flight control system)
Controls ➡️ force- axis combined in overhead torque shaft (hyds bay) ➡️ pilot assist servis (PAS) ➡️ mixing unit (MU) ➡️ tail rotor servo ➡️ tail rotor quadrant cables ➡️tail rotor
Main rotor
- 4 bladed
- CCW
- fully articulated
- 53’8” diameter
How are the rotor blades attached to the hub?
Via spindle assemblies and are retained via elastomeric bearings
What is on each spindle?
- blade lock-pin puller
- fold hinge
- blade fold actuator
- pitch lock actuator
- putch change horns (connected to pitch control rods)
What do blade lock-pin pullers look like and what do they do?
- “2 nips chained together”
- locks blades OUT so they don’t fold back
What does the fold hinge look like and what does it do?
- hinge on the “top face of the lollipop”
- blade rotates here when being folded
What absorbs vibrations on top of the rotor head?
What do you check on this during pre-flight?
Bipolar vibration absorber
Check that it is free to move and greased up
What does the swashplate assembly comprised of?
A stationary and rotating disc separated by a bearing. The outer disc (rotating swashplate) is what rotates around the rotar shaft,tilting about the teflon-coated uniball
What are main rotor dampers supplied with? What psi are they charged to?
Nitrogen-pressurised hydraulic fluid
1200 psi, you check charge and fluid level on pre-flight
Where are main rotor dampers located and what do they do?
They are mounted between each spindle assembly to absorb rotor hub sharing loads and restrain lead/lag
Tail rotor drive shaft is made up of?
- 6 sections, balistically hardened
- connected by Thomas couplings before the IGB
- connected together by 4 viscous damper bearings
When you increase collective, which direction does the nose yaw?
Right
When you decrease collective, which way does the nose yaw?
Left
What does the AVCS system do?
It reduces the duration of peak vibratory loads produced by the main rotor
(Meaning it reduces vibrations from main rotor)
Main rotoe causes what kind of vibrations?
4 per revolution
What other sensor does the AVCS system use?
It uses the Nr sensor as a reference signal to track rotor speed
What isnthe AVCS system made up of?
- AVC Computer (AVCC)
- 10 feedback accelerometer sensors (8 vertical and 2 lateral)
- Vibration Control Augmentation System (VCAS)
What does the AVCC do?
Determines frequency, magnitude, and phase required to reduce aircraft vibrations
What does the 10 feedback accelerometer sensors do?
- 8 vertical
- 2 lateral
- Provide vibration information to AVCC
- provides feedback as it senses vibrations the AVCC triggers
What is the VCAS?
-Vibration Control Actuation System
- 1 Electronics unit
- 5 Force Generators
What does the VCAS do?
-Force Generators rotate weighted wheels at a rate of 180° out of phase with the helicopter vibrations (as commanded bg the electronic unit)
What are the Force Generators
- part of VCAS system
- near the nose
- 5 pairs total (4 pairs of 1000#, 1 pair of 500#)
Flow schematic of the AVCS system
Accelerometers sense vibrations
➡️ AVCC computer
➡️ AVCC computes “counter vibes”
➡️ Electronic unit actuates the force Generators
➡️force generators shake/rotate to produce counter vibes
When should extended AVCS use be avoided and why?
- on deck
- AVCS system analysis cycle resets every 5 minutes (300 seconds) which may cause an erroneous AVCs input
When can you test the AVCS?
AVCS IBIT shall only be initiated with rotors static to avoid damage to dynamic components
Flying in “utility mode” what do you lose? What types of missions can you still fly?
- ISAR and ARPDD radar modes
- ESM
- dipping sonar
- ARC-210 presets
- accoustic processing
- ASE system
- missile and torpedo employment
- data fusion
- onboard map
-you can still fly local pattern, cross country, ferry, logistics, MEDEVAC, and VERTREP flights
What does a damper failure consist of?
It causes a dynamically imbalanced rotor condition, with low-frequency lateral or vertical vibrations (1-3p), where magnitude may increase over time
Loss of tail/rotor authority/effectiveness is when?
Authority = Power required > Power available
Effectiveness = wind direction / environmental
Weather vaning
120°-240° (tail wind)
Reduction/Loss of AOA
60°-120° (right crosswind)
Tail rotor VRS
210°-330° (left crosswind)
Main rotor VRS interaction
280°-330° (Left headwind)
Or
030°-080° (right headwind)
How do youbrecover from loss of tail rotor authority or effectiveness?
- Lower collective
- Fwd cyclic
- Full left pedals (at low air speeds)5$
How much oil is in main xmsn?
7.5 US gallons
What type of oil is used for xmsn system?
DOD-PRF-85734
How much xman oil is in IGB and TGB?
2.75 US pints
When do you check main xmsn oil?
-30 minutes after shutdown or later
- hot scale used 30mins-2hrs after shutdown
- cold scale used 2+ hrs after shutdown
If xmsn oil is down to ADD line on oil dipstick, how much do you need to add?
2 quarts
Where is main xmsn oil dipstick and filler port located?
Right rear of main module
Whre is the IGB oil level sight gauge?
Left side of gear box
- if equipped with bullseye sight gage, gearbox is full with pylon spread and oil within inner circle
- replenish if bottom outer circle can be seen
Where is the TGB oil sight gauge? Servicing guidelines?
Right side of gearbox
Contains red upper and lower limit line
Green areas on either side of gauge also delineate servicing limits
Is properly serviced when oil level is within thr lines/green area with pylon spread (replenish if oil level is below lower line)
