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Airframe Rotors > Vibration Analysis > Flashcards

Vibration Analysis Flashcards

1
Q

What are the two types of vibration

Describe them

A

Lateral and vertical

Lateral vibrations are caused by the main rotor being spanwise out of balance

Vertical vibrations are caused by a main rotor being out of track, sweep or having different flight characteristics

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2
Q

Which is done first lateral or vertical balancing

A

Lateral balance must be perfect prior to moving on to vertical balancing

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3
Q

What is the purpose of the spring mounting on the aircraft battery

A

The battery is attached to spring mounting and acts as a resonant vibrating mass to absorb vibration from the main rotor blades

It is mechanically tuned by adding or subtracting weights

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4
Q

When removing the CMRB from the retention is it considered normal for a loud bang to be heard?

A

Yes, hydraulic pressure from the removal kit overcomes the friction of the seating on the morse taper.

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5
Q

What is the technique used to torque the lead-lag pin?

A

Stretch torquing. More accurate.

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6
Q

. List the functions of the main rotor dampers.

A

Limit lead-lag travel, maintain smooth lead-lag operation and absorb blade shock on startup/ shutdown.

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7
Q

Under what circumstances would you carry out a main rotor damper check?

A

When the pilot feels a 1R vibe or excessive ground wallow

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8
Q

How to you check a main rotor damper.

A

Comparative maintenance between all blades by monitoring each gauge and lead/lagging the blade with the rotor break on.

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9
Q

Why are the tail rotor blades set to a positive angle, as opposed to 0.

A

A positive blade angle is to counter rotational torque from the Main rotor.

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10
Q

On the retention assembly which components are installed to keep the blades in a safe and neutral position?

A

Droop stops, Pitch lock.

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11
Q

In the operational checkout procedure for the flight control system there is a requirement for a azimuth phasing check. Why is this check carried out?

A

To ensure the azimuth was correctly installed and rigged.

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12
Q

What component in the flight control system allows for gyroscopic procession?

A

90 degree lag of the azimuth rods. (Tower rods)

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13
Q

Describe the construction of the CMRB.

A

Nickel leading edge and tip cap, Fiberglass composite spar with a nomex honeycomb core and graphite trailing edge.

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14
Q

What are the 2 conditions can the blade tracking system remove to improve the main rotor track and vibration?

A

One-per-rev and Split cone conditions.

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15
Q

The pilots sign the aircraft in with a 1R vibe. Upon inspection you find that B blade tracking motor is buried in the red. What action would you take.

A

Double check tracking motor authority, shorten the chordwise rod IAW pubs and re centre the tracking motors.

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16
Q

What is required for the blade tracking system to operate in automatic mode?

A

Weight off wheels

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17
Q

Name the tracking motors that operate when the pilot is trying to remove a split cone.

A

B & D.

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18
Q

. What blade tracking motors are used in auto mode?

A

C and d

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19
Q

What’s the difference between the collective damper assy and the collective bungee?

A

Damper = ensures slow operation of the collective downwards (and upwards) movement.
Bungee = Spring forces to counteract the centrifugal forces acting on the spanwise rods.

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20
Q

What are the locations for primary stops?

A

Cyclic = Base of the yoke
Collective = Cantered bulkhead
Directional controls = Pilots input crank

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21
Q
  1. What is the location of secondary stops?
A

Cyclic = Idler
Collective = Idler
Directional = Upper tunnel control pulley.

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22
Q

With the aircraft sat on the group running in idle, is it a fault if the collective starts to rise?

A

No, if it can be overcome by slight downwards pressure.

23
Q

What components transfer the drive from the main rotor shaft to the azimuth assembly?

A

Spindle and spindle support.

24
Q

What component stops the outer half of the azimuth from rotating?

A

Azimuth link

25
Q

What are the four mechanical control inputs into the AFCS pack?

A

Lateral, Longitudinal, Directional and collective.

26
Q

Does the FCC provide input into the flight controls via the AFCS servo actuators

A

Yes

27
Q

Does the FCC receive inputs from the INS & GPS?

A

Yes

28
Q

Is the FCC located in the LH nose door?

A

No rh side

29
Q

W hat is the purpose of the collective friction brake?

A

To simulate desired “Feel” for the pilot.

30
Q

Does the FCC have authority over the friction brake system?

A

Yes. (Alt hold disables it)

31
Q

What’s the purpose of the AFCS actuator bobweight assembly

A

Counteracts flapback.

32
Q

What is the purpose of the locking springs found in the AFCS pack Boost valve and AFCS actuators?

A

To return the system to a neutral position when boost is off and acts as a failsafe when hydraulics are lost.

33
Q

What are the 3 modes of function of the AFCS actuator?

A

Manual, Boost and Auto.

34
Q

Name the 2 controls the pilot can use to close the PRSOV and ECS and isolate bleed air from the aircon pack.

A

Emergency and ECS off.

35
Q
  1. With the ECS acting in auto and the cabin temp was to increase, what would be the effect on the torque dual motor valve?
A

It would close bleed air and provide more conditioned, cold air.

36
Q

Should the aft avionics compartment overheat, what indication would you see?

A

Boot temp high warning light

37
Q

What components work to achieve a cabin temp set by the pilot on the ECS control panel?

A

Duct temp sensor, Cockpit zone temp sensor, Digital temp controller & dual torque motor valves.

38
Q

In the event of ditching how would the helicopter stat afloat?

A

Float bags, Aux tanks & tail boom.

39
Q

Describe what happens when the helicopter ditches in salt water?

A

When 2 salt water immersion sensors (One front and one back) are submerged in salt water float bags will deploy.

40
Q

. Is it possible for the BAU to deploy with the floatation system?

A

Yes

41
Q

When would this occur?

A

When float bags are in automatic mode.

42
Q

When float bags are deployed, what releases the helium?

A

Cad’s

43
Q

Name the different methods of releasing the cargo hook.

A

Electrically (Cyclic button), emergency jettison handle and externally.

44
Q

What is the maximum load the cargo hook can carry?

A

4000lbs

45
Q

Whats the maximum weight limitation?

A

Aircraft weight limitations are normally much lower.

46
Q

What is the construction of the floor panels?

A

Aluminium sheet sandwiching aluminium foil honeycomb

47
Q

Can the aircraft be jacked without the floor panels installed?

A

No

48
Q

What is the aircraft fuselage construction?

A

Semi-monocoque, consisting of bulkheads, frames, strings etc.

49
Q

What’s the purpose of the troop-seat energy absorber?

A

To reduce forces on personnel during crashes and reduce bodily harm.

50
Q

How do the troop-seat energy absorbers work?

A

Wire forced through a bolt matrix causing friction.

51
Q

What precaution needs to be taken when working around the W-struts?

A

Strut protective padding.

52
Q

In general terms, what are the 2 main types of rotor induced vibration?

A

Later = Blade out of balance.
Vertical = Blades out of track.

53
Q

What passive system is used to reduce 4R vibration?

A

Battery shock absorbers.

54
Q

What principle does this system use?

A

Resonance

Airframe Rotors (6 decks)

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