Part One Flashcards
(117 cards)
1
Q
Types of main rotor heads
A
Fully articulated
Semi rigid
Rigid
2
Q
Semi rigid rotor head
A
Flapping hinges Replaced by flexible sections
Drag hinges replaced by flexible sleeves
3
Q
Main rotor additions
A
A lifting eye - attachment for lifting
Flapping stops
Droop stops
4
Q
Three types of hinges
A
Feathering hinge
Flapping hinge
Dragging hinge
5
Q
Types of dampers
A
Elastomeric damper
Hydraulic
6
Q
Main rotor blade sleeve (feathering). What does it do?
A
Allow the input of pitch control
7
Q
Main rotor blade sleeve contains
A
Pitch bearing
Tie bar
Damper support/attachment
8
Q
MRBS = main rotor blade sleeve
Purpose of a tie bar
A
Absorbs centrifugal loads generated by the rotating blade (strands of wire that can twist, wrapped around two bushes)
9
Q
Bush
A
Hard metal (washer) which is bonded to a resin so when you put a bolt through it doesn’t effect the fibres
10
Q
Purpose of MR blades
A
Produce lift
Has aerofoil sections
11
Q
Symmetrical aerofoil
A
No lift at 0 AoA
Advantage = small pitch changes
Little centre of pressure change
Twisting loads are reduced
12
Q
Non symmetrical aerofoil
A
Useful lift at 0 angles
Produces more lift than symmetrical
Disadvantage : large changes to centre of pressure
13
Q
How to distribute lift evenly over the blade
A
made with a built in twist (Washout)
Each blade is either tapered
14
Q
How to get higher forward speed
A
BERP blade
15
Q
How is a MRB constructed
A
SMART material -
glass reinforced plastic
carbon reinforced plastic
stainless steel and titanium
16
Q
Main areas of a MRB are:
A
Root end/attachment area
Centre section/ main lift area
Outboard section/tip
17
Q
Attachment pins and bushes
A
Provide an attachment point for the main rotor blade root end to the rotor hub
Secured by a blade attachment pin
18
Q
What can be used to fill the hole of the attachment pin
A
Balance weights
19
Q
What is doubler
A
On aircraft due to high stress
They are bonded and bolted to composite structure
They form the attachment to the blade sleeve
Spread the weight on the carbon fibre
20
Q
What is used to lead the attachment pin into the bush ?
A
Bullet adapter
21
Q
Bullet adapter
A
Makes sure damage is not inflicted to the bushes
Directs pin into the bush
22
Q
In some blade attachments, part of the spar composite material structure may be wrapped around two steel bushes
A steel fitting is attached to the blade root by two bolts passing through the steel bushes
A
Root end section
23
Q
What complete the electrical path from the root to the head
A
Bonding leads
24
Q
Reasons for bonding leads
A
Minimise damage
Prevent electro static charges
Reduce the electric shock hazard
25
What is the following made of :
Spar
Filling
Skin
Leading edge
Trailing edge
Composite materials
Honeycomb
Carbon or glass fibre
Stainless steel or titanium
Light honeycomb structure
26
What good Blade tip
Easily interchangeable
Adjustable balance weights
27
What is used for adjusting aerodynamic balancing
Trim tabs
28
Static wicks
Discharges static electricity build up
29
Blade identification
Colour coded
Unique serial number
30
Lift load path
(How the helicopter is lifted)
A. Main rotor blades
B. Main rotor head
C. Main rotor mast
D. Main rotor gearbox casing
E. Main rotor gearbox supports struts/beams
F. Airframe mountings
31
Vibration control devices
Mass main rotor head vibration absorber
Bifilar vibration absorber
32
Large mass
attached by stiff springs out of phase to the MRH centre line.
Forced vibration generated by aircraft will be cancelled out by the mass
Mass/spring main rotor head vibration absorber
33
Biflilar vibration absorber
Arm mounted to each blade
Pendulum weight attached by a pivot
Weights oscillate in opposition to any rotor vibration
Prevents vibration being transferred to the airframe
34
What does a Active vibration cancellation do
Sense incoming vibration and react to them
35
Purpose of tail rotor
counteract torque reaction
Moment about vertical axis (yaw)
36
Tail rotor types
Free
Shrouded (fenestron)
NOTAR
37
Free tail rotor
Limits service life due to stress
Danger to ground personnel
Only has flapping and feathering
38
Shrouded (fenestron)
Solution to disadvantages of free tail rotor
High speed ducted fan mounted In a cambered fin
Advantages:
Flapping hinges are not required
Light and less vulnerable to damage by loose objects
Less hazardous to personnel
Disadvantages:
Increase in weight
Requires more power
Increase in drag due to enclosure
Expensive
39
NOTAR
Has no tail rotor
Reduces noise
Production limit
40
Tail rotor blade construction
Composite materials
Also has :
Erosion shield - protects blade leading edge
Blade tip - sometimes includes a cap, bonded to the blade
Balance weights can be installed on bolts
41
What must you do with Lubrication
Must be checked and serviced
42
Rotor blade maintenance
(What you are looking for)
Dents
Cracks
Distortion
Erosion
Surface finish
Correct attachment of components
Bearing wear
Damage to trim tabs and blade tips (tip strikes)
Balancing
43
Swash plate
Rotating star - The upper section connected to rotor shaft by scissor link so that it rotates at the same speed.
Tilting this alters blade pitch
This also has a ball joint so it can be tilted in any direction.
Non rotating star - lower section is mounted on the rotating star by bearings and is kept stationary by a scissor link connecting to the main gearbox
Control rods are connected to this star
44
Cyclic and collective rods are combined in what?
Mixing unit
45
Spider system parts
Spindle: big pole in the middle that spins passes input through mast
Ball joint provides pivot for the spindle
Dangle berry (bearing) is the bit at the bottom the the rods connect to ( oil filled)
46
What is used to replenish oil in bearing in the spider
Replenishment nipples
Oil guns
47
Main rotor pitch vernier
Used to indicate the pitch angle of each rotor blade
Permanently fixed to MRH blade sleeves
48
Basic spider assembly
Control passes through centre of mast MRGB
Changes angles of MRB’s
Tilts for cyclic
Whole assembly raises and lowers for collective
49
How is Trim controlled
Operated by pressing a single button on the cyclic.
This removes forces while these are moved to a new position.
When button is released the force is re established with new location (new datum)
50
How is trim control achieved
Electrically controlled trim actuators
51
Control rods system consist of what components
Rods/tubes
Bell cranks
Torque tubes
Control stops
Idler links
52
What does a control rod do ?
Transmits movement between two points
53
Control rod types
Fixed length
Adjustable length
54
Control rods have a left hand thread and right hand thread what happens?
It extends or retracts the length of the rod
To ensure they remain at there set length they are locked with a locknut
55
What is locking wire and tab washers ?
Types of wire locking
56
What is the control action generally free from ?
Backlash
57
How can you tell if enough thread is screwed into the control rod to be safe ?
A Witness hole - if a wire can fit through the hole it’s not safe. If it doesn’t go all the way through then it is safe
A witness line - if this is visible then it is not safe
58
Incorrect adjustment in one part of the system could cause what ?
Result may well be that the control can be operated in one direction
Geometric lock
59
Bell crank
These change the direction of control movement (in a rod system)
Acts with a pivot point
60
To prevent long control runs from distortion shorter rods are used and supported by what
Idler links - similar to bell cranks but do not change direction
61
Torque tube
Used to direct the control run sideways and join pilot and co pilot control levers
Used to change direction of movement if the leavers at each end are attached at different angles
62
Control stops
They stop to much AoA (pitch) on the main rotor blade
Attached to the airframe when control is moved to much a lever makes contact with the stops
Contact pads are fitted to prevent damage when it touches the stop
63
Types of control stops
Fixed
Adjustable - used to adjust the range of maximum travel
64
Control cables
Quadrant
Cables
Cable end fittings
Tension regulator
Turnbuckles
Pulleys
Fairleads
65
Control quadrant
Changes control rod to a cable or cable to control rod
Bearing in the middle acts as a pivot
Has swaged end fittings mounted in receptacles in the quadrant
Cable sits in a grooved perimeter
Control rod attaches at the edge of the quadrant
66
What do cables provide
Strong, light and flexible method of control and are used extensively in aircraft control systems
Operate in tension, only used to pull the control
Two cables can be arranged in a loop to provide a pull in both directions
67
How to operate servo
We go from a quadrant back to a control rod to operate the servo
68
Key parts to control cables
Preformed cable
Swaged end
Lock clad cable
Nylon coated cable
Thermal expansion
Tension regulator
69
Preformed cable
Each strand is twisted into a shape which completes the cable
More flexible
More resistant to kinking
Will not unravel - if a wire breaks it will lie flat
Less likely to prevent the cable from padding round pulleys and through fairleads
70
Cable end fittings
Made from corrosion resisting steel
Various fitting swaged (squeezed) on to the end of the of the cable during manufacture
71
Lock clad cable
Flexible steel wire with a length of tubing swaged to it
Locks the cable together so it reduces changes in tension due to temperature variations
Reduces cable stretch when under load
Whipping action is reduced as the cable is now rigid
72
Nylon coated cable
Flexible nylon sleeve extruded over corrosion resistant cable
Nylon protects cable from Debris and reduces wear
Reduces friction between cable and pulley thereby reducing overall friction in control system
73
Thermal expansion on control cables
Aluminium alloy has a higher coefficient of expansion than steel
With increasing ambient temperature the fuselage will expand more than the cables
Tension of the cables will increase
74
How do you overcome ambient temperature decrease
By fitting a cable tension regulator
75
Tension regulator
Maintains cable tension within limits
76
Need for cable tension
System operated effectively - not to taut or slack
Excessive tension imposes unnecessary load on the system
A slack cable will result in ineffective response
Temperature, Cable stretch and general wear of supporting parts will affect tension
Must be checked and adjusted
77
Turn buckles
Used to join cables together
Adjusts length and tension
Screws into the fixed fittings on the cable ends (swaged and fittings)
Threads must be evenly engaged at either end
78
Turn buckles are Locked with either:
Locking wire
Locking clips
79
Tension rod type turnbuckle
Solid rod body with a left and right-hand screw thread
Rotating the rod will tighten or loosen the cable tension
Safety inspection or witness hole
Usually wire locked
80
Barrel type turnbuckle
Operation is same as tension rod type
Locked with special spring clips or wire locking
81
Difference between barrel type threads and tension rod types
Barrel is internal thread
Tension is external thread
82
Left hand threads , how are they marked
Grooves or notches cut into the corners of the flats
Be aware that notches cut into the flats also indicate HTS ( high tensile steel)
83
Pulleys
Used to change the direction of the flying control cables
Used to give support on long cable runs
Consists of a bearing and a grooved disc
84
What is a cable guide or retainer used for ?
To ensure cable remains on the pulley
85
What are pulleys made from?
From phenolic or aluminium
Softer material means the V groove is subject to wear from the steel control cable
86
Fairleads
Restricts the sideways fluctuations of the cable caused by aircraft vibrations
87
What are Fairleads made from
Low friction material, such as
fibre
tufnol
nylon
as the cable may directly contact the fairlead leading to wear
88
Clearance between cable Fairleads
Too big gap - excessive vibrations
Too small gap - excessive wear
89
What is an interlink assembly
Interlink assemblies are installed in the cyclic system to automatically cancel unwanted effects of change of the collective lever
90
The fore and aft interlink
Automatically sends a nose down input when collective is lifted
Vise verser
91
Constant rotor speed during collective pitch change
Alter fuel supply to the engine to maintain constant engine rotational speed
Provided by fuel computer
Hydro mechanical governor
92
What are powered flying controls used for ?
Required to provide sufficient force to operate the controls satisfactorily
Assists the pilots control effort
93
What type of powered flying controls is there ?
Hydraulically powered servo jacks
94
What are powered flying controls usually fitted to
Non rotating star
Spider
95
Tail rotor control run
Both main rotor and tail rotor controls may be power assisted
96
What issues could happen with powered flying controls?
Hydraulic failure
97
How to overcome hydraulic failure
Revert to manual controls
On large helicopters have a duplicate hydraulic system
98
What does a fly by wire do ?
Replaced the manual controls with an electronic interface
Movements of flight controls are converted to electronic signals
Flight control computers interpret signals and move actuators
Allows the computer to perform functions without the pilots input
The computer won’t let the pilot complete an unsafe movement
99
Redundancy
Allows one of the systems to fail and the other one will still work making it safe
100
Fly by wire failure what does it do
It recognises the failure and still allows it to be flown safely and to land
101
Maintenance of controls
What does they examine
Bearing and security
Corrosion
Damage
Correct rigging
102
Control rod maintenance
Should be perfectly straight
Checked for freedom of movement
Correct alignment
Friction pull off
Range of movement
Not fouling/chafing other systems
103
What is friction pull off
Friction check
104
Control cable maintenance
Maker sure they don’t get contaminated - it will cause wear
Must be uncoiled straight
105
The majority of cable failure is caused by :
Wear and corrosion
Individual wires failing due to fatigue and bending
Kinking and wire distortion caused by incorrect handling
Failure at the end fitting
Internal corrosion
106
What must you check on new cables
Part number is correct
End fittings are complete
107
Examine pulleys for
108
Rigging
The practise of truing and checking the system to ensure that the flying controls operate correctly
109
What is a control surface
Rotor blade
110
When is rigging carried out
When maintenance manual tells you
After disturbing any part of the control system
111
Checks before rigging
No obstructions which could damage the control surface
It is important to display warning notices informing personnel of the possibility of movement
Inform personnel working in the versinity
112
Checks before rigging
Level the aircraft both laterally and longitudinally
Aircraft maintenance manual will state when to do it
Make sure that all parts are actually serviceable - no point in rigging if you have to replace something
Check cables, pulleys, Fairleads and tubes
113
What are issued in sets, specific number parts and have a specific place
Rigging pins
114
Blade tracking
Used to describe the tip path followed by the main rotor blades as they rotate about the main rotor mast.
115
How is blade tracking measured
Opto-electronic devices or laser equipment
116
Blade tracking is carried out
Part of a rigging process
After a dynamic component change in the rotor system
Following a pilot report of vibration
117
Independent inspection
Inspection for correct assembly
Functional test of the system
It's complete by someone who is not on the job
