Main Rotor Flashcards
What is the MR comprised of?
- MR mast in 3 sections
- MR hub (Startflex)
- 3 rotor blades
- Vibration absorber
Where is the hub located relative to the airframe? What does it do?
Located at the center of the resultant lift of the blades.
- supports the blades
- absorbs the forces induced by the rotation (centrifugal, flapping, lead/lag loads
Overall weight of Starflex rotor head
121 lbs
Rotor diameter
10.69 m
35.07 ft
To prevent MR settings being lost on removal/install …
- Starflex hub can only be mounted on one position on the mast
- each blade/sleeve/rod forms and assembly that is ident by a diff color (yellow, blue, red)
What does the mast consist of?
- Lower casing: four contacts bearing, planet gear, upp MGB electrical chip detector
- Upper casing: Nr phonic wheel and sensor
- Swashplate assembly: 4 contacts bearing, stainless steel ball joint, teflon guide tape
How are the swashplates connected?
Rotating star rotates on a bearing and copies movements of stationary star which pivots off a balljoint
- rotating star is attached to the rotor shaft by the upper scissors
- stationary star is kept from rotating by a lower scissor attached to the casing
What suspends the entire helicopter?
The 4-contacts thrust bearing
Why is it called Starflex?
- Composite, Glass Resin STAR
- 3 FLEXible arms in the flapping direction
- Decays slowly, fail safe
What joins the blades to the Starflex hub?
Rigid sleeves - so that the hub performs the following functions:
- flapping
- drag
- pitch change
How is flapping accomplished?
Starflex arms are flexible in flapping
Sleeve assembly flaps about the Laminated Spherical Stop Bearing which distorts elastically to flap
How is lead/lag forces accomplished?
The Starflex arms are rigid in plane
- sleeve pivots about center of Laminated Spherical Stop Bearing, deforms the Elastomer Frequency Adapter Blocks in shear
How is pitch change accomplished?
Starflex arms are rigid in torsion
- Laminated Spherical Stop Bearing deforms in Torsion
- Sleeve rotates about the axis from the Laminated Spherical Stop Bearing center and the Ball Joint Center
How are each accomplished:
Flapping, Pitch change, lead/lag
- Flapping: Starflex arms and Laminated Spherical Stop Bearing
- Pitch change: Distorsion of the Laminated Spherical Stop Bearing, rotating about axis with Ball Joint Center
- Lead/Lag: Pivoting about center of Laminated Spherical Stop Bearing and deforms Elastomer Frequency Adapter Block
In which planes is the Starflex rigid/flexible?
Flapping: Flexible
Pitch Change: Rigid
Lead/Lag: Rigid
Composition of the MR blades?
- Fiberglass roving leading edge spar w/ box structure
- Stainless steel leading edge cuff
- Glass fabric skin
- Foam core
- Polyurethane strip integrated on underside of blade
What is the Rotor Hub Vibration Absorber?
- Counteracts cyclic (lateral) vibration
- Weight held in place by 3 springs
- Centering and retaining balljoint guide weight
- Protected by a boot
What are the cabin resonators and their purpose?
2 attached to the bottom structure beam, resonators respond to the excitation frequency of the aircraft by counteracting with a cancelation frequency.
How is Rotor Speed Nr determined?
Using a slotted wheel driven by the mast and a phonic magnetic rate sensor.
- when the wheel tooth passes the sensor the magnetic flux is at maximum
- when a gap passes the sensor the magnetic flux is at minimum
Wind demo during start/shutdown
40kts from any direction
50kts with a headwind +/-30deg off the nose
Rotor brake operation
170 PRM = max for brake application (allowable for high winds)
140 RPM = normal operation for brake application
100 RPM = AMC max operation for brake application, unless winds are high
What are Pilot Induced Oscillations (PIO)
Result from efforts of the pilot to control the aircraft.
- can be caused by abrupt input on controls or turbulence
- corrective action: release collective and let aircraft correct itself
