NATOPS Chapter 11 Flashcards
Normal Hover Attitude
4-5* nose up
2-3* left wing down
Ground Effect
When the rotor disk is within one rotor diameter of the ground
Blowback
Retreating blade sees less relative wind
Translational Lift
Approximately 17 -30 knots
Blade Stall Recovery
Decrease collective
Decrease Severity of Maneuver
Decrease Airspeed
Increase rotor RPM
Decrease Altitude
Decrease Gross Weight
Tail Rotor
Tractor Tail rotor canted at 20% providing 2.5% of total lift in a hover.
Loss of Tail Rotor Authority
LTA is an issue of power. Seen at high gw/high DA. Left pedal will be sluggish or you can droop.
Nr drooping
As Nr droops, torque increase while power available to the main rotor and tail rotor decrease. Eventually the tail rotor cannot produce enough anti-torque and the helicopter will spin right.
Loss of Tail Rotor Effectiveness
LTE is the inability of the tail rotor to provide sufficient force to maintain yaw controllability. A function of operating rpm and tail rotor angle of attack. Relative winds, low-speed/high power maneuvering, gross weight, and high da are all factors.
High power… lots of left pedal
Tail rotor winds
Winds from the right, decrease AoA and reduce effectiveness
Winds from the left, increase AoA and improve effectiveness
AoA Reduction Winds
060-120 relative
Weather Vaning
120-240 relative
Aircraft wants to nose into the wind
Tail Rotor Vortex Ring State
210-330 relative
Tail rotor operates in its own recirculated airflow
Main Rotor Disk Vortex Interaction
280-330 relative
Main rotor vortex directed to the tail rotor changing Tail Rotor AoA
Hover/Air Taxi
Right sideward flight can increase airflow across the tail, reduction in AoA
Recovery from LTE
Lower the collective to stop the right yaw
Gain forward airspeed, if necessary turn in direction of rotation
At very low airspeeds, full left pedal may stop it
Tail Rotor Spar Damage
Left turns in excess of 30* per second above 75 KIAS may cause damage to the spar
AoA Reduction Winds
060-120 relative
AoA Reduction Winds
060-120 relative
4/rev vibration
Indication that the lift generation of the rotor has been exceeded. Correct by reducing collective
AoA Reduction Winds
060-120 relative
Main Rotor Flapping
Inducement of less than 1G flight may exceed main rotor flapping margin and cause droop stop pounding
AoA Reduction Winds
060-120 relative
Power Required Exceeds Power Available
At High DA, high GW.
Add +100 DA for every 10% humidity above 40%.
AoA Reduction Winds
060-120 relative
Vortex Ring State
Encountered:
Greater than 700fpm descents 0-20KIAS
@1500fpm descent 5-10KIAS
Leads to uncommanded pitch and roll oscillations and descent rate may approach 6000’
AoA Reduction Winds
060-120 relative
Vortex Ring State Recovery
Decrease Collective Pitch
Increase forward airspeed
Enter Autorotation if altitude permits.
AoA Reduction Winds
060-120 relative
Autorotational Airspeed
Enter at max 100 KIAS
Min rate of descent 75 KIAS
Max glide 95 KIAS
AoA Reduction Winds
060-120 relative
Autorotation Nr
Actual- In the approach close to 100, in the flare as much NR as possible
Practice- As close to 100 as possible to provide faster engine spool up when Nr droops below 100%
AoA Reduction Winds
060-120 relative
Dynamic Roll over
Ground contact, and a rolling motion. Opposite cyclic may not be enough to correct, and may exaserbate the problem by adding lift into the equation
AoA Reduction Winds
060-120 relative
Sloped Landing Considerations
Consideration should be given to setting the parking brake.
With parking brake increased risk of dynamic rollover
Without increased risk of rolling out of zone
Land with upslope wheel first, the keep the rotor disk level
Extreme aft cyclic may cause droop stop pounding, or main rotor blades striking the tail pylong
Salt water power deterioration
20C indication of engine performance degradation and possible salt encrustation
40C indication of engine performance degradation which may cause compressor stall
Look for TGT and Torque relationship
Salt Water ingestion
Greatest in winds of 8-12 knots due to sea spray being lifted
Small risk in winds 15-20 knots as spray is blown under the aircraft
Lower hover alt = greater risk of ingestion
Flight with external loads
Know the riding characteristics
Oscillations can be minimized with smooth control inputs
There is a best airspeed for a load
Be wary of loads aerodynamic properties
Performance in Icing
If unanticipated icing is encountered first consideration should be exiting icing conditions
Main rotor vibrations
1 per rev - main blades out of track, or worn or loose control rod bearings
ground 1 per - static imbalance of main rotor, or improper landing gear strut servicing
1.44 per rev - SAS and pilot induced oscillations longitudinally
4 per rev- asymmetrical blade loading. vertical and lateral shakes
Ground Resonance
Caused by out of phase lead lag tendency, or system dampers.
Can occur within 3 seconds and produce violent vibrations.
Will continue to build until take off or main rotor is disengaged.
Tail Rotor Vibrations
Tail shake 5hz - felt as a random impulse around yaw axis
Tail Drive Shaft Vibes (high freq) - caused by an unbalanced driveshaft, buzz in the pedals or tickling in the nose
1 per 20hz- tail rotor imbalance, loose hardware or damage.
AoA Reduction Winds
060-120 relative
