NATOPS CH 11

Question 1

Normal Hover attitude

Answer 1

4-5 Deg nose up

2-3 deg left wing down

Question 2

Speed of balde tips

Answer 2

725 ft per second or mach .65

Question 3

Ground Effect

Answer 3

• When rotor disk is within one rotor diameter of the ground
• Causes the main rotor thrust vector to shift forward so that it is more vertical (more lift/less induced drag)
• Effects are strongest close to the ground and dissipate rapidly as altitude above ground is increased
• MH-60R is considered to be in ground effect at radar alimeter altitudes at or below 45 feet

Of note: downwash below the rotor can exceed 50 knots.

Question 4

Flapping

Answer 4

Blade on advancing side of the rotor flaps up, decreasing AOA, and reducing lift generated. The retreating blade flaps down, increasing AOA, and generating additonal lift.

Question 5

Blowback

Answer 5

• If the aircraft is exposed to a headwind gust, the retreating blade sees less relative wind velocity and the advancing balde sees more relative wind velocity. This causes the rotor disk to be tilted aft or “blown back”
• Blowback of the main rotor disk tilts the main rotor thrust vector aft, causing the nose of the helo to pitch up.
• Blowback makes the helo unstable with respect to gusts on the nose.
• This reaction is countered by pilot input in the long term and by the hover augementation/gust alleviation feature of SAS 2, and altitude hold feature of the autopilot in the short term.

When transitioning to formward flight, blowback results in more forward cyclic being required to continue acceleration

Question 6

Stab programing

Answer 6

Begins at 30 KIAS, causes nose forward pitching moment until then.

Question 7

Translational Lift

Answer 7

• Results from an reduction in induced power, and overall reduction in power required for forward flight
• Maintaining hover power will result in approx a 500 fpm rate of climb at 80 KIAS
• As the airspeed reaches approx 17 knots, a noticeable vibration will be felt as the aircraft encounters its own ground vortex. The ground vortex is rolled up under the aircraft as speed continues to increase and disipates as the aircraft reaches approx 30 knots.

Question 8

Tail winds when transitioning to forward flight

Answer 8

Basically, be aware that power requirements will increase as you pass through a state of zero wind

Question 9

Blade Stall

Answer 9

• First occurs at the root
• Most likely to occur when operating at high values of speed, gross weight, DA, and power. Any of these conditions is especially aggravated by low rotor RPM.
• Maneuvers, acceleration or turbulent air, al of which increase g-load factors, will induce blade stall by reducing the airspeed at which blade stall will occur

Question 10

Methods of Eliminating Roughness Caused by Blade Stall

Answer 10

Decrease collective pitch
Decrease severity of maneuver
Gradually decrease airspeed
Increase rotor RPM
Decrease altitude
Decrease gross weight

Question 11

LTE Zones

Answer 11

AOA reduction 060 to 120
Weather vaning 120 to 240
Tail rotor vortex ring state 210 to 330
Main rotor disc vortex interaction 280 to 330 , less frequently from 30 to 80

Question 12

LTA

Answer 12

LTA is a power issue. Usually seen in high gross weight and/or high DA conditions. Left pedal response may be sluggish. In extreme cases, main rotor speed will droop. As Nr droops, Q increases, power available decreases. Helo spins to the right.

Question 13

LTE

Answer 13

Inability of the tail rotor to provide to provide sufficient force to maintain yaw controllability. Occurs when full pedal input is insufficient to provide directional control. TR thrust function of operating RPM and TR AOA. Two primary directional control mechanisms are AOA and weather vaning tendency of the fuselage. Relative wind direction, low speed/high power maneuvering, operating RPM, gross weight, and DA contribute to LTE.

Question 14

Recovery from LTE

Answer 14

1. Altitude permitting, lower collective to reduce Q and assist in arreting right yaw. Too much descent rate = more power required to arrest, may reinitiate LTE.
2. Using forward cyclic to increase airspeed and if necessary, turning in the direction of rotation. Reduces TR thrust required and produces a streamlining effect.
3. At very slow speeds or in a hover, applying full left pedal may arrest right yaw.

Question 15

Initial evasive maneuvering traning

Answer 15

Initial evasive maneuvering training shall only be conducted under the supervision of qualified instructor pilots. The training shall only be accomplished during approved syllabus training flights.

Question 16

Tail rotor spar loads in maneuvering flight

Answer 16

CCW turning single main rotor helos exhibit transient torque increases in forward flight with roll rates to the left. Left roll rate increases retreating blade AOA, driving up torque, and main rotor procession loads further contriubute to this effect. Left roll rates (above approx 30 deg/sec in forward flight above 75 KIAS) can combine with induced tail rotor gyroscopic and flapping loads to cause excessive tail rotor spar loading.

When executing high roll rate maneuvers to the left, collective should be lowered concurrently with maneuver initiation to control transient Q and reduce tail rotor spar loads.