TD 29

Question 1

Dynamic Rollover

Answer 1

A helicopter is susceptible to a lateral-rolling tendency called dynamic rollover. Dynamic rollover can occur on level ground as well as during a slope or crosswind landing and takeoff. Three conditions are required for dynamic rollover—pivot point, rolling motion, and exceed critical angle.

Question 2

Retreating Blade Stall

Answer 2

As the stall of an airplane wing limits the low speed of a fixed wing aircraft, the stall of a rotor blade limits the high speed of a rotary-wing aircraft. In forward flight, decreasing velocity of airflow on the retreating blade demands a higher AOA to generate the same lift as the advancing blade. Figure 1-79, page 1-66, illustrates the lift pattern at a normal hover with distribution/production of lift evenly spread throughout the rotor disk.

Question 3

Settling with Power

Answer 3

Settling with power is a condition of powered flight in which the helicopter settles in its own downwash (may also be referred to as vortex ring state).
Under certain conditions the helicopter may descend at a high rate which exceeds the normal downward induced flow rate of the inner blade sections (inner section of the rotor disk).

• airflow of the inner blade sections is upward relative to the disk-> produces a secondary vortex ring in addition to the normal tip vortex system.
• secondary vortex ring is generated about the point on the blade where airflow changes from up to down.
• the result: an unsteady turbulent flow over a large area of the disk which causes loss of rotor efficiency although engine power is still supplied to the rotor system.

Question 4

Vestibular Illusions

Answer 4

The vestibular system provides accurate information on the ground, but is vulnerable to illusions in the dynamic flight environment—particularly in depraved visual environments—posing the threat of SD.

Somatogyral: false sensation of rotation due to semicircular canals inability to accurately register sustained angular velocity.

• Leans
• Graveyard Spiral
• Coriolis Illusion

Somatogravic: when changes in gravity or linear acceleration stimulate the otolith organ which responds to gravitointertial force, not gravity alone.

• G-excess Illusion
• Elevator Illusion