TD 29

Question 1

Retreating Blade Stall

Answer 1

Definition: retreating blade eventually stalls in high speed flight because of the high AoA needed to compensate for dissymmetry of lift. Decreasing velocity of airflow on the retreating blade demands a higher AoA to generate the same lift as the advancing blade. The stall will begin at the tip of the blade and advance inboard.

Indications: rotor followed by left roll and pitch up

Conditions that produce retreating blade stall:

1. High gross weight
2. High density altitude
3. High “G” maneuvers
4. Low rotor RPM (rotor drop)
5. Turbulent air

Corrective Actions:

1. Reduce airspeed
2. Reduce collective
3. Reduce altitude
4. Reduce security of the maneuver
5. Increase rotor RPM to normal limits

Question 2

Settling with power

Answer 2

Definition: A condition of powered flight in which the helicopter settles in its own downwash, also referred to as vortex ring state.

Conditions req. for settling w/ power

1. Vertical/near vertical rate of descent of 300 FPM or more
2. Slow forward airspeed (less than ETL)
3. Rotor system using 20-100% of available engine power

Conditions conducive for settling w/ power:

1. Steep approach at a high rate of descent
2. Formation flight approach
3. Downwind approach
4. OGE hovering above max hover ceiling
5. OGE hove w/ not-constant altitude
6. Masking/unmasking

Corrective action:

1. Cyclic - forward, to gain airspeed [preferred method]
2. Collective - a large application during the initial stage

Question 3

Dynamic Rollover

Answer 3

Definition: susceptibility of a helicopter to a lateral rolling tendency

Conditions:

1. Pivot point - contact w/ the ground
2. Rolling motion - more rolling motion means critical angle is exceeded sooner
3. Exceeding the critical angle - angle which, if exceeded, recovery is impossible

Types of dynamic rollover:

1. Rolling over on level ground (Most COMMON)
2. Rolling upslope
3. Rolling downslope

Question 4

Dynamic Rollover 
     Physical Factors 
     Human Factors 
     General Factors 
     Common Errors

Answer 4

Physical Factors (MAST-C)
Main rotor Thrust 
Aircraft CG 
Sloped Landing Area 
Tail rotor Thrust 
Crosswind component 

                       Human Factors (FLIII) Failure to make timely control movements  Loss of visual reference points  Inexperience  Inattention  Inappropriate control inputs 

                        General Factors (CHILL) 
Crosswind 
High roll rates 
Left pedal inputs
Lateral landing 
Left skid high/Right skid high 

                      Common Error (RALF) Rapid collective during slope landing/takeoff Abrupt cyclic in fully articulated rotor systems  Large and/or uncoordinated anti-torque pedal inputs  Failure to detect lateral drift before heading

Question 5

Vestibular Illusions

Answer 5

Definition: consist of semicircular canals or otoliths organs

There are two types of vestibular systems are:
Semicircular canals - angular acceleration (pitch, yaw, roll)
Otolith canals - linear acceleration and gravity (deceleration)

The categories of vestibular illusions are:
Somatogyral illusions - semicircular canals
The Leans (Most Common)
Graveyard Spin/Spiral (Mostly In fixed wing)
Coriolis Illusion (Most Dangerous)
Post-Roll (Gillingham) Illusion
Somatogravic illusions - otoliths organs
G-excess Illusion
Elevator illusion
Oculogravic illusion
Alternobaric vertigo
Influence of all Ohio or drugs
The types of visual illusions are:
False Horizon
Vection
Fixation

     Height-Depth Perception illusion 
     Autokensis 
     Size constancy
     Confusion w/ ground lights
     Size-Distance illusion 

 Crater illusion 
  Aerial perspective 
  Shape constancy
  Structural illusion