TD 30

Question 1

Loss of Tail Rotor Thrust

Answer 1

a. This situation involves a break in the drive system, such as a severed driveshaft, causing the tail rotor to lose power.

b. Indications:
1. Pedal input has no effect on helicopter trim.

WARNING
Degree of roll and side-slip may be varied by varying throttle and/or collective. (At airspeeds below approximately 50 knots, the side-slip may become uncontrollable, and the helicopter will begin to spin on the vertical axis.)

    2. Nose of the helicopter turns to right (left sideslip).  
    3. Left roll of fuselage along the longitudinal axis.  

c. Procedures:
1. If safe landing area is not immediately available, continue powered flight to suitable landing area at or above minimum rate of descent autorotational airspeed.
2. When landing area is reached, make an autorotational landing (THROTTLE CLOSED).
3. Use airspeed above minimum rate of descent airspeed.

NOTE
Airflow around the vertical fin may permit controlled flight at low power levels and sufficient airspeed when a suitable landing site is not available; however, the touchdown shall be accomplished with the throttle in the full closed position.

    4. If run-on landing is possible, complete autorotation with touchdown airspeed as required for directional control.  
    5. If a run-on landing is not possible, start to decelerate from about 75 feet altitude, so that forward groundspeed is at a minimum when the helicopter reaches 10 to 20 feet; execute the touchdown with a rapid collective pull just prior to touchdown in a level attitude with minimum ground run. 
    6. Hover – Perform hovering autorotation.

Question 2

Loss of Tail Rotor Components

Answer 2

a. The severity of this situation is dependent upon the amount of weight lost. Any loss of this nature will result in a forward center of gravity shift, requiring aft cyclic. A full autorotational descent and landing should be accomplished with a run-on type termination if to an improved surface, or minimum ground run if to an unimproved surface. Landing should be accomplished in a level attitude.

b. Indications:
1. Varying degrees of right yaw depending on power applied and airspeed at the time of failure.
2. Forward CG shift.

c. Procedures:
1. Enter autorotative descent (THROTTLE CLOSED).
2. Maintain airspeed above minimum rate of descent airspeed.
3. If run-on landing is possible, complete autorotation with touchdown airspeed as required for directional control.
4. If run-on landing is not possible, start to decelerate from about 75 feet altitude, so that forward groundspeed is at a minimum when the helicopter reaches 10 to 20 feet; execute the touchdown with a rapid collective pull just prior to touchdown in a level attitude with minimum ground run.

Question 3

Transverse Flow Effect

Answer 3

In forward flight, air passing through the rear portion of the rotor disk has a greater downwash angle than air passing through the forward portion.

• causes unequal drag in the fore and aft portions of the rotor disk and results in vibration easily recognizable by the aviator
• occurs between 10 and 20 knots
• most noticeable during takeoff and during deceleration for landing
• right rolling motion due to gyroscopic precession

Question 4

Hypoxia

Answer 4

Hypoxia is defined as the state of oxygen deficiency in the blood cells and tissues enough to cause impairment of function.

Types of hypoxia:

    1. Hypoxic- altitude, when there is not enough oxygen in the air or decreasing atmospheric pressure prevents diffusion of oxygen into the bloodstream.
    2. Hypemic- blood loss, anemia, smoking, reduction in the blood’s oxygen carrying capacity
    3. Stagnant- heart attack, pooling from G forces, blood’s oxygen carrying capacity is adequate but circulation is not
    4. Histotoxic- alcohol, interference with the use of oxygen by body tissues

Stages of hypoxia:
- Indifference stage
Surface-10,000; night vision affected at 4,000’, effect of hypoxia increased with self imposed stressors
- Compensatory stage
10,000-15,000; effects on CNS, impaired efficiency is apparent after 10-15 minutes
- Disturbance stage
15,000-20,000; physiological responses can’t compensate for oxygen deficiency, LOC, loss of senses (vision first, hearings last), reduced mental processes, unusual personality traits, reduced psychomotor functions, cyanosis
- Critical stage
20,000+; 3-5 min = judgement and coordination lost, mental confusion, dizziness, incapacitation, and LOC

Treatment:
100% oxygen and descend to below 10,000’

Prevention:
Prevention methods include limiting time at altitude, using supplemental O2, and pressurizing the cabin.
Supplemental oxygen- 
>10,000’ for > 1 hour
>12,000’ for >30 min
>14,000’ for any amount of time