18 Application. The confined area landing and approach is a precision, power-controlled approach used when the intended point of landing is surrounded by obstacles preventing a normal approach glide slope. The techniques of utilizing power and cyclic coordination to effect a precision descent shall be used in the confined area approach and landing.Maneuver Description and TechniqueUse a pattern altitude of ’ AGL and 70 knots. Make a reconnaissance of the landing zone to ensure the area is clear and to check the best arrival and departure routes. Descend to no lower than 200' AGL and go no slower than 50 knots on the reconnaissance pass.
19 2. When abeam the intended point of landing at pattern altitude of feet AGL and airspeed of 70 KIAS, simultaneously commence a descending, decelerating turn to arrive at the 90-degree position with 300 feet AGL and 60 KIAS (same 90-degree position as in a precision approach). 3. Anticipate a level-off at 300 feet AGL and continue to decelerate to arrive on the courseline with feet of straightaway at 300 feet AGL. Report on final when established. Continue to decelerate to 45 KIAS while approaching the glideslope. 4. As the helicopter intercepts the glideslope (25-45 degrees) reduce power to begin the descent. Visualize the glideslope and closure rate to the intended point of landing. Adjust power as necessary to maintain the glideslope. If the glideslope becomes excessive (greater than 45 degrees) or uncomfortable, wave off.
20 5. Once established on the glideslope, adjust the angle of descent such that the tail rotor will clear the downwind obstruction by at least ten feet and the touchdown area will be in the upwind one-third of the LZ. Smooth, coordinated cyclic and collective inputs are required to maintain the glideslope without requiring excessive power.6. Anticipate sloping or rough terrain in the landing zone, therefore, plan on coming to a hover attitude prior to executing a touchdown.
21 Common Errors and Safety Notes 1. Ensure power required to land does not exceed power available.2. Rate of closure is critical. As rate of closure increases, rate of descent also increases. Avoid descent rates in excess of 800 FPM when airspeed is below 40 KIAS; vortex ring state may result.Whenever the glideslope exceeds 45 degrees or the approach becomes uncomfortable, wave off.4. As the helicopter crosses the obstruction, ensure the crew has cleared the tail rotor. If not clear, wave off.
22 5. Anticipate a loss of wind effect or turbulence as the helicopter nears and descends below the obstruction.Failure to reduce collective a sufficient amount when intercepting the glideslope will cause ballooning or steepening of the glide angle.7. While in the confined area landing zone, any aircraft movement shall be cleared by all crewmembers prior to commencement. The aircraft may be turned a maximum of 90o at a time.
25 Confined Area Takeoffs Application. The confined area takeoff is a precision maneuver designed to provide proper obstacle clearance and minimal exposure to the Caution/Avoid areas of the Height-Velocity Diagram.Procedures/Maneuver Description and Technique1. Prior to landing in a confined area, ensure power required does not exceed power available. If sufficient power is not available to take off from a confined area, do not land in one.2. Select the best takeoff route optimizing wind and the lowest obstruction combination. Remember to include a minimum of ten feet of clearance from the highest obstruction on the intended flight path. If possible, the takeoff should be initiated from the downwind one-third of the LZ. This will provide the most shallow departure glideslope.
26 3. Call on radio, "(Aircraft call sign), lifting CAL Zone 4 3. Call on radio, "(Aircraft call sign), lifting CAL Zone 4. From a hover, check the gauges and caution lights, then smoothly increase power to establish a sufficient rate of climb and angle of ascent to clear the highest obstacle by ten feet (tip path plane above highest obstacle). When able, begin a smooth acceleration and transition to a normal takeoff. Keep the scan moving and CONTINUALLY CLEAR ALL PARTS OF THE HELICOPTER. 5. When clear of all immediate obstructions, maneuver as necessary to avoid other obstacles while gaining airspeed as soon as possible.
27 Common Errors and Safety Notes 1. Always ensure tail rotor clearance prior to maneuvering in the zone. A tail rotor strike may occur resulting in complete loss of tail rotor thrust.2. Rushing the maneuver may cause settling, poor yaw control, and loss of obstruction clearance. Confined area takeoffs are precision maneuvers and require more time and concentration than normal takeoffs.3. Smooth control coordination is required throughout the takeoff. Use power judiciously.4. Because the helicopter is below the obstructions, the wind may not provide extra lift until clear of the obstructions.
31 Vortex Ring StateVortex ring state is an uncommanded rate of descent caused by the helicopter settling into its own downwash. In this state, the flow through the rotor system is upward near the center of the rotor disk and downward in the outer portion. This results in zero net thrust from the rotor and extremely high aircraft descent rates. Vortex ring state is not restricted to high gross weights or high density altitudes. It may not be recognized and a recovery effected until considerable altitude has been lost. Helicopter rotor theory indicates that it is most likely to occur when descent rates exceed 800 feet per minute during (1) vertical descents initiated from a hover and (2) steep approaches at less than 40 KIAS.Indications to the pilot are:1. Rapid descent rate increase2. Increase in overall vibration level3. Loss of control effectiveness
32 Vortex Ring State Recovery Recover by:1. Forward cyclic to gain airspeed.2. Decrease collective.If impact is imminent:3. Level aircraft to conform to terrain.WARNINGIncreasing collective has no effect toward recovery and will aggravate vortex ring state. During approaches at less than 40 KIAS, do not exceed 800 feet per minute descent rate.