FM 57-38 Chptr 4 - Helicopt...pdf - heli - arod1

FM 57-38 Chptr 4 - Helicopter Landing Zones

http://www.globalsecurity.org/military/library/policy/army/fm/57-38/C...

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FM 57-38 Chptr 4 - Helicopter Landing Zones

http://www.globalsecurity.org/military/library/policy/army/fm/57-38/C...

M ILITARY

THIS CHAPTER IMPLEMENTS STANAGs 3218 AND 3619 AND QSTAG 585 .

CHAPTER 4

HELICOPTER LANDING ZONES

Helicopter landing zones contain one or more helicopter landing

sites. A control center is established at each landing site and a

release point (manned or unmanned) is normally selected for the LZ

( STANAG 3619 ).

Section I. SITE SELECTION AND LANDING POINTS

The ground unit commander, in coordination with the supporting aviation

unit, selects the location of helicopter LZs that support the ground

tactical plan.

4-1. REQUIREMENTS

Minimum landing space requirements and minimum distance between helicopters

on the ground depend upon a number of variables. These requirements are

covered by aviation unit SOPs, or they are prearranged by the aviation unit

commander in coordination with the pathfinder leader. The final decision

concerning minimum landing requirements rests with the aviation unit

commander. In selecting helicopter landing sites from maps, aerial

photographs, and actual ground or aerial reconnaissance, the commander

considers the following factors.

a. Number of Helicopters. Animportant factor is the number of helicopters

required to land at one time at one site to accomplish the mission. It

maybe necessary to provide another landing site(s) nearby or to land

helicopters in successive lifts at the same site.

b. Landing Formations. When they can, helicopters should land in the same

formation in which they are flying. However, planned formations may require

modification for helicopters to land in restrictive areas. If a

modification in flight formation is required for landing, use the change

requiring the least shift in the formation ( Figure 4-1 ).

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FM 57-38 Chptr 4 - Helicopter Landing Zones

http://www.globalsecurity.org/military/library/policy/army/fm/57-38/C...

c. Surface Conditions, Surfaces must be firm enough to prevent helicopters

from bogging down, creating excessive dust, or blowing snow. Rotor wash on

dirt, sand, or snow-covered surfaces may obscure the ground and should be

avoided, especially at night. Remove from landing points debris that could

damage the rotor blades or turbine engine(s).

d. Ground Slope. The ground should be relatively level and the slope should

not exceed 7 degrees if the helicopter is to land safely ( Figure 4-2 ).

However, observation and utility helicopters can terminate at a hover over

ground slopes exceeding 7 degrees to load or to off-load personnel or

supplies. Large utility and cargo helicopters can also land on terrain with

a slope ranging from 0 degrees to 7 degrees. From a 7- to 15-degree slope,

direct pilots to hover, as appropriate. Make landings upslope whenever

possible and avoid landing downslope.

NOTE: To determine slope in percentage or degrees, all measurements may be

expressed in feet or meters. If the elevation on the map sheet is expressed

in meters, convert meters into feet by multiplying by three. If in feet,

convert to meters by dividing by three.

e. Approach and Departure Directions. The direction of landing should be

over the lowest obstacles and generally into the wind, especially at night.

However, if there is only one satisfactory approach direction, or if it is

desired to make maximum use of the available landing area, most helicopters

can land with a crosswind of 6 to 9 knots or a tailwind of 0 to 5 knots.

For wind stronger than 9 knots, the pilot lands into the wind. The same

considerations apply to departures from landing sites.

f. Prevailing Wind. Consideration of approach and or departure routes is

more important than that of prevailing wind unless a crosswind velocity

exceeds 9 knots. The ability to land crosswind or downwind depends on the

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FM 57-38 Chptr 4 - Helicopter Landing Zones

http://www.globalsecurity.org/military/library/policy/army/fm/57-38/C...

type of helicopter. Small helicopters can accept less crosswind or tailwind

than larger, more powerful helicopters.

g. Density Altitude. The density altitude is determined by altitude,

temperature, and humidity. For planning, as density altitude increases, the

size of the LZ must also be increased because high, hot, and humid

conditions decrease the lift capabilities of helicopters using that site.

h. Loads. Most helicopters cannot climb or descend vertically when fully

loaded. Therefore, a large area and better approach/departure routes are

required for fully loaded helicopters than for empty or lightly loaded

ones.

i. Obstacles. Landing zones should be free of tall trees, power lines, and

similar obstructions on the approach/departure ends of the landing site.

Obstacles within the landing site, such as rocks, stumps, holes, and thick

grass or brush (over 0.45 meter or 18 inches), must be removed. For

planning, an obstacle ratio of 10 to 1 should be used; that is, a landing

point requires 100 feet of horizontal clearance from a 10-foot tree if

helicopters must approach or depart directly over the tree.

NOTE: The helicopter unit commander makes the final decision on minimum

landing requirements based on the effects of air density, slope, and

surface conditions. These requirements should be available in oral

instructions during early mission planning.

4-2. ALTERNATE SITES

Enemy action, unfavorable terrain, or changes in the tactical or logistical

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FM 57-38 Chptr 4 - Helicopter Landing Zones

http://www.globalsecurity.org/military/library/policy/army/fm/57-38/C...

situation may require alternate landing sites. These are selected primarily

by the ground unit commander to support the tactical plan. On the

recommendations of the aviation unit commander and the pathfinder on the

site, the ground commander (or his representative) decides when alternate

sites will be used. Instructions concerning their use must be given to

pathfinders by the fastest means available. Pathfinder and aviation unit

commanders do not have the authority to shift to an alternate LZ(s) unless

such authority has been specifically delegated by the supported ground unit

commander.

4-3. LANDING POINTS

These are areas/points (designated by the pathfinder leader) that can

support the weight of a helicopter. As a guide, a helicopter requires a

relatively level, cleared, circular area from 25 to 100 meters in diameter

for landing. This depends on the type of helicopter. The area around the

landing point must be cleared of all trees, brush, stumps, or other

obstacles that could damage the helicopter. Generally, a helicopter

requires more landing area during darkness than during daylight.

Considerations such as helicopter type, nature of load, climate, and

visibility affect what size landing point is used for a particular landing

site.

a. The surface of the landing point center must be level and sufficiently

firm to allow a fully loaded helicopter to land and, if necessary, to shut

down, restart, and depart without sinking into the ground. The term "hard

surface" indicates the proper condition.

b. The entire landing point must be cleared of any loose material that

could be blown up by the rotors. The term is "cleared to ground level." It

would not, for instance, be necessary to clear grass up to 0.3 meter (1

foot) high that might cover a level field unless a fire risk existed. A

dusty surface can be stabilized with water, if available. Snow can be

packed to reduce the amount of blowing snow and removed to reveal hazards.

c. If ground obstructions cannot be cleared, some helicopter operations can

be performed without the helicopter landing. The same dimensions for

clearing and ground markings are required, but the helicopter hovers above

ground obstructions that prevent it from landing. However, every effort is

made by ground troops to improve landing point surfaces to allow the

aircraft to land.

d. Recommended minimum distances between landing points within a landing

site are measured from center to center as follows:

Size 1 landing point . . . . .25 meters.

Size 2 landing point . . . . .35 meters.

Size 3 landing point . . . . .50 meters.

Size 4 landing point . . . . .80 meters.

Size 5 landing point . . . . .100 meters.

Use a 100-meter separation between all landing points if the aircraft are

of varying sizes ( Figure 4-3 ).

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FM 57-38 Chptr 4 - Helicopt...pdf

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