9 US Army IT0637 Selecting Entry Zones on Aerial Imagery

SUBCOURSE IT0637

EDITION B

US ARMY INTELLIGENCE CENTER SELECTING ENTRY ZONES ON AERIAL IMAGERY

SELECTING ENTRY ZONES ON AERIAL IMAGERY Subcourse Number IT0637 EDITION B US Army Intelligence Center Fort Huachuca, Arizona 85613-7000 5 Credit Hours Edition Date: September 1991 SUBCOURSE OVERVIEW This subcourse is designed to teach you basic procedures involved with the selection of entry zones on aerial imagery. Contained within this subcourse are instructions on how to select a drop zone (DZ), helicopter landing zone (HLZ), a potential airplane landing zone (ALZ), and a beach/amphibious landing area.

There are no prerequisites for this subcourse.

This subcourse reflects the doctrine which was current at the time the subcourse was prepared.

TERMINAL LEARNING OBJECTIVE TASK:

You will identify procedures for selecting a DZ, HLZ, a potential ALZ, and a beach/amphibious landing area.

CONDITIONS:

You will have access to extracts from FM 5-34, FM 20-12, FM 30-10, FM 31-11, FM 31-12, FM 57-38, and STP 34-96D24-SM-TG.

STANDARDS:

You will identify procedures for selecting a DZ, HLZ, a potential ALZ, and a beach/amphibious landing area in accordance with FM 5-34, FM 2012, FM 30-10, FM 31-11, FM 31-12, FM 57-38, and STP 34-96D24-SMTG.

i

IT0637

TABLE OF CONTENTS SECTION

Page

Subcourse Overview

i

LESSON 1: DROP ZONE SELECTION Part A: Drop Zone Factors Part B: Drop Zone Computations Part C: Percent of Slope Computations Part D: Surface and Obstacle Considerations Part E: Drop Zone Accessibility Part F: Drop Zone Reports and Overlays Practice Exercise Answer Key and Feedback

1 2 2 6 11 12 13 14 16

LESSON 2: HELICOPTER LANDING ZONE SELECTION Part A: Classification of Helicopter Landing Zones Part B: General Helicopter Landing Zone Criteria Part C: Helicopter Landing Zone Computations Part D: Percent of Slope Computations Part E: Surface and Obstacle Considerations Part F: Helicopter Landing Zone Accessibility Part G: Helicopter Landing Zone Overlays Practice Exercise Answer Key and Feedback

17 17 18 27 28 30 30 30 31 34

LESSON 3: AIRPLANE LANDING ZONE SELECTION Part A: Classification of Airplane Landing Zones Part B: General Airplane Landing Zone Criteria Part C: Airplane Landing Zone Computations Part D: Percent of Slope Computations Part E: Surface and Obstacle Considerations Part F: Airplane Landing Zone Accessibility Part G: Airplane Landing Zone Overlays Practice Exercise Answer Key and Feedback

36 36 37 39 39 39 39 40 43 46

IT0637

ii

SECTION

Page

LESSON 4: BEACH/AMPHIBIOUS LANDING AREA SELECTION Part A: Beach/Amphibious Landing Area Factors Part B: Beach/Amphibious Landing Area Criteria Part C: Beach/Amphibious Landing Area Computations Part D: Percent of Slope and Gradient Computations Part E: Surface and Obstacle Considerations Part F: Beach/Amphibious Landing Area Accessibility Part G: Effects of Weather on Beach/Amphibious Landing Operations Part H: Beach/Amphibious Landing Operations Collection Checklist Preparation Part I: Beach/Amphibious Landing Area Overlays Practice Exercise Answer Key and Feedback

47 47 51 52 54 55 56

APPENDIX A: Glossary APPENDIX B: Formulas and Rules

77 80

58 58 62 64 68

iii

IT0637

LESSON 1 DROP ZONE SELECTION MOS Manual Tasks: 301-338-2803 301-338-3701 OVERVIEW TASK DESCRIPTION: In this lesson you will learn to describe the factors, compute area size and percent of slope, identify hazardous surface conditions and obstacles, and determine accessibility for DZs in the area of operations (AO).

LEARNING OBJECTIVE: ACTIONS:

Describe the information and procedures required to select a DZ.

CONDITIONS:

You will be given access to extracts from FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

STANDARDS:

DZs will be selected in accordance with FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

REFERENCES:

The material contained in this lesson was derived from the following publications: FM 5-34.

FM 30-10.

FM 57-38.

STP 34-96D24-SM-TG. INTRODUCTION

A DZ is a specified area upon which airborne troops, equipment, and supplies are dropped by parachute, or on which supplies and equipment may be delivered by free fall.

1

IT0637

PART A: DROP ZONE FACTORS 1. After receiving a request for intelligence information (RII) from the commander to select a DZ, imagery analysts (IAs) at the collection management and dissemination (CM&D) section must consider the following DZ factors: a. Easy exit from the DZ. b. Type of aircraft employed. c. Altitude at which air delivery is to be made. d. Types of loads to be delivered. e. Relative number of obstacles in the area. f. Availability of adequate aircraft approach and departure routes. g. Method of air drop: Free drop, high velocity, or low velocity. h. Access to the area. i. Minimum drop zone dimensions. j. Maximum percent of slope for drop zones is 30 percent.

2.

Additionally, the lAs must consider the following factors: a. Hazardous surface conditions. b. Potential approaches and exits. c. Proximity to mission objective. d. Enemy disposition. e. Alternate landing zones. f. Supporting fire (in coordination with the G3 and fire support element (FSE).

PART B: DROP ZONE COMPUTATIONS

1. The request for DZ identification will usually include the rate of speed the aircraft will fly over the proposed area and the amount of time available. Furthermore, you will be informed as to the prevailing wind velocity and wind direction which has an impact on the ground speed.

When the wind velocity at the delivery altitude cannot be determined, use the aircraft's air speed as the ground speed. Use the steps outlined in the following paragraphs in computing the DZ size. Additionally you must

IT0637

2

consider percent of slope (Part C of this lesson), surface and obstacles (Part D), and DZ accessibility (Part E).

NOTE: 2.

It is desirable to fly aircraft into the wind during air delivery because the slower ground speed gives more time over the DZ and assures a more compact delivery.

Compute minimum required DZ length.

a. The minimum required DZ length should be computed by multiplying the ground speed of the aircraft by the time needed to release its cargo. b. Length computation formula: D = R x T. D S R .51 T

= = = = =

DZ length (in meters(m)) Aircraft speed in knots Ground speed of aircraft: S x .51 Conversion factor of knots to meters per second Time required for aircraft to release its cargo and personnel.

c. Compute Ground Speed R. (1) Add tail wind speed to aircraft speed, or (2) Subtract headwind speed from aircraft speed (Figure 1-1).

Figure 1-1. Considering Prevailing Wind Speed.

(3) Convert knots to meters per second by multiplying aircraft speed by .51. Result is ground speed R in meters per second. d. Calculate drop zone length D by multiplying R x T. Result is length of drop zone D (in meters).

NOTE: Always round UP the required DZ length to the nearest meter.

3

IT0637

For example: If the aircraft speed is 110 knots, head wind is 20 knots, and drop time is 20 seconds, the required length of the DZ is: D = R x .51 x T D = (110 - 20) x .51 x 20 = 918m.

3. Compute required DZ width. The required DZ width depends upon the method and/or type of air drop, wind drift, and formation of the aircraft, which is usually provided in the request.

When it is not specified, you must give the requester the widths of all proposed DZs that meet the length requirements. a. The wind drift formula is used to determine the minimum required width of a DZ. In this formula, K is a constant that represents the characteristic drift of a parachute of a certain model. b. Wind drift formula: (1)

D= KxAxV D = Width of DZ (in meters) K = 4.1 (constant) for personnel parachutes 2.6 (constant) for all other parachutes V = Velocity of surface wind (in knots) A = Altitude of aircraft (in hundreds of feet).

(2) For example: D = K x A x V K = 2.6 (G-13 cargo parachutes) V = 11 knots A = (2,000ft รท 100) = 20 D = 2.6 x 11 x 20 = 572m.

NOTE: Always round the required DZ width UP to the nearest meter.

4. Using your PI or equivalent scale, you should measure the potential DZ length on the imagery (or the map if imagery is not available) and then compute the ground distance (GD) in meters. a. Imagery length computation formula: GD = PD x DPRF. b. Map length computation formula: GD = MD x DMRF. GD = Ground distance (length) in meters PD = Photo distance (in feet) DPRF = Denominator of the photo representative fraction 3048 = Conversion factor of feet to meters MD = Map distance DMRF = Denominator of the map representative fraction Scale = 1 : DPRF or DMRF.

IT0637

4

c. For example: PD = .06ft DPRF = 25,000 GD = .06ft x 25,000 x .3048 = 457.2m = 457m or MD = .03ft DMRF = 50,000 GD = .03ft x 50,000 x .3048 = 457.2 = 457m.

NOTE: Always round the potential DZ length DOWN to the nearest meter.

5. In the next step you should measure the potential DZ width on the imagery (or the map if imagery is not available) and then compute the ground distance in meters. a. Imagery width computation formula: GD = PD x DPRF b. Map width computation formula: GD = MD x DMRF c. For example: PD = .04ft DPRF = 25,000 .3048 = Conversion factor of feet to meters GD = .04ft x 25,000 x .3048 = 304.8m = 304m or MD = .02ft DMRF = 50,000 GD = .02 x 50,000 x .3048 = 304.8 = 304m.

NOTE: Always round the potential DZ width DOWN to the nearest meter.

6. In those cases where the plot of the potential DZ is irregular in shape, the lengths and widths will be determined as shown in the following sketch (Figure 1-2). Note the usable length is measured along a centerline while width used is the minimum dimension of the plotted area with ends perpendicular to the centerline. Width is 140m in this example, and length is 380m.

Figure 1-2. Irregular-shaped DZ.

5

IT0637

7. Compute flight time. A DZ should be as large or larger than the commander's specific request; this is due to safe landing requirements. Normally an area 460m long and 180m wide is the minimum requirement for the delivery of supplies. If a DZ of the desired length is not available, the flight time over the DZ (whatever its length) must be computed to determine how much of the load can be released in one pass and/or how many passes must be made to release the entire load. a. Flight time computation formula: T= T= D= R= .51 =

D__ R x.51 Time over the DZ Length of the DZ Ground speed Conversion factor of knots to meters per second.

b. For example: D = 150m R = 105 knots x .51 = 53.55 = 53m/seconds T=

150___ (105 x .51)

= 150 = 2.83 = 2 seconds.

53

NOTE: Always round the flight time DOWN to the next lower whole second.

PART C: PERCENT OF SLOPE COMPUTATIONS 1. After the DZ area has been determined, you must compute the percent of slope. For this factor you need a map of the area. The slope of a DZ should not be more than 30 percent. Use the following formula to compute the terrain's percent of slope: SL = VD x 100 HD SL = Percent of slope VD = Vertical distance of the DZ (altitude difference between each end of the DZ length) HD = Horizontal distance of the DZ 100 = Conversion factor for percent.

NOTE:

Both VD and HD must use the same unit of measurement (feet or meters). Use 3.281 as the conversion factor from meters to feet or .3048 to convert feet to meters.

a. For example: If the length of the DZ is 900m, one end of which is at an altitude of 150ft and the other end at 200ft; the percent of slope is 1.7 percent, rounded up to 2%.

SL =

(200 - 150)__ (900 x 3.281)

x 100 = 1.7% = 2%.

REMEMBER: Always round UP the percent of slope to the nearest percent.

IT0637

6

b. The contour intervals on maps are in feet or meters. The bar scales are usually in meters, yards, statute miles, or nautical miles. If you use the bar scale, you may have to convert yards to feet (1 yard = 3ft). If you use your PI scale, be sure to multiply your measurements by the map scale.

2. The following example will lead you through the basic steps in determining percent of slope using a map. Use the map extract (Figure 1-3) to compute the percent of slope.

Figure 1-3. Map Extract (not to scale). a. Step 1: Determine the elevation of each point. Neither point is on a contour line, so it will be necessary to interpolate. Point Y is located on an intermittent stream symbol, which could 'be confused with a contour line if care is not taken. The contour interval is 50ft. b. Step 2: Measure the distance between points X and Y, using a piece of paper, PI scale, or boxwood scale. Make your measurements from the center of one dot to the center of the other dot (Figure 1-4).

Figure 1-4. Measuring from Dot to Dot (Map not to Scale).

7

IT0637

NOTE:

For instructional purposes, use the metric side of the boxwood scale from your PI kit.

It would have been easier to use the .001 foot scale and thus have all variables in the same unit of measure. You may want to use the tube magnifier to exactly align the scale with the centers of the two points in order to more accurately read the distance found.

(1) As you can see in Figure 1-4, the map distance (MD) is 2.95 centimeters (cm). GD is found by solving the following formula: GD = MD x DMRF, the latter of which is 50,000 GD = 2.95cm x 50,000 = 147,500cm = 1,475m.

(2) In comparing elevations and horizontal distance, we find the elevation is in feet and distance in meters, so we must convert one or the other. For the purpose of this requirement, convert the horizontal distance to feet.

GD = 1,475m x 3.281 = 4,839.475; rounded up to 4,840ft. c. Step 3: Use the percent of slope formula. VD = change in elevation from Point X to Point Y. SL = VD = X - Y x 100 HD HD SL = 5,925ft - 5,475ft x 100 4,840ft SL = 450 x 100 = 9.2975; rounded up to 10% 4,840 SL = 10%.

3. Aerial imagery is of significant value for percent of slope determinations. Maps do not show small or new features constructed after the date of the map. a. For this problem, use the Sunnyside stereopair (Figure 1-5), the Sunnyside photo (in back of the Subcourse booklet), and the map extract (Figure 1-6). The photo scale is 1: 32,600 (DPRF = 32,600). Compute the percent of slope from the road/trail junction at point X to the road junction at point Y. Remember when working with imagery you should at first transfer the points on the imagery to the same locations of the map. This has already been done for you.

IT0637

8

Figure 1-5. Stereopair--Sunnyside.

9

IT0637

Figure 1-6. Map Extract--Sunnyside, AZ 1:50,000.

IT0637

10

b. A tip which may be of help, not only in solving this particular problem, but also in future similar situations, is to consider the comparative scales of the imagery and the map. The photo scale is 1: 32,600 and the map scale is 1: 50,000. Measuring the distance between annotations X and Y on the imagery will give you a straight line distance of 8.5cm. Using the following formula, you can determine the approximate distance between points X and Y. MD = PD x DPRF DMRF MD = 8.5cm x 32,600 50,000 MD = 8.5cm x 0.652 MD = 5.542cm; rounded up to 5.6cm. c. Next, measure on the map extract from point X northward along the road to point Y, which is 5.4cm. Now, obtain the vertical distance. Bring the vertical distance to the same unit of measure as the horizontal distance and multiply it by 100 to obtain the percent of slope. Your result should be: SL = VD x 100 HD SL = 168ft x .3048 (x 100).

5.4cm x 50,000 NOTE: To convert centimeters to meters divide centimeters by 100.

SL = 51.2064m x 100 = 1.8965 rounded up to 2%, or +2% for the 2,700m inclined slope.

PART D: SURFACE AND OBSTACLE CONSIDERATIONS 1. When both size and slope of a proposed DZ are acceptable, inspect imagery of the area for potentially hazardous ground surface conditions and the presence of obstacles. This requires examination of photography in stereoscopic pairs as well as a review of available maps. a. Protect troops from injury during a drop. b. Prevent the unsuccessful drop of equipment.

2. Unfavorable or hazardous surface conditions are normally provided by the terrain detachment, to include information on:

11

IT0637

* Water. * Marshland. * Gullies. * Drop-offs (cliffs). * Dense trees. * Dense low vegetation. * Large rocks.

3.

Obstacles are manmade features, such as: * Power lines and poles. * Buildings. * Towers. * Fences. * Military impediments (i.e., punji stakes, barriers, barbed wire, etc.).

NOTE: The most acceptable troop DZ is a flat, resilient surface without obstructions.

PART E: DROP ZONE ACCESSIBILITY 1. A favorable DZ must have accessibility. Accessibility means available ground approaches and exits (in and out) of the DZ. If possible, DZ's near lines of communication (LOCs), such as roads, railroads, canals, and so on, should be selected.

2. Certain questions must be answered before identification can occur. The tactical situation will add other questions, however, these will always need to be answered: a. Will the approach involve more or less troops/equipment than the exit? b. Will the exit involve more or less troops/equipment than the approach? c. Will the approach/exit occur during daylight or night?

IT0637

12

3. When troops are parachuted into an area, it is most important they have an easy exit from the DZ area, preferable in the general direction which will support their ground tactical plan.

When supplies or equipment comprise the load, personnel on the ground must be able to approach the area, recover the material, and then exit with the material. For example, if wheeled vehicles were parachuted into a DZ, the troops already on the ground may be able to approach the DZ on foot through a densely wooded area or up a steep slope. However, the vehicles may not be able to exit through the forest or negotiate the slope. When evaluating a potential DZ area for accessibility, the type of load will be a major consideration.

4. Another item, related to accessibility, we need to look for in a potential DZ area, is the trafficability of the soil. Swampy soil, or in some cases even fine sand, may rule out the selection of a DZ in that parachuted equipment may bog down, or troops may not be able to approach or exit the area rapidly. Therefore, trafficability of access routes must be considered to afford easy cross-country movement of vehicles and personnel in and out of the DZ. PART F: DROP ZONE REPORTS AND OVERLAYS 1. Normally, the IA prepares a report in accordance with local SOP. Furthermore, the IA selects a primary DZ and alternate DZs to the collection management officer (CMO) who in turn recommends these to the G2 and the commander to satisfy the PIR. 2. Upon request the IA will prepare an overlay of the primary and alternate DZs (Figure 1-7).

If the situation permits, a terrain analyst will prepare this overlay.

Figure 1-7. DZ Overlay.

13

IT0637

LESSON 1 PRACTICE EXERCISE The following material will test your grasp of the material covered in this lesson. There is only one correct answer for each item. When you have completed the exercise, check your answers with the answer key that follows. If you answer any item incorrectly, study again that part of the lesson which contains the portion involved.

1.

Using the following data, compute the required length of the DZ; aircraft speed = 125 knots, headwind = 10 knots, time required to complete the drop = 30 seconds.

A. 175.9m.

B. 1,759.5m.

C. 1,760m.

D. 1,800m.

2.

Using the following data, compute the potential DZ width in meters; PD = .075ft, DPRF = 25,000.

A. 571m.

B. 1,875m.

C. 5,715m.

D. 6,152m.

3.

Using the following data, compute the percent of slope for a DZ with an elevation of 300ft at one end and 150ft at the other end, and a horizontal distance of 2,000ft.

A. 2%.

B. 4%.

C. 7.5%.

D. 8%.

IT0637

14

4.

When evaluating a potential DZ for accessibility, what will be a major consideration?

A. Aircraft used for drop.

B. Type of load.

C. Supplies.

D. Slope.

5.

Using the ISLA DE VIEQUES map sheet (contour interval 20m) and the map extract (Figure 1-8), determine which of the DZs (A, B, C, or D) is most suitable for parachute delivery of food and ammunition, based on the following mission request: Air speed is 115 knots with head wind of 10 knots, from 2700, time required to make the drop will be 15 seconds.

Figure 1-8. Map Extract.

15

IT0637

LESSON 1 PRACTICE EXERCISE ANSWER KEY AND FEEDBACK Item

Correct Answer and Feedback

1.

C. Using the formula D = R x .51 x T, rate of aircraft speed R = 125 knots - 10 knots headwind = 115 knots x conversion factor of knots to meters .51 x time required to complete the drop.

T = 30 seconds = 115 x .51 x 30 = 1,759.5m, rounded up to 1,760m (page 3, para 2).

2.

A. Using the formula GD = PD x DPRF, the potential DZ width GD = .075 x 25,000 = 571.5m, rounded down to 571m (page 5, para 5).

3.

C. Using the formula SL = VD x 100, elevation at one end = HD 300ft, HD elevation at the other end is 150ft, SL = VD (300-150ft) x 100 HD (2,000ft) SL = 150 x 100 2,000 SL = 7.5% rounded up = 8% (page 6, para 1).

4.

B. Type of load will be a major consideration when evaluating a potential DZ for accessibility (page 13, para 3).

5.

a. DZ "D" is most suitable, since it is long and wide enough; percent of slope is less than 15%; there is little vegetation, and it is easily accessible. With the forecast of headwinds of 10 knots from 2700, the aircraft flying east to west over the DZ, the required length of the DZ is 810m; DZ "D" is approximately 860m x 375m (pages 2 through 13). b. DZ "A" is not suitable because of excessive slope and it is too short (700m x 350m). c. DZ "B" is not suitable because it is neither long enough nor wide enough (580m x 300m). d. DZ "C" is not suitable because of excessive slope (nearly 35%), rugged terrain, and dense vegetation; however, the DZ is

880m x 440m.

IT0637

16

LESSON 2 HELICOPTER LANDING ZONE SELECTION MOS Manual Tasks: 301-338-2803 301-338-3701 OVERVIEW TASK DESCRIPTION: In this lesson you will learn to describe the general classification and criteria; compute area size and percent of slope; identify hazardous surface conditions and obstacles, approaches, and exits; and determine accessibility for HLZs in the AO. LEARNING OBJECTIVE: ACTIONS:

Describe the information and procedures required to select an HLZ.

CONDITIONS:

You will be given access to extracts from FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

STANDARDS:

HLZs will be selected in accordance with FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

REFERENCES:

The material contained in this lesson were derived from the following publications: FM 5-34 FM 30-10 FM 57-38 STP 34-96D24-SM-TG. INTRODUCTION

lAs at the CM&D section will identify a primary HLZ and alternate HLZs and provide these to the ground unit commander, who in coordination with the supporting aviation unit commander, will select the final location of the HLZ to best support the ground tactical plan.

PART A: CLASSIFICATION OF HELICOPTER LANDING ZONES 1. Heliports in the theater of operations are classified by the military area in which they are located and by the category of helicopters intended to use them. For landing area classification the theater of operations is divided into the following areas: a. The battlefield area is normally under control of a brigade.

17

IT0637

b. The forward area is immediately behind the battlefield area and normally under control of a division or brigade. c. The support area is behind the forward area and normally in the corps rear area or the area under the control of the fighter air support command. d. The rear area is behind the support area and normally in the army service area of communications zone.

2. Helicopter Categories: The following helicopters were designated as controlling aircraft to establish the limiting geometric and surface strength requirements of helipads and heliports. a. Observation helicopter (OH-6A/OH-58). b. Attack helicopter (AH-1G/AH-64). c. Utility helicopter (UH-1D). d. Cargo helicopter (CH-47) (medium lift). e. Cargo helicopter (CH-54) (heavy lift).

PART B: GENERAL HELICOPTER LANDING ZONE CRITERIA 1. HLZs in the battlefield area are considered landing zones of opportunity. In selecting HLZ from maps, aerial photographs, and actual ground or aerial reconnaissance, the same criteria used for determining a DZ apply. Additional information, normally supplied by the aviation unit commander, should be used when selecting an HLZ. Information should include the type HLZ and type and number of helicopter to be used.

2.

HLZs have the following specifications:

a. A HLZ is a helicopter landing area that encompasses one or more helicopter landing sites. b. A helicopter landing site is a subdivision of a HLZ. The size of a landing site depends on the number of landing points (LPs) within it and the size of the LPs. c. A LP is a designated or selected touchdown point where a single helicopter lands. A touchdown area marker is essential to provide a visual reference for depth perception and also to reduce the effect of white-out (Figure 2-1).

IT0637

18

Figure 2-1. Touchdown Area Marker.

3. HLZ dimensions. As previously stated, the size of the landing site will depend on the number of LPs within it, and the size of these LPs. As a guide, a helicopter requires a relatively level, cleared, circular area of 20 - 75m in diameter for landing depending on the type of helicopter.

Generally speaking, a helicopter requires more usable landing area at night than during the day.

The criteria provided in Figures 2-2 through 2-4 represents guidance on LP preparation.

Helicopter units will designate the size, small, medium or large, to be utilized by their units for specific operations. Numerous considerations such as helicopter type, unit proficiency, nature of loads, and climatological conditions may apply to size of LPs utilized. General distance between LPs within a landing site in daytime landing are as follows (measured center to center): o Small landing points

80ft/25m.

o Medium landing points

115ft/35m.

o Large landing points

165ft/50m.

Figure 2-2. Small Landing Point Dimensions.

19

IT0637

Figure 2-3. Medium Landing Point Dimensions.

Figure 2-4. Large Landing Point Dimensions. a. Minimum recommended daytime LP dimensions for helicopters in formation are shown in Table 2-1. Length is shown from front to rear, width from side to side or laterally.

Table 2-1. Minimum Recommended Daytime LP Dimensions.

b. Minimum and maximum recommended nighttime LP dimensions for helicopters in formation are shown in Table 2-2.

IT0637

20

Table 2-2. Minimum and Maximum Recommended Nighttime LP Dimensions.

NOTE: Most helicopters cannot land or take off vertically when they are fully loaded; therefore, a larger area or a better approach is needed. c. Landing formations. Whenever possible, helicopters should land simultaneously in the same formation in which they are flying. These formations can be in a string, strip, trail, diamond, vee, heavy left, heavy right, slingload etc. If necessary, you need to select an additional HLZ. Various nighttime HLZs are shown in Figures 2-5 through 2-9).

4. The supporting aviation unit commander has the final authority in establishing the landing area criteria for assigned helicopters in daytime and nighttime missions. This may change from time to time, depending on how heavily loaded the aircraft will be, the place of landing, the time of landing, and the anticipated weather conditions. For example, the area requirement may be larger-a. For a heavily loaded helicopter. b. For a helicopter whose cargo is sling loaded. c. When landing must be made at night or during other periods of reduced visibility. d. When there are terrain obstructions or obstacles in the area. e. When an area is located at high elevation. f. When temperature is hot or when humidity is low.

NOTE: The aviation commander should provide the IA with required dimensions for all HLZs based on various flight and landing formations. This action will assist the IA in computing HLZ sizes.

21

IT0637

Figure 2-5. Standard Flight and Landing Formations.

IT0637

22

Figure 2-6. Night UH-1 Landing Site--Diamond Formation.

23

IT0637

Figure 2-7. Night UH-1 Landing Site, Flights Heavy Left Formation.

IT0637

24

Figure 2-8. Night CH-47 Landing Site, Flights Heavy Left Formation.

25

IT0637

Figure 2-9. Night CH-47 Sling load Pickup and/or Drop Zone.

IT0637

26

PART C: HELICOPTER LANDING ZONE COMPUTATIONS 1. In determining the HLZ area size, you can proceed in the same manner as you did for the DZ area by first computing the required and then the potential HLZ areas. However, you can also first compute the potential and then the required HLZ areas. You should do the latter when you want to find out how many helicopters will be able to land in a potential HLZ. 2..

Use the following procedure in determining the HLZ area: a. Potential HLZ length = GD = PD x DPRF when measuring imagery. or GD = MD x DMRF when measuring on a map.

For example:

PD = .094ft and DPRF = 10,000 GD = .094ft x 10,000 = 940ft

b. Potential HLZ width = GD = PD x DPRF or GD = MD x DMRF For example:

PD = .0372ft and DPRF = 10,000 GD = .0372ft x 10,000 = 372ft

NOTE: For potential HLZ length and width, if your results are in fractions, you should round DOWN to the nearest foot or meter. Use the same basis for all measurements (either feet or meters). c. Determine how many H-64 helicopters can land in the potential HLZ area in a two trail formation during daytime.

(1) Determine the minimum recommended LP dimensions by using Tables 2-1 and 2-2.

For example: The minimum recommended daytime LP for 1 x AH-64 = 31m from front to rear and 31m laterally (Table 2-1). Since we are using feet, you should convert 31m to feet; 31m x 3.281 = 101.71ft = 102ft.

NOTE: You should round UP converted LP dimensions.

(2) Determine the number of LPs (or helicopters) from front to rear of the potential HLZ by using the formula: # LPs from front to rear = Potential HLZ length Minimum recommended LP length For example: # LPs from front to rear = 940ft 102ft = 9.21 = 9 LPs or 9 x AH-64 can land from front to rear.

NOTE: You should always round DOWN number of helicopters.

27

IT0637

(3) Determine the number of lateral LPs of the potential HLZ by using the formula: # lateral LPs = Potential HLZ width Minimum recommended LP width For example: # lateral LPs = 372ft 102ft = 3.64 = 3 LPs or 3 x AH-64 can land laterally.

(4) Determine the total number of helicopters (LPs) of the potential HLZ by using the formula: Total # helicopter LPs = # of LPs (or helicopters) from front to rear x # of lateral LPs (or helicopters) For example: 9 x 3 = 27 helicopters.

NOTE: Use the same procedure in determining the potential HLZ for a nighttime mission.

Ensure you use the minimum recommended LP dimensions for nighttime.

PART D: PERCENT OF SLOPE COMPUTATIONS 1. The percent of slope for an HLZ should not exceed 7째 or 8% if the helicopter is to land.

However at the pilot's discretion it may be possible for a helicopter to hover just in contact with the ground on slopes greater than 7째 or 8%. a. When you compute the percent of slope, do not depend entirely on the map. Study the area on imagery, too. The map contour intervals may indicate that the percent of slope is sufficient, but sloping or rugged terrain can be seen only with a stereoscope. b. When the percent of slope is greater than the allowable 8%, report this to the requester.

The site may still be usable if the commander chooses to hover the aircraft and load/unload troops and supplies by rope or ladder. When the slope is more than 8%, provide the requester with the exact percent figure as this can affect operations. This is important because when the ground slope is less than 8%, helicopters should be landed up-slope. When the slope is more than 8%, helicopters may be landed side-slope (Figure 2-10). c. Now you are ready to compute the percent of slope of each potential HLZ. Do this the same way as the DZ's using the formula: SL = VD x 100 HD

IT0637

28

Figure 2-10. Helicopter Landing on Side-slope and Up-slope.

2.

Furthermore, when you compute the HLZ percent of slope, consider the following: a. Direction of positive slope. This is important for the approach and exit direction. b. Number of aircraft used. This will be provided by the aviation unit commander.

c. Landing formation. Planned landing formation may require modification in order to allow helicopters to land in restricted areas. Whenever possible, it is desirable to land aircraft in the same formation they were flying (Figures 2-5 through 2-9). Furthermore, front to rear and lateral touchdown requirements must be considered; these will be provided by the aviation unit. d. Altitude density. The density is determined by the altitude, temperature, and humidity.

For planning purposes, as density increases, the landing area should increase proportionately. e. Approach/departure directions. Whenever possible, approach/departure should be into the wind. However, if there is only one suitable approach direction due to obstacles or the tactical situation, or if it is desired to make maximum use of the available HLZ, most aircraft can land with a crosswind (10 knots or less) or a tailwind (5 knots or less). The same considerations apply to departures from the HLZ. f. Loads. Remember, that when fully loaded, most helicopters cannot ascend or descend vertically.

29

IT0637

PART E: SURFACE AND OBSTACLE CONSIDERATIONS 1. You need current aerial imagery, preferably stereopairs as well as a review of current maps of the area. In addition to a percent of slope greater than 8%, you should identify unfavorable surface conditions and obstacles and their location in the same manner as for DZs. All unmovable obstacles must be clearly marked on your overlay and reported to the requester.

2. The surface of the center of the LP must be even and sufficiently firm to allow a fully loaded helicopter (1/4 ton for light helicopter, 3 tons for larger helicopters) to stop and start without sinking. The whole LP must be cleared of trees, brush, stumps any loose material or piles of dust or sand which could be blown up by the rotors of the helicopter. LPs with sandy or dusty surfaces should be stabilized or covered with metal mats. Any snow on any LP should be packed or removed to reveal any hazardous objects and reduce the proportion of blowing snow.

3. The HLZ may be usable even if there are tall obstacles in the area, such as trees or buildings, provided the aviator has a 10 to 1 clearance ratio for both approach and exit; for example: If a tower is 60ft high, the aviator needs 600ft to clear it.

Required clearance = 10 (Horizontal clearance) to 1 (Obstacle height) = 10 x 60ft = 600ft.

4. When you identify an obstacle in or near an HLZ, provide the requestor with this information: a. A description of the obstacle and its location. b. Suggested approach to and exit from the area to clear the obstacles.

PART F: HELICOPTER LANDING ZONE ACCESSIBILITY Approach and landing should be made over the lowest obstacles and generally into the wind. If possible, HLZs near LOCs (roads, trails, rivers) should be selected, to provide easy exit from the area.

PART G: HELICOPTER LANDING ZONE OVERLAYS Upon request the IA will prepare an overlay of the primary and alternate HLZ. This overlay will be similar to the one prepared for a DZ. Situation and time permitting, this overlay will be prepared by a terrain analyst.

IT0637

30

LESSON 2 PRACTICE EXERCISE The following material will test your grasp of the material covered in this lesson. There is only one correct answer for each item. When you have completed the exercise, check your answers with the answer key that follows. If you answer any item incorrectly, study again that part of the lesson which contains the portion involved.

1.

Who will select the final location of the HLZ? A. IA. B. Ground unit commander.

C. Aviation unit commander.

D. CM&D collection manager.

2.

What is the minimum recommended LP for one UH-1D helicopter in formation in a daytime mission?

A. 20m x 20m.

B. 30m x 30m.

C. 31m x 31m.

D. 40m x 40m.

3.

At how many percent slope should a helicopter be landed up slope?

A. Less than 8%.

B. Less than 10%.

C. Less than 12%.

D. Less than 15&.

31

IT0637

4.

What is the maximum crosswind factor for a helicopter in the approach to land safely?

A. 5 knots.

B. 7 knots.

C. 10 knots.

D. 15 knots.

5.

How many feet clearance are required for a CH-47 helicopter to land where a light pole stands 35ft tall near the landing point?

A. 35ft.

B. 70ft.

C. 135ft.

D. 350ft.

6.

How many CH-47 helicopters can land in an area 1,000ft x 400ft at nighttime using maximum LP dimensions?

A. 4.

B. 5.

C. 6.

D. 10.

7.

Using the ISLA DE VIEQUEZ map sheet, stereopair 1 (in back of the subcourse booklet) the map extract (Figure 2-11), the checklist and following situation (Table 2-3), determine the best suitable and alternate HLZs.

Situation:

The enemy established a POW compound at KR 37850286 west of Esperanza with 12 x US POWs. Highway 997 was cut east and west of Esperanza. The forward line of own troops (FLOT) is located approximately 3 1/2 kilometers (km) west of Esperanza. Prevailing winds are from E at 3 knots.

Tasking:

IAW operations order (OPORD) 1-1 the 1st US Air Assault Squadron is tasked to land with 14 x UH-1D helicopters within 3km of the objective at night and liberate our soldiers.

IT0637

32

Table 2-3. HLZ Checklist.

Figure 2-11. Map Extract.

33

IT0637

LESSON 2 PRACTICE EXERCISE ANSWER KEY AND FEEDBACK Item

Correct Answer and Feedback

1.

B. The ground unit commander will select the final location of the HLZ (page 21, para 4).

2.

C. The recommended landing area for UH-1D helicopters in formation in a daytime mission is 31m x 31m (page 20, Table 2-1).

3.

A. At less than 8% slope a helicopter should be landed up slope (page 29, fig 2-10).

4.

C. A helicopter can land safely at a maximum crosswind of 10 knots (page 29, para 2e).

5.

D. At the prescribed 10 to 1 clearance ratio, the CH-47 helicopter must have 350ft clearance to land safely (page 30, para 3, part E).

6.

A. 4 x CH-47 helicopters can land safely at nighttime at the 1,000 x 400ft HLZ; first you must convert the required 75m front to rear clearance for a CH-47 (page 21, Table 2-2) to feet, 75 x 3.281 = 247ft; 4 x CH-47 helicopters can land front to rear; however, only 1 x CH-47 helicopter can land laterally (unless the width would be 494ft) (pages 27-28, part C).

7.

Area No. 1 should be recommended as the night HLZ because of its proximity to the objective, its length is maximized due to the wind conditions, and there is a good road leading from the HLZ to the POW compound and highway 201. The approach direction should be from the W. Area No. 2 is too small for use as a night HLZ. Area No. 3 is too far from the objectives. Area No. 4 should not be selected because of the lack of a well defined route to the objective. Area No. 5 is not suitable because of percent of slope restrictions (pages 20-30).

NOTE:

Tactics as well as landing area considerations, i.e., size, surface conditions, and approach/exit directions come into play.

NOTE:

In evaluating the areas you should have developed similar basic information as shown in the checklist (Table 2-4).

IT0637

34

Table 2-4. Completed HLZ Checklist.

35

IT0637

LESSON 3 AIRPLANE LANDING ZONE SELECTION MOS Manual Tasks: 301-338-2803 301-338-3701 OVERVIEW TASK DESCRIPTION: In this lesson you will learn to describe the classification and general criteria, compute area size and percent of slope, consider unfavorable surfaces and obstacles, and determine accessibility for a potential ALZ in the AO. LEARNING OBJECTIVE: ACTIONS:

Describe the information and procedures required to select potential ALZ.

CONDITIONS:

You will be given access to extracts from FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

STANDARDS:

Potential ALZs will be selected in accordance with FM 5-34, FM 30-10, FM 57-38, and STP 34-96D24-SM-TG.

REFERENCES:

The material contained in this lesson was derived from the following publications: FM 5-34.

FM 30-10.

FM 57-38.

STP 34-96D24-SM-TG. INTRODUCTION

An ALZ (also referred to as runway or landing strip or a fixed wing landing area (FWLA)) is a specified location within an objective area used for landing aircraft. Potential ALZs are selected to meet the requirements of the supported ground and using aviation unit. IAs at the CM&D section will select potential ALZ locations based on aerial imagery and current maps.

PART A: CLASSIFICATION OF AIRPLANE LANDING ZONES ALZs in the theater of operations are classified by military areas in which they are located similar to HLZs. Controlling aircraft classifications are assigned six categories which include all fixed wing aircraft in the current military inventory. A controlling aircraft, or 36

IT0637

a combination of controlling aircraft, has been designated for each category to establish the limiting geometric and surface strength requirements of the airfield. The categories and associated controlling aircraft are: a. Liaison (0-1A). b. Surveillance (OV-1). c. Light lift (C-7A). d. Medium lift (C-130). e. Heavy lift (C-124, C-135, and C-141). f. Tactical (F-4C and F-1.05).

PART B: GENERAL AIRPLANE LANDING ZONE CRITERIA 1. An ALZ is established so Army aircraft can safely land and take off. It also provides guidance for aircraft taxiing and parking while they are on the ground. It has one or more landing strips. The landing strip consists of a runway and may include taxiways, parking points, and dispersal areas.

2. Selection of a potential ALZ depends on the type aircraft, runway dimension requirements (Table 3-1), surface, and location. These specifications are normally furnished by the concerned aviation unit commander.

3. There are three types of ALZs. They are classified according to their size and degree of improvement: a. A Pioneer landing strip usually has an unimproved runway and is normally used for fair weather operations only. This air strip has the following characteristics: (1) Minimum length: 1,200ft.

(2) Minimum width: 50ft.

(3) Minimum lateral clearance: 75ft on each side of runway centerline.

(4) Taxiways and parking areas: Not normally required.

37

IT0637

Table 3-1. Runway Dimension Requirements.

b. A hasty landing strip also has an unimproved surface, which is normally acceptable for marginal weather, but is unusable during prolonged periods of poor weather. After a period of occupation, most pioneer landing strips (terrain permitting) can be improved to meet the requirements of a hasty landing strip. This strip has the following characteristics: (1) Minimum length: 1,200ft, plus a 10% overrun at each end.

(2) Minimum width: 50ft plus a 10-ft shoulder on each side.

(3) Minimum lateral clearance: 100ft on each side of runway centerline.

(4) Has taxiways, parking areas and may include dispersal areas. c. Deliberate. A deliberate landing strip has an all-weather capability. As a minimum, it should have all the characteristics of a hasty landing strip, plus any other facilities needed to meet the

38

IT0637

standards required by any aircraft. A deliberate strip is usually a permanent installation with a control tower, hard surface runways, taxiways, and parking ramps.

PART C: AIRPLANE LANDING ZONE COMPUTATIONS In computing the area size you should determine the length and width of the area, followed by identifying the potential airfield by type. a. For determining the length and width use the same formula as for measuring a DZ or HLZ. Length (or width): GD = PD x DPRF or GD = MD x DMRF b. Identify the potential ALZ by type, for example, if the photo scale is 1:20,000, the photo distance (length) is .08ft and the photo distance (width) is .004ft, then the potential ALZ could be either a hasty or deliberate type, depending on construction and facilities.

PART D: PERCENT OF SLOPE COMPUTATIONS In computing the percent of slope (SL), use the same formula as for computing SL of a DZ or HLZ: SL = VD x 100 HD NOTE: The maximum slope for a potential ALZ should not exceed 10%.

REMEMBER: Always round UP percent of slope to the nearest percent.

PART E: SURFACE AND OBSTACLE CONSIDERATIONS The surface of a potential ALZ must be firm and smooth enough to allow heavily loaded aircraft to land, taxi, park, and take off without delay or damage to the aircraft. It should be located away from obstacles such as mountains, telephone wires, tall buildings, and trees. The area should be free of heavy rocks and stumps so that troops can clear it easily. This is particularly important for pioneer and hasty strips which may have to be established quickly. The area should be dry as water or marshland can cause early erosion.

PART F: AIRPLANE LANDING ZONE ACCESSIBILITY 1. Location. An ALZ should have convenient access to and from the areas, such as roadways or other level terrain. If there are prevailing winds, the runway should be oriented, if possible, so that aircraft can land and take off into the wind.

39

IT0637

2. The minimum size of an ALZ depends on the type of loads, the direction and velocity of winds, and the condition of the ground. Consider the following factors in establishing a ALZ: a. Soft, wet, slippery, or any other unfavorable surface conditions will increase the length of the landing zone by at least 7%. b. Crosswinds may require an increase in width of the landing zone by at least 7%. c. Uphill take off and downhill landings may require longer runways. The maximum slope on any ALZ should not exceed 10%. d. If there are obstacles at the approach and departure ends of the ALZ, obstacle clearance is measured from the obstacle to the approach and departure end. You should ensure a 10: 1 clearance ratio is obtained (same as used for an HLZ).

PART G: AIRPLANE LANDING ZONE OVERLAYS Upon request the IA will prepare an overlay of the potential primary ALZ and an alternate ALZ if deemed necessary (Figure 3-1). A relief and drainage overlay may also be provided (Figure 32). ALZs are normally referred to by their nickname or a color. Situation and time permitting, this overlay will be prepared by a terrain analyst if assigned.

40

IT0637

Figure 3-1. Proposed ALZ "Green."

41

IT0637

Figure 3-2. Relief and Drainage Overlay.

42

IT0637

LESSON 3 PRACTICE EXERCISE The following material will test your grasp of the material covered in this lesson. There is only one correct answer for each item. When you have completed the exercise, check your answers with the answer key that follows. If you answer any item incorrectly, study again that part of the lesson which contains the portion involved.

1.

Which ALZ has an unimproved runway and is used in fair weather only?

A. Deliberate.

B. Hasty.

C. Pioneer.

D. Strategic.

2.

What can cause early erosion to an ALZ? A. Dry ground.

B. Water.

C. Rocks.

D. Aircraft.

3.

Which of the following is required for an ALZ? A. Convenient access.

B Obstacles.

C. Prevailing winds.

D. Wind velocity.

43

IT0637

4. Using the ISLA DE VIEQUEZ map sheet and the map extract (Figure 3-3), determine the ALZ suitability of potential pioneer ALZs marked A, B, C, and D. Rank these proposed ALZs by priority.

Figure 3-3. Map Extract.

44

IT0637

LESSON 3 PRACTICE EXERCISE ANSWER KEY AND FEEDBACK Item

Correct Answer and Feedback

1.

C. The pioneer ALZ has an unimproved runway and is used in fair weather only (page 38, para 3a).

2.

B. Water or marshland can cause early erosion to an ALZ (page 39, part E).

3.

A. An ALZ must have convenient access (page 39, para 1, part F).

4.

"A" should be selected as best potential pioneer ALZ due to its length (1,685ft), less than 1% slope, and lack of obstacles in the approach and exit directions. Additionally, its size would lend itself to relatively easy upgrading to a hasty ALZ. The only disadvantages found are the few scattered trees and its elevation of less than 5m, which in inclement weather might cause the soil to be slippery and of poor stability. Remember, however, that pioneer ALZ do not require other than fair weather operation (pages 37-40).

"C" should be selected as second best pioneer ALZ due to its satisfactory length (1,245ft), good drainage, and no approach/exit hindrances. Its 7-8% slope, which crosses the strip laterally (NE to SW), was a major disadvantage, although it is below the 10% maximum slope allowed. Its size would not permit easy expansion to meet the length requirement (1,500ft) of a hasty ALZ. "B" should be rejected. It has less than 1% slope and good drainage; however, it is unsuitable because of its short length.

Although the ground distance of the strip itself is 1,345ft, the hill mass approximately 175m to the NW, with an interpolated height of 20m above the NW end of the strip would be a terrain obstacle in the approach/exit direction. Using the 10 to 1 clearance ratio, the NW end of the strip would have to be shortened 25m (82ft), if landing or take off was required over this end of the strip. The usable length of the strip would only be 1,147ft, which is too short to meet the 1,200ft length required of a pioneer strip.

"D" should be rejected. It has good drainage and a 6-7% slope aligned generally with the length dimension of the strip (NE to SW). It is unsuitable because of its location. The measured ground distance length of the strip is 1,345ft. The stream bed in the area will be a hazard. In addition, the terrain obstructions (MONTE PIRATA and CERRO EL BUEY hill masses) at opposite ends of

the strip preclude aircraft from landing in Area D when the 10 to 1 clearance ratio is applied.

46

IT0637

LESSON 4 BEACH/AMPHIBIOUS LANDING AREA SELECTION MOS Manual Tasks: 301-338-2803 301-338-3701 OVERVIEW TASK DESCRIPTION: In this lesson you will learn to describe the general criteria, compute area size, percent of slope, and offshore gradient; analyze hazardous surface conditions and obstacles; consider accessibility and effects of weather; and prepare a checklist for a beach/amphibious landing area.

LEARNING OBJECTIVE: ACTIONS:

Describe the information and procedures required to select a beach/amphibious landing area.

CONDITIONS:

You will be given access to extracts from FM 20-12, FM 30-10, FM 3111, FM 31-12, and STP 34-96D24-SM-TG.

STANDARDS:

Beach/amphibious landing areas selection will be in accordance with FM 20-12, FM 30-10, FM 31-11, FM 31-12, and STP 34-96D24-SM-TG.

REFERENCES:

The material contained in this lesson was derived from the following publications: FM 20-12.

FM 30-10.

FM 31-11.

FM 31-12.

STP 34-96D24-SM-TG. INTRODUCTION

IAs at the CM&D section will identify beach/amphibious landing areas, especially when assigned to a joint task force (JTF) or in support of it.

PART A: BEACH/AMPHIBIOUS LANDING AREA FACTORS 1. A beach amphibious landing area is a continuous segment of coastline over which troops, equipment, and supplies can be landed by surface means.

47

IT0637

2. Primary and alternate amphibious operation landing areas are selected and prioritized after considering the size of the area required, terrain features, weather factors, enemy disposition, supporting fire, and proximity of the objectives. Amphibious operations require a detailed study of hydrography, weather, climate, and terrain, which is accomplished in a joint Army, Air Force, Navy, and Marine effort. The terrain portion is primarily the responsibility of Army and Marine specialists; terrain studies are prepared by terrain intelligence engineers, intelligence analysts, and lAs in a joint effort.

3. The landing force commander selects specific landing beaches from available beach/amphibious landing areas. When the amphibious task force is composed of two or more attack groups with related landing groups, a landing area may be selected for each attack group.

In this case, each landing group commander selects the landing beaches from within the assigned area. The principal factors in the selection of landing beaches are: a. Suitability for beaching landing ships, landing craft, and amphibious vehicles. b. Beach trafficability. c. Suitability of offshore approaches. d. Number, location, and suitability of beach support areas and beach exits. e. Location, type and density of beach obstacles, including underwater obstacles. f. Nature of the terrain immediately inland from the beaches. g. Suitability of LOCs, including roads, railroads, and waterways. h. Suitability of the beach from the standpoint of expected weather and tidal conditions. i. Known hostile force dispositions, strengths, and capabilities.

4.

Beaches are categorized by their shape (Figure 4-1). a. Concave (Point A to Point B). b. Convex (Point B to Point C). c. Straight (Point C to Point D). d. Irregular (Point A to Point D).

IT0637

48

Figure 4-1. Beach Categories.

5.

Beach types include the following beaches: * Coastal plain. * Coastal ridge. * Cliff/terrace. * Coral reef. * Glacial. * River mouth. * Pocket.

a. Coastal plain beaches. A landing on a wide coastal plain beach provides unrestricted maneuver room, and a subsequent advance from the beach can be made in any direction.

Boundaries and objectives are hard to locate on this type of terrain, and there are few prominent registration points for artillery, naval gun fire, and aerial bombardment. Usually there is no natural defensive terrain on the flanks of the beach head, so more troops are required to protect the flanks. Some coastal plain beaches are near marshy and swampy terrain which may hinder movement from the beach. b. A coastal ridge beach has terrain that rises evenly to a considerable distance back from the beach which gives the defender excellent observation and fields of fire. More commonly, the coastal area remains flat for some distance and then rises in a steep gradient to a coastal ridge.

49

IT0637

c. A cliff/terrace beach is usually quite narrow. The delineation of a cliff beach from a terrace beach is basically established by the height of the landmass immediately behind the beach. Cliff beaches may have rocks and debris which accumulates by erosion of the adjoining severe terrain. The surface is made up of the same type of material as the major adjacent landform. If wave action is strong on a cliff beach, any fine material is washed away resulting in a beach covered with boulders or barren rock. Cliff beaches isolated from strong wave action are usually composed of sand and similar to coastal plain beaches as far as surface materials are concerned. A terrace beach may be composed of loose sand or rocks; it may be barren rock; or it may be strewn with boulders. d. A coral reef beach is located in the coral region (normally between 30 degrees north latitude and 30 degrees south latitude) protected by a barrier reef with fringing reef along the shoreline, or it is located on an atoll. Any beach protected by a barrier reef is composed primarily of fine coral sand (coral skeletal remains, broken shells and hardened algae) and usually firm and narrow. When the beach or fringing reef is exposed to wave action, the foreshore is eroded. The coral reefs themselves normally present significant obstacles with abrupt seaward slope and the exposed offshore edge of the reef is steep. The upper surface of the reef may be extremely rough with jagged coral formations rising above the surface and deep pits indenting the surface of the reef. An atoll is a ring-shaped coral island or group of coral islands enclosing a lagoon or another island. It has the same basic characteristics as the coral barrier reef. e. Glacial beaches are usually found in the higher latitudes, normally above 60 degrees north and south latitude. These beaches were eroded by glacial action and have round and irregular shorelines with numerous inlets, some of which may be quite deep, long and narrow, with almost perpendicular, smooth mountain walls rising to great heights. This type of coast is very dangerous to navigation because of the islands and rocks off entrances to the inlets. The beach itself may be composed of material which has no geologic relationship to the coastline with depositions of material carried from the hinterland by the glaciers. This is often a mixture of silt, sand, gravel, and rocks. f. A river mouth or delta beach is easy to identify due to its proximity to the mouth of a major stream or river. This type of beach undergoes a greater physical change than the other beach types, and the foreshore is composed primarily of the type of sediment carried by the stream or river. g. A pocket beach is found on many of the coasts throughout the world and has a wide range of composition and topography. The irregular coastlines, where pocket beaches are quite common, are made up of headlands and indentations with the pocket beaches found in the indentations. This type of beach is divided into two general areas: the

IT0637

50

end zones and central zone. The end zones are those areas on the flanks inside the beach termination points. They are protected from direct wave action by the headlands and subsequently the beach soil is usually fine sand. The central zone is that portion of the entire beach between the end zones and exhibits the same characteristics and soil conditions of any beach exposed to wave action. Any highlands behind the beach may provide the source material which is continually washed down and deposited on the beach. Lowlands behind the beach, however, will have little effect on its character. A common problem affecting some pocket beaches is that many of the bays or other indentations fronting the beach may become blocked by sandbars which are built up by sand drifting along the coast in longshore currents. These sandbars may become attached to the mainland at the upstream end and any open channel which might exist will occur at the downstream end. Sometimes these sandbars connect offshore islands to the mainland. Pocket beaches are usually concave shaped.

PART B: BEACH/AMPHIBIOUS LANDING AREA CRITERIA 1. The required beach area for amphibious operations is calculated based on original requester's guidance and local SOP. The following unit beach landing should be used (Table 4-1 and Figure 4-2): Table 4-1. Unit Beach Landing Length.

51

IT0637

Figure 4-2. Typical Beachheads and Landing Areas.

2. In order to identify whether an area is suitable for beach/amphibious landings you must be given the following information: a. Minimum length of beach front necessary. b. Types of equipment being landed. c. Types of transports to be used, to include length and width of each transport type. d. Transport capability (i.e., can it land on beach? What minimum depth (draft) is required? etc.).

PART C: BEACH/AMPHIBIOUS LANDING AREA COMPUTATIONS Beach landing length is computed using the formula GD = PD x DPRF (or MD x DMRF) similarly as for DZs, HLZs and ALZs. Measurements are taken from one termination point to another (Figure 4-3) and rounded down to the nearest meter.

IT0637

52

a. The beach termination points are the extreme ends of the beach selected. The total length of the beach is measured between these points following the natural coastline. b. The beach width usually will not be uniform and, therefore, is determined at various points along the beach. c. The beachhead line, which is roughly semicircular, encompasses that area near the coast which is large enough for the deployment of the assault force and its supplies and equipment, and usually includes terrain features which are the initial objectives of the assault force. The beachhead line, once established, must be held so the subsequent landing forces can land and deploy in proper battle order. Loss of, or major enemy force penetration into, the beachhead line places the entire amphibious operation in jeopardy. d. The beach front extends from low tide limit to the high tide limit and usually coincides with the foreshore (Figure 4-4).

Figure 4-3. Beach Landing Length.

53

IT0637

PART D: PERCENT OF SLOPE AND GRADIENT COMPUTATIONS 1. Again, we use the same formula as for determining percent of slope of a DZ, HLZ, or ALZ with different specifications. Measurements are made of the width of the beach front.

SL = VD x 100 HD SL - Percent of slope.

VD - The height difference of the beach front, which is from the edge of the beach front (low tide limit) to the high tide limit (Figure 4-4).

HD - The horizontal (ground) distance of the beach front.

REMEMBER: Always round UP percent of slope to the nearest percent.

Figure 4-4. Shores.

2. Combined offshore or foreshore-back shore beach gradient is expressed as a ratio of the rise in elevation of one unit of measure to the horizontal (ground) distance in a number of the same unit of measure; for example, 1:15. Use the following formula: Gradient = Vertical distance (VD) Horizontal distance (HD) a. A quick way to obtain the gradient (1: ) is to invert the fraction and divide the denominator by the numerator, for example, if VD = 150m and HD = 3,000m, Gradient = 1: 3,000 = 1 : 20 150

IT0637

54

NOTE: Round UP any fractions to the next whole number, i.e., 1:50.52 = 1:51.

REMEMBER: To convert feet to meters, multiply feet x .3048 when converting meters to feet, multiply meters x 3.281. All measurements must be in the same unit. b. In computing the combined foreshore-back shore gradient, measure from the shoreline to the nearest 20m contour line which can be used for the start of the hinterland. You should transfer the 20m contour line from the map to the photo by interpolation prior to making your measurement.

3.

The gradient is then further expressed as shown in Table 4-2.

Table 4-2. Beach Gradients.

4. The depth lines or curves illustrated at 1, 2, and 3 fathoms (1 fathom = 6ft) (Figure 4-5) are established in order to determine the offshore gradient and assist in the safe approach of the landing craft. However, the ISLA DE VIEQUES map sheet shows the depth lines in feet. The depth curves may be a series of dots (as shown) or solid lines. Although Army responsibilities do not normally involve such hydrographic endeavors, in a joint operation you may be called upon to assist in developing these underwater "contour lines."

PART E: SURFACE AND OBSTACLE CONSIDERATIONS 1. Normally, the surface condition of the combined foreshore/back shore area is considered critical upon landing. The foreshore is generally white colored; the back shore begins where the beach discoloration changes from white to brownish-gray and ends at the beginning of the hinterland by revealing a darker tone and taller vegetation on aerial photography.

2.

Unfavorable or hazardous surface conditions include: a. Large rocks or reefs. b. Drop-offs (cliffs). c. Dense trees. d. Dense vegetation.

55

IT0637

Figure 4-5. Typical Beach/Amphibious Landing Area.

3.

Obstacles include: a. Buildings. b. Military impediments (i.e., landing craft barriers, barbed wire, etc.).

PART F: BEACH/AMPHIBIOUS LANDING AREA ACCESSIBILITY

1. Because of the configuration of shorelines, usually the area most suitable for the execution of a landing operation is also the most easily organized for defense.

2.

The ideal beach for amphibious landing is one with-a. No obstructions in the sea approaches. b. Deep water close inshore (Figure 4-4).

IT0637

56

c. Near shore gradients sufficiently deep for dry-ramp beaching of landing craft and ships (Figure 4-4). d. Soil composed of firm sand with gentle gradients/slopes. e. Small tides. f. No currents. g. No surfs.

3.

The beach terrain should be-a. Gently rising, relatively clear, and with firm surface that has adequate drainage. b. Flat or gently rising terrain, backed by a coastal range high enough to mask the landing

area.

NOTE: Ideal conditions are rarely found, so suitable areas must be evaluated to determine those that come nearest to optimum requirements.

4.

Other terrain considerations include:

a. Dunes. Ground that is sharply broken by extensive dunes or a low coastal plateau provides the attacker with concealment from the defender's observation. The small compartments and corridors limit the range of defensive fire.

(1) Transverse dunes are mounds of sand with their longest dimensions oriented at right angles to the prevailing wind. They almost always have a steeper leeward slope than they have on the windward side.

(2) Longitudinal dunes are sand formations whose longest dimensions are oriented in the same direction as the prevailing wind.

They may have a symmetrical shape or may be without any particular shape at all.

Longitudinal dunes may be over 100 miles in length. They are usually not backed by areas of standing water, such as swamps or marshes.

(3) Because they are formed by windblown sand coastal dunes, they are quite unstable landforms, appearing in one location as a transverse dune, only to disappear and reform as a longitudinal dune elsewhere. The winds responsible for their formation may also be the means for their destruction. b. Mountains located directly on the sea usually limit the number of beaches large enough to accommodate a landing force of effective size. Where steep ground is lightly defended or neglected by the defender, a small force may seize it and gain surprise. Airborne or airmobile troops may be used to block the movement of defensive reserves to the landing

57

IT0637

area, or to secure passes through the mountains and thus prevent the defender from interfering with the amphibious landing. c. Sandbars. These offshore sand formations are usually found near coastlines with a gentle beach gradient. During stormy weather the sandbars will be found further offshore than during calmer weather conditions. Sandbars paralleling the coast may cause a lagoon to form between themselves and the coastline; direct access to the shore is dependent on openings (channels) through the sandbar areas. The location of these channels are highly variable, and current photography is required before the actual landing takes place.

NOTE: Soil analysis, beach materials, and other trafficability aspects are normally reported by terrain and soil analysts. However, lAs will determine beach exits (roads, airstrips, and so on).

PART G: EFFECTS OF WEATHER ON BEACH/AMPHIBIOUS LANDING OPERATIONS All phases of an amphibious operation are directly influenced by weather conditions and climate.

Weather affects the tides, beaching and unloading conditions, speed of vessels, air support, and visibility. Poor weather conditions may provide cover for the amphibious force, but favorable weather is essential for the actual landing and during the initial build-up that follows. Excessive sea jeopardizes the entire operation.

PART H: BEACH/AMPHIBIOUS LANDING OPERATIONS COLLECTION CHECKLIST PREPARATION 1. A collection checklist must be prepared for each potential amphibious operation landing area using the following items: a. Identification. Local name and military designation. b. Location.

(1) Map reference--include series and sheet number(s) of both tactical and air-ground series.

(2) Political unit, area, UTM coordinate and geographic coordinates of the termination points.

(3) Landmark reference--description and location of the landmark, and azimuth and distance from landmark to termination point (Figure 4-6). c. Related water body or watercourses. Cross-reference to appropriate collection file. d. Length between termination points. e. Seashore form. Concave, convex, straight, or irregular.

IT0637

58

f. Coastal terrain type. Emergent, submergent, compound, coral reef, delta, volcanic, fault, manmade, and so on. g. Alignment. High water shoreline and low water shoreline. h. Beach width at low water. i. Beach width at high water. j. Backshore.

(1) Slope.

(2) Material (composition, texture, and trafficability).

(3) Obstacles.

(4) Vegetation. k. Foreshore.

(1) Slope.

(2) Material (composition, texture, and trafficability).

(3) Obstacles.

(4) Vegetation.

I. Near shore. (Give alignment and distance from low water shoreline).

(1) 10m (5 fathoms) depth line at low water.

(2) 6m (3 fathoms) depth line at low water.

(3) 4m (2 fathoms) depth line at low water.

(4) 2m (1 fathoms) depth line at low water.

(5) Obstacles.

(6) Reefs (near shore). (a) Type and location. (b) Distance from low water shoreline. (c) Length and width.

(d) Slope (direction).

59

IT0637

(e) Depth to surface of reef at low tide. (f) Depth to surface of reef at high tide. (g) Height of surface above water at high and low tide. (h) Effects of surf. (i) Effects on tide. (j) Channel through reef (alignment, width, and depth at low water).

(7) Reefs (offshore). (a) Type and location. (b) Distance from low water shoreline. (c) Length and width. (d) Slope (direction). (e) Depth to surface of reef at low tide. (f) Depth to surface of reef at high tide. (g) Height of surface above water at high and low tide. (h) Effects of surf. (i) Effects on tide. (j) Channel through reef (alignment, width, and depth at low water). m. Offshore conditions.

(1) Water depth.

(2) Offshore islands (location and characteristics).

(3) Sandbars. (a) Location and distance from low water shoreline. (b) Length and width. (c) Consistency. (d) Slope (seaward and landward).

IT0637

60

(e) Passages (alignment, width, and depth). (f) Depth at high and low water.

(4) Obstacles (type, location, and characteristics). n. Beach features. Natural and manmade; cusps, runnels, stream mouths, groins, piers, outfall pipes, and so on.

(1) Type and location.

(2) Number and extent.

(3) Bypass possibilities.

(4) Influence on operations. o. Tide.

(1) Type (diurnal, semidiurnal, or mixed).

(2) Type range (spring, topic, and diurnal).

(3) Range.

(4) Meteorological effects. p. Surf.

(1) Breakers (type, average height, distance formed from shore, and number of lines).

(2) Period.

(3) Width of surf zone.

(4) Direction from which swells approach coast.

(5) Weather and seasonal effects. q. Currents. Location, direction, and velocity. r. Beach exits.

(1) Type and location.

(2) Number and condition. s. Coastal terrain. Cross reference to appropriate collection file.

(1) Critical terrain features (location, type, bypasses, and influence on operations).

61

IT0637

(2) Obstacles (location, type, extent, bypasses, and influence on operations).

(3) Cross-country movement (troops, wheeled vehicles, and tracked vehicles). t. Support area cover and concealment. u. Dispersal and storage area. Location and description. v. Availability of fresh water. Location and quantity. w. Defenses. Location and type.

2. Terrain overlays are normally prepared by the terrain analysis detachment and added to the checklist. Overlays include presentations depicting cross-country movement, vegetation, slope, soil drainage pattern, ridge lines, and so on.

3. Refer to Figure 4-6. Subparagraph 6(2) (landmark reference) of the collection checklist description and location, distance and azimuth from a landmark to termination points, should be completed as follows: a. "Beach is located approximately 1,000m from the church northeast of Esperanza to the western termination point on a magnetic (MAG) azimuth of 179 degrees. Furthermore, the beach is approximately 2,100m from the same church to the eastern termination point on a MAG azimuth of 148 degrees." b. MAG azimuths are determined by using your coordination scale and converting grid azimuth to MAG azimuth by adding or subtracting the grid-magnetic (G-M) angle as described in the legend of your map. For example, in Figure 4-6, the concave-shaped pocket beach western termination point (KR 387020) is 1,000m from the Esperanza church on a grid azimuth of 170 degrees which must be converted to MAG azimuth (170 plus 9 degrees shown in the declination diagram), resulting in a MAG azimuth of 179 degrees; and the eastern termination point (KR 3990015) is 2,100m from the Esperanza church on a grid azimuth of 139 degrees, which must be converted to MAG azimuth (139 plus 9) = 148 degrees MAG azimuth.

Remember to add the G-M angle after obtaining the grid azimuth.

PART I: BEACH/AMPHIBIOUS LANDING AREA OVERLAYS Upon request the IA will prepare an overlay of the proposed primary and alternate beach/amphibious landing area. Beach/amphibious landing areas are referred to by their nickname.

IT0637

62

Figure 4-6.

MAG Azimuth Reading

63

IT0637

LESSON 4 PRACTICE EXERCISE The following material will test your grasp of the material covered in this lesson. There is only one correct answer for each item. When you have completed the exercise, check your answers with the answer key that follows. If you answer any item incorrectly, study again that part of the lesson which contains the portion involved.

1.

Which beach shape is depicted from Point A to Point B, Figure 4-7?

A. Concave.

B. Convex.

C. Straight.

D. Irregular.

Figure 4-7.

2.

Which beach type can be found above 60 degrees latitude?

A. Glacial.

B. Coral reef.

C. Dunes.

D. River mouth.

IT0637

64

3.

What is the gradient of a foreshore with VD = 15m and HD = 45m?

A. 1:2.

B. 1:3.

C. 1:5.

D. 1:6.

Use your ISLA DE VIEQUES map sheet, stereopair 2 (in back of the subcourse booklet), and the map extract (Figure 4-8) for questions 4 and 5. Make your measurements on the stereopair (scale 1:25,500) 4.

What is the beach gradient of the combined foreshore-back shore at Punta Vaca (KR 318007) annotated A? A. 1:5.

B. 1:7.5.

C. 1:10.

D. 1:18.

5.

What is the offshore gradient west of Punta Vaca between the two arrows annotated B? A. Gentle.

B. Flat.

C. Mild.

D. Steep.

65

IT0637

Figure 4-8. ISLA DE VIEQUES Map Extract.

IT0637

66

LESSON 4 PRACTICE EXERCISE ANSWER KEY AND FEEDBACK Item

Correct Answer and Feedback

1.

A. This is a concave-shaped beach (pages 48/49, para 4a/ fig 4-1).

2.

A. A glacial beach can be found above 60 degrees latitude (page 50, para 5e).

3.

B. A foreshore with VD = 15m and HD = 45m has a gradient of 15 = 1:3 (page 54/55, para 2).

45

4.

D. The combined foreshore-back shore gradient is 1:18.

First you must transfer the points to be measured from the map to the photo, and you should obtain a measurement of 1.4 centimeters (cm) from the point of Punta Vaca to the approximate location of the 20m contour line. Using the formula: GD = PD x DPRF, multiply 1.4cm x 25,500 = 35,700cm. Next, use the formula Gradient = VD HD Divide 35,700cm by 2,000cm (converted 20m) and the result is 1:17.85; round up the next whole number 1:18 (pages 54/55, para 2).

5.

C. The offshore gradient west of Punta Vaca between arrows (Annotation B) on the map extract (Figure 4-9) is considered mild. You should get a measurement of .058ft between the two points. Using the formula: GD = PD x DPRF, multiply .058 x 25,500 = 1,479ft. Next, use the formula Gradient = VD; insert 18ft for the next HD depth line for VD and 1,479ft for HD; you should get a gradient of 1:83. Finally, look up the type gradient: mild (page 54/55, paras 2 and 3/Table 4-2).

IT0637

68