Rev. 1977 1025 STEEL FITTING SPRING
FABRIC WING
• STEEL ROD WASHER NUT
METAL WING 2017 FIGURE 3.17.-Typical wing tip installations.
vice, in addition to impedance matching, also provides isolation between VOR navigation receivers while keeping line insertion losses at a minimum.
40. RANGE RECEIVING ANTENNAS. Mount T", "L", or "V" antennas on top or bottom of the aircraft with approximately 1-foot clearance from the fuselage and wings. Typical wire antenna installations are shown in figures 3.15 through 3.19.
41. MARKER RECEIVING ANTENNA. The marker receiver operates at a frequency of 75 MHz. In order to keep to a minimum the number of antennas on the aircraft, the marker receiver may utilize the same antenna as the range receiver if that antenna is mounted on the underside of the aircraft. However, both receivers should include provisions to permit simultaneous opera- Chap 3 AC 43.13-2A tion without interference. A whip or other vertical type of antenna should not be used for marker reception since the ground facility transmits from a horizontally polarized antenna.
4130
OR AN BOLT AND NUT 1025 STEEL
THIMBLE SPRING
FIN TAIL POST RUDDER:
1025 OR 4130 TUBE
RUBBER TENSION UNIT FIGURe 3.18.-Typical in tip installations.
42. ATC RADAR BEACON (TRANSPONDER) AND
DISTANCE MEASURING EQUIPMENT (DME) AN- TENNAS. Locate these antennas at an unobstructed location on the underside of the fuselage.
preferably at the lowest point of the aircraft when in level flight. To the extent practicable, mount the antenna so that the base is horizontal when the aircraft is in cruise attitude.
a. Installation. Mount the antennas at least 36 inches away from obstructions and as far as possible from other antennas. Tests have shown that the location of the antenna with respect to obstructions is of greater importance than having the antenna installed in a vertical position.
However, signal strength and pattern become noticeably affected as the angle of the antenna approaches 45° from the desired vertical position.
On fabric-covered aircraft or aircraft with other types of nonmetallic skin, it will be necessary to provide a flat metallic surface or ground plane" extending at least 12 inches in all direc- 19
AC 43.13-2A Rev. 1977
ANCHOR CABLE COIL SPRING
INSULATORS
DOUBLER FIGURE 3.19.- Typical wire antenna installations.
FIGURE 3.20.--Preferred position for distance measuring and/or ATO radar beacon antennas.
tions from the center of the antenna. Be sure the antenna makes a good, direct electrical connection with the ground plane. Install gaskets, pressurization seals, and/or sealant as required.
b. Dual System Installations. When dual ATC radar systems, dual DME systems, or combinations of these systems are installed, determine that the separation between their respective antennas is within the manufacturer's prescribed limits. (See paragraph 27i for mutual interference in DME and ATC radar beacon systems.)
c. Antenna Cable. Route the antenna cable in the most direct path practicable. Since losses can be relatively high at these frequencies, follow the equipment manufacturer's recommendations regarding transmission lines and lengths.
43. DIRECTION FINDING ANTENNAS (100 to 1750 KHz). Manual or automatic loop-type antennas are used with direction-finding receivers. The loops are designed for use with a particular receiver. Connecting wires between the loops and receivers are also designed for the specific equipment. Accordingly, only components meeting the specification characteristics of the receiver manufacturer should be used.
Chap 3
Rev. 1977 AC 43.13-2А
a. Loops enclosed in streamlined housings or exposed loops are satisfactory for external mounting on an aircraft. Loops may also be flush mounted on the aircraft when proper attention is given to avoid interference from metallic structure and skin of the aircraft.
c. Installation kits are designed for either top or bottom fuselage mounting of loop and sense antennas, or a combination of these two locations.
Particular attention should be paid to the manufacturer's installation instructions for antenna location (top or bottom) and loop output connections, in order to prevent 180° errors in bearing indications.
< >
INTERNAL LOOP
ENCLOSED LOOP FIGURE 3.21.-Typical ADF antenna installations.
b. Sense antennas are used to resolve radio bearing ambiguity in direction finding systems.
The sense and its lead-in must be matched to the input capacitance of the ADF receiver. The sense antenna capacitance is a function of length, spacing between antenna and fuselage, and leadin capacitance. To achieve this antenna/receiver capacitance match, it is important that the sense antenna be installed in accordance with the ADF manufacturer's recommendations for the particular make and model of aircraft.
d. Optimum ADF performance is achieved when the "T", rather than the "L", type of sense antenna is used, (see fig. 3.15). The "p" type has a noise cancelling effect due to the antenna cable being connected in the center of the antenna. The "L" type antenna has directional characteristics and may not produce a definite station passage indication as the "T" type does.
A whip antenna of a type and dimension recommended by the equipment manufacturer may be used in place of the "T" or "L' types. Methods of installing a whip antenna are shown in figures
3.1, 3.2, and 3.3.
e. Because the ADF receiver is susceptible to aircraft radiated noise, antenna lead-ins should be routed so that they are kept away from electric power cables, alternators, solid state power supplies, anti-collision lights, pulse transmitting equipment, etc. They may be rounted against airframe members for extra shielding.
f. Loop-ins should be of the recommended type and length. The length of lead-in specified by the manufacturer for a particular installation may be excessive for the physical dimensions between the antenna and receiver. Excessive leadin should not be trimmed, but should be coiled to take up the extra length. Do not coil excess cable in any area subject to electrical noise.
g. After completing the installation, it is essential that the loop be calibrated. One acceptable means of compliance is contained in AC 43.13-1A, chapter 15, section 6, paragraphs 848 through 853.
44. ANTENNA INSTALLATION ON PRESSURIZED AIRCRAFT. The use of doublers, to reinforce the aircraft skin to support antennas, is previously described in this chapter. The material contained in this paragraph concerns the methods of apply- Chap 3 21
AC 43.13-2A ing sealant to guard against the passage of air, liquids, and vapors from pressurized structures.
a. Typical Antenna Installation Procedure. When the attaching parts and the antenna are ready for installation, clean all faying surfaces with a cleaning solvent. Clean a larger area than that to which sealant is to be applied. Remove the solvent from the faying surfaces by blasting with dry air and wiping with a clean soft cloth.
(1) Coat the affected area with the primer specified by the sealant manufacturer.
(2) Apply the sealant to one surface, using a spatula or brush, and spread it over the entire faying surface until a uniform thickness of approximately ⅓2-inch is obtained. (See fig. 3.22 and 3.23.)
ANTENNA.
GASKET
SEALANT
AIRCRAFT SKIN - DOUBLER FIGURE 3.22. Typical antenna installation.
(3) Place the component parts together and install the required fasteners. If permanent fasteners cannot be installed, use temporary fasteners to hold the component parts together until the sealant has cured. Install permanent fasteners with fresh sealant by dipping the fastener in sealant or by filling the fastener hole with sealant. (See fig. 3.24.)
(4) Fill holes and joggles by injecting the sealant into the voids and/or cavities. This method is used where the sealant cannot be applied with a spatula or brush. Figure 3.25.
(5) Allow the sealant to cure, then remove excess sealant from the periphery of the antenna using a nonmetallic scraper.
22 Rev. 1977
•SEALANT APPROX.
1/32" THICK FIGURE 3.23.-Faying surface sealing.
Warning Sealants may contain toxic and/or flammable components. Avoid inhalation of vapors. Supply adequate ventilation and provide a suitable exhaust system. Wear approved respiratory protection while using these materials in confined areas. Do not allow the sealant to come in contact with the skin or eyes. Insure that no source of ignition is present in the working area.
b. High Speed Aircraft. The sealant methods described should be used to prevent moisture or water from entering the aircraft and the expulsion of air and vapors when the aircraft structure is pressurized.
SEALANT MAYBE
APPLIED EITHER TO
HOLE OR FASTENER
- SEALANT
- SEALANT FIGURE 3.24.-Fastener sealing.
Chap 3
Rev. 1977 AC 43.13-2A
(1) Figure 3.26 displays a blade type antenna mounted on a flat surface using a sealing gasket.
This type of installation does not require the application of a sealant.
(2) Figures 3.27 and 3.28 display two types of flush mounted antennas. The antenna unit and fiberglass cover are manufactured as one integral assembly.
(3) Flush mounted antennas installed on a vertical fin are normally part of the primary structure. The radiating elements of the antenna and the fiberglass cover are individual units.
GUN NOZZLE (a) Clean all metal surfaces necessary to insure good electrical bonding contact between the antenna mounting surface and the aircraft
(b) After the fiberglass cover is installed, FIGURE 3.25.-Injection sealing. sealer may be applied to fill the space between the fiberglass cover and skin of the vertical fin.
Figure 3.29 displays one-half of a vertical fin antenna installation. An identical installation is required on each side.
GASKET
ANTENNA FIOURE 3.27.-ATC flush mounted antenna.
FIGURE 3.26.- Blade antenna installation.
Chap 3 23
AC 43.13-2A Rev. 1977
• FIGURE 3.28.-Marker beacon flush mounted antenna.
FIGURE 3.29.-VOR flush mounted antenna.
45.-50. [RESERVED] 24 Chap 3 |
Rev. 1977 AC 43.13-2A Chapter 4. ANTICOLLISION AND SUPPLEMENTARY LIGHT INSTALLATIONS
51. ANTICOLLISION AND SUPPLEMENTARY LIGHT SYSTEMS.
a. Anticollision Lights. The requirements for anticollision lights are included in Federal Aviation Regulations, Parts 23, 25, 27, and 29. Aircraft for which an application for type certificate was made before April 1, 1957, may conform either to the above regulations or to the following
(1) Anticollision lights (when installed) should be installed on top of the fuselage or tail in such a location that the light will not be detrimental to the flight crew's vision and will not detract from the conspicuity of the position lights.
If there is no acceptable location on top of the fuselage or tail, a bottom fuselage installation may be used.
(2) The color of the anticollision light shall be aviation red or white in accordance with the specifications of FAR Part 23.
(3) The arrangement of the anticollision light
(i.e., number of light sources, beam width, speed of rotation, etc.) should be such as to give an effective flash frequency of not less than 40 and not more than 100 cycles per minute.
b. Supplementary lights may be installed in addition to position and anticollision lights required by applicable regulations, provided that the required position and anticollision lights are continuously visible and unmistakably recognizable and their conspicuity is not degraded by such supplementary lights.
52. INTERFERENCE.
a. Crew Vision. Partial masking of the light may be necessary to prevent direct or reflected light rays from any anticollision or supplementary light from interfering with crew vision.
Determine that the field of coverage requirements are met. An acceptable method of preventing light reflection from propeller disc, nacelle, or wing surface is an application of nonreflective paint on surfaces which present a reflection problem. Perform a night flight-check to assure that any objectionable light reflection has been eliminated. Enter a notation to that effect in the aircraft records.
b. Communication and Navigation. Assure that the installation and operation of any anticollision/supplementary light does not interfere with the performance of installed communication or navigation equipment. Capacitor discharge light (strobe) systems may generate radio frequency interference (RFI). This radiated interference can be induced into the audio circuits of communication or navigation systems and is noticeable by audible clicks in the speaker or headphones. The magnitude of the RFI disturbance does not usually disrupt the intelligence of audio reception.
c. Precautions. RFI can be reduced or eliminated by observing the following precautions during installation of capacitor discharge light systems :
(1) Locate the power supply at least three
(3) feet from any antenna, especially antennas for radio systems that operate in the lower frequency bands.
(2) Assure that the lamp unit (flash tube) wires are separated from other aircraft wiring placing particular emphasis on coaxial cables and radio equipment input power wires.
(3) Make sure that the power supply case is adequately bonded to the airframe.
(4) Ground the shield around the interconnecting wires between the lamp unit and power supply at the power supply end only.
53. MARKINGS AND PLACARDS. Identify each switch for an anticollision/supplementary light and indicate its operation. The aircraft should be flight tested under haze, overcast, and visible Chap 4 25
AC 43.13-2A moisture conditions to ascertain that no interference to pilot vision is produced by operation of these lights. If found unsatisfactory by test, or in the absence of such testing, a placard should be provided to the pilot stating that the appropriate lights be turned off while operating in these conditions.
54. ELECTRICAL INSTALLATION. Install an individual switch for the anticollision light or supplementary light system that is independent of the position light system switch. Data for the installation of wiring, protection device, and generator limitations is contained in chapter 11 of Advisory Circular 43.13-1A, "Acceptable Methods, Techniques, and Practices-Aircraft Inspection and Repair." Assure that the terminal voltage at each light is within the limits as prescribed by the manufacturer.
55. ALTERATION OF STRUCTURE.
a. The simplest light installation is to secure the light to a reinforced fuselage skin panel.
The reinforcement doubler shall be of equivalent thickness, material, and strength as the existing skin. (Install as shown in fig. 4.1.)
ANTICOLLISION LIGHT OR
SUPPLEMENTARY LIGHT
FUSELAGE SKIN
- EXISTING STRINGER
EXISTING STRINGER VIEW A-A
APPROXIMATELY ONE REINFORCING DOUBLER INCH SPACING OF ALCLAD 2024-73 1/8" MIN. DIA. RIVET 1 1/2" EDGE DISTANCE MIN.
FIGURE 4.1.- -Typical anticollision or supplementary light installation in a skin panel (unpressurized).
Rev. 1977
b. When a formed angle stringer is cut and partially removed, position the reinforcement doubler between the skin and the frame. Doubler to be equivalent to the stringer in thickness and extend lengthwise beyond the adjacent fuselage frames. The distance between the light and the edge of the doubler is twice the height of the doubler flange. (See fig. 4.2 for typical installation.)
CUT STRINGER EINFORCING DOULLE ANTICOLLISION LIGHT OR * ALCLAD T.
SUPPLEMENTARY LIGHT FRAME
STRINGER
DOUBLE FLANGES
AT LEAST THE HEIGHT STRINGER
OF CUT STRINGER STUNGER RIVETS ADDED
FLANGE AND DOULLER AS SHOWN ON
EXISTING RIVETS FRAMES FIGURE 4.2.-Typical anticollision or supplementary light installation involving a cut stringer (unpressurized).
c. Engineering evaluation is required for instal lations involving the cutting of complex formed or extruded stiffeners, fuselage frames, or pressurized skin of pressurized aircraft.
d. Vertical stabilizer installations may be made on aircraft if the stabilizer is large enough in cross section to accommodate the light installation, and aircraft flutter and vibration characteristics are not adversely affected. Locate such an installation near a spar, and add formers as required to stiffen the structure near the light.
(A typical installation is shown in fig. 4.3.)
e. Rudder installations are not recommended because of the possible structural difficulties.
However, if such installations are considered, make an engineering evaluation to determine whether the added mass of the light installation Chap 4
Rev. 1977
MOUNTING SCREW HOLES
FOR LIGHT TO FAIRING
ANTICOLUSION LIGHT O
SUPPLEMENTARY LIGH
VERTICAL
STABILIZER
APPROXIMATELY ONE
INCH SPACING OF 1/8" MIN. DIA. RIVET
LIGHT MOUNTING
FAIRING
• MOUNTING RING
VERTICAL
STABILIZER
VIEW A-A NOTE:
SKIN THICKNESS OF MOUNTING RING AND
FAIRING ARE AT LEAST EQUIVALENT FIGURE 4.3.-Typical anticollision or supplementary light installation in a fin tip.
will adversely affect the flutter and vibration characteristics of the tail surfaces.
f. Pressurized Aircraft Installation. Doubler installation to reinforce the aircraft skin previously described in this chapter is adaptable to pressurized structure with the application of sealant.
Sealant is used to prevent moisture or water from entering the aircraft and the expulsion of air when the aircraft structure is pressurized.
(1) Sealant procedures for aircraft skin reinforcing doubler and doubler fasteners are contained in paragraph 44, chapter 3 of this manual.
The aircraft manufacturer's data may recommend the specific sealant to be used and provide instructions for the application.
(2) Figures 4.4 and 4.5 illustrate two different designs of anticollision light assemblies.
The application of sealant is required when either type of light assemblies is installed.
procedures would be identical for installation of a capacitor discharge (strobe) light system.
Chap 4 AC 43.13-2A
AIRCRAFT SKIN
DOUBLER -
SEALANT FIGURE 4.4.-Typical rotating type anticollision light installation for pressurized aircraft.
Caution: Sealant and solvents may contain toxic and/or flammable components. Avoid inhalation of vapors and supply adequate ventilation. Wear appropriate respiratory protection while using these materials in confined areas. Avoid contact with the skin and eyes.
AIRCRAFT SKIN
DOUBLER
SEALANT
COAT SCREWS WITH SEALANT FIGURE 4.5.-Typical oscillating type anticollision light installation for pressurized aircraft.
56. GUIDELINES FOR INSTALLATIONS.
a. Prior Approval. Due to the complexity of measurements for intensity, field of coverage, and color, evidence of FAA approval should be obtained from the light manufacturer before installation.
b. System Performance.
(1) Field of Coverage. Evidence of FAA approval for "field of coverage" should be obtained from the light manufacturer before installation. To insure that the manufacturer's approved field of coverage is applicable to an installation, his mounting tolerance should not be exceeded.
Rev. 1977 AC 43.13-2A
(2) Obstructed Visibility. Measure all solid angles of obstruction within the required field of coverage. For multiple light installations, coverage between the mounting levels is not necessary. When a multiple light installation is being repeated in each independent measurement (overlap) should be counted. Methods for determining the amount of obstructed visibility are given below; howerer, other methods can give acceptable results.
(a) Wall Shadows. This procedure is applicable to installations where shadows from light obstructions appear on a vertical surface such as a hangar wall. Validity is based on two facts: (1) that a vertical surface can approximate a sphere surface if the distance from the light is considerable, and the shadow is reasonably small, and (2) that sphere surface area can be converted to steradians by dividing by the radius squared.
1 Position the aircraft in a darkened hangar so that longitudinal axis is perpendicular to a hangar wall. Level as for weight and bal- The distance extend in each direction within at least 30° above and 30° below the horizontal plane of the aircraft, except that there may be solid angles of obstructed visibility totalling not more than the requirements of paragraph .1401(b) of the applicable airworthiness regulations.
5 For installations where shadows are restricted to directly aft and centered about the longitudinal axis, the following procedures apply:
a Establish a point on the wall which corresponds to a line parallel to the longitudinal axis and through the light associated with the shadow.
& Measure the distance from the light to the point and determine the area representing
0.15 steradians (A=0.15d'). The distance (d) should be at least 20 feet.
c Draw a circle, with the established point as the center, having an area equal to that found in b above.
d If the shadow falls within this circle, its position is acceptable. For multiple light installations, consider only the shadow above light level.
e If the shadow is partially out of the circle, the shape of the 0.15 steradian area may be varied, but the established point should remain at the center of the area (centroid).
(b) Ramp Shadows. This procedure is applicable to shadows which appear on a horizontal plane such as a flat level ramp and will be associated with a top mounted light and a
0.5 steradian limit. Area measurements as described in the wall shadow method should not be used. Some error is inherent, because horizontal angles are measured on a plane displaced from the light source. To compensate for these measinstallations, only shadows above the level of the urement errors, a table (fig. 4.8) is furnished top light should be considered. to convert from measured solid angles to true 3 Compute the solid angle obstruction solid angles. A term "square degrees" is used in steradians, by dividing each shadow area by to aid in the discussions of solid angle measurethe square of the distance from the center of the ments.
area to the light. 1 If no masking is required, remove the 4 Evaluate the results to determine if do mine te red cover and attach its clamp ring to the light the system consists of enough lights to illuminate the physical configuration and flight character- the vital areas around the aircraft, considering istics of the aircraft. The field of coverage must base. If masking is used, obtain a clear cover and install it with a duplicate mask. available dark ramp. A minimum of 50 feet 2 Center the aircraft on the largest Chap 4 28
Rev. 1977 AC 43.13-2A radius of clear ramp space will usually be needed.
If the installation is symmetrical, clear ramp space will be needed on one side only. Level the aircraft as for weight and balance check. Trim the flaps, rudder, elevator and ailerons. With jacks in place, raise the gear if the measurement results would otherwise be affected.
4 At night, turn on the anticollision light and chalk all shadow patterns (except jack shadows) which appear outside the circle.
the light rotates so as to cause the shadows to oscillate, lay twine along the outermost edge of the shadow, and chalk along the line.
5 Move the aircraft to facilitate area 3 Chalk the following marks on the measurements. Measure, sketch, and chart the ramp: ramp marks and other information as shown in a A reference point directly below Figure 4.6. Measure enough points along the the light. shadow patterns to accurately describe them.
b A circle centered on this reference Make enough sketches to include all shadows.
point having a radius equal to 1.732 times the 6 Convert the above measurements to a height of the light above the point. (The circle graph showing vertical degrees vs. horizontal represents area beyond the minus 30° vertical degrees as shown in Figure 4.7 (first quadrant).
The second quadrant will have to be measured tudinal centerline which passes through the ref- erence point. « A line parallel to the aircraft longi- also to obtain the total shadow area for one side. If the shadow pattern is symmetrical, no other measurements will be necessary. Use 1 degree for each space on the graph paper and count the square degrees of shadow. A total of 1,642 or IST QUADRANT less is within limits. A total of 1,872 or more is out of limits, and if possible, should be reduced O EXAMPLE POINT mask. If the count is between 1,642 and 1,872, by adding or moving a light, or by trimming a proceed as follows: For each 1 degree segment of vertical (pitch), convert the counted square degrees to true square degrees by use of the table of Figure 4.8. If the sum of the true square degrees from all segments exceeds 1,642 (0.5
- SHADOW steradian), the installation is out of limits.
17.3 FT. (c) Scale Drawings. Accurate scale draw- 1OFT. BELOW LIGHT POINT ON RAMP ings can be used to measure solid angles of obstruction. Such drawings should have sufficient size and accuracy to give dependable results. In some cases, actual measurements can be combined POINT O with small drawings as shown in Figure 4.9. For
• 20 the 6 points established on the left wing, a string can be used to connect the light successively to EXAMPLE POINT O A = 20 FT. each. A protractor can then be used to measure 8 = 20 FT. the vertical angle from level. The horizontal H = 10 FT. DISTANCE TO POINT I = 28.2 FT. angle for each point can be measured on the top HORIZONTAL ANGLE = 45° view (center). When both horizontal and verti- VERTICAL ANGLE = 19.4° cal angles for each point have been determined, they can be plotted on a graph as shown in Fig- FIGURE 4.6.-Ramp shadow pattern. ure 4.10. If a symmetrical condition exists, only the first and second quadrants need be measured.
d A line perpendicular to the above The first quadrant contains approximately 450 line, which also passes through the reference square degrees of obstruction. The other wing point. quadrant will double this to 900 square degrees.
Chap 4 29
Rev. 1977 AC 43.13-2A
• - EXAMPLE O:
DEGREES BELOW LIGHT (PITCH) HORIZONTAL ANGLE = 45° PITCH ANGLE = 19.4° TAN PITCH ANGLE = 10/28.2 o 20 - FUSELAGE WING SHADOW 28.2 SHADOW
LIGHT BASE SHADOW 30 20 30 50 60 70 80 90
HORIZONTAL DEGREES FROM NOSE FIGURE 4.7.-Conversion to vertical vs. horizontal degrees.
A measurement of the fin and rudder shadows adds approximately 100 for a total of 1,000 square degrees. Since a maximum of 1,642 square degrees is allowed (0.5 steradians), this installation is well within limits. Due to limitations of the method, results within 10% (0.05 steradians) of the limit are questionable. Many times a mask is required to prevent reflections into the cockpit.
In the example of figures 4.9 and 4.10, the installed mask blocks the light for +10 horizontal degrees and from -10 to -30 vertical degrees.
These 400 square degrees were measured at the
• light.
When larger drawings are used and no actual aircraft measures are made, vertical angles should not be taken directly from the drawing, but should be computed as follows:
1 On the aircraft side view, measure the vertical distance from a point to the light level.
2 On the top view, measure the distance from the point to the light.
3 Compute:
vertical distance Tangent of vertical angle= horizontal distance Pitch Segment (Degrees) Messured Degrees Square Factor Correction Square True Degrees (Degrees) Segment Pitch Measurco Square Degrees Correction Factor True Degrees Square 24-23 22-21 30-29 29-28 28-27 27-26 26-25 25-24 23-22 21-20 20-19 19-18 18-17 17-16 16-15 90 4826 90 • 87036 • 88701 • 87882 • 89493 • 90259 • 90996 • 91706 • 93667 • 94264 • 96363 • 95372 • 92388 • 93042 • 95882 , 94832 78.33 39.03 79.09 12-11 15-14 14-13 13-12 11-10 10-9 7-6 9-8 8-7 3-2 2-1 1-0 6-5 5-4 4-3 • 96815 • 98629 • 98325 • 98902 • 97237 • 97630 • 97992 • 99996 • 99813 • 99905 . 99144 • 99540 • 99966 • 99692 • 99357 TOTAL FIGURE 4.8.-Conversion to true square degrees-1st quadrant.
Chap 4 30