AC 43.13-1А Page 307 1972 Section 4. PITOT-STATIC SYSTEMS
907. SYSTEM COMPONENTS. Conventional design of the pitot-static system consists of pitotstatic tubes or pitot tubes with static pressure ports or vents and their related heaters, if any, and includes lines, tubing, water drains and traps, and selector valves. Pressure actuated indicators such as the altimeter, airspeed, and rate-of-climb indicators, and control units such as air data transducers, and automatic pilots may be connected to the sysing them near the instrument and blowing clean, dry air through them. No instruments should be connected to the system during this process.
911, HEATER ELEMENTS. Some pitot-static tubes have replaceable heater elements, while others do not have replaceable elements. Check replacement of the heater element or the entire tube for proper operation by noting either ammeter current or that the tube or port gets
908. PITOT-STATIC TUBES AND LINES. The pitot tube is installed with the axis parallel to the longitudinal axis of the aircraft unless otherwise specified by the manufacturer. When lines are attached or removed from a bulkhead feedthrough fitting or at a union, precautions must be taken to assure that the line attached to the opposite end is not loosened, twisted, or damaged by rotation of the fitting. Such fittings normally are provided with a hex flange for holding.
909. PRESSURE PORTS OR VENTS, Static pressure ports or vents should be mounted flush with the fuselage skin. Inspect for elevation or depression of the port or vent fitting. Such elevation or depression may cause airflow disturbances at high speeds and result in erroneous airspeed indications.
910. CLEANING OF SYSTEM. Inspect air passages in the systems for water, paint, dirt, or other foreign matter. Probe the drains in the pitot tube to remove dirt or other obstructions. Tubing diameter should be checked when a problem is experienced with drainage of the pitot-static system or freezing at altitude. If this diameter is less than 3/8 inch, it should be replaced with larger tubing. Water may not drain freely from smaller diameter lines. Water or obstructions may be removed from the lines by disconnect- Chap 16
912. SYSTEM LEAK TESTING. Pitot-static leak tests should be made with all instruments connected to assure that no leaks occur at instrument connections. Such tests should be made whenever a connection has been loosened or an instrument replaced.
913. STATIC SYSTEM TEST. Advisory Circular AC 48-208A describes an acceptable means of complying with static system tests required by FAR Part 91, section 91.170, for airplanes operated in controlled airspace under IFR. (This circular also provides information concerning the test equipment used, and precautions to be taken when performing such tests.) Aircraft not operated in controlled airspace under IFR should be tested in accordance with the aircraft manufacturer's instructions.
If the manufacturer has not issued instructions for testing static systems, the following may be used:
a. Connect the test equipment directly to the static ports, if practicable. Otherwise, connect to a static system drain or tee connection and seal off the static ports. If the test equipment is connected to the static system at any point other than the static port, it should be made at a point where the connection may be readily inspected for system integrity. Observe testing precautions given in paragraph 915.
Par 907
b. Apply a vacuum equivalent to 1,000 feet altitude, (differential pressure of approximately
1.07 inches of mercury or 14.5 inches of water) and hold.
c. After one minute, check to see that the leakage has not exceeded the equivalent of 100 feet of altitude (decrease in differential pressure of approximately 0.105 inches of mercury or 1.48 inches of water).
914. PITOT SYSTEM TEST. Pitot systems should be tested in accordance with the aircraft manufacturer's instructions. If the manufacturer has not issued instructions for testing pitot systems, the following may be used:
a. Test the pifot system by sealing the drain holes and connecting the pitot pressure openings to a tee to which a source of pressure and a manometer or reliable airspeed indicator is connected.
b. Apply pressure to cause the airspeed indicator to indicate 150 knots (differential pressure 1.1 inches of mercury or 14.9 inches of water), hold at this point and clamp off source of pressure. After 1 minute, the leakage should not exceed 10 knots (decrease in differential pressure of approximately 0.15 inches of mercury or 2.04 inches of water). Warning: Do not apply suction to pitot lines.
Par 913 AC 43.13-11 197
915. PRECAUTIONS IN TESTING. Observe the fol lowing precautions in all pitot-static systen leak testing:
a. Perform all other work and inspections be fore leak testing.
b. Use a system diagram. It will prevent ap plying reverse pressure to any instrument, an help determine the location of a leak whil observing instrument indications.
c. Be certain that no leaks exist in the test equip.
ment.
d. Run full range tests only if you are thor.
oughly famlliar with the aircraft instrument system and the test equipment.
e. Pressure in the pitot system must always be equal to or greater than that in the stati‹ system. A negative differential pressure across an airspeed indicator can damage it.
f. The rate of change or the pressure applied should not exceed the design limits of any pitot or static instruments connected to the systems.
g. After the conclusion of the leak test, be certain that the system is returned to its norma.
fiying configuration, such as removing tape from static ports and pitot tube drain holes and replacing the drain plugs, etc.
916.-926. RESERVED.
Chap 16
AC 43.13-1A Page 309 1972 Section 5. MECHANICAL ADJUSTMENT OF MAGNETIC DIRECTION INDICATORS
927. CORRECTION FOR ERRORS. When a magnetic direction indicator does not provide satisfactory directional indications, it can be adjusted by the "ground swinging" technique to compensate for errors.
928. GROUND SWINGING. The ground swinging technique is as follows:
a. Move aircraft to a location free from influence of steel structures, underground pipes and cables, reinforced concrete, or other aircraft.
b. Place the aircraft in level flying position.
c. Check indicator for fluid level and cleanliness. If fluid is required, the compass is defective.
d. Remove compensating magnets from chambers or reset the fixed compensating magnets to neutral positions, whichever is applicable, before swinging.
•. Check the pivot friction of the indicator by deflecting the card with a small magnet. The card should rotate freely in a horizontal plane.
f. Align the aircraft with the North magnetic heading and compensate with compensating magnets. Repeat for the East magnetic heading.
Then place on South and West magnetic headings and remove half of the indicated error by adjusting the compensators. Engine(s) should be running.
g. Turn the aircraft on successive 80° headings through 860°. Prepare a placard to show the correction to be applied at each of these headings. When significant errors are intro-' duced by operation of electrical/electronic equipment or systems, the placard should also be marked at each 80° heading showing the correction to be applied when such equipment or systems are turned on or energized.
929. REMOTE GYRO COMPASS SYSTEMS, Adjustment and compensation of remote indicating gyro compasses, polar path compasses, and other systems of this type may also be accomplished using the "ground swinging" technique. Reference should be made to the manufacturer's manual for special tools, instructions, and procedures.
930.-940. RESERVED.
Chap 16 Par 927
Page 310 AC 43.13-1A 1972 Section 6. PRESERVATION AND PACKAGING
941. PRESERVATION. Preserve all instruments, serviceable or unserviceable, in accordance with the manufacturer's recommendations or other acceptable standards. Protect the unit against humidity, extreme temperatures, dust, rough handling or other damage until it is repaired or installed in an aircraft. The method used should be pickling, wrapping, sealing in plastic covering, rigid boxes with plastic or foam padding, or other methods appropriate to the instrument or subassembly.
942. STORAGE, Instruments should be stored in a location and a manner which provides maximum protection from physical damage. Serviceable instruments should remain packaged until installed in an aircraft. If a drying agent is used, the package should be dated so that the drying agent may be inspected for condition. Inspect units that remain in storage for extended periods of time for general condition and integrity of packaging and preserving materials.
943. SHIPPING. Protect the instrument from damage during shipment by sealing it in a moisture proof covering and protecting it with a drying agent. Use plastic foam, rubberized hair, or foam rubber molded to the configuration of the instrument case to support it inside a rigid shipping container. Large units may be shock-mounted on fitted pallets or racks and protected with covers.
944.-954. RESERVED.
Par 941 Chap 16
AC 43.13-1A Page 311 1972 Appendix 1 CROSS REFERENCE TABLE OF PARAGRAPH NUMBER CHANGES FROM AC 43.13-1 Former Paragraph Revised Paragraph Former Paragraph Revised Paragraph 61 96 62 97 68 98 64 99 65 100 66 101 67 102 68 108 Reserved 104-114 69 115 70 Reserved 116-126 71 127 72 128 78 129 74 180 75 181 76 182 188 78 184 79 185 186 Reserved 187-147 148 149 150 Reserved 26-86 151 152 86 158 Reserved 154-164 87 165 166 42 187 Reserved 48-58 168 91 169 Reserved 170-180 92 181 Reserved 57-67 98-99 Reserved 182-192 100 188 101 194 102 186 108 196 104 197 105 188 106 199 107 200 Reserved 201-211 108 212 109 218 79 110 214 111 215 112-118 Reserved 216-226 120 227 88 121 228 Reserved 84-94 122 229 60 95 128 230
Page 312 AC 43.13-1A 1972 paragrapk aragraph 281 879 282 215 880 288 284 892 285 898 894 247 248 406 249 407 250 408 251 409 252 410 258 411 ₫12 265 266 424 267 425 426 279 427 280 428 281 429 282 480 288 442 295 448 296 444 297 445 298 446 298 447 800 448 801 449 450 818 451 814 452 826 464 827 466 828 466 829 880 478 881 478 882 480 481 844 482 845 488 846 484 347 485 848 497 860 498 861 499 862 500 863 501 502 875 376 514 877 515 878 616
AC 43.13-1A Page 313 1972 Former Parapraph Former Paragraph 275 517 849 665 276 518 850-859 277 519 860 677 881 678 278 581 861A 679 279 862 680 280 868 681 281 582 864 682 282 588 865 688 288 584 866 684 284 585 867 685 285 586 868 686 286 687 869 687 287 588 870 688 288 589 871 689 289-299 872 690 800 558 878 691 801 554 378A 692 802 555 878B 898 878C 694 808 567 878D 695 804 568 8781 696 805 569 806 570 874 708 807 571 875 709 876 808 588 877 809 584 878 810 585 879 811 586 880 812 587 881 715 818 588 882 716 814 589 815 590 888 728 816 591 884 729 885 780 817 608 886 818 604 887 819 605 888 820 606 389 889 A 785 821 618 890 747 822 680 891 828 681 892 748 824 682 898 749 894 750 825 624 886 751 826-889 896 752 840 656 897 758 841 657 898-405 842 658 406 766 848 659 407 767 844 660 408 768 845 661 409 769 346 662 410 770 847 663 411 771 348 664 412-414
Page 314 AC 43.13-1A 1972 Former Paragraph Revised Paragraph Former Paragraph Resieed Paragraph 415 788 458 850 416 784 459 851 417 785 460 862 418 786 461 858 418-421 Reserved 787-797 462-472 Reserved 854-868 422 798 478 864 428 799 474 865 424 800 475 866 425 801 476 867 426 802 477 868 427 808 478 Reserved 869-879 428 804 479 880 429 805 480 881 480 806 481 882 481 807 482-484 Reserved 888-898 482 808 485 894 488-486 Reserved 809-819 486 895 487 820 487-491 Reserved 896-906 488 821 482 907 489 822 498 908 440 828 494 909 441 824 495 910 442 825 496 911 448 826 497 912 444 827 498 918 440-447 Reserved 828-888 499 914 448 839 500 915 449 840 501-511 Reserved 916-926 450 841 512 927 451 842 618 928 402 848 514 929 458 844 515-516 Reserved 930-940 New 845 617 941 454 846 518 842 455 847 619 948 456 848 520-550 Reserved 944-954 457 849
AC 43.13-1A Page 315 1972 Appendix 2
CROSS REFERENCE TABLE OF ILLUSTRATION NUMBER CHANGES Former Number Kovised Number Former Number Revined Number 2,1 (New figure) 2.25 2.27
2.2 (New figure) 2.26 2.28
4.24 (New figure)
2.28 2.25 No other illustration numbers were changed.
2.24 2,26 * U.S. GOVERNMENT PRINTING OFFICE: 1973 0-472-339