CFR > Title 14 - Aeronautics and Space > CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION > SUBCHAPTER J—NAVIGATIONAL FACILITIES (parts 170 to 171) > PART 171—NON-FEDERAL NAVIGATION FACILITIES > SUBPART J—Microwave Landing System (MLS) (§171.301 to §171.327) > 171.311—Signal format requirements.

171.311—Signal format requirements.

The signals radiated by the MLS must conform to the signal format in which angle guidance functions and data functions are transmitted sequentially on the same C-band frequency. Each function is identified by a unique digital code which initializes the airborne receiver for proper processing. The signal format must meet the following minimum requirements:
(a) Frequency assignment. The ground components (except DME/Marker Beacon) must operate on a single frequency assignment or channel, using time division multiplexing. These components must be capable of operating on any one of the 200 channels spaced 300 KHz apart with center frequencies from 5031.0 MHz to 5090.7 MHz and with channel numbering as shown in Table 1a. The operating radio frequencies of all ground components must not vary by more than ±10 KHz from the assigned frequency. Any one transmitter frequency must not vary more than ±50 Hz in any one second period. The MLS angle/data and DME equipment must operate on one of the paired channels as shown in Table 1b.
Table 1a—Frequency Channel Plan
Channel No. Frequency (MHz)
500 5031.0
501 5031.3
502 5031.6
503 5031.9
504 5032.2
505 5032.5
506 5032.8
507 5033.1
508 5033.4
509 5033.7
510 5034.0
511 5034.3
*****
598 5060.4
599 5060.7
600 5061.0
601 5061.3
*****
698 5090.4
699 5090.7
Table 1b—Channels
Channel pairing DME No. VHF freq. MHz MLS angle freq. MHz MLS Ch. No. DME parameters Interrogation Freq. MHz Pulse codes DME/N µs DME/P Mode IA µs FA µs Reply Freq. MHz Pulse codes µs
* 1X 1025 12 962 12
** 1Y 1025 36 1088 30
* 2X 1026 12 963 12
** 2Y 1026 36 1089 30
* 3X 1027 12 964 12
** 3Y 1027 36 1090 30
* 4X 1028 12 965 12
** 4Y 1028 36 1091 30
* 5X 1029 12 966 12
** 5Y 1029 36 1092 30
* 6X 1030 12 967 12
** 6Y 1030 36 1093 30
* 7X 1031 12 968 12
** 7Y 1031 36 1094 30
* 8X 1032 12 969 12
** 8Y 1032 36 1095 30
* 9X 1033 12 970 12
** 9Y 1033 36 1096 30
* 10X 1034 12 971 12
** 10Y 1034 36 1097 30
* 11X 1035 12 972 12
** 11Y 1035 36 1098 30
* 12X 1036 12 973 12
** 12Y 1036 36 1099 30
* 13X 1037 12 974 12
** 13Y 1037 36 1100 30
* 14X 1038 12 975 12
Code of Federal Regulations 801
** 14Y 1038 36 1101 30
* 15X 1039 12 976 12
** 15Y 1039 36 1102 30
* 16X 1040 12 977 12
** 16Y 1040 36 1103 30
▽17X 108.00 1041 12 978 12
17Y 108.05 5043.0 540 1041 36 36 42 1104 30
17Z 5043.3 541 1041 21 27 1104 15
18X 108.10 5031.0 500 1042 12 12 18 979 12
18W 5031.3 501 1042 24 30 979 24
18Y 108.15 5043.6 542 1042 36 36 42 1105 30
18Z 5043.9 543 1042 21 27 1105 15
19X 108.20 1043 12 980 12
19Y 108.25 5044.2 544 1043 36 36 42 1106 30
19Z 5044.5 545 1043 21 27 1106 15
20X 108.30 5031.6 502 1044 12 12 18 981 12
20W 5031.9 503 1044 24 30 981 24
20Y 108.35 5044.8 546 1044 36 36 42 1107 30
20Z 5045.1 547 1044 21 27 1107 15
21X 108.40 1045 12 982 12
21Y 108.45 5045.4 548 1045 36 36 42 1108 30
21Z 5045.7 549 1045 21 27 1108 15
22X 108.50 5032.2 504 1046 12 12 18 983 12
22W 5032.5 505 1046 24 30 983 24
22Y 108.55 5046.0 550 1046 36 36 42 1109 30
22Z 5046.3 551 1046 21 27 1109 15
23X 108.60 1047 12 984 12
23Y 108.65 5046.6 552 1047 36 36 42 1110 30
23Z 5046.9 553 1047 21 27 1110 15
24X 108.70 5032.8 506 1048 12 12 18 985 12
24W 5033.1 507 1048 24 30 985 24
24Y 108.75 5047.2 554 1048 36 36 42 1111 30
24Z 5047.5 555 1048 21 27 1111 15
25X 108.80 1049 12 986 12
25Y 108.85 5047.8 556 1049 36 36 42 1112 30
25Z 5048.1 557 1049 21 27 1112 15
26X 108.90 5033.4 508 1050 12 12 18 987 12
26W 5033.7 509 1050 24 30 987 24
26Y 108.95 5048.4 558 1050 36 36 42 1113 30
26Z 5048.7 559 1050 21 27 1113 15
27X 109.00 1051 12 988 12
27Y 109.05 5049.0 560 1051 36 36 42 1114 30
27Z 5049.3 561 1051 21 27 1114 15
28X 109.10 5034.0 510 1052 12 12 18 989 12
28W 5034.3 511 1052 24 30 989 24
28Y 109.15 5049.6 562 1052 36 36 42 1115 30
28Z 5049.9 563 1052 21 27 1115 15
29X 109.20 1053 12 990 12
29Y 109.25 5050.2 564 1053 36 36 42 1116 30
29Z 5050.5 565 1043 21 27 1116 15
30X 109.30 5034.6 512 1054 12 12 18 991 12
30W 5034.9 513 1054 24 30 991 24
30Y 109.35 5050.8 566 1054 36 36 42 1117 30
30Z 5051.1 567 1054 21 27 1117 15
31X 109.40 1055 12 992 12
31Y 109.45 5051.4 568 1055 36 36 42 1118 30
31Z 5051.7 569 1055 21 27 1118 15
32X 109.50 5035.2 514 1056 12 12 18 993 12
32W 5035.5 515 1056 24 30 993 24
32Y 109.55 5052.0 570 1056 36 36 42 1119 30
32Z 5052.3 571 1056 21 27 1119 15
33X 109.60 1057 12 994 12
33Y 109.65 5052.6 572 1057 36 36 42 1120 30
33Z 5052.9 573 1057 21 27 1120 15
34X 109.70 5035.8 516 1058 12 12 18 995 12
Code of Federal Regulations 802
34W 5036.1 517 1058 24 30 995 24
34Y 109.75 5053.2 574 1058 36 36 42 1121 30
34Z 5053.5 575 1058 21 27 1121 15
35X 109.80 1059 12 996 12
35Y 109.85 5053.8 576 1059 36 36 42 1122 30
35Z 5054.1 577 1059 21 27 1122 15
36X 109.90 5036.4 518 1060 12 12 18 997 12
36W 5036.7 519 1060 24 30 997 24
36Y 109.95 5054.4 578 1060 36 36 42 1123 30
36Z 5054.7 579 1060 21 27 1123 15
37X 110.00 1061 12 998 12
37Y 110.05 5055.0 580 1061 36 36 42 1124 30
37Z 5055.3 581 1061 21 27 1124 15
38X 110.10 5037.0 520 1062 12 12 18 999 12
38W 5037.3 521 1062 24 30 999 24
38Y 110.15 5055.6 582 1062 36 36 42 1125 30
38Z 5055.9 583 1062 21 27 1125 15
39X 110.20 1063 12 1000 12
39Y 110.25 5056.2 584 1063 36 36 42 1126 30
39Z 5056.5 585 1063 21 27 1126 15
40X 110.30 5037.6 522 1064 12 12 18 1001 12
40W 5037.9 523 1064 24 30 1001 24
40Y 110.35 5056.8 586 1064 36 36 42 1127 30
40Z 5057.1 587 1064 21 27 1127 15
41X 110.40 1065 12 1002 12
41Y 110.45 5057.4 588 1065 36 36 42 1128 30
41Z 5057.7 589 1065 21 27 1128 15
42X 110.50 5038.2 524 1066 12 12 18 1003 12
42W 5038.5 525 1066 24 30 1003 24
42Y 110.55 5058.0 590 1066 36 36 42 1129 30
42Z 5058.3 591 1066 21 27 1129 15
43X 110.60 1067 12 1004 12
43Y 110.65 5058.6 592 1067 36 36 42 1130 30
43Z 5058.9 593 1067 21 27 1130 15
44X 110.70 5038.8 526 1068 12 12 18 1005 12
44W 5039.1 527 1068 24 30 1005 24
44Y 110.75 5059.2 594 1068 36 36 42 1131 30
44Z 5059.5 595 1068 21 27 1131 15
45X 110.80 1069 12 1006 12
45Y 110.85 5059.8 596 1069 36 36 42 1132 30
45Z 5060.1 597 1