Publication: Magyar Közlöny
Issue: MK-2007-70 (Year: 2007, Number: 70)
Era: 2004-2010
Section: Melléklet a 2007. évi XLVI. törvényhez
Paragraph Index: 3833

2. Practical aspects of reliability and availability 2.1 Measurement of reliability and availability 2.1.1 Reliability. The value that is obtained for MTBF in practice must of necessity be an estimate since the measurement will have to be made over a finite period of time. Measurement of MTBF over finite periods of time will enable Administrations to determine variations in the reliability of their facilities. 2.1.2 Availability. This is also important in that it provides an indication of the degree to which a facility (or group of facilities) is available to the users. Availability is directly related to the efficiency achieved in restoring facilities to normal service. 2.1.3 The basic quantities and manner of their measurement are indicated in Figure F-2. This figure is not intended to represent a typical situation which would normally involve a larger number of inoperative periods during the specified operating time. It should also be recognized that to obtain the most meaningful values for reliability and availability the specified operating time over which measurements are made should be as long as practicable. 23/11/06 ATT F-4 2007/70/II. szám Attac ment Annex 10 — Aeronautical Communications erating on-o erating ecified o erating time Actual o erating time = a a a a a a = o erating eriod on-o erating time = s s f f f s = sc eduled s utdo n eriod f = failure eriod ecified o erating time = um of actual o erating time and non-o erating time n n n a1 s1 a f1 a3 f a f3 a f f a a Figure F-2. Evaluation of facility availability and reliability 2.1.4 Using the quantities illustrated in Figure F-2, which includes one scheduled shutdown period and five failure periods, one may calculate mean time between failures (MTBF) and availability (A) as follows: Let: a1 + a2 + a3 + a4 + a5 + a6 + a7 = 5 540 hours s1 = hours f1 = 2½ hours f2 = hours f3 = hours f4 = hours f5 = 2½ hours Specified operating time = 5 580 hours Actual operating time MTBF = Number of failures = i a ¦ 5 540 = = 1 108 hours ATT F-5 23/11/06 2007/70/II. szám Annex 10 — Aeronautical Communications Volume I Actual operating time u 100 A = Specified operating time = i i i a a s f i i i u   ¦ ¦ ¦ 5 540 = 5 580 u 100 = 99.3 per cent ___________________ 23/11/06 ATT F-6 2007/70/II. szám ATTACHMENT G. INFORMATION AND MATERIAL FOR GUIDANCE IN THE APPLICATION OF THE MLS STANDARDS AND RECOMMENDED PRACTICES 1. Definitions (see also Chapter 3, 3.11.1) namic side lobe level. The level that is exceeded 3 per cent of the time by the scanning antenna far field radiation pattern exclusive of the main beam as measured at the function scan rate using a 26 kHz beam envelope video filter. The 3 per cent level is determined by the ratio of the side-lobe duration which exceeds the specified level to the total scan duration. Effective side lobe level. That level of scanning beam side lobe which in a specified multipath environment results in a particular guidance angle error. S point . A point 2.5 m (8 ft) above the runway centre line and 900 m (3 000 ft) from the threshold in the direction of the azimuth antenna. S point E. A point 2.5 m (8 ft) above the runway centre line and 600 m (2 000 ft) from the stop end of the runway in the direction of the threshold. Standard receiver. The airborne receiver model assumed in partitioning the MLS error budgets. The salient characteristics are: (1) signal processing based on the measurement of beam centres; (2) negligible centring error; (3) control motion noise (CMN) less than or equal to the values contained in Chapter 3, 3.11.6.1.1.2; (4) a 26 kHz bandwidth 2-pole low pass beam envelope filter; and (5) angle data output filtering by a single pole, low pass filter with a corner frequency of 10 radians per second. 2. Signal-in-space characteristics — angle and data functions 2.1 Signal format organization 2.1.1 The signal format is based on time-division multiplexing wherein each angle guidance function is transmitted in sequence and all are transmitted on the same radio frequency. The angle information is derived by measuring the time difference between the successive passes of highly directive, unmodulated fan beams. Functions may be transmitted in any order. Recommended time slots are provided forthe approach azimuth, approach elevation, flare, and back azimuth angle functions. Preceding each scanning beam and data transmission is a preamble which is radiated throughout the coverage volume by a sector antenna. The preamble identifies the next scan function and also synchronizes the airborne receiver signal processing circuits and logic. 2.1.2 In addition to the angle scan function, there are basic and auxiliary data functions, each with its own preamble, which are also transmitted from the sector antennas. The preamble permits each function to be recognized and processed independently. Consequently, functions can be added to or deleted from the ground configurations without affecting the ANNEX 10 — VOLUME I ATT G-1 23/11/06 2007/70/II. szám Annex 10 — Aeronautical Communications Volume I 23/11/06 ATT G-2 operation of the receiver. The codes used in the preamble and data functions are modulated by differential phase shift keying (DPSK). 2.1.2.1 PS data signal characteristics. The DPSK data are transmitted by differential phase modulation of the radio frequency carrier with relative phase states of 0 or 180 degrees. The DPSK data signal has the following characteristics: data rate — 15.625 kHz bit length — 64 microseconds logic “0” — no phase transition logic “1” — phase transition 2.1.3 Examples of the angle function organization and timing are shown in Figures G-1 and G-2.* Details and definitions of the data items shown in Figure G-1 are given in Chapter 3, 3.11.4.8. 2.1.4 The sequences of angle guidance and data transmissions shown in Figures G-3A, G-3B and G-3C have been demonstrated to provide sufficient freedom from synchronous interference. 2.1.4.1 The structure of these sequences is intended to provide sufficient randomization to preclude synchronous interference such as may be caused by propeller rotation effects. 2.1.4.2 The sequence pair shown in Figure G-3A accommodates the transmission of all functions. Any function not required may be deleted so long as the remaining functions are transmitted in the designated time positions. 2.1.4.3 The sequence pair shown in Figure G-3B accommodates the high rate approach azimuth function. Any function not required may be deleted so long as the remaining functions are transmitted in the designated time positions. 2.1.4.4 Figure G-3C shows the complete time multiplex transmission cycle which may be composed of the sequence pairs from Figure G-3A or from Figure G-3B. The open time periods between sequences can be used for the transmission of auxiliary data words as indicated. Basic data words also may be transmitted in any open time period. 2.1.4.5 Sufficient time is available in the cycle shown for the transmission of the basic data and the auxiliary data defined in words A1-A4, B1-B39, B40-B45 and B55, provided that data are also transmitted during unused time slots or slots devoted for data words within the sequences. 2.1.4.6 More efficient sequences may be designed by adjusting the timing within the sequences and the inter-sequence gaps to allow the transmission of additional auxiliary data words. Such sequences must be designed to provide equivalent freedom from synchronous interference as the sequences shown in Figures G-3A, G-3B and G-3C. Frequency domain analysis techniques may be utilized to demonstrate that alternative sequences are sufficiently randomized. 2.2 Angle guidance parameters 2.2.1 The angle guidance parameters that define the MLS angle measurement process are specified in Chapter 3, 3.11.4.5. Two additional parameters that are useful in visualizing the operation of the system are the midscan time (Tm) and the pause time. They may be derived from the Chapter 3 specifications and are shown for reference in the following table. * All figures are located at the end of the Attachment. 2007/70/II. szám Attac ment G Annex 10 — Aeronautical Communications Signal format midscan and pause times (see Figure G-2) Midscan1 Pause time, Tm time Function ( s) ( s) Approach azimuth 7 972 High rate approach azimuth 5 972 Back azimuth 5 972 Approach elevation 2 518 Flare elevation 2 368 1 Measured from the receiver reference time (see Appendix A, Table A-1). 2.2.2 Function timing accuracy. Because of the inaccuracy in the determination of the reference time of the Barker code, and because the transmitter circuits smooth the phase or amplitude during phase transitions of the DPSK modulation, it is not possible to determine the timing of the signal with an accuracy better than 2 microseconds from the signal-in-space. It is therefore necessary to measure the timing accuracy specified in Chapter 3, 3.11.4.3.4 on the ground equipment. Suitable test points should be provided in the ground equipment. 2.3 Azimuth guidance functions 2.3.1 Scanning conventions. Figure G-4 shows the approach azimuth and back azimuth scanning conventions. 2.3.2 Coverage requirements. Figures G-5 and G-6 illustrate the azimuth coverage requirements specified in Chapter 3, 3.11.5.2.2. 2.3.2.1 When the approach or back azimuth antenna sites are necessarily offset from the runway centre line, the following factors should be considered:

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