时间：2011-04-18 00:47来源：蓝天飞行翻译 作者：航空 点击：次
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FIG 1.1.10 Coverage Volumes 3.D Representation 3.Environment. The system has low suscepti-bility to interference from weather conditions and airport ground traffic. 4.Channels. MLS has 200 channels. enough for any foreseeable need. 5.Data. The MLS transmits ground.air data messages associated with the systems operation. 6.Range information. Continuous range in-formation is provided with an accuracy of about 100 feet. 1.1.12. NAVAID Identifier Removal During Maintenance During periods of routine or emergency maintenance, coded identification (or code and voice, where applicable) is removed from certain FAA NAVAIDs. Removal of identification serves as a warning to pilots that the facility is officially off the air for tune.up or repair and may be unreliable even though intermittent or constant signals are received. NOTE. During periods of maintenance VHF ranges may radiate a T.E.S.T code (-... -). 1.1.16 Navigation Aids NOTE. DO NOT attempt to fly a procedure that is NOTAMed out of service even if the identification is present. In certain cases, the identification may be transmitted for short periods as part of the testing. 1.1.13. NAVAIDs with Voice a.Voice equipped en route radio navigational aids are under the operational control of either an FAA Automated Flight Service Station (AFSS) or an approach control facility. The voice communication is available on some facilities. Hazardous Inflight Weather Advisory Service (HIWAS) broadcast capability is available on selected VOR sites throughout the conterminous U.S. and does not provide two-way voice communication. The avail-ability of two-way voice communication and HIWAS is indicated in the A/FD and aeronautical charts. b.Unless otherwise noted on the chart, all radio navigation aids operate continuously except during shutdowns for maintenance. Hours of operation of facilities not operating continuously are annotated on charts and in the A/FD. 1.1.14. User Reports on NAVAID Performance a.Users of the National Airspace System (NAS) can render valuable assistance in the early correction of NAVAID malfunctions by reporting their observations of undesirable NAVAID performance. Although NAVAIDs are monitored by electronic detectors, adverse effects of electronic interference, new obstructions or changes in terrain near the NAVAID can exist without detection by the ground monitors. Some of the characteristics of malfunction or deteriorating performance which should be reported are: erratic course or bearing indications; intermittent, or full, flag alarm; garbled, missing or obviously improper coded identification; poor quality communications reception; or, in the case of frequency interference, an audible hum or tone accompanying radio communications or NAVAID identification. b.Reporters should identify the NAVAID, loca-tion of the aircraft, time of the observation, type of aircraft and describe the condition observed; the type of receivers in use is also useful information. Reports can be made in any of the following ways: AIM 1.Immediate report by direct radio communica-tion to the controlling Air Route Traffic Control Center (ARTCC), Control Tower, or FSS. This method provides the quickest result. 2.By telephone to the nearest FAA facility. 3.By FAA Form 8740.5, Safety Improvement Report, a postage.paid card designed for this purpose. These cards may be obtained at FAA FSSs, Flight Standards District Offices, and General Aviation Fixed Base Operations. c. In aircraft that have more than one receiver, there are many combinations of possible interference between units. This can cause either erroneous navigation indications or, complete or partial blanking out of the communications. Pilots should be familiar enough with the radio installation of the particular airplanes they fly to recognize this type of interference. 1.1.15. LORAN a. Introduction 1. The LOng RAnge Navigation.C (LORAN) system is a hyperbolic, terrestrial.based navigation system operating in the 90.110 kHz frequency band. LORAN, operated by the U.S. Coast Guard (USCG), has been in service for over 50 years and is used for navigation by the various transportation modes, as well as, for precise time and frequency applications. The system is configured to provide reliable, all weather navigation for marine users along the U.S. coasts and in the Great Lakes. 2. In the 1980’s, responding to aviation user and industry requests, the USCG and FAA expanded LORAN coverage to include the entire continental U.S. This work was completed in late 1990, but the LORAN system failed to gain significant user acceptance and primarily due to transmitter and user equipment performance limitations, attempts to obtain FAA certification of nonprecision approach capable receivers were unsuccessful. More recently, concern regarding the vulnerability of Global Positioning System (GPS) and the consequences of losing GPS on the critical U.S. infrastructure (e.g., NAS) has renewed and refocused attention on LORAN. 3. LORAN is also supported in the Canadian airspace system. Currently, LORAN receivers are only certified for en route navigation. Navigation Aids 1.1.17 4. Additional information can be b. LORAN Chain found in the “LORAN.C User Handbook,” 1. The locations of the U.S. and Canadian COMDT PUB.P16562.6, or the website LORAN transmitters and monitor sites are illustrated http://www.navcen.uscg.gov. in FIG 1.1.11. Station operations are organized into subgroups of four to six stations called “chains.” One station in the chain is designated the “Master” and the others are “secondary” stations. The resulting chain based coverage is seen in FIG 1.1.12. FIG 1.1.11 U.S. and Canadian LORAN System Architecture FIG 1.1.12 LORAN Chain Based Coverage 1.1.18 Navigation Aids 2.The LORAN navigation signal is a carefully structured sequence of brief radio frequency pulses centered at 100 kHz. The sequence of signal transmissions consists of a pulse group from the Master (M) station followed at precise time intervals by groups from the secondary stations, which are designated by the U.S. Coast Guard with the letters V, W, X, Y and Z. All secondary stations radiate pulses in groups of eight, but for identification the Master signal has an additional ninth pulse. (See FIG 1.1.13.) The timing of the LORAN system is tightly controlled and synchronized to Coordinated Universal Time (UTC). Like the GPS, this is a Stratum 1 timing standard. |
