Alternatives To The Instrument Landing Systems Engineering Essay

Alternatives To The Instrument Landing Systems Engineering Essay Pilots have been faced with horrors of not being able to safely carry out the whole flight envelope activities during unfavourable weather conditions. The solution was the idea of somehow aiding pilots with instruments that would help get the job done. The Instrument Landing System (ILS), being the first, did break the ice but its faults and restrictions paved way for alternatives like the MPL, JPAL, IGS and TLS amongst others. It cannot be overlooked though that the ILS is still the most common of all approaches and pilots are tested numerous times on the workings of the ILS during their flight career. The Instrument Landing System (ILS) is an instrument presented, pilot interpreted, precision approach aid. The system provides the pilot with instrument indications which, when utilised in conjunction with the normal flight instruments, enables the aircraft to be manoeuvred along a precise, predetermined, final approach path. [1] Tests of the ILS began in 1929 and the Civil Aviation Authority (CAA) authorised installation of the system in 1941 at six locations. The first landing of a scheduled U.S. passenger airliner using ILS was on January 26, 1938, as a Pennsylvania Central Airlines Boeing 247-D flew from Washington D.C. to Pittsburgh and landed in a snowstorm using only the Instrument Landing System.[2] The first fully automatic landing using ILS occurred at Bedford Airport UK in March 1964. [3] 1.1 Overview on the Instrument Landing System (ILS) The ILS uses two primary signals: a localizer for lateral guidance (VHF) operating between frequencies 108.10MHz and 111.95MHz; and a glide slope for vertical guidance (UHF) operating between 329.30MHz to 335.00MHz. The localizer provides course guidance throughout the descent path to the runway threshold from a distance of 18 NM from the antenna between an altitude of 1,000 feet about the highest terrain along the course line and 4,500 feet about the elevation of the antenna site. [4] On the other hand, the glide consists of two overlapping beam modulated at 150Hz and 90Hz. The centre line of the glideslope signal is arranged to define a glide slope of approximately 3Â ° above ground level with the beam being 0.7Â ° below the glideslope centreline and 0.7Â ° above the glideslope centreline i.e. 1.4Â ° in total. The transmitter is located 750 to 1,250 ft. down the runway from the threshold, offset 400 to 600 ft. from the runway centreline [5]. 1.2 Limitations facing the ILS The complexity of the ILS localizer and glide-slope system gives rise to its high installation cost. Also, there are topographic limitations with the ILS because of the complex siting requirements due to the sensitivity of both the localizer and glide slope systems. The localizer’s full functionality is limited due to effects from obstructions in the signal broadcast areas like hangers and large buildings and the glide-slope conversely is affected by the terrain in front of the glide-slope antenna. If terrain is sloping or uneven, reflections can create an uneven glide-path causing unwanted needle deflections. Additionally, the ILS only supports straight-in approaches since its signals are pointed in one direction by the positioning of the antennae arrays. Furthermore, the ILS suffers from frequency congestion because of a finite number of available frequencies (only 40 channels in all)[6], and has frequency modulation interference problems in some areas.[7] Also, the fact that it is not easily deployable makes it fall out of favour with the military. These main facts resulted into the development of the Microwave Landing System (MLS) with one intention only, to replace the ILS.