Air Information Publications — Page 23, Lesson 31

I want to walk you through the Air Information Publications section, specifically the table of radio navigation and landing aids. Let's start with the ILS at Bournemouth. Bournemouth has a Category I Instrument Landing System, or ILS, for runways 08 and 26. Category I means it provides guidance down to a decision height of 200 feet. For runway 08, the localizer call sign is I BMH; for runway 26, it's I BH. The localizer frequency for either runway system is 110.50 MHz. The paired glide path frequency for each runway is 329.60 MHz. The ILS hours of operation are denoted as HO, which means the service is available to meet operational requirements—essentially, it's on when needed, not on a fixed schedule. The antenna coordinates are published in the remarks column, given in degrees, minutes, seconds, and hundredths of latitude and longitude. That's a precise position for the antenna installation. The remarks column also states that the glide slope for each ILS is 3°. That's the standard glide path angle. It also gives the ILS Reference Datum Height—often abbreviated as Ref Datum Hgt—for runway 08 as 53 feet, and for runway 26 as 50 feet. Let me define that term precisely: the ILS reference datum point is a point at a specified height, around 50 feet, located vertically above the intersection of the runway centre line and threshold, through which the downward extended portion of the ILS glide path extends. In plain terms, it's the point above the runway threshold where the glide path crosses at that height—typically where the aircraft's wheels would be at touchdown. The remarks column also publishes localizer limitations for runway 08, and for the ILS on runway 26 it states that "the quality of guidance provided does not permit use of the facility for coupled approaches below 350 ft." That means you cannot use the autopilot or flight director coupled to the ILS for an automatic approach below 350 feet on runway 26—the signal quality degrades below that altitude. Now, moving to the next item in the table. The letter L in the Type column indicates that the airfield has a low-powered Non-directional Beacon, known as a Locator, sited on the aerodrome at the published latitude and longitude. Its call sign is BIA, frequency 339 kHz, and operational hours H24—that means continuous service, 24 hours a day. The range is 20 NM, which is the promulgated range or Designated Operational Coverage, abbreviated DOC. Let me read you the definition of DOC as given in the excerpt: "The range promulgated for UK NDBs is based upon a daytime signal protection ratio between wanted and unwanted signals that limits bearing errors at that distance to +/- 5°. At ranges greater than those promulgated, bearing errors will increase. Adverse propagation conditions, particularly at night, will also increase bearing errors. This protection takes into account average atmospheric noise but not night-time sky waves." So the 20 NM range is a daytime figure. If you fly beyond that range, bearing errors grow. At night, sky-wave propagation can cause even larger errors. The excerpt directs you to see the latest AIC—Aeronautical Information Circular—on Radio Navigation Aids - Designated Operational Coverage for the most current data. Next, the DME, or Distance Measuring Equipment. It is frequency-paired with the ILS—I BMH for runway 08 and I BH for runway 26. The channel number is 42X, which is the selection for military TACAN-equipped aircraft. TACAN stands for TACtical Air Navigation—it's a military system that provides both bearing and distance. The operational hours are HO, same as the ILS, and the aerial elevation is 44 feet AMSL—Above Mean Sea Level. In the remarks column, it states that zero range is indicated at the threshold of runway 26, and 160 metres before crossing the threshold of runway 08. That means when the DME reads zero, you are at the threshold for runway 26, but for runway 08 you still have 160 metres to go before you cross the threshold. That's important for approach planning. Finally, the excerpt lists other sources of this information. Publications such as Aerad and Jeppesen Flight Guides, Low and High Level Airways Charts, Arrival and Departure Charts, and Airfield Approach Charts all provide information on airfield opening hours, handling, communication, and radio navigation and landing aids. These are commercial or supplementary sources you'll use alongside the official AIP.