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Ever wondered how aircraft navigate inflight?

Posted on January 22 2021

We’ve come a long way from the days of just compass and charts, there are several NAVAID (Navigation Aid) devices pilots rely on and one of them are VOR/DMEs.
VORs (Very high frequency Omni-directional Range) are ground stations which provide a radial from or bearing to a VOR station for an aircraft, while DMEs (Distance Measuring Equipment) provide a slant-range distance to the station, which will be longer than the ground distance as it takes into account the aircraft’s altitude. Together they provide a fixed position.
These are short- range radio navigational ground stations. In order to use these, aircraft must have the appropriate equipment and must be within line-of-sight. To identify a VOR one can check it by it’s morse code identifier or the automated voice recording stating the word ‘VOR’ followed by the station name.
Cheung Chau’s DVOR/DME is known for being the starting point for the famous approach to Kai Tak at Runway 13.
Identifier: CH
Frequency: 112.3
The ‘D’ in DVOR/DME stands for ‘Doppler’. These are advanced versions of the conventional VORs providing signals with greater quality and accuracy.
VOR/DME Fun Facts:
🔸 DME transmitters can get overloaded! If too many aircraft are trying to transmit over its ability to process, it will reduce sensitivity and not process aircraft further away. 
🔸 When choosing the new standardised system to replace the low frequency radio range, VOR/DME won over competitors due to being cheaper, not affected by static interference by lightning, and the combination being easier to use to get a location from just needing one station rather than cross referencing from 2. 
大家行山會用到指南針地圖,以地標地形找到自己於地圖上相應的位置;而於航空上則會應用幾種導航設備,其中之一是VOR / DME。
VOR(Very high frequency Omni-directional Range)為飛機提供了飛機位置相對於地面 VOR站的方位;,而DME(Distance Measuring Equipment 距離測量設備)提供了飛機到該站的傾斜距離。計算了因高度的差距,可以得出飛機離開 DME 的距離。當有了離VOR/DME 的方位和距離,飛行員便可以得知飛機在航圖上的位置。
VOR / DME 都是發射無線電的導航站,屬於設在地面上的導航設備。飛機上亦須配備適當的設備才可以解讀到VOR/DME 的訊號;並且飛機和導航站須在視線範圍內。每個 VOR導航站亦有自己的摩斯密碼,以便確保飛機所收到的訊號是來自正確的目標導航站(就好似睇電視追台時會指出現正在收看的是某某台的廣播)。
長洲的DVOR / DME是著名啟德13號跑道IGS航道的起點。
DVOR / DME中的“ D”代表“多普勒” - 是常規VOR的升級版本,可提供更高質量和準確性的信號。
VOR / DME 小知識:
🌟 如果過多的飛機連上同一個DME ,DME 會降低靈敏度,令最遠的飛機不能再使用其功能,減低過度運算的機會。 
🌟 當選擇新的標準化系統來替代低頻無線電範圍時,VOR / DME因價格便宜,不受雷電的靜態干擾影響而獲得了青睞,並且這種組合更易於使用,僅需一個地面訊號站就可以作出定位。
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