Amazing accuracy

Better navigational accuracy in the air may be approaching its limits.

For passengers travelling with scheduled airlines, times have changed, sadly, and no longer can you visit the flight deck, and see from there the views that pilots get.

New meaning to the term 'on track'.

It was not so long ago, that aircraft navigation was carried out using beacons on the ground, either on VHF, or Medium wavebands.

For longer trips with no ground aids a Navigator would plot your route using Astro (sun or the stars) navigation, until companies like Decca produced other radio systems to give you a position, but these from my memory had their problems.

Today in the modern aircraft we have Inertial Navigation Systems using laser gyros together with radio VHF back up, taking cross cuts from beacons, coupled with Distance measuring equipment to pinpoint your position, and now the magic Global Positioning System (GPS) with it`s startling accuracy.

Often with only 1000 feet between, you can see aircraft either above, or below you, often on the same track. This picture of an Emirates airline Airbus A380 was taken northbound over Turkey. The trails left behind are ice crystals which are left by the water vapour that passes through the engine, and freezes immediately at temperatures of some minus 60 degrees C.

The vortex from the wings causes the rotating trail from each engine to be disturbed, and if you pass through such disturbed air following the wake of another aircraft you often get a bump as your aircraft will be travelling at 500 MPH, some 7 miles per minute, a closing speed of 1000MPH if heading towards each other.

As the accuracy is so good these days, airlines have taken to introducing an offset of one or two miles to the left or right of track, just in case there is an error of timing, or in severe turbulence an aircraft could lose or gain the amount of separation which is between machines.

I think we get the best seats in the house!

By Bob Derham

[Bob is a Captain on a privately operated Airbus A319. Ed.]

One thought on “Amazing accuracy

  1. When learning to fly, I had an instructor who was wonderful, friendly and very experienced but often cantankerous. Sadly he passed away recently.

    On seeing a student pilot’s plan for a visual training flight, he would ask us why the plan was to fly at 2500 feet, 3000 feet or whatever altitude had been chosen. We usually had some vague answer possibly relating to the ground level, the cloud base, avoiding controlled airspace, getting good enough radio reception or some combination of those. But we had missed his point!

    “Don’t fly at 2500 feet or 3000 feet”, he would say, “because everybody else does that! Fly at 2700 feet so that you don’t fly into them!”

    Then, as quick as ever, he would go to the meta level: “I know what you are thinking! What if everybody did that? We would all be flying at 2700 feet and we would still fly into each other. But the fact is that they don’t! So you should!”

    Actually just thinking of him reminds me of other stories.

    Learning to fly “bad weather circuits” with him was like barnstorming. It felt as if we had to climb to get over the runway approach lights!

    He instructed me on some of my instrument flying. His introduction to learning to fly the hold went something like: “the reason that we fly holds is that it is a waste of time. I know, I know what you are thinking: if it is a waste of time, then why are we doing it …!”

    He also liked independent thinkers. I remember an incident soon after I had gone solo. There was a bit of a breeze and I had parked an aircraft facing in the opposite direction to all the other parked aircraft. (I think the wind must have changed.) When he noticed it, he looked up who had last flown the aircraft and made a point of seeking me out and telling me that he liked people who “used their nouse” rather than following the crowd. One remembers things like that and, to me, it is part of good instruction.

    He was a very observant instructor and I miss him.


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