View Full Version : Track correction 'By scientific method only'
18th Jun 2010, 14:10
I'm flying x-country and I see a lake in the distance and I should be heading towards it but I'm not.
I was told by one instructor just go there. Another told me I can't deviate from my original track (written down on the plan) unless I change it by scientific method only.
Problem is I don't really know how many miles off track I am off yet, might not know until I get a bit closer. If I take a guess at how many miles I will be off, what if I don't know my exact position at present (i.e how many miles since last checkpoint and how many miles to the lake), how can I do the 1 in 60from this present position, guess everything? Seems to me it would make a lot more sense to just fly to the checkpoint if you can see it.
Just wondering what the examiners take might be on it.
18th Jun 2010, 15:45
The "scientific method" is called Dead Reckoning or Heading Hold; the other is a track crawl.
It depends on whether the examiner has asked you to fly a leg as a heading hold or a track crawl; in which case, you do as asked!
On your map, draw 5 and 10 degree fan lines either side of your heading and draw the half-way and quarter-way points. These will give you an idea of the correction you need to make. For example, if at half way, you estimate yourself to be 7 degrees off course, then you'll need to make a correction of 14 degrees in your heading. And yes, much of it is based on guess-timations but they do become more educated with practice and experience.
Track Crawl though is what most people sorry, helicopter pilots do in real life!!!
18th Jun 2010, 17:29
Thanks Whirly, I was avoiding using the fan lines to keep the map clutter free but will give it a go
18th Jun 2010, 18:24
Find an instructor who can explain the 'Standard Closing Angle' technique and FORGET all those fan lines, half- and quarter-way lines in the middle of nowhere. Such techniques were taught in the 1960s and have long since been replaced by simpler techniques....
If you see a feature ahead which you can guarantee is on track, then simply fly to it. But you'd better be certain!
I was told by my Army Chipmunk instructor, as soon as you recognise the destination, fly straight towards it.
By all means do the scientific thing as an exercise, but the whole point of navigation is the above.
PS The point of paralleling the track is simply to make sure you don't get any further off track while you work things out.
From my non professional not an instructor take it with a pinch of salt you're liable for airspace busts if it doesn't work out point of view...
Fan lines are bo**ocks. Far too many lines on your map (ever tried flying around London with fan lines criss crossing the Heathrow CTA?), very complicated and easy to slip up.
BEagle is right on - learn the standard closing angle. It's idiot simple, works a treat and requires maths no more comlicated than your 2x table. It has been neatly summised in a previous thread thus:
To give an estimate how far off track you are, at landmarks on your track draw at 90degs to the track line a "known" length - depending on the track distance I generally go for 6nm (3nm either side of track) or 10nm (5nm either side of track). When abeam said landmark, work out how far off you are and go from there. As long as your windage wasn't drastically wrong to start with you should never be more than about 5nm off track at any given point - but be aware of compound error, etc.
My 0.02c, try it with an instructor first, etc. But SCA is taught by the RAF, and if it's good enough for them...
19th Jun 2010, 20:21
My flight training school's preferred technique at CPL level was the standard closing angle.
The CAA examiner was more than happy with my use of it during my test and in the pre-exam questioning.
There are a few techniques, however most of the older scientifc techniques are designed such that when you recognise you are off track, you go straight from that point to your destination. In essence once off track, you never actually get back onto your original intended path.
On face value that's not a problem, however.....
Let's assume your intended path passes 2 miles north of a danger zone or controlled airspace. All of a sudden finding you are 2 miles south of your intended track, accepting a gradual track to your destination is no longer appropriate. The standard closing angle method is far better because you regain your planned and therefore "safe" route.
I real life and non exam world, if you can see the socking great big lake which is on your route, you fly to it, however in exam world, that's not really a good enough test of one's navigational ability!