I came across a question in the online practice exam regarding syllabus item 2.7.4.3 [d] which relates to ground speed checks.

It's probably a bit of common sense, but are there any guidelines regarding the use of suitable features to perform ground speed checks with? If I remember correctly the question gave options of homesteads, rivers and roads at various distances from the initial fix.

Thanks, H

Hi henrik,

No guidelines reeeeeally.. So long as you're sure the features you're seeing are the features you're using to calculate your groundspeed!

Best thing to do though is to use prominent features that aren't easily mistaken, ie. dams, large road intersections, highways, things like that.

Good luck

Hey, just letting you know that i did my test on wed and there were no such questions in my own exam, any q that req figuring things out gave the g/s. a couple of 1 in 60's, quite easy and all two marks. Were a few q's on bod and eod and also similar ones to the bod and eod and a planned flight asking the max hrs possible for flight etc. Pretty straight forward and nothing you wont have seen in the text.

Rossy

There are a couple of points worth remembering for ground speed checks.

1. Don't attempt to check you ground speed over a short distance. It is impossible to get an accurate ground speed over a distance like 20nm. You cannot time it accurately enough and one minute would make a huge difference to the answer. The longer the distance the better, but don't waste you time if the distance is any less than 30nm.

2. Pick a line feature [straight river, road or railway line] that crosses you track an approximately right angles. That allows you to be a little left or right of track and still get an reasonably accurate ground speed. A line feature that crosses track at a shallow angle will give very different answers if you are a little left or right of track.

3. Don't use an abeam feature if it is more than a couple of miles off track. It's surprisingly difficult to accurately assess when you are abeam a feature that is a long way off track unless you use a nav aid such as ADF or VOR.

Anyway why not just check your GPS????