Teaching SCA as a method

[Dan Winterland]

DFC, I'm not sure you understand what BEagle is saying. He wrote "Let us imagine that we have been accurately flying the first leg of our navigation exercise at 90 kts on a heading of 040° when we notice that we are 4 miles left of track". You wrote "In the second case the pilot first corrects the error and then applies the SCA".

BEagle has told us that we have been flying accurately, therfore the error is not through flying an incorrect heading - it's down to applying the wrong drift correction, probably due to an inaccurate forecast. If this is the case, the correction needs to be applied when back on track. If the error is because we realise we have been flying the wrong heading for whatever reason, then it's quite obvious that we will have to make some sort of heading correction before applying the SCA.

You actually demonstrate this in your second diagram where you show a heading adjustment, whereas your first diagram is incorrect in that if you continued on your original heading, you will in fact still diverge from track. You do however, correctly state that the heading error itself will lead to a slight displacement. However, this will be small and in the overall scheme of things, accurate enough to get you within visual range of your next turning point.


SCA does work very well in practice. The technique was designed for military pilots operating in the low level environment where navigation is made far more difficult because you can't see your turning or check points until you are close to them and also because the workload is high. When you determine you have a track displacement error, you have to decide what caused it. Was it a cumulative error down to innacurate drift calculation, or was it a once only error due to having to avoid weather/a SAM site or as a result of evading an enemy fighter? In the former, a correction has to be made before applying the SCA , in the latter - the original heading was probably good and no correction is neccessary.

I learnt it when I trained in the RAF and then later taught it as an RAF QFI for 6 years. With lots of experience of the SCA, I would say it's a very good technique. Although it's probably of more relevance in a Tucano flying at 250' at 240knts, it is still very valid at lower speeds. Thats why I later taught it in the flying club environment. I found it superior and easier for a student to apply than other techniques such as the new track reference.