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I am going through my cpl nav KDR and wanted to clarify a few things.
If asked for a track change when doing a 1 in 60 but they have only given you one distance off track, between 2 track distances, you just calculate the CA right?
Secondly, if given the degrees off track and time at point a (1200) and b (1220, b being the point off track), how can i calculate ETA and distance to C?
Lastly, when calculating Roc and rod, I'm getting confused with the corresponding nm steps to the LLs and discerning differences. Plus, I just want to make sure that to remain within CTA, I should +500ft, even if the question does not state it?
Bob Taits admin replied the topic: Calculating track change
Firstly apologies I'm doing this from my phone.
Q1 without seeing an actual question, theb1:60 requires you to calculate Track error, which will then have you parallel your original track. Secondly the closing angle to regain track to destination.
Q2. Your off track and have been delayed to that point by 20 minutes. V=D/t so work out your ground speed or better still wind velocity if the question gives you this information. Then calculate your ETI from the off track point to the destination.
Q3. In real life yes you need to maintain +500 to the step. Question wise I would need examples to help. The questions love trickery in the wording.
Appreciate it. What I mean for question 1 is that they have provided 2 distances (D1 20m and D2 30nm) and only one position off track (i.e. 5nm). Do I just use this to calculate both te and CA or just ca?
For the second question, I'm asking moreso, if provided with an angle off track, rather than a distance, how to calculate time from this and create a distance from it.
WayneJ replied the topic: Calculating track change
Hi Kejt,
The basics of the 1 in 60 is Heading change is the Track Error (TE) plus Closing Angle (CA). TE is calculated on your first distance D1 and distance off track . CA is calculated on D2 distance to rejoin track and distance off track.
Re Q2. In part 91 MOS, in nav it talks about 1 in 60 rule and simple mental maths. Bob Tait's examles often gives a question telling you the degrees Off track and Heading change. From these two numbers, you can determine what the CA is. Now if these two angles (TE and CA) are the same, the distance from A to B and B to C must be the same. As we consider that the Ground Speed with these calculations does not change, then the time from A to B must be the same as B to C! Eta is then B plus the time interval.
If the CA is half or double of the TE, the distance changes by the same proportion. Easy to understand of you draw a couple of examples.
If there is only 1 distance off track provided and I want to find a heading change. How would I do this? I can't calculate both te and ca from it so I don't understand what to do.
So for this question:
Secondly, if given the degrees off track and time at point a (1200) and b (1220, b being the point off track), how can i calculate ETA and distance to C?
If not provided with a te and I can only calculate the CA, how can I determine both time and distance?
WayneJ replied the topic: Calculating track change
Hi Kejt,
The distance given OFF track is used for both calculations TE and CA. Review page 88/89 (electronic copy)in the NAV text book and exercise N11.
re your second, this seems to be a common type question. The degrees off track is your TE, so if you are given a HDG change, you can determine the CA.. I will post a drawing later.
