IRS or INS indicates : Drift: 6°L (left)

[manucordier]

Hello,

If my IRS or INS indicates "Drift: 6°L", what does that mean ?

Option1: That I am drifting 6° to the left of the required track, so I should apply a drift correction angle to the right because the wind is coming from the right.

Option 2: or it means that I have a 6° Drift Correction Angle applied to the left of my required track (in other words, the aircraft nose is positioned to the left of the required track) and that is allright because I have wind coming from the left.

Which of both options is right ? Or maybe both are wrong ?

Thank you very much to whom will help me with that one.

Emmanuel.

[GKaplan]

Option 1 I'd say.
At least that what my box means when it says that (it's neither IRS nor INS, but indications should be similar).

[jfkjohan]

This is possibly the first time on Pprune that i'm ever actually trying to help on a subject so here goes.

With XTK/TKE set on your INS, it would either show you the first value which would be the amount in nautical miles off track you are (either left/right of the desired track) and the second value would show you the correction angle to regain your desired track (if needed).

Example XTK/TKE set and displayed 6.0 L / 35" and you wanted to make good a track of 090 degrees true (T), (heading due east), your aircraft would be on a current heading of 055 degrees (T). To correct, you would steer right by 35" and voila. TKE would then show 0.

Of course, you still have a XTK / cross track error of 6.0nm to the L but at least you would be making good a track parallel to your desired track. You can figure out how you want to regain track in another lesson. Hehe. (Tip : Track Error + Closing Angle = Track to Intercept)

Maybe you were thinking "drifting" as in your aircraft veering to the left of track as per my example above?

BTW I am still a freshie at this so I could again, be totally wrong on this one!

I'm sure others with more experience would follow up on this. I can then learn with you too!

Good luck!

Johan @ JFK

Johan Farid Khairuddin.com (http://www.johanfaridkhairuddin.com)

[welliewanger]

jfkjohan,
I don't think the question was about XTK/TKE, it was about drift.

Apply the KISS principle (keep it simple stupid!)

Emmanuel,
You're also overcomplicating things. The drift value the system gives you is, erm, how much you're drifting! It's the difference between your heading and your track. For example:
HDG: 090
Wind from: 000
Track: 100

In this example, the wind (from the North) is blowing you slightly Southbound. You are drifting 10 degrees right.

Unlike in your possible answers, it's not telling you anything about a "required" track. It's just telling you the difference between your heading and your track.

HTH

[jfkjohan]

Apply the KISS principle (keep it simple stupid!)

Hi welliewanger - Thanks so much. Learnt from it! It was my first time trying to help on Pprune. I'm sure I might have overdone it! Haha

Johan

[welliewanger]

Hey Johan,
No probs. I once heard someone say something like "The scariest thing is a man who knows he's right." There's not enough open minded people on this forum.

[jfkjohan]

"The scariest thing is a man who knows he's right."

Hi Welliewanger,

If its anything, i'd know i'd always be wrong until proven right either by a) myself or b) by others. Also hopefully with more constructive criticism received, less would be the later of the two.

Thank you for sharing that quote as well.

God bless you and have a good weekend.

Regards,
Johan.