Ground speed

Originally posted by Moggy C
Modesty should forbid me denying that I know what your are talking about, but, never having failed an exam, – no I don’t 🙂

Moggy

Not sure what his point was either, Moggy! Maybe it’s his irony re-surfacing again!;)

LOL

Originally posted by R.weaver

Im sure you know what im talking about Moggy,EH???

Modesty should forbid me denying that I know what your are talking about, but, never having failed an exam, – no I don’t 🙂

Moggy

Yes well I was sitting next to a file of answers in the examination where I was left on my own for the hour, but cheating might not be the answer. Me cheat no, im far to decent adnd far above for that he says as he looks for nav answers. No I know where I went wrong, I will retake at the start Of April and I WILL PASS THE NAV NEXT TIME. It ws a bit of a shcok failing an exam.

Im sure you know what im talking about Moggy,EH???

Regards

R.weaver

Safe legal flying

Poor old r has to learn this stuff to pass his exams.

It is of little practical use, he’ll end up like the rest of us, checking the time it takes him to reach a ‘quarter of the way there’ waypoint and then multiplying the error by three to give him his ETA.

Moggy

sorry to add another post below 🙂

End of the day you have to use a method you are comfortable with and one that is as safe as practically possible i.e. no head down in cockpit for prolonged periods, and if this means using a calculator then so be it, but there are arguments for not “losing” the necessary practical skills that has been developed in using “traditional” methods and which is a view I fully back, its the same old arguement about manual navigation or GPS? 🙂

Dean

Id never use a whizzwheel in the air to be honest, i would use that method i just stated above ^ or something i did on my skills test was draw a compass on my plog with different wind correction angles going around the spoke for that particular heading plus the groundspeed along side, it actually looked quite neat hehe.

whizzwheel

Why do student pilots still have to do this stuff? What’s wrong with an electronic calculator? I know the battery can run out, but I think trying to use the wheel in the air while flying the aeroplane and keeping a good lookout is next to impossible. Surely a calculator would be less error prone when doing your planning?
It’s like being told you can’t use a computer at work, you have to write all your letters by hand and do calculations in your head rather than use a spreadsheet.
Is it time to consign these things to history where they belong?

What do you all think?:)

I know this wasnt in the original question but this method may help whilst in flight Robert for diversions etc.

as for a headwind component in a crosswind use the clock method for quick reference for diversions, if you are flying a heading of 270 deg and the wind is 225/20 then the heading difference is 45 deg, so look on your watch and say that 45 is ¾ the way round clock face so take ¾ of the wind for crosswind so thats 15kts xwind and 5 kts headwind, and for 15 deg difference in heading to wind direction you take ¼ of the wind speed for xwind and ¾ for headwind, and if wind is 30 deg off heading then you take ½ and ½, same applies for a tail wind too 🙂 once you deciphered this info you can then work out your groundspeed easliy by adding (if its tailwind) or subtracting (if its a head wind) the head/tail components from your TAS.

D.

Okay, when you do have your CRP-1 to hand…

Using the circular scale, set the wind direction against the index mark. In this case, 090 degrees.

Adjust the sliding scale until you have the 100 knot arc directly under the centre point of the circular scale.

Using a chinagraph pencil (sharpened for accuracy), mark a cross on the transparent surface of the circular scale, at the point on the sliding scale centre line which is 10 knots down from the centre point.

You have now set the wind.

Now turn the circular scale so that your heading (in the first example this is 180 degrees) shows against the Index mark.

Set your TAS under the centre dot, and simply read off the ground speed from under the wind mark. In this case, your ground speed will also be 100 knots, as you have a pure cross wind which neither adds to nor detracts from your TAS.

In the second example, heading 135 degrees, you should show a ground speed of 93 knots. The third example (heading 215 degrees) will give you a ground speed of 106 knots.

Of course, you then also have to consider drift, but as you were only asking about the air speed / ground speed calculation, I’ve left that part out. Let me know if you want me to cover that element too.

Steve

I dont have my crap one with me so for your answers just add the wind onto the headings and reas off the drift. I have it now, I think.

Cheers again Steve

Regards

R.weaver

Safe legal flying

Any other methods welcome

Not easy to explain on a forum I’m afraid. Your best bet is going to be to sit with your instructor and work through one or two examples.

Still, as a general rule of thumb….

Example 1 – Wind 090/10kts. IAS 100kts, heading 090. (answer to this one is that your ground speed will be 90kts, as you’re flying directly into the headwind).

Example 2 – Wind 090/10kts. IAS 100kts, heading 270. (answr to this one is that your ground speed will be 110kts, as you now have a 10kt tailwind.)

Happy with the logic behind those? If so, good. Try these three on your own, and I’ll log on when I get home later (where my CRP1 is!) and let you know my answers.

Q1 – Wind 090/10kts. IAS 100kts, heading 180.

Q2 – Wind 090/10kts. IAS 100kts, heading 135.

Q3 – Wind 090/10kts. IAS 100kts, heading 215.

See how you get on with those.