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HeliTorque :: View topic - Tight tolerance
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HeliTorque Forum Index » Ground School

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paddywak
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PostPosted: Wed Mar 07, 2012 6:21 pm    Post subject: Tight tolerance Reply with quote

While doing a few questions I came across this one which you would think to be simple. Have a go and see you what you get.

Given TAS = 227kt Track 316T WV 205/ 15
calculate HDG T and Ground speed.

A. 313/235
B. 312/ 232
C. 310/ 233
D. 311/230

I am using a CRP 5 and arrived at 312/230, I went for D which is wrong!

Let me know which type of computer you use, be interesting to see what others get
Happy whizzing Very Happy
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flip2
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PostPosted: Wed Mar 07, 2012 10:45 pm    Post subject: Reply with quote

Using an electronic whizz wheel, I get 312 / 232... so 'B' (by cheating).

I try to give the JAA system the benefit of the doubt wherever possible. But this level of "accuracy" raises my eyebrows. Is the forecast wind accurate and consistent to a knot? Do flight planners use whizz wheels? I understand the other arguments - the emphasis on precision, that a knot / minute / kg could be the difference between being able to do a flight or not. But still....

Anyway, back on topic: I was told several years ago that the "correct" answers were calculated using a CRP-5. I suspect that they have since moved to electronic flight planners to avoid any embarassments
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James T Lowe
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PostPosted: Thu Mar 08, 2012 7:54 am    Post subject: Reply with quote

Yup, using my own electronic flight planner spreadsheet, I concur. B. 312/232

Never used a CR(a)P-5, so I can't comment on its tolerances; but I've never really been able to use its little brother with any great precision.

The tolerances on the answer are interesting, too - there's not a lot of scope for slightly large pencil marks there, is there?

Flip - with you there - the real world reality is wind just doesn't stay precisely the same direction/speed for a 30 minute flight leg. (Let alone a 9 hour flight around a jetstream...)
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LoachBoy
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PostPosted: Thu Mar 08, 2012 10:21 am    Post subject: Reply with quote

I used to use a CRAP-5 (and did so for my CPL exams)..... suffice it to say, and has been iterated many times, the print quality on the CRAP-5 would appear demonstrably better after several pints I suspect!!!

The gradations themselves are so thick on mine that they alone can easily account for an additional knot or degree here and there...... God only knows how much variation there is if you did a tolerance stack-up on it, from a whole nav planning exercise!

I know its hard chap, but don't sweat too much on these - as Flip says, the accuracy of the data supplied in reality would likely prevent you working as accurately as some of these questions demand; and don't get me started on the manufacturing quality of the CRAP-5!

In my Nav exam, I had 3 out of the 4 answers where you would get either the heading or speed correct, but not both...... and 'best guess' came down to which you felt was more important....... being within 1 degree of the heading, or 1 knot of speed!!!
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PostPosted: Thu Mar 08, 2012 10:24 am    Post subject: Reply with quote

Time to learn mental trigonometry then... Wink
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paddywak
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PostPosted: Thu Mar 08, 2012 5:02 pm    Post subject: Reply with quote

hopefully in the exam I may have a better selection of answers to choose from, my friends that are on my course are all getting the same results as me
so it cant be us or the computer.

Trig will come into some of the questions , but with only 1hr 30 to complete the Nav exam with about 45 Questions, you need to be really quick, so if you can use the wheel then this is the fastest way.

More than a couple of minutes on a question and you risk running out of time, that all depends on what's thrown at you of course... Shocked

Thanks for the replies folks!
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LoachBoy
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PostPosted: Fri Mar 09, 2012 8:31 am    Post subject: Reply with quote

Keep us posted - there were a few 'vocal' sorts on my exams (I may possibly have been one.....), that lodged several queries during various exams, and accuracy of whizz-wheels vs spread of answers was one that came up a few times.

The guy that was running our ground school course was working very hard with the CAA to try and improve things like this, and to also include more 'H' in the CPL(H)!
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paddywak
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PostPosted: Fri Mar 09, 2012 2:05 pm    Post subject: Reply with quote

LoachBoy wrote:
Keep us posted - there were a few 'vocal' sorts on my exams (I may possibly have been one.....), that lodged several queries during various exams, and accuracy of whizz-wheels vs spread of answers was one that came up a few times.

The guy that was running our ground school course was working very hard with the CAA to try and improve things like this, and to also include more 'H' in the CPL(H)!


I like it! more H , that would be nice, ill let you all know what happens next week, watch this space.
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Pogue
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PostPosted: Fri Mar 09, 2012 3:49 pm    Post subject: Reply with quote

OK, I'm late to the party, but I got 'B' using an E6-B4 whizz wheel. ( I didn't peek at the other responses before hand...)
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paddywak
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PostPosted: Mon Mar 12, 2012 1:27 pm    Post subject: Reply with quote

Well done for not cheating Pogue...

Heres another for you all, I post the answer later!

Given true altitude is 9000ft

OAT is -32C

CAS is 200kt

What is your TAS, using my CR_P 5 I arrived at 217kt TAS

Anyone care to agree/ disagree ?
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paddywak
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PostPosted: Mon Mar 12, 2012 8:17 pm    Post subject: Reply with quote

The choice of answers for the above question are as follows:

A 215KT

B 210KT

C 200KT

D 220KT
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Pogue
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PostPosted: Tue Mar 13, 2012 2:49 am    Post subject: Reply with quote

I also got 217kt. I would choose 'A' given the choices...
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paddywak
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PostPosted: Tue Mar 13, 2012 7:48 am    Post subject: Reply with quote

I also chose A, but they wanted D 220 kts,

Confused
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Pogue
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PostPosted: Tue Mar 13, 2012 1:15 pm    Post subject: Reply with quote

It figures they would round up... Smile
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lancsman
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PostPosted: Thu Mar 15, 2012 11:38 am    Post subject: Reply with quote

Using the CRP 1 I got 217 ish also (air speed window to small to get accurate reading)
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