CRP-5 Wind Side Calculations Help Please
 

Hi All,

I keep having accuracy issues when calculating headings, G/S's etc on the wind side of my CRP-5. (PPL level)
When I say accuracy issues, my dead reckoning is fine and is usually bang on. The issues I am having are when I am completing exercises in workbooks, (PPL Confuser, Trevor Thom NAV etc). Most of my calculations are approx 3 deg out, and its driving me insane.
I use a fine tip pen, and am as accurate as is humanly possible when 'lining up and marking', but only roughly 1 in 4 answers are within tolerable limits.

Has anyone else experienced the same issues, could I have an 'iffy' computer??

Cheers guys. :confused::confused::confused::confused::confused:

give us an example we can do and see what we come up with,,,, its also worth noteing that some questions do not have a right answer, just the nearest will do

also are you doing PPL wind up method or CPL wind down method? i dont know why they teach you the up first as you have to do down in CPL and why confuse stuff from the start as thats where most of us are heading anyway

There is a reason they call it the CRaP 5 LOL LOL

I had the same issue all through my ATPL groundschool.

I would suggest trying another computer. For exams, I use a Jeppesen metal computer for all wind-side calculations, and a CRP-5 for other calculations (as it allows for SG of fuel in addition to being more accurate in my opinion).

In life outside of exams, I just use the Jeppesen, and the Cr@p 5 stays at home.

Not sure how to 'balance drift', have never come across it, or maybe I am not familiar with the terminology. I will run through a quick scenario:

W/V 055/36 TAS120 TRACK085T VAR 7W

Firstly obviously, I have plotted the W/V onto the plate. It is absolutely BANG ON!!
Secondly, I spin round to a track of 085. This gives 11 deg of Stbd drift, and a G/S of 91kts.
This gives a True HDG of 074, so a Mag heading of 081.

So answer:
HDG(T) 074
HDG(M) 081
G/S 91KTS

Answer in book:
HDG(T) 077
HDG(M) 084
G/S 88KTS

So, I am 3 out on all calc's.
Do you guys get the same.......:confused::confused:

Thanks a lot for your help.

Given wind and heading, track is easy but given wind and track, you need to employ a "shuffle" method - best to get an instructor to show you this but, in your example, I made the initial drift to be 10 degrees so move the bezel back to 75 degrees. Reading off from W/V at 36kts, gave me a drift of 7 degrees. 7 degrees plus 75 = 82, not 85 so move the bezel another degree to 76 gives a drift of 7 (and a bit), shuffle again to 77 degrees, drift = 8 degrees which equals track of 085.

I think that's also what is meant by balancing the drift; you sort of have to work backwards.

Cheers

Whirls

The old "iffy computer" excuse, eh? Don't worry - we've all been there.

The Gen Nav ATPL exam is nearly one third CR(a)P 5 questions and therefore required daily practice of 30 to 40 minutes throughout the course, Strangely, the computer stopped being "iffy" towards the end of the course.

Practice, practice, practice.

I used a jeppesen computer disc for my ATPL.the smallest u can get.(cr5)
http://www.marvgolden.com/flight-com...jeppesencr.htm

I was always in the middle of 2 answers, so I had just to pick one answer.
passed navigation exam with 78%, and a 20$ computer disc...just lucky!

I dont suggest them if you do your ATPL.

'Balancing the Drift'?
 

I am currently near the end of my PPL and use a CRP-5 and get the same answers as Windsheer. I have been taught the 'Down-Wind' method and I would employ exactly the same process as Windsheer to get my results.

I had a period of thinking that I needed to 'Balance the Drift' when doing my 'Down-Wind' method calculations. But my instructor said that it was incorrect as I was confusing the 'Down-Wind' and 'Up-Wind' methods?

I stopped balancing the drift and never had any problems with accuracy (never more than 1 degree -/+) with my PPL Nav exam or getting close to the examples given in my PPL Nav study book, AFE - Jeremy Pratt.

Which method have you been taught? It sounds like the 'Down-Wind' method?

Someone with more experience than me could advise whether there tends to be any difference in answers when employing either 'Up-Wind' or 'Down-Wind' methods? But somehow I very much doubt it!

I'm not really sure whether what I have said helps you much Windsheer, but thought it was worth mentioning anyway.

Cheers.

Cheers all, and cheers 119.35.

It all helps enormously. The main thing I have picked up is there isn't a problem with my CRP, just maybe my methods - which will obviously change with experience.

The 'down or up' interests me though. I was simply shown the one method and can see that applying the other could give a different result. I will speak to the boys in black jumpers next time at the airfield. Although, any other tips will be appreciated.

Thanks again all.......:D

who use these computer disc?
never seen that in a cockpit!!!

bit of mental working out can save you tons of trouble in the exams....as in if its a bit of left hand down or right hand down. 4 possible answers in ATPLs, 3 of them could be to increase heading, ie to the right. or vica versa. a quick look at the answers before you do the q can help. same goes for if the scenaria gives you a head or tail wind in the answer. Usually knocks a few answers out before you even touch the crap5. you can be lucky enough to get 3 knocked out instantly. bang. tick the box, move one. saved yourself 5 mins! best to double check just in case though.

also...quick sketch diagram. can usually get a pretty accurate estimate of what the answer will work out to be. if your crp5 matches your estimate and the answer is one of the 4-sweet. takes no time at all and helps big time in the exams.calculations get much more accurate with practice and in the IR phase, being able to pull up a ballpark heading/groundspeed helps for the old ndb holds,ILS and NDB approaches. quick wind arrow on a plate, bobs your uncle and fannys your aunt

Actual answer to the problem:

HDG(T) 076.4º
G/S 87.5KTS

So it seems the confuser isn't perfectly correct.

Not suggesting you should attempt this method for exams but just for practical purposes:

Max Drift (MD) = (WV X 60) / TAS

= (36 x 60) / 120 (Note the convenience of 36 x 60 and 120 - quite easy to do in your head)

= 18 degrees, when applied 90 degrees off track

15 degrees off track = 1/4 of MD
30 degrees off track = 1/2 of MD
45 degrees off track = 3/4 of MD
60 degrees off track = FULL MD

Therefore, 85 degrees track against 55 degrees wind direction = 30 degrees = 1/2 MD

= 9 degrees, turning into wind = True Heading of 85 - 9 = 76 degrees

Add Magnetic Variation = 76 + 7 = 83 degrees Magnetic

Took me 30 seconds (after 4 x bottles of Magners) and I'm no genius - mind you, the numbers in the question helped.

CPL instructor used to b*ll*ck me every time I picked up the CRP - "You don't need that. Max Drift, boy, Max Drift"