CRP5 Questions
 

- Working out true altitude is not a problem, and more useful I think- but this has me confused.....any help would be appreciated.
(You are given pressure alt. or true alt. a QNH and SAT)

CRP5 IS SHORT FOR CRAP 5. JUST DONE THE JAA EXAMS MYSELF ANSWERS ARE NOT VERY ACCURATE WHEN USING THE '5' SO WE WERE TOLD TO JUST TO USE ISA DEVIATION MULTIPLYED BY 120.
FOR TRUE ALT CALCS TRY USING ISA DEVIATION MULTIPLY BY 4 {CONSTANT) THEN MULTIPLY BY HEIGHT IN THOUSANDS.
E.G -5 MULTIPLY BY 4 MULTIPLY BY 12(12000)
GIVES A MUCH MORE ACCURATE ANSWER AND ALL OUR CHAPS ARE PASSING NAV SO GIVE IT A GO.

CRP5
 

if anyone has a secondhand(in good nick) crp5 computer that they would like to sell at a good price, please email me...
cheers

Ummm, the bosses here don't like these kind of posts unfortunately.

But anyway, I've sent you an e-mail regarding this :D

Have fun training.

CRP5 What the *!*! is all that about
 

Help me out guys/gals

This is my first post. I am a PPL student. 30 odd hours, just really embarking upon Navigation.

Did your instructors really explain the Nav computer to you?? Mine has not, and frankly I am finding it highly confusing!

Does anyone have any hints and tips to get me on the right track? How did you become accomplished with your CRP5?

Thanks

h'mm i must admit i didn't completely understand the beast until i met gen nav in the ATPL's. And worked my way through the monkey see, monkey do chapters in the oxford notes

Which bit do you have problems with?

Is it the wind triangles or the slide rule bit on the other side?

MJ

No, my instructors didn't go out of their way to explain how to use the nav computer. But I found it relatively straight forwards just by following the instructions in the booklet that came with it. The AFE/J. Pratt PPL syllabus books have further instructions on the basics in them.

The main thing seems to be practise. The more you use it, the better you get at using it. The other thing that still takes me a while is doing the rough calculations that give you an idea of the scale of the answer that you are expecting.

I guess it seems anachronistic in this day of 'real' <img src="wink.gif" border="0"> computers to have to use a ciruclar slide rule, but as others will point out, the batteries can never fail in a CRP-5. But on the other hand, a real computer will tell you the answer without having to pre-calculate a rough answer!

I assume you are having trouble with the slide rule bit and not the wind calcultions. If you are having trouble with the wind calculations, make sure you understand the theory behind what you are trying to acheive and then just practise, practise, practise.

[ 07 January 2002: Message edited by: tacpot ]</p>

[quote]...a real computer will tell you the answer without having to pre-calculate a rough answer! <hr></blockquote>

Not true! Electronic computing devices are not infallible. Apart from failures of the device there is also the 'garbage in - garbage out' problem.

Unless you have some idea of what the answer should be, how will you know when the electronic brain gets it wrong? And it will get it wrong.

As for using a circular slide rule, only practice will enable the user to become adept. I find some problems can be solved quicker using a whiz wheel than a calculator.

If one type of whiz wheel is awkward, try using a different type eg from the 'slide' type to a 'CR' circular type. The CR5 from Jeppessen is my favourite.

[ 08 January 2002: Message edited by: Tinstaafl ]</p>

Backon

If you have any specific queries feel free to email me. It is hard to teach the whole thing remotely by internet! I am a ground instructor, formerly of General Nav for the now dormant SFT. Alternatively if you're near Bournemouth anytime soon I am happy to teach you the rapid and accurate use of this wonderful and powerful calculating device, in exchange for a couple of pints.

And Tacpot, if you're well-taught then you should have a rough answer in your head already! :)

I was taught how to use the !!!!ty-Five by Mr. Send Clowns, and confirm that it ayn't hard to use once you've been shown how properly.

Hot Tip alluded to already: take an educated guess as to the answer BEFORE you pick up yer CRP-5, that way you'll know immediately if final answer you get is bollocks or not.

[ 08 January 2002: Message edited by: Blackshirt ]</p>

I seem to remember that reading the Trevor Thom book on Navigation or Flight Planning, I forget which, was what finally got me to understand it.

I'd dig the books out to find out exactly which book it was (and it wasnn't some other book completely!) but my bookshelf is half way across the world at the moment, so apologies if I'm wrong and there's nothing helpful in Thom!

FFF
---------

Backontrack,

Basically, there are 4 types of operation that the CRP5 does for you.

1. Multiplication and Division and Conversions, just like any slide rule. I agree, for these, you are probably better off with an electronic calculator.

2. Distance, Speed and Time (and fuel-flow calculations). You can do these with a calculator, but it's actually quicker with a CRP5, once you get good at it. With a question like "You are doing 220 knots groundspeed, so how long will it take you to cover 57 nautical miles?", if you use a calculator, you get the answer in hours. You then need to multiply it by 60. By the time you've done that, you could have already had the answer on the CRP5, in terms of minutes, which is what you want, not hours. On the other hand, if the question is "Your groundspeed is 320 knots, so how far will you travel in 13 minutes?", then you need to divide, not multiply, by 60. With a calculator, decisions as to which way round to do the calculation, and slight loss of speed. No such problem with the CRP5. With that big black triangle on the inner scale, you work in base 60. It gives you the answer in the form you need it.

3 TAS and Altitude Calculations. To calculate these by numerical methods on an electronic calculator requires specialist formulae, which are too complicated for everyday use - especially TAS from FL and temp, and Compressibility correction. The CRP5 solves them simply and accurately.

4 Wind Calculations - the relationship between Heading, Track, Drift, TAS, and Groundspeed. These are vector problems and would be too complicated on a normal programmable scientific calculator. You have been able to get specialist aviation calculators with the formulae already programmed for years, but these have never really caught on because the presentation on the CRP5 wind face, as well as solving the numerical problem, gives you an instant intuitive picture as to whether the wind is giving you mainly head/tailwind component or mainly crosswind, and a visual picture of whether it's head or tail and which direction the drift is in.

Three other observations:

Firstly, if your instructor hasn't explained it to you, he's not doing his job properly. Ask him. You may find he doesn't know it himself.

Secondly, the little book that comes with the CRP5 is excellent! You can use it to teach yourself very easily, if you want to.

Finally, the Oxford/Pooley CRP5 Computer Based Training (CBT) CDROM will be available in February. You can get it from Pooley's. It is so clear in its explanation. In the meantime, if you want to, you can get the CRP1 CBT CDROM. It's pretty similar to the CRP5, but without the same number of facilities.

All the best,

Paul

[ 08 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]

[ 08 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]

[ 08 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]</p>

I was under the impression we are not allowed to use calculators in the JAR Eaxma (PPL/ATPL)

Is this correct???

My instructor explained a little bit, but i got most of my info from the handbook that you get with it and also from the Jeremy Pratt Nav book!!

You can take your CRP-5 or simillar into any exam in any subject. You can also take a non programmable calculator too.

Only way to master the whizz wheel is to use it every day. U have too be damn fast in the atpl nav exam cos time is tight.

AS paul said the wee book is escellent

Well that just rips it!!!!! <img src="mad.gif" border="0"> <img src="mad.gif" border="0"> <img src="mad.gif" border="0">


My flying school told me i wasnt allowed a calculator for the nav exam!! I had to do all my working out on my wizz wheel!

Still passed though!

:) <img src="wink.gif" border="0"> <img src="cool.gif" border="0"> :)

The Trevor Thom Navigation book explains the CRP in great detail and is very understandable.
Also as Paul says, the little book which comes with the CRP-5 is also worth working through.
Also as previously stated in another post the Oxford General Nav ATPL notes go through the CRP-5 in great detail but its probably overkill to buy these if you are 30 hours into PPL.
Good luck

Paul may correct me if I'm wrong, but no electronic calculator is permitted in any of the PPL exams. The CAA has always been concerned by the slack control of exam sittings shown by some small flying schools/clubs, so maybe that is why some have been allowed. Non-programmable electronic calculators (not electronic flight computers!) are however permitted in all CPL/ATPL exams.

Thanks to everyone for their replies. It helps knowing your no the only ones struggling sometinmes.

I shall attack the Nav book and give it another go.......just hit a brick wall I think.

cheers

Backontrack,

Some Instructors teach the "wind up" method of using the whizzwheel and some teach the "wind down" method; if you intend to progress to CPL/ATPL, start using the appropriate method from the outset. I was taught one for the PPL and had great difficulty getting to grips with the other for the ATPLs.

[ 08 January 2002: Message edited by: Tee ]</p>

Tee,

Couldn't agree more!!!!!!!

'Wind up' is suitable only for PPLs, because they won't have to wind find or work out track from heading. But if you're going to be a professional you must use 'wind down'. It's the only way that's compatible with 'heading from track', 'track from heading', and 'wind-finding'. PPLs only have to do the first. However, if you want to pass these pesky JAA ATPL exams you have to be able to do all three. You have to do it 'wind down'.

Sorry about all the bold face. I don't shout in my lessons - well, not often, anyway. But the point is important.

All the best,

Paul

[ 08 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]</p>

Or use a CR circular type & never be bothered by the 'wind up' or 'wind down' carry on... <img src="smile.gif" border="0">

Yeah, yeah. I admit I'm biased. But in fairness I did Oz PPL & CPL all on a slide type (calculators only allowed in the CPL Performance & Operation subject), then Oz IR, Oz/USA/UK ATPLs on a Jeppessen CR5. In 10 years instructing I taught with both types & my vote is definitely to the CR.

NB. I still have & will keep the Kane slide type. Accurate & durable - if you want to put up with the bulk of a slide & the weight of all its thick aluminium!

The circular ones, aka "chick magnets", are designed for males to be prominantly placed in the top left hand pocket of your pilot shirt, to subtly let the female world know "I Am A Pilot"(in case they thought the epaulettes meant you were a prison officer or bus driver)

I had heard a rumour that these could also be used for navigation calculations in an emergency.

IMHO When it comes to accurate nav calculations, you can't beat the CRP-5. Does anyone know where I can get spare parts for one in Australia as mine is falling to bits after 14 years.

Wind dot down...put your track on the top...draw vertical line through wind dot...put grommit over TAS...turn line until it parallels a drift line...heading is on the top, and g/s under the dot.

BTW Tinny, candidates can take a non-programmable electronic calculator into the Aus PPL cyberexam.

I'm not entirely sure what is meant by the terms "wind up" and "wind down" but I presume it refers to the orientation of the wind vector on the prayer wheel's vector grid as the problem is solved by the pilot.

Do keep in mind that the little pocket Jepp style calculator and the traditional EB6 style use different triangles for the vector resolution and that has a material outcome for the different manner in which each is used.

Unless someone has come up with yet another implementation of the vector solution (and I admit to not having kept pace with the calculator marketplace in recent years), I am only aware of three; the two common ones mentioned above and an interesting Aristo calculator which I used briefly many years ago.

I am totally perplexed by the reference to the PPL doing it differently to the CPL/ATPL pilot. Either it is done correctly, or it is done incorrectly. I look forward to being enlightened on this one ....

And, Backontrack, do be very aware that the great majority of people have a very, very limited knowledge of the details which go into prayer wheel design ... it all tends to stop at monkey see, monkey do. I can recall the odd ground/flying school instructors telling me some of the most imaginatively incorrect ways in which to use the gadget ....

[ 09 January 2002: Message edited by: john_tullamarine ]</p>

Wind up and down are both mathematically correct methods, achieving the same result. Wind up is initially slightly simpler, but in truth even given the errors some students initially make wind down is the best way. The errors are small enough for PPL purposes, and I have had students at ATPL who had great trouble converting, and kept making mistakes on the wind-down method.

Hi CFI,

Yes, I know calculators are allowed now. Once upon a time in the dim, dark mists of time they weren't...

Send Clowns,

Your response is not particularly useful.

A quick net search has not found me any references to the "wind up" and "wind down" techniques.

Could I trouble someone to give me, preferably, net references, or else text references so that I can familiarise myself with what the conversation specifics are about ?

[ 10 January 2002: Message edited by: john_tullamarine ]</p>

Dear Paul,

Please correct me if I am wrong but I have always used the "Wind up" method. I do consider myself as professional as my fellow pilots. I have passed Navigation exams in India, UK and in USA and had no problems what so ever.
I did my NAVs with Bristol and I was also told that I will not be able to do all the calculations if I use wind up method. I couldnt get my head around wind low method so I used wind up and I had no problem and got the results every single time.
I think it all depends on which way you were taught and how comfortable you feel using it.

<img src="smile.gif" border="0"> Jatin

[ 10 January 2002: Message edited by: DesiPilot ]</p>

To John Tullamarine:

Let me explain 'wind up' by use of an example. You are in a PA28, TAS = 100 knots. You want to fly a track of 072 and the wind is 315/20.

OK, start off in the usual way, by putting the wind on. Bring 315 on the inner wheel up against the 12 o'clock position, ie, against the heading index. But instead of plotting your 20 knots downwards, ie, in the 6 o'clock direction, plot it upwards, towards 12 o'clock.

Now rotate the desired track, 072, to the 12 o'clock position. Move the slide so that the wind mark you have made appears against 100 knots.

This tells you immediately, with no juggling to balance the drift, that the required heading is 10 degrees left of the track, ie, you need to fly 062. Your groundspeed will be the figure under the centre mark, ie, 108 knots.

Everything is the 'wrong' way round if you are used to the normal way of operating. The heading marker is indicating your track and the wind point is on the TAS, with the groundspeed under the centre dot. But it does have the advantage of being a one-shot operation. No fiddling to adjust the drift.

Many flying schools , especially in the USA, teach it this way to their PPL students, who find balancing the drift too difficult. If all you are ever going to do is, given the desired track, find heading to fly, it is easier. But if you are going to do either of the other operations, it gets extremely confusing.

I don't teach it, and I don't recommend it. But you are entitled to a decent explanation. As for the rest of you out there, don't use it if you want to become an ATPL.

To Desipilot:

Do whatever works for you, as long as you get the right results. I think you're past the student stage by now, anyway. But if, as a student, you use a non-standard method after being taught the correct one, don't expect the instructor to bust a gut in helping you out if you encounter difficulties with it.

All the best,

Paul

JT, I can't follow the method either, but going through the method described and Tinstaffl's comments I think it's because I've always used the circular whiz wheel (as described by CFI as the "look at me I'm a pilot" model :) ), as opposed to the one I've seen in the Trevor Thom books. Is that the same one you use?

Can someone confirm that this is the case?

Paul,

Thanks for the clarification...

I found a picture of the CRP5 on a web site and it appears to be a fairly stock standard sort of E6B/Dalton ? Am I correct in that assessment ? If not, I would appreciate a 5 second heads up on the differences.

My initial confusion related to the "wind up/down" terminology which I hadn't come across before and the suggestion that one could use the calculator in more than one way to solve the vector problem graphically.

What then confused me greatly was the suggestion by another poster that the two methods are mathematically equivalent, a claim which appears to be arrant nonsense.

IF (and I emphasise IF) the gadget is a simple E6B then it would appear to me that to use "wind up" is graphically flawed (ie trignometrically incorrect) although, as the consequent error is negligible for small drift angles, the answer is acceptable for practical purposes. Even for largish drift angles the errors are not so great that they would cause a major problem in flight.

But this is hardly justification for using a flawed method which is intellectually confusing, especially without making it clear to the student that this is the case. Add to this the problem with pilots often swapping to the little Jepp wheels when they get onto faster equipment and the opportunity for needless confusion becomes a worry.

Surely a basic tenet of sound instruction is neither to teach nor permit the student to apply incorrect techniques, whether in the classroom or in the aircraft, useful simplifications and shortcuts notwithstanding. The extra minute or two necessary to ensure that the student understood what he/she is doing with regard to the vector solution would far outweigh the very questionable gains to be had using a flawed technique which then has to be unlearned later on.

Quite some years ago I taught CPL/ATPL classroom theory for around 15 years or so and NOT ONCE out of quite a few hundred pilots can I recall a student having more than trivial difficulty learning and doing the exercise the graphically correct way.

Can someone tell me .....

(a) have I missed some vital underlying lemma here ?

(b) what purposeful advantage is there in using a flawed technique when the correct approach only takes a moment or two longer, makes intellectual sense, and doesn't have to be unlearned next month because it is wrong and doesn't work to sufficient accuracy ?

Perhaps I have yet another piece of quaint folklore to add to my list of innovative ways of using the prayer wheel.

Foyl, I use either style of wheel according to whichever I pick up in my little hand first to solve the immediate problem. It doesn't matter.. if the same data is built into the wheel's design then either will give the same answer if used correctly. Many of the E6B machines don't have any compressibility data so, in that case and for high speed aircraft, the little Jepps are more useful.

Foyl,

Even if you use the circular sort, you can still use them either 'wind-up- or -wind-down'. Try my example the normal way, then reverse the wind direction to 135, and you will get your triangle of velocities without any drift-juggling. Not that I recommend it - just to show that the type without the slide makes no difference to the argument.

John Tullamarine,

Yes, the CRP5 is like a Dalton or Jeppesen EB6. It has a rectangular slide, with a high-speed and low-speed side. The slide rule has a few more facilities (compressiblity slide-rule, not a table, and calculation of True Altitude or Density Altitude from Pressure Altitude and Temp), but the Wind Face works on exactly the same principle.

Send Clowns is perfectly correct, the 2 methods are mathematically equivalent. You are not changing the geometry of the triangle of velocities by plotting upwind. You are simply displacing the axis in which you plot it on the face of the computer. The triangles are identical.

As for what is the 'correct' way to do it, I think it's horses for courses. I've already said I don't teach 'wind-up' and don't encourage its use. But the GA situation in the USA is virtually unique. Many people who have lots of surplus wealth want a relaxing week-end hobby. If the flying clubs make it all too difficult, the same people will go jet-skiing, powerboat racing or snow-boarding instead. These guys are not going to become ATPLs. Provided that safety is not compromised, it's good that they enjoy flying. Lighten up a little.

All the best,

Paul

[ 11 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]

[ 11 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]

[ 11 January 2002: Message edited by: Paul Hickley, Gen Nav Spec, Oxford ]</p>

Apologies J_T, I was merely trying to reassure you that both methods give the correct result for problems of heading and groundspeed.

It is very hard to teach CRP-5 in text, I would always recommend you get someone to teach face to face, and check what you are doing. If your own instructor is unable and unwilling, and none of your other club instructors will help, then you might do better at another club! It is part of an instructor's job to teach these things, and it is important, especially if you plan ever to become a commercial pilot, that you can use this instrument quickly and accurately.

You both seem very sure of your ground.. perhaps I had best go away and do some trig on the matter before I consider my position ?

Several cups of coffee and sheets of paper later ....

Ooohhhh dear ...

Perhaps the ports which accompanied the coffee consumption had something to do with it but now it is apparent that I was guilty of contemplating a subject over a cup of coffee without drawing a sketch and doing some sums ... how often do we all exhort our students to "draw a piccy" ?

As a result, I permitted the engagement of my mouth (keyboard, if you will) whilst the brain, quite clearly, was doing something else. (Quietly goes away and tears up degree due to obvious and gross incompetence ...).


Please do let me edit/correct my previous post ...


The statement that the wind up and wind down methods for the E6B style of instrument are identical is perfectly correct and, in fact, it is the one and the same vector triangle ONLY which is being "drawn" over the slide fanlines regardless of which method is used .. not even a matter of different triangles at all.

This is quite easily seen by drawing the vector picture on paper using correct bearings and scale on a fan and radii background and then considering what is being done with the instrument using first one, then the alternative methods. Either way .. one triangle ... so the same answer ... no error.

For me, though, it is very easily confusing if one is concentrating on the instrument (which is, after all, the window through which we see part of the complete vector triangle).

For those who are similarly prone to confusion, consider that you are also "moving" the entire instrument (as a window) over the larger background grid toward the track vector. Not at all easy to sort out in the mind without a sketch to aid orientation.

I haven't looked at the solution on the little Jepp calculator so I offer no comment in respect of that instrument. When next I have one in hand and a few minutes to spare I will contemplate the problem once more.


My humblest and most obsequious apologies, both to Paul Hickley and Send Clowns ...


The main thrust of my concern as an instructor still stands. I have no problem with using any method that produces a good answer in practice. However, for the instruction side of things, to introduce needless intellectual complexity when a student needs just the opposite .. appears to me to be counterproductive.

The student is best placed to understand what he/she is doing if he/she can see the relationship beween the instrument actions and the base vector solution and this is one reason why it is easier for most people to follow the rationale behind the E6B rather than the little Jepp although I hasten to add that both are fine instruments.

It is for this reason that I would avoid the use of a method ("wind up" on the E6B) which

(a) is very confusing, intellectually, when viewed against the basic solution.

(b) really offers a negligible increase in ease of instrument use, although that is, admittedly, just my opinion. I reiterate my earlier statement that I have never had a student who had other than the usual trivial difficulties in coming to grips with the traditional method of using the instrument. If there is an advantage in the alternative method, then I suspect that it is more imagined than real.

It would appear that Paul and I agree on this general point of view.

Rather than folklore, I have learnt something new ... and that can only be a good thing ...

Have I lightened up sufficiently for you, Paul ?

best regards ...

[ 12 January 2002: Message edited by: john_tullamarine ]</p>

The wind correction rotation needed on the CRP type computer often confused me in the early days. I eventually found that a double check of my result was useful. That check was, am I leaning (heading) into wind,relative to intended track.

Paul, and others,

Please answer this one for me:

Is there a requirement for a slide/circular computer that can calculate compressibility - for the JAA ATPL exams ?

In other words, the "Pooleys CRP-1", is it sufficient for the ATPL exams, knowing it can handle neither high speeds nor compressibility ?

Also, a reference to where it can be found as to what calculators are allowed to the exams, would be welcome. (Electronic, non-programmamble OK ?)

TD

By the way, when I was reading this thread and saw "wind up" - I couldn't understand why you got so wound up about wind up. I was reading "wind up" as in overreacting to something !

Thanks JT & PH, woke up when I read it through properly - with brain engaged this time... <img src="rolleyes.gif" border="0"> :)

I can't believe this - a flaming suitcase to the left of the thread showing hot interest in the topic - on the CRP5!!

To The Drop:

The JAA ATPL Gen Nav, Flight Planning and Instruments exams all require you to be able to calculate TAS from FL and OAT for cases above 300 knots. If your flight computor doesn't have a compressibility slide-rule or table, then you are allowed to take a single-sheet compressibility correction table in with you to the exam. If an Oxford student already has a flight computer without compressibility and doesn't want to buy a CRP5 when he starts the course, we issue him with the compressibility correction table.

You are also required to solve triangle of velocity problems at typical flight speeds of modern jet airliners, ie, TAS of about 420 to 490 knots. If you haven't got a high-speed slide, it will slow you up. You can solve the problem by halving the TAS and the Windspeed, solving for that case, and doubling the groundspeed you find at the end of the calculation. The drift is correct. I really wouldn't recommend it, though. Speed is everything, especially in the Gen Nav exam - almost everyone finds it tight for time.

If you're going to do ATPL, you need a proper flight computer to give yourself a fighting chance. Take the view that it's a long-term investment - if you get your licence, you will probably be flying high-speed aircraft. And if you look after it properly, it will last you a lifetime.

As for electronic calculators, you can use any non-programmable sort. Get a reasonable scientific one - you must have sines, cosines, tangent, logs, and powers. You can't use specialist aviation electronic calculators, such as the Jeppesen Electronic E6B.

I'll see if I can find the reference quoting the calculator regulations at work on Monday. I haven't got it at home. But what I've told you above is correct.

All the best,

Paul

Thank you, Paul, I will see if I can get that compressibility sheet. The wind side is OK, it has the fast side as well ...

TD