CRP-1 Computer

[Genghis the Engineer]

I don't often use it when airborne, certainly - but I've used the Dalton Computer regularly for flight planning on the ground.

G

[mikehallam]

CRP's main function is pre-flight planning, with a chart. Of course any computing aid or even pencil & paper will do. That's why it lives in my bag.
i.e. Used before, without a care, you fly off in the general direction of 'x'.

As per se it's unknown how good the applicant's trigonometry is, the CRP test presumably demonstrates that one understands the basic 'rules' and thus better knows how to visualise the effects of wind, on drift & velocity.

[Rather than wholly believing a digital read out from some random piece of kit the P1 has decided to use.]

mikehallam.

[BackPacker]

I think i will try to master this device

Don't try to master the device. Try to master the theory behind it. Start with constructing a wind triangle on the chart itself. I learned how to do that for a nautical exam (using current and drift instead of wind, but the idea is the same) and it's really, really simple.

Then you realise that, with the typical speeds of a light aircraft, your chart is often simply not big enough to construct a 1-hour wind triangle, and that working in smaller increments, say 30 or 15 minutes gets too confusing. So you make the leap to using the wind side of the CRP-1. Which is really nothing more than a one-hour wind triangle but in a smaller and more convenient package. And slightly more accurate too.

As far as the circular sliderule side is concerned, think of it as a straightforward calculator that only does multiplications and divisions. Start with (I'm not kidding) multiplying 2 and 3 together on the sliderule. Try to understand why the answer is 6 according to the sliderule, and do a few other of these very, very basic calculations. Then do divisions.

Then setup the slide rule according to the booklet for doing, say, a fuel weight calculation. You will find that once you've got the scale set up properly, one of the main indicators (opposite of the "1" usually) is simply pointing to the specific gravity of the fuel you're using (in whatever units you choose to use). Same for time/speed/distance calculations. You are simply setting it up so that the "1" (or the "60" for 60 minutes in an hour) is against your multiplier (ground speed).

Once you've mastered the basics, using the CRP-1 is easy and probably faster than using an electronic calculator. Plus, it will give you a mental check on whether the answers are more or less correct.

All the intermediate electronic stuff, like electronic flight computers, home-grown spreadsheets and such, are not really useful as far as I'm concerned. In fact, to a large extend I consider them GIGO systems: Garbage In, Garbage Out. It's too easy to input a wrong value, but use the output as gospel. And fly in a completely opposite direction without knowing or understanding why.

If you want to get rid of the CRP-1, make sure you get rid of it all the way. And that means to get either a PC package like SkyAngel, PocketFMS or JeppView where you simply click your whole route together with your mouse and then upload it onto your GPS/iPhone/whatever, or a proper aviation GPS which essentially does the same thing. You then enter the upper wind, airspeed, fuel flow and a few other values, and the device calculates the whole plog for you. The mental check of the CRP-1 is now replaced with the very simple fact that the magenta line runs from your origin to your destination.

[biffo28]

Thanks Backpacker.

You advice on "get rid of it all the way" was very timely. Posed the CRP-1 question to my instructor today and he showed me SkyDemon - I am now sold on that type of software!