Navigation Woes...
 

Hi all

Looking for advice on the nav exam and studying for it. I have both the Pratt and Thom series of books and seem to be able to understand the majority of stuff therein. My problems lie within the mathematics and use of the whizz wheel.

The regular operations of addition etc I can manage no problem and if I do the gross error checking on conversions etc they usually turn out close - if not spot on - to the worked examples or questions from the confuser.

My problem lies with the wind calcs. I have been using the wind-down method as I was (or hopefully still) planning on going on to the ATPL/CPL afterwards and noted from previous threads that this was the preferred method. I am also using the CRP-5 to avoid the need to upgrade for later studies!

If I draw the information that is given out on paper to "validate" my thoughts I get close to the correct answers but fail to understand the final jiggle to get the G/S & Hdg..

Any information advice etc is appreciated.

I have been considering the purchase of another book or two that I have seen in the Transair catalog (cannot for the life of me remember their titles) that take you through a complete flight and show alternative methods of doing the calcs - would they help clear the mists?? (Met is another story!!)

Cheers

Dave

Dave,

The "wind down" method tells you what drift you will get if you fly a particular heading. You need to "jiggle" to get the wind for the desired track.

Let's take an example. (N.b. I don't have a CRP5 to hand, so I'll make up numbers which are approximate - you will probably get different numbers if you actually work through my example!)

In our example, the wind is 300@20, you intend to track 270 at 90kt. You use the "wind down" method, and find that, if you fly heading 270, you will have 14 degrees of drift, suggesting a heading of 284.

Now, the jiggle: repeat the process, but this time, instead of 270, work out the drift for heading 284. You find that the drift is now 12 degrees. (The reason for the reduction is because you've turned into wind slightly, so there is slightly less crosswind than there was on the heading of 270.)

Ok, so if the drift is now 12 degrees, we need to jiggle again, and try a heading of 282. On that heading, we still have a drift of 12 degrees, which confirms that 282 is indeed the correct heading.

Hope that clears up the jiggle.

FFF
-----------------

Never heard of the Wind-Down method. I just read track off the GPS and alter my heading until actual track = desired course over ground ;) For flight planning I use Flight Star ;)

englishal
only one slight flaw in your cunning plan, you cant use that method in the exam!

RudeNot2: FFF has the answer

Ken

Doh! Oh well, luckily I don't need to!

Eek
 

What are you going to do if your GPS fails ?

Wind down cd
 

Get the Nav and CRP-1 OAT CD ROM.

I Know you're using the CRP-5 but the cd rom really is excellent for visually and verbally explaining how to carry out all necessary calcs on your flight computer.

Don't buy any more books, I'm confident that this'll do the trick. :ok:

Good luck

Nadders

I will 2nd what nadders said. I had the same problem, once I could follow it through, it was a piece of cake,

Not used it since my NAV exam, tend to use mental arithmatic, and work it out as and when I need to

But gonna have to start using it for my IMC exam

Start with your vision of the triangle of vectors on paper. Point A - the aeroplane, is at the bottom (usually off the bottom), of the sliding scale (in the middle, where the zero speed would be).

The centre of the rotating circle can be either point B (the end of your TAS and Heading) or point C (the end of your track and groundspeed).

You choose which of these it wil be. When you draw the wind vector Up you are making the centre point C, when you draw the wind vector Down, you are making the circle centre point B.

The usual situation is you know your track (orientation line A-C) and your TAS (length vector A-B), but you don't know the length of A-C and you don't know the orientation of A-B.

Using the Wind Up method means your circle centre is point C of the vector triangle. The END of the wind vector (where the wind blows from) is point B of your vector triangle . You know the track you want to fly, so set it on the outer ring - the wind vector moves about, left or right. You know your TAS, so slide the speed scale up/down until your TAS is under the point B (start of the wind vector). You now have your vector triangle - point A (at the bottom of the scale), point B (the end of the TAS vector) and point C (the circle centre) being the Groundspeed vector. Now just read off your drift on the left/right degrees of the sliding scale, and your groundspeed under the centre circle. No fiddling required.

The fiddling comes with the Wind Down method because you are placing the end of your TAS vector in the centre (point B), from which you have to find out what drift will give you your desired track (point C). As you rotate the circle back and forwards, the drift changes, and so does the eventual track. You are trying to find the correct amount of drift that will produce the track you want to fly. That's what the fiddling is about - matching the drift on the scale, so that it will give the desired track from the selected heading. Finally, once the amount of drift gives the desired track, you can read your ground speed from under the end of the wind vector.

To visualise it all draw a (large-ish) vector diagram (random, TAS, random wind, random track), using the speed scale of the CRP your sepeed, then put you CRP over it - it then becomes more evident.

GB

Look at the stanby battery powered GPS that has been on charge from the mains power.

I feel another heated GPS debate coming on..... :ok:

Show me a pilot who can hand fly and operate the CRaP 5 and I will show you a man with more arms than an octopus.

Thanks god for the ASA flight computer!!

I like these arguments. If you are nicely trimmed out you should be able to start whizz wheeling. Personaly I use the ASA CX-2 when in the air. On the ground I use the whizz wheel, mostly because I am working on my ATPL's and I don't want to forget how to use it.

I prefer good ole nav for vfr, heading distance time and visual references. I do use a GPS in the PA32 sometimes, usualy in crap weather. If not VOR's DME's and NDB's.

No genuine pilot can pretend to be able to use the circular slide rule in flight, unless he has an autopilot.

And if he has an autopilot, he obviously hasn't had a total electrical failure, in which case why not use the alternatives to GPS e.g. VOR/DME/ADF or even (dare I say it) call up ATC and ask for vectors or whatever. Of course anybody flying somewhere for real will just refer to the 2nd GPS (which will be running anyway) and get on with the flight.

This stupid device exists for the same reason as you need to wear a certain kind of pullover when playing cricket, or wear a leather apron in a masonic lodge, or the soldiers guarding Buckingham Palace wear those silly high furry hats, etc - it's a great olde English (note: not "British") tradition which usefully separates the men from the sheep.

I am rather suprised it is mandatory at the JAA ATPL level, since no airline pilot young enough to be currently serving will have ever used one for real. In the commercial air transport world, this stuff went out with the sextant. I hope that nobody flying jets for real actually believes otherwise; I would be seriously concerned for my safety if they did.

The FAA doesn't require it in the PPL, CPL, ATPL and guess what, all these are ICAO compliant. To top this insult to our regulators, most of the world flies under FAA licenses!! I just hope the Daily Mail never finds out.

To answer the original poster's Q I would suggest learning it just enough to pass the exams, and sell it on Ebay immediately afterwards.

Could not agree more.

However I would not sell it or stop using it until you have your ATPL's out of the way and have a job on a commercial flight deck.

You might like to look at this thread.
http://www.pprune.org/forums/showthread.php?t=266801

:rolleyes:

The last time you will use a Crap wheel as a PPL is the PPL exams. The last time you will ever use it as a wannabee ATPL is the ATPL exams. You will never use it in reasl life. Airline pilots don't even do there own flight planninbg it is done by ground ops. You just get in, press the same buttons and fly the same old routes, waiting to spring into action and do the good stuff if the !!!! hits the fan.

The CRP computer is a piece of history that should be dumped in the compost of aviation history. I don't believe anyone can safely operate a GA aircraft auto pilot or not and operate the CRP. It is a device that takes a lot of heads in time. Time that you should be looking out the window and carrying out see and avoid. The ASA electronic verision is marginally faster to operate but the same comments still apply. This is the reason why we have so many rules of thumb. Safety first.

Thanks for all of the replies folks.. I will dig out the "computer" this weekend and start going through some further examples.

IO540 and Bose et al.
Well I must be an exception to the rule. I am ATPL and I have not one grey hair - I may even be young enough to be your offspring. I still carry the wheel and use it. A damned fine instrument it is too. Yes, there are more modern alternatives that are perfectly adequate, but so is the wheel. You pays your money and takes your choice.

In fact I am not an exception to the rule - all my colleagues carry a wheel and use them.

I am curious droopy, tell me what exactly you and your colleagues do with the whizz wheel? Solve Sudoku problems with it?

Not one airline pilot I know uses a whizz wheel anymore so you have really piqued my interest as to what you can possibly do with one!!!

I don't need a Wizz wheel - If I need to calculate drift, I simply take Sin of relative wind to give me a cross and headwind component then add that to my course to give me GS and course to steer...:) Of course the Log Tables I use are JAR-FCL approved log tables.

If GPS 1 fails, I use GPS2. If that fails I use VORs. If there are no VORs I use NDBs. If there are no NDBs I may use Atlantic 252 or some other station in Newfoundland.... :eek::}

Yes I am ATPL(H). Two crew, IFR, scheduled type flying in a stabilised but non autopilot aircraft. We do have a (notice the singular) GPS which is approved as a primary nav aid in certain scenarios. We do use flight planning software at base. I am not anti modern stuff and would use it by preference. But there are times (like when the network crashes at work - not uncommon) when the wheel is dragged out. Similarly, on the odd occasion the GPS does throw a wobbly we use it in flight. More commonly we use a wheel to plan subsequent flights on return legs. Yes there is a GPS sat there, but to be quite honest it is often less hassel to use the wheel and not substantially slower.
Don't write off the wheel. It is an incredibly powerful tool and alot easier to use than is made out - practice makes perfect! There are even things it can do that our GPS cannot, like work out intercepts for moving way points (ok I agree that is not terribly useful).
Gadgets are great, but it doesn't mean the old stuff doesn't work. We still often fly IFR with no HSI, no Autopilot and no second GPS and we still get home on time.

Bose,

Not that we have a chance to do Suduko puzzles, but how do you use the wheel to solve them?!!

Similarly, on the odd occasion the GPS does throw a wobbly we use it in flight. More commonly we use a wheel to plan subsequent flights on return legs. Yes there is a GPS sat there, but to be quite honest it is often less hassel to use the wheel and not substantially slower.
Don't write off the wheel. It is an incredibly powerful tool and alot easier to use than is made out - practice makes perfect! There are even things it can do that our GPS cannot, like work out intercepts for moving way points (ok I agree that is not terribly useful).
Gadgets are great, but it doesn't mean the old stuff doesn't work. We still often fly IFR with no HSI, no Autopilot and no second GPS and we still get home on time

All the above proves is that a whole as yet undiscovered world can exist in some corner of aviation.

For a start, how often does a GPS "throw a wobbly"? What sort of a GPS are you using??? Was it made in the 1980s?

IFR with no HSI (presumably meaning no slaved DI) in a helicopter??? What kind of masochistic exercise is this?

The biggest problem is that anybody who can fly a helicopter while holding a heading to an accuracy where the slide rule would deliver a more accurate solution than the simplest rule of thumb (e.g. max drift is half the crosswind, etc) is a robot.

This is simply unreal. Could be an RAF or ex RAF crew perhaps, which was never exposed to the outside world?

Perhaps the most serious comment I can make is that some things can be practiced by very high hour highly trained pilots which would be completely stupid and inapplicable to all the rest.

Why not just fly partial panel, single pilot IFR, no autopilot, at night? Then you don't need much avionics, so even less to go wrong.

All the above proves is that a whole as yet undiscovered world can exist in some corner of aviation.

Indeed.

For a start, how often does a GPS "throw a wobbly"? What sort of a GPS are you using??? Was it made in the 1980s?

It probably was. The make is Trimble, I forget which model, something like a 1201.

IFR with no HSI (presumably meaning no slaved DI) in a helicopter??? What kind of masochistic exercise is this?

Most aircraft have a nice HSI, some have a slaved DI, RMI, OBS. We don't get to choose!

The biggest problem is that anybody who can fly a helicopter while holding a heading to an accuracy where the slide rule would deliver a more accurate solution than the simplest rule of thumb (e.g. max drift is half the crosswind, etc) is a robot.

It is perfectly feasible to fly our helicopters to a degree of heading. Wheel is more accurate than rules of thumbs, but we still use our thumbs as well.
This is simply unreal. Could be an RAF or ex RAF crew perhaps, which was never exposed to the outside world?

Wash your mouth out!:) Never flown military. Ex GA.

Perhaps the most serious comment I can make is that some things can be practiced by very high hour highly trained pilots which would be completely stupid and inapplicable to all the rest.

There are many ways of skinning the aviation cat. None are wrong, some might be seen as inappropriate but at the end of the day everything from rules of thumbs, whiz wheels, GNS 430s to full FMS are valid. To critisise any one of them is folly.

Why not just fly partial panel, single pilot IFR, no autopilot, at night? Then you don't need much avionics, so even less to go wrong.

Its not about masochism (although it maybe sadistic tendencies among management) or machoism. It is about being able to keep the show running regardless of the level of kit fitted to the machine. There is a huge dumming down of aviation in professional levels due to more advanced hardware. I prefer to fly rather than push buttons.

Great posts, Droopy! :ok:

Well I am impressed that a commercial pilot is so keen to hang on to history.

You are not an airline pilot and my comments still stand, I personally do not know an airline pilot who uses a whizz wheel.

There is no doubt as you say the whizz wheel is a powerful tool, so was the slide rule and the log tables I used as a kid for math. However in this day and age electronics devices deliver much greater accuracy with less effort and far less room for error.

This has been debated so many times before!:hmm:
At the end of the day, once you have done your exams it is up to you if you use it or put it in the bin, but, until the powers that be decide otherwise, it has to be used for exams and so lets get on with help where it is needed and I would suggest that those who no longer use one leave the thread alone as they are not likely to be in practice and so not a lot of help.:p

True. But you might also struggle to find an airline pilot who does his own planning... ;)

By all accounts the reason we still have to use a piece of equipment that was used by WW2 bomber crews is the old power issue. The CAA think that the whizz wheel is more reliable as there are no batteries to run out. Fair point, but only to a point. There are that many nav aids available these days that if the battery packs up then look at using another aid. Carry a spare set of batteries. Use VOR/NDB, call ATC, the options are endless really, and the whizz wheel isn't that accurate really. It needs to be supported by mental arithmatic as well. Not too hard on the ground, but a complete pain if being banged about at 2000 feet!

However, as we know the powers that be aren't keen on change, so the whizz wheel will stay for the forseeable future I imagine.

Bose,

It is not a matter of wanting to hang onto history, its a case of having to fly a piece of aviation history :ok:

Mind you I reckon I will still fly with a wheel in the pocket even if I did fly a new fangled machine.

CG,

How accurate do you need to be? The wheel is easily accurate enough given the quality of the forecast wind, fuel gauges etc. Yes our flight planning software works out our fuel requirements to the nearest lb, but that is less than 0.1% of our hourly burn. The wheel goes to the nearest 10lbs which is easily good enough.

I think one of the main reasons that the RAF has 'Talking Baggage' in the back of it's large Helis is precisely that it is impossible to use a whizz wheel while flying a heli.
If we were doing too well on a navex, we used to get the 'overturned Landrover, x stretcher cases at grid Y, can you deal' thrown in, and I had the luxury of spreading out the map on the aircraft floor and doing all my tracks, drift calcs and Fuel/weight/range computations without being encumbered with sticks and levers.

On the negative, I had no forward view, so had to rely on a sideways view of the world and the pilot narrating what he could see, OK at 1500', but somewhat exciting at 50-100'/90 kts, going across a 1:25,000 at alarming speed shouting 'Wires' sporadically!:}

The power issue doesn't wash. Can anybody here remember the last time a calculator was unusable due to dead batteries? One can make that argument for a laptop or a PDA, most certainly, but one would not use either of those for a critical application on the ground and one would not use either of them for anything (when running on batteries, anyway) when airborne.

It's true airline pilots don't normally do their own planning. I have flown with quite a few and none of them (noting that very few of those who fly GA fly IFR GA) would be able to file an IFR flight plan that's Eurocontrol acceptable, and they haven't got a clue about IFR issues like oxygen, and where to get smart weather data via the internet. The place to look for real "on the hoof" flight planning ability is corporate and private bizjet pilots; most of them have to do everything alone. None of them use the slide rule.

I think the continued teaching of the slide rule is positively reducing safety. For a start, the large proportion of the PPL ground school (none of which is mandatory anyway) gets blown away on this subject, and could be better spent teaching more useful stuff, like how to work out a real long route across a bit of Europe.

Next, nobody is taught how it actually works. I used a straight slide rule at school since in the late 1960s (this was in Eastern Europe, not the UK) and understood how it works: adding/subtracting logs and doing the antilog gives you multiplication and division. But present day PPL students never get to understand this very simple principle. They never realise that the calculator side is just a general purpose multiplication/division function, which just happens to have marks in common places like litre/gallon conversion factors. They think it is some special purpose aviation device, which magically converts one thing to another. So when they get a duff answer because they line up the marks wrong (which is really easily done) they never realise it. I also think most of them never suss out that the wind side works out the trig for the wind triangle, and when and why iteration is required to get the right answer.

There is so much stuff which would be more usefully taught in the PPL, which would help turn out a PPL holder who can go somewhere interesting. Instead, they learn a whole load of rubbish.

Most intelligent people that walk into a flying school take one look at this quaint old nonsense, smile politely and walk straight out of the door.

Droopy - if you can fly a heli to 1 degree on say a 20nm leg, you are indeed a robot :)

Not strictly true.

The whizz will i got came with a little manual. It explained how it works and went into all the above you mentioned. It even had a little test at the end.

I would imagine hardly anyone reads that little book and waits for NAV lessons, and as you say comes to the conclusion that it is an aeronautical masterpiece.

So those that do not are thick????

Picture it, pilot has no ideas how to use a GPS and battles with the whizz wheel. Suddenly he looses instrumentation including the GPS is spamcan is equiped with. Pilot plots diversion whizz's it up and makes a safe landing.

Pilot has no ideas how to use a whizz wheel as he intelligently decided to walk away from the quaint old nonsene, but he did smile nicely. His spamcan looses all instrumentation including the GPS which he has a Phd in the operation of. He proceeds to fly of course get lost and crash due to no more fuel and the inability to read a map and use a whiz wheel.

Out of the two scenarios who is the less intelligent?

RudeNot2
 

Did you get an understandable reply to your question?

;) ;)

GB

What utter nonsense, most people are well into their PPLs before they come across the confuser and I would not think much of people who would let a simple plastic device stop them from completing. If you like the Nav computer or not, explained properly it is NOT that hard to learn and you DO have to for your licence.
(n.b. for the record I also think it should be phased out, but until the CAA do that I will continue to each it):p :yuk:

Actually if you read my post you would see that was exactly the point I made!!!

Intersting to read so many points of view from a large number of apparently experienced pilots here. As a very green PPL who has less than 20 hours under my belt since gaining my license I still use the whizz wheel to help me plan my nav. Touching wood here - it has never let me down and honestly I really enjoy this form of navigation.

During my training I often flew a GPS equipped aircraft but it was never allowed more than passing reference. Maybe I should have been more insistent and I wouldn't be sitting here now thinking how naive I seem to be and how little I know. I appear to have a mental block as regards getting started with a GPS. How did others who only have the "luxury" of club hire get to learn how to use one? Car based GPS easy - are a/c based system really as easy?

I am only now gaining in confidence in the use of VOR, presumably it's a case of familiarity and practice makes perfect.

I would really welcome a balanced view point on this. Am I really the only one who is having a crisis of confidence on the subject of "technology" in the cockpit?:O

Rude Not 2

I am sorry for hi jacking the post, but I hope you can see that at least a small minority of professional pilots still use the wheel and believe it is worthwhile to get to grips with.

Flyingsteve55,

As I have said before there are many ways of doing navigation and it is up to you what you decide to use. It will largely depend what sort of flying you want to do. For some, traditional navigation is a reason in its own right to fly, others want the most user friendly, low input means to get from A to B. Neither is wrong. What ever you use and whatever you choose not to use, it is well worth having some understanding of the pluses and minus's of all of them.

My advice to you is to practice the wheel and get confident with it. After all you have to use it to get your PPL. Thereafter I would recommend that you get your instructor to give you at least an hours flying using the GPS post PPL as an extra lesson. GPS's are great, but there are a large number to choose from and not all of them are very easy to use. In fact some of them are very challenging and counter intuitive. But once you get the hang of them, they can be very useful.

PS IO540 I am not a robot and agree that I couldn't hold a heading to within a degree for an extended period, but the AFCS can - all I have to do is fly to that heading, which I can do to one degree. The Stab looks after the rest. (basically a yaw hold using the compass as a datum)

That's true, there does seem to be this assumption that you can remember some secondary school maths, which I guess won't apply to everyone.

Personally I use the wheel because I was taught it for the PPL and can't be arsed either to do the sums by hand with pencil and paper or to find and learn a piece of software that will do it for me. Simply because it's not worth the effort, the wheel takes seconds per flight to do the sums, and it'll take longer than that for the computer to start up!

Droopystop

Don't worry about the 7500:rolleyes:!! This is what the forums in general - not just this one - are about.

I will look back to the thread on Sunday night with whizzy in hand and also dig out the CRP cd that I have and go over things again. I must get my finger out and get the exam sat otherwise October will be on us and I will have to sit Airlaw and HPL again!!

Thanks for the info guys, both the relevant stuff and the banter.

Not sure why a discussion of the circular slide rule should automatically lead to a discussion of GPS.

The slide rule is for ground use. A GPS is used enroute. The two are not related.

I am convinced that the slide rule should be abolished and the time put to better use. Anybody who can afford to fly can afford to buy an electronic version for the wind calcs. The CRP devices are actually very expensive for what you get. The multiplication/division side of the slide rule is (in most hands) just a disaster looking for a place to happen and a 5 quid calculator does a much better job. The pilot then has to remember a few factors like 3.78 (USG to litres) but he has to remember those anyway to do a sanity check when using the slide rule.

Couldn't agree more. There should be no restriction on using an electronic calculator for PPL navigation training as far as I'm concerned. Although personally I find the circular slide rule useful for some applications.

Do any of the latest hand-held GPS systems include a flight planning calculator? Having entered route waypoints, it wouldn't be rocket science to enter planned IAS, ALT, W/V, OAT and fuel consumption to obtain GS, heading and leg time for each leg. Then send it to a printer for your paper back-up in case the system dumps in flight.

Ideally, of course, the W/V and OAT would be available on-line....