What can ground based weather radar see?

[IO540]

In the JAA IR Met exam, one question asked (from memory) what can a ground based weather radar see:

A) CBs with hail
B) liquid precipitation.

The other two options were obviously implausible.

From seeing some similar QB questions I think the writer was after A) but both are absolutely equally correct IMHO.

I appealed it, for what good that might do...

Interestingly the actual exam questions in the 7 exams did not contain anywhere near as many dodgy questions as the QB does. For example I didn't see any which had outrageous options like

A) 2 nm
B) 2 miles
...

which make one wonder what the writer has been smoking :ugh:

[Genghis the Engineer]

I'd go with A, Wx-Radar should always see CB with hail, but it won't see liquid precip in every case - light drizzles unlikely to be seen with a standard weather radar. Particularly since precip that is of too low density to threaten an aircraft may well be filtered out.

Just like CPL and ATPL exams, written by idiots, the thing that you need to do is get into their heads and work out what they wanted, rather than any kind of truth.

G

[FlyingGoat]

B would also appear to be a reasonable answer if you look at this website (http://www.raintoday.co.uk/).

[Contacttower]

My memory of the question was actually that it was asking about airborne weather radar...I may be wrong though...that's just what I remembered it as.

I can't remember exactly but there was something about option A which seemed to suggest that it wasn't the right answer, I can't remember but it may have been prefixed with an 'only' or an 'always' making it unlikely to be the right answer.

At the time I was 90% it was B; from the point of view of getting into the mind of the question my gut feeling was that it was driving at the notion that weather radar can only see returns of precipitation and therefore doesn't necessarily detect other hazards like cells that have yet to mature etc.

That said I see Genghis' logic as well. I guess we will just have to wait and see...(I'm assuming one's results tell you which ones one got wrong?)

The Met IR Exam was a complete abomination though; some questions definitely had more than one answer, some were so simple that honestly if someone couldn't answer they really should think about handing in their licence (like the question about what happens to temperature vs altitude), some just had really bizarre options as answers and most I completely fail to see their relevance to aviation (like pressures over ice vs other surfaces or some such irrelevance).

Only the questions about interpreting TAFs/METARS and Weather Charts were any good, and even then they seemed more interested in one's ability to average out a few spot winds than maybe work out were the ice is going to be.

Hopefully the new syllabus which is starting in October will be better (although its of no relevance to me since I'll still be doing the old one).

Is that the only question you appealed IO540 or did you find some more?

[IO540]

I'm assuming one's results tell you which ones one got wrong?No. No feedback.

Is that the only question you appealed IO540 or did you find some more? In that exam, just the one.

I agree about the bollox, but I could write reams on it and it won't make any difference. It is outrageous that so much crap has to be learnt, and so little of it is relevant to real flight and real flight hazards, and the relevant stuff is mostly missing (other than telling you that you can get clear ice in CBs, hey ho). The AF447 business did not shock me at all; a fresh graduate of the ATPL ground school could be a complete muppet and if he flies regular missions then he will stay that way.

The new exams were supposed to arrive in June but I ignored them because they have been delayed for a couple of years and could be delayed yet again, and because the QB was going to be even more delayed. Without QB revision, this garbage is ultra tedious. Once I have my marks for this last lot, I will tell you which subjects I did using the QB entirely ;)

About the "hail" I am not convinced that you could have small hail which a particular radar won't see. After all, a few years ago some Brit passenger jet had the outer layer of its windscreen smashed by hail, with just the inner layer holding in the hull pressurisation, and I recall a discussion from the time about hail not always being visible on radar, apparently.

[24Carrot]

My course notes back up Genghis.

Strong returns from hail, returns from rain vary with droplet size, poor returns from snow and ice crystals.

But that was in RNAV, not MET.

I also vaguely remember something in the QBs about 4cm waves being especially good for something, possibly smaller raindrops.

[flybymike]

I recall being advised by ATC just before take off, of a heavy shower "coming in fast"
It was snow, and lots of it....

[Whopity]

The reason the JAA professional exams are such poor quality is down to the way they were produced. Questions were submitted to the JAA and then distributed to all the JAA States for comment before they were accepted. By default, no comment meant they were considered satisfactory! In the main nobody had the time or resources to verify the questions so they were virtually all accepted , warts and all. The UK CAA did do an analysis of the first CQB but it was pooh-poohed by the French exam committee chairman. The latest EASA CQB has a quality factor no better than 20-30%. Its fair to say there is no longer any correlation between the ATPL theoretical training and the flight training.

[IO540]

There is also, quite obviously, little correlation between (1) the written study material which a CAA approved FTO is supposedly teaching in the classroom, (2) the QB used in the actual exams, (3) the QB(s) available for revision.

Not just in content but in the weight of certain subjects.

I give credit to the UK CAA for apparently weeding out a lot of garbage. Across 6 exams (HP&L was an exception; loaded with crap) the dodgy-grammar and other dubious stuff was mostly missing. It could be a coincidence but it does look like somebody has gone through it.

Unless, that is, they save the nasties for the re-sit papers ;) ;)

The latest EASA CQB has a quality factor no better than 20-30%.Do you mean the "new" exams (lately due in June 2011) or some forthcoming full EASA IR? I heard a German firm was paid 50 euros per question, to write the latter. OTOH the former, I heard, is still mostly based on the old QB; in fact I have an analysis of it done by an FTO.

[24Carrot]

Googling around, papers like this:
http://www.atmos.washington.edu/gcg/yuter/pdfs/Yuter-MS328_final.pdf

suggest hail is about 5 times more reflective than water, because ice has a different refractive index.

Reflectivity also depends on size. Hail in CBs can be much larger than water droplets, because large water droplets are unstable and tend to break up.

I think I have the '4cm' thing too. Wavelengths above 5cm don't suffer much attenuation, (ie absorption by what they travel through), and so can see further through cloud.

So in exam-speak, 'A' is a 'better' answer than 'B', though both are correct.

--

Also it always surprised me that there was no feedback on wrong answers.

If somebody gets less than 75%, fair enough, tell them to go back and study the subject properly. But lots of people get 90-100%, which means about 0-3 questions are wrong.

So the examiners' message is: "OK, you know everything we believe you need to know, except for just three important things, and we won't tell you what they are!".

[Contacttower]

Without wishing to start an another FAA vs. JAA debate having done IR exams for both now the FAA although being far from perfect had a number of areas in which were far superior:

-Because the demand for IR study material is so much greater one learns out of commercially sold books which are actually written by real people and the material reads in a joined up, flowing way which guides you through the learning process.

-There is no formal "course" process as such meaning the cost of the ground school is kept down; just a sign off from an instructor who will check to make sure that you are ready for the exam.

-The exam itself is done on a computer and you know the result immediately rather than in 10+ days; which is much more reliable than having a paper answer sheet that is then read by a computer and has been known to randomly give people zero.

-You are told which questions you got wrong and your practical instructor has to review these questions with you which keeps the ground school fresh in your mind during training.

-The practical examiner reviews all the essential stuff like flight planning and met before the practical test to ensure your knowledge of it and can cancel the practical if he feels your knowledge is not as good as required.

[HEATHROW DIRECTOR]

<<I recall being advised by ATC just before take off, of a heavy shower "coming in fast" . It was snow, and lots of it....>>

Probably looked out of the window!! A lot depends on the wavelength of the radar but modern ATC radars don't usually show weather. The older, primary radars only showed rain. They couldn't show the location of CBs.

[Whopity]

Having been involved in the calibration of some of the first rainfall radars (Chilbolton) they can definitely see liquid precipitation because they directed us to it.

Just the sort of thing a pilot flying IFR needs to know!
Do you mean the "new" exams (lately due in June 2011) or some forthcoming full EASA IR? I heard a German firm was paid 50 euros per question, to write the latter. OTOH the former, I heard, is still mostly based on the old QB; in fact I have an analysis of it done by an FTO. Yes they are the ones. According to the latest CAA info, old exams will not be valid after April 2012 and have to be replaced with the even lower standard, even less relevant, exams to accord with the latest bureaucracy.

[IO540]

suggest hail is about 5 times more reflective than water, because ice has a different refractive index.

However, isn't straight plain ordinary boring precip a lot more common than hail?

On any given day, have a look on meteox.com and tell me if the red bits are heavy rain, or hail. If they are hail, there is a lot more hail around than is my real life experience - unless most of it melts before it hits the ground like some sort of extra heavy duty viagra (ooops I meant virga).

The exam itself is done on a computer and you know the result immediately rather than in 10+ days

I gather that in Slovakia the JAA exams are computer based, cost 18 euros for the whole lot, and you get the result immediately. So this is anal retention by certain countries, UK included.

Also it always surprised me that there was no feedback on wrong answers.

The powers to be are very careful to stop the real questions leaking out. Even in the JAA PPL, no discussion of the exam questions with instructors is permitted.

It's a bit silly since the ATPL QB is mostly "out" nowadays.

I think that the FAA ATPL system would collapse the FTO system over here, because so few students would pass the oral exam. IME, the FAA PPL and IR questions are about 80% relevant. Not perfect but the JAA stuff hovers nearer to 8% :) The FAA oral exams are mostly a doddle for any existing pilot.

Yes they are the ones. According to the latest CAA info, old exams will not be valid after April 2012 and have to be replaced with the even lower standard, even less relevant, exams to accord with the latest bureaucracy.

I thought somebody took the existing exams and stripped out 15-20% of the questions, rather than writing new ones.

I know about the March (April?) 2012 cutoff for the existing exams. There is a little irony there because if you fail any exam 4x you lose all the passes to date, but with the 2-month CAA exam timetable 4 resits take you to March 2012 anyway :) :)

[Whopity]

Also it always surprised me that there was no feedback on wrong answers. Lets be honest, nobody knows who wrote the question and where the answer came from!
I thought somebody took the existing exams and stripped out 15-20% of the questions, rather than writing new ones.For 50 Euros a question you have hit the nail on the head. The entire CQB was compromised at about the time the JAA folded as the person who received it on behalf of one newly qualified State, took the disc with him when he left!

[IO540]

What does that mean? Is the new exam QB a subset of the old exam QB, or was it freshly written?

It would suprise me if they scrapped a whole QB just because somebody is known to have taken a copy. There must be dozens if not hundreds of people who have access to the QB in each JAA country. They could not all have been positively vetted :)

And weren't 50% of the QB questions released to the FTOs at one point?

[172_driver]

-The exam itself is done on a computer and you know the result immediately rather than in 10+ days; which is much more reliable than having a paper answer sheet that is then read by a computer and has been known to randomly give people zero.

In Sweden JAA exams are computer based since 2006 (..something) and you get the result right away. But they don't tell you which ones you had wrong. The first JAA exams I did though were on paper. After everyone had finished their tests we switched with our mate and corrected each others :O

Speaking about the whole JAA theory education system, I have totally lost faith in it with all QBs circulating. It's completely eroded. What my students say is they recognise 90-95 % of the questions on exams by doing Bristol QB. People with questionable knowledge score 90+ %. It's not a good measurement of knowledge anymore.

And there is more to it. OPP being a good example. EU-OPS is a living document that is continuously being amended and updated, Subpart E All Weather Ops recently had major changes. Asking my national CAA if the questions in their QB will reflect these changes they say No. So you purposely have to teach old stuff that is no longer valid just for them to pass the tests.

[IO540]

I have totally lost faith in it with all QBs circulatingThat's not the problem, however. The real problem is that the course content is mostly irrelevant to flying, and as far as I can tell has been irrelevant for many years.

All that Met stuff about a warm occlusion being warm air pushing under cold air (or whatever) is fine for drawing fancy pictures in the classroom, or in the ATPL textbooks which fill the shelves in pilot shops, but there is no practical way to relate it to real life and make operational go/no-go decisions on the basis of it. Both private and commercial pilots make operational decisions on the basis of professionally produced weather data: tafs, metars, sigwx, etc, etc.

Objectively, this stuff should not be taught to pilots. It's a waste of their time.

The FAA IR does not teach it in that level of detail, and there is absolutely no evidence that aviation is less safe in the USA, or less safe among US licensed pilots flying outside the USA. More safe, if anything.

The question banks have always been around. Originally, many years ago, the largest FTOs compiled their own question banks by assigning each exam cadet 5 questions to remember, and a man from the FTO stood outside the exam room with a notepad and quickly noted down the details before the cadet forgot. Over years, each FTO built up a QB, which they used internally, sprinkling the "real" questions into their assignments.

Sure it is possible, in theory, to pass the exams without opening the study material, with zero aviation knowledge, just using the QB. (Actually you can't quite do that because you have to open it to do the FTO homework). It would take a huge amount of work though, even for a current pilot doing a ICAO IR to JAA IR conversion like I am doing.

I reckon HP&L is done totally off the QB in most places...

[FlyingGoat]

More safe, if anything.

Any chance of elaborating on that?

[englishal]

Depends if it was an faa radar or jaa radar. Faa radar will show lots of weather, jaa radar will hardly show a txpdr return (well they keep complaining about "poor radar performance" anyway)

[Contacttower]

Depends if it was an faa radar or jaa radar. Faa radar will show lots of weather, jaa radar will hardly show a txpdr return (well they keep complaining about "poor radar performance" anyway)

:D:D:D That did make me chuckle...