CPL MET questions, help please!

[Aussie]

Just about to sit a CMET exam, was after a few answersto questions i didnt think Uncle Trev covered very well...

What exactly is Diurnal variation? What are the factors that affect diurnal variation of wind?

What would the pilot experiance in the cockpit flying through an inversion?

Q. You are flying on track at 5000FT. Ahead are occasional CB in your way. Best way to pass them is...

A. flying straight through them?
B. Flying underneath them?
C. flying around the boundary?
D. flying inbetween the seperated CB?

This was an actual question i was asked in PPL and i thought it was D for sure. My instructor agreed. Dont know what CASA is thinking?

Any help?

Cheers!

[HEALY]

OKay here we go. Had a few brews so the answers may stir more debate than fact.

1) Diurnal variation is the changes over a day ie 24 hours. Therefore the factors that effect wind would be temperature differences between the land and sea creating land and sea breezes. Localised factors such as valley winds eg will also be created

2) Thru a temp inversion it will be bumpy below and thru the inversion however once above normally fairly smooth (from experience however dont take for gospel) as the temp starts to decrease again. Visibilty will also be reduced depending on type of pollutants in the air

3) If you have CB's around it obviously means a bumpy ride if your down below 10000. Thru will see you in large updraughts and possible downdroughts from what could of been a dissapating storm, Underneath more of the same depending I guess what the base is. The boundary will be rough as well and could se you in it if your downwind of the CB. Answer i guess is D ....buts its a stupid question really.


Good luck dude

[readbackcorrect]

try c....

Occasional cbs can have a habit of becoming somewhat more occasional, ie they spawn more, discharges between the clouds may also occur and windshear associated with one clouds updraught and the others downdraught may prove somewhat testing for most aircraft.

But on days like this i usually go fly a kite instead, with a metal key attached...


:oh:

[Jenna Talia]

C. flying around the boundary?

I would also say that C would be the correct answer, but I do not quite know what is meant by 'boundary' as I have never seen or heard this term used in almost 20 yrs of commercial & airline ops.

Attempting to fly in between CB's (although, it does not say the distances) within close proximity to others can be fraught with danger due to the lightning strike factor.

I see that CASA exam q's are still either not clearly defined or ambiguous.

Good luck.

[HEALY]

Jenna Talia is right about ambiguous. The term 'Occasional' seems to be a key word here although no spacing is defined. It could mean 1 CB here and none for miles or well spaced groups.
If there is a gap of more than 20 or 30 miles then "What me worry" I guess

[Lodown]

IMHO...

Q. What exactly is Diurnal variation?

Healy has answered that one.

Q. What are the factors that affect diurnal variation of wind?

Ans. Without a textbook nearby - temperature and atmospheric pressure are two changes that occur on a daily basis that affect wind.

Q. What would the pilot experience in the cockpit flying through an inversion?

Ans. Possible wind shear with changes in wind direction and/or speed associated with the inversion. A night time inversion can be smooth above and below with a couple of bumps at the inversion layer. If the cockpit has direct venting from the outside, the pilot may also feel the temperature change.

Q. You are flying on track at 5000FT. Ahead are occasional CB in your way. Best way to pass them is...

A. flying straight through them?
B. Flying underneath them?
C. flying around the boundary?
D. flying in between the separated CB?

Ans. D. flying in between separated CB.

There's no defined boundary or additional detail to the description of occ. CB, so flying around some imaginary, nondescript boundary in answer C is not the best option. Diversions, turn arounds, land and wait them out, are not provided as options in the answer. Best answer of those available is D.

In reality...A, B, C, and D (and others) are all options, but D is the best one of those provided.

Q. Don't know what CASA is thinking?

Ans. Who does? Is there a list of multichoice answers available for this one? If so, I'd feel relatively safe answering, "None of the above."

Jenna Talia, what is the "lightning strike factor"? It might just be me, but in my experience that is probably No. 101 on my list of 100 priorities when passing CBs.

[Jenna Talia]

Lodown,

As quoted from the trusty old, 'Manual of Meteorology' Part 2, 'Aviation Meteorogy' under the heading of Lightning, page 65:

Lightning is the electrical discharge that occurs across the very large electric potentials that are set up within single cumulonimbus, between adjacent clouds and between the cloud and the ground. The last of these three has the largest voltage. Cloud to ground discharges are less common than cloud to cloud.

I can vividly recall flying between two CB's one night in a PA31 when all the hairs on both of my arms stood straight due to the amount of static electricity present.

I never did that again.

[Lodown]

Sounds like an exciting experience. Thanks for the quotes. I was trying to find my met. manuals with no luck. They'll turn up one day. I was thinking of all the other hazards around CBs like hail, IFR conditions and wind shear. Lightning was well down the list just because it is difficult to pick one place to fly that is any better than another regarding lightning in proximity to a CB and most aircraft are reasonably well protected. There are also reports of lightning emanating from the tops of CBs and going up.

[readbackcorrect]

Well lodown this goes to show u that c is correct. Flying far from any cb is advisable. When u have another nearby u are now restricted to flying equidistance from either, significantly reducing the leeway as compared to if only one was present. To me the term boundary would suggest the area where ambient weather conditions as opposed to fully blown cb conditions exist. Ie unaffected area.

U hear about the skydiver who entered a cb? Apparently took 30 mins to reach terra firma.

Well if any big jet pilots are reading what is the accepatable distance to fly around a cb? I imagine its intensity on radar plays a big part and also the tops are a consideration.

Anyways have u done the met exam?

[Freddy Fudpucker]

C is the answer. Fly on the freestream upwind side. Flying inbetween ( or down the bowling alley) can turn very ugly quickly, as the sister cells can merge and turn into a super cell (not that likely anywhere other than in southern australia)

There are different kinds of inversions but all will include a wind vector and temperature change. So in the cockpit you will experience turbulence, ground speed change and a rise (on climb)on the OAT gauge.

[Lodown]

Once again, it's just my opinion...

The question is asking about occasional CBs from a pilot's perspective, not a blanketed sky of ginormous thunderstorms with severe lightning and Force 10 winds, bowling alleys and what-not. And certainly not from the perspective of some nut dangling from a parachute who ascribes to answer A.

Fly in between the things and around the individual CBs. If they turn into massive thunderstorms or super cells, well then plan on other routes, but that is not what the question asked.

Freddy, freestream upwind side is not in the answers. Nice to know, but won't get a mark on the exam. One of the presented answers mentions the cells are separated. Whether they merge, join, or form some lesbian relationship is moot to the question.

If your destination, whether it be Sydney, Brisbane or Come-by-chance reports occasional CBs, do you and every other inbound aircraft fly to an alternate and wait it out?

Unless you sit in the inversion or have some digital readout, most OAT gauges are so slow, they won't register a thing and trying to pick up a momentary one or two degree temperature change on an OAT gauge while you blast through on climb or descent would be pretty tough.

[swh]

CB's and Lightning....

Lightning is caused by ice crystals, sometimes they will ask "What is lighning and indication of "

Lightning normally only occours within +/-5 degrees (i.e. +/- 10,000 ft) of the freezing level, may come from the top, side, or bottom of the cloud

If you see lightning and your in an aircraft that is not certified for known icing, lightning is a good indication to change course as ice may be present.

Aircraft certified for known icing, are not certified for severe icing.

readbackcorrect

At 10,000 with sharp or scalloped edges 5nm, less than FL200 if there is a rapid change in shape 10 nm
Above FL200 to FL250 10nm
Above FL250 to FL300 15nm
Above FL300 20 nm

To clear above a Cb, 5000 ft.

:ok:

Edit : added +/- for clarity

[tinpis]

http://fototime.com/%7B254F0026-C98D-45B1-9C73-F7101A2744BD%7D/picture.JPG


:( Tin sees lightning selects answer D:


D: Reach over to balcony beer fridge select

http://fototime.com/%7B13643E38-A77E-44A9-A1C9-0FFBB5789D95%7D/picture.JPG


Thinks of countless thankless night flights with Flying Doc and aero med...

[Lodown]

Thanks swh. Very informative.

[NAMPS]

Just to add to swh's post, I was taught to divert towards the upwind side of the CB (i.e. the other way from where the anvil is pointing).

[tinpis]

Just to add to swh's post, I was taught to divert towards the upwind side of the CB (i.e. the other way from where the anvil is pointing).

Doesnt work on a horses guts night in an A/C that doesnt have Wx radar.

[maxgrad]

swh, is that from your co's sops?
my co's sops state 5 nm ground level to 20 nm fl200 and greater, interpelate in between.
CASA really are wizards when it comes to writing exam q's ...... NOT

[swh]

maxgrad,

If memory serves correct it was in an AIC at one stage, and no it not my company sop.

:ok:

[Aussie]

Thanks for all the replies...who knows what and or how CASA thinks?

Just another quick one. WIth Tempo and Inter in weather forecasts...we use a half hour before and after safety buffer.
So if our ETA falls within the TEMPO or INTER eg
ETA for YSWG is 0945 and the TEMPO reads
TEMPO 1002 blah blah blah, then we would have to take that TEMPO into consideration because half hr before the TEMPO starts is 0930 and our ETA is 0945....
Hope thats not too confusing...

Anyway, what about when we have FM 1002 blah blah blah blah...

Do we add the half hr before and after buffer to it?

Thanks again guys, appreciate it!

[maxgrad]

aussie oi oi oi
sorry couldn't help myselp:p

With INTER and TEMPO
30 mins b4 and after
if your ETA falls within period then you must take it into consideration
eg TEMPO with TS etc finishes at 10, and your ETA is 1010, you must carry holding fuel or diversion fuel

[Aussie]

Yeah righto Maxgrad!
Thanks for the answer mate, but do we add that safety buffer to a

"FM 1002 SCT CU 050"

would i need to add that buffer onto that?

Also, if flying through as inversion on approach, would anything happen to the altimeter reading as i pass through the inversion?

Cheers again!


Aussie

[maxgrad]

generally speaking with a FM period or TEMPO or INTER, If you are going from an operational req to the removal of that req,(bad to good wx) are you arrival time is within 30 mins then you have to plan for flight regarding the operational req (bad wx)

0210 (bad wx) operational req

ETA 1010 utc, plan using bad wx info, even though it is expected to improve.

ETA 0145 utc, plan using bad wx info

FM02 (bad wx)operational req

ETA 0145, plan using bad wx info

hope I'm making sense here as it's damn late

[Lodown]

Also, if flying through as inversion on approach, would anything happen to the altimeter reading as i pass through the inversion?
No.

One thing to be aware of is that during a strong inversion at night (which seem to commonly set up around 100 ft or so), a change of wind at the inversion can play tricks with your established approach. There may be times when you fly over a field in the dark with few other references, look at a stationary windsock and subsequently fly an approach with a significant tailwind wondering why the aircraft is having trouble slowing down and descending. Then you get through the inversion layer and you have to drag the plane to the runway. Another situation occurs when you fly an approach into a headwind, get through the inversion and then wonder why you're overshooting your aiming point. I seem to remember Woolongong as being an example when westerly winds were blowing up high and a surface inversion and the hills to the west created calm winds on the ground.

Night time/early morning inversions affect balloons in a different way. If they've been above the inversion for a while and coming back down, they tend to bounce around on top of the inversion until temperatures adjust or lifting gas/hot air is dumped.

[Freddy Fudpucker]

Lodown, I take offence to the tone of your reply to my post regarding the original Q. The answer is C. The expontentials are to give the young bloke an insight into how I came about obtaining the answer. There are two accidents I can think of off the top of my head where experienced crew flew between CB's and got caught with the strides at half mast. Also Inversion temp changes can last for 1 or 2000 feet.

[swh]

Freddy,

Not that is of much importance to day to day flying ... the highest recorded temperature inversions occour over India, reguraly measured to extend 55000-72000m in winter to 70000-83000 m in summer. Inversions of 100 degrees have been recoreded.

:ok:

[Jenna Talia]

Freddy,

Were the accident/s due to the CBs forming into one?

[Lodown]

CASA examiners must be loving this. They have an answer that would be marked correct and a close answer that would be marked wrong. Supporting arguments have been given for both.

Aussie, have fun trying to decide.

Freddy, in the accidents you are thinking of, was the sky coverage "occasional"? I'm not disagreeing with your facts, however the original question as presented by Aussie specifically refers to "occasional" sky coverage and flight at low levels.

[Aussie]

Gday all,

just to let you know i have passed my CMET today.

Cheers to all that helped me!

Speak to yas soon!

PS. that Thunderstorm q. poped up again, and i got it wrong by selecting flying through the gap...so it aint D!

Seeya!

[maxgrad]

well done Aussie,
if not doing so already, keep all your training notes and stuff, you never know when it will come in handy
congrats again

[Lodown]

Hey well done. That's one debate for which we now know the outcome for sure. Thanks for the follow-up.

[Freddy Fudpucker]

Jen one accident I think a 717 in the states involved two cells forming into one biggun'. The other involved occasional embedded cb's. The crew using a weather radar picked the path between two thunderies and ended being in uncontrolled flight for over a minute and a half. Scary stuff.

[NAMPS]

tinpis

Doesnt work on a horses guts night in an A/C that doesnt have Wx radar.

Absolutely correct ... my answer was given on the basis of the CPL 'Day' VFR Syllabus :ok: