Flight Planning Question

[tik_nat]

Hi all,

Just missed my second attempt at flight planning by 2%.....gutted. First attempt was no good because I'm an idiot who can't use a calculator, but this second attempt has me stumped. Good results on practice exams before both with plenty of time, but still no dice.

Are there any ROT that people use regard when to break up a sector or use an average (how many degrees track change, wind change, temp change etc.) There doesn't seem to be constant method and when you answers are sometimes only a few hundred kg apart, I find this to be a real guessing game.

There is one question that has popped up in both exams relating to a min fuel / max payload flight asking of a BRW. The temps are fairly high (ISA +15) with holding at the destination, so the opitmum level is not available at TOC due cruise thrust limits (again, by a few hundred kg only). In this case, do they expect me to plan a step climb in the middle?

A 0.79 cruise would allow optimum level at TOC, but they specify M0.82. If it were truly a max payload/min fuel flight, why are we trying to get there so quick?

Third attempt on July 1......does anyone know when exactly this new exam system comes into place. The website just says July.

Cheers

Tik

[Captain Nomad]

If you are in Newcastle you are just around the corner from Reg Litster at ATVC. Top ATPL theory guru and you could organise a little coaching session with him perhaps?

http://www.atvc.com.au/Posts/Articles/New-ATPL-Flight-planning-course-now-available-from-ATVC

[Hailstop3]

If you aren't already, start from the back of the exam on the hardest questions and work forward. That way you can spend all the time you need on the hard ones and if you miss a few at the start because of timing then you will only lose 1 or 2 marks rather than 5 or 10. Sounds simple but is a tried and true process and worked really well for myself as well as many others I know.

[landlocked]

1) Before you decide whether to average, have a look at how close the answers are. The closer the answers, the more accurate you need to be. There is evidence to suggest that CASA is not a huge fan of averaging unless tracks and weather are very similar. When in doubt, split the flight into more sectors.

2) Step climbs will not give a minimum fuel answer unless at the higher altitude for long enough to recover the fuel used in getting to the new altitude (typically 200 kg). I would consider a step climb if the flight was over 1000 nm. On a flight from Darwin to Melbourne (about 1700 nm), you might expect a difference of about 250 kg between the 2 plans, depending on actual weather.

3) Make sure that you are accurate in calculating TAS and ground speeds. CASA is now most likely using electronic validation of calculations, so you need to apply the effective TAS loss even when the drift angle is only 5° (despite what the Jeppesen instructions say: see new exam information book). Make sure your CR3 is calibrated correctly before you attempt the exam by comparing ground speeds from your CR3 with electronic calculations.

[tik_nat]

Thanks guys,

slam_click, I did have a look at the info booklet and have been using the numbers in it for my calculations. I did use 0.82......i was just saying it didn't make sense to do so real world if you were truly aiming for a min fuel flight. That said, I will slow down a little bit next time....i had 30 minutes and went back to check some of my 5 mark answers (I did the exam backward)

Next time, I'll take it a little slower for the 5 markers to get them accurate first time and use the extra time at the end to check some of the smaller mark questions.

Thanks for the info on the step climb. I know the practice exams specified a step climb if they wanted it, but the POH says to plan for a step climb if it helps (of something to that effect). I'll also hunt around for a CR3...I've been using a CR4 thus far which has worked out in the prac exams, but I'll need all the help I can get.

[Username here]

If you aren't already, start from the back of the exam on the hardest questions and work forward

Can't agree with you more mate, this got me through the exam - was over it after 2 1/2 hours, luckily I only had 1 and 2 markers left. Passed the exam last Friday! Best feeling in the world, beers taste better after flight planning!!!:ok::ok:

[landlocked]

A couple more thoughts that might help:

1) Regarding averaging tracks: averaging track changes of about 10-20° is not usually significant is the wind is close to all headwind or tailwind. If the wind is a quartering wind (about 45° either side of track) the averaging technique becomes more of a risk. That being said, there is not much you can do in a climb or descent other than average tracks.

2) In the climb or descent, do NOT round the ETI or distance. Use the unrounded figures in the calculations. This is what CASA is most likely doing.

3) I suggest that legs over 400 nm are starting to get risky unless there is a constant track and weather.

[tik_nat]

Landlocked, i've been rounding climbs and descents, so I'll stop doing that.

One for audience regarding the min fuel / max payload question I can't figure out. I'll give the numbers as best as I can remember without the actual info so CASA does get upset (I'm sure they're watching);

MAX Payload, Min Fuel
Cruise: M0.82
Distance: 980NM
INTER conditions at destination
Winds about 50-70kt H/W all the way
ISA + 14 at F300. ISA+15 at F340.

Question asks for BRW, however I'll simply ask in this forum the bit that had me stumped......what is my initial cruise level?

Even the lowest answer available (just over 81 000kg) ends up with a TOC GW figure greater than cruise limits at all levels in the ALT CAPE. I went back and triple checked the ISA variation, since ISA +10 poses no issue, but ISA+15 is out.

Any ideas?

[cabzjet]

Not sure if you were doing this already. But here goes

1. Find Estimated fuel burn (Dist X Rough SGR + 1500) then 10% for VR to go with step 2

2. Find LW which will be MZFW 63500 + FR,VR,holding etc (max payload, min fuel)
3. Add Estimated fuel burn to LW to find Est BRW. Minus approx 3000 if FL 310 or >.
4. Alt capability.
5. Confirm and check Alt capability with Climb chart Fuel burn.
6. Plan back from LW
7. Done

- If you have AFT cyber exams refer to AFPA_40

Hope this helps.

[landlocked]

I suggest you work backwards from TOD at the optimum altitude to a point where you reach the thrust limits for that altitude/weather subdivision, then put in a step climb from a lower altitude that you can maintain in the previous subdivision. You might even have to have 2 step climbs if the route is long enough, particularly if the departure airport is in the tropics where temperatures are high.

[Username here]

You might even have to have 2 step climbs if the route is long enough, particularly if the departure airport is in the tropics where temperatures are high

Whoa...slow down there big man! I did a lot of questions in the lead up to my exam plus the actual exam and I have never seen a question which required multiple step climbs without telling you to include a step climb in the wording of the question. If this was required I'm sure Nathan would have an example somewhere in the book/exams to give you a heads up.

If it doesn't ask for a step climb - don't do one!!

I had two full flightplans (one was a find the MBRW as per your example) in my CASA exam which didn't stipulate whether to use optimum or highest possible FL. I used highest level and got them both correct.

[landlocked]

Let me qualify my statement about step climbs:

1) Although I have seen a practice exercise that required 2 step climbs to obtain the minimum fuel requirement,question it would be very unlikely to need 2 step climbs in a CASA exam.

2) The B727 Performance and Operating Handbook (For use in ATPL(A) Flight Planning Examination) states: "Enroute step climbs from one cruising level to a higher cruising level, made to optimise cruise performance as fuel is burnt off should be planned when appropriate" P2-2, section 13. The exam question does not need to state that a step climb is appropriate.

If the temperature is too high at the departure airport to get anywhere near the optimum level and maintains flight to the destination at the lower level, the flight will not be a minimum fuel flight. If the flight is short, it is usually not worth using the extra 200 kg (usually) to get to the next level. However, on longer flights (probably about the 1000 nm or longer) the loss of fuel in the step climb is more than recovered by flying at the more economical altitude.

As a rule of thumb, a step climb could be considered when departing from tropical departure airports and heading south, if the flight is about 1000 nm or more. (Eg: Cairns to Perth, Darwin to Melbourne etc). The sooner the step climb can be made, the more likely that it will be a lower fuel burn off than maintaing a constant altitude.

[drpixie]

tik_nat - not sure what you're doing, but it 81t sounds very heavy. Max payload means max attainable payload for that flight in those conditions - will very likely be much less than max allowable payload. If you can't carry payload X and required fuel at M.82 ISA+15, then X is too much payload.

[tik_nat]

Cabzjet - what you describe is exactly what I'm doing. I did the cyber exam question you speak of the night before the actual exam and got it correct.

81T was the lightest available answer (from memory). The question asked for BRW planning max payload/min fuel. If anyone can let me know what the MAX LEVEL is for BRW 81T at ISA+15, I'd love to know how you worked it out.

If it's not possible, I'm starting to think my recollection of the question is not so great or I miscalculated the ISA deviation and got myself so convinced of it, maybe made the same error when checking it 3 times (I checked at F300 and F340.....ie TOC, not 2/3 climb for ALT CAPE).

One thing that just came to mind is that I didn't even consider a VERY low altitude on depature (ie F260). I think the F235 ISA devation was +10 (the F180 certainly was +10).

Either way....i think it's time to let it go, hit the practice questions again and hope like hell I don't get another question like that!!

As a side quesiton - what wind do I use for a F210 cruise. The exam booklet says interpolation is not necessary, so do I got to F185 or F235?

[Username here]

As a side quesiton - what wind do I use for a F210 cruise. The exam booklet says interpolation is not necessary, so do I got to F185 or F235?

My notes interpolated 185 - 235 wx.

Which course are you using mate? I had a couple of issues during my prep (I self studied) emailing Nathan cleared up every issue I had - no need to wait for an answer from PPRUNE - and I knew the answer he gave was correct - gave me a heap on confidence before the exam - I found flight planning is all about speed and confidence!

If you're not already using AFT you're making it hard on yourself fom the get-go! My opinion anyway...

[landlocked]

CASA has implied that they will create artificial weather so that 185 and 235 are virtually the same if you need to cruise at 210.

[tik_nat]

Another one that's popped up - when asked for a TAS at MIN HOLD Speed, I assume you use 200KTS indicated at all levels and then derive a TAS from that? This is as opposed to MIN DRAG speed, where you derive the IAS from the table then work a TAS from there.