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## Take off charts and cross wind

• Flightanaesthetist
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### Flightanaesthetist created the topic: Take off charts and cross wind

Hi,

Did the theory PPL exam yesterday and passed. Take off charts were a little more tricky than expected . Had up slope one runway with a tail wind and down slope other runway with headwind. Question is the wind was a crosswind 15 knots of about 40 degrees. Does one calculate the headwind component using the EB6 flight computer or the clock method for crosswind on landing ?

Also interesting in the exam was about three questions re EGT and how to lean the mixture based on EGT . Also one relating to CHT and interpreting an abnormal reading . I don't remember seeing this material covered in any of my reading .

• John.Heddles
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• ATPL/consulting aero engineer
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### John.Heddles replied the topic: Take off charts and cross wind

Question is the wind was a crosswind 15 knots of about 40 degrees. Does one calculate the headwind component using the EB6 flight computer or the clock method for crosswind on landing ?

The mental gymnastics techniques are useful and necessary for when you either don't have the kit to hand to run the sums, or don't have the time/ability to use the kit. However, if you can use the kit, why not get the benefit of the more accurate answer ? So my suggestion is, when feasible, use the computer.

Also interesting in the exam was about three questions re EGT and how to lean the mixture based on EGT . Also one relating to CHT and interpreting an abnormal reading . I don't remember seeing this material covered in any of my reading .

I don't have Bob's systems texts to hand. However, this is really basic stuff which will be in the books, I am quite sure. No doubt Bob or Stuart will offer specific comment when they see this thread.

Engineering specialist in aircraft performance and weight control.

• Flightanaesthetist
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### Flightanaesthetist replied the topic: Take off charts and cross wind

Im not sure how much detail I can go into without breaching CASA regs but the level of question re EGT in the exam needed much more info than is available in either Book one or two of Bob Taits books.

Re Take off charts, I had only encountered questions pre exam with a total headwind component, so my query was ... For example the runway is 36 and the wind is 15 knots at 320 degrees, does one than use the EB6 to calculate the headwind component as it will change the take off calcs ?

• John.Heddles
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• ATPL/consulting aero engineer
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### John.Heddles replied the topic: Take off charts and cross wind

Im not sure how much detail I can go into without breaching CASA regs but the level of question re EGT in the exam needed much more info than is available in either Book one or two of Bob Taits books.

I would think that, should you pose an hypothetical question (to whatever detail), any resemblance to a CASA exam question could only be coincidental ? I think CASA's concern is wholesale fraudulent cheating rather than bona fide training considerations. Keep in mind that, in prior times, CASA (or its antecedent entities) used to release the actual exam questions post exam for Industry training use.

Certainly, without the detail, we cannot offer any sensible comment.

Re Take off charts, I had only encountered questions pre exam with a total headwind component, so my query was ... For example the runway is 36 and the wind is 15 knots at 320 degrees, does one than use the EB6 to calculate the headwind component as it will change the take off calcs ?

We make the (not quite correct) presumption that the crosswind doesn't materially affect T/O and landing distances. Any headwind or tailwind (whether a direct up/down the runway or vector component) will have a measurable impact on the distances and needs to be accounted.

Clearly, if the wind is at an angle to the runway, only the headwind/tailwind vector component of the wind is of interest so, indeed, you must figure that component else you are running fanciful calculations of little relevance to what is going on. There are various ways to run such vector resolution calculations and the preference will always incline to the most reasonably accurate unless there be other pressing reasons why a less accurate calculation might be more appropriate on the day.

You can use -

(a) Dalton style computer and get a pretty accurate graphical vector resolution (assuming the instrument has a square grid - not all have),

(b) Jepp style and get a similar result (using the wind scales),

(c) Jepp style and get a trigonometrically derived answer (of greater precision than is warranted),

(d) any of the various mental calculations.

Point is, however you go about it, you have to figure the resolved head or tailwind component for the charts.

Engineering specialist in aircraft performance and weight control.