May I suggest that you post two or three specific examples with which you have been working along with some description of how you have been approaching the problems ? That way, our comments will relate to what you have been doing previously and should provide more learning value for you.

[color=blue]accurately interpolate values on the P charts[/color]

Graphical work is fairly standard and a bit of practice will sort out your problems. Some performance charts are well-drawn, others are pretty dreadful. That is an unfortunate fact of life in the piloting world, I'm afraid. With such charts as you post, we can to and fro until you get the basics well under control.

[color=blue]winds that are upwards of 60° off the runway heading, I have no idea how to calculate the headwind component[/color]

This is a resolution of vectors problem. Once you get on top of the technique, it is just a matter of step 1, step 2 and your answer tumbles out of the other end.

Please do post several scanned examples and we can go from there ....

[size=4][/size]The wind component table in the AIP GEN 2.6 or most flight computers have a conversion scale to solve the component problem.

[attachment=2194]components.png[/attachment]
[attachment=2196]Slidecomponent.png[/attachment]

Adding to Bob's comments, we will show you how to figure the components exactly, providing you have a Jepp CR style computer. Dead easy technique and quicker than pulling out the AIP page.

Thanks for your reply, as these were CASA exam questions I don’t have them. But some of the figures were PH 3500ft, 080/15, 1.2% slope, runway 02/20 can’t remember exactly what the runways were but made up one, no mention of particular aerodrome. But the winds were at 60° off the runway. Both questions I encountered were using figures where you’d have to interpolate the values in each box.
One of the questions was using the Cessna style takeoff charts, where as the other was using the echo landing chart

OK, I presume that you are studying with Bob's books.

How about you scan a couple of charts from the book, work some made up examples, and then post your manuscript workings of those.

The only way we can help you, effectively, is by working through examples with you .... a bit like being able to watch over your shoulder in class while you do the work yourself and we can comment along the way.

If you are using someone else's books, scan the charts from that material - makes no difference to the story.

I’ll endeavour to get it to you when I can.
Adding onto my previous comments, yes I am using bobs books, and PPE.
Was there anywhere within the book that talks about interpolation of charts, finding xwind/headwind components using an E6B (ASA version). I have a rough idea of how to get a reasonable answer, although unfortunately I’ve come straight from RPL so I’m finding it difficult trying to learn these charts with no prior experience that would have otherwise been gained doing PPL

Interpolation needs to be sensible, but not of microscopic precision. Generally, chart parametric lines aren't too wildly non-linear so a linear interpolation is OK. Some comments on interpolation in this thread FYI

https://bobtait.com.au/forum/performance/6817-echo-loading#13455

I gather that Bob's current books have some words regarding the sloping rule trick.

Most folk use the cheat sheets shown in Bob's earlier post. However, if you happen to be using the CR whizz wheel, you can do the exact trigonometric calculation on which the cheat sheets are based. The Dalton whizz wheel (eg the ASA device), however, is a straight graphical wind solution so there is no need for the trigonometry - so you miss out on that trick.

Don't fuss too much about missing PPL, I could run you straight to the ATPL exam without any of the lower licence work. Not a good idea, but doable.

How would you go about interpolation the Echo P charts for instance? The grids aren’t exactly even (11mm for the PH, slope % near radiates outwards from a single point off the page I would suspect?, also wind speed are 1mm apart on the takeoff chart)

Here is a little trick I learned back in the early 90’s for roughly calculating headwind comps:
Take 115 minus the angle between RWY and wind. Then work the % of the wind;

Example:
RWY 140
Wind 170
Wind speed 40kts

Easy Maths Now:
170 –140 = 30
115 – 30 = 85
85 x 40/100 = 34kts
H/W = 34kts

And another;

RWY 280
Wind 220
Wind speed 20kts

280 – 220 = 60
115 – 60 = 55
55 x 20/100 = 11kts
H/W = 11kts

I traditionally try and work out stuff in my noggan before checking with the CR3 and charts. What Bob and John suggest is great advice, but try the above mentioned method from time to time even just to get a rough idea and increase your speed for these calcs. Hope this helps.

Echo is the old DCA P-chart format (DCA was the original incarnation of CASA). Not 100% on who designed the format - a bit before my time - but, almost certainly, either Icko Tenenbaum or John Fincher who were the head men in Head Office performance back then. Superb engineers and top blokes, both of them. The beauty of the approach, for those of us playing engineers out in Industry, was that the format was standardised and they all worked to the same set of equations. DCA published a couple of tech memos for information - as I recall, those were authored by Ian Cohn and Ron Saunders who worked for Icko and John - I'd have to dig in the dustiest of dusty filing cabinets to locate my copies to double check on the memory cells. If neither Icko nor John developed the technique, I suggest that Ian and Ron would have done the deeds. I thought they were a pretty good attempt at a standardised chart structure and the approach was good so far as practical accuracy was concerned. More to the point, any developmental flight testing only required very simple work - read low cost for the applicant - and was easy work to do.

[color=blue]The grids aren’t exactly even
(a) 11mm for the PH,[/color]

These are just density height grids. The individual lines ("parameters") are pretty linear (straight) and the intervals between the lines are pretty linear as well (would fit reasonably on a straight line were we to read some points and cross plot them. Pragmatically, one would interpolate by Mk. 1 eyeball. If you wanted to do a bit better, the sloping rule trick would be just fine.

The distance grids are modestly non-linear (and not well drawn for the takeoff chart) but, for all practical work, treat them as linear for interpolation.

The surface grid provides for three accepted rolling coefficients of friction. Interpolation is inappropriate.

[color=blue](b) slope % near radiates outwards[/color]

As to whether the lines meet somewhere, I have never even thought about that. I would need to revisit the first principles equations to make an assessment. In any case, not of any real relevance to anything in particular. If you were after better accuracy, it would be necessary to cross plot. However, for practical purposes, linear interpolation would be close enough so, again, the sloping rule trick is fine.

[color=blue](c) wind speed are 1mm apart on the takeoff chart[/color]

First, be very aware that there is a sharp discontinuity in the interpolation at zero wind. This is due to there being a 50% conservative factor for headwind and a 150% pucker factor for tailwind. So never try to interpolate across the zero wind line. For headwinds, the interpolation functionally is linear, as is the tailwind so, again, the sloping rule trick works fine.

Here is an aid to accurate interpolation that I have included in the CPL Performance book.
[attachment=2197]Screen Shot 2022-11-09 at 8.35.35 am.png[/attachment]

Thank for this Bob, I saw this in your book beforehand. I've tried using this trick but the graph's aren't 10mm apart, so skewing the ruler doesn't fit the box. It's printed on an A4 page, so I'm not sure what I'm doing wrong

[color=blue]the graph's aren't 10mm apart, so skewing the ruler doesn't fit the box.[/color]

You're missing the point, I fear. The idea of the sloping rule is to aid the eye in interpolating even divisions - works on the principle of similar triangles. Doesn't matter what the actual dimensions might be. More to the point, you are using the rule as a convenient set of equally-spaced divisions - no more, no less.

If you want to use the trick, set up whatever number of divisions fits comfortably in the dimension available to suit the requirement.

Typically, if you can fit in 10, that's great for most needs. If you only can fit in 5, run with it. If 2, that's all you can manage. It still is better than a simple eyeball interpolation for the typical pilot. On the other hand, with a fair bit of practice, eyeballing and simple pencil marks can work really well. An experienced engineer or draftsman does this all the time to aid in drawing work.

Also, keep in mind that GA P-charts are not microscopically precise and have a bit of in-built fat in the numbers. I've made quite a few of the Echo style charts in years gone by - they are of reasonable and pragmatic accuracy but, by no means, precision data. Different matter with recent heavy aircraft where the numbers are processed far more accurately and, invariably, drawn using high accuracy computer kit.

Looking at Bob's post No. 12, the parallel lines example is linked up to the vertical scale. This doesn't appear to be a very easy way to pick a point or line between two of the graphed lines as far as I can see. It seems that we are normally trying to pick a position between two graph lines rather than between two scale positions. Am I missing something here ?