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Welcome to the CPL Performance question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.
wabigail created the topic: Takeoff and Landing P Charts
Any advice for being able to accurately interpolate values on the P charts? I cannot find any examples anywhere, they have been the bain if my existence. Also, they’re giving winds that are upwards of 60° off the runway heading, I have no idea how to calculate the headwind component for this. Any help would be appreciated
John.Heddles replied the topic: Takeoff and Landing P Charts
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.
accurately interpolate values on the P charts
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.
winds that are upwards of 60° off the runway heading, I have no idea how to calculate the headwind component
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 ....
Engineering specialist in aircraft performance and weight control.
John.Heddles replied the topic: Takeoff and Landing P Charts
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.
Engineering specialist in aircraft performance and weight control.
wabigail replied the topic: Takeoff and Landing P Charts
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
John.Heddles replied the topic: Takeoff and Landing P Charts
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.
Engineering specialist in aircraft performance and weight control.
wabigail replied the topic: Takeoff and Landing P Charts
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
John.Heddles replied the topic: Takeoff and Landing P Charts
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
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.
Engineering specialist in aircraft performance and weight control.
wabigail replied the topic: Takeoff and Landing P Charts
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)
Qfly replied the topic: Takeoff and Landing P Charts
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;
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.