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Calculating Weight from Linear P Charts p3.19 Q4

  • brook
  • Topic Author

brook created the topic: Calculating Weight from Linear P Charts p3.19 Q4

Hi Bob and Richard,

Just a quick one on Linear P -Charts:

On page 3.19 of the Issue 6 Performance book, question 4 asks:

Find the Maximum Take off Weight permitted under the following circumstances:
TODA 950m
short dry grass
2% up
15 kt headwind
6000 ft Pressure Height
Temp +20 deg c

The available Answers are:
a) 810 kg (closest to the answer I got)
b) 700kg
c) 750 kg (the actual answer)
d) 730 kg

I have attached a scan of the chart which I draw out the line from the main body of the chart and intersect it with the specified runway length of 950m. Unless I am mistaken (and I could be) it would appear that the line of 2 deg slope and 15 kt headwind intersects the 950m TODA, it brings me to 810 KG, but the answer is less with 750 KG.

(if I examine the climb weight limit by extending the PH of 6000ft then I get a climb weight limit of 990 kg, but thats OK because 810kg and 750kg are both below this.

Can someone let me know where I am going wrong from the scan of the page 4 supplement chart?

Thanks

Brook
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  • Richard

Richard replied the topic: Calculating Weight from Linear P Charts p3.19 Q4

Hi Brook,

The chart is a bit tricky to read but I wonder, are you using the charts out of the old supplement? If not, here is a copy for downloading and printing out: www.bobtait.com.au/images/stories/bobtai...-PERF_Supplement.pdf

Here is my working for the problem:


First off, I get just a nudge over 750kg as the max weight for the take-off. Also the climb weight limit is 960kg (not 990 as you mentioned). Try it again on the newer chart (which is a direct copy of the one you'll get from CASA in the exam) and if it still borks check out my working for it,

Cheers,

Rich
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  • brook
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brook replied the topic: Calculating Weight from Linear P Charts p3.19 Q4

Thanks Richard,

Downloaded the new supplement, did the workings and I too got close to 750KG.

Thanks for that, the book I bought must have had the old supplement in it. Makes me feel better I'm not completely mad!

Brook
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  • Richard

Richard replied the topic: Calculating Weight from Linear P Charts p3.19 Q4

Great, glad it worked out :)

Cheers,

Rich
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