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## Hard P-Chart questions

• Posts: 35

### jkatz098 created the topic: Hard P-Chart questions

Failed my exam yesterday, and some how got all 4 of my p chart questions wrong. I have no idea how since I measured things to the mm (literally) and have never gotten a p-chart question wrong.

I remember one of the echo landing ones having these results
RWY18 - 2% down, 15kt HW
RWY 36 - 2% up slope, 15kt TW

The winds were given as a forecast so I first determined the runway I should use based on forecast winds. Now obviously RWY 36 would have a tailwind at 15kt which exceeds.

When I plotted on the chart, I used nil wind, however I'm curious with a question like this, because if I had used the winds 15kt hw or 5kt tw (due to being the max) the 5kt tw with an up slope would have given me a shorter landing distance. But the wind was forecast at 15kt tw so it would have been different if it allowed for that on the chart.

The question is, did I go about this question correct and select the runway which is forecast to have a headwind rather than exceeding the tailwind?

• John.Heddles
• Offline
• ATPL/consulting aero engineer
• Posts: 702

### John.Heddles replied the topic: Hard P-Chart questions

I have no idea how

We would need to see specific questions and your specific working to offer useful comments.

I measured things to the mm

What are you measuring to the mm ?

I used to design these DCA format P-charts in another life so I know their ins and outs in quite some detail. There is no reason to be getting out rules to measure things - a ruler (preferably a Douglas protractor) is, however, very necessary for drawing the lines and, certainly, a sharp pencil is a good idea.

RWY18 - 2% down, 15kt HW

R/W appears usable

RWY 36 - 2% up slope, 15kt TW

R/W is not usable due W/C - ignore it for the question.

When I plotted on the chart, I used nil wind

That's appropriate at the planning stage or during flight when you are a significant distance (time) away from the landing. As you approach the destination/alternate, though, if you have a reported wind, then you can use that as is.

But the wind was forecast at 15kt tw so it would have been different if it allowed for that on the chart.

Landing with 15kt T/W is not permitted so it is totally irrelevant to the question's answer. Plenty of aircraft have had the T/W limits increased to 10 kt and, some, 15 kt. Greater T/W limits would be somewhat few and far between. The problems can be both performance and handling driven and would always require certification flight test workup.

Engineering specialist in aircraft performance and weight control.

• Posts: 162

### MissSoph replied the topic: Hard P-Chart questions

Hey jkatz098.... I’m just curious as to why you have not used the winds for the landing charts.?
I would be hazardous to say that if the info given was written as you have above... I would have used the winds... if however it was given to me in the form of say a TAF... then perhaps not... I’m learning quickly... well ok.... slowly.... that there is always a trick to the info provided...