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Does anyone know how to figure in the altitude lines on the GIV Twin Engine Plight Planning Chart? I can't see how that line intersects with another line.

https://imgur.com/a/e2UOr3z

Thank you...

Are you talking about "max initial FL" lines?
Think about them as constant take-off weight lines. upper left border says "max initial FL410 @ MTOW (74.5klb). Sample plotted situation of 49klb landing + 19 klb fuel burn = 68klb TOW allows climb to FL410 (line to the left of planning point) but not to FL430, where you need to be no more than ~65.5 klb TOW.
Probably some optimal climb profile is assumed, and cruise weight is lower than TOW numbers apparently.

I don’t get how you determine 68klb TO weight? I have to be missing something.

rfresh737 wrote:

I don’t get how you determine 68klb TO weight? I have to be missing something.

They plot for 49 klb landing weight, and get 19 klb fuel burn for whatever flight distance they solve for.
49+19=68

I got it...I kept reading your first answer and the light bulb finally went off...thanks for the help...!!!

So this is what I ended up with. Line #7 (blue line) representing the flight level line.

https://imgur.com/Bk0ieFq

rfresh737 wrote:

So this is what I ended up with. Line #7 (blue line) representing the flight level line.

https://imgur.com/Bk0ieFq

THat is perfectly correct.
I would put it a bit differently, though - this line represents TOW, and hence maximum FL you can climb right after takeoff. Same thing, just a bit different perspective.
I wonder if there is a table of weight vs maximum FL somewhere in the book.

Got it…thanks for the clarification!!!

kalvado wrote:

rfresh737 wrote:

So this is what I ended up with. Line #7 (blue line) representing the flight level line.

https://imgur.com/Bk0ieFq

THat is perfectly correct.
I would put it a bit differently, though - this line represents TOW, and hence maximum FL you can climb right after takeoff. Same thing, just a bit different perspective.
I wonder if there is a table of weight vs maximum FL somewhere in the book.

There should be one showing step climb weights as fuel burns off and known conditions. This charts is for ISA at FL, there should be charts for different temps at FL, too.

OK, so in this screen shot, landing weight of 50 + 11000 fuel burn == 61000 TOW. Blue line is laid over 61000 and this tells me I can just make it to FL430 but not FL450?

https://imgur.com/SmpIw5Z

Correct

rfresh737 wrote:

OK, so in this screen shot, landing weight of 50 + 11000 fuel burn == 61000 TOW. Blue line is laid over 61000 and this tells me I can just make it to FL430 but not FL450?

https://imgur.com/SmpIw5Z

Correct. Well, at least initially you are limited to 430. As @GalaxyFlyer said, you should be able to step climb as you burn off fuel.

I think I don't need my blue line #7. All I need to do is just look into what area that cyan landing weight vertica line is crossing that red line. Just looking at what area those lines cross will tell me what initial FL I can do. As for the TOW that is just calculated by adding the landing weight to the fuel burn rate in my head.

Thank you...

Sort of a useless chart, have to go elsewhere to find trip fuel, find alternate and holding fuel. Once you know those inputs, the chart gives you initial FL. Big Whoop! But, it’s 30+ years old.

GalaxyFlyer wrote:

Sort of a useless chart, have to go elsewhere to find trip fuel, find alternate and holding fuel. Once you know those inputs, the chart gives you initial FL. Big Whoop! But, it’s 30+ years old.

There is clearly a bit more to this chart.
Purple line coming from another chart at right-bottom should represent either travel distance or airborne time. Looks like some graphic calculation is done there as well.
From there you choose landing weight ( empty + payload + reserves, all more or less known) and can calculate - well, estimate - trip fuel. Oh, and by the way this is your TOW, and you file FL430 initial altitude.