How Goes it \ PLE charts [Archive]

Chimbu chuckles

2nd Feb 2003, 23:13

LRT it is easy to make your own with some graph paper. Given you're asking I'll assume you don't know how and describe the process...if you do know how sorry but perhaps others reading this may find it informative.

On an A4 graph paper, or in your PC and then print off as many as you want.

X axis - distances from 0 to whatever. 1cm = 100nm
Y axis - Fuel on Board from 0 to full tanks. 1 cm = 100lbs or whatever fuel unit measure you use.

Top right corner a smaller graph with

X axis - GS or TAS. 1 cm /100kts
Y axis - Fuel Flow. 1cm /100pph. Put FFs on both Y axis so you can later draw lbs/gnm or lbs/anm out or home with ease.

You of course need to know your aircraft and on mine in the past I would typically have some notes in the border at top or bottom giving expected TAS/FF for SE cruise/DP cruise etc.

Before departure mark on the Y axis FOB and on the X axis desto distance from departure point. It's also a good idea to mark enroute reporting points/alternates along the X axis at their respective distances along track.

At TOPC note FOB and distance from point of departure, plot it when conveniant.

Plot min FOB required at desto.

Draw a straight line from TOPC plot to desto min FOB plot. This is your max acceptable lbs/gnm.

As you progress along track plot FOB overhead each marked reporting point. This is your actual lbs/gnm.

If actual lbs/gnm line is trending (physically) above max acceptable lbs/gnm line then you are going to arrive at desto with excess fuel over min req'd, if trending below you are not. Draw these lines in with the new (actual) lbs/gnm line originating at the TOPC plot.

To calculate DP/SE PNRs you will need either a parallel rule (navigation ruler used in maritime navigation) or you can use the nice wide Jepp ruler and by drawing marks to keep parallel 'walk' the ruler across the chart.

Plot on the Y axis at point of departure and/or enroute alternates req'd FOB for SE/DP case (remember they have different FR/VR requirements) + of course any weather/traffic holding req'd.

In the small lbs/gnm chart in top rh corner draw a straight line between expected GS and expected FF and while remaining absolutely parallel walk that down 'till the ruler bisects the plot for req'd FOB at departure point or Alt. Draw a line that bisects both the original max allowed lbs/gnm line and the actual lbs/gnm line. Look on the X axis under the intersection point of the two lines and that's your PNR/diversion point.

It's a lot of fun (in an 'old time' Navigator sort of way) and immediately shows in a pictorial way what wind does to your PNRs etc.

Of course with modern FMSs and an electronic calculator you can work all this out in a fraction of the time...but it's a good way to amuse yourself on a long boring sector:D. Actually with practice it's pretty quick.

For maximum amusement handover to your buddy, be he Capt or F/O and engrose yourself in your masterpiece (within the limits of good airmanship of course:D) and fob off their enquiries until you're finished then drop it in their lap with a triumphant grin. Of course some Captains might be mightily pissed with such behaviour so pick your mark if you're an F/O.

Chuck.