How do i use this performance graph

[MattH150197]

So i have an assignment to plan a flight from Heathrow to Glasgow and I am trying to calculate the time fuel and distance for the inital climb to cruise level and departing the airport, we have been given an aircraft manual and i have found the graph attached however i have calculated the pressure altitude at Heathrow to be -187 feet so how do i use the graph, any ideas? Thanks

 

[mfb]

0 feet and -187 feet are indistinguishable on the scale of the graph, just use 0.

 

[MattH150197]

0 feet and -187 feet are indistinguishable on the scale of the graph, just use 0.

Ah okay i had thought that might be the case but wasnt sure. Thanks very much!

 

[CWatters]

Just for info.. You might care to check out the Professional Pilots forum

http://www.pprune.org

I expect they have a section where tech questions can be asked.