performance question

[gphillips134]

an aircraft is scheduled for take off, and requires 800m (TODR) under normal conditions at sea level. The following airfield characteristics need to be taken into account:Pressure altitude 2000ft QNH 1013 HPa Temp +21C, 5kt tailwind, 2% upslope, adjust the TODR accordingly using the following factors:

pressure alt +/- 20m / 1000ft
Runway slope +/- 15m/ 1% slope
Headwind -5m / 1kt
Tailwind + 10m / 1kt
temp +/- 5m / 1 degree ISA deviation


explaination would be helpful, cheers

[Lewy Boy]

All you do is add on the effect of each condition i.e

TODR=800m
PA=+40m (20m/1000ft and high elevation increases TO run)
Slope=+30m(15m/1% and upslope will increase distance)
Wind=+50m(10m/1kt and tailwind increases TO run)
Temp=+50m(ISA at 2000ft is 11.04c example is 21c so ISA+10.Warmer air increases distance again)

Hopefully the answer is around 970m. I had a few of these in my performance exam and passed it so hopefully this is the correct method.

Good luck

[FlyingForFun]

I believe you are actually supposed to multiply the effects, not add them......? They are "normally" expressed in terms of a %age addition to the distances required, though, not an absolute value, so not sure how you'd do that in this case. Possibly convert each individual value to a %age, then multiply the %ages together???

FFF
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[peb]

Im agree with you, I think that is the right answer. 970 meters

[gphillips134]

well done to the first responce the answer was indeed correct not to difficult once someone has taken five minutes to show you how its done

thanks again