CAP 697 Table 2.2.3

OAT is +13ºC, ISA at 8000ft = -1ºC, so Temperature condition is 'ISA +14ºC'

Therefore, we need to interpolate between 'ISA' and 'ISA +20ºC' on the Table

TAS .... this is the same, 160 kts

Fuel flow:

8000ft, ISA, fuel flow 71.1 PPH

8000ft, ISA +20ºC, fuel flow 68.5 PPH

Our condition 'ISA +14ºC', so (71.1-68.5) x (6/20) = .78, so fuel flow = (68.5 + 0.78) = 69.28 PPH