It’s a little more tricky than that. The 777 has Vref based on weight and we are more interested in the landing distance calculation than the speed. The aircraft will happily cope with a small Vref variation due to temperature and altitude.
However, from the landing distance calculation tables you can see the effect of energy on the aircraft derived from height above sea level and temperature!
So, for example, to calculate the landing distance we start with a reference distance for a given weight of 250T (777-300ER) and a set autobrake setting.
e,g, For 250T and Autobrake 3 a reference distance would be approx 2500m.
We then calculate the variables which include:
Weight adjusts for each 5T above and below 250T
Altitude adjusts per 1000’ above MSL
Wind adjusts for each 10kts head or tail wind
Slope adjusts per 1 degree slope + or -
Temperature adjusts for each 10 degrees above or below ISA
Vref adjusts per 5kts above Vref 30
Reverse thrust adjusts.
As you can see above the altitude and temperature factor in here as the energy is taken into account for high altitude airfields. So, for NBO for example, the airfield is 5000’ above AMSL and, from the graph, I have to add 70m per 1000’ so 5 x 70 = 350m for the altitude.
The temperature is, in this case, also +70m per 10 degrees over ISA. So 30 degrees at 5000’ is ISA + 25 (ISA temp ‘should’ be 5 degrees at 5000’) giving 70 x 2.5 = 175m for the temperature.
Therefore, not taking into account any other variables, just for the height and the temperature the corrected landing distance required for the 777-300ER for NBO at 250T is 2500m + 350m + 175m = 3025m required. An ‘extra’ 525m just for the extra energy carried over the threshold.