Hey Clarrie,
What are the critical OATs for departure 35 for the A and C engines?
A rough look at the BoM max temps for the last 5 years for CBR airport for January shows a monthly mean of 30.3C with a standard deviation of 4.7C, based on 153 daily observations showing a range of max OAT of 23.4C, the highest being 42.0C. The distribution is a reasonably symmetrical approximation of the normal distribution, so even Alan's mathematical genii in Route Planning can easily calculate the probability of a particular temperature occurring during that month. For a slightly bigger bonus, they could probably develop a correlation estimate between the new airport data and the old airport data (kept from 1939 to 2010) and work it out on a daily basis to match the traffic data.
For a huge bonus, they could even talk to Yield about providing a daily seat limit, making it easier for the boys to manage the variations on the day.
Now, getting back to the troll's original bait, the cost of power by the hour for a 21K engine compared to an 18.5K engine is eye-wateringly disproportionate for the number of take-offs required above 18.5K. Let's just say you need 21K for 30 departures but the rest (say 120) are at maximum derate of around 15-16K: you pay for every minute of time in service as if you are spinning the fan off the front at max TGT through the emergency gate.
Would I assess the probabilities of getting away with 18.5K engines
or would I just pay through the nose for 21K and look at it after 3 months?
Farm Gate,
Anybody limiting TOW to maintain OEI SID compliance at CBR either had big expensive engines or doesn't grasp the benefits of Special Departure Procedures...
Neville N,
I didn't realise that IATA had taken over from the ACCC in protecting consumers...
Stay Alive,