Comparing performance when evaluating aircraft

Lack of accuracy or simply wrong data sources can distort airlines understanding of the evaluated aircraft performance

Too often, in the frame of aircraft evaluations, the way aircraft performance is analyzed can lead to comparing apples and oranges. As usual in the aviation business, the devil is in the details.

Third-party service providers specializing in operational performance calculations can report aircraft performance data. The service provided is very good for daily operations, but rarelyensures correct comparisons when it comes to assessing performance for new aircraft. This simply comes from the fact that upcoming aircraft improvements or standards are not yet considered in their data, or that aircraft represented in their database are not always consistent in terms of weight, cabin layout, age, etc., (because it usually represents specific in-service aircraft).

When aircraft performance data is provided by an OEM, the source of data is the most reliable for aircraft evaluations; however, great attention should still be paid to the set of assumptions used as small deviations can greatly distort results. Here are some examples of the fuel burn sensitivity of some assumptions applied to the same aircraft:

- the impact of using 800nm instead of 500nm for the average sector can result in a 3% fuel burn delta per block hour
- moving from 70% to 85% load factor leads to some 3% additional fuel burn delta
- using 85% reliability winds instead of average winds (50%) equals another 2-2.5% fuel burn delta
- the impact of one tonne on the OWE on a single-aisle can affect fuel burn by another 0.7-1%

And all these can cumulate!

Also, the less the aircraft burns fuel, the greater the impact of these assumptions.

To obtain an apple-to-apple comparison, it is therefore essential to precisely define the cabin configuration and the resulting weight breakdown of an aircraft, as well as all the key parameters of the flight profile.The same thorough approach is required when assessing the economics of an aircraft, and in particular in the maintenance cost domain where each assumption can tangibly affect the calculated projections.

As said, the aviation devil lives in the details…

For more information contact:
Patrick Baudis
Vice President Marketing, Latin America & Caribbean
patrick.baudis@airbus.com