9.5 Aircraft Performance in the Real World

What is Aircraft Performance? 

When you shop for a car, one aspect you must consider is the car's performance relative to your needs. You might think about:

• fuel consumption in the city and on the highway

• cargo towing capacity, if you have a trailer 

• acceleration, braking and top speed

In the aviation world, we are concerned with similar elements. But as the plane is operating in three dimensions, and not restricted to the earth's surface, we can argue that aircraft performance is broader and more complex. Consider some of the following aspects of aircraft performance: 

• Payload and fuel capacity 

• Fuel consumption 

• Range and endurance

• Climb and descent capability 

• Cruise performance at various altitudes 

• Speeds: minimums, maximums

• Maximum altitude 

• Landing and takeoff distances

• Atmospheric conditions: air pressure, temperature and humidity 

All of these elements are interrelated, and when it comes to aircraft performance questions, usually the correct answer starts with "it depends..."

It is typical for airlines to have a team of aircraft performance engineers who provide guidance and support on these topics. For example, they may work on problems like:

• managing standard operating procedures

• measuring fleet performance

• economic studies for existing and potential routes

• location-specific studies for challenging airports, for example the Innsbruck Airport in Austrian Alps

Finding Aircraft Performance Data

Aircraft manufacturers publish detailed operating manuals for aircraft purchasers, which include sections about the aircraft's performance figures. In today's world these manuals are typically distributed digitally. Manufacturers like Boeing and Airbus also provide aircraft performance software packages that let operators and engineers interact in more detail with the performance data. For Boeing and Airbus these software packages are called BPS (Boeing Performance Software) and PEP (Performance Engineering Programs) respectively. These programs allow for in-depth studies to be undertaken, including scenario simulations computed from first-principles physics. Since these programs are not available publicly, operators do not expect students to know how to use them. They are taught on-the-job or in specialized training classes in Seattle or Toulouse. 

Another resource for getting performance data is Eurocontrol. Eurocontrol maintains a database called BADA (Base of Aircraft Data). To access it you need to submit an application. From their description:

Aircraft Performance in X-Plane

X-Plane makes physical realism one of its main points in its marketing; however, we have observed in this flight planning project that the operating manual that comes with the default 737-800 does not include any aircraft performance data, except for a few fuel planning pages. It is a generic model; we do not even know which engine version it is supposed to have. I would not necessarily call this a shortcoming. X-Plane 11 ships with 22 aircraft models, and it would be unrealistic to expect X-Plane to be able to provide detailed performance data accurately matched with simulator performance for all these models, without hiking development costs and the retail price of the game. 

So, it may be better to say that X-Plane as a platform takes a physics-based approach, and if you want a high fidelity recreation of a real-world aircraft, you need to purchase a professionally developed payware version of that aircraft.