An Introduction to Aircraft Performance Group

Welcome back to Jump Seat. Today, we’d like to focus on Aircraft Performance Group, or APG. Through our partnership with them, we provide weight and balance and takeoff/landing performance including runway analysis calculations within the ARINCDirect tools.

The critical calculation of determining maximum takeoff weights can be frequently misunderstood. Fortunately, APG's analysis accounts for the characteristics of the runway, surrounding terrain and obstructions, the performance capabilities of the aircraft, and the expected meteorological conditions at the time of departure. This leads to rapid, accessible, and accurate data, optimizes flight safety, and prevents errors. 

Runway and Terrain 

All APG runway analysis calculations account for the expected takeoff flight path while considering each individual obstruction in conjunction with a world-wide terrain database. It is necessary to consider items like acceleration altitude, takeoff thrust time limits, and distant terrain beyond the coverage of the survey.

Official governmental sources determine all information on declared distances, surface type, runway slope, and surveyed obstacles. For airfields within the FAA area of responsibility, these include the NOAA Obstruction Chart, FAA Form 5010, Digital Obstacle File, and the NOS Enroute Supplement. For areas outside of the FAA's responsibility, the sources include the ICAO Airport Characteristics Data Bank, AIP Type A/B Charts, AD 2.10, ENR 5.4, and the NOS Enroute Supplement. Terrain data is determined from the NASA SRTM (Shuttle Radar Topography Mission) Digital Elevation Model dataset. 

These data sources are the first input in determining the expected flight path. Special Engine Out Departure Procedures (EOPs) are developed to optimize a flight path over the lowest terrain while minimizing the pilot workload. EOPs are designed to follow the intended ground path of a normal operation, such as a SID or MAP. By aligning these ground tracks, risk and confusion are reduced should an engine failure occur during the takeoff climb.   

V2 climb speeds for the aircraft also affect the expected ground track due to differences in turn radii; particularly for fly-over and turn-to-heading legs. To account for these variations, the Obstacle Accountability Area (OAA) is developed to account for multiple climb speeds. By modeling climb speeds applicable for low-speed turbo-propeller aircraft to high-speed regional jets, it's assured the ground track for any climb speed is covered by the superset OAA.  

Aircraft Performance Capabilities 

Once the ground track OAA and relevant terrain and obstacles are determined, the certified aircraft performance data is used to determine the takeoff limit weight. This data is typically derived from the published AFM (Airplane Flight Manual) or SCAP (Standard Computerized Airplane Performance) software.  

The runway analysis solution first considers certified limits such as brake energy, tire speed, and climb limits. Then, using the takeoff distance data and the climb data, the maximum weight is determined to be the weight that meets all requirements of TORA, TODA, and ASDA, along with the four segment Single Engine Flight Path profile to clear all-terrain and obstacles by the regulatory required margin. When possible and supported by the published data, V1 is optimized to maximize weights while meeting those requirements. Runway surface condition, anti-ice settings, other engine bleeds, and MEL items will also be accounted for, when necessary. 

Figure 1: Performance Calculator on the ARINCDirect iPad Application

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