Performance calculations: One manufacturer’s approach
Although older jets use a blizzard of paper charts and tables to calculate performance, newer models take advantage of technology to provide more precise and versatile data. Embraer, for example, provides three ways to perform takeoff performance calculations for the new Phenom 100. One is to use the Simplified Takeoff Analysis paper charts in the Airplane Flight Manual. It may seem like a throwback; however, the charts provide much more precise data than older types. This may be the easiest method for many.
To begin, locate the page for the correct takeoff pressure altitude, flap setting, and anti-ice condition. Let’s practice by looking up the takeoff performance data for a takeoff from Van Nuys, California (VNY), at a temperature of 35 degrees Celsius/95 degrees Fahrenheit, and a weight of 10,470 pounds. Van Nuys’ elevation is 803 feet msl, so let’s locate the page for a 1,000-foot pressure altitude, flaps one, dry runway, and anti-ice off.
Next, find our weight of 10,470 pounds at the top of the table and move your finger down that column until you reach the row for 35 degrees Celsius. You’ll see that our takeoff runway required is 4,980 feet and our V1, VR, and V2 are 106, 106, and 107 knots, respectively. At the bottom of the column you’ll see that our VFS (the speed where the aircraft will fly with flaps up) is 129 knots. The climb limit weight is located in the far right column for each temperature row. In this case, it’s 10,470, the maximum certificated takeoff weight for the Phenom 100.
Other methods for computing takeoff data use Embraer software applications. Embraer certified the Phenom 100 using a takeoff performance calculation method unique among light jets. This certified data is contained in software called the Optimized PERformance Analyzer, or OPERA. This software is a part of the AFM and is provided on a CD-ROM.
The OPERA software allows pilots to input a large number of variables to determine the precise performance that can be expected from the airplane. These variables include such basics as weight, temperature, and runway length, as well as more detailed considerations such as anti-ice On or Off, runway slope, runway contamination, obstacles in the takeoff path, desired second-segment level-off height, and automatic thrust reserve (ATR) On or Off. ATR automatically boosts thrust on the operating engine after an engine failure. The OPERA system is very sophisticated, but it’s as complex as it is capable. So to make calculating takeoff performance simpler, Embraer developed easy-dispatch software, or EDS, which provides a much friendlier graphical user interface and simpler outputs.
Embraer includes in the AFM some selected takeoff performance data in paper form. These Simplified Takeoff Analysis charts, like the one we used to calculate our performance departing Van Nuys, will do the job under most conditions, but do not necessarily allow optimum aircraft performance.
These charts are provided in the AFM only for limited conditions and are all based upon ATR Off, which limits second-segment climb and climb-limited takeoff weight compared to takeoffs made with ATR On. The climb-limited takeoff weight is the maximum weight under which the standard Part 25 2.4-percent gross second-segment climb gradient can be met. Departure procedures (DPs) often require a much greater climb gradient and this performance can only be calculated by using OPERA or EDS.
Ben Marcus is co-founder and CEO of jetAVIVA, a light jet sales and acquisition specialist firm. He is an ATP and CFI with single -pilot jet type ratings in the Citation 500 series, Citation Mustang, and Embraer Phenom 100.