A Method of Standardizing Takeoff Performance Data Using Modeling and Simulation

Abstract

Existing methods of correcting takeoff distance data to reference conditions rely on analytical or empirical equations that are limited to small incremental corrections for a small number of factors. An alternate method of standardizing takeoff performance data is presented here that uses modeling and simulation to correct for the effects of non-standard ambient air temperature, pressure altitude, wind, runway slope, aircraft gross weight, pilot technique, and numerous other factors. The method uses a two-degree-of-freedom takeoff simulation to calculate corrections to the test-day measured distances and airspeeds at rotation, liftoff, and 50 feet above ground level. Since the simulation is physics-based, it can be used to make large corrections and extrapolations over the full range of conditions for which its component models are valid. The simulation uses models of the aerodynamic, propulsive, and rolling resistance forces that are validated or updated based on flight test results. Two methods of modeling pilot rotation and pitch attitude capture techniques are implemented. Application of the modeling and simulation method is illustrated using flight test data from a four-engine turboprop tactical transport aircraft. Nomenclatureforce coefficient along the flight path [n/d] C y = force coefficient normal to the flight path [n/d] F E = propulsive drag [lb] F G = gross thrust [lb] g = acceleration due to gravity [32.174 ft/sec 2 ] h = geometric altitude [ft] HP = propeller shaft horsepower [hp] i T = thrust line incidence angle [deg] N = propeller speed [rpm] q = incompressible dynamic pressure [lb/ft 2 ] S = reference (wing) area [ft 2 ] S g,std = standardized ground roll distance [ft] S g,test = test-day measured ground roll distance, corrected for wind effects [ft] S g,test,w = test-day measured ground roll distance, uncorrected for wind effects [ft] S level = ground roll distance, corrected to zero-slope runway [ft] S slope = test-day measured ground roll distance, uncorrected for runway slope effects [ft] S std = standardized distance [ft] S′ std = reference-day predicted distance [ft] S test = test-day measured distance [ft] S′ test = test-day predicted distance [ft] t = time [sec] TOLAND = takeoff and landing simulation 1 Aerospace Engineer, 773TS/ENFB, Air Force Flight Test Center. American Institute of Aeronautics and Astronautics 2 V to = ground speed at takeoff [ft/sec] V w = wind speed [ft/sec] W = aircraft gross weight [lb]  = angle of attack [deg]  = density ratio [n/d]  = flight path angle [deg]  slope = runway slope [deg]  = rolling friction coefficient [n/d] std = standard or reference conditions test = test-day measured conditions

A Takeoff Rotation Model Including Pilot Technique Parameters for Flight Test Data Reduction and Expansion

“…A good description of this methodology is provided in Ref. 3. Figure 5 shows a typical takeoff with a comparison between the model (dash lines) and flight test data.…”