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AFFDL-TR-79-3032 Volume I THE USAF STABILITY AND CONTROL DATCOM Volume I, Users Manual McDonnell Douglas Astronautics Company St. Louis Division St Louis, Missouri 63166 April 1979 Updated by Public Domain Aeronautical Software Santa Cruz CA 95061 December 1999 AIR FORCE FLIGHT DYNAMICS LABORATORY AIR FORCE WRIGHT AERONAUTICAL LABORATORIES AIR FORCE SYSTEMS COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OH 45433 Page 1 of 67

From AFFDL-TR-79-3032 THE USAF STABILITY AND CONTROL DIGITAL DATCOM Volume I, Users Manual SECTION 1 INTRODUCTION In preliminary design operations, rapid and economical estimations of aerodynamic stability and control characteristics are frequently required. The extensive application of complex automated estimation procedures is often prohibitive in terms of time and computer cost in such an environment. Similar inefficiencies accompany hand-calculation procedures, which can require expenditures of significant man-hours, particularly if configuration trade studies are involved, or if estimates are desired over a range of flight conditions. The fundamental purpose of the USAF Stability and Control Datcom is to provide a systematic summary of methods for estimating stability and control characteristics In preliminary design applications. Consistent with this philosophy, the development of the Digital Datcom computer program is an approach to provide rapid and economical estimation of aerodynamic stability and control characteristics. Digital Datcom calculates static stability, high-lift and control device, and dynamic-derivative characteristics using the methods contained in Sections 4 through 7 of Datcom. The computer program also offer a trim option that computes control deflections and aerodynamic data for vehicle trim at subsonic Mach numbers. The program has been developed an a modular basis as illustrated in Figure 1. These modules correspond to the primary building blocks referenced in the program executive. The modular approach was used because it simplified program development, testing, and modification or expansion. This report is the User's Manual for the USAF Stability and Control Digital Datcom. Potential users are directed to Section 2 for an overview of program capabilities. Section 3 provides input definitions, with basic configuration geometry modeling techniques presented in Section 4. Analyses of special configurations are treated in Section 5. Section 6 discusses the available output Page 2 of 67

data. The appendices discuss namelist coding rules, airfoil section characteristic estimation methods with supplemental data, and a list of geometric and aerodynamic variables available as supplemental output. A self-contained user's kit is included to aid the user in setting up inputs to the program. Even though the development of Digital Datcom was pursued with the sole objective of translating the Datcom methods into an efficient, user-oriented computer program, differences between Datcom and Digital Datcom do exist. Such is the primary subject of Volume II, Implementation of Datcom Methods, which contains the correspondence between Datcom methods and program formulation. This volume also defines the program implementation requirements. The listing of the computer program is contained on microfiche as a supplement to this report. Modifications, extensions, and limitations of Datcom methods as incorporated in Digital Datcom are discussed throughout the report. Users should refer to Datcom for the limitations of methods involved. However, potential users are forewarned that Datcom drag methods are not recommended for performance. Where more than one Datcom method exists, Volume II indicates which method or methods are employed in Digita1 Datcom. Direct all program inquiries to AFFDL FGC, Wright-Patterson Air Force Base, OH 45433; phone (513) 255-4315. Page 3 of 67

MASTER ROUTINES Main Programs Executive Subroutines Utility Subroutines METHOD MODULES Performs the executive functions of organizing and directing the operations performed by other program components. Performs user-oriented non-method operations such as ordering input data, logic switching, input error analysis, and output format selection. Performs standard mathematical tasks repetitively performed by method subroutines. SUBSONIC TRANSONIC SUPERSONIC MODULE 1 CHARACTERISTICS AT ANGLE OF ATTACK MODULE 3 CHARACTERISTICS AT ANGLE OF ATTACK MODULE 5 CHARACTERISTICS AT ANGLE OF ATTACK MODULE 2 CHARACTERISTICS IN SIDESLIP MODULE 4 CHARACTERISTICS IN SIDESLIP MODULE 6 CHARACTERISTICS IN SIDESLIP MODULE 10 DYNAMIC DERIVATIVES MODULE 11 HIGH LIFT AND CONTROL DEVICES MODULE 7 TRIM OPTION SPECIAL CONFIGURATIONS MODULE 7 LOW ASPECT RATIO WING-BODY AT SUBSONIC SPEEDS MODULE 8 AERODYNAMIC CONTROL EFFECTIVENESS AT HYPERSONIC SPEEDS MODULE 9 TRAVERSE-JET CONTROL EFFECTIVENESS AT HYPERSONIC SPEEDS FIGURE 1 - DIGITAL DATCOM MODULES Page 4 of 67

SECTION 2 PROGRAM CAPABILITIES This section has been prepared to assist the potential user in his decision process concerning the applicability of the USAF Stability and Control Digital Datcom to his particular requirements. For specific questions dealing with method validity and limitations, the user is strongly encouraged to refer to the USAF Stability and Control Datcom document. Much of the flexibility inherent in the Datcom methods has been retained by allowing the user to substitute experimental or refined analytical data at intermediate computation levels. Extrapolations beyond the normal range of the Datcom methods are provided by the program; however, each time an extrapolation is employed, a message is printed which identifies the point at which the extrapolation is made and the results of the extrapolation. Supplemental output is available via the “dump” and “partial output” options which give the user access to key intermediate parameters to aid verification or adjustment of computations. The following paragraphs discuss primary program capabilities as well as selected qualifiers and limitations. 2.1 ADDRESSABLE CONFIGURATIONS In general, Datcom treats the traditional body-wing-tail geometries including control effectiveness for a variety of high-lift /control devices. High-lift/control output is generally in terms of the incremental effects due to deflection. The user must integrate these incremental effects with the “basic” configuration output. Certain Datcom methods applicable to reentry type vehicles are also available. Therefore, the Digital Datcom addressable geometries include the “basic” traditional aircraft concepts (including canard configurations), and unique geometries which are identified as “special” configurations. Table 1 summarizes the addressable configurations accommodated by the program. Page 5 of 67

CONFIGURATION PROGRAM REMARKS BODY WING, HORIZONTAL TAIL PRIMARILY BODIES OF REVOLUTION, OR CLOSE APPROXIMATIONS, ARE TREATED. TRANSONIC METHODS FOR MOST OF THE AERODYNAMIC DATA DO NOT EXIST. THE RECOMMENDED PROCEDURE REQUIRES FAIRING BETWEEN SUBSONIC AND SUPERSONIC DATA USING AVAILABLE DATA AS A GUIDE. STRAIGHT TAPERED, CRANKED, OR DOUBLE DELTA PLANFORMS ARE TREATED. EFFECTS OF SWEEP, TAPER AND INCIDENCE ARE INCLUDED. LINEAR TWIST IS TREATED AT SUBSONIC MACH NUMBERS. DIHEDRAL EFFECTS ARE PRESENT IN THE LATERAL DIRECTIONAL DATA. BODY-WING BODY- HORIZONTAL LONGITUDINAL METHODS REFLECT ONLY A MID-WING POSITION. LATERAL DIRECTIONAL SOLUTIONS CONSIDER HIGH AND LOW-WING POSITIONS. WING-BODY-TAIL NON-STANDARD GEOMETRIES THE VARIOUS GEOMETRY COMBINATIONS ARE GIVEN IN TABLE 2. WING DOWNWASH METHODS ARE RESTRICTED TO STRAIGHT TAPERED PLANFORMS. EFFECTS OF TWIN VERTICAL TAILS ARE INCLUDED IN THE STATIC LATERAL DIRECTIONAL DATA AT SUBSONIC MACH NUMBERS. NON-STANDARD CONFIGURATIONS ARE SIMULATED USING “BASIC” CONFIGURATION TECHNIQUES. STRAKES CAN BE RUN VIA A DOUBLE- DELTA WING. A BODY-CANARD-WING IS INPUT AS A WING-BODY- HORIZONTAL TAIL. THE FORWARD LIFTING SURFACE IS INPUT AS A WING AND THE AFT SURFACE AS A HORIZONTAL TAIL. SPECIAL CONFIGURATIONS LOW ASPECT RATIO WING OR WING-BODY CONFIGURATIONS (LIFTING BODIES) ARE TREATED AT SUBSONIC SPEEDS. TWO- DIMENSIONAL FLAP AND TRANSVERSE JET EFFECTS ARE ALSO TREATED AT HYPERSONIC SPEEDS. TABLE 1 - ADDRESSABLE CONFIGURATIONS Page 6 of 67

2.2 BASIC CONFIGURATION DATA The capabilities discussed below apply to basic configurations, i.e., traditional body-wing-tail concepts. A detailed summary of output as a function of configuration and speed regime is presented in Table 2. Note that transonic output can be expanded through the use of data substitution (Sections 3.2 and 4.5). Typical output for these configurations are presented in section 6. 2.2.1 Static Stability Characteristics The longitudinal and lateral-directional stability characteristics provided by the Datcom and the Digital Datcom are in the stability-axis system. Body-axis normal- force and axial-force coefficients are also included in the output for convenience of the user. For those speed regimes and configurations where Datcom methods are available, the Digital Datcom output provides the longitudinal coefficients CD, CL, Cm, CN, and CA, and the derivatives C L α , C m α , C , C , C l β n β Y β Output for configurations with a wing and horizontal tail also includes downwash and the local dynamic-pressure ratio in the region of the tail. Subsonic data that include propeller power, jet power, or ground effects are also available. Power and ground effects are limited to the longitudinal aerodynamic characteristics. Users are cautioned that the Datcom does not rigorously treat aerodynamics in the transonic speed regime, and a fairing between subsonic and supersonic solutions is often the recommended procedure. Digital Datcom uses linear and nonlinear fairings through specific points; however, the user may find another fairing more acceptable. The details of these fairing techniques are discussed in Volume II, Section 4. The partial output option, discussed in Section 3.5, permits the user to obtain the information necessary for transonic fairings. The experimental data input option allows the user to revise the transonic fairings on configuration components, perform parametric analyses on test configurations, and apply better method results (or data) for configuration build-up. Datcom body aerodynamic characteristics can be obtained at all Mach numbers only for bodies of revolution. Digital Datcom can also provide subsonic longitudinal data for cambered bodies of arbitrary cross section as shown in Figure 6. The cambered body capability is restricted to subsonic longitudinal-stability solutions. Straight-tapered and nonstraight-tapered wings including effects of sweep, taper, and incidence can be treated by the program. The effect of linear twist can be treated at subsonic Mach numbers. Dihedral influences are included in lateral- Page 8 of 67

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