1、NASA TECHNICAL NOTE NASA TN D-6575 Ln h m 4 a SUMMARY OF SPIN TECHNOLOGY AS RELATED TO LIGHT I GENERAL-AVIATION AIRPLANES I by James S. Bowman, Jre Langley Research Center Hampton, Va* 23365 I NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. DECEMBER 1971 Provided by IHSNot for Resale
2、No reproduction or networking permitted without license from IHS-,-,-CONTENTS L Page SUMMARY . 1 INTRODUCTION . 1 SYMBOLS . 2 THESPIN . 3 SIGNIFICANT FACTORS . 4 Mass Distribution 5 Relative Density . 6 Tail Configuration 7 Criterion for spin recovery . 7 Rudder effectiveness . 10 Elevator effective
3、ness 11 Antispin fillets 12 Ventral and dorsal fins 12 External Wing Tanks 13 Aerodynamic effects . 13 Mass effects . 13 13 Wing Trailing-Edge Flaps and Landing Gear Wing Position 14 TailLength . 14 Center-of -Gravity Position . 15 Power 15 CONCLUSIONS . 16 REFERENCES . 18 FIGURES 20 iii Provided by
4、 IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARY OF SPIN TECHNOLOGY AS RELATED TO LIGHT GENERAL -AVIATION AIRPLANES By James S. Bowman, Jr. Langley Research Center SUMMARY A summary has been made of all NASA (and NACA) research and experience related to
5、the spin and recovery characteristics of light personal-owner-type general-aviation airplanes. Very little of the research deals with light general-aviation airplanes as such, but many of the airplanes and models tested before and during World War I1 were similar to present-day light general-aviatio
6、n airplanes with regard to the factors that are impor- tant in spinning. The present paper is based mainly on the results of spin-tunnel tests of free -spinning dynamically scaled models of about 100 different airplane designs and, whenever possible, includes correlation with full-scale spin tests.
7、The research results are discussed in terms of airplane design considerations and the proper use of controls for recovery. Three factors are found to be of almost overriding importance in spinning for this type of airplane. These factors are the relative distribution of the mass between the wing and
8、 fuselage, the density of the airplane relative to that of the air, and the tail design. The mass distribution and relative density determine the tail-design requirements and the control movements required for recovery, An empirically determined design factor is available as a guide for the design o
9、f the tail to insure good spin recovery. The rud- der is generally regarded as the primary recovery control. The elevator can be very effective in some cases, such as positive (wing-heavy) loadings or recovery during the incipient spin, but it might prove to be ineffective for fully developed spins,
10、 flat spins, or cases in which the mass distribution or center-of -gravity position has been changed. INTRODUCTION The technology of spinning seems to receive little attention from most people asso- ciated with airplanes - from design to operation - because it is not a normal part of the operation o
11、f most airplanes. Most general-aviation airplanes are no longer required to be able to recover from a fully developed spin (ref. l), and spin training is no longer required for a private pilots license. These factors, and many more, have led to a gen- eral lack of understanding of the basic principl
12、es of spinning. Consequently, a crisis Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-usually develops when a new design is involved in a spin crash or when an old design has a series of spin accidents. In either case, the design is usually so fixed
13、 that the optimum design change to improve the spin-recovery characteristics involves so much time and money that it is ruled out in favor of a minimum, less expensive modification which is less desirable. The purpose of the present paper is to summarize findings of the NASA (and NACA) research that
14、 relates to the spinning of general-aviation aircraft. This summary is intended to be sufficiently detailed to help the designer build safer airplanes by giving adequate treatment to spin recovery early in the design stage, and yet sufficiently gen- eral to help pilots and operators have a better un
15、derstanding of spinning so that they may better cope with spin problems that occur with their airplanes. Most of the applicable research was performed before and during World War I1 and was not performed on general-aviation airplanes as such, but many of the airplanes and models tested during this p
16、eriod were similar to present-day general-aviation airplanes with regard to factors that are important in spinning. From these tests the effects of many pertinent design features were determined. This work is analyzed herein with regard to present-day light general-aviation airplanes and is updated
17、with more recent spin experience applicable to this class of airplane, practically all of which is fragmentary and unpublished. The class of airplane toward which this summary report is directed is the personal-owner aircraft of less than about 1800 kg (4000 pounds) gross weight. The analysis is mad
18、e, however, in terms of nondimensional parameters so that it may be more broadly applicable. SYMBOLS b F IXJY Ix - IY mb2 L L1 2 wing span, m (ft) force, N (lb) moments of inertia about X- and Y-axis, respectively, kg-mz (slug-ft2) inertia yawing-moment parameter distance from center of gravity of a
19、irplane to centroid of fuselage area SF, m (ft) distance from center of gravity of airplane to centroid of rudder area SR1, * (ft) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-L2 m R S I SF R1 sR2 TDPF TDR URVC W cy distance from center of gravity
20、 of airplane to centroid of rudder area sR2, (ft) airplane mass, kg (slugs) spin radius, m (ft) wing area, m2 (ft2) fuselage side area under horizontal tail, m2 (ft2) unshielded rudder area above horizontal tail, m2 (ft2) unshielded rudder area below horizontal tail, m2 (ft2) tail-damping power fact
21、or tail-damping ratio unshielded - rudde r volume coefficient weight, kg (lb) longitudinal, lateral, and vertical body axis of airplane, respectively angle of attack, deg relative-density factor, m/pSb air density, kg/m3 (slugs/ft3) angle between Y body axis and horizontal measured in vertical plane
22、, positive when right wing is down for erect spins, deg airplane spin rate, turns/sec THE SPIN The spin has been defined as a motion in which an airplane in flight at some angle of attack between the stall and 900 descends rapidly towards the earth while rotating about 3 Provided by IHSNot for Resal
23、eNo reproduction or networking permitted without license from IHS-,-,-a vertical axis. (See ref. 2.) The spinning motion is very complicated and involves simultaneous rolling, yawing, and pitching while the airplane is at high angles of attack and sideslip. Since it involves separated flows in the r
24、egion beyond the stall, the aero- dynamic characteristics of the airplane are very nonlinear and time dependent; and hence, at the present time, the spin is not very amenable to theoretical analyses. The overall spin maneuver can be considered to consist of three phases: the incip- ient spin, the de
25、veloped spin, and the recovery. An illustration of the various phases of the spinning motion is given in figure 1. The incipient spin occurs from the time the airplane stalls and rotation starts until the spin axis becomes vertical or nearly vertical. During this time the airplane flight path is cha
26、nging from horizontal to vertical, and the spin rotation is increasing from zero to the fully developed spin rate. The incipient spin usually occurs rapidly for light airplanes (4 to 6 seconds, approximately) and consists of approximately the first two turns. As indicated by full-scale tests and by
27、the model tests of reference 3, the typical incipient-spin motion starts during the stall with a roll-off. Then, as the nose drops, the yawing motion begins to build up. About the half-turn point, the airplane is pointed almost straight down but the angle of attack is usually above that of the stall
28、 because of the inclined flight path. (See fig. 1.) As the one-turn point is approached, the nose comes back up and the angle of attack continues to increase. As the airplane continues to rotate into the second turn, the flight path becomes more nearly vertical, and the pitching, rolling, and yawing
29、 motions become more repeatable and approach those of the fully developed spin. In the developed spin the attitude, angles, and motions of the airplane are some- what repeatable from turn to turn, and the flight path is approximately vertical. The spin is maintained by a balance between the aerodyna
30、mic and inertia forces and moments. The spinning motion is made up of rotation about the airplane center of gravity plus trans- latory motion of the center of gravity; however, it is primarily a rotary motion and is affected mainly by the moments acting on it. A typical example of an airplane spinni
31、ng motion and the forces in a spin is illustrated in figure 2. The third phase, the recovery, is caused by a change in the moments so as to upset the balance between the aerodynamic and inertia moments. Such a change in the moments is obtained by deflecting the controls of the airplane. The specific
32、 control movements required in any particular airplane depend on certain mass and aerodynamic characteris- tics, which are discussed in the subsequent sections of this paper. SIGNIFICANT FACTORS Reference 2 is a summary paper in which many of the factors that affect spin and recovery are discussed.
33、It affords much useful background information which is of 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-interest with regard to the present problem, but it is oriented mainly toward modern high- performance military airplanes. The present paper,
34、on the other hand, identifies and discusses the factors that are of particular significance with regard to the light airplane. The picture that will evolve in the discussion is that three principal factors are of almost overriding importance in the spinning of light general-aviation airplanes: the r
35、elative distribution of the mass of the airplane between the wing and fuselage, the den- plane. The relative density is generally fixed by performance considerations and cannot be accommodated to spin requirements. Of the other two factors, mass distribution is very important because it determines t
36、he control movements required for recovery and together with the relative density, it determines the tail-design requirements for recov- ery. The tail design is important because it must have certain features to provide the aerodynamic moments required for recovery and to damp the spinning rotation
37、and also because it is the factor that can most easily be controlled by the designer, particularly in the latter stages of the design and development of the airplane. . 1 sity of the airplane relative to the density of the air, and the tail configuration of the air- P I Mass Distribution The way in
38、which the mass of an airplane is distributed between the wing and fuse- lage is the most important single factor in spinning because it determines the way in which the airplane, while spinning, responds to control movements, especially to eleva- tors and ailerons. An airplane rotating in a spin can
39、be considered to be a large gyro- scope. Since there are mass and angular rotation about all three axes, inertia moments are produced about all three axes. In addition, aerodynamic forces and moments are moments are opposite in sign to the aerodynamic forces and moments and are both equal and opposi
40、te for an equilibrium spin condition. An example of the aerodynamic and iner- tia moments balanced in pitch is illustrated in figure 3. Perhaps the clearest example of this balance is that for a wing-level spin, the nose-down aerodynamic pitching moment must be exactly balanced by the nose-up inerti
41、a pitching moment. In order for the air- plane to recover from the spin, the equilibrium must be broken, and this is normally accomplished by changing the aerodynamic moment by moving a control or combination of controls that can cause the greatest antispin moment. I I I I acting on the airplane bec
42、ause of its motion through the air. The inertia forces and I i The mass distribution of all airplanes (general aviation, military fighters, bombers, etc.) can be grouped into three general loading categories, as shown in figure 4. The - - mass distribution of the airplane is evaluated in terms of th
43、e parameter lx - r) lY, which mbL has been found to be a normalizing factor and which is nondimensional so that it is inde- pendent of the size and weight of the airplane. This parameter is important in deter- mining the inertia yawing moment, which is a controlling factor in a spin, and is 5 Provid
44、ed by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-commonly called the inertia yawing-moment parameter. When the weight of the airplane is distributed mainly along the wing, the moment of inertia in roll is greater than that in pitch, and the value of this ma
45、ss-distribution parameter is positive. This situation is referred to as a positive or wing-heavy loading, and features such as wing-mounted engines and tip tanks contribute to such a loading. Conversely, when the weight of the airplane is distributed mainly along the fuselage, the moment of inertia
46、in pitch is greater than that in roll, and the value of the mass-distribution parameter is negative. This situ- ation is referred to as a negative or fuselage-heavy loading, and features such as fuselage- located engines, fuel, luggage, and cargo contribute to such a loading. Almost all light genera
47、l-aviation airplanes actually fall into the zero loading category of figure 4, where the moments of inertia in roll and pitch are about equal. However, there are some excep- tions, especially when heavy tip tanks are installed on the wings. The zero loading range is generally considered to be the ra
48、nge between values of -50 X and 50 X for the inertia yawing-moment parameter. When the difference between the rolling and pitching moments of inertia is this small, the inertias contribute little, or nothing, to the recovery. The loading of the airplane dictates the control movements required for re
49、covery. (See refs. 2 and 4 to 7.) Deflection of the rudder to oppose the spinning rotation directly is always recommended, but in many cases, it is not adequate to provide recovery. For the wing-heavy loadings, down elevator is the primary recovery control. For fuselage- heavy loadings, the aileron is the primary recovery control; the aileron should be deflected with the spin, for example
