1、NASA TECHNICAL NOTE NASA TN D-7411I-(NASA-TN-D-7411) FREE-FLIGHT N74-21649INVESTIGATION OF THE STABILITY ANDCONTROL CHARACTERISTICS OF A STOL BODELWITH AN EXTERNALLY BLOW1 JET FLAP (NASA) Unclasz-f p HC $4.00 CSCL 01B H1/02 37230FREE-FLIGHT INVESTIGATIONOF THE STABILITY AND CONTROLCHARACTERISTICS OF
2、 A STOL MODELWITH AN EXTERNALLY BLOWN JET FLAPbyLysle P. Parlett and Sandy J. Emerling 1112Langley Research Center 4 -and IArthur E. Phelps III /Langley Directorate, 2 9U.S. Army Air Mobility R and Arthur E. Phelps III, Langley Directorate, L-9148U.S. Army Air Mobility R therear elements, however, w
3、ere pivoted to permit deflections in the range from 300 to 700Symmetric deflection was used, of course, to vary the lift and drag capability of the model,while asymmetric deflection was used to provide a rolling moment to help trim therolling-moment asymmetry present with one engine inoperative. An
4、example of suchasymmetric deflection is illustrated in figure 2 (c) which indicates the asymmetricdeflection used in the flight tests with the left outboard engine inoperative.Longitudinal trim and control moments were provided by an all-movable horizontaltail, on which (1) the elevator was set at a
5、 constant deflection of -500 and (2) a 17-percentleading-edge flap was installed. Lateral moments were provided by a rudder and by aconventional spoiler which could be deflected over the full semispan or, in some tests,only ahead of the outboard segment of the flaps.Blowing systems illustrated in fi
6、gure 2(d) provided boundary-layer control (BLC),when desired, for the wing leading edge, aileron (outboard trailing-edge flap segment),horizontal-tail leading edge, elevator, and rudder. In each of these systems, compressedair flowed from tubes through a row of small, closely spaced holes, then thro
7、ugh slots toform a fairly uniform sheet along the forward surface of the airfoil or control element.The engines used were 15.3-cm-diameter (6-in.) fans driven by compressed air andwere installed at -3o incidence so that the exhaust impinged directly on the flaps. Theengines were equipped with latera
8、l exhaust deflectors for use in trimming the lateralasymmetries in engine-out tests. Figure 2(e) shows a deflector installed on an engine.All tests were made in the 9- by 18-m (30- by 60-ft) open-throat test section of theLangley full-scale tunnel. The static-force tests were made with an internal s
9、train-gagebalance and conventional sting which entered the rear of the fuselage. Photographs of themodel in force-test and flight-test conditions are presented as figures 3(a) and 3(b),respectively.TESTS AND PROCEDURESStatic-Force TestsIn preparation for the tests, engine calibrations were made to d
10、etermine grossthrust as a function of engine rotational speed in the static condition - with the modelflaps off and the engine thrust deflectors off. The tests were then made by setting theengine speed to give the desired gross thrust and holding these settings constant throughthe ranges of angle of
11、 attack or sideslip. It has been shown in the past that the grossthrust of these engines at a constant speed is not affected significantly by forward speedfor the forward speeds involved in the present tests.7Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I
12、HS-,-,-Jet deflection angles and flap turning efficiency were determined from measure-ments of normal and axial forces made in the static-thrust condition with flaps deflected.The static thrust used in computing turning efficiency was taken directly from the enginecalibrations at the appropriate rot
13、ational speed.During the tests, six-component longitudinal and lateral force-test data were meas-ured at several flap deflections (symmetric and asymmetric) through an angle-of-attackrange of from about -50 to 350 at engine gross-thrust coefficients up to 1.1 per enginefor four-engine and three-engi
14、ne operation. Tests were made at various incidences ofthe horizontal tail, at various deflections of spoiler, rudder, ailerons, and thrust deflec-tors, and for various amounts of BLC blowing over aileron, rudder, and wing leadingedge. The jet momentum for each of the blown surfaces was evaluated by
15、measuring theforce produced by the respective jets in the wind-off condition. Tests to determine side-slip aerodynamic stability derivatives were made at sideslip angles of -50 and 50. Wind-on tests were made at free-stream dynamic pressures of 62.2 and 81.4 N/m2 (1.3 and1.7 lb/ft2), which correspon
16、d to velocities of 10.1 and 11.6 m/sec (33 and 38 ft/sec), andReynolds numbers of 0.31 x 106 and 0.36 x 106, respectively. These values of Reynoldsnumbers were approximately in the same range as those of the flight tests which variedfrom 0.24 x 106 to 0.56 x 106.Free- Flight TestsIn the test setup f
17、or the free-flight tests (shown in fig. 4), the model was flownwithout restraint in the 9- by 18-m (30- by 60-ft) open-throat test section of the tunneland was remotely controlled about all three axes by two human pilots. One pilot, locatedin an enclosure at the rear of the test section, controlled
18、the model about its roll and yawaxes while the second pilot, stationed at one side of the test section, controlled the modelin pitch. The model-thrust operator was stationed with the pitch pilot. Compressed air,electric power, and control signals were supplied to the model through a flexible trailin
19、gcable composed of electric wires and lightweight plastic tubes. This cable also incor-porated a 0.32-cm (1/8-in.) steel cable (attached to the model) that passed through apulley above the test section and was used to catch the model in the event of an uncon-trollable motion or mechanical failure. T
20、he entire flight cable was kept slack during theflights by a safety-cable operator using a high-speed pneumatic winch. Further discussionof the free-flight technique, including the reasons for dividing the piloting tasks, is givenin reference 8.The control actuators were energized remotely by means
21、of control sticks used bythe pilots. Flicker-type (full-on or full-off) control was used in flying the model, and thetrimming of the control surfaces was accomplished by small electric motors which wereoperated independently of the flicker system. The ailerons moved only downward from8Provided by IH
22、SNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-their neutral position, and during flight tests were linked with the spoilers in such amanner that the deflection of a spoiler on the right wing, for instance, was always accom-panied by downward deflection of the le
23、ft aileron. In the engine-out condition, blowingwas applied to the aileron on the engine-out wing to provide an increment of roll trim. Noaileron blowing was used during four-engine operation. The rudder could be deflectedsimultaneously with the ailerons and spoilers, or left undeflected, at the opt
24、ion of thelateral pilot, and, like the ailerons, was provided with boundary-layer control only duringengine-out flights. Artificial damping was applied, when desired, by deflecting the appro-priate control surfaces (horizontal tail, spoiler, or rudder) by means of pneumatic servoswhose output was co
25、ntrolled by signals from rate-sensitive gyroscopes. Strip-chartrecords of signals from rate gyros and control-position indicators formed a basis forevaluating the artificial damping employed during flight. Control travels used duringthe flight tests were 100 deflection of the horizontal tail, 150 de
26、flection of the rudder,600 deflection of the spoiler, and 170 deflection of the ailerons.Free-flight investigations of the dynamic stability and control characteristics of themodel in four-engine operation were made for symmetric flap deflections of 400, 500, and600 at angles of attack from approxim
27、ately 00 to 200; thereby, a lift-coefficient rangefrom about 2.5 to 9.5 was covered. With one outboard engine inoperative, the effects ofdifferential (asymmetric) flap deflection and the various other lateral trim devices ondynamic stability and controllability were investigated at lift coefficients
28、 of approximately4.2 and 5.5. The lift coefficient of 5.5 was the highest at which level flight could beobtained with the flaps set at an approach setting with a mean deflection of about 500.CALCULATIONSBy means of linearized equations of motion, similar to those presented in refer-ence 9, the longi
29、tudinal and lateral directional dynamic stability characteristics of themodel were calculated for comparison with the results of the free-flight tests and foruse in correlating the model results with STOL handling-qualities criteria. The calcu-lations were made by use of the mass and geometric chara
30、cteristics from table I, staticaerodynamic data from the present paper, and dynamic stability derivatives from ref-erence 3. The results of the calculations are presented in terms of damping ratio,period of oscillation, and inverse time to one-half amplitude. Frequency and dampingparameters from the
31、se calculations were scaled up, using dynamic scaling relationshipspresented in reference 10, to predict some of the handling qualities of an airplane havinga 24.4-m (80-ft) wing span. The initial response of this airplane was calculated by usingequations from reference 11, a rudder deflection of 15
32、0, spoiler deflection of 600, andhorizontal-tail incidence change of 100 being assumed.9Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-DETERMINATION OF STATIC STABILITY AND CONTROLCHARACTERISTICS OF FLIGHT-TEST MODELLongitudinal CharacteristicsWind-
33、off data.- The static turning-characteristics of the engine-wing-flap system_are compared with those of three previous investigations (refs. 2, 12, and 13) in figure 5.These data show that the turning efficiency 7 for the present model was higher at a flapdeflection 6f3 of 500 than that for previous
34、 externally blown jet-flap models, but that thejet deflection (turning angle), particularly for the 700 flap deflection, was low compared withthat for the previous models. The poor turning performance at the higher flap setting forthe present model may be associated with the fact that larger, higher
35、 bypass-ratio engineswere simulated in the present study, and that the flap might be less effective in capturingand turning this larger diameter engine exhaust flow.Wind-on data.- The wind-on longitudinal characteristics of the model for flap deflec-tions of 400, 500, and 700 are presented in figure
36、s 6 to 8. The high lift coefficientsshown in these figures are representative of those which would be required to providesafety margins for STOL operation, but the pitching-moment data show that high lift isaccompanied by problems in the areas of longitudinal stability and trim. One result com-mon t
37、o all test configurations and thrust levels was that a pitch-up occurred at angles ofattack generally at or just above the stall. Data for the 400 flap deflection (fig. 6) showthat before the pitch-up was encountered, the model was stable at all but the highest valueof CM and had a positive pitching
38、 moment. It would be quite simple to reduce thispositive moment to zero, for trim, by unloading the tail since the jet flap gives a verylarge diving moment with tail off. For higher flap deflections (and higher lift coefficients),figures 7 and 8 show that the tail incidence of 50 produces stability
39、at low values of aand CJ, but not enough moment for trim. Lower tail incidences (00 and -50) providetrim, except at the highest thrust levels, but the loss of stability at these reduced inci-dences is an indication of tail stall. Comparison of figure 9 with figure 7 shows thatboundary-layer control
40、in the form of leading-edge blowing on the wing increases liftcoefficient, but also produces more negative pitching moments which compound the trimproblem. In order to help overcome the difficulties of producing trim and stability simul-taneously during the flight tests, which will be discussed in a
41、 later section, the horizontaltail was equipped with leading-edge and trailing-edge blowing to prevent the tail fromstalling. No force-test data are available for the tail-blowing condition, however, becauseof malfunctioning of the blowing system during the force-test program.In order to give some i
42、ndication of realistic flight conditions based on the modelresults, lift and drag data from figures 6 to 9, with appropriate corrections for pitch trim,are summarized in figures 10 and 11 in forms for convenient analysis. A fundamentalassumption in the following analysis is that the model will give
43、the same performance with10Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-three engines operating as with four for the same total gross-thrust coefficient after it istrimmed. This assumption is supported by data and analyses presented in references
44、13and 14, and in figure 12 of the present paper. The engine-out data of figure 12 are pre-sented for lateral trimmed conditions using the trimming methods developed in this inves-tigation. The data show little penalty on the performance of the configuration with the useof these trimming methods. If
45、an approach condition is assumed with 6f3 = 500, CL = 4.0,and y = -60 (solid symbol, fig. 10(b), then the configuration is about 150 below the stalland at a speed slightly greater than 1.2 times the stall speed to afford safe stall margins.If the configuration has a thrust-weight ratio slightly in e
46、xcess of 0.45 with one engineinoperative, the descent can be arrested without a change in flap setting or airspeed inthe event of a wave-off, even with an engine out. If the flap deflection is then reducedto 400 (fig. 10(a), a climb out can be made at y = 30, still without increasing-airspeed.These
47、performance margins would seem to indicate a reasonable degree of safety and areapproximately those of reference 14. Figure 11 shows the effect of adding leading-edgeboundary-layer control. The shift of the curves to the left indicates the possibility ofoperating at somewhat higher lift coefficients
48、 with a given installed thrust.Lateral Characteristics, Symmetric ThrustThe static lateral stability deri atives of the model are presented in figure 13.These data show that the model with power on is directionally stable (positive Cn) andhas the large positive-dihedral-effect (negative ClO) charact
49、eristic of externally blownjet-flap configurations (refs. 2 and 13). The effects of engine thrust are to increase thedirectional stability and positive dihedral effect at high angles of attack for all flap deflec-tions. At the deflection of 700, however, large increases in thrust produce noticeablydestabilizing effects on Cnf and reductions in -Clp at low angles of attack.The lateral control characteristics of the model are shown in figures 14 and 15.The spoilers (fig. 14) ar
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