NASA NACA-RM-A53J23-1954 The effects of operating propellers on the longitudinal characteristics at high subsonic speeds of a four-engine tractor airplane configuration having a wi rat.pdf

1、c/ * COPY 7 RESEARCH MEMORANDUM THE EFFECTS OF OPERATING PROPELLERS ON TEE LONGITUDINAL CHARACTERISTICS AT HIGH SUBSONIC SPEEDS OF A FOUR- ENGINE TRACTOR AIRPLANE CONFIGURATION HAVING A WING WITH 40 OF SWEEPBACK AND AN ASPECT RATIO OF 10 By Fred B. Sutton and Fred A. Demele Ames Aeronautical Laborat

2、ory Moffett Field, Calif. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WASHINGTON Imary 7,1954 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-X RACA 53523 I NATIOIWL ADVISORY COMMITFEZ FOR h RSSEARCHMEWRARDUM AERONAUTICS ?XEEZFECTSOFQPERATIRGPROPELI;

3、ERS ON = LONGITIIDINAL CHARACTEEKEf?ICS AT HIGH SUBSONIC SPEEDS OF A FOUR- ENGINE TMCTQR CONFIGURATION HAYING AWINGWfTB“OFSWE3ZPBACKANDAR ASPECTRATIO OF 10 By Fred B. Sutton and Fred A. Demele SUMMARY I -8 An investigation has been conducted at high subsonic speeds to determine the effects of operat

4、ing propellers on the longitudinal char- acteristics of a four-engine tractor airplane configuration having a kO“ swept wing with an aspect ratio of 10. Wind-tunnel tests were conducted through ranges of angles of attack and propeller thrust coefficients at Mach numbers from 0.a to 0.90 at Reynolds

5、nunfbers of 1,000,COO and 2,ooo,ooo. The effects of varying propeller blade angle, tail incidence, and vertical height of the horizontal tail were investigated. The over-all effects of operating propellers on the longitudinal characteristics were not large when compared to the effects of propeller o

6、peration at low speed. Compared to the model with the propellers off, operation of the propellers at constant thrust coefficients generally decreased the static longitudinal stability. Increasing the propeller thrust coefficient at a constant Mach number increased both the static longitudinal stabil

7、ity and the trimmed lift coefficient. Operation of the propellers at constant thrust coefficient increased the wing lift- curve slope but had little effect on the variation of-lift-curve slope with Mach number. Operation of the propellers had little effect on the Mach number for longitudinal force d

8、ivergence at a constant lift coeffi- cient but resulted in a decrease in the rate of change of longitudinal force coefficient with Mach number at supercritical speeds. This effect increased with increasing propeller thrust coefficient and with increas- ing lift coefficient. A method of predicting th

9、e effects of propeller normal force on the pitching-moment characteristics of the configuration is presented. Com- parisons with measured effects indicate that the accuracy of the method is good. . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NA

10、CARM A53J23 . RaiBing the horizontal tail had little effect on the longitudinal stability with the propellers removed but was destabilizing with the propellers operating. 4 For an assumed airplane, operating at the power required for level flight at an altitude of bO,OOO feet, calculations indicate

11、only a small change in the stable variation of tail incidence for trim with Mach number compared to the propellers-off condition. INTRODUCTION The potentialities of turbine-propeller propulsion 8ytem are well recognized, particularly with regard to the take-off and range capabili- ties of multiengin

12、e airplanes. The combination of a turbine-propeller propulsion system and an airframe configuration utilizing a sweptback wing of high aspect ratio should make possible the achievement of long- range flight at relatively high SUbSOniC speeds. This propulsive system could utilize supersonic propeller

13、s with high disc loadings. It iB not believed that the effects of these propellers on the longitudinal char- acteristics of swept wings can be adequately predicted, either by exist- ing theoretical methods or by available experimental data. An investigation ha8 been made in the Ames lravity locatfon

14、 (See fig. l(a).) acceleration due to gravity propeller diapleter maximum thickness of propeller blade section horsepower per engine incidence of the horizontal tail with respect t0 the wing- root chord propeller advance ratio, - measured effects. The small discrepancy at the lower angle6 of attack

15、is believed due to lift stemmIng from the asy-rsnetry of the nacelle fore- body. The theoretical computations did not account for any lift contri- bution due to the nacelle forebody. The effects of propeller slipstream on the pitching-moment charac- teristics of the wing and tall could not be predic

16、ted to any acceptable degree of acrmrac y with existFng methods. It is believed that the com- bination of the effects of ting sweepback, of viscous separation, of propeller 8lTpstream rotation, and of wing-nacelle interference makes the estimation of slipstream effects on the pitching-moment charact

17、er- istics of the wing and tail virtually impossible for the present model. Figure 21 shows the variation with Mach number of the various effects of the operating propellers on the pitching-moment-curve c Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,

18、-,-NACA RI4 AZU-23 13 SlOpC= A(dC previouslymentioned. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-16 NACA RM A53523 Longitudinal force coefficients were only slightly affected by changes of Reynolds number and of propeller.blade angle at a Mach

19、num- ber of 0.70 and 0.80. At a Mach number of O.gO, increasing the Reynolds number from l,OC!0,000 to 2,000,OOO resulted in sizable decreases in longitudinal force coefficient. CONCLUSIONS An investigation has been made of the effects of operating propel- lers upon the longitudinal characteristics

20、of 8 four-engine tractor airplane configuration employing a wing with Co.,df: ;: 4.96 4.83 4.61 4.27 $3 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-25 Cable III Iv V VI VII VIII Ix X XI 6 7 8 9 lo 11 12 13 14 Tail aem* 09 2 02 2 02 2 tail off 0.10 g 0: tail off 02 2 tail off %* Br R1 TAIL HEIGHT = 0 b/2, i.t = -4O, P fI = so, R = 1,000,000 - Concl.tid $ (b) M = 0.86, o.go z r Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-