Sjoberg, Sigurd A

English

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RESEARCH MEMORANDUM 
PREUMINARY MEASUREMEWIS OF THE DYNAMIC LATERAL 
STAEZLITY CISARACTERJSTICS OF THE DOUGLAS 
D-558 -11 (RUAERO NO. 37974) AIRPLANE 
By Sigurd A. Sjoberg 
Langley Aeronautical Laboratory 
Langley Air Force Base, Va. 
CLASSSICATION CHANGED 
NATIONAL ADVISORY COMMITTEE 
FOR AERONAUTICS 
WASHINGTON 
August 18,1949 
..Date. 
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https://ntrs.nasa.gov/search.jsp?R=19930085944 2020-06-17T16:24:12+00:00Z
T h i s  paper presents 80111~8 data on the dynamic l a t e r a l  stability 
characterletice of the Douglas S-II (BuAero no. 37974) afrplane. 
For the airplane in the clean canditicm, the lateral osci l la t ions are  
lightly damped. In the lan- canditim, the  airplane perfoms a 
canstant-mglf tude  la teral  omi l l a t ion .  
The &@a8 &5$= a” has a eweptback w i n g  and eweptback 
horizontal and ver t i ca l  tail surfaces and w a ~  designed. f o r  cambination 
turbo  j e t  and rocket power. ’ A rocket engine had not ge t  been &stalled 
In the airplane b e i n g  w e d  in the present investigation. This a.irplane 
is powered solely by a J3-O turbojet engue mich  erhausts  out of  
the airplane has both s lots  and stall-cmtrol vanea. No aer-c 
bdance or control-force booster flystem is wed on any of the control 
the bottam of the fueelage between the wing and the  tail. The wing of 
a 
2 - XACA RM ~ 9 ~ 1 8  
surfaces. The air-glane has an ad ju tab le  s t ab i l i ze r  and speed brake8 
which are ins ta l led  on the aft portion of the fuselage. Figure 1 ehows 
characterist ics of the airplane. 
. a three-viex drawing of the a,irplane and table I presents the physical 
Standard NACA Fnstruments were ins ta l led   in   the  airplane t o  
measure the f o l l o w i q  quantities: 
Afrspeed 
Altitude 
Normal, longitudinal, and. transverse accelerations 
Rolling, yawing, and pitching velocit ies 
Elevator, rudder, right aileron, and s tabi l izer  posi t ions 
Sideslip angle . .  
Rudder, aileron, and e leva tor  cmtro l  forces 
Airspeed WBB meaeured with a swiveling t o t a l  head and swiveling 
s t a t i c  head mounted on a boom which extended apprmlmately 8 feet  
forward frm the nose of the airplane. A vane which measured eideslip 
angle waa mounted on the s a m  boom approximately 6 f ee t  fo- of the . 
nom of the airplane. 
Presented in t h i s  paper are 8- data obtained on the dynamic 
l a te rd  stabi l i ty  character is t ics  of the DO- I L ~ ~ I I  amlane 
during the f irst  two W A  flights of the airplane. A calibration of 
the  airspeed  installatian of the airplane has not   get  been obtained and 
therefore the airspeeds, al t i tude,  a d  Mach numbers presented in t h i s  
paper are uncorrected for po8ition error and airspeed4lead error. 
Figure 2 shows a the h i e t q  of a lateral o a c i l l a t i m  of the 
airplane  resulting fYam abrupt  deflection and release of the rudder. 
This maneuver waa made at a Mach number of 0.63 and an a l t i tude  
of 12,200 feet Kith the airplana in the clean condition. The data show 
the  osci l la t ion 16 slow t o  damp especially at small amglitudes where 
the oscil lation is  practically of constant amplitude. The .period of  
the oscil lation is 1.6 secande. 
u 
. .  i 
r i  
b 
WACA RM ~9318 - 3 
8 
Figure 3 is a time history of a lateral osc i l la t ion  in the land- 
condition. This oscil latiori  was again Lnduced by abrupt deflection and 
a constan-kmplitude  oscillation  with a period of a p p r o m t e l g  
2.7 seconds. 
release of the rudder. 'the landing condition,  the airplane performs 
Figure k is a time history of a portion of a landing apgroach made 
with . the D-558-n airplane. During the f i rs t  part of this  time history, 
between 30 and 4.4 seccmde, the pi lot  did not  a t tempt  to  s top the oscil- 
l a t i o n  by m e  of the ailerons or  rudder and the alrplane performed a 
canstant-a~~rplitude oscillation. earn 44 second6 t o  60 seconds the  p i lo t  
used the ailerona and wae a b l e   t o  damg the oscil lation. *en though 
the p i l o t  can.daug the oscillation, the oscillation is objectionable 
particularly durfng landing approaches and ladings becauee the controls 
m m t  be moved almost continuously. The rough-ir handling qualities of 
the airplane would probably be particularly  objectionable. 
Data were  obtained M the dynamic lateral s tab i l i ty   charac te r i s t ics  
I of the Douglae IL358-11 (BUAero No. 37974) airplane during  the first two e 
NACA f l igh ts .  These data show that for the airplane In the clean 
condition, lateral oscil lation6 a r e  lightly damped especially for smal l  
amplitudes. In the landing condition, the airplane has neutral 
o s c i l l a t o q   s t a b i l i t y  as the airplane perform a const&,nt-pplitude 
oscil lation. These constant-amplitude oscillations can be damped by 
vigorous use of the controls, but are objectionable t o   t h e   p i l o t ,  
however, became almost cantinuous movement of the controls is required. 
Langley Aeronautical  Laboratom 
National Advisory Comalttee f o r  Aeronautics 
Langley A i r  Force B k ,  Vs. 
4 NACA RM ~ ~ 1 8  
. . . . . . . . .  . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  . . . . . . . . . .  
MCA 
EACA . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  
6-10 
63-010 
39.9 
71.8 
41. 75 
53.6 
5.8 
0.50 
3.59 
40.0 
0 
3.78 
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A 
6 I 
Figure 1.- Three-view drawhg of D o u g l a s  S558-n ( WzAsro No. 37974) . 
6 W A  FZM Wl8 
02 
Figure 2 .- TFrne history of lateral oercillation of Douglas %55&II 
(Bubro KO. 37974) airplane in the clean condition. Flaper up; 
g e m  UP; shts locked; M = 0.63; h = 12,000 feet. 
7 
0 
b 
I 
Figure 3.- Time history of lateral osc i l la t ion  of Dougl&s v58-11 
(W1Aez-o Xo. 37974) airplane durfng a landing appmch.  Flaps 
d m ;  gear down; slats unlocked; at 0 eecond, Vl = 244 miles per hmq 
h = 13,960 feet; at 20 seconds, Vl = 2@ miles per hour, 
h = 10,900 feet. / 
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Preliminary measurements of the dynamic lateral stability characteristics of the Douglas D-588-II (BuAero No. 37974) airplane

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