A few Charpy samples containing a transverse EB weld at the V-notch location were produced. Three tensile specimens containing a transverse weld were also produced. These samples were tested at cryogenic temperatures. The welded Charpy samples resulted in average impact values of 20 ft-lb. This average value is as good as the NASA test samples with the base metal. The tensile specimens broke at slightly higher loads than had been calculated. The Charpy specimens did not come up to the prescribed level of 25 ft-lb. The results of the specimen tests are presented

Daforno, G.

English

NASA Technical Reports Server

NTF MODEL CONCEPT FOR THE X-29A 
Glanky DaForno and Gene Toscano 
Grumman Aerospace Corporation 
Bethpage, New York 
91 
https://ntrs.nasa.gov/search.jsp?R=19830010485 2020-03-22T00:04:44+00:00Z
This workshop on cryogenic models will, in essence, bring the Grumman X-29A 
NTF model design concept phase to a close. The next phase will be a full-detail 
design effort that will provide drawings ready for model fabrication. 
The entire study to develop a 6.25-percent scale model be,gan in September 1981 
when NASA Langley expressed interest in new flight test programs for NTF ,flight 
correlation aircraft. On this basis, and with concurring interest from Grumman's 
Advanced Development Section and Engineering Technology Committee, we proceeded with 
an initial concept drawing, which was further developed with the most up-to-date 
technical information available from the NASA Langley Model Design Group of the 
Systems Engineering Division. 
We then embarked on a proof of concept by physical demonstration of those 
areas in the design that were most innovative relative to conventional wind tunnel 
model design. In particular, these are (1) the installation of pressure tap 
passages in the wing via an electron discharge machining (EDM) process to drill 
the holes, and (2) the electron beam (EB) welding of the wing tips to close the 
access area for EDM drilling. The demonstration module of these processes is 
presented in the illustrations. 
Because of the concern to obtain the prescribed level of Charpy impact value 
(25 ft-lb at cryogenic temperature) in Vascomax 200 material, we produced a few 
Charpy samples containing a transverse EB weld at the V-notch location. Three 
tensile specimens containing a transverse weld were also produced. These samples 
were tested by NASA Langley at cryogenic temperatures prior to the workshop. The 
welded Charpy samples resulted in average impact values of 20 ft-lb for our heat 
treat cycle. This average value is as good as the NASA test samples with the base 
metal. The tensile specimens broke at slightly higher loads than had been calcu- 
lated. It was noted in the presentation that the Charpy specimens did not come up 
to the prescribed level of 25 ft-lb. The results of the specimen tests are pre- 
sented in the illustrations. 
92 
PART I 
REQUIREMENTS, GUIDELINES, AND DESIGN LOADS 
G. DaForno 
93 
The main use of the model will be to acquire high-quality data for the NTF-to- 
flight correlation and, compatible with the schedule, to obtain highly desirable 
data for the X-29A project. The task of designing and fabricating a high-quality 
X-29A model for this use is challenging enough that we must resist the temptation 
to add more demands. Even though a key capability of the NTF is (static) aero- 
elastic studies at fixed Reynolds number, this model is not thought of as a tool 
for such studies. The philosophy of the effort is summarized in the figure. 
PHILOSOPHY. 
a DATA FOR NTF CORRELATIONS 
- NTF TO FLIGHT: PRESSURES AT ONE SPAN STATION (AT LEAST) 
- NTF TO OTHER TUNNELS 
- NTF, CRY0 TO AIR 
o FLIGHT-RE F&M DATA FOR 'X-29A PROGRAM 
- LOW-SPEED, HIGHaPITCHING MOMENTS 
- SUSTAINED AND INSTANTANEOUS MANEUVERING 
- CRITICAL MANEUVER LOADS 
- DRAG WITHOUT FLAP HINGE FAIRINGS 
o MINIMUM DEMANDS ON MODEL, BUT HIGH QUALITY 
o NO Q STUDY PER SE 
94 
Pressures are key to the correlation. This figure compares pressure tap 
locations on the model and on the flight article. On the flight article, the 
taps are only on the left wing/canard, and those marked with a tagged symbol were 
specially inserted for the NFT-to-flight correlation. The taps on the model are 
split left and right, as shown. It seems feasible to place on the model the taps 
marked "desirable." 
PRESSURE TAPS ON X79A AIRCRAFT 
Eli...- TAPS ON NTF MODEL 
0 48 US, L WING 
0 do LS, L WING 
(33) 
95 
An NTF-to-flight corelation requires the incorporation on the model of all 
controls which are here shown shaded. 
96 
Among the typical details to be included in the model for a realistic corre- 
lation effort are flap-tab actuator/linkage fairings (if any), since they have a 
distinct effect at least on drag. Size and number of such prospective fairings 
can be appreciated from this photograph of the X-29A (l/8 scale) Documentation 
Model. 
% CURRENT 12.516-SCALE X-29A :*fIHD TUKNEL N03EL 
97 
The motivation and philosophy for this model are translated into the set of 
requirements spelled out in this figure. Note the q range allowed. Data with 
removed fairings are of unique interest since the X-29A actuation is an off-the- 
shelf rather than-an advanced item, and it would be desirable to establish the 
associated drag penalty at flight Reynolds numbers. 
REQUIREMENTS 
o COVER FLIGHT-RE FOR WORSE CASE: 
l LOW SPEED, HIGH ~4 (M = 0,4, d TO 90°, pT0 25’, &TO 20,6X1.0% 
1 MAX SUSTAINED G, INCL, MDP (M = 0,7 TO 1,00, a TO 7’+TO loo, ,R$TO 50X109 
- MAX INSTANTANEOUS G (M = 0,4 TO 1,1, a TO 45’, /3TO loo, &TO 55X10% 
1 MANEUVER LOADS DESIGN CONDITIONS FOR WING, CANARD, VTAIL 
o NTF-TO-TUNNELS CORRELATION: ALLOW FOR MAX UNIT RE OF 11 FOOT/16T/12 FOOT/NTF-AIR 
o Q EFFECTS AND RE SENSITIVITIES: RANGES ARE FALL-OUT 
o WING PRESSURE TAPS: 48 W,S, 114 + (DESIRABLE) 27 AT W,S, 50 
o INCORPORATE ALL CONTROLS AND DEVICES 
i CANARD, 3 & 
- WING TE FLAPS, 4 SETS 
I RUDDER, 4 6, 
- sTRAKE FLAP (DESIRABLE) 
o REMOVABLE FLAP HINGE FAIRINGS (DESIRABLE) 
98 
The motivation and philosophy for the model are further translated into guide- 
lines to be kept in mind in satisfying the requirements. On contour fidelity, 
tolerance demonstrated (to a certain extent) at Grumman on a high-quality model 
includes: 1 mil on wing leading edges (via hand refinement of aluminum leading 
edges of somewhat larger radius), and 2 mils on wing large areas. Body-alone 
data are very desirable on the X-29A configuration, and giving this up is a price 
worth paying only for substantial other advantages. 
GUIDFI JNES 
o MIN Q (ONSET OF SATURATION), MIN T, AND MINIMUM THERMAL STRESSES 
o SCALE: MAX SIZE, COMPLETELY SAFE FOR WALL INTERFERENCE 
(EVEN AT THE COST OF REMOTE ACTUATION OF CANARD) 
o MIN CONFIG BUILD-UP: CANARD OFF, V-TAIL OFF 
o BEST MODEL TOLERANCES DEMONSTRATED, BUT NO EXTRA DEVELOPMENT 
0 (PROVISIONAL): 
- 3 T/C 
- NOSE STRAKES AND BOOM 
- NO BUFFET GAGES 
- NO RMS ROLLING MOMENT 
- STRAIN GAGES FOR MONITORING INTEGRITY 
- ROOT GAGES? 
99 
The point of this figure is to draw attention to the fundamental elements 
which determine the mechanical and thermal loads on the model. They are: the 
decision on the scale, the flight conditions to be simulated, and the trade-offs 
(9 versus temperqture) in the test section. Of course, we strive for minimum 
loads. There is a minimum value of cNq once flight cN'.s and associated 
Reynolds numbers are given. Also, as soon as RemC is in the range 20 X lo6 and 
up, thermal loads close to the NTF lowest temperatures are unavoidable and there- 
fore we accept the maximum thermal loads in exchange for minimum cNq. 
DESIGN LOAD = I 'REF FS, 1 SCALE I ( ) cNq DES 
THERMAL LOAD Tt 
100 
In order to have maximum volume for instrumentation, highest strength, easiest 
fabrication, and best line fidelity for given fabrication tolerances, this scale 
was chosen as the largest that seemed safe for wall interference. The l/16 scale 
choice relies on NASA Langley guidance emphasizing prudence at the present time 
against transonic wall interference. Little information exists on scale require- 
ments for high-angle-of-attack low-speed wall interference in slotted-wall tunnels. 
Typical (geometrical) blockage values of.Grumman practice with conventional models 
are given merely as reference. Remote control of the canard is impossible in a 
l/16 scale model, but it may have been possible in a l/12 scale model. 
SCALE (WALL INTERFERENCE) 
l TRANSONIC SPEEDS, LOW.oG 
c = 0005dqS; b/W = 0.20 
REASONABLE SIZE, BUT CONCERN C = 0.07dFS; b/W = 0,27 
a LOW SPEED, HIGHa SEEMS OK 
o CONVENTIONAL GRUMMAN MODELS: 
- TRANSONIC, FOR 8' TUNNELS c =.o,o75qs to 0.095~ 
- LOW SPEED, HIGH06 FOR 7' X lo', C = 0.06% to O,lld@ 
SOLID WALLS b/W = 0,ll to 0,33 
101 
We take the onset of saturation (as shown in the NTF projected opera,ting 
envelope) as a reference minimum q at each Reynolds and Mach number. To keep 
(CNq)DES at a minimum, it is necessary to choose at the outset the flight con- 
ditions to be simulated. This figure shows that a (cNq)DES emerges quite 
naturally, since-a value around 2700 psf is required by the majority of the 
conditions. The normal load is only 1950 lb. 
MINLMLTM kNdDES FOR l/16 SCALE NTF MODEL OF X29A 
I 6000 
5000 
4000 
3000 
CN4. 
PSf 
2000 
1000 
0 
I- 
, - 
I 
I 
50K 
I 
I a 
I NTF/OTHER TUNNEL* CORRELATION NTF-TO-FLIGHT CORRELATION 
/- 
(CNq)DES selected (12-4-81) 
I 
I 
1650 
 
-Aero w 'ads- k 
I* , At their maximum Re. MDP = mz : design point; SL = sea 1s !vel 
102 


NTF model concept for the X-29A. Part 1: Requirements, guidelines, and design loads

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server