The NACA impact basin and water landing tests of a float model at various velocities and weights


Material Information

The NACA impact basin and water landing tests of a float model at various velocities and weights
Series Title:
Alternate Title:
NACA wartime reports
Physical Description:
10, 9 p. : ill. ; 28 cm.
Batterson, Sidney A
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:


Subjects / Keywords:
Seaplanes   ( lcsh )
Aerodynamics -- Research   ( lcsh )
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )


Summary: The first data obtained in the United States under the controlled testing conditions necessary for establishing relationships among the numerous parameters involved when a float having both horizontal and vertical velocity contact a water surface are presented. The data were obtained at the NACA impact basin. The report is confined to a presentation of the relationship between resultant velocity and impact normal acceleration for various float weights when all other parameters are constant. Analysis of the experimental results indicated that the maximum impact normal acceleration was proportional to the square of the resultant velocity, that increases in float weight resulted in decreases in the maximum impact normal acceleration, and that an increase in the flight-path angle caused increased impact normal acceleration.
Includes bibliographic references (p. 10).
Statement of Responsibility:
by Sidney A. Batterson.
General Note:
"Originally issued August 1944 as Advance Confidential Report L4H15."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003804832
oclc - 123898542
System ID:

This item is only available as the following downloads:

Full Text
O)AC P L- 4.3

ACR No. L4H15


August 1944 as
Advance Confidential Report L4H15

By Sidney A. Batterson

Langley Memorial Aeronautical
Langley Field, Va.



NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
I advance research results to an authorized group requiring them for the war effort. They were pre-
viously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.

L 163

-- --

Digitized by Ihe Iniernei Archive
in 2011 wilh landing Irom
University ol Florida, George A. Smathers Libraries will support from LYRASIS and Ihe Sloan Foundation


htlp: details nacaimpaclbasinw001ang

:.'.CA ACR iTo. L HI15


ADV I.iC' CC*'.r LrIAL -P'.T

T:E FAi.. I;'InCT EiiT ,.-AL "T 'LF L.;:7DING TE.T-


.ITL -2iCiT3

By Sidr:-y A. Batterson

The first dlta obtained in the -."ited States under
the controlled testing conditions necessry".- for estab-
lishli,: relationships the i.t.orous p 3-i.eters
involved when a float ha.--" b-oth horizontal and vertical
velocity contacts a water surfacee are ~resented. The
data were obtained at the '..'"A ".iract basin. The report
is confinr,'l to a r.f sensation of the relationship bet.'een
result-nt velocity i.,. .. .act normal acceleration for
,var .ipns float '.-;,;-ht.s .-hen .ll o L-er -.sra.v.-t-'crs .re
constant. n .i. iz 01s.' t, ,: r, ,.,:ntal r.-sults inJicated
Lhat Ihe n-jyimuji imi p..,t n.or..-a]. *.c.e:ie ti'. va 3as pro-
crtcrnail c t'.;, squ'a:"e cl.' -, litant .- c c it', t'.:-t' :-J?-s in flo:.t *:.if.t -'e .ult d i-n i-c"c ea n t!i:
ImIL iT.!,'U i.l z.act nurmi al cc ? -r- t f.-_, a.,d th-i.t an incre-.;e
1: the fli :ht-patL anile r v'set ".ncr,_-.3,'* iiT-act rori!al
acc.el r ticn.


Until the present time, almost nll exp,-erimental
v.ork re iat. to 1.ocdz or: .eaplan,:s l-i-I in3 n 'v 6ter InS
consisted of fuLl-S-ZA.e landing tezts. attemptss to use
result-l of urje full-scal.! t:3ts to e':tablish rela-
tionahips :i,,cnr tre v:aricius i..pact parPm-it- Lers h1qve not
beeni very successful for two r.asorns3 (1)A prea-rc'.ng-d test
progr,-'n involvinL the isol-ion of selected parArrieters
could not oe carried out sinc ';hi values for a number
of the variables were a function of piloting tchr!ni .'u.
and th.- natural coni, tion.s of the wind -and the s. a .vere
not controllcbl- 'ur'n:-' the test; snd (2) the available
instrimu'Jnts proved inadequate to supply, sufficiently
accurate results.

;ACA ACR No. L14115

In order to overcome the risadvantages of full-scale
testing, an impact bosin 'n .'vch float models could be
tested under controlled conditions vas constructed at the
Langley Memorall Acronautical Labor~tory at Langley Field,
Va. The first data obtained in the NACA impact basin,
which are ccnts.ined in the present report, may be used
with the results of subsequent investigations to establish
basic relationships among the impact parameters. Logical
interpretation of results of flight tests investigating
conditions beyond the scope of the NACA impact basin will
then be possible.

The T..resent tests are confined to establishing a
relptionshiop b-etween resultant velocity and impact normal
acceleration ."or s:?alanes of various weights. The
solution of t'.e problem of determining landing loads
must fcllicow 'ar'th.r investigations under controlled con-
diticns in o'nicr to isolate tl.e effects of a number of
other pjr-.Jre '1s sa uch as flight-path angle, dead rise,
bull sh;ib, 'd trim.

V resultant velocity ci0 float, feet per second

Vh horizonil velocity corir'onint of float, feet per
s e con1!

V, vertical velocity comp-)-,--b of float, feet per

g acceleration of gravity (J2.2 ft/sec)

y flight-path angle, degrees (See fig. 1.)
T float trim, degrees

n, impact acceleration normal to water surface, g


Float Model and NACA Lun;act Basin

The model consisted of a float designed to conform
to exceptionally high strength requirements. Care was

C C I7r 7 7,',T'T IA L

!!ACA .'-CR '!o. L1.4115 COI-TIDEITL.L

exercised dari1r ti-i do jin ,nd construction of this
mo-el t'. obt-inr a -'. asonc bl' smcotth tottom. The 3cet-
metal s':in -aned mrn3t of the tr_'uctural m mtera vwer. r. 3de
of (iurAl in. or.Oer tc obtain the v.eiqlt con-
fornming to the lc::i1 sc:-cifisations. The wei-ht of the
moiel w,?s i-07 pol"n:s; n-:.oever, provisions. wErc included
wher-ebv 2000 pounds of r;ddiional v.eight cold be bolted
onto the sides in lrcr.".t:ents cf 25 pounds. The lines
and ne'citineit di..--i'ns ion-s of the flc:it mcdel .re shcv.n in
fiure 2. -. fe'-tur o the-3se lines is the IBtEnce of
all chine 11sre.

'rTh:e ..'. imrotct basin .i. esenrtil. a concrete
tnk $6 f t lcng, feet ;ti l., nd 11 f.- t dtep wvith
a normal -.a-r -i .h of -t. Heav-.' uilt-up teel
rails are sn11r-..:.A-d -alng t: .;n- ir-i-e Iengthl of the tank
:ith the e-.:certi'':, r? ,he l ut lIe:-t, whi-h is to be
occu.r01Pd- by; a ,.ve .: : The iails al., a port-'or of
the tank a e -s'-."n ri i'ure 3. Th]-e l .rei', lo.vow r, a'id' sur'-=.ces of e I.c rail we'Th: e rSound st. aigrt and
parallel withinn --t t'.:.ra.:1:e of L.C02 inch -nd the sEi.i
tolerx-\nc? .as h:l d 1 ir-in-r ilnst1 .tioil in locating the
rails with reso-:r:t t.o =tj: other rnd tc the :'.ter surface.

A 'nain carria: a dro., lin:S.-: e to which
th -n nod?! is Castenedr tri,"els d ,ov'n the tan': on the
rails. f'iure I. ho'1. t.-a- ennri 1 :trr:-.n ement of the
car-' with many of the seco-ndad.r'y membe-rs. omitted
for clearness. The. basic ear.' structure consists
of chro'ne-;.ol -hdenun steel tubing (fig. 5): the total
weight, withoutt mrodel and int3 -urr.ents bit. including the
dron lin!kage, is approxit..telv 5000 pounds. It mrna
be noted that both. ic',wer and upper wheels ars provided.
The u1j-er wheels are ara:.ged rrn sets of tewo and
located in trucks which swivel in a vertical olne
parallel to the l-ngit udinal crriae cC nter line so
that the lo:J Is aqual,.ized b'stwj'een the t':o w'h-els.
Solid-ruhber instead of one-i.':itic tires are uijed to
reduce to mini.nlrn defle-ct.ions under load. Before
installation, the outside diameter of each whe-l w;as
ground concentric to the, axle baciring and thfn balanced.
The lower "vho-ls nay,- b jsckl-ed up the, low.ver
surface of the rails until bothl u 'p- r and lower r wheels
exert -p. rre.determirned pressure o:-i thk rails. Oscilla-
tions tr-r.nsmitted to the carria e rcre limited by this
arrangement to very sn::.ll amplitudes and therefore havc
little disturbing effect union th! actual drop process and

C',?I 7F ID1i'T IAL

4 CC:F-m::'TTDLL :':AA ACR No. L4R15

the instruments. Lateral restraint is provided by four
side wheels bearing upon the inner rail surfaces.

The Crop linkage consists of the boom and the upper
and lower linkbars, which are pivoted at both ends and
with the boom form a parallelngram type of linkage
(fig. 4). The model was fastened rigidly to the lower
boom fitting by means of bolts through three lugs built
into the float (figs. 6 and 7). By this attachment, the
float was restrained in all directions with respect to
tihe boon but had freedom in the vertical direction since
it was attached to the narallclogr-.m linkage. The lower
boom fiting provides a r:.eans for setting the float at
va,',ous trim s and m.ngles of yaw. The float may be
d-orped' from :ny height up to I, feet, depending upon
the vertical velocity component desired, by engaging
tl;e corJesrpondirng rack troth '.'ith L laJtch on the
ca-ria,?e. This latch is released by means of a trip
za.1 loc-ted at the Roperr po'-it i.lonrL one rail.
Releasing the latch allows the boom anl the float to
drop f-re_-ly except for tl-.e rstraintI imposed by the
upner and lower linl'bars, which kVep th' coom vertical
as the float Crops. The action imn.arted to the model is
not rerpendi-cular to the water surface during a large
pirt of the drop. Since the ir:.r.-ersion occurs when the
linkbars ar lev-l, howvLve-, any horizontal
comron3nt contributed by the linkage arrangement is at
a minimiur: d'urng impact .nd is negligible. The dropping
weight '-la be var'ec t.- the sadrition of lead bars fitted
around the b-om aid bolted together as zhcwn in figure 6.
The total weight of the boon and linkb.-rs alone, and hence
the minimum drooping weight, is 7'0 pounds.

In order to simulate wing lift, an air-cylinder and
piston arrangementt that can apply ny desired lift on
the nmod,-l,_ up to 2400 po'.inds is incorrorated in the
carriage. This mechanism is referred to as lhe "buoyancy
engine." The lift is applied to the model by so connecting
the boon and the piston of th.,e ouw-yancy engine with a cable
and sheave system that the piston: is forced to travel
against the Air Pressure in the cylinder as the float drops.
The amount rf lift exerted on th. nmoJel depends upon the
initial air pre-sur: 3sujplied to the cylinder before each
run. The rod running upward at -r angle from tha bottom
ruar noint of the boom (fig. 6) is the lower-end connec-
tion of th. cable syst-m. .'.7th this arrangement the'
application of the lift may bc withheld throughout the
downward travel of the boom until just before the


I.',.C ACR Fo. 4iHl5 C1CUFIDE, TIAL 5

float contacts the water, T:'r- float is thus allo.wedt to
attain ;-.: desired vertical velocity coi.,pcnent.

The carr'a -e has no self-contained ,frive but any
d:;sired horizontal velocity up to 110 feet per second
may be attain b-; means of a catapulting system. The
catapult is of the t,'p used tby the Ivvy on shipboard
for l1nw.ching service .,-pes and accelerates the carriage
to the desire-i snepe in a distance of 60 le-t. The drop is release.,: at such a point that the inmp ct
occurs aprr r.:r'ately 1)0 fe-t .ro,.i '.h r.oint at whichh
the cat.-.piltf stroke ends. This procedure allows a
r-.ric. durin.- w.hi-h most of the irregularities and
oscillations inherent in the catapult run are damped
out. Follower, the i",--ct, the carrla,:- run is
terminated '-r a :ivy arresting gear c:asttle of dis-
sipating the total kinetic energy of the carriage in
less than 100 feet.


The co:ration of the horizontal-velocity recorder
is dep:!'dnt upon 1-inch strips o' thin metal, referred
to as "interrurters," that jrctrude about 4 inches
below t?.e lower inside corner of one rail at 1-foot
intervals thrcuthott the lenth of the tank. These
intcrrnrrtr-z r-.a&v bc s3en cn the lit rail in fi.urs 8.
A photoelectric 2el1 is !oca Led oi the ra rl:-;g.a in such
%:'. annir thL t each intErruoter c-u'es a br--a: in the
pholtc ieoctric-c-. l circ'.'it t s thec car:--i.gge travels
down the tn-n:. T.he cul-rent is th'Ien f.d, to a iigh-
frequency j-i\'t o a reccring oscillo-
graph in which a shift in the record line each
time the photo-lectric-cell circ-cut is ce,-1edr by -:.n
interrupted r. In adrfiti_ on, the oscillograph record
contains ----Scon; c tir-.rg l1i3s. Inas'uch as the
carriage is travling at '-rctically constant velocity
b'-twe-n th? "nl of the cstani'.t .stroke End tYe impact,
this velocity c-n be deter;mil;ned by Jivldin. the nurr.-br
of interruptcrs nassd during this interval by the

The Jisplaccrment Cf the boor and its velocity in
the vertical direction are also recorded by the oscil-
1o raph. The displacement 's recorded by a galvanomtter

C, NFC": dI

FrACA PCR No. I14+15

elemne:nt, which deflects in proportion to the amount of
c!rrc-it thiiLt flows tir'ouch L nlece :f resistance wire.
'i-e c;' length cf t-is wire is v-ried with the
rositicn of the? Ico.n i"y zor.le ci:n the ci-urit through
a sl-ding contact. Th.e J: placerient of this contact
alon, th- wire ollows' th3 oo:. travel. Thu sane
:.I par-'tus is U3s in tle deter::;Iination of tle vertical
velocity c.:r orient. In order to determine the vertical
velocIty'nt, hovev.r-, the current derived from the
slidc vt ire is directed ino s.vral high-capacity condrensers
.J.nd hus l-_octricll]." iff "'orent-i ted The galvar-om3ttr
ele.r!::t r6coria bris c}-n-:, 1,1 crrr n+i., which i9 a
function of e he boo;n vrt.ical veloct:.-. The velocity
is then deri v-.i fr'o; thr.- recorded change in current by
ref -"er .ca tc s:tit:-...1 ca.i braticn curve.

Tlc im .act r..r.ral aca'lera-ions '.cre initially
ct.srnin;dl wvit.n ar. anclsc lrc;ret thit recorded the
flIxu'e of a van : as: .c 3ured oy strain
. Th- fr. :ur z .c of tli- ac Celeronrcter :;as
12.z c.'cl::s p.,:r1 ..c ic. An .rmonlifyling sjst!m was
rtc ul!'Cl, hr.v.el to d.;ct th.e Lcceleromt!.r to tha
3scilo-rwranh t.-,.. r.en-orned the other v-lu-s. Since
.mrlif-yin:: eq'uin :nt -.:[.s not available in time for the
.ec;s, a .s:Fcial recorder wasv nces-s3ar for this
,.rticvlb irnsta2r.~enc. Thi records obtained during
the first -,,rt of the test sho;:ed that e-xtr.-ne-us
viiratilon. ere distlbin- tiL.-h galv.anori.eter elemrrint
".'hich riecored t.e i'.r:-ct accelr.'atiors. An accel-
rc.roioter that rcc. ride tne ancjui'.r disrlace::.,nt of
an .n': sl anc- a:l.vsn;mete ';as3 su:.'stituted
fcC tie re- i of t.'-.- c..t. Thi. instrL'uent had a
cclf-ccnt. A; ed or 7'.a, recoirdi;n ;.yste-., had a
're -e;:. of i'. c ./ies nar eco:.d, and w.asc apparel ntly
i .ndis.rb d by e:-.,t"r.- i us ns. Thu damnpi.t7r. *'.s
bet";oo0.n five-te:It'ls anii'. six-tenths of the critical
do.nii:.. The i.1 tr t 'as- enclos..d in a box ;nd
micuntue ri' on the boori t3IItwc':i the frfnt anid rear
float fittirgs. Ih :.:ot.ntrn may be seen in figures 6
and 7,


The data prCse6itcd herein were obtained during
the initial calibration runs at the NACA impact basin.


PC' ~--O IPI_~rJ I

N1AC;. C. IT:o. LIjilTm5

The test pr J:-am thus er.en,:5 upon the c -lib'etion
r1* ulirsments, which neccssitac, -cx rims at var.-'n w, l-:'-,ts
and 1 ;i.;1i. velocities. A test -.-."-:.: r: was therefore
formula that consisted of a systematic series of
run fI .. .'.'"; the v '*".;-.tion f 2ma;im~ihn normal acceler-
ation was .'bti as a L. Action i.f resultant veloci '
aiv' float weiTght with all other '..:: te!es Crnstant.

The model was tested at drc-. :n we~lt of 1100,
1500, 1','0O, and ?,.00 ..r!nL. A cr;:-lete series of runs
was .-. :-. for each oei -.:t, with horizontal velocities
covwrL.+ an :. ..- te r.... from 35 o --, feet .,"
second. ..n atteiapt ..wa= ade to maintain t4 ., ..-.u't
the test a constant ratio vertical velocity con-
ponent V. to. horontal velocity cori .: -
v'ilue o*f V. /V; is -s-. i.-; -.I tan y, where y is the
f'- h L-pathn 1.o. T:..:: valuo of tan y was selected
as 0.12' for oresnt tc'its. In order to check t '.,
ef" t of aa increased .i ..- ,,.-ath ...,,... four ..~.-
tional runs :. which tan y vas roximatel" 0.2-',
were ..- 'for the dro of 1100 rnds. The
trim 5 s o3 and the i of as 00 -.. .. .,ut
each series .. '. t, e i.. -c t -'oc c a lift .
to the droo .-L1. ; igot a.': e ,. aas ex-L.':.d on the
float by means of thir, buoy y ine,. normal
accelir.tions were recorded a '.:" the n.ximu~n valae 's.
nr t" l fo r -h r,.i_.

'Iee ar-l''' r ..e us: in .-' _'rs-s re :.L.- : ives
i ..- .. I,:' '. .. l ? 1. t ': th*.I t ihe

Hoi. .nt;i 1 '.*lo t :. t 'D r se 'i- ....... .
Ve t ia -.1 v :. LCd ", 1 -. r. r .-c ; .,.. ..... 0.2

jut. ;7u e. ce'. L.-- : ~: .:1 :.1 i r :* ]. *- .* oo te or

- ,.L ? ; *. 1 .r.. t r..- ;.. :1.i ? r:- 3s to the
S sv. ,in: .:. te '. hic.* .1- 1 -, I. n ". -c""r. _- ;-:c c -nts
t .F x L 1 ; :' -i' s r L :r'-- .'. it L ,:
r'.r. .: of ar,.-, lie,:-., lc, a f ..-iu.:.c; f c. f" :;>:. tl.,-. s Aic ton

C,.T FIL T '.. L


A.r LA.CR No. L}.H15

the nti.ur-,. fr.e-,encr- of ti'e acceele-oete: and is based
Ir:co rL-. i ..7t i : rq.elc;.- is ,CoLnsS curve aerived
;.:.'e-..s.- 1 for the inztrutr.:nt. Irnas.nuch as the.
*s i- -s J.L ;,.od o ;:-d decreased in acceleration
v;-yr1us at n igh- i':re :ency lcads, it- J:ts concluded that
ti-.e natural fre.u;enr.- of the as~!elrom.eter iwas not

In tn( l.: .r velocity r.n,y-s, the atterrpt to
1:T., i: n csr'stt.,t fli:hc-Jp*th a '.le 'was not very
zuo '.'f'f., f be's; se in cOal ibra' d .ta vire available
,-r. i th:. :ir] l '. ocit.- c r1i. onenbs had to be -sct.-
r.ated ,. In ',dd It ce, d. viJ t .occ;':'red between the
" 1.'r ca i s. lc ." 3j.z e. i..c'lenits .--pectod 1i.:-1 dron calibra-
t , .e:.L1I.:c " t-L`3 cLtrri: e tt r. 3- and t.' v rticai
'":lo? it.; .2C'poi n..t3 01 t ..i-.d d'u'ir :1.:1 t- t r'ms. The
i i'tti.. t .. .. .- :i .at:ns s.: cra.-.' d rapidly y
I in the cr i arL.I:ir itica. vel c.. cy ; p. -.y components and
the.:. rfor cc.'..- :. the orr of th.e flight-path
h i
1 I,' ft i. h -t..-n at .low velo ties.

'* ..-CT .. r.', *, T ,- T T IT -r-T'
S .. -.. .J A D~ L.IS)UT..I L

'Thoe '.sulr.: cf c:-ch series of tests for dropping
wei hts j i1 1, '0,, C 1 ', r 2 .. lr2 -,0 pounds nre shown
:. i,.'-:. it ,hic nlot- in ur-s ,. ].2, 're -,-c tive' .
'h.s r,- -. .t '. o '. .:cc le:'. -,? i units .re J er" ed
" t-he ''.-: rr... r'l. I :...T ,,'ch 2.s the. buoyr'ncy

1 s 3s si. tr.ct.ted :'c .n :ce v'- btti, t..': fror., t.a
ace.'. 1 Ltr i,., c o I .c l t.V force resultin. from
l; ilLrCt. The re "ults of fth !'ou- runs for which h tan y
wa app'-.'-i.t .ly ',. 0 are .1:Ott. .c in figure 9, A-h ch
cl..r y i1 nc'r, :.'- t :ni in.'cease i.n t fliht-puh angle
incr---:. S.' r ncr m:. .-.i z 1cceler'ftion,.

T.3 r.],o'-t-dasn line;? fn 'igure3 9 to 12 have slopes
t;At re ?. srnt the prcporti.on

ni cr V2

aind ass throuit thle exp. er .i"m.l -nts that correspond
to tan y 0.125' as detemir.lne-d fr,.r f.i-re 5, which
sh}nws tI.n vaVriati n ii. fl.h1 T.-pt. th w .1.l w eith resultent
vlinocit:t for- -.- f:ur dr oppin? v.e;.ht3. by referring
th.: e.ired-t cxperim:r:! tal curivc of f.:;:i.rc 9 for

*,':'i ,ID ..TD IL


NACA ACR Noo. I41.15

tan y= 0.125, to i -ure 15(a), the maximum normal acceler-
ation can be obser" :i to be directly ipr..,-rtional to V2
i.'-r. the fll.,-ht-pt. :mr le remains constant. Below 72 feet
r:r second, however, this pror.crt'on no lon.7er holds
and the maximum normal accelerations show a lar2-jr increase
with result t velocity than is -Li,'icated by the line
for ni a V2. This trend is ;;:er;ced in order to be
consistent with -h- four points of figure 9 that were
obtained at tan y 0.200. Thi.i analysis can be
appli:.' to figures 10 a:n- 12 and f .ur-cs 15(b) atd 13(d),
respectively, althe-i the the n in which the flight- :-i:le remains constant .ir. the amount by ,,.':ich
tan y varies offere r somewhat in f'.ru:-.s 13(b) and 13(d).
By z.' 1.yinj this anal-. s to f!L."'.: 15(c), it would bo3
expec' -'. that the values of :..- : l normal accelei';tion
and resultant velocity that correspond to values of V
fi':C: 76 feet r-r secc '. (the at which tan y 0.125)
to the maximum velocit would show some proportion
other than V7 since the line reoresnmti tan y
a definite slcnc: within this ra'i,_: of V; that is,
at V > 76 feet -_- sc.'id, the values of maxim-u normal
acceleration should 11i below the curve for nice V2
whereas, at V < 76 f (?t per second, the values of
:.:1::i:ru:iua nor.-l. ac.?lc- .tlcn sIhould l1i- above the curve
f. n- 0 r V". p .. S1 soi'.s :C*. t :1..: 1. th. 2 c*s2 .
Th- .' d I ne fo n V is uc t .,,i n -l t the
-..r,. c 1.c) at '-i.ich tan 0 1 0.125.
I to.,.i uopnic rs ~ -t pi ic-v.'vI d ] -.h-- .fli '. t-pn t-!i *in.-e

frcI". ".-. '... .c.V l :. ":;'.-ts v.. .:i",ctl: 1 s the square
f t'I j '.:- S .1 i ". "- ... ".: .. c -"*.-l ..clus "i- '. gr ', es
..: ..,: .:.:. c- .- :-_' -"- 1 ?: l-. id .. i stance
,i? ? ... '....... 1. -_. i- .- "I. -. _- t.. : iT

r'i-'." c :;.; cf .b:-
t ... r n: Linc ce n- ..- f :r .Ic'.int '..c c.bit.Ai ncd nd
Lh: -... _; of y ''.. .-t: prox,. -in:.t- e 10'3 D rent

.' h li.rne c n of fi-vres to 12 are reolotted
r. ri iure l -, .'i.-. .- rfo-.e prez.=:-:. the experimental r of ma:': ia "-. ; t nLc;-inal- ,.c.elerat o, n with
re._ul; velocity; f. r v-rim.u. dcr1:nLi.-, weights with all '-ar.'i'e'tL.ers 3,'.itait. Tt ima' be nt-ed, th t che maxinmu' accelers.tLc. dce--,.ses as the weight increases. The
curve epre..:e .'. r of )-- ;' .nds s -ifted, 8
was in-ji.d -'" -u ., ..- tcus .. he. ..' .lv 'inor.etr ele!"ent
that -recorded tI-:.: -. .l r.:i for t .his 3er-ies of
.;*2i out of bl C:ce- .L:'r-e':'": U.s 1:. ~ :-.i 'ins vere tllherefore

.'r':FI., i' :..

rJnCA ACR No. L4H15

sune rinrrcsd i.ipon the accal.?eromet. r record and accelerations
-rr' clr' t1. an th:- actual 'nn ict accelerations v:c-re ccnso-
q.Lr'tl" r"coded. !;o at.te':;pt was maLde to --valuatu the
ilccre,3I 3 in mL xilnz n.-:ai':l aceleraticn that resulted
f '-r-,I tCl in n sCc' i en .iherht since e the data anpeared
ilr.c'ie " e r l' lt.t i s purpose.


Rfj. J.ts cf t.sts L.t thn ILA n impact caui.n of the
v-i-iast-,n .ith r3sultta-it velccRity a.nId eightt of the
n' a cce-lratin : resultin,' f1 jrom la'nd:ng3 of sea-
plrecs on waSer Inr'ica-. d t-e folluvwin.l conciusiisons:

1. Th; i.Lxi:-i3u' lic L c' nor -ilal Ccc leration -.;as
or.-,; to s; .'re oi the result-.nt velocity in
accorirdlnce lt- i th. e l 1.a.v (-c' fluid resistance.

2. The ri.:-::. L'. l i,.n Ct normal acceltratic-n decreased
as the vcii.ght pr.)viocd All other zondi'icns
rlna lin d coii.t nt;.

An .icrese, ini maxitun impact normal acceleration
a',cco'olr : i..d .,n incre6 as-. i1n L iIt-.'a th anEle provided all
o'.hcr conrdi 'in rcrmaincd ): t .ant.

Langley ie :morial ,':eron,.t ical Laborato-y
ilsticnsl .:rviscrv Ccn-mi.ttee for Aer.onaiutics
Lnllrley Field. Vi.




NACA ACR No. L4H15 Fig. 1


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Fig. 2


Figure 3.- Tank and rails of NACA impact basin.



Fig. 3





i2 *'.* -, i

n H





Fig. 4



Figure 5.- Front view of carriage in NACA impact basin.

Figure 6.- Side view of model fastened to boom in NACA
impact basin.



Figs. 5,6

ai,., -;*`:"~'"


Figure 7.- Front view of model fastened to boom in NACA
impact Dasin.

Figure 8.- Photoelectric-cell interrupters in NACA impact



Figs. 7,8





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--, ... -- ----------


-- ---- ,,,

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P ~~ 1' _____ ^ ______

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Figs. 9,10



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Figs. 11,12


a -


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F' U





Figs. 13,14

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