Project Sign Progress Report, 1948

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

--
10
282
'
THE AEROPLANE
and _pseudo-circular and pseudo-square wings thus exhibit
~ignificam d.fferences... 1 his also applies to the ground eff.:ct,
1.e., tbe tand.ng <juahues.
1 he prov1s.on 01 ob11que nozzle­
shaped slots at the lips yielded no useful r.:sults.
In any case,
squo1re-cut tips Vvere found to be a disadvantage, w11h respect
to drag, as well as to other qualities.
Later N.A.C.A. research by F. E. Weick and Robert Saundefs
referred to aspect ratios of the order of 3 1n conncct,on w11h
slotted auxiliary Vevions flaps for the trim of tailless aeroplanes.
This constituted the first investigation of what has b.x:ome
known to-day as the .. Delta Wing.'' i.e., the combination of
sweep-back with low aspect ratio.
Such shapes are of special
interest for aeroplanes capable of flying through the trans-sonic
region.
•
Pancakes Ii la Zimmermann
The results of Zimmermann's research were so ~onvincing
that a number of otherwise quite respectable designers were
tempted into experimentation with disc-wing aeroplanes.
In
accordance with Zimmermann's views, all these designs were
intended to be of the safety-first type of privately owned
aircraft.
This distinguishes the early phase from the more
recent interest in Flying Saucers.
In '1934 Farman was stimulated into experimenting with a
wing with an aspect ratio of only 1.9.
1 his was seen in his
F-1020 monoplane which otherwise had a long fuselage with
a conventional tail.
It was said to have proved very stable
in flight. but was noc further heard of.
An experimental
parasol monoplane with a completely circular win$, a camber
flap in the trailing edge and severely skewed ailerons Wl?.$
tested in the U.S.A. (in 1934), with indifferent results.
It was
shown in flight in news reels.
At about the same time Raoul J. Hoffmann. of St. Peters·
burgh, Florida, an eminent aeronautical engineer of Austrian
origin (known as the first to prove-in 1913-that the r:itio
C '/C 9
governs optimum climb and glide with minimum
L
D
sinking speed, took up development of the disc-wing aeroplane.
Hoffmann's Flying Saucer was a tailless aircraft with an
aspect ratio of slightly over 2.
The fi rst type was an ultra·
li$ht single-seater with 36 b.h.p. Later a side-by-side two-seater
with an 85 b.h.p. Cirrus engine was constructed and flew well;
the wing tips served as ailerons and the elevators formed part
of the trailing edre.
The aerofoil sectir,ns employed were
N.A.C.A. M.6 basically. with N.A.C.A. M.1 at the tips. Both
are sections designed by.M. M. Munk. The former is a reflexed­
camber section with a practically stationarY, centre of pressure;
the latter is symmetrical
The central structure of the wing, the fuselage and the fin
was of welded-steel tube; the wing had three spars.
This
little two-seater }"as stated to fly well and to exhibit ve_ry go(!d
stability.
It seems, however. that the controllab1hty, m
particular directionally, was not satisf~ctory.
1 he visi(?n fr(?m
the cockpit must have been very restncted--a moot point wllh •
all these designs.
A speed range from 28 m.p.h. to 13S m.p.h.
was claimed.
The empty weight was given as 900 lb •• and the
wing loading was 5.5 lb. / sq. ft.
One remarkable characteristic observed during the flying
tests of Hotrmann's aircraft was that, when comin(! in to land.
the approach was steep: yet prior to the fl lltening out and
just before touching down, the glide flattened.
1 his would
l MAJ(
C
jc
Cl MA.(
0 MIN
r­
0 MIN
,001----.U---4---1---4----4-----+---~
CI..Akl( T AUl,OfOtL SfCTl()N
C,.ACA • IP No u,)
z
;•f
..,
.,,.
~
60
~
J
::,., l5
r " •
"< .. "
fl"
It .
!i "'
z
J
~ •>
• It
~
"
It
ti
0
11f
2
10
z
c!, "
~
6
t i;
AA
o·
•
ASP(Cf U flO ( •' 1J
Fig. 117.-These resulu from Zlmmermann's wind-tunnel
tests on disc; wings (1932) clearly show the character!stits
of low aspect ratio aerofoils.
•
MARCH 5, 1948
c:,_
i
g:
0
10
"<
Cl ARK I AEAO FOtl SECTION
"'
0
(i-v-CA
ZIMME~MANN,
..
~l P No ()1)
:;
o'----~---L---JL_.__..L.__...L._......:~,
ASPECT AATIO
., .,
18.-Furthcr results from Zimmermann's tesu shown here
also indicate the advantages to be gained from disc wings.
seem to. contradict the experience referred to above and it
w~s aunbuted. to. a ground effect arising from the rak~ of the
wing-tips.
It 1s indeed rea:.onable to e)(pcct that the presence
of t_he ground would affect the formation of the marginal
vort1c~s to an ex\ent which may markedly influence the
beh~v1our of disc wings during take-off and landing. Hoffmann
proJected a ousher and a twin-engined version but these types
did not materialize.
•
A
further development was the Arup monoplane of
R: J. Hoffmann and C._L: Snyder at South Bend, Indiana. The
w!ng _shape ~as v~ry s1m1lar.
I~ resembled a semi-circle flying
w11h 11s straight side a_s the_leading edge; to this wing, ailerons
were added as special ups.
1 he aspect ratio practically
corres~onded to. that of the previous Hoffmann types.
Again,
aerofoils wtth little centre-of-pressure travel were used.
1 he latest type ~ad it~ _tailplane and elevator separately
locate~ over the wing tr:11lmg edge (similar to the .. Elytro·
plane
of De Rouge!).
It seems that the longitudinal control
at certain incidences was not satisfactory.
1 he ailerons which
formed part of the wing shape and reduced the aspecl ratio
to a value ~f I: 15 had a triangular shape and were greatly
s_kewed (taking_ into account the obliqui: flow over the wing
tips). The engine was a 70 b.h.p. Le Blond radial; a tricycle
undercarriage was fitted.
With the oilot alone, a gliding speed of 23.S m.p.h. was
r~o_rded (lhe wing loading was about 3.3 lb./sq. ft.) and a
gliding angle of 21 degrees was mea~ured, with a sinking speed
of 12.3 ft. ocr si:cond. wh.ch ~an be accommopated by a sturdy
undercarriage without nattening out of the glide.
1 he maxi·
mum speed was 86 m.p.h .. and the take-off was stated to require
S secs. in zero wind.
Several more Arup types seem to have been constructed
an_d _flown during 1935.
1 h~ flying qualities were pr.iised­
ghding angle~ or I : 2.6 bemg quoted- and the published
performance figures sounded extremely good.
Yet, for reasons
never disclosed, the production stage was not reached and the
development ceased abruplly.
It is worth noting that Charles
Zimmermann himself has taken no part in this development,
b1;11 he was an interested spectator at demonstration flights
wnh an Arup monoplane at Langley Field.
An Italian "Tortelllno "
At the time .of the Arup development (1934). F. Piana
Canova. an Italian, began to embark on a development for a
tajlless aeroplane with a low aspect ratio.
In May, 1935, he
secured patents for a rhomboidal wing, one diagonal of which
coincided with the direction of flight.
1 he ailerons were to
be located at the lateral apices. elevator and rudder at the
rear apex. while the airscrew was in front of the leading apex.
Another patent related to bi-convex aerofoils with ducts and
control valve~ for the pilot, enabling the latter to neutralize
the negative oressure on the forward ventral surface when at
negative incidences.
The latter patent was, apparently, never
submitted to flight experiments.
NND 927545
(To ~ confin~d.)