AIRCRAFT CIRCULARS
NATIONAL ADVISORY COMMITTEE FOR AEROIAUTICS
No. 168
SPARTAN tICRUISER I? COMMERCIAL AIRPLANE (BRITISH)
A Six-Seat Low-Wing Cantilever Monoplane
Washington
August, 1932
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
AIRCRAFT CIRCULAR NO. 168
SPARTAN "CRUISER" COMMERCIAL AIRPLANE (BRITISH)*
A Six-Seat Low-Wing Cantilever Monoplane
A six-seater which has recently made its appearance
is the new three-engine monoplane produced at Cowes by
Spartan Aircraft, Ltd., and to be known as the Spartan
"Cruiser." (Figs. 1, 2, and 3.)
Fitted with three De Havilland "Gipsy III" inverted
engines, the "Cruiser" carries, when equipped for passen-
ger work, five passengers in addition to the pilot. This
represents a power of 72 horsepower per paying passenger,
which cannot be regarded as excessive in view of the good
performance of the airplane. When the cabin furnishings
are removed and the "Cruiser" used as a freight carrier,
the pay load becomes 1,000 pounds, or 2.78 pounds per
horsepower, for an endurance of 6 hours and a cruising
range of approximately 700 miles. If the range is short-
ened, the pay load is, of course, correspondingly increased,
As the airplane has been designed to, and actually does,
fly on any two of its three engines, it should cruise at
a power expenditure low enough to ensure that engine fail-
ure should be almost unknown, and forced landings to all
intents and purposes eliminated.
The ratio of gross weight to tare weight is always
worth examining, as it represents to some extent the
"structural efficiency" of the aircraft. For the Spartan
"Cruiser" as a passenger airplane the ratio is 1.53, and
for the freight carrier it is 1.65.Both figures must be
regarded as good, and indicate that considerable engineor-
ing skill has been brought to bear on the structural design.
The aerodynamic efficiency also appears to be above
the average. The Evening "high-speed figure" 'fl/2kD
has a value of 20.25, which points to a very low minimum
drag coefficient. In appearance the "Cruiser" is certainly
"clean," and the performance indicates that there is good
*From Flight, July 22, 1932.
2 N.A.C.A. Aircraft Circular No. 168
scientific foundation for this 'impression.
Thecabin of the."Cruiser" is very well arranged, with
comfortable seats along the sides, a good view through
windows in the sides, and excellent lighting through the
side windows and the roof lights.
FUSELAGE
The fuselage is of metal construction throughout,
and follows closely in principle, althotigh not, of course,
in actual' shape, the hulls of the "Saro" flying boats.
Aseries of light frames give the fuselage its transverse
sections, while the planking or covering is of A].clad,
stiffened by longitudinal corrugations spaced several
inches apart. The p lanking is riveted to the frame flanges.
THE WING
The cantilever monoplane wing is of all-wood construc-
tion, with two main spars of box section, having spruce
flanges and three-ply sides. The wing ribs have spruce
flanges and three-ply webs, and the covering is a three-
ply skin which assists in providing torsional stiffness.
Near the fuselage the wing covering is thickened and stiff-
ened to form a walkway to the cabin door. An aileron crank
with its fairing is shown in Figure 4.
TAIL UNIT
The complete tail unit is a d.uralumin structure cov-
ered with doped fabric. The rudder and elevators are pro-
vided with horn balances, and tail trimming is by a screw
jack operated by a wheel in the pilot's cockpit.
POWER PLANT'
The three De Iavilland "Gipsy III" engines are mount-
ed. two in the wings and One in the nose of the fuselage.
(Fig'. 5.) If desired., alternative types can..be fitted
provided they are of reasonably the. same power and general
type. The engine mountings are of steel tube construction
(fig. 6) and the wing engines are faired' carefully into
the wing surface. As the central engine is rather high
N.A.C.A. Aircraft Circular No. 16
above the ground, it has been fitted with hand-turning
gear. The outboard p ropellers are within reach from the
ground, and the outboard engines are therefore started by
swinging the propellers. . .
FUEI SYSTEM .
There are two main gasoline tanks, rliOd wing
between the main spars, each
wing just behind its engine. Each tank haa capacity of
60 gallons (273 liters), which gives the airplane an en-
durance of six hours at an economical cruising speed of
110 m.p.h.-. When the airplan i's used-'as ápassenger car-
rier the tanks will not normally be filled up, but will
contain enough fuel foraboiitfourours cruising. The
tanks are interconnected with larg 'e balance pipes. Each
engine is pr6vided with a fuel timp which feeds direct to
the carburetor. In the event of a pump failing, a cross
connection is arranged whereby the engine is supplied by
another pump. Fuel content gauges are fitted to each tank.
LUBRICATION SYSTEM
The oil tanks are placed. in the fairings behind. each
engine. (Figure 7.) • .
LANDING GEAR
The landing gear is of the ht split tt type and has a wide
track (10 feet). The telescopic strut, which riinso the
under side of the front spar, is of the "oil-cum-steel"
spring type. The bent axle hinges on the centerline of
the bottom of the fuselage in line, with the front spar,
while the radius rod runs to the rear spar. The tail wheel
structure is shown in Figure 8.
CONTROLS
Elevator and ailerons are operated , by a hand wheel
on a hinged column, while the rudder control is a para].- .
-lemotin,easlydjustable r.Fomthepilo'scn-
trols to the various control surfaces the run-through the
airplane is by rods and cables. Engine controls are con-
veniently placed, and operate through rods and torque
shafts.
4 N.A.C.A. Aircraft Circular'Nô.l68
CABIN ARRANGEMENT
The fuselage is sufficiently wide to permit of plac-
ing the seats along the sides, with a gangway down the
center of the cabin. Pour of the seats are placed between
the wing spars, while the pilot's seat (on the port side)
and that of the fifth passenger are in front of the lead-
ing edge of.the wing. The windows in the sides of the
cabin are of triplex, while those in the roof are of cel-
luloid. The side windows are made to slide for ventila-
tion purposes.
Behind the cabin is a large stowage space-for luggage.
The main dirnensions, areas- etc., are shown on the'
three-view general arrangement drawings, and . the 'charac-
teristics have been collected in the following table.
CHARACTERISTICS
Dimensions:
.Wing span 54 ft. 0 in. 16.45 m
Length, over-all 39 " 2 11.9 u
10 " 0 " 3.05 U
Height, over-all
Area:
Wing 436.0 sq.ft. 40.5 rn
Ailerons 40;3 " 374 II
Stabilizer 30.5 2.84 II
Elevators 31.5 u 2.93 II
1260 " 1.11 II
Pin
Budder 20.0 I
1.86
N.A.C.A. Aircraft Circular No. 168 5
CHARACTERISTICS (cont'd.)
Weights (passenger airplane)
Tare 3,400 lb. 1,545 kg
77 ft
Pilot 170
Five passengers 850 386
Luggage 100 " 45 'I
Fuel for 4 hours 600 " 273 "
Oil 70 u 32
Loaded weight 5,190 2,358 U
Weights (freighter)
Tare 3,320 " 1,508
Pilot 170 " 77 9
Freight 1,000 " 455
" 410 it
Fuel for 6 hours 900
75 l 34 9
Oil
Loaded weight 5,465 ' 2,485
PERFORMANCE
Maximum speed 135 m.p.h. 217 km/h
Cruising " 110 It
177
Initial rate of climb 600 ft./min. 345 ni/s
Ceiling 13,000 ft. 3,960 m
When fully loaded, the airplane will not only maintain
height, but will climb with either of the three engines.
stopped.
N.A.C.A. Aircraft Circular No. 168 Fig. .1
let 39! 2" —
jr-
----
101214 ft.
k- 10101L
7'8 ' 11 1-c - 148"-_.-__-_>l<-4'l0 (1
-jI
MUNAM LO
Wing area 436.0 sq.ft.
Aileron area 40.3 IT It
0
Stabilizer area 30.5
Elevator area 31.5
Fin area 12.0 11 II
Rudder area 20.0 H
3 Gipsy III engines
Fig. 1 General arrangement drawing
of the Spartan "Cruiser" airplane.
The circles in the plan view are roof
lights and not seats.
N.A.C.A. Aircraft Circular No. 168. Pigs. 293
J
CU
11.
LA.C.AS Aircraft Circular No. 168. Pigs. 4,569798
One of the wing
engine mountings Pig. 5 A wing engine
installation
Pig. 7 oil
tank
of wing engine
mounted in
fairing behind
the engine.
/
-/
An aileron crank
and its fairing.
i/I \
Pig. 8 The tail wheel,
which is sprung
and swivelled, the aidways
movement being limited by
rubber buffers.
6
