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= Cessna Skymaster =
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Introduction
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The Cessna Skymaster is an American twin-engine civil utility aircraft
built in a push-pull configuration. Its engines are mounted in the
nose and rear of its pod-style fuselage. Twin booms extend aft of the
wings to the vertical stabilizers, with the rear engine between them.
The horizontal stabilizer is aft of the pusher propeller, mounted
between and connecting the two booms. The combined tractor and pusher
engines produce centerline thrust and a unique sound. The Cessna O-2
Skymaster is a military version of the Cessna Model 337 Super
Skymaster.
Development
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The first Skymaster, Model 336 Skymaster, had fixed landing gear and
initially flew on February 28, 1961. It went into production in May
1963 with 195 being produced through mid-1964.
In February 1965, Cessna introduced the Model 337 Super Skymaster. The
model was larger, and had more powerful engines, retractable landing
gear, and a dorsal air scoop for the rear engine. (The "Super" prefix
was subsequently dropped from the name.) In 1966, the turbocharged
T337 was introduced, and in 1973, the pressurized P337G entered
production.
Cessna built 2993 Skymasters of all variants, including 513 military
O-2 versions. Production in America ended in 1982, but was continued
by Reims in France, with the FTB337 STOL and the military FTMA
'Milirole'.
Design
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The Skymaster handles differently from a conventional twin-engine
aircraft, primarily in that if an engine fails, the plane will not yaw
toward that engine. Without the issue of differential thrust inherent
to conventional (engine-on-wing) twins, engine failure on takeoff will
not produce yaw from the runway heading. With no one-engine-out
minimum controllable speed (Vmc), in-flight control at any flying
speed with an engine inoperative is not as critical as it is with
engines on the wing with the associated leverage; however, performance
in speed and, particularly, rate of climb are affected. Flying a
Skymaster requires a pilot to hold a multiengine rating, although many
countries issue a special "centerline thrust rating" for the Skymaster
and other similarly configured aircraft.
Ground handling requires certain attention and procedures. The rear
engine tends to overheat and can quit while taxiing on very hot days.
Accidents have occurred when the runway is shorter than the
single-engine take-off roll and pilots, unaware of a rear engine
shutdown, have attempted take-off on the nose engine alone. Federal
Aviation Administration Airworthiness Directive 77-08-05 prohibits
single-engine take-offs and requires the installation of a placard
marked "DO NOT INITIATE SINGLE ENGINE TAKEOFF".
The Skymaster's unique sound is made by its rear pusher propeller
slicing through turbulent air from the front propeller and over the
airframe while its front tractor propeller addresses undisturbed air.
Operational history
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From 1976 until the middle 1990s, the California Department of
Forestry and Fire Protection used O-2 variants of the 337 Skymaster as
tactical aircraft during firefighting operations. These were replaced
with North American OV-10 Broncos, starting in 1993.
During the Rhodesian Bush War, the Reims-Cessna FTB 337G 'Lynx' was
the main light attack aircraft used by Rhodesian Security Forces
during Fire Force counterinsurgency air assault missions, which began
in 1974. The Lynxes were armed with twin Browning .303 machine guns
mounted above the wing and 37mm SNEB rockets, locally made Mini
"Alpha" Bombs (cluster bombs), Mini "Golf" Bombs ( blast and shrapnel
bomb) and 'Frantan' (a napalm variant carried in frangible drop tanks)
bombs.
Brothers to the Rescue
========================
From 1991 until 2001 the Cuban exile group 'Hermanos al Rescate'
(Brothers to the Rescue) used Skymasters, among other aircraft, to fly
search and rescue missions over the Florida Straits looking for
rafters attempting to cross the straits to defect from Cuba, and when
they found them, dropped life-saving supplies to them. Rescues were
coordinated with the US Coast Guard, which worked closely with the
group. They chose Skymasters because their high wing offered better
visibility of the waters below, they were reliable and easy to fly for
long-duration missions (averaging 7 hours), and they added a margin of
safety with twin-engine centerline thrust. In 1996, two of the
Brothers to the Rescue Skymasters were shot down by the Cuban Air
Force over international waters. Both aircraft were downed by a
MiG-29, while a second jet fighter, a MiG-23, orbited nearby.
Variants
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'Cessna has historically used model years similar to U.S. auto
manufacturers, with sales of new models typically starting a few
months prior to the actual calendar year.'
;
:Original variant first flown in 1961 and introduced for the 1963 and
1964 model years. The 336 had a six-seat cabin and was powered by two
195 hp Continental IO-360-A engines. Production aircraft differed
from the prototypes in that they had a roomier cabin and a redesigned
rear engine cowling to improve engine cooling and reduce cabin noise.
Gross weight was 3900 lb. A total of 197 built; 2 prototypes and 195
production aircraft (102 in 1963 and 93 in 1964).
;
:The 1965 model year brought major changes to the Skymaster, which led
to a new model number, 337, being assigned. The most significant
change was the addition of retractable undercarriage similar to that
of the Cessna 210 Centurion, which sat four inches lower than the 336
for ease of entry/exit. Other changes included a redesigned nose
cowling and new rear engine intake, greater wing angle of incidence,
shortened ventral tail fins, increased elevator chord, and an
increased gross weight of 4200 lb. The 337 was powered by two 210 hp
Continental IO-360-C or IO-360-D engines. 239 total built; 1
prototype and 238 production aircraft.
;
:1966 model year with canted engine instruments and rotary-type door
latches. 284 built. 31 were later modified to MC337A standard with
loudspeakers and leaflet dispensers for use by the United States Air
Force as the O-2B Skymaster.
;
:1967 model year with improved brakes, 38A alternators, a redesigned
cabin heating system, a split-bus electrical system, and an increased
gross weight of 4300 lb. A version powered by turbocharged 210 hp
Continental TSIO-360-A engines was also offered as the T337B. 231
built, plus 479 M337B military variants as the O-2A Skymaster.
;
:1968 model year with a new instrument panel, improved seat belts, and
an increased gross weight of 4400 lb (4500 lb for the T337C). 223
built.
;
:1969 model year with reduced elevator chord and increased elevator up
travel, electroluminescent instrument panel lighting, and new cowl
flap controls. Also offered as the turbocharged T337D. 215 built.
;
:1970 model year with conical cambered wingtips, a new fuel quantity
system, and an increased gross weight of 4440 lb (4630 lb for the
T337E). 123 built, plus 24 in France by Reims Aviation for the
European market as the F337E.
;
:One aircraft converted from the 20th production F337E.
;
:Introduced for the 1971 model year with an increased gross weight of
4630 lb (same as the T337F) a refined instrument panel, a padded
glareshield, a front engine access panel, and other minor changes.
The 1972 model year introduced nose-mounted landing/taxi lights and
minor interior changes. The turbocharged T337F was only offered for
the 1971 model year. 147 total built; 83 (1971) and 64 (1972). Reims
also built a total of 31 as the F337F; 21 (1971) and 10 (1972).
;
:Introduced for the 1973 model year with a recontoured nose cap, flush
wingtip lights, low-drag front exhaust stack and wing strut fairings,
a flush-mounted pitot port on the left wing strut, a split airstair
door replacing the cabin and baggage doors, aileron gap seals, and a
hydraulic powerpack replacing the engine-driven pump. Power was
provided by two 210 hp Continental IO-360-G engines. The 1974 model
year introduced recessed parking brake control, a hydraulic gear
accumulator, and improved subpanel rocker switches. 1975 introduced
an optional 148 gal auxiliary fuel system and the Skymaster II with a
preferred options package. 1976 introduced a "Camber-Lift" wing, a
redesigned instrument panel, and a reworked fuel system with tail boom
fuel sump tanks removed. 1977 introduced a new front propeller
airfoil and an auxiliary master power switch. A turbocharged version
of the unpressurized 337G was not offered. 354 total built; 88
(1973), 56 (1974), 65 (1975), 77 (1976), and 68 (1977). Reims also
built a total of 29 as the F337G; 8 (1973), 8 (1974), 5 (1975), 3
(1976), and 5 (1977).
;
:Also known as the T337G, introduced for the 1973 model year as a
turbocharged, pressurized version of the 337G. The P337G was powered
by two 225 hp TSIO-360-C engines. Like the 337G, the Skymaster II
option was also available for the P337G. 292 total built; 1 (1971
prototype), 148 (1973), 45 (1974), 31 (1975), 32 (1976), and 35
(1977). Reims also built a total of 22 as the FT337GP; 8 (1973), 5
(1974), 2 (1975), 2 (1976), and 5 (1977).
;
:Military variant of the F337G with Sierra Industries Robertson STOL
modifications and underwing hardpoints. Known as the Lynx in
Rhodesian Air Force service. 61 built.
;
:Introduced for the 1978 model year with redesigned control wheels and
minor interior refinements. The turbocharged version was also offered
after a six year absence as the T337H, which was powered by two 210 hp
Continental TSIO-360-H engines. The T337H-SP was introduced for the
1980 model year and was powered by TSIO-360-JB engines. The 1980
model year replaced the engines of the 337H and T337H with the
TSIO-360-GB and TSIO-360-HB, respectively. 140 total built; 58
(1978), 47 (1979 337H/T337H), 1 (1979 T337H-SP prototype), 24 (1980
337H/T337H), and 10 (1980 T337H-SP). Reims also built 2 aircraft in
1978 as the F337H.
;
:Introduced for the 1978 model year as a turbocharged, pressurized
version of the 337H powered by two 225 hp TSIO-360-C engines, which
were replaced by the TSIO-360-C for the 1980 model year. 64 total
built; 26 (1978), 24 (1979), and 15 (1980). Reims also built 1
aircraft in 1978 as the FT337HP.
;
:Based on the M337B but with two 317 shp Allison 250-B15 turboprop
engines, a longer span wing, and improved high lift devices.
Designated O-2T, only a single prototype was built.
;
:Also known as the O-2TT, a proposed variant of the O-2T with a tandem
two-seat cockpit for the pilot and observer. Only a mockup was built.
;
:Reduced-scale four-seat version of the 337 first proposed in 1965 as
the Model 377 with cantilever wings replacing the 336/337 strut-braced
configuration. The 377 was later redesignated as the Model 327 in
1967 and was first flown in December of that year. One prototype was
built before the project was canceled in 1968 due to lack of
commercial interest in the design. The prototype was delivered to NASA
to serve as a full-scale model for wind tunnel testing. It was used in
a joint Langley Research Center and Cessna project on noise reduction
and the use of ducted versus free propellers.
Conversions/modifications
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;Ampaire Electric EEL
:Hybrid electric aircraft with the forward piston engine replaced by
an electric motor powered by a battery, in a parallel hybrid
configuration. The demonstrator first flew on 6 June 2019, before
Hawaiian regional carrier Mokulele Airlines experiment connecting Maui
airports with the aircraft.
;AVE Mizar
:Flying car, created by Advanced Vehicle Engineers, was an attachment
of Skymaster wings, tail, and rear engine to a Ford Pinto outfitted
with aircraft controls and instruments.
;Conroy Stolifter
:An extensive single-turboprop engine STOL cargo plane conversion of
the Skymaster. Front engine was replaced with a Garrett AiResearch
TPE-331 turboprop; rear engine was removed, and its space filled with
an extended cargo pod.
;Groen RevCon 6-X
:Test conversion of a Cessna 337 Skymaster airplane. This aircraft
conversion tested the theory of using fixed-wing airplanes as the
basic airframes for gyroplanes to reduce cost and shorten development
time.
;Spectrum SA-550
:Built by Spectrum Aircraft Corporation of Van Nuys, California, it
was an extensive single-turboprop engine conversion of a Reims FTB337G
constructed in the mid 1980s. They removed the nose engine, lengthened
the nose, and replaced the rear engine with a turboprop.
;Summit Sentry O2-337
:Summit Aviation of Middletown, Delaware re-manufactured existing used
337 airframes into the militarized O2-337 which includes four
wing-mounted NATO standard pylons capable of carrying 350 lb (159 kg)
each for 7.62 mm and 12.7 mm gun pods, rocket launchers, bombs,
markers and flares. The aircraft was marketed for the target
identification and marking, reconnaissance, helicopter escort and
aerial photography roles. Examples were sold to the Haitian Air Force,
Honduras, Nicaragua, Senegal and the Thai Navy. The variant was still
in production in 1987.
;VoltAero hybrid electric conversion
:VoltAero is a startup company formed in September 2017 by the CTO and
test pilot of the 2014 Airbus E-Fan 1.0. The company has been
established in Royan, with support from the French Nouvelle-Aquitaine
region. It is developing a hybrid electric aircraft testbed based on
the Skymaster, which is intended to fly in late February 2019. It will
be followed up by the VoltAero Cassio prototype in 2020, a
clean-sheet, all-composite design.
References
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*
*Taylor, John W. R. 'Jane's All The World's Aircraft 1969-70'. London:
Sampson Low, Marston & Company, 1969. .
*
[http://www.flightglobal.com/pdfarchive/view/2004/2004-09%20-%202334.html
"World Air Forces 2004"]. 'Flight International', 16-22 November 2004.
pp. 41-100.
External links
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*
[https://web.archive.org/web/20160303193746/https://wingsoverkansas.com/photos/cessna/dm/got-away/Cessna327.jpg
Photo of the Cessna 327 Baby Skymaster]
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Original Article: http://en.wikipedia.org/wiki/Cessna_Skymaster