Cessna Skymaster C337, O-2 & C336: A DRAFT In the Works
- skylarkcolo
- Nov 6, 2017
- 19 min read
Updated: 4 days ago
0-2 Prototype
In 1965, the USAF at Eglin AFB, FL, modified a 336 with four sets of hard points on the wings, and had a one time STC approved by the FAA. The serial number on that plane is 336-0026. It was used a proof of concept to see if the idea was feasable for the 337's to be used as FAC aircraft. The Cessna model 305's (Birdogs) were getting hammered in South East Asia and North American Aviation Bronco's were late in getting into production, so the Air Force was scrambling to find a stop gap aircraft that had the range, load carrying and had multiengine reliability to supersede the birdogs. This 336 eventually became N331KW. At one time it was owned by a Belize national, General Steven Walz who is now living in the USA. Belize Air Force markings V3-1KW registration. Flown at many large airshow in the 1990s as"Miss Belize, The Caribbean Queen". Someone from the British magazine 'Airforces Monthly' saw this aircraft and it was announced in the magazine that the Belize Air Force had an ex-USAF O-2! Even today there is a mention of this aircraft under the Belize Air Force heading in 'Air Forces of the World' and other military reference guides, despite the fact that he has now sold the aircraft and it is now back carrying its true identity (ie N331KW).
The O-2 Skymaster called "Miss Belize, is the above aircraft. The plane had HF/VHF & UHF equipment and was showed in the "Dec 1996 QST magazine and Airforces Monthly". Miss Belize was flown by General Walz (K0UO) in over a 100 USA and Caribbean air-shows, and at numerous US Military Bases Air demonstrations in the 1990s. Note the Belize ham call "V31-KW" is also the Airplane's tail numbers, V3-KW see more photos on QRZ @ the call V31KW.
History of the Cessna Skymaster
The first prototype Skymaster was a basic 4-seat, all-metal, high wing push-pull twin aircraft. The tricycle undercarriage was fixed and had two 175hp Continental GO-300-C geared engines. The prototype was registered N34273 and was given the construction number of 633 (Cessna Experimental Series) and first flew on 28 February 1961.
The tandem twin engine arrangement — which Cessna called Centre Line Thrust — with the nose-mounted tractor engine and rear-mounted pusher engine, mitigated asymmetrical thrust issues in an engine failure, and had the added advantage of more easily allowing for a high-wing configuration for a clear field of view for observation. The U.S. Federal Aviation Administration (FAA) created a new center thrust rating for pilots.
SPECIAL CHARACTERISTICS
The Skymaster has different handling characteristics than a conventional twin-engine aircraft. Foremost is that it will not yaw into the dead engine if one engine quits. Consequently, it has no tendency to depart the runway if an engine fails on the takeoff roll. The adage, “dead foot, dead engine” used to remind a pilot in a twin which propeller to feather when an engine quits. When a Skymaster loses power, the pilot must use the instruments to determine which engine has failed. The Skymaster is also controllable at lower airspeeds than a comparable conventional twin. There is no minimum controllable speed advisory (Vmc) on the airspeed indicator. On the dead engine feather it and close the cowl flap. You lose about 15 mph.
C336: It wasn't until August 1962 that the first production aircraft flew and mid-1963 before deliveries began. Production models of the 336 were different from the prototype by having IO-360 engines, an enlarged cabin to take 6 people, inboard wing sections were redesigned and the vertical tail surfaces were enlarged. TOGW was 3,900lbs. 195 production 336's were built and were given construction numbers of 336-0001 to 336-0195.
On 30th March 1964 the prototype of the 337 first flew, piloted by Dick Kember. Despite it looks being similar to the 336 it was a largely redesigned aircraft. The wing incidence angle was increased, the nose cowling was redesigned, the tail boom angle increased, a new dorsal air intake for the rear engine was added and the 337 had retractable undercarriage. This was the first model called the Super Skymaster. The word Super was dropped in 1972. The prototype was registered N5422E and had the construction number of 647. Production on the 337 started in February 1965. This model has a TOGW of 4200lbs and IO-360C engines. The cost of a new 337 would be around $39,950. A new construction number series was started for the 337. These basic models had construction numbers between 337-0001 and 337-0239.
In 1966 the 337A was produced. This had minor changes to the standard 337 and construction numbers in the range 337-0240 and 337-0525. There were 286 of them built.
1967 saw the 337B. TOGW was increased to 4,300lbs and there was an optional belly cargo pack. A further option on this aircraft was a turbocharged 210hp TSIO-360-A engines. The price for a T337B in 1967 was $49,500. Construction numbers for the 337B and T337B went from 337-0526 to 337-0755 and there were 230 of them built.
1967 also saw the building of a reduced scale version of the 337. This was known as the 327. Only one aircraft was built and first flew on 4 December 1967. It was registered N3769C and had a construction number of 663 (Cessna Experimental Series). This aircraft later went to NASA as a 'full scale wind tunnel research unit'.
O2, In 1967 the USAF placed an order for Skymasters. Two variants saw action the O-2As for FAC missions and O-2Bs for psychological operations.The military designation for theses aircraft was O-2A. They had their own construction number sequence starting at M0001. The USAF also took 32 aircraft from the civil production lines. These retained their civil construction numbers and were fitted with loud-speakers and leaflet dispensers for psychological warfare duties. They were also different from the O-2A's by not having hard-points under the wings.
First flights took place in 1967 and the U.S. Air Force took its first deliveries in March of that year. The aircraft had a crew of two: pilot and observer. It was fitted with two Continental IO-360-C fuel-injected, flat six-cylinder engines. Among other possible considerations, the “push-pull” design allowed for a simpler one-engine operating procedure and a high wing mount for better visibility (and the handling characteristics should an engine fail).
The main differences between the 337 and the O-2 included the removal of the cabin step and spinners on the propellers, addition of observation windows in the cabin door and roof of the cabin. Engine fire detection equipment were added together with smoke generator equipment added to the rear exhaust system. The instrument panels were also different and they had an armament switches panel installed. Four underwing pylons for rockets, flares and cluster bombs. Military reconfiguration of Skymasters added observation windows, 7.62mm miniguns, LAU-59/A pods holding Folding Fin Aircraft Rockets, armored seats, self-sealing fuel tanks, and stronger landing gear.
By Randy Malmstrom
Since his childhood, Randy Malmstrom has had a passion for aviation history and historic military aircraft in particular. He has a particular penchant for documenting specific airframes with a highly detailed series of walk-around images and an in-depth exploration of their history, which have proved to be popular with many of those who have seen them, and we thought our readers would be equally fascinated too. This installment of Randy’s Warbird Profiles takes a look at the Heritage Flight Museum’s Cessna O-2A Skymaster.
Cessna O-2A Skymaster, Nicknames for the aircraft type included “Oscar Deuce”, “The Duck”, “Mixmaster”, “Push-Pull”, “Cessna Suck-Blow”, or “The B.S. Bomber” (for the O-2B psychological warfare — PSYOPS — variant). In 1966, the U.S. Air Force commissioned Cessna Aircraft Company for an observation and close air support aircraft. The O-2 was based on the civilian Cessna 337 Super Skymaster (the 336 Skymaster was introduced in 1961) and had fixed landing gear and a smaller engine; the 337 was fitted with a more powerful engine and retractable landing gear, and the “Super” was later removed from the name.
First flights took place in 1967 and the U.S. Air Force took its first deliveries in March of that year. The aircraft had a crew of two: pilot and observer. It was fitted with two Continental IO-360-C fuel-injected, flat six-cylinder engines. Among other possible considerations, the “push-pull” design allowed for a simpler one-engine operating procedure and a high wing mount for better visibility (and the handling characteristics should an engine fail).
Armament included: an SUU-11/A 7.62 mm Minigun pod, rocket pods on fixed underwing hard points to deliver smoke rockets, bombs or flares for defensive purposes or to designate targets for air strikes. The crew could carry machine guns and grenades.
Amour plates were installed under the seats and porous foam slabs were place in the fuel tanks during assembly to make them explosion-resister after being hit by small arms fire. This resulted in about a 5% loss in fuel capacity.
Among others, the O-2 was flown by the U.S. Air Force, U.S. Navy, U.S. Air National Guard, and many militaries and civil air guards flew them including the South Vietnamese Air Force. During the Vietnam War, the O-2 was seen as a replacement for the O-1 Birddog. The O-2A flew Forward Air Control (FAC) missions for the 20th Tactical Air Support Squadron. The O-2B variant was equipped with loudspeakers and a leaflet dispenser for use in the psychological operations (PSYOPS) role.
Vietnam: The U.S. military introduced O-2s into Vietnam beginning in May 1967. This first required getting the aircraft to Asia, which was not a straightforward process. Civilian pilots flew O-2s in flights of four from Cessna’s Wichita, Kansas, plant to Hamilton AFB in California. At Hamilton, the Air Force removed all the seats except the left front and installed extra fuel and oil tanks and an emergency radio. Still flown by civilians, these aircraft island-hopped from California to Vietnam, with flight leaders earning $1,000 and other pilots $800 for the trip, plus airfare home. The Hamilton-Hawaii leg was the longest at about 13 hours flight time; fuel aboard provided for about 14.5 hours of flight, leaving a small margin for navigational error.
O-2B (Cessna 337A)
Some dozen civil Cessna 337s were converted to O-2B, with loudspeakers under the right aft cabin window, a leaflet dispenser, a large blade antenna above the cockpit and a half-loop antenna above the front windows. In many cases they lost the propeller spinners. Unlike the O-2A, the O-2B has no underwing pylons and no windows in the bottom of the right cabin door.
Among others, the O-2 was flown by the U.S. Air Force, U.S. Navy, U.S. Air National Guard, and many militaries and civil air guards flew them including the South Vietnamese Air Force. During the Vietnam War, the O-2 was seen as a replacement for the O-1 Birddog. The O-2A flew Forward Air Control (FAC) missions for the 20th Tactical Air Support Squadron. The O-2B variant was equipped with loudspeakers and a leaflet dispenser for use in the psychological operations (PSYOPS) role.
U.S. Air Force records indicate that a total of 178 of its O-2s were lost in the Vietnam War.
The O-2 may have been flown in war with up to 5600LBs, later some of the 336 & 337 Skymasters have had issues regarding wing attachment points and Cessna promulgated a Supplemental Inspection Document (SID) for “relatively involved” inspection procedures
The 337C came in 1968 with a new instrument panel and 4,400lb TOGW (4,500lb on T337C)
Minor changes were made in 1969 to produce the 337D. Construction numbers in the range 337-0979 to 337-01193 with a total of 215 built.
Cambered wing tips plus other minor changes came on the 1970 337E. T337E's has a TOGW of 4,600lbs, construction numbers between 337-01194 and 337-01316 and a total of 123 built.
The 337E was the first Skymaster model to be re-built in France by Reims Aviation. Reims Aviation started life as Avions Max Holste in 1933. Due to financial stresses Cessna acquired a 49% shareholding on 16th February 1960. Reims started building Cessna aircraft from kits supplied from the USA for the European and Middle Eastern markets. Skymasters re-built by Reims have both Cessna and Reims Construction numbers.
The 1971/2 337F model had 4,630lbs TOGW for both non-turbo and Turbo models. Construction numbers of 337-01317 to 337-01462 were on these 146 aircraft.
In 1973 the 337G emerged. This had split airstair entry door, smaller rear side windows, improved flaps, larger front propeller, modified wing struts and Cont. IO-360-G engines. Production of this model continued until 1977 by which time 353 had been built with construction numbers in the range 337-01463 to 337-01815.
A Turbo charged version of the 337G was produced in 1974. This model also had a pressurised cabin and redesigned windshield. A new construction number sequence was started for these aircraft.
With the Cessna 337G introduced in 1973 the fuselage looks a bit different. First of all, the cabin windows were reduced in size, in particular the two rear ones. Secondly, the vertically hinged cabin door on the right is now split horizontally, opening up and down. The lights in the wing tips are larger than previously, and flush with the tip contour. Other differences are much smaller and difficult to see.
The Cessna 337H is externally not different from the G model.
Between 1978 and 1980 the 337H models were produced in three forms ie 337H (normal) T337H (Turbo) and P337H (Pressurised cabin). Cost for these aircraft were $124,090 for the standard model and $140,890 for the turbo model.
P337H Pressurized Skymaster
Introduced for the 1978 model year as a turbocharged, pressurized version of the 337H powered by two 225 hp (168 kW) TSIO-360-C engines, which were replaced by the TSIO-360-C for the 1980 model year.[13][14] 64 total built; 26 (1978), 24 (1979), and 15 (1980). Reims also built 1 aircraft in 1978 as the FT337HP.[16][17][18] These aircraft were referred to as "
" on the Federal Aviation Administration type certificate, but were given "P337" construction numbers by Cessna. The four nearly square cabin windows are the key to recognise the pressurised Skymasters, like this Cessna P337G.
Production of the Skymaster by Cessna finished in 1980. However Reims Aviation of France was assigned world-wide marketing rights to the aircraft, and as a result they built (from scratch) a further 61 aircraft, which it called the Reims FTB337 Minirole. Most of these aircraft went to military operator in Europe and Africa. The Portuguese Air Force taking the most.
n 1969, Reims Aviation in France began licence assembly of the Model 337, with primary structures supplied by Cessna and Continental engines built in the UK under licence by Rolls-Royce. The US and French production lines continued in parallel, the French versions being classified Reims F337. The name Milirole was applied to the basic unpressurised F337 for a short time. Since 1974 Reims have developed a special unpressurised STOL version, designated FTB337, which can be provided with a wide range of equipment to make it suitable for such duties as maritime or overland patrol and rescue. Detail improvements continued each year, and a turbocharged version, the Model 337 Turbo-System Super Skymaster, was introduced in 1970, but the prototype of a pressurised T337 Skymaster, powered by 168kW Continental TSIO-360 engines, flew in July 1971 (the word Super had then been dropped), and deliveries began the following May.
Reims Cessna
F337E Super Skymaster, 24 built.
F337F Super Skymaster, 31 built.
F337G Super Skymaster, 29 built.
FT337G Super Skymaster, 22 built.
F337H Super Skymaster, 1 built.
FP337H Pressurized Skymaster, 1 built.
FTB337G Milirole; military F337G with Robertson STOL modifications and underwing hardpoints, 61 built.
Lynx : Rhodesian designation for 21 FTB337Gs delivered to the Rhodesian Air Force.
The Skymaster lives on: Even with production of the Skymaster finished that is not the end of the story. A modification to the pressurised 337's was first undertaken by Riley. This modification consisted of adding a Riley intercooler to pump cooler air from the turbochargers into the aircraft's engines that greatly improved the aircraft's performance. STOL modifications to the wings, air conditioning, comprehensive avionics package, new paint scheme and a custom interior were also part of the deal. This 'new' aircraft was dubbed the Riley Skyrocket. Riley also tried to launch the Super Skyrocket but unfortunately, went out of business before FAA approval came forth for this new modification. However, LLC of Carlsbad, California has now obtained the necessary approval and is now modifying P337's. This modification consists on installing two turbocharged 310hp Continental TSIO 520 engines, with intercoolers.
Cessna 327 Baby Skymaster
Cessna thought there was a market for a four seat version of the model 337. Hence it developed model 327. Apart from being smaller, the Cessna 327 has cantilever, non-braced wings as main external difference. Unfortunately for Cessna, there was no commercial interest, to just one was built.
In addition to 1859 standard and 332 pressurised 337s, Cessna built 513 military O-2 versions, largely for Forward Air Control, for the US Air Force.
O-2T (Cessna 348)
The US military had plans for an improved version of the O-2, with turboprop engines and a tandem cockpit. One O-2A was converted to the O-2T concept aircraft, receiving Cessna model number 348. This has the turboprop engines, but not the redesign fuselage. The front cowling with exhausts in the left and right bottom corners is the main external difference compared to the regular O-2.
After Cessna production ended in 1980, development continued with Reims, in France, with the FTB337 STOL and the military FTMA Milirole. Reims of 94 aircraft .FTB337G
Military variant of the F337G with Sierra Industries Robertson STOL modifications and underwing hardpoints. Known as the Lynx in Rhodesian Air Force service, 61 were built.
French production by Reims Aviation totalled 66 Model F337s, 27 F337Ps and 61 FTB337s.
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.[4]
This conversion turns a standard civil Cessna 337 more or less into an O-2A. Like the O-2A the Summit Sentry O2-337 has four pylons under the wings, a blade antenna and half loop antenna on top of the fuselage and observations windows on the right side. You can only distinguish it from the real O-2A if the rear window arrangement of the original 337 is retained.
AirScan upgraded some to a big bore 300-325 hp continous hp continental. With 450 fpm enhance cruise and 20kts increase cruise with only 2 gallons more fuel per hour. Airscan now A2G had up to 25 Skymasters, mostly G & H models. They have their own GW increase STC for their aircraft and they had to do a drop test. Using IO-550-N engines, Hartzell Model PHC-G3YF-2UF/F7663D-2R propeller front, Hartzell Model PHC-I3YF-2AL/FLC7663DF-2 propeller rear, front and back AirScan engine installations and 5120 pounds Maximum Gross Weight
AirScan now A2G Modified IO-550 Cessna 337G & H Super Skymaster
General Characteristics
Capacity: 3 passengers
Length: 29 ft 9 in (9.07 m)
Wingspan: 38 ft 09 in (11.81 m)
Height: 9 ft 4 in (2.84 m)
Wing area: 201 sq ft (18.7 m2)
Fuel capacity: 92 US gal (77 imp gal; 350 L) normal, 128 US gal (107 imp gal; 480 L) with auxiliary tanks
Powerplant: 2 × Continental IO-550 air-cooled flat-six piston engine, 300 & 310 hp (224 & 231 kW) each
Propellers: 3-bladed McCauley fully-feathering, constant-speed propeller, 6 ft 4 in (1.93 m) diameter
The A500 is powered by twin Teledyne Continental TSIO-550E engines. It is a fuel-injected six-cylinder air-cooled horizontally-opposed piston engine which produces a maximum takeoff thrust of 350 horsepower each. The aircraft has a maximum speed of 225 knots and a cruise speed of 220 knots. The stall speed is 75 knots in landing configuration with gear and flaps down. It has a range of 892 nautical miles at 75% power and a ferry range of 1,286 nautical miles at 45% power. The aircraft has a maximum certified service ceiling of 25,000 feet and 14,900 feet on one engine. The rate of climb is 1800 feet per minute.
Airscan had some of these ordered
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, who worked closely with the group. They chose Skymasters because their high wing offered better visibility of the waters below, were reliable and easy to fly for long duration missions (average 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 (FAC) over international waters. Both aircraft were downed by a MiG-29, killing four people in the Skymasters, while a second jet fighter, a MiG-23 orbited nearby. Watch the 2006 film "Shoot Down" and the 2019 "Wasp Network" starring Penelope Cruz.
V31KW, uses an internet remote station, that station is at the Belize Defense Force base, Ladyville Belize (INTL. Airport). V31KW can also run AIRMOBLE HF-70cm.
Variants
Cessna
327 Baby Skymaster - reduced scale four-seat version of the 337, with cantilever wings replacing the 336/337strut-braced configuration. It first flew in December 1967. One prototype was built before the project was cancelled 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.
336 Skymaster - production version powered by two 195 hp (145 kW) Continental IO-360-A engines, 195 built.
337 Super Skymaster - 336; retractable undercarriage, redesigned nose cowling and new rear engine intake, and greater wing angle of incidence, powered by two 210 hp (160 kW) Continental IO-360-C engines, 239 built.
337A Super Skymaster - 337; minor detail changes, 255 built.
337B Super Skymaster - 337A; increased take-off gross weight, optional belly cargo pack, 230 built.
T337B (1967) Turbo Super Skymaster - 337B; two Continental turbocharged fuel injected 210 hp (160 kW) engines which boosted service ceiling to 33,000 feet (10,000 m), cruise speed to 233 mph (375 km/h), and range to 1,640 miles (2,640 km)
337C Super Skymaster - 337B; new instrument panel and increased take-off gross-weight, 223 built.
337D Super Skymaster - 337C; minor detail changes, 215 built.
337E Super Skymaster - 337D; cambered wingtips and minor changes, 100 built.
337F Super Skymaster - 337E; increased take-off gross weight, 114 built.
337G Super Skymaster - 337F; split airstair entry door, smaller rear side windows, improved flaps, larger front propeller, powered by Continental IO-360-G engines, 352 built.
P337G Super Skymaster - 337G; pressurized cabin and turbocharged engines, 292 built.
337H Skymaster - 337G; minor changes and optional turbocharged engines, 136 built.
P337H Pressurized Skymaster - T337G; minor changes, 64 built.
337M - US military version designated O-2 Skymaster in service, 513 built.
O-2A - US military designation of the 337M Forward air control, observation aircraft for the US Air Force. 501 delivered to the USAF and 12 to the Imperial Iranian Air Force
O-2B: Psychological warfare version for the US Air Force (31 former civil aircraft were converted to O-2B).
O-2TT: Twin turboprop-powered version of the O-2.
Summit Sentry O2-337 : Military version.
Lynx: Armed military version for the Rhodesian Air Force.
T337H-SP
Reims Cessna
F337E Super Skymaster, 24 built.
F337F Super Skymaster, 31 built.
F337G Super Skymaster, 29 built.
FT337G Super Skymaster, 22 built.
F337H Super Skymaster, 1 built.
FP337H Pressurized Skymaster, 1 built.
FTB337G Milirole; military F337G with Robertson STOL modifications and underwing hardpoints, 61 built.
Lynx : Rhodesian designation for 21 FTB337Gs delivered to the Rhodesian Air Force.
A total of 178 USAF O-2 Skymasters were lost in the Vietnam War, to all causes.[5]
Following the Vietnam War, the O-2 continued to operate with both U.S. Air Force and Air National Guard units into the late 1980s.
U.S. Navy
Six former USAF O-2A airframes were transferred to the U.S. Navy in 1983 for use as range controllers with Attack Squadron 122 (VA-122), the Pacific Fleet Replacement Squadron for the A-7 Corsair II at Naval Air Station Lemoore, California. These aircraft were later transferred to Strike Fighter Squadron 125 (VFA-125), the F/A-18 Hornet FRS at NAS Lemoore, in 1986 for use in the same range control role.[6] These O-2A aircraft were eventually replaced by T-34C Turbo-Mentor aircraft transferred from the Naval Air Training Command.
U.S. Army
Of the six USN aircraft mentioned above, two were transferred to the U.S. Army in late 1990.[6] USAF O-2As were augmented by the 1990 aircraft transfer from the Navy. Several disassembled USAF O-2s remain in storage at Davis-Monthan AFB, Arizona.[6] Two O-2As were used at Laguna Army Airfield, Arizona as part of testing programs carried out by the Yuma Proving Ground. These were retired in October 2010 and sent to a museum.[7]
Military Operators
Belize
Paraguay: Paraguayan Air Force One 337RG
Portugal: Portuguese Air Force (32 FTB-337G)
These aircraft were bought in 1973 to replace the force's aging Dornier Do 27 fleet, intensively used in the Portuguese Colonial War, but the first deliveries did not arrived until December 1974 - after the end of the war. The last Skymaster in service with the Portuguese Air Force was retired on July 25, 2007.
Skymaster with Vance and Delaney Allen, & Dad Steve Walz at 4KS airport 
Miss Belize the Airplane QST Dec 1996 writeup 
Kennedy Walz at 4KS airpot in the Skymaster 
Gavin Ross Allen 
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