Tuesday, July 15, 2014

The Cessna 336, 337, O-2 Skymaster

First flown on February 28, 1961 the Cessna 336,  November 34373 had a fixed undercarriage. A high wing typical of Cessna aircraft with strut bracing.   A center pod fuselage holding the two engines.   The 336 originally flew with two 175 horsepower Continental GO-300-C  geared engines.  One engine was  in a Tractor configuration in the nose, the other in a pusher in the rear of the pod.  Two booms were extended from the wings to form parallel tails with a horizontal surface fitted between.
The 336 could hold a pilot and three passengers and was initially conceived as an air taxi.   The 336 officially went into production in May of 1963.  The Production 336 had a larger passenger pod capable of holding Five plus the pilot.   The engines became Continental IO-36Os which could generate 260 horsepower each.
Flying a Skymaster is different than flying other multi or single engine aircraft.   If you lose an engine in a multi-engine aircraft the aircraft will yaw into the failed engine.  This is not the case in a Skymaster.    It is important to understand engine out failures are different and sometimes hard to detect because both engines are on the same thrust line.   The Skymaster requires usually a Multi-engine rating or some countries issue a “Centerline thrust rating” for the 336/337.
The 336 and later 337 rear engine was notorious for overheating..   In Hot and High climates the rear engine can quit on Taxi.  The same can be said about Pontiac Fieros, but I digress.   Several accidents occurred when a pilot didn’t realize the rear engine had shut down and attempted a takeoff.   The single engine take off roll exceeded the runway length.   To prevent this the FAA Issued Airworthiness Directive 77-08-05   which prohibits Skymasters from single engine take offs, and  a placard in the cockpit which reads “DO NOT INITATE SINGLE ENGINE TAKEOFF’
In February 1965 Cessna introduced the 337 Super Skymaster.   While similar in appearance to the 336 it was a complete redesign.  To aid in the overheating rear engine a dorsal intake was added.  The 337 received retractable landing gear.    To improve performance the wings incidence angle was increased and its nose cowling reshaped.  The tail boom angle was also increased to enhance tail performance.   The 337 continued production until 1982 and under for a few more years under license by Reims in France.
In 1965 the USAF was looking for a replacement for its O-1 Bird Dogs and to act as a “stop gap” off the shelf aircraft until the North American OV-10s came online.   The 26th  336 was converted to a Forward Air controller  ( FAC) and given to hard two hard points for rockets or guns.   The 336 caused the creation of the 337M.  In 1967 the USAF placed an order for what would become the O-2A   The Air Force also took 32 337s directly from the Civilian line.  These would be called O-2Bs
The O-2A differed from the 337 in many ways.  The spinners were removed from both engines.   The cabin was given additional windows above the cockpit for upward visibility.  The Cabin door on the right side was also given observation windows to improve downward viability. Eventually  the Left side window also was enlarged so the pilot could see the oncoming  aircraft it was designating for.
  The wings were now equipped with four hard points.  They hard points could hold the SUU-11/A  Minigun,  or  MAU-3A Bomb racks.  The primary weapon hung, however,  was the LAU-59/A launcher which held 19 Mk40  FFAR  ( Folding Fin Aerial Rockets)   These were often  Willy Pete’s  jargon for White Phosphorous.   This was the primary way to mark a target in the FAC role.  The 19 rockets could be fired either one at a time or the whole container could be rippled.  
O-2As were substantially heavier than 337s due to all the military gear.   The Main panel now had a gun sight.  Though for most FACs a grease pencil mark on the windscreen worked just as well if not better.  There was an Armament control panel added to the main controls.  Armor was placed below the seats and the fuel tanks were given foam linings.
Behind the cockpit was a rack of radios.   UHF for talking to the other TAC aircraft.  FM to talk to the ground troops.  Lastly a VHF radio, to be able to talk to home base to coordinate air strikes.  This was a problem all the way up through the first Gulf War.    Also in this rack was the navigation suite of ; TACAN, VOR,  and ADF.
The O-2Bs, which were production 337Gs,  were originally purchased as trainers to get  pilots and ground crews familiar with the aircraft.  Eventually the O-2Bs would also go into war as PSYOP aircraft.  These aircraft would be given a huge loud speaker on the left side to broadcast propaganda.  They were also given a “Bomb bay” so they could drop leaflets.  They came to be known as BS Bombers.
 In South East Asia the USAF lost a 178 aircraft.  Eventually in the conflict they were replaced by OV-10 Broncos.
After the war the O-2 soldiered on in Active Duty and Air National Guard.   A small child’s mother used to hate Saturday Mornings when between 6-10  O-2s would fly over their house make a racket like a swarm chain saws .  Those 111th Tactical Air Support Group would eventually fly OA-37s and OA-10s and within the last week begin their new mission flying MQ-9 Reapers as the 111th Attack wing.
One of my all-time favorite squadron transitions, and in the  WTF, category  was the 105th Tactical Support Group  became the 105th Military Airlift Group . The mission went from flying O-2s  to flying C-5As !  How’s that for a conversion? 
 U.S. military service ended for the O-2A when the US ARMY retired the last two. They were used as observation aircraft at the Yuma Proving Range, and were turned over to museums in 2010, not bad for a Stop Gap aircraft from the sixties.  Adding additional support to the old adage “There is nothing more permanent than something that’s temporary.”   
Much like one of my other favorite aircraft  the DC-3  the 337 was given the Basler Turbo conversions treatment.   The Basler Turbo 37 had both Continentals removed.  The fuselage was stretched from 29 feet 9 inches to  36 Feet 10 Inches allowing for 9 passengers and a pilot.   The Pusher engine was replaced with at 550 HP Pratt & Whitney PT6 with a Three Blade Prop.  The aircraft can take off fully loaded (for Cleveland) in under 450 Feet.
O-2s served on the fire lines of California also.   California Department of Forestry and Fire Protection went to Davis-Monthan Air Force Base, the Boneyard, and picked 20 airframes from 40 they were given access to.  By 1976 the O-2 were again directing “Air Strikes” and continued to serve until the late 90s when they were replaced by OV-10s
For 10 years from 1991 to 2001 the Hermanos al Rescate used Skymaster to look out for and drop supplies to Cuban refugees fleeing to Florida by boat.   Much like another conflict in the Skymasters past, two of the Brothers to the Rescue aircraft  were shot down by  a  Cuban MiG-29 over international waters while on a search mission.  A third was targeted until a pair of F-15As crossed into that international air space.
Overall 2,993 Skymasters were built.
To this day this little boy loves to hear the sound of those swarming chain saws. 
Works Cited
"O-2 Skymaster." O-2 Skymaster. N.p., n.d. Web. 12 July 2014. <http://www.cc.gatech.edu/fac/Thomas.Pilsch/AirOps/O2.html>.
"Skymaster Owners And Pilots Site (SOAP) C336, C337, O-2." Skymaster Owners And Pilots Site (SOAP) C336, C337, O-2. N.p., n.d. Web. 12 July 2014. <http://www.337skymaster.com/websites.htm>.
"Skymaster." Skymaster. N.p., n.d. Web. 12 July 2014. <http://www.skymaster.org.uk/history-of-the-skymaster/>.
"Spectrum SA-550." Wikipedia. Wikimedia Foundation, 07 Jan. 2014. Web. 12 July 2014. <http://en.wikipedia.org/wiki/Spectrum_SA-550>.

1 comment:

  1. Great summary of an airplane that has had an impact greatly disproportionate to the number produced (501 O-2As)
    Chris Mayer