The Differences

[N73GX]

I am not a pilot but I am a member of the AOPA and a Aviation supporter.
I do not own a Skymaster but Love the aircraft and safety features of a center line thrust.

Ok, Enough of all that. I am looking for information pertaining to all types of Skymasters. I am currently creating a O-2A for Microsoft’s Flight Simulator. I thought this would be the best place to ask questions about the skymaster that I do not have the answers to.

Besides internal workings and panels of the 337 what are the major differences of the 337s? I am aware of window placements between pressurized, military and other utilitarian 337’s. What I am looking for is actual air frame and design. Is there any?

Thank you for information you can provide

Jason Garrett

[OSCARDEUCE]

Jason
The O2-A was about 800 lbs heavier than its civilian brother the 337. The wings had 2 tanks in each wing. there was the addition of a 3rd spar in the wing and hard points to carry rocket launches and ordinance. There are 2 titanium runners on the underside of the fuselage to protect it in case of wheels up landings (combat damage). The rear alternator is belt driven,while the front is driven off the accesory portion of the engine. Most O2's have repaired bullet/shrapnel holes. Anyone with anything else.
The O2-A is a beast on one engine, especially with external stores. Single engine ceiling is about 2200 ft in my aircraft with full fuel,pax and a warm day. The O2-A had a smoke system on the rear engine to make it visible to the aircraft it was controlling. The elevator was the earlier 336 shorter chord version with some of the counterweights taken out to make the controls heavier. The Military pilots were more used to higher control pressures than civilian pilots.
Will add more as I remember. Go to www.cessnawarbirds.com for more info. You can get a great book there on the O2-A and other Cessna aircraft. You can see my O2-A at www.huey.org and www.mapsairmuseum.org
Tom

[Kevin McDole]

Jason,

re: differences in various models of 337

Here's a quick overview - let me know what details you'd like:

Models were: normally aspirated, turbocharged, and pressurized (which is also turbocharged).

Fuel capacities varied from around 90 gallons up to 148 in some models.

Earlier fuel systems contained 4 tanks (2 in each wing) and the pilot would have to select tanks manually. Later models were simplified - one tank in each wing so fuel management was much simpler.

Think of the front engine as the "left" control, the rear is the "right". For instance, the front engine uses the left wing tank, the left throttle, prop and mixture control. The gages also follow this convention. RPM, fuel pressure, and MAP have left and right needles.

[N73GX]

This is all great information. Thank you very much. I knew this would be a great place to get the info.

Thanks again
Jaosn

[WebMaster]

There is another place, it's on the SuperSkyrocket page, history of the 337

http://www.superskyrocket.com/pages/...istory_1_1.htm

Tom (Oscardeuce):

I was interested to learn via your post of the extra spar in the 02. I seem to remember reading somewhere (Cessna propaganda?) that there were NO structural changes made to the Skymaster airframe, with the exception of hard points for mounting hings under the wings, when it became the 02. This sounds structural to me. Did Cessna feel a need to beef up the wing or was this to meet a government spec? I understand that there's a guy who does (used to do?) an airshow routine in an older (pre-"porthole" side windows `72-73?) 337. Anyone know if this airplane is actually an 02? Thanks for the input.

Regards,
Jim

[w1bw]

I'll piggyback on this thread about differences between various skymasters. I'm just starting the process of considering a normally aspirated 337.

The big dividing line is clearly the F to G model transition. I've read the article on this site which also appeared in one of the Cessna group magazines extolling the virtues of the late-pre-G models. From this and other info, i see the following differences (older vs newer):

Gear: hydraulic (optional dual) vs electro-hydraulic
Fuel: main/aux tanks (124) vs integrated (148)
Seats: regular middle row vs bench
Weight: empty weight 230 less on F vs G
Door: normal vs swing-down
Cabin: F 4" wider than G
Windows: larger side windows in F vs G
Noise: F more noisy than G
Speed: F 4kt slower than G

Is this all accurate? I think there were other seat changes during the G/H model run, but not sure what changed when.

I'm particularly interested in hearing from those of you who have flown models on both sides of this fence. I generally like later models of most things, but cabin comfort is important.

[kevin]

The fuel capacity change (to 148) did not occur until the H model in '76, to my knowledge, although I will be happy to be corrected.

There was a change in back seats from G to H, see this thread:

http://www.337skymaster.com/messages...highlight=seat

Having flown both, I don't think the noise difference is really significant. The pressurized 337s are somewhat quieter, but the normals seem all about the same to me. Never took a meter to it though.

Individual differences between airplanes (rigging, age of engines, etc.) will totally mask out the 4 knot book speed difference. For practical purposes, the speed is the same.

The rest of what you wrote looks right to me.

Kevin

[w1bw]

Guy: yes, I"m based at BED currently (1985 Skylane). I would enjoy taking you up on your offer sometime!

[Kevin McDole]

My notes indicate the capacities of the various models are as follows ("usable" is a little less than these numbers):

1965 337 through 1972 337F
Standard: 92.8
Long Range: 131

1973 - 1974 337G
Standard: 92.8
Long Range: 125

1975 337G
Standard: 92.8
Long Range: 150

1976 337G through 1980 337H
Standard: 90.6
Long Range: 150.6

[skymstr02]

Originally posted by hardball
Tom (Oscardeuce):

I was interested to learn via your post of the extra spar in the 02. I seem to remember reading somewhere (Cessna propaganda?) that there were NO structural changes made to the Skymaster airframe, with the exception of hard points for mounting hings under the wings, when it became the 02. This sounds structural to me. Did Cessna feel a need to beef up the wing or was this to meet a government spec? I understand that there's a guy who does (used to do?) an airshow routine in an older (pre-"porthole" side windows `72-73?) 337. Anyone know if this airplane is actually an 02? Thanks for the input.

Regards,
Jim

There are numerous structural differences between the O-2A and a civillian version. The rear spar is beefed up to absorb the firing impact loads from the hard points. The main spars are different, and are attached to the fuselage using bolts two sizes larger than the civil counterpart. There are lifting eyes installed on both fuselage spar carry throughs. There is 5 degrees more elevator travel, more elevator trim travel, and the bob weight and spring in the left vertical fin are missing, creating a more heavy feel in the pitch for the USAF types. An O-2 can cross feed the aux fuel, the electrical system is totally different, the landing gear indicating system can silence the gear warning horm, there is no yellow light to indicate gear up, but a red light to indicate gear in transient. The cowl flap actuating system is different. The engines have tach generators, no mickey mouse mag sensor for engine speed indications. The engines inter cylinder baffling is different, so no prop spinner is necessary, no so on the civil version, etc, etc, etc.

I've got around 500 hours in mine, and wouldn't trade it for any other 337.

Skymaster02,

Thanks for the info. Looks like I'll be hunting for an 02!

Regards,
Hardball

[WebMaster]

Originally posted by w1bw
Guy: yes, I"m based at BED currently (1985 Skylane). I would enjoy taking you up on your offer sometime!

Carefull if you go flying with him. His gear doors are SHINY on the INSIDE!!!
Seriously, I have never seen a neater aircraft.
I'm still working on keeping the belly clean