Max Gross Weight of a Combat Ready O-2

submitted by: Alva Leon Matheson

These are the “Military” Dash 1 weights for the O-2A & B. Max gross weight 4,400 pounds or 4,850 pounds if everything over 4,400 is internal fuel or wing mounted. The book says the max landing weight is 4,400 pounds. Basic Wt A- model – 3,226 pounds, (B model – 3,268 pounds), this includes “unusable” fuel but “not” oil. Add Oil 38 pounds, fuel in main tanks (88.4 gals) 528 pounds, or mains and auxiliary tank (124 gals) 732 pounds, two MA-2A rocket pods with (supposedly WP) rockets 94 pounds, one freshly bathed and clothed FAC and misc. gear 220 pounds and ‘other’ payload/cargo. This puts our takeoff weight for the O-2A at 4,310 pounds, less the radio gear and ‘other’. Since we didn’t hang the CP (co-pilot), FAN (Forward Air Navigator) or Observer, radio gear or ‘other’ on the wings, and we are already at 4,310 pounds, one must keenly observe that we routinely took off over grossed.
I have no info on the weight of the standard back seat radio package (any O-2A radio maintenance or Weight & Balance guys know?) and rarely was I freshly bathed and clothed on most of my launches (average side load of red clay, mud and dirt about five pounds). Then there was the variety of toys we (might have to be a “one man army”) threw on board, like official (and unofficial) survival aids (parachutes, extra bullet spreaders, big bang makers, bowie knives, lots and lots of ammo bandoleers, (they looked really cool around the “Donut Dollies” if you were fortunate enough to operate from or divert to a MOB (Main Operating Base). Frightening to think that every guy (except the REMFs) onboard wouldn’t be seen without his toys, so one had to add that to the gross weight too. Add to that a bunch of maps/books, those fancy cameras, C-rations for breakfast, lunch and maybe dinner, and another crew member or observer or an occasional “tourist”, you can see why our “real” takeoff gross weight is an elusive figure. However elusive, it behooved any O-2A FAC to be very conscious of it and to have some idea of his single engine service ceiling throughout the mission. Better to bailout early (if high enough and if he had a parachute of course) than take up farming by plowing through the fields (at best) or lumbering by mowing down the trees (at worst).
So far I’ve gotten estimates of 4,800 pounds (okay) and 4,900 pounds (Oops see the above). That’s way above my estimate of 4,500 pounds, because those guys used four rocket pods (great idea) and two-crew-members which makes their figures right on. At those weights, one shouldn’t takeoff if one suspected he might lose the rear engine (you know, the one the bad guys always managed to hit) because, according to the Dash 1, his service ceiling was sea level on a Bermuda day but damn well below that on most days we saw in Vietnam. Front engine only, you’re a goner unless you’re by yourself, over water, jettisoned everything, or you were awfully high (a rare occasion for most FACs)! If one had a choice, he would prefer the VC/NVA hit the front engine (the one with the engine driven hydraulic pump and generally just sitting out there burning up fuel until one needed to lower or raise the landing gear). But the rear engine operating gave one reason for hope.
If you trust the Dash 1 performance charts (USAF tested of course), the rear engine service ceiling @ 4,900 pounds would be about 2,000 MSL in Bermuda but somewhere between 500’ and 1,500’ MSL on a typical 90 degree day (average worst case) in Vietnam. Actually that would be 300’ to 1,200’ because it seemed there were always 200’ trees below when one lost an engine. Not bad for a guy (we didn’t have female pilots back then) right over DaNang (but not Monkey Mountain or those other big rocks of course), Nha Trang, Cam Rhan Bay, the delta or the coast. From what I’ve seen, few of us had that good fortune, as the terrain we normally operated over was much higher, more like 1,000’ to 6,000’ MSL. No doubt that had something to do with why they were called “The Highlands.” I called them “The Badlands” because if I lost an engine, that would be a more appropriate term.
So, it was not totally true that one couldn’t fly an O-2A on one engine unless that occurred shortly after takeoff at max “over-gross” weight.
If you were lucky enough to be in the right place at the right time, had time to jettison everything except your CP/FAN or girl friend, (and your toys, remember we never went anywhere without our toys) you would have a gross of about 4,600 pounds (full fuel). Front engine operating ceiling would only be 500’ to 1,000’ MSL (don’t forget the 200’ trees), not much good to anyone in the areas I flew in. Rear engine ceiling would be 2,500 to 3,000’ MSL. You might make it if you could stay in the valleys or over the rivers as I did, but if there was a mountain range between you and a cold beer, you were going to have a bad day. Of course, these altitudes would improve as one burned off fuel, but only by about 600’. No doubt some were lucky. Sadly, some weren’t.
I seem to recall that engine out (feathered only) training at Hurlburt or Phan Rang. Anyone else recall that?
PS: An interesting note, the guys who wrote the Dash 1 performance data and set the max gross at 4,850 pounds must have dreamed of going along on one of our little excursions to collect combat pay. They frequently used a gross weight of “5,000” pounds. in their sample performance pages. Still trust the Dash 1?