Recollections of Vietnam
Contrary to what I would have believed before arrival, the greatest danger presented to the military aviator in South Vietnam was not the enemy. He was always there and would not hesitate to shoot at you if you provided the opportunity, but he was not the biggest problem. The real issue was the tremendous amount of air traffic, the confused air traffic control and communications system, and artillery and naval gunfire. The situation changed minute by minute and it required a high degree of awareness to avoid disaster.
The Republic of Vietnam, claiming itself to be a sovereign state, chose to operate the civil air traffic control system. When we flew under Instrument Flying Rules (IFR), we filed a flight plan with the Vietnamese air traffic controllers. Unfortunately, they were not yet well enough trained to do the job. At the larger airfields, like Tan Son Nhut in Saigon, there was rarely a problem, while at places like Nha Trang, just north of Cam Ranh, you were literally taking your life in your hands to depend fully on the controllers. Consequently, whenever we flew IFR, we would use one radio to maintain contact with the air traffic controllers and a second to talk to the nearest Ground-Controlled Intercept (GCI) site. GCI was normally used to provide extremely accurate navigation for aerial strikes (the B-52's used it to put their bombs exactly where they were needed), but they had the best radars in-country and took pity on fellow Americans at the mercy of the civilian air traffic control system. They would follow our flights and advise us of any nearby traffic so we could take our own evasive action.
Most of the time we were VFR (Visual Flight Rules) or "Special VFR" (this tended to be a euphemism for IFR without a flight plan and clearance) and we did not interact at all with the Vietnamese air traffic controllers. We depended on our eyes to avoid other aircraft. Remember that we had the civilian Vietnamese traffic (mostly Air Vietnam), civilian international air carriers (all operating IFR), the U.S. Air Force, the U.S. Army, the U.S. Marines, the U.S. Navy, the Australian Air Force, as well as the VNAF (Vietnamese Air Force) all operating more or less independently at the tactical level. Compartmentalization of information was routine and necessary in the military, so we had no idea what missions the Army or the Navy might be running and, likewise, they had no idea what we were doing. It paid to be attentive.
Now add the grunts on the ground to the equation. They played with some really nasty toys like howitzers. A howitzer is nothing more than a large rifle, but it can chuck a high explosive projectile over 10,000' high. Since 10,000' was our maximum operational altitude, our only choice was to avoid the launch site and impact site of those projectiles and all points on the line between. To facilitate this, the Army set up a network of "Arty" (short for artillery) command posts and sectioned off all of South Vietnam into regions. Before entering a region we called up the Army Arty site and asked for current firing information. To add to the confusion, the Army used arcane FM radios which operated in the 30 - 50 MHz range for these communications. That type of radio is unique to the Army, so our aircraft were retrofitted with them. They were among the least reliable communications devices we had. The Army would also change their frequencies often so as to keep the enemy guessing, but it also quite often kept us guessing. One learned early in the game what a "marking round" looked like. A marking round was a projectile that produced a thick column of white smoke on impact. This was to allow the artillery spotters (sometimes in light aircraft) to determine the exact impact point and relay instructions to the gun crew if adjustments were necessary. More than once we saw marking round impacts in areas we thought were clear. One of the most painful photographs I have ever seen was posted in the all Caribou operations areas -- it was a picture of a C-7A Caribou immediately after it had been hit dead center by a 105mm HE round. The aircraft was still in the air -- in two separate pieces. The picture was a reminder to check for artillery before entering a new sector. A further complication of the artillery problem was that the ARVN (Army of the Republic of Vietnam) rarely participated in warning people of their intentions. They just rolled out the guns and started shooting.
The U.S. Navy also got into this game, but they had even nastier toys. The Navy often set up their ships off the coast and fired inland. A naval rifle, as it is properly called, can achieve a projectile altitude of over 20,000' and their projectiles could be as big as a small car. Fortunately, the Navy was very efficient at informing us of its intended firing areas in our pre-mission briefings every morning, so we could give these areas wide berth.
I guess the postscript is that you also had to fly the airplane from time to time. Without a doubt, the best part of flying the 'Bou was the landing. The shorter the field and the rougher was all the better, for that was what this aircraft was designed for and thrived on. In a short field approach, the Caribou had a decidedly nose-low attitude. Those huge full-span flaps saw to that. Airspeed over the runway threshold could be as low as 42-43 knots and a huge pitch change was necessary to accomplish the flare preparatory to the touchdown. When there is less than 1,000 feet of dirt in front of you, you don't play around trying to get a "grease job" landing. You plant the mains, reverse the props, lower the nose, and get the beast stopped with brakes, reverse thrust, and always a great cloud of red dust. Properly done, this could be accomplished in under 200 feet if you had the luck to have any decent headwind and never more than 500 feet in the worst of conditions. I think everyone took great pride in his ability to put 14 tons of aircraft exactly on the money and get it stopped in the shortest possible distance; I know I did!
The second best part of flying the 'Bou was cruise. Here, at 105 knots and with no pressurization or air conditioning, we flew with the cockpit side windows open and the rear cargo door open. That provided a great breeze and also allowed you to hang your elbow (or your whole arm) out the window. The view from the "greenhouse" cockpit was superb and we were low enough to do a lot of sightseeing in our scheduled rounds. From that vantage point, Vietnam was a very beautiful country. On the ground, the inside of the aircraft was like a furnace, but as the aircraft climbed, the temperature dropped at 2 degrees C for every thousand feet. We welcomed the cool air at cruise and the opportunity to get some relief from the heat and humidity and often cruised at 9,000 or 10,000 feet (depending on our heading) just to get the maximum benefit from that standard atmospheric temperature lapse rate.
The takeoffs were always the time for extreme care. The Caribou, especially at high gross weights and the high density altitudes typical of a hot, humid climate, had very marginal single-engine performance. In a full STOL takeoff configuration at max weight, in fact, the best single engine rate of climb we could expect was -50 feet per minute! In these situations, from the time you passed your refusal speed until you accelerated and got the flaps retracted, you were entirely at the mercy of Pratt & Whitney. The most likely time for an engine failure was at the initial power reduction from Takeoff Power to METO Power. Never has an engine been treated so gently as during those initial power reductions! Fortunately, both of my Caribou engine failures occurred at cruise altitude and presented no great problem.