The Navy installed what was known as a “Gold Stripe” engine that had an extra 250 horsepower in a few A/B’s flown by HC-7. This alleviated some of the power, or lack of power problem a bit, but the hot and humid conditions found in South East Asia dictated a better solution which was found in twin engine C and D models.
Both the UH-2A/B and the C/D airframes were almost identical. The big difference was from the top of the fuselage up because the C’s and D’s had two GE T-58 engines rather the one in the A/B.
With two engines, the UH-2C now had twice as much power as the UH-2A with the same rotor system. To add fuel capacity, the H-2Cs and Ds now carried external fuel tanks on either side of the fuselage that could be dropped in an emergency. With full fuel, you had about two and a half hours of fuel and didn’t have to worry about having enough power to hover.
To create the UH-2C and the HH-2C (which had some armor plate and at when first built, a three barrel mini-gun under the chin), Kaman Aircraft added a second engine and a combining gearbox. Now power went from the T-58 engines aft to a big combining gearbox and then forward to the transmission. So, there were a lot of shafts and bearings that needed greasing under the cowlings. See later story about molybdenum disulfide grease.
To get into the H-2, one climbed into the cockpit via a sliding door on either side of the fuselage. Except for the additional column of instruments for the second engine and two engine speed selectors on the left side of the center console, the instrument panels were the same.
Flying the H-2C and D was a joy. For a helicopter, it was fast and could reach 120 – 130 knots (if the blades were in trim) thanks to lots of power and its streamlined shape. It was small so it was easy to land on the smallest flight deck and very maneuverable. It could out turn any other helicopter I flew. In fact, in the D, you could roll it into eighty to ninety degrees of bank and pull two gs and maintain altitude for at least one full turn. One had to watch your rotor rpm because the increased gs would cause the main rotors to speed up and you didn’t want to risk having them come off!!! I often practiced erratic (some might say all my flying was erratic!!!) left and right climbing and descending turns as a way of preparing to throw off the aim of anyone who might want to shoot at me.
Another fun thing to do in the H-2 was quick stops. In these, you went from a fast cruise, i.e. ninety to one hundred knots or more and then pulled the nose up to about forty-five degrees or more above the horizon while at the same time lowering the collective to maintain altitude. The idea was to slow the helicopter as fast as possible and maintain altitude. The maneuver ended with either the helicopter in a hover or at a slow speed, i.e. ten to twenty knots. There were variations in which we used the rudders to do a pedal turn toward the end of the flare to turn the helicopter ninety or even one hundred and eighty degrees from the original heading.
Of all the Navy helicopters I have flown – the TH-57A (the Navy’s primary helicopter trainer version of the Bell Jet Ranger), UH-1D, H-2 and H-3 series – the D model H-2 was the easiest to fly and hover even without the auto stabilization equipment or ASE working. It had lots of power and tail rotor control. Hydraulic boost made it easier to control but it was flyable, albeit it needed a strong arm to fly it boost off. As an instrument platform, it was stable and the gauges large and easy to scan. In short, it was like a sports car, and it was fun to fly.
Even though the pilots “wore” the H-2, there was plenty of room in the cockpit and the seats were comfortable for a long mission. The cabin of the H-2was another story because it was pretty cramped. There wasn’t room to stand up and with two air crewmen on board and all the gear we carried, the cabin was crowded. Add a couple of passengers and it was a packed house. There were canvas troop seats for four, but I’ve had seven or eight packed into in the cabin.
We flew with the cockpit doors either off or open and the sliding cabin doors again, either off or open unless it was bitter cold. The wind provided the air conditioning and in SE Asia, there was nothing that could cool you off unless you were inside the ship. Even when AC on the ship was on full blast and the temperature was in the low seventies. In the winter, the H-2’s doors didn’t seal well and it was drafty. The heater pumped out a lot of heat from the center console so that depending on in which seat you were sitting, your right or left side was toasty warm and the other side was cold.
And, then there were the blade flaps. In the H-2, the main rotor blades had an external flap which looked like an aileron that was added as an afterthought. Control inputs from the cyclic stick or the collective moved the flaps and helped change the pitch of the blades. One of the benefits was that it reduced the amount of hydraulic power needed to control the rotor blades. They worked great as long as they were in “trim.” The blade flaps on two of the blades could be trimmed using electric motors and but they were, at times, very difficult to keep aligned. If they were out of trim, the H-2 had a vibration that could range from mild to very uncomfortable.
The avionics compartment was in the nose and access to it was through clamshell doors that were split vertically. I’m sure the designers pointed out the fact that the clamshell doors made it easy to get to the black boxes that controlled the navigation and communications equipment, the ASE and the blade trim system. Even though there were rubber seals on the doors, they leaked. Water in the avionics compartment is not a nice thing particularly if you are flying in a heavy driving rain on instruments.
On the UH-2C, Kaman kept the three bladed tail rotor from the A/B and it wasn’t powerful enough to compensate from the additional power available. If you pulled a lot of power, you would do two things that were bad if one was not very, very careful. First, you could run out of tail rotor authority and the helicopter would rotate uncontrollably to the right. Ham handed increases in power could also over torque the combining gearbox and/or the transmission which would at the very least, shorten their lifespan or worse, cause either one to fail. The severe limits on the amount of torque that could be applied to the transmission and the power of the tail rotor to offset torque limited the crew’s ability to fly the helicopter anywhere near its true performance limits.
The UH-2A was underpowered in almost all flight regimes and the hot and humid conditions in South East Asia exacerbated its lack of power problems. Pilots joked that in the twin engine UH-2C used the same Pilots joked that the UH-2A/B had barely enough power to turn the rotors while the UH-2C had so much, it could unscrew them. To correct the tail rotor authority problem, the D had a four bladed tail rotor.
Other maintenance headaches were keeping the tail rotors greased and corrosion. The castings for the transmission, combining gear box and others were made from an aluminum magnesium alloy. The good news was that they were light and strong. The bad news was that they were very susceptible to corrosion from the salt air. And, god forbid, if they overheated and caught on fire, it would have been a race between how fast you could ditch the helicopter and how fast the fire caused the helicopter to disintegrate from the heat or explode. You have two choices with a magnesium fire – suffocate the flames with sand or submerge it in water – and neither of them is a practical solution in a flying machine!
The dynamic system of each model of the H-2 needed frequent greasing and the tail rotor was the most sensitive of them all. Every ten hours, we shut the main rotors down and then greased the bearings on the tail and main rotor. Sometime around hour twelve the vibrations would start and would continue to get worse until the bearings were greased. Go long enough without greasing and the bearings would be ruined or fail which could have its own disastrous consequences
An attempt was made to arm the UH-2C in a version called the HH-2C but the three barreled mini-gun that hung in a nose turret had problems staying in the safe position. Landing a helicopter on the small, confined deck of a destroyer requires firmly planting it in the right position. There were several instances where the gun fired the remaining rounds in the barrels so it was taken off.
From the lessons learned in the UH-2C and the HH-2C, the Navy and Kaman created the HH-2D. It had a beefed up transmission and combining gearboxes and a four bladed tail rotor along with provisions for armor and self-sealing tanks. The upgraded gearboxes and four bladed tail rotor significantly reduced the limitations on the amount of power you could use and combined with the four bladed tail rotor, one had plenty of tail rotor control. With just two and a half hours of gas on board, even with external tanks, the HH-2D’s range limitations kept it in utility and short range rescue roles.