Passing Gas

The capability of In-flight refueling (IFR) of combat aircraft is critically important for a nation to project its military power. The few nation-states that own and operate “tankers” must be regarded as long-range threats by their enemies. In this context, it is no wonder that huge amounts of resources have been dedicated by so many countries to achieve this capability.

Early experiments from the 1920s to the late 1930s mostly pursued endurance records. Later Britain’s Sir Alan Cobham advanced the process by using IFR for transatlantic crossings of Empire flying boats. WW II revealed the need for IFR, but little progress was made until after its conclusion.

Hose and drogue systems emerged during the Korean War. Relatively simple to build, they consist of a hose reeled from the tanker with a “basket” on its end. The receiver aircraft flies formation with the basket and maneuvers so as to insert their “probe” into it for fuel transfer. Notoriously difficult for the receiver pilot; the basket frequently flails due to the aerodynamics of the approaching aircraft.

After WW II, General Curtis LeMay wanted a system that could transfer fuel faster than had been possible with the probe and drogue. Boeing developed the KC-97 Stratotanker which came equipped with a flying boom. This enabled a more stable tanker delivery system with higher flow rates. However, receiver aircraft needed a complex “boom receptacle” to accommodate this new system. The receptacle assembly included a lighted door which could be opened to accommodate the boom. The boom could be maneuvered in three dimensions by an operator lying prone at the rear of the tanker aircraft.

The tanker aircraft were equipped with “director lights,” on their bellies and forward of their main wing. These lights enabled the boom operator to command the receiver aircraft forward/aft, and up/down. They also enabled radio silent refueling operations. The director light strip on the left commanded up/down that the boom operator needed to direct the receiver into position. Green in the middle, the lights glowed yellow for about a third of it either side of the middle, and red from the yellow to the end. On the right side of the tanker’s belly, the forward/aft lights guided the receiver aircraft. Once the receiver began taking on fuel, the director lights became automatic. In that case, the position of the boom, rather than the boom operator, served to illuminate the proper lights, and thus inform the pilot of the receiver aircraft if they were drifting out of position.

On a typical refueling that I experienced in the F-106 in the 1970s, a flight of four fighters would rendezvous with a KC-135 tanker. This usually began with an offset, head-on (altitude separated) approach. After assuring the tanker crew that the fighters’ weapons were safe, the fighter formation leader would call the moment for the tanker to begin a 180-degree turn to the fighters’ heading. If all went according to plan, the tanker would roll out on the fighters’ heading, slightly ahead and slightly above them. With the assistance of on-board radar, this could be done in the weather, but was much more tedious. Once near the tanker, lead would assume the “precontact position,” in trail with the tanker and a few feet behind it. The other three would fly formation with the tanker on either side of its wingtips. The boom operator would then begin giving the receiver aircraft instructions toward the contact position.

When my turn came, I maneuvered into the precontact position, enabled my refueling system, and waited for the boomer’s instructions. When I enabled my refueling system, the boom receptacle door opened, illuminated its lights, illuminated the blue “ready” refueling indicator light on the glare shield above the instrument panel, and opened the jaws of the boom clamp assembly. Three lights mounted high on the fighter’s instrument panel announced: “ready (blue),” “contact (green),” and “disconnect (red).” When cleared into the contact position, I pulled up slightly to position the end of the boom level with my eyes and began inching forward to the correct position according to the boomer’s instructions.

“Up two, forward five,” he says.

I head directly for the boom tip. As it slowly nears my windshield, it gently moves an inch or two to the side. I never knew if it was the boomer doing that or the boundary layer aerodynamics of the cockpit. It is now behind me and I must rely solely on the boomer’s instructions.

“Forward one,” he says. I can feel the boom nozzle contacting my aircraft. After several thumps, my blue ready light extinguishes, followed by the illumination of the green contact light.

“Receiver contact,” I say

“Tanker contact,” the boomer says.

I pause a few seconds and then squeeze the switch under my right index finger to disconnect. My red disconnect light illuminates.

“Receiver disconnect,” I say.

“Tanker disconnect,” he says.

I get to do this five more times in order to log my mandatory six hookups in six months. Immediately above my left hand which is on the throttle, is a long switch. I momentarily release the throttle and bump the switch upward with the back of my hand. That motion resets the refueling system back to the “ready” mode.

On my sixth hookup I receive a “top up” on fuel. I show 230 knots on my airspeed indicator, which is a little slow for comfort. As the fuel flows, my weight increases to the full capacity of 14,495 pounds. I continuously add power as my weight increases. Nearing the end of the process, I am at almost full throttle, but without afterburner, called “military” power.

“Tanker fuel cutoff,” says the boomer.

“Receiver disconnect,” I say.

I turn off the IFR system and return to a position off the right wing of the tanker. The maneuver has taken about seven minutes. Soon we are all topped off and separate from the tanker. My airplane flies much better at 300 knots.

One cloudless day in the late fall of 1970 I participated in an IFR mission with the squadron chief of maintenance. Although a fully qualified pilot, he flew less than the rest of us. A young Lt. Col., he was physically fit and mentally sharp. I have no reason to doubt his story. I had received my six hookups and fuel and had moved out for his session. All went well until he began taking fuel. His aircraft began to slowly move forward. The boom accommodated this by retracting and pitching downward.

“Approaching forward limit,” the boomer said with no response.

“At forward limit,” he announced in a slightly higher pitched voice.

“Breakaway, breakaway, breakaway,” he fairly screamed over the radio.

The fighter kept moving forward. The boom, being fully compressed, had nowhere to go except to bend like a pretzel. With no response from the fighter, the tip of the boom bent so as to be nearly vertical in the fighter’s boom receptacle. I moved out a little farther, wondering if I was to witness a huge fireball. Finally, the boom broke just above the fighter’s boom receptacle. The stored energy in the bent boom caused it to violently recoil upward, returning with great force toward the fighter. As the remaining part of the boom struck the top of the fighter, the steering devices on the sides of the boom broke off and departed in the fast-moving air. Fuel streamed from the boom. Meanwhile the tanker had firewalled his throttles to no avail.

“Mike Golf 05, do your read, do you read?” asked the tanker.

“Loud and clear, what just happened?” responded the fighter pilot.

“You just collided with a tanker. I recommend you take it home as an emergency aircraft.”

We all made it home uneventfully. Back on the ramp, everyone gathered around as a piece of the tanker was removed from the fighter. He swore that he had a momentary radio failure that caused the incident. I have no reason to doubt that. Even so, he became known as the “souvenir collector.”

The Tennessee Air National Guard was still flying the ancient KC-97, propeller-driven tanker in 1970. Like most National Guard airmen, they were supremely proficient at their jobs. Refueling with them was always a pleasure, except for the airspeeds. Only able to achieve 195 knots, their tankers demanded slow-flying the F-106, especially at heavier weights. To compensate for this, the “toboggan” technique was invented. When the receiver is unable to stay in position at full power, the tanker begins a descent, granting the receiver a small power advantage. That always worked well with the KC-97 crews, and they were good at it. Another difference with refueling behind a KC-97 was that their boom was slightly offset from the center of their aircraft. In the F-106, a “vision splitter” divided the center of the pilot’s view so as to eliminate confusing reflection from the sides of the windscreen. Hardly noticeable under normal flying, the vision splitter required the pilot to move to one side of the cockpit to see the tanker’s director lights. With the KC-97, no such inconvenience was required. Another difference present in KC-97 operations was that it performed its mission at lower altitudes. This made for a much more relaxed process since it happened below the area of positive control or “Class A” airspace where all aircraft must be on an instrument flight plan and constantly negotiating with Air Traffic Control. The Tennessee Air National Guard remains a proud and effective organization, now equipped with KC-135R Stratotankers.

The F-102 was not equipped for IFR when originally built. A few were equipped with crude, temporary probe assemblies in order to ferry them to Southeast Asia during the Viet Nam war. When I flew from Iceland in the F-102, without IFR capability; endurance was short, and the Russians knew it. We would frequently intercept TU-95 Russian bombers at the edge of our range at a location carefully calculated by them to cause us maximum stress. The sorely needed IFR capability finally materialized when the F-102 was replaced with the F-4, and later, the F-15. On one daylight mission to intercept Russian bombers near the Faroe Islands, I was positioned near a Russian TU-95, hurriedly performing my surveillance, when a voice with a decidedly British character came over my radio.

“Sloe Gin, Eleven Squadron lead here, when you finish, we would like to survey the Bear.”

It was a flight of British Lightning fighters out to harass the Russians, just as we were.

“Certainly, I’m finished, it’s all yours.” I said.

With that, a very much faster fighter passed underneath the bomber, lit its twin afterburners, and sharply pulled up in front of it, continuing skyward performing several vertical rolls. This was a classic “hot nose” maneuver, designed to create turbulence and surprise in the Russian crew.

“That was beautiful. I heard that the Lightning carried little fuel. How can you afford to do such a thing ‘way out here.” I said.

“We have a Victor tanker nearby.” He said.

I wonder if the F-4 pilots who followed me at Keflavik ever did such pranks.

In 1982, the Royal Air Force established a requirement for additional tanker resources, due to shortcomings identified during the Falklands War. As a result, nine Lockheed TriStars were acquired for conversion. Six of these became tankers, equipped for hose-and-drogue refueling. The first of these entered service in 1985. Hose-and-drogue systems are easier to implement than boom-type systems. However, three years from concept to operation is a notable accomplishment. Contrast that with the USAF KC-46 Pegasus program. Begun with a procurement directive in 2001, the latest forecast calls for the aircraft to be combat ready in late 2023. Plagued by cost overruns, delays, cancellations, rebids, and corruption; the thirty-year-old airframe design (Boeing 767) may be obsolete when the glacially-paced U. S. Government finally agrees on a new tanker. Due to “flaws in the bidding process,” the Airbus aircraft which won the 2008 bid, was rejected in favor of the Pegasus. Cost overruns and delays accumulated. Wiring redesign to military specifications, fuel system changes, and implementation of a remote boom operator station bedeviled the project. Failure to follow FAA processes in the design of the refueling system caused a delay, which is curious in an Air Force project. By adding additional capabilities along the way, such as electronic countermeasures, and electronic warfare, the aircraft is still years away from initial operational capability (IOC) and holding. I expect that further delays and cost overruns will forever continue to push the IOC and price tag ahead.

Much like the relationship between a child and its mother, fighter pilots (and, indeed, all receiver pilots) carry an unspoken gratitude for the life-giving fluids provided by tanker crews. Although frequently maligned by fighter pilots as being members of a support group, rather than front line combat crews, the bond between the two groups is palpable. During the Vietnam War, rumors emerged of tanker crews violating procedures to rescue a stricken fighter over enemy territory. Their courage and devotion to duty is much appreciated by myself and the other receivers whom I know.