HSC’s Double Bubble Trouble

By LT I.M. "Fridge" Grover, USN

When the Ronald Reagan Strike Group left the Northern Arabian Sea last September, it was the end of an era. For the first time in over 20 years, there was no longer a carrier in 5th Fleet. The end of the war in Afghanistan signaled a shift in the military. For the Navy, that meant focusing more on the Indo-Pacific looming threat of the near peer power that is China and increasing our presence in the South China Sea. What this means for the Carrier Strike Group (CSG) is more interactions with Chinese and more long range constructive kills, all of which occur over vast open stretches of ocean. You may be asking yourself, “what does this have to do with Helicopter Sea Combat (HSC)?” The answer to that question is simple enough. We are, as we have always been, tasked to recover our fellow aviators when they are having the worst day of their lives.

As the Navy and the Air Wing move into maritime operations in and around China, the Air Wing leadership looks to do long range maritime strikes, the possibility of interactions with opposing forces increases. With this increased interaction comes the very real world possibility of an aircraft being shot down, “swapping paint” during an intercept, and the ever present possibility of an aircraft malfunction hundreds of miles away from the carrier. In the event of this happening, the HSC Community has asked itself how it can best serve in the Personnel Recovery (PR) realm. In preparation for this flight, there has been extensive planning around Distributed Maritime Personnel Recovery (DMPR). For the HSC Community to be successful in DMPR, we have to increase the combat radius of the MH-60S. The Sierra’s fuel system, originally based on the Blackhawk's system, is not as robust as its sister aircraft, the MH-60R, and other legacy Seahawks. The Block One Sierras only had an internal capacity of 2,400 pounds of fuel which gives the operator approximately two hours of flight time. This led to a call for the Extended Range Fuel System (ERFS), which gives the Sierra the option of adding up to two auxiliary tanks, internally positioned in the cabin, thus increasing the fuel capacity of the aircraft by 1,400 pounds per tank. The HSC Community now considers a single auxiliary tank the “standard,” however, with this new operational requirement, maybe the community will shift to a new standard of dual auxiliary tanks.

Every year HSC-12 uses the dual auxiliary tank configuration on its cross country from mainland Japan to Okinawa. Senior aircraft commanders would always warn their junior copilots, “Make sure both tanks transfer, you won’t make it with trapped gas.” This statement is true. If you trap enough gas, completing the legs can be impossible. On the last leg of my first cross country to Okinawa, which is primarily overwater, we trapped about 500 pounds in one of our auxiliary tanks. Fortunately for the crew, the weather was good and we were able to land above NATOPS minimums, but our low fuel lights had come on prior to touchdown. If we had to delay for weather or had more of a headwind, it could have led to a more pressing problem. During this flight, we changed which auxiliary tank we used each time we transferred fuel. This was the technique that this Helicopter Aircraft Commander (HAC) had heard from one guy, who knows somebody, who said 80% of the time it works 100% of the time. During this cross country, all three HACs had different ideas and methods for using the auxiliary tanks. This anecdote serves more to show that there are no codified procedures and that it is more of an, “I heard to do it this way,” than any authorized procedure published in a governing publication. All NATOPS has to say about dual auxiliary tank (commonly referred to as “double bubble”) operations is how to fuel the aircraft and contains no inflight procedures. These problems led HSC-12 to look for more answers when it came to the use of the double bubble configuration.

Working back to the problem at hand, long range maritime strikes and Defensive Counter Air (DCA) missions require HSC to remain flexible and ready to execute PR while using the dual auxiliary configuration to match the fixed-wing ranges. HSC-12, on their Summer Patrol 2022, began using dual auxiliary tanks more regularly. Everything from plane guard, to logistics runs, to MEDEVACs, all while collecting data about the use of the fuel transfer system. One major reason for the data collection was to determine if there is, in fact, a “best” method to transfer fuel from our auxiliary tanks into the main tanks to avoid trapping fuel. We used different methods. One method involved transferring one tank down to 100 pounds, secure the fuel transfer, and then switch tanks. Another involved transferring from the tank and letting the system automatically secure before switching tanks. The final method was to transfer in 500 pound increments, switching between the tanks each time. We found that when you only switch tanks once and secure the fuel transfer with around 100 pounds remaining in the tank, it seems to have best results. We are continuing to collect data during our Fall Patrol in order to provide the best answer to the dual auxiliary tank fuel transfer problem.

The use of the dual auxiliary tank configuration is not without drawbacks. The biggest being that the auxiliary tanks significantly reduce cabin space. Per our publications, we are only authorized to take three passengers in seats while in the dual auxiliary tank configuration. Furthermore, in the dual auxiliary configuration, we are unable to support any VERTREP operations as the forward auxiliary tank, when installed, sits on top of the cargo hook access hatch. Additionally, installation of the second auxiliary tank inhibits the ability to install the deck-plate mounted GAU-21, .50 caliber machine gun. One of the major missions of HSC is combat logistics and this configuration limits our ability to execute this mission.

The configuration also presents an inconvenience and distraction to aircrewmen. In order to change tanks, the aircrewmen must crawl back to the tanks to change a directional valve. This can be a difficult to reach switch, and if the aircraft has any cargo or passengers, the crewman must first climb over them in order to switch the valve. Not only can this be difficult, but it also takes their attention away from the mission at hand.

Just as the Navy is evolving to better counter a near-peer adversary, the HSC Community must evolve as well. We must look for ways to increase our capability for the missions we are called to do. Perhaps we should look to add additional tanks, or ones that allow us to more easily configure to the mission at hand. A good starting place could be something akin to what we see with the Army Blackhawks with their external wingmounted tanks, or perhaps a door frame mounted or window mounted .50 cal. While missions such as HVU protection and combat logistics will always remain, the days of the CSG regularly going through the Strait of Hormuz are over for now. As more CSGs and Amphibious Ready Groups (ARGs) start focusing on operations in the vicinity of China and the South and East China Seas, we must invigorate our focus to other mission sets like DMPR. We must begin to develop more robust procedures, or find an engineering solution for routine operations with dual auxiliary tanks. Until then, we must continue to gather data about how to most effectively employ our beloved aircraft.

Extended Range Fuel System (ERFS)