Nobody kicks ass without tanker gas...
Paul Tiller looks at USAFE's only dedicated tanker asset, the 100th Air Refueling Wing
Go to RAF Mildenhall on any day of the week and you will see a number of large grey-painted aircraft with a black square containing a white letter 'D' on their tails. These aircraft are the Boeing KC-135R Stratotankers assigned to the 351st Aerial Refuelling Squadron (ARS) of the 100th Air Refuelling Wing (ARW), one of the resident units at the base.
The history of the 100th ARW's association with England can be traced back to 1943 when the 100th Bombardment Group (Heavy) - 100th BG - was based at Thorpe Abbotts in Norfolk for the latter part of the Second World War. It was during this time that the unit earned the name 'Bloody Hundredth' due to the high loss rate of aircraft and personnel whilst carrying out a number of missions over mainland Europe. Despite these losses the unit was awarded numerous honours and distinctions. After the end of the war the unit underwent numerous role changes within the US Air Force and at times was deactivated but, like a Phoenix rising from the ashes, the powers that be saw opportunities to reactivate it and whatever role it was tasked with was carried out with great success. Today the 100th ARW is a unique unit for three reasons: It is the only air refuelling wing within the United States Air Forces in Europe (USAFE) command; it is the only designated air refuelling wing in the United States Air Force to be based outside of the continental US; and it is the only peacetime USAF unit to have aircraft carrying Second World War-style tail markings as a salute to the unit's heritage.
The 100th ARW comprises a number of other units which form the 100th Operations Group, such as the 100th Maintenance Squadron, the 100th Mission Support Squadron, the 100th Operations Support Squadron and the 351st ARS to name a few. There are fifteen aircraft assigned to the 351st ARS at any one time, with aircraft occasionally being 'swapped' with US based units. When a 'new' aircraft arrives it undergoes a close and thorough inspection by the maintenance teams of the 100th Maintenance Operations Squadron - this is a process that, in some instances, can take up to three weeks to complete. Any faults or defects that are found are logged and rectified and the aircraft has the 351st ARS/100th ARW unit markings applied to it. Only after this inspection has been completed can the aircraft enter active squadron service.
The 100th ARW's area of operations encompasses Iceland, the UK, mainland Europe, Russia, and all of Africa, with the exception being the Horn of Africa which is the responsibility of Central Command (CENTCOM). In the UK, the 351st ARS regularly provides tanker support and training to the F-15 squadrons of the 48th Fighter Wing (FW) at RAF Lakenheath. Within the European theatre of operations, the unit also interacts with the USAFE units of the 52nd FW based at Spangdahlem AB in Germany and the 31st FW based at Aviano AB in Italy, which call upon the services of the 351st ARS approximately three or four times a month. At Geilenkirchen AB in Germany, US-based KC-135 units often operate from the base on a TDY (temporary deployment) basis and interestingly there is no interaction between these units and the 351st ARS. Whilst the primary fuel transfer method is through the KC-135's 'flying boom' some of the 'R models have been modified to MPRS (Multi Point Refuelling System) standard and fitted with Hose and Drogue Units (HDU) under each wingtip. These units are Mark 32B HDUs supplied by Flight Refuelling Ltd and their installation necessitates each aircraft to undergo a major refit, have modifications made to the fuselage and wing fuel tanks, the installation of additional fuel control systems, indicators and circuit breakers. The addition of the HDUs provides the KC-135R with the versatility to refuel the NATO and US Navy aircraft types that use a refuelling probe as well as receptacle aircraft during a single mission. Both HDUs can be used to simultaneously refuel two probe equipped aircraft with each HDU providing a nominal continuous flow rate of 400 gallons per minute although the flow rate may vary depending on the back pressure of the receiver aircraft.
The boom can also be modified to utilise the drogue and basket system with the drogue being trailed behind the lowered boom. These modified aircraft regularly support the air refuelling requirements of other NATO air forces including Belgium, the Netherlands, Denmark and Germany. Of course the 100th ARW is not confined to just refuelling fighter aircraft - any aircraft transiting the Atlantic that requires air refuelling can call upon the 100th ARW and these could be Medevac flights from the Middle East and/or Africa, cargo/transport aircraft and even bomber aircraft. Such is the workload of the unit that in 2005/2006 the 100th ARW offloaded approximately 98 million pounds of fuel, and flew approximately 3,300 sorties to amass roughly 7,000 hours flying time. Looking at those statistics it's easy to understand why a posting to the 100th ARW is one which many in the air refuelling community would like to have as it provides the opportunity to train and refuel different aircraft types on a regular basis, something which US-based air refuelling units do not enjoy. For the personnel of the 100th ARW, the average stay with the unit is a three-year option but this is dependant on individual circumstances. The officers and enlisted personnel with spouses and children stay for three years whilst those who are unaccompanied stay for two years, but it's not uncommon for most people who have a two-year option to extend it to three years.
A typical 351st ARS training mission begins with the crew receiving their mission brief followed by an in-depth crew discussion covering a host of subjects including weather conditions, receiver aircraft type, fuel loads, altitudes, timings, NOTAMs, etc. The boom operator is tasked with obtaining details of the receiver aircraft call signs; this is done prior to mission departure. When the crew arrive at their aircraft the pilots check the maintenance records with the crew chief. The pilots and crew chief then inspect the aircraft for any possible faults such as hydraulic fluid leaks or damage to the wings, engines and external fuselage. If the pilots are satisfied with the aircraft condition they sign off the crew chief's paperwork and board the aircraft.
Once onboard the crew commence their pre-flight checks. This they do in a methodical and organised manner, carefully following each procedure on the checklist. There is no opportunity or possibility to take a short cut with the checklist, it has to be followed step by step as the safety of the crew and aircraft is paramount. As they work through their checklist they request engine start with the control tower. When engine start is approved the four CFM56-2 engines are slowly brought to life one by one, the crew carefully monitoring the engine instruments in the cockpit whilst continuing with the other pre-flight checks. When all four engines are operating as they should be and there are no other problems the crew contact the tower to request clearance to taxi to the runway. Once the control tower gives departure clearance the aircraft will depart, steadily climbing to its agreed altitude, heading out to a pre-designated air-to-air refuelling area (AARA). Upon arrival at the AARA the aircraft establishes a race track pattern orbit, the boom operator or 'boomer' conducts a series of checks to make sure the boom is functioning properly. This also enables the pilots to get an indication of how the aircraft handles in the present weather conditions with the boom deployed. The boomer also passes the information regarding the callsigns of the receiver aircraft to the pilots who, when requested, pass the details to the relevant sector air traffic controllers. With the orbit established, the tanker awaits the first of the receiver aircraft.
The receiver aircraft are cleared by the sector air traffic controllers to make contact with the tanker. The pilots maintain a visual lookout for the receivers as well as keeping an eye on their traffic alert and collision avoidance system (TCAS) display in the cockpit as this will display their location. The pilot of the receiver aircraft makes direct contact with the tanker pilots and approaches the tanker from behind and 1,000 feet below the tanker's altitude. Fighter aircraft take up position next to the tanker, holding off the right wing, and await clearance to approach the lowered boom. The tanker pilots rely on the boom operator to keep them informed as to what is happening at the rear of the aircraft. Throughout the refueling process, the intercom system is used to maintain the lines of communication between the boom operator, the tanker pilots and the receiving aircraft. The air refuelling environment is both a complex and a dangerous one as using the boom involves two aircraft making contact via the end of said refuelling boom with both aircraft flying in variable lighting and weather conditions through turbulent air and with speeds at hundreds of miles an hour. There is a high risk of damage to the receiver aircraft from the boom - they are subjected to scratches and/or dents and, depending on the receiving aircraft type, larger scratches and/or dents can reduce stealth characteristics. Another potential hazard is fire in the cockpit of the receiver aircraft, which can be caused by the boom probe puncturing the receiver aircraft's canopy, causing electrical fires to start. If the receiver aircraft gets too close to the tanker, the boom operator will call for a breakaway, the tanker pilot will increase speed, and the receiving pilot will reduce his speed and drop down and away from the tanker.
Laying on a couch, in a prone position, face downwards, with his head supported by a chin rest, the boom operator has an excellent view from the window, and with the boom lowered calls the receiver aircraft to the boom. The boom operator is constantly calling instructions and assurances to the pilot of the receiver aircraft, and as the receiver aircraft nears the boom the operator manoeuvres it towards the receiver aircraft's receptacle using his left hand on the joystick, calling out distances in feet before the boom makes contact. Once contact has been made the pre-arranged amount of fuel is offloaded, the flow being controlled by either the pilot or co-pilot. Fuel offload time is dependant upon the receiver aircraft - for instance, an F-15 can receive up to 4,500lbs of fuel in about a minute and a half if all the fuel pumps of the F-15 are activated; offload times for a C-5 Galaxy will be significantly different. If the tanker aircraft reaches the end of its orbit pattern and a receiver is 'hooked' to the boom, both aircraft will make the turn together and fuel will still be offloaded. Once the fuel has been offloaded, the boom is retracted and the receiver aircraft drops down and backwards. If the receivers are fighter aircraft they will drop down and backwards and accelerate out to the left wing where they hold for a short time before continuing on their own mission. The boom operator will make a record in his notebook of the aircraft type, the call sign, the serial number and the fuel quantity offloaded. The fuel offload data is then cross referenced with the pilot's own fuel offload data during the mission debrief. Fuel is offloaded from one of the three main internal fuel tanks, usually the central tank, and as more fuel is offloaded the centre of gravity of the tanker changes. To compensate for this, the pilots transfer fuel loads from the front and aft internal tanks.
The whole process is then repeated each time a receiver aircraft calls on the tanker. With the mission at an end, the tanker returns to base, the aircraft is parked up, engines and systems are shut down and the crew head for their mission debriefing.
Certainly the KC-135R is going to be around for a good number of years yet (see 'Still passing gas'), but nothing lasts forever and the USAF have already begun considering their options for its replacement. The tanker community has a saying "Nobody kicks ass without tanker gas nobody!" (NKAWTG N!) - a statement which is both very true and appropriate.
The author extends his grateful thanks to the following who made this article possible: the 100th OG; Capt. T. Wright and Capt. J Humphries of the 100th ARW Public Affairs Office; Maj. J. Harbour, Capt A. Wright, SSGT W. Baker, A1C M. Miranda; the 48th FW crews of F-15Cs and F15Es call signs 'Akita 51/52', 'Bolar 51/52/53', 'Bones 11/12', 'Pistol 11/12/13', and 'Ratch 31/32'.