35,546 Gallons: How the C-17 Carries Enough Fuel to Cross Oceans Nonstop

The C-17 Globemaster III can carry 35,546 gallons of JP-8 fuel—over 240,000 pounds when fully loaded. This massive fuel capacity is what gives the aircraft its strategic reach, enabling nonstop flights from the continental United States to virtually anywhere in the world. But managing that much fuel safely and efficiently requires sophisticated engineering that most passengers and cargo never see.

Fuel Capacity and Distribution

Tank Layout

The C-17’s fuel is stored in integral wing tanks, meaning the wing structure itself forms the fuel tank walls. There are no separate rubber bladders or rigid containers—the sealed wing skin contains the fuel directly. This approach maximizes capacity while minimizing weight.

The fuel system includes:

• Four main tanks in the wing center section
• Two reserve tanks (one in each wing)
• Auxiliary tanks in the wing outer sections
• Surge tanks at the wingtips for overflow and venting

The total capacity of 35,546 gallons translates to approximately 237,000 pounds of fuel at standard fuel density. That’s more fuel than many regional jets weigh fully loaded with passengers and cargo.

Fuel Weight Considerations

With a maximum takeoff weight of 585,000 pounds and an operating empty weight around 282,500 pounds, fuel and payload share the roughly 300,000 pounds of available capacity. A fully fueled C-17 carrying maximum fuel can still transport about 50,000 pounds of cargo—enough for a significant tactical load.

For maximum cargo missions, crews upload less fuel and plan for fuel stops. The trade-off between fuel and payload is a constant consideration in mission planning.

Fuel Management System

Automatic Operation

The C-17’s Fuel Management System (FMS) automatically maintains proper fuel distribution as the aircraft consumes fuel. This isn’t just about keeping the engines fed—it’s about maintaining the aircraft’s center of gravity within acceptable limits.

As fuel burns from the main tanks, the system automatically transfers fuel from auxiliary tanks to maintain balance. Pilots can monitor this process but rarely need to intervene—the automation handles normal operations flawlessly.

CG Management

Aircraft center of gravity (CG) must stay within a defined envelope for safe flight. With 240,000 pounds of fuel distributed across the wingspan, where that fuel is located dramatically affects CG. The fuel management system continuously calculates fuel distribution and commands transfers to keep CG centered.

This automatic CG management is particularly important during long flights as fuel burns. What started as a properly balanced fuel load could drift out of limits without active management.

Fuel Pumps and Plumbing

Boost Pumps

Each main tank contains multiple electric boost pumps that pressurize fuel flow to the engines. The redundancy ensures engine fuel supply even if individual pumps fail. The boost pumps also serve a secondary purpose: keeping fuel under pressure prevents vapor formation at high altitude, where ambient pressure is low.

Engine Feed

Fuel flows from the main tanks through feed lines to each of the four Pratt & Whitney F117 engines. Each engine has dedicated fuel lines and pumps, ensuring that a problem in one engine’s fuel supply doesn’t affect the others.

The engines’ own fuel pumps, driven by the engine accessories, provide the final boost that delivers fuel to the combustors at the required pressure and flow rate.

Crossfeed Capability

The crossfeed system allows fuel from any tank to feed any engine. This capability is essential for handling abnormal situations—if one tank develops a leak, fuel from the remaining tanks can still supply all engines. The crossfeed valves are electrically controlled from the cockpit.

Aerial Refueling

The C-17 is equipped for aerial refueling via a receptacle mounted on top of the forward fuselage. This capability dramatically extends the aircraft’s range and endurance, enabling truly global operations without landing.

The Receptacle

The Universal Aerial Refueling Receptacle Slipway Installation (UARRSI) accepts fuel from Air Force KC-135 and KC-46 tankers using the flying boom method. During refueling, a boom operator on the tanker “flies” the boom into the C-17’s receptacle, where it locks in place for fuel transfer.

Transfer Rates

Fuel transfers rapidly during aerial refueling—up to 1,000 gallons per minute. At that rate, the C-17 can take on tens of thousands of pounds of fuel in just minutes of connected time. The fuel management system directs incoming fuel to appropriate tanks to maintain CG.

Mission Impact

Aerial refueling transforms C-17 mission possibilities. A sortie that might otherwise require multiple fuel stops can be completed nonstop with tanker support. Time-critical missions—medical evacuations, rapid response deployments—benefit enormously from this capability.

Fuel Jettison

In emergency situations, the C-17 can jettison fuel overboard to reduce weight for landing. Maximum landing weight is lower than maximum takeoff weight, so an aircraft that needs to return shortly after a heavyweight takeoff might need to dump fuel.

Fuel dumps through jettison pipes at the trailing edge of each wing, well away from the engines and other ignition sources. The system can dump thousands of pounds of fuel per minute, bringing the aircraft to landing weight relatively quickly.

Fuel jettison is a last resort—it’s expensive and has environmental implications. Crews will typically burn fuel down through holding patterns if time permits.

Fuel Quantity Indication

Pilots monitor fuel through the Fuel Quantity Indication System (FQIS), which uses capacitance probes in each tank to measure fuel level. The system accounts for fuel temperature and density, providing accurate weight readings rather than just volume.

The EICAS display shows total fuel quantity, individual tank quantities, and fuel flow rates to each engine. The system also calculates remaining range and endurance based on current consumption rates.

Low Fuel Warnings

The system generates caution and warning messages as fuel reaches critical levels. These alerts give crews time to divert to alternate airports or request tanker support before the situation becomes an emergency.

Single Point Refueling

On the ground, the C-17 refuels through single point receptacles on the underside of the wing. High-pressure fuel from a tanker truck or hydrant system flows through these connections, filling all tanks through a single hookup.

The single point system dramatically speeds ground refueling compared to over-wing refueling of individual tanks. A C-17 can take on a full fuel load in under 30 minutes through single point refueling—essential for quick turns during surge operations.

Fuel Temperature Management

Fuel in the wings experiences significant temperature variations during flight. At cruise altitude, outside air temperatures drop to -60°F or colder. Fuel cools toward these temperatures, becoming more viscous and potentially reaching its gel point in extreme cold.

The fuel quantity system monitors fuel temperature. If fuel approaches critical cold temperatures, crews can descend to warmer altitudes or use fuel heating if available. Proper mission planning considers expected fuel temperatures over long routes.

Why It Matters

The fuel system is what makes the C-17’s strategic mission possible. The ability to carry enough fuel to fly 5,000+ miles nonstop, coupled with aerial refueling capability, gives the aircraft truly global reach. Whether delivering cargo to a remote airstrip in Africa or evacuating patients from a disaster zone in Asia, the C-17’s fuel capacity enables missions that would require multiple aircraft or fuel stops with other airlifters.

For C-17 crews, fuel management is a constant consideration. Every mission involves calculating fuel requirements, monitoring consumption, and sometimes making real-time decisions about diversions or tanker rendezvous. Understanding the fuel system’s capabilities and limitations is essential knowledge for anyone flying or maintaining this aircraft.