--- title: "The Unusual Asymmetry Of The C-17 Globemaster III" description: "The C-17’s mismatched under-fuselage sponsons put it in an exotic category of asymmetric fixed-wing aircraft designs. The C-17’s mismatched under-fuselage sponsons put it in an exotic category of asymmetric fixed-wing aircraft designs." date: "2025-09-07" modified: "2025-09-07" authors: - name: "Thomas Newdick" job_title: "Staff Writer" link: "https://www.twz.com/authors/thomas-newdick.md" url: "https://www.twz.com/air/the-unusual-asymmetry-of-the-c-17-globemaster-ii" categories: - "Air" - "Air Forces" - "C-17" - "Military Aviation History" - "Transports" - "U.S. Air Force" --- # The Unusual Asymmetry Of The C-17 Globemaster III ![A C-17 Globemaster III assigned to the 164th Airlift Wing, Memphis Air National Guard, Tennessee departs from Joint Base Elmendorf-Richardson, Alaska providing airlift support for 11th Airborne Division soldiers participating in Talisman Sabre 25, July 13, 2025. Talisman Sabre 25 is a bilateral exercise with multinational participation hosted by Australia, in partnership with U.S. Indo-Pacific Command. The Talisman Sabre series is the principal Australian-U.S. military training activity focused on mid-intensity, high-end war fighting to ensure our forces are capable, interoperable, deployable on short notice and combat-ready.]() *U.S. Air Force photo by Sheila deVera* The annals of aviation history are scattered with asymmetric aircraft designs, some of them notably [more extreme]() than others. Perhaps less well-known among this diverse group is the U.S. Air Force’s airlift specialist, the [C-17A Globemaster III](). The sheer size of this aircraft means that its lopsidedness is less often seen by casual observers, especially when it’s on the ground. But once spotted, the feature is hard to ignore and is worth a closer look. ![A U.S. Air Force C-17 Globemaster III aircraft performs a fly by prior to the “Thunder Over the Bay” Air Show at Travis Air Force Base, California, March 29, 2019. In addition to the C-17 Globemaster III, the two-day event featured performances by the U.S. Air Force Thunderbirds aerial demonstration team, U.S. Army Golden Knights parachute team, flyovers, and static displays. The event honored hometown heroes like police officers, firefighters, nurses, teachers and ordinary citizens whose selfless work made their communities safer and enhanced the quality of life. (U.S. Air Force photo by Heide Couch)]() *A U.S. Air Force C-17 performs a flyby. In this view, the two distinctly different-length landing gear sponsons are obvious. *U.S. Air Force photo by Heide Couch* Heide Couch* In fact, this oddity is just one of many interesting [features](), [capabilities](), and [operational exploits]() associated with the C-17. For example, *TWZ* [has previously explored]() how the aircraft’s thrust reversers, normally used to deflect the airflow from the main engines to provide braking when landing, can also be employed in flight, for a dramatic “reverse idle tactical descent.” Meanwhile, wider attention was brought to the C-17’s asymmetry in a recent thread on the social media platform X, posted by [@SR\_Planespotter](), a friend of *TWZ*. A partial underside view of a C-17 was provided alongside a shot of the [C-5 Galaxy](), which features an offset aerial refueling receptacle. https://twitter.com/SR_Planespotter/status/1961622414409764960 Turning to the C-17, it’s immediately obvious from this angle that the two large fairings that run down either side of the lower fuselage are of significantly different lengths. These sponsons accommodate the main landing gear, which is itself worthy of note. On the C-17, the main gear has two struts, with three heavy-duty wheels on each. The complex mechanism that allows these wheels to be retracted is something of a technological marvel, as you can see in the videos below. Overall, the landing gear is designed to ensure the C-17 can make high-angle, steep approaches, allowing it to operate into small, austere airfields and short runways even when heavily loaded. https://www.youtube.com/shorts/fimPud98LGA https://www.youtube.com/watch?v=E-ozJBZU8zg As for the discrepancy in length between the two sponsons, this is due to the C-17’s auxiliary power unit (APU) being installed in the forward part of the sponson on the right-hand side. ***A video showing a U.S. Air Force C-17 flying at low level through the Mach Loop in the United Kingdom provides another good view of the underside sponsons:*** https://www.youtube.com/watch?v=7DqiWG61Nzs&t=1s In the C-17, the APU is a self-contained gas turbine engine, drawing gas from the aircraft’s main fuel system. The APU provides electricity as well as hydraulic pressure. In this way, all the aircraft’s doors and the rear ramp, plus the various control surfaces, can be fully operated without using the four Pratt & Whitney F117-PW-100 turbofan main engines. The same APU system also delivers pneumatic pressure, which is used for the environmental/air-conditioning and de-icing/anti-icing systems. ![The first US Air Force C-17 Globemaster arrives into Tacloban delivering aid supplies. \*\*\* Local Caption \*\*\* Defence has established OPERATION PHILIPPINES ASSIST to support international Humanitarian and Disaster Relief (HADR) operations in the wake of Typhoon Haiyan. A Royal Australian Air Force C-17A Globemaster along with a C-130J Hercules departed Darwin on Wednesday 13 November to support the deployment of a civilian Australian Medical Assistance Team (AusMAT), provided by the Department of Health. The two heavy lift aircraft transported the 36 strong civilian AusMAT and some 22 tonnes of associated equipment. OPERATION PHILIPPINES ASSIST has also been supported by a RAAF Mobile Air Load Team (MALT), and an Aircraft Security Operations Team. These personnel were responsible for enabling the delivery of the medical specialists and their equipment to the Philippines. The ADF stands ready to respond to any further request for assistance.]() *Shadows on the underside of a U.S. Air Force C-17 emphasize the asymmetric sponsons. *Australian Department of Defense* CPL Glen McCarthy* As well as the APU, the right main landing gear sponson features a ram air turbine (RAT), which can be extended in the case of a major power failure, ensuring that there’s hydraulic system power for the flight controls. ![]() *Paratroopers with the 4th Brigade Combat Team, 25th Infantry Division from Joint Base Elmendorf-Richardson, Alaska, jump from a U.S. Air Force C-17. *Australian Department of Defense* UNKNOWN* So, while the asymmetric nature of the C-17 may not always be obvious, there’s a very logical reason behind it. The same is the case for various other asymmetric fixed-wing aircraft through the ages (helicopters are a different matter altogether, with the majority using an asymmetric tail rotor as a matter of course). Similarly, many propeller-driven aircraft feature more modest asymmetry, such as offset vertical tail surfaces, to counteract torque produced by the rotating prop. https://twitter.com/aeroweanie/status/1961888368314495366 There have also been a surprising number of aircraft whose asymmetry is bestowed by having an offset cockpit. The Cold War-era British de Havilland Sea Vixen carrier fighter is perhaps the best example, with the pilot’s cockpit set on the left and the observer’s position more or less ‘buried’ on the right. This was supposed to provide the observer (navigator) with a better working environment to monitor the radar scope, but it was otherwise hardly conducive to comfort. ![The second before take off from R.N. Carner HMAS Eagle as the Catapult crew run from underneath a Sea Vixen jet fighter. August 03, 1971. (Photo by George Lipman/Fairfax Media via Getty Images).]() *A Sea Vixen, seconds before takeoff from the carrier HMS *Eagle*. *Photo by George Lipman/Fairfax Media via Getty Images* Fairfax Media Archives* Then there have been the various aircraft types with asymmetric landing gear, especially when it comes to the nose undercarriage. Most famous is perhaps the [A-10 Thunderbolt II]() attack aircraft, with the nose leg offset to accommodate the enormous [GAU-8/A Avenger]() 30mm rotary cannon. ![A U.S. Air Force A-10 Thunderbolt II from the Idaho Air National Guard’s 124th Fighter Wing is painted with a heritage WWII paint scheme at the Air National Guard paint facility in Sioux City, Iowa. The paint scheme is designed to replicate the look of the original P-47 Thunderbolt as it appeared during the 2nd World War. The 124th Fighter Wing conceived the idea in order to commemorate the unit’s 75th anniversary and lineage to their predecessor, the 405th Fighter Squadron. U.S. Air National Guard photo: Senior Master Sgt. Vincent De Groot]() *A-10 Thunderbolt II. *U.S. Air National Guard photo by Senior Master Sgt. Vincent De Groot* Vincent De Groot* Less well known is the [Hawker Siddeley Trident]() airliner, of the 1960s era, which had its nose gear offset by a full two feet to make space for the bulky, primitive automatic approach and landing equipment that was installed in the bottom of the forward fuselage. https://twitter.com/LebanonJets/status/1961672303265173825 The Scaled Composites ARES (Agile Responsive Effective Support), built to perform a similar close air support role to the A-10, ended up even more radically lopsided. In this case, a 25mm rotary gun was mounted on the right, with the engine intake on the left. A special recess in the nose was intended to divert gun gases, canceling asymmetric recoil. The engine was also set at an angle to avoid the same gases entering it, while various ducts redirected the engine exhaust, reducing the infrared signature. The aircraft is still active today [as a testbed](). ![]() *Scaled Composites ARES. *Scott Lowe** ![]() *This view of the ARES reveals its offset engine. *Scaled Composites** We can’t finish this brief study without looking at perhaps the most extreme example of all. The World War II-era German Blohm & Voss BV 141 was a wildly unorthodox tactical reconnaissance aircraft. In this case, to provide the crew with the best visibility, the fuselage was located entirely separately, starboard of the engine and tail unit. ![]() *Blohm & Voss BV 141. *Bundesarchiv** So, this is how the C-17 airlifter takes its place among some other standout asymmetric aircraft designs. Let us know which skewed flying machines we might have missed. ***Update, September 15:*** Thanks to an email from an individual who was involved in the C-17 flight-test program, we now have a definitive answer on why the decision was made to install the APU in the right-hand-side landing gear sponson, rather than in a more conventional (symmetrical) location. While they would prefer to remain anonymous, this is the explanation in their own words, which has only been slightly edited for clarity: *“When they first designed the aircraft, it was supposed to have composite wings instead of the aluminum-lithium alloy it ended up using. At some point, they realized that an aircraft that was supposed to operate just behind the battle line should be easily field-repairable. Any damage to a composite wing would require vacuum bagging and, most worryingly, a cure time of several hours. Whereas an alloy wing could have a scab patch slapped on in a matter of minutes with basic sheet-metal tools.* *“The APU was supposed to go into the huge empty compartment under the vertical stabilizer, with access through the hatch above the cargo door (not to be confused with the cargo ramp). Changing to the alloy wing altered the center of gravity and required moving the APU out of the tail to its current location.”* *Contact the author: thomas@thewarzone.com* ## Author Thomas Newdick is a staff writer at *TWZ*, where he covers military aviation, defense technology, weapons systems, and international security. Based in Berlin, Germany, he reports on conflicts, military modernization efforts, and emerging aerospace technologies around the world, with a particular interest in airpower and its role in contemporary warfare. His reporting is informed by deep expertise in modern and historical airpower, particularly in Europe, with a focus on military aviation, air campaigns, and aerospace developments across the continent and beyond. Over a journalism career spanning more than 25 years, Thomas has become known for making complex defense and aerospace topics accessible to a broad audience. His reporting combines technical expertise, historical context, and a focus on the real-world operational and strategic implications of military developments. ### Author social links [Twitter]()