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.
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.
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.
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:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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