A Royal Air Force's C-17 Globemaster III military transport aircraft performed a daring maneuver
in the skies above the United Kingdom on July 29, 2021.
As footage from that day shows, the aircraft engaged its thrust reversers to drop from
a cruising altitude of 30,000 feet to 5,000 feet in just two minutes.
The thrust reversers, customarily used to slow the aircraft down to help the warplane
land on space-limited runways, are instead used to dramatically lose altitude in mid-flight.
The maneuver, known as a reverse idle tactical descent, has thus far only been used for logistical
training purposes, providing a spectacular sight every time.
Such rehearsals have showcased the Globemaster III’s incredible agility and maneuverability
while it performs a unique feat that could be used to pierce into hostile territories
in an aggressive, sudden, and yet safe fashion…
A Legendary Air Carrier
The Boeing C-17 Globemaster III is a military transport aircraft designed for strategic
airlift operations.
With a wingspan of 169 feet and a maximum takeoff weight of 585,000 pounds, the C-17
can carry oversized cargo, equipment, and troops to remote locations worldwide.
It is powered by four mighty engines and has a range of over 2,400 nautical miles, making
it ideal for long-range missions.
The C-17 has been used in various military operations, including peacekeeping missions,
humanitarian relief efforts, and combat operations.
Its rugged design and advanced avionics system make it capable of operating in multiple environments,
from desert heat to arctic cold.
In addition, the aircraft is equipped with a state-of-the-art cargo handling system that
allows for quick and efficient loading and unloading of cargo and the ability to airdrop
supplies.
The Globemaster III has been a key asset to the US military and its allies, with many
countries using the aircraft to support their air mobility needs.
As such, it has been used in several high-profile operations, including Operation Desert Storm,
Operation Iraqi Freedom, and Operation Enduring Freedom, as well as in various humanitarian
missions, including disaster relief efforts in Haiti, Japan, and the Philippines.
One critical capability is that the aircraft's engines are capable of thrust reversal.
This specialized function provides the warplane with swift deceleration for landing and performing
specific maneuvers, one of which is the daring reverse idle tactical descent.
Thrust Reversal
The C-17 Globemaster III has gained renewed interest in social media because of a recent
video showing an impressive short-field tactical departure where a US Air Force pilot took
off from Portland International Airport with a takeoff distance of fewer than 2,500 feet.
The video shows the colossal metal beast taking off with an incredibly short distance in a
feat that appears to defy gravity itself.
The warplane then levels off just a few dozen feet above the runway to perform a steep and
dramatic climb called a low-altitude tactical departure, used to negate small-arms threats
near an airfield during a combat scenario.
The thrust reversers, located on the aircraft's four Pratt & Whitney F117-PW-100 turbofan
engines, are typically used to deflect airflow upward and forward during landing to reduce
the distance needed to stop and provide access to smaller airstrips.
The C-17's thrust reversers are incredibly powerful and designed to deflect the airflow
from the engines upward and forward when landing, reducing the distance needed to stop to about
3,000 feet.
This is helpful when performing landings in small and less developed runways such as those
found in several war zones.
On the ground, the thrust reversers also keep jet wash away from the aircraft's rear, making
it easier to load and unload cargo via the ramp.
The thrust reversers are even powerful enough to propel the aircraft backward on the ground,
which can be useful for reversing on shorter airstrips.
And they can push a fully loaded C-17 up a two-degree slope if required.
Moreover, the thrust reversers have another less-known function that has been barely tested.
In it, they are used mid-flight to drastically lose altitude and achieve a spectacularly
swift descent.
A recent video from the RAF's C-17 operator, No. 99 Squadron, showed this capability during
a training sortie on July 29, 2021.
The video showcases a reverse idle tactical descent during a seven-hour flight around
the United Kingdom.
Test’s Limitations
The incredible footage shows the thrust reversers engaged to allow for a maximum-rate descent,
causing the aircraft to drop from 30,000 feet to 5,000 feet in just two minutes, an incredibly
swift loss in altitude that very few large aircraft can achieve safely.
Interestingly, the RAF crew claimed that what was accomplished in the test was far from
the aircraft's maximum performance capabilities regarding descent rate, which suggests the
Globemaster III could descend even faster if needed.
In the video, the pilots can be seen maintaining the aircraft's speed by adjusting its attitude,
as glimpsed by the relationship between the horizon and the wing's angle.
The crew of 99 Squadron explains: (QUOTE): "The low nose attitude needed to maintain
speed is part of what causes the massive rate of descent.
Speed brakes are also used, for an even higher descent rate.
Higher speed also means higher rates of descent."
According to the crew, the maneuver is being tested for: (QUOTE): "Getting on the deck
as quickly as possible."
They also made it clear that the tests did not include procedures for emergency or combat
scenarios: (QUOTE) "It is unlikely to be used in an emergency due to the highly dynamic
nature of it, but you never know."
The crew's comments, however, have not been enough to stop some experts from entertaining
the idea of its combat use.
Many combat aircraft enthusiasts have jumped at the possibility of using the thrust reversers’
ability to enable a quick descent in situations where the aircraft needs to quickly drop from
a high altitude to a low one, such as entering into or approaching hostile territory without
flying over dangerous areas that a typical descent would require.
Extreme Yet Safe
The drastic rate of descent is spectacular to behold and is said to be a safe and reliable
operation that does not exert excessive stress on the crew apart from some moderate vibration.
As one of the crewmembers put it: (QUOTE) "From the cockpit, the amount the wings and
nacelles shake with all four [engines] in reverse is also quite incredible."
Otherwise, the automatic cabin pressurization system ensures the maneuver is relatively
forgiving on the ears and body, as the forces imparted are between 0.0 and 2.0G.
Pilot Andy Netherwood described the feat as: (QUOTE) “A great party trick and fun to
fly," stressing that the maneuver is easy and does not pose a stall risk.
The process involves slowing down, configuring the aircraft, engaging the thrust reversers,
and following the flight director's instructions.
Considering that the C-17 Globemaster III’s short-field and low-altitude tactical departure
capabilities are intended to keep the aircraft safe even when operating in hostile territories
or directly under fire, it is not hard to imagine that the reverse idle tactical descent
function could also be used to decent into hostile environments in a dramatic way that
helps the warplane avoid enemy fire.
Only time will tell if the incredible maneuver depicted in the footage will have combat applications.
Still, for now, it highlights the aircraft's versatility and why it is one of the most
sought-after airlift solutions for military forces around the world.
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