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A-10 CAS aircraft
The A-10 Thunderbolt II is the first US Air Force (USAF) aircraft specially designed for close air support (CAS) of ground forces. The Warthog is a simple, effective and survivable twin-engine jet aircraft that can be used against all ground targets, including tanks and other armored vehicles.
The aircraft can survive direct hits from armor-piercing and high explosive projectiles up to 23mm. Their self-sealing fuel cells are protected by internal and external foam. Manual systems back up their redundant hydraulic flight-control systems. This permits pilots to fly and land when hydraulic power is lost.
How the A-10 can fly when it loses hydraulic systems?
Lynn Taylor, former A-10 pilot, explains on Quora how the Warthog can fly when it loses hydraulics (like did by then-Capt. Kim Campbell on Apr. 7, 2003 when her A-10 was badly damaged during Operation Iraqi Freedom, as the main picture in this post shows).
‘When the Hawg loses hydraulics, it goes into fly-by-wire mode.
‘Of course, this isn’t the new-fangled electronic “fly-by-wire” like you have on the F-16 and newer fighter jets. Ohhhhh no. This baby goes old school, with actual wires that move. Cables, really. And pulleys. Cables and pulleys. It’s all very technical.
‘Usually this would happen as a result of battle damage that perforated your hydraulic lines, but it could happen if there is some weird multiple failure of both hydraulic systems. You can also choose to enter this flight mode by flipping a switch. Trying this flight mode out by flipping that switch is part of A-10 training, and it isn’t done lightly.
‘This flight mode is called “manual reversion,” and is a backup to the backup in case you’re having an especially bad day. The way it works is that there are, literally, cables and pulleys, that run from the control stick, all the way out to the control surfaces on the wings and tail.
Flying the A-10 without hydraulic systems
‘Now, those cables don’t move the control surfaces themselves. Those barn doors are pretty weighty, and wind resistance would make it nigh impossible for anyone but King Kong to manhandle the jet around the sky if that’s what you had to do. Instead, the cables actually move the trim tabs on the control surfaces.
‘This picture shows the back side of the right wing of an A-10, a little over halfway out. To the left is a flap. To the right is the aileron/speed brake combo. The bottom edge is the aileron trim tab, with a connector rod on the top, and a counterweight on the bottom.’
‘Usually, the trim tab is controlled with a little knob on the stick, and it helps to “trim” the aircraft to maintain a particular attitude in flight. In manual reversion, that connector rod becomes the mechanism to push and pull the trim tab. The trim tab then acts much like a miniature aileron, with the aileron acting much like a wing. After moving the trim tab, aerodynamic forces act on the aileron and move it, then the aileron does its normal job and moves the wing, which then moves the jet.
‘Pretty cool, huh?
‘Here’s a wider shot showing the barn doors fully open (see above). You can see the trim tab and counterweight on the top right section of the aileron. There are similar devices on the outer trailing edges of the elevators (see below). (IIRC, there are no trim tabs for the rudder).
Intrepid Hawg drivers
‘Of course, driving the Hawg this way feels a lot like driving a semi-truck without power steering, but it will at least get you back over good guy land before you have to step over the side and give the jet back to the taxpayers.
‘Some intrepid Hawg drivers have even landed the jet in manual reversion, but, according to the manual, “this is not recommended, and should only be attempted in ideal conditions.” We’d always joke that, any time you have to fly in manual reversion, you’re already not in “ideal conditions.”’
Landing the A-10 without hydraulic systems
‘So, landing in manual reversion can be done, but it’s a tricky proposition, and not something you practice. Not everyone who has attempted it lived to tell the tale. You can see a few instances of manual reversion landings over here at How does the A-10 stack against MANPADS?
‘The manual reversion flight mode is another one of those genius ideas designed into this beast by the amazing engineers at Fairchild Republic. It’s another trick in the bag of one of the most survivable aircraft ever built.’
Photo credit: Burkhard Domke and U.S. Air Force