Extreme survivability is the hallmark of the A-10. Designed from the ground up for redundancy protection to battle damage, the A-10 was envisioned to operate and survive the low-level world of high-intensity AAA gun barrages, IR and radar-guided surface-to-air missiles (SAMs), and the ever-present threat of enemy interceptors.
In such an environment, the pilot enjoys (and requires) the survivability built into the airframe: redundant hydraulic, electrical, and fuel lines in widely dispersed protected ducts; triple spars on wings and horizontal tailplanes; dual engines close to fuselage centerline, which were set high above the fuselage to limit FOD ingestion on primitive forward operating areas; self sealing fuel tanks; left-right parts interchangability; and most importantly, a direct mechanical cable linkage for redundant backup flight controls. Cables were chosen for this system backup due to the higher rate of failure (jamming) of control rods with battle damage. The high 85% bypass turbofan design directed cold bypass air upwards at a 10 degree angle to mix with and cool hot jet exhaust; further, the twin vertical stabilizers masked the heat signature of the aircraft from the sides, reducing the potential targeting threat from heat-seeking missile launches.
Former A-10A Flight Commander Ed Herlik relates a personal incident that illustrates the durability of this plane:
"From my own experience, the jet I inherited in England actually ran over and killed a motorized glider before I got my name on the 'Hog. The pilot knew he hit something but it wasn’t until he got home and saw the paint and propeller marks on the belly that he knew he’d had a midair. The other plane didn’t fare so well..."
The unswept straight wing incorporates a high lift camber, and permits increased strength. Good lookdown visibility is insured by a cockpit set high and forward on the fuselage; when threatened, the pilot finds ready comfort in the nearly three-quarter ton titanium “bathtub” armor surrounding the cockpit. Composed of alloy plates bolted together with a multi-layered nylon fiber shell, this tub can withstand direct 23mm projectile strikes from the Soviet-made ZSU 23-4 quad barrelled radar-guided AAA gun, and even 57mm projectiles <<see NOTE below>>. The titanium tub itself represents 47% of the total armor on the plane—a remaining 37% protects the fuel system. Even the ammo drum for the 30mm cannon has its internal helical ammo delivery system protected.
All this was accomplished in a cockpit that lacked even the simplest autopilot, requiring the A-10 to be flown hands-on at all times. Indeed, it has been said that a Republic F-84 pilot from Korea would feel right at home in the A-10 cockpit... however, the lack of such “typical” avionics on the A-10 is attributable more to the lack of adequate performance and reliability of such “advanced” devices during the 1970s, than a desire on behalf of the design team to return to the past. For targetting, a limited computing bombsight linked to the inertial navigation system was present. It would not be until after Desert Storm that the addition of low-altitude safety and targeting system (LASTE) modifications (begun in 1989) would be completed, providing (at last) an autopilot; a simple radar altimeter coupled to a voice warning system (Bitching Betty); nighttime formation (“slime”) lights; cockpit lighting compatible with night vision goggles; and the same weapons delivery computer as found on the F-16, although the F-16’s radar ranging was not incorporated. The strategic value, albeit late, of these modifications could be immediately seen at the 1991 ‘Gunsmoke’ USAF bombing competition, where the Hogs of the 175th Tactical Fighter Group (Air Nat’l Guard) of Baltimore, MD—fitted with the LASTE mods—flew home with top honors. <<see NOTE below>>
Turn and Burn
The A-10 enjoys an extreme measure of agility and responsiveness that permits it to fly low and slow to employ terrain-masking techniques to thwart enemy defences. Its lower speed, combined with the higher lifting camber of the wing design, permits the A-10A to pull more g-forces at a lower given speed, making the A-10A highly maneuverable and agile. For comparison:
A-10: 3.5g, 180° turn, 320 knots
time to completion: 16 seconds
2,700 ft radius turn
F-16: 6g, 180° turn, 600 knots
time to completion: 17 seconds
3,620 ft radius turn
What these figures state clearly is that the A-10A can out-corner a F-16 Falcon in full afterburner (for ONE turn only!!), assuming similar "clean" underwing configurations, with air-to-air weapons only. This, of course, is not the primary role of the A-10A…
Within the performance envelope of that first turn outlined above, the high lift (high drag also) wing design permits the A-10 to enjoy a lower "corner" velocity—that is, a lower speed at which it can pull max g-forces—relative to the F-16.This higher rate of turn at lower speeds permits the A-10 to perform evasive jinking maneuvers mere feet above the ground, whereas other “fast mover” jets require a greatly elevated performance ceiling and higher g-force penalty. <<before yelling, please see NOTE at bottom of Chapter 12, "Counter-Air Tactics">>
Get Up and Go
In the event of hostilities, the A-10 has been exceptionally configured for rapid deployment in battle. The auxiliary power unit (APU) is built in, removing the need for external power carts and minimizing ground crew interaction. A single-point fuel receptacle, located in the leading edge of the left landing gear pod, permits not only refueling of the two integral wing tanks and the two tandem fuselage tanks, but also allows ‘hot-pitting’ of aircraft, where the pilot remains in the cockpit with engines running. Inflight refueling via a refueling slipway receptacle located on the fuselage in front of the cockpit permits “box and boom” fuel exchanges. Additionally, up to three external drop tanks can be carried.
Internal fuel capacity: 1,650 US gallons. Weight: 10,700 lbs
External fuel capacity (3 600-US gal ferry tanks): 1,800 US gallons. Weight: 11,700 lbs
NOTE: due to the increased form and interference drag penalty induced by the three ferry tanks, A-10As in Ferry configuration often only carry only two tanks.
Hard to Kill
Verification of survivability tests riddled a static A 10A airframe with over 700 rounds of 23mm armor piercing-incendiary (API) and high explosive-incendiary (HEI) shells, and over 100 rounds of other calibers, without causing critical subsystems damage(!). A summary of the survivability test is as follows:
Cockpit armor 430 rounds
GAU-8 Ammo Drum 58 rounds
Underwing Bombs 23 rounds
Wing Fuel Storage 172 rounds
Fuselage Fuel Storage 102 rounds
Aft/Tail Systems 6 rounds
Windshield Panels 24 rounds (NATO 7.62mm API)
NOTES:
Survivability of 57mm projectiles: even though this was specifically listed in the original assessment of survivability test results, a direct contact burst should indeed penetrate (and destroy) the armor of the cockpit and plane. It is more plausible to suggest instead that a proximity (close range) burst may be survivable; although this would, of course, depend on the circumstances…
2-seat Night Fighter Variant: the A-10 design had been designed from the onset by Fairchild to contain a second cockpit without major modification to the airframe, in the area covered by the rear cockpit “turtle” deck immediately behind the ejection seat. In 1978, Fairchild leased back the first of the DT&E aircraft back from the Air Force (serial number 75-01664) for conversion to a Night All Weather (N/AW) YA-10B prototype. The structural changes in this conversion provided the second cockpit, an additional 20 inch extension to vertical tail surfaces (increased stability with the now altered center of gravity), and relocated avionic access bays. No other major changes were required, validating much of the early design sophistication and anticipation for such future modifications. The first test flight occurred May 4, 1979. The N/AW concept sought to extend the A-10’s role beyond that of a pure daylight battlefield resource, providing battlefield commanders an additional capability in severe environmental and tactical conditions. The N/AW included avionics for low altitude penetration, target acquisition. Amazingly, this extended capacity and handling characteristics remained very close to the single-seat A-10, without loss of ammunition, payload hardpoints, or internal fuel capacity, although the titanium cockpit shielding was not extended to the second cockpit in the prototype.
The avionics suite would have been upgraded to include a forward-looking infra-red radar (FLIR) pod, radar-generated terrain contour map, terrain avoidance radar, and key ordnance delivery and flight symbology. The second-seat System Operator had duplicate displays and was responsible for searching targets with the FLIR, and coordinating targets to a moving ground map radar display. Moving targets could have been acquired, identified, and designated at a distance of eight miles in essentially instrument-flying conditions of night, clouds or rain. Initial target location was acquired in a momentary popup and linked via inertial navigation systems to establish a line-of-sight approach. The aircraft would then resume a terrain following mode for optimimum target penetration.
It is unfortunate to note that funding beyond the YA-10B prototype never surfaced, as the LANTIRN avionics system was slated for higher-priority F-16C and F-15E inventories. The lack of further development of the N/AW concept is a striking irony, since two squadrons during Desert Storm, the 74th TFS (Flying Tigers) and the 355th TFS (Falcons), had to develop their own program of exclusively night interdiction, without the benefit of any of the avionics mentioned here. Even the inclusion of the LASTE modification after the Desert Storm conflict did not included the FLIR designator. It is a tribute to the men of these squadrons that they fought as well as they did, using ingenuity and the trust they had in their abilities and aircraft to have performed so well.
An interesting sidenote about LASTE is the number of lives lost associated with its late implementation; the Air Force lost an average of 2.5 hog drivers each year to controlled flight into the ground. In other words, pilots who were task saturated, distracted—or just plain unlucky—flew perfectly good jets into the ground an average of 2.5 times each year before LASTE. Only one Hog driver survived such a mishap. Only one Hog driver has died this way in a LASTE jet.
