Il Fairchild-Republic A-10 Thunderbolt II è un aereo da attacco al suolo monoposto statunitense, bimotore e ad ala rettilinea. Sviluppato dalla Fairchild-Republic attorno al cannone GAU-8 Avenger nei primi anni settanta, l'A-10 è in dotazione all'USAF che sfrutta la sua pesante blindatura per colpire obiettivi terrestri di vario tipo.
Nel gergo dei piloti è chiamato Warthog (facocero).
Storia del progetto
L'idea di sviluppare un aereo dedicato specificatamente al supporto aereo ravvicinato venne nel 1966 all'allora capo di stato maggiore dell'USAF John P. McConnell, che intendeva riunire le qualità dimostrate nella guerra del Vietnam (in corso) dell'A-1 Skyraider con quelle dell'A-7 Corsair II. L'aereo che ne risultasse avrebbe dovuto quindi possedere lunga autonomia, maneggevolezza a basse quote, vasta gamma di armamenti e buona velocità, ma avrebbe dovuto essere più resistente ai colpi della contraerea.
Nel 1967 venne dunque varato dall'USAF il programma A-X a cui si interessarono numerose ditte costruttrici, ma nel 1970, dopo le varie selezioni, ne rimasero solo due: la Northrop Grumman Corporation con il suo progetto "A-9", e la Fairchild Aircraft che propose la versione "A-10". Tutte e due le idee prevedevano ali lunghe e dritte e numerosi piloni subalari per l'aggancio delle armi, ma la Fairchild propose il montaggio dei motori (due turboventole) su gondole installate sopra la fusoliera dietro le ali, e due timoni verticali posti alle estremità degli impennaggi orizzontali. L'aereo della Grumman invece aveva una configurazione più classica, con i motori montati in gondole ai lati della fusoliera sotto le ali, e con un unico timone verticale. Ad entrambe le ditte fu commissionata la costruzione di un prototipo per dei test sul campo e verificare quindi quale dei due modelli fosse migliore. Dall'ottobre al dicembre 1972 l'USAF valutò, dietro voli di prova, le due versioni, dimostrando un maggiore interesse per l'A-10, che sembrava più robusto e meglio protetto dai colpi da terra per via del suo disegno.
I costi inferiori dell'A-10 rispetto all'A-9, fecero sì che nel 1973 l'USAF finanziò la costruzione di un primo lotto di dieci di questi velivoli e lo stesso anno fece sapere che avrebbe scelto come armamento primario il GAU-8 Avenger da 30 mm della General Electric. Le buone prove dimostrate dall'accoppiamento dell'A-10 con il GAU-8 portarono alla consegna dei primi aerei nel dicembre 1975 (arrivati alla Davis-Monthan Air Force Base), che diventarono operativi nel 1977.
Dal 1975, data di inizio della produzione, al 1984, data di fine, sono stati costruiti in totale 715 A-10, cifra comprensiva di due prototipi monoposto e un prototipo biposto (quest'ultimo scartato dopo voli di prova non soddisfacenti). Dal 1987 gli aggiornamenti del velivolo sono curati dalla Northrop Grumman Corporation.
I programmi di aggiornamento
Data l'età del Thunderbolt II, l'USAF ritenne di doverlo aggiornare per metterlo al passo coi tempi. Negli anni novanta iniziò il programma A-10/PEP, Precision Engagement Program, per trasformare gli A-10 nella nuova versione A-10C, con il primo esemplare tornato operativo nel settembre 2007.
La modernizzazione dovrebbe interessare 356 velivoli. Le novità prevedono un nuovo abitacolo con strumentazione digitale, un sistema di navigazione GPS, un sistema integrato di controllo per il volo e il tiro, la compatibilità con pod FLIR e illuminazione laser per l'utilizzo di bombe LGB senza necessità di una fonte di illuminazione esterna, la predisposizione per il casco HMS, sistema di visione notturna NVG, la capacità di utilizzare bombe a guida GPS come le JDAM e le WCMD (a grappolo), un sistema di comunicazione avanzato. Gran parte di questi congegni elettronici è stata commissionata alla Lockheed Martin Systems Integration – Owego.
La struttura e i motori non sono stati trascurati, essendo stati oggetto di rinnovamenti che garantiranno una vita operativa al Thunderbolt fino al 2028.
Il 31 ottobre 2016 il Pentagono ha comunicato di aver deciso di estendere l'utilizzo dell'intera flotta di 283 esemplari non più fino al 2028, ma addirittura fino al 2040/2045, questo finché l'aereo che uscirà vincitore dal programma A-X non dimostrerà appieno le proprie capacità nel CAS/COIN.
Tra il 2011 e l'agosto 2019, 173 esemplari sono stati sottoposti all'aggiornamento A-10 Enhanced Wing Assembly per la sostituzione delle ali con delle nuove che dovrebbero avere una durata equivalente a 10.000 ore di volo. Questo aggiornamento strutturale consentirà all’aeromobile di continuare a volare fino alla fine degli anni 2030. Ad agosto 2019 Boeing ha ottenuto un nuovo contratto per la continuazione del programma volto a sostituire le ali dei restanti 109 aerei non ancora modificati.
Tecnica
L'A-10 Thunderbolt II (il primo "Thunderbolt" fu il Republic P-47) possiede buona precisione e manovrabilità sia a basse quote (sotto i 300 metri) che a basse velocità. La capacità di atterrare e decollare su piste corte o semi-preparate gli permette inoltre di agire vicino alla prima linea, se necessario anche di notte grazie al dispositivo Night Vision Imaging System (NVIS). La spessa corazza di cui è completamente rivestito gli permette di sopportare proiettili con calibro superiore a 23 mm, inoltre i serbatoi di carburante sono ricoperti di schiuma antincendio. Se anche tutti e sei i serbatoi venissero perforati entrerebbe in funzione un sistema di alimentazione d'emergenza, in grado di erogare carburante per 370 km di autonomia.
La cabina di pilotaggio monoposto, sormontata da un esteso cupolino a goccia, è completamente blindata in titanio per garantire la salvezza del pilota da proiettili con calibro fino a 23 mm. È presente un Head-up display, usato per individuare i bersagli e scegliere il tipo di munizionamento da lanciare e un sistema di navigazione inerziale affiancato da un sistema di navigazione TACAN. Il sistema di comunicazione è di tipo multi-band.
Altri elementi dell'avionica includono GPS, contromisure elettroniche valide sia per attacchi aerei che terrestri, sistema di puntamento laser Pave Penny, computer specifici per l'attacco a basse quote che calcolano continuamente le coordinate migliori per colpire i bersagli, pilota automatico specifico per le basse quote e sistema anti-collisione con il suolo.
Il Thunderbolt II monta due motori General Electric TF34-GE-100, ognuno capace di 4.111 kg di spinta. Il volo è possibile anche con un motore fuori uso, senza mezza coda, due terzi di un'ala (capace di sopportare, insieme all'altra ala, carichi fino a 7,3 g positivi) e vari elementi della fusoliera. All'occorrenza il motore può essere alimentato per un breve periodo da benzina, in mancanza del cherosene.
L'impianto idraulico è stato costruito con doppi circuiti, e in caso entrasse completamente in avaria è disponibile un sistema di controllo meccanico del volo.
Armamento
L'aereo dispone di 11 piloni subalari per l'attacco di armi, trasportabili fino ad un massimo di 7.260 kg.
L'A-10 può trasportare il missile aria-superficie AGM-65 Maverick, capace di colpire obiettivi distanti più di 45 km. Altri missili caricabili nei piloni sono gli AIM-9 Sidewinder (aria-aria). Quanto alle bombe, possono essere usate le Mk 82 da 226 kg o le bombe a grappolo BLU-1, BLU-27/B Rockeye II o CBU-52/71.
Il pod LITENING ER della Northrop Grumman, essenziale per l'acquisizione dei bersagli, proietta le immagini in un visore termico CCD di 640×512 pixel.
Il cannone, installato nella parte inferiore del naso all'apice della fusoliera, è un GAU-8/A Avenger a 7 canne rotanti ad azionamento elettro-idraulico, calibro 30 mm e camerato per il munizionamento 30 × 173 mm, in grado di distruggere un carro armato da una distanza di 6,5 km con proiettili da 0,75 kg o 0,43 kg (la scorta consiste in 1.350 unità). La cadenza di tiro è selezionabile secondo le necessità: 2.100 o 4.200 colpi al minuto.
Il GAU-8 Avenger è un cannone Gatling statunitense con elevata potenza di fuoco, ma anche di rilevante peso ed ingombro, impiegato sull'A-10 Thunderbolt e nel sistema di difesa navale di punto Goalkeeper.
Possiede 7 canne rotanti, con due motori esterni che azionano l'arma a 2100 o 4200 colpi al minuto. Il serbatoio munizioni contiene 1350 colpi ed è corazzato; altre munizioni, per un totale di 1350, sono alloggiabili nel nastro di alimentazione. Peso totale dell'installazione: 1830 kg. È lungo circa 6 m, ciò nonostante sporge solo in minima parte dall'aereo; spara proiettili esplosivi la cui potenza è nettamente superiore a quelli del Vulcan, e nel caso dei proiettili perforanti, l'efficacia contro carri è migliore.
Impiego operativo
L'inizio della carriera operativa del Thunderbolt II non fu promettente. La fine della guerra fredda e la caduta dell'Unione Sovietica indussero l'USAF a lasciarne a terra un numero sempre crescente, pensando addirittura di escluderlo dalle linee in favore di una versione dell'F-16 appositamente pensata per l'attacco al suolo. Ad opporsi fu però l'United States Army, l'esercito statunitense, anche perché l'F-16 non si dimostrò un buon vettore per il cannone Avenger. Per venire incontro sia alle richieste di radiazione del Congresso che a quelle dell'esercito, l'USAF optò per accantonare circa la metà degli A-10 e trasformare la restante metà in un aereo da ricognizione avanzata (versione denominata OA-10A, senza, però, nessuna differenza dall'A-10A).
Quando l'Iraq invase il Kuwait, facendo da miccia alla guerra del Golfo, il Thunderbolt ritornò in auge con 140 esemplari che distrussero circa 1.000 carri armati, 2.000 mezzi militari di vario genere e un migliaio di pezzi di artiglieria in 8.624 missioni totali. Questi numeri spinsero l'USAF a mantenere in servizio i Thunderbolt II, anche se si rese necessario un loro aggiornamento.
Mentre era in corso il processo di modernizzazione, il Thunderbolt II ha avuto modo di volare nelle operazioni Provide Comfort, Southern Watch, Desert Fox, Noble Anvil, Deny Flight, Allied Force, Enduring Freedom e Iraqi Freedom. Più recentemente, ha colpito elementi pro-Gheddafi nell'ambito dell'operazione Odyssey Dawn.
Ad oggi è stato ampiamente usato nella Guerra in Afghanistan (2001 - in corso) e nella Guerra d'Iraq, e dalle forze Nato in Medio Oriente è stato definito "l'incubo dei talebani", dato che i proiettili supersonici del GAU-8 arrivano a destinazione prima di poter essere uditi.
L'aereo, nonostante alcune proposte, non è mai stato esportato.
Versioni
Dell'A-10 sono stati prodotti 751 esemplari distribuiti tra U.S. Air Force, Air National Guard e Air Force Reserve:
- YA-10: 2 prototipi (c/n 71-1369 e 71-1370).
- YA-10A: 6 esemplari di pre-serie (da c/n 73-1664 a c/n 73-1669) solo modifiche di dettaglio rispetto ai prototipi.
- A-10A: versione di serie il cui primo esemplare fu il c/n 75-0258.
- OA-10A: versione virtuale, l'USAF usava questa sigla quando impiegava l'A-10 in missioni FAC (Forward Air Controller, ricerca e acquisizione bersagli). Designazione cancellata nel 2003.
- YA-10B: versione biposto richiesta dall'USAF, detta anche A-10 N/AW (notte e cattivo tempo), nell'aprile 1978. Fu costruito un prototipo modificando l'apparecchio c/n 73-1664 che volò il 4 maggio 1979, dotato di un sistema di navigazione e attacco simile all'attuale LANTIRN, piattaforma inerziale LN-39 e radar altimetro AN/APN-194. L'USAF non diede seguito alla richiesta.
- A-10B: versione biposto d'addestramento e attacco ipotizzata nel 1980 da costruire in circa 300 esemplari. Non venne mai realizzata.
- A-10BMS: versione d'attacco marittimo proposta a vari paesi asiatici. L'armamento era composto da missili AGM-84 Harpoon o Exocet, ma non fu mai prodotto.
- A-10AMX: versione proposta all'Italia nel 1978 per il programma AMX, da cui uscì l'omonimo velivolo italo-brasiliano. Era un A-10 rimotorizzato con due Turbo-Union RB.199-36 senza postbruciatore da 4.508 kg/s di spinta. Velocità max 830 km/h.
- A-10C: questa designazione venne adottata il 12 aprile 2004 per differenziare gli A-10 aggiornati con calcolatore digitale per la gestione degli armamenti e pod per l'acquisizione dei bersagli e munizionamento di precisione.
- OA-10C: Il 12 aprile 2004 l'USAF decise di reintrodurre il prefisso O sugli A-10 che effettuano missioni FAC (Forward Air Controller).
Utilizzatori:
- Stati Uniti - United States Air Force - 715 esemplari ordinati, 281 in servizio al settembre 2019.
Cultura di massa
L'aereo statunitense appare in alcuni videogiochi di simulazione di volo dedicati, come A-10 Tank Killer (prodotto da Dynamix nel 1991) e il sequel Silent Thunder: A-10 Tank Killer II (Sierra Entertainment, 1996), A-10 Cuba! o il più recente (2011) DCS: A-10C Warthog (della serie Digital Combat Simulator della russa Eagle Dynamics) e in altri videogiochi di simulazione più generici (l'aereo è uno dei tanti pilotabili) come Lock On: Modern Air Combat, Ace Combat: Distant Thunder (in versione A-10A Thunderbolt II), Ace Combat: Squadron Leader (in versione A-10A Thunderbolt II), Ace Combat: The Belkan War (in versione A-10A Thunderbolt II), Tom Clancy's H.A.W.X., Battlefield: Bad Company 2, Battlefield 3, Battlefield 4, Red Crucible Firestorm, Call of Duty: Modern Warfare 3, MetalStorm: Wingman e Command & Conquer: Generals - Zero Hour.
Il Thunderbolt II ha ispirato anche dei giocattoli, come alcuni Transformers della Hasbro e altri robot giocattolo dello stesso tipo. Nella linea Transformers G1, c'era il personaggio di Powerglide, poi riutilizzato in altre linee (Classics, Combiner Wars, Generations e così via) con dimensioni. In particolare, si trasformavano in A-10 due robot della serie Gobots che fu prodotta dalla statunitense Tonka, tra il 1983 e il 1987, in diretta concorrenza ai Transformers. Nel 2008, la rinnovata popolarità dell'aereo a seguito del film Transformers (2007) condusse, inoltre, la Hasbro a mettere in vendita un robot (Wingblade) che si trasformava in A-10. L'A-10 compare anche in Aero Fighters 2, arcade a scorrimento verticale, e in Saints Row 2, Saints Row: The Third e Saints Row IV (con il nome fittizio "AB Destroyer").
Tre aerei A-10 compaiono in alcune scene del film L'uomo d'acciaio.
Nel film Terminator Salvation, quarto capitolo dedicato alla saga di Terminator, la Resistenza umana impiega alcuni A-10 contro le macchine volanti di Skynet.
Nel film Transformers, 2 Thunderbolt assistono una squadra di militari contro l'attacco del decepticon Scorponok.
Nel cartone animato Gi.Joe,e nella serie di giocattoli,gli aerei usati dai "cattivi",i Cobra,sono ispirati al Thunderbolt.
Nel film Leoni per agnelli, un A-10 viene inviato in soccorso di due soldati U.S.A. rimasti isolati e attaccati da alcuni Talebani.
ENGLISH
The Fairchild Republic A-10 Thunderbolt II is a single-seat, twin turbofan engine, straight wing jet aircraft developed by Fairchild-Republic for the United States Air Force (USAF). It is commonly referred to by the nicknames "Warthog" or "Hog", although the A-10's official name comes from the Republic P-47 Thunderbolt, a World War II fighter-bomber effective at attacking ground targets. The A-10 was designed for close air support (CAS) of friendly ground troops, attacking armored vehicles and tanks, and providing quick-action support against enemy ground forces. It entered service in 1976 and is the only production-built aircraft that has served in the USAF that was designed solely for CAS. Its secondary mission is to provide forward air controller-airborne support, by directing other aircraft in attacks on ground targets. Aircraft used primarily in this role are designated OA-10.
The A-10 was intended to improve on the performance of the A-1 Skyraider and its lesser firepower. The A-10 was designed around the 30 mm GAU-8 Avenger rotary cannon. Its airframe was designed for durability, with measures such as 1,200 pounds (540 kg) of titanium armor to protect the cockpit and aircraft systems, enabling it to absorb a significant amount of damage and continue flying. Its short takeoff and landing capability permits operation from airstrips close to the front lines, and its simple design enables maintenance with minimal facilities. The A-10 served in the Gulf War (Operation Desert Storm), the American led intervention against Iraq's invasion of Kuwait, where the A-10 distinguished itself. The A-10 also participated in other conflicts such as in Grenada, the Balkans, Afghanistan, Iraq, and against Islamic State in the Middle East.
The A-10A single-seat variant was the only version produced, though one pre-production airframe was modified into the YA-10B twin-seat prototype to test an all-weather night capable version. In 2005, a program was started to upgrade remaining A-10A aircraft to the A-10C configuration, with modern avionics for use with precision weaponry. The U.S. Air Force had stated the F-35 would replace the A-10 as it entered service, but this remains highly contentious within the USAF and in political circles. With a variety of upgrades and wing replacements, the A-10's service life can be extended to 2040; the service has no planned retirement date as of June 2017.
Development
Background
Post-World War II development of conventionally armed attack aircraft in the United States had stagnated. Design efforts for tactical aircraft focused on the delivery of nuclear weapons using high-speed designs like the F-101 Voodoo and F-105 Thunderchief. Designs concentrating on conventional weapons had been largely ignored, leaving their entry into the Vietnam War led by the Korean War-era Douglas A-1 Skyraider. While a capable aircraft for its era, with a relatively large payload and long loiter time, the propeller-driven design was also relatively slow and vulnerable to ground fire. The U.S. Air Force and Marine Corps lost 266 A-1s in action in Vietnam, largely from small arms fire. The A-1 Skyraider also had poor firepower.
The lack of modern conventional attack capability prompted calls for a specialized attack aircraft. On 7 June 1961, Secretary of Defense McNamara ordered the USAF to develop two tactical aircraft, one for the long-range strike and interdictor role, and the other focusing on the fighter-bomber mission. The former became the Tactical Fighter Experimental, or TFX, which emerged as the F-111, while the second was filled by a version of the U.S. Navy's F-4 Phantom II. While the Phantom went on to be one of the most successful fighter designs of the 1960s, and proved to be a capable fighter-bomber, its lack of loiter time was a major problem, and to a lesser extent, its poor low-speed performance. It was also expensive to buy and operate, with a flyaway cost of $2 million in FY1965 ($16.2 million today), and operational costs over $900 per hour ($7,000 per hour today).
After a broad review of its tactical force structure, the U.S. Air Force decided to adopt a low-cost aircraft to supplement the F-4 and F-111. It first focused on the Northrop F-5, which had air-to-air capability. A 1965 cost-effectiveness study shifted the focus from the F-5 to the less expensive LTV A-7D, and a contract was awarded. However, this aircraft doubled in cost with demands for an upgraded engine and new avionics.
Helicopter competition
During this period, the United States Army had been introducing the UH-1 Iroquois into service. First used in its intended role as a transport, it was soon modified in the field to carry more machine guns in what became known as the helicopter gunship role. This proved effective against the lightly armed enemy, and new gun and rocket pods were added. Soon the AH-1 Cobra was introduced. This was an attack helicopter armed with long-range BGM-71 TOW missiles able to destroy tanks from outside the range of defensive fire. The helicopter was effective, and prompted the U.S. military to change its defensive strategy in Europe by blunting any Warsaw Pact advance with anti-tank helicopters instead of the tactical nuclear weapons that had been the basis for NATO's battle plans since the 1950s.
The Cobra was a quickly made helicopter based on the UH-1 Iroquois, though, and in the late 1960s the U.S. Army was designing the Lockheed AH-56 Cheyenne, a much more capable attack aircraft with greater speed. These developments worried the USAF, which saw the anti-tank helicopter overtaking its nuclear-armed tactical aircraft as the primary anti-armor force in Europe. A 1966 Air Force study of existing close air support (CAS) capabilities revealed gaps in the escort and fire suppression roles, which the Cheyenne could fill. The study concluded that the service should acquire a simple, inexpensive, dedicated CAS aircraft at least as capable as the A-1, and that it should develop doctrine, tactics, and procedures for such aircraft to accomplish the missions for which the attack helicopters were provided.
A-X program
On 8 September 1966, General John P. McConnell, Chief of Staff of the USAF, ordered that a specialized CAS aircraft be designed, developed, and obtained. On 22 December, a Requirements Action Directive was issued for the A-X CAS airplane, and the Attack Experimental (A-X) program office was formed. On 6 March 1967, the Air Force released a request for information to 21 defense contractors for the A-X. The objective was to create a design study for a low-cost attack aircraft. In 1969, the Secretary of the Air Force asked Pierre Sprey to write the detailed specifications for the proposed A-X project; Sprey's initial involvement was kept secret due to his earlier controversial involvement in the F-X project. Sprey's discussions with Skyraider pilots operating in Vietnam and analysis of aircraft used in the role indicated the ideal aircraft should have long loiter time, low-speed maneuverability, massive cannon firepower, and extreme survivability; possessing the best elements of the Ilyushin Il-2, Henschel Hs 129, and Skyraider. The specifications also demanded that each aircraft cost less than $3 million (equivalent to $20.9 million today). Sprey required that the biography of World War II Luftwaffe attack pilot Hans-Ulrich Rudel be read by people on the A-X program.
In May 1970, the USAF issued a modified, more detailed request for proposals for the aircraft. The threat of Soviet armored forces and all-weather attack operations had become more serious. The requirements now included that the aircraft would be designed specifically for the 30 mm rotary cannon. The RFP also specified a maximum speed of 460 mph (400 kn; 740 km/h), takeoff distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg), 285-mile (460 km) mission radius, and a unit cost of US$1.4 million ($9.2 million today). The A-X would be the first USAF aircraft designed exclusively for close air support. During this time, a separate RFP was released for A-X's 30 mm cannon with requirements for a high rate of fire (4,000 round per minute) and a high muzzle velocity. Six companies submitted aircraft proposals, with Northrop and Fairchild Republic selected to build prototypes: the YA-9A and YA-10A, respectively. General Electric and Philco-Ford were selected to build and test GAU-8 cannon prototypes.
Two YA-10 prototypes were built in the Republic factory in Farmingdale, New York, and first flown on 10 May 1972 by pilot Howard "Sam" Nelson. Production A-10s were built by Fairchild in Hagerstown, Maryland. After trials and a fly-off against the YA-9, on 18 January 1973, the USAF announced the YA-10's selection for production. General Electric was selected to build the GAU-8 cannon in June 1973. The YA-10 had an additional fly-off in 1974 against the Ling-Temco-Vought A-7D Corsair II, the principal USAF attack aircraft at the time, to prove the need for a new attack aircraft. The first production A-10 flew in October 1975, and deliveries commenced in March 1976.
One experimental two-seat A-10 Night Adverse Weather (N/AW) version was built by converting an A-10A. The N/AW was developed by Fairchild from the first Demonstration Testing and Evaluation (DT&E) A-10 for consideration by the USAF. It included a second seat for a weapons system officer responsible for electronic countermeasures (ECM), navigation and target acquisition. The N/AW version did not interest the USAF or export customers. The two-seat trainer version was ordered by the Air Force in 1981, but funding was canceled by U.S. Congress and the jet was not produced. The only two-seat A-10 built now resides at Edwards Air Force Base's Flight Test Center Museum.
Production
On 10 February 1976, Deputy Secretary of Defense Bill Clements authorized full-rate production, with the first A-10 being accepted by the Air Force Tactical Air Command on 30 March 1976. Production continued and reached a peak rate of 13 aircraft per month. By 1984, 715 airplanes, including two prototypes and six development aircraft, had been delivered.
When A-10 full-rate production was first authorized the aircraft's planned service life was 6,000 hours. A small reinforcement to the design was quickly adopted when the A-10 failed initial fatigue testing at 80% of testing; with the fix, the A-10 passed the fatigue tests. 8,000-flight-hour service lives were becoming common at the time, so fatigue testing of the A-10 continued with a new 8,000-hour target. This new target quickly discovered serious cracks at Wing Station 23 (WS23) where the outboard portions of the wings are joined to the fuselage. The first production change was to add cold working at WS23 to address this problem. Soon after, the Air Force determined that the real-world A-10 fleet fatigue was more harsh than estimated, forcing them to change their fatigue testing and introduce "spectrum 3" equivalent flight-hour testing.
Spectrum 3 fatigue testing started in 1979. This round of testing quickly determined that more drastic reinforcement would be needed. The second change in production, starting with aircraft #442, was to increase the thickness of the lower skin on the outer wing panels. A tech order was issued to retrofit the "thick skin" to the whole fleet, but the tech order was rescinded after roughly 242 planes, leaving about 200 planes with the original "thin skin". Starting with aircraft #530, cold working at WS0 was performed, and this retrofit was performed on earlier aircraft. A fourth, even more drastic change was initiated with aircraft #582, again to address the problems discovered with spectrum 3 testing. This change increased the thickness on the lower skin on the center wing panel, but it required modifications to the lower spar caps to accommodate the thicker skin. The Air Force determined that it was not economically feasible to retrofit earlier planes with this modification.
Upgrades
The A-10 has received many upgrades since entering service. In 1978, the A-10 received the Pave Penny laser receiver pod, which receives reflected laser radiation from laser designators to allow the aircraft to deliver laser guided munitions. The Pave Penny pod is carried on a pylon mounted below the right side of the cockpit and has a clear view of the ground. In 1980, the A-10 began receiving an inertial navigation system.
In the early 1990s, the A-10 began to receive the Low-Altitude Safety and Targeting Enhancement (LASTE) upgrade, which provided computerized weapon-aiming equipment, an autopilot, and a ground-collision warning system. In 1999, aircraft began receiving Global Positioning System navigation systems and a multi-function display. The LASTE system was upgraded with an Integrated Flight & Fire Control Computer (IFFCC).
Proposed further upgrades included integrated combat search and rescue locator systems and improved early warning and anti-jam self-protection systems, and the Air Force recognized that the A-10's engine power was sub-optimal and had been planning to replace them with more powerful engines since at least 2001 at an estimated cost of $2 billion.
HOG UP and Wing Replacement Program
In 1987, Grumman Aerospace took over support for the A-10 program. In 1993, Grumman updated the damage tolerance assessment and Force Structural Maintenance Plan and Damage Threat Assessment. Over the next few years, problems with wing structure fatigue, first noticed in production years earlier, began to come to the fore. The process of implementing the maintenance plan was greatly delayed by the base realignment and closure commission (BRAC), which led to 80% of the original workforce being let go.
During inspections in 1995 and 1996, cracks at the WS23 location were found on many aircraft, most of them in line with updated predictions from 1993. However, two of these were classified as "near-critical" size, well beyond predictions. In August 1998, Grumman produced a new plan to address these issues and increase life span to 16,000 hours. This resulted in the "HOG UP" program, which commenced in 1999. Over time, additional aspects were added to HOG UP, including new fuel bladders, changes to the flight control system, and inspections of the engine nacelles. In 2001, the cracks were reclassified as "critical", which meant they were considered repairs and not upgrades, which allowed bypassing normal acquisition channels for more rapid implementation.
An independent review of the HOG UP program at this point concluded that the data on which the wing upgrade relied could no longer be trusted. This independent review was presented in September 2003. Shortly thereafter, fatigue testing on a test wing failed prematurely and also mounting problems with wings failing in-service inspections at an increasing rate became apparent. The Air Force estimated that they would run out of wings by 2011. Of the plans explored, replacing the wings with new ones was the least expensive, with an initial cost of $741 million, and a total cost of $1.72 billion over the life of the program.
In 2005, a business case was developed with three options to extend the life of the fleet. The first two options involved expanding the service life extension program (SLEP) at a cost of $4.6 billion and $3.16 billion, respectively. The third option, worth $1.72 billion, was to build 242 new wings and avoid the cost of expanding the SLEP. In 2006, option 3 was chosen and Boeing won the contract. The base contract is for 117 wings with options for 125 additional wings. In 2013, the Air Force exercised a portion of the option to add 56 wings, putting 173 wings on order with options remaining for 69 additional wings. In November 2011, two A-10s flew with the new wings fitted. The new wings improved mission readiness, decreased maintenance costs, and allowed the A-10 to be operated up to 2035 if necessary. The re-winging effort was organized under the Thick-skin Urgent Spares Kitting (TUSK) Program.
In 2014, as part of plans to retire the A-10, the USAF considered halting the wing replacement program to save an additional $500 million; however, by May 2015 the re-winging program was too far into the contract to be financially efficient to cancel. Boeing stated in February 2016 that the A-10 fleet with the new TUSK wings could operate to 2040.
A-10C
In 2005, the entire fleet of 356 A-10 and OA-10 aircraft began receiving the Precision Engagement upgrades including an improved fire control system (FCS), electronic countermeasures (ECM), and smart bomb targeting. The aircraft receiving this upgrade were redesignated A-10C. The Government Accounting Office in 2007 estimated the cost of upgrading, refurbishing, and service life extension plans for the A-10 force to total $2.25 billion through 2013. In July 2010, the USAF issued Raytheon a contract to integrate a Helmet Mounted Integrated Targeting (HMIT) system into the A-10C. The Air Force Material Command's Ogden Air Logistics Center at Hill AFB, Utah completed work on its 100th A-10 precision engagement upgrade in January 2008. The final aircraft was upgraded to A-10C configuration in June 2011. The aircraft also received all-weather combat capability, and a Hand-on-Throttle-and-Stick configuration mixing the F-16's flight stick with the F-15's throttle. Other changes included two multifunction displays, a modern communications suite including a Link-16 radio and SATCOM. The LASTE system was replaced with the integrated flight and fire control computer (IFFCC) included in the PE upgrade.
Throughout its life, the platform's software has been upgraded several times, and although these upgrades were due to be stopped as part of plans to retire the A-10 in February 2014, Secretary of the Air Force Deborah Lee James ordered that the latest upgrade, designated Suite 8, continue in response to Congressional pressure. Suite 8 software includes IFF Mode 5, which modernizes the ability to identify the A-10 to friendly units. Additionally, the Pave Penny pods and pylons are being removed as their receive-only capability has been replaced by the AN/AAQ-28(V)4 LITENING AT targeting pods or Sniper XR targeting pod, which both have laser designators and laser rangefinders.
In 2012, Air Combat Command requested the testing of a 600-US-gallon (2,300 l; 500 imp gal) external fuel tank which would extend the A-10's loitering time by 45–60 minutes; flight testing of such a tank had been conducted in 1997, but did not involve combat evaluation. Over 30 flight tests were conducted by the 40th Flight Test Squadron to gather data on the aircraft's handling characteristics and performance across different load configurations. It was reported that the tank slightly reduced stability in the yaw axis, but there was no decrease in aircraft tracking performance.
Design
Overview
The A-10 has a cantilever low-wing monoplane wing with a wide chord. The aircraft has superior maneuverability at low speeds and altitude because of its large wing area, high wing aspect ratio, and large ailerons. The wing also allows short takeoffs and landings, permitting operations from primitive forward airfields near front lines. The aircraft can loiter for extended periods and operate under 1,000-foot (300 m) ceilings with 1.5-mile (2.4 km) visibility. It typically flies at a relatively low speed of 300 knots (350 mph; 560 km/h), which makes it a better platform for the ground-attack role than fast fighter-bombers, which often have difficulty targeting small, slow-moving targets.
The leading edge of the wing has a honeycomb structure panel construction, providing strength with minimal weight; similar panels cover the flap shrouds, elevators, rudders and sections of the fins. The skin panels are integral with the stringers and are fabricated using computer-controlled machining, reducing production time and cost. Combat experience has shown that this type of panel is more resistant to damage. The skin is not load-bearing, so damaged skin sections can be easily replaced in the field, with makeshift materials if necessary. The ailerons are at the far ends of the wings for greater rolling moment and have two distinguishing features: The ailerons are larger than is typical, almost 50 percent of the wingspan, providing improved control even at slow speeds; the aileron is also split, making it a deceleron.
The A-10 is designed to be refueled, rearmed, and serviced with minimal equipment. Its simple design enables maintenance at forward bases with limited facilities. An unusual feature is that many of the aircraft's parts are interchangeable between the left and right sides, including the engines, main landing gear, and vertical stabilizers. The sturdy landing gear, low-pressure tires and large, straight wings allow operation from short rough strips even with a heavy aircraft ordnance load, allowing the aircraft to operate from damaged airbases, flying from taxiways, or even straight roadway sections.
The front landing gear is offset to the aircraft's right to allow placement of the 30 mm cannon with its firing barrel along the centerline of the aircraft. During ground taxi, the offset front landing gear causes the A-10 to have dissimilar turning radii. Turning to the right on the ground takes less distance than turning left. The wheels of the main landing gear partially protrude from their nacelles when retracted, making gear-up belly landings easier to control and less damaging. All landing gears retract forward; if hydraulic power is lost, a combination of gravity and aerodynamic drag can lower and lock the gear in place.
Durability
The A-10 is exceptionally tough, being able to survive direct hits from armor-piercing and high-explosive projectiles up to 23 mm. It has double-redundant hydraulic flight systems, and a mechanical system as a back up if hydraulics are lost. Flight without hydraulic power uses the manual reversion control system; pitch and yaw control engages automatically, roll control is pilot-selected. In manual reversion mode, the A-10 is sufficiently controllable under favorable conditions to return to base, though control forces are greater than normal. The aircraft is designed to be able to fly with one engine, half of the tail, one elevator, and half of a wing missing.
The cockpit and parts of the flight-control systems are protected by 1,200 lb (540 kg) of titanium aircraft armor, referred to as a "bathtub". The armor has been tested to withstand strikes from 23 mm cannon fire and some strikes from 57 mm rounds. It is made up of titanium plates with thicknesses varying from 0.5 to 1.5 inches (13 to 38 mm) determined by a study of likely trajectories and deflection angles. The armor makes up almost six percent of the aircraft's empty weight. Any interior surface of the tub directly exposed to the pilot is covered by a multi-layer nylon spall shield to protect against shell fragmentation. The front windscreen and canopy are resistant to small arms fire.
The A-10's durability was demonstrated on 7 April 2003 when Captain Kim Campbell, while flying over Baghdad during the 2003 invasion of Iraq, suffered extensive flak damage. Iraqi fire damaged one of her engines and crippled the hydraulic system, requiring the aircraft's stabilizer and flight controls to be operated via the 'manual reversion mode.' Despite this damage, Campbell flew the aircraft for nearly an hour and landed safely.
The A-10 was intended to fly from forward air bases and semi-prepared runways with high risk of foreign object damage to the engines. The unusual location of the General Electric TF34-GE-100 turbofan engines decreases ingestion risk, and allows the engines to run while the aircraft is serviced and rearmed by ground crews, reducing turn-around time. The wings are also mounted closer to the ground, simplifying servicing and rearming operations. The heavy engines require strong supports: four bolts connect the engine pylons to the airframe. The engines' high 6:1 bypass ratio contributes to a relatively small infrared signature, and their position directs exhaust over the tailplanes further shielding it from detection by infrared homing surface-to-air missiles. The engines' exhaust nozzles are angled nine degrees below horizontal to cancel out the nose-down pitching moment that would otherwise be generated from being mounted above the aircraft's center of gravity and avoid the need to trim the control surfaces to prevent pitching.
To reduce the likelihood of damage to the A-10's fuel system, all four fuel tanks are located near the aircraft's center and are separated from the fuselage; projectiles would need to penetrate the aircraft's skin before reaching a tank's outer skin. Compromised fuel transfer lines self-seal; if damage exceeds a tank's self-sealing capabilities, check valves prevent fuel flowing into a compromised tank. Most fuel system components are inside the tanks so that fuel will not be lost due to component failure. The refueling system is also purged after use. Reticulated polyurethane foam lines both the inner and outer sides of the fuel tanks, retaining debris and restricting fuel spillage in the event of damage. The engines are shielded from the rest of the airframe by firewalls and fire extinguishing equipment. In the event of all four main tanks being lost, two self-sealing sump tanks contain fuel for 230 miles (370 km) of flight.
Since the A-10 operates extremely close to enemy positions, where it is an easy target for MANPADS, surface-to-air missiles (SAMs), and enemy fighters, it can carry up to 480 flares and 480 chaff cartridges, which is more than any other fighter, but usually flies with a mix of both.
Weapons
Although the A-10 can carry a considerable amount of munitions, its primary built-in weapon is the 30×173 mm GAU-8/A Avenger autocannon. One of the most powerful aircraft cannons ever flown, it fires large depleted uranium armor-piercing shells. The GAU-8 is a hydraulically driven seven-barrel rotary cannon designed specifically for the anti-tank role with a high rate of fire. The cannon's original design could be switched by the pilot to 2,100 or 4,200 rounds per minute; this was later changed to a fixed rate of 3,900 rounds per minute. The cannon takes about half a second to reach top speed, so 50 rounds are fired during the first second, 65 or 70 rounds per second thereafter. The gun is accurate enough to place 80 percent of its shots within a 40-foot (12.4 m) diameter circle from 4,000 feet (1,220 m) while in flight. The GAU-8 is optimized for a slant range of 4,000 feet (1,220 m) with the A-10 in a 30-degree dive.
The fuselage of the aircraft is built around the cannon. The GAU-8/A is mounted slightly to the port side; the barrel in the firing location is on the starboard side at the 9 o'clock position so it is aligned with the aircraft's centerline. The gun's 5-foot, 11.5-inch (1.816 m) ammunition drum can hold up to 1,350 rounds of 30 mm ammunition, but generally holds 1,174 rounds. To protect the GAU-8/A rounds from enemy fire, armor plates of differing thicknesses between the aircraft skin and the drum are designed to detonate incoming shells.
The AGM-65 Maverick air-to-surface missile is a commonly used munition for the A-10, targeted via electro-optical (TV-guided) or infrared. The Maverick allows target engagement at much greater ranges than the cannon, and thus less risk from anti-aircraft systems. During Desert Storm, in the absence of dedicated forward-looking infrared (FLIR) cameras for night vision, the Maverick's infrared camera was used for night missions as a "poor man's FLIR". Other weapons include cluster bombs and Hydra rocket pods. The A-10 is equipped to carry GPS and laser-guided bombs, such as the GBU-39 Small Diameter Bomb, Paveway series bombs, JDAM, WCMD and glide bomb AGM-154 Joint Standoff Weapon. A-10s usually fly with an ALQ-131 ECM pod under one wing and two AIM-9 Sidewinder air-to-air missiles under the other wing for self-defense.
Modernization
The A-10 Precision Engagement Modification Program from 2006 to 2010 updated all A-10 and OA-10 aircraft in the fleet to the A-10C standard with a new flight computer, new glass cockpit displays and controls, two new 5.5-inch (140 mm) color displays with moving map function, and an integrated digital stores management system.
Since then, the A-10 Common Fleet Initiative has led to further improvements: a new wing design, a new data link, the ability to employ smart weapons such as the Joint Direct Attack Munition (JDAM) and Wind Corrected Munitions Dispenser, as well as the newer GBU-39 Small Diameter Bomb, and the ability to carry an integrated targeting pod such as the Northrop Grumman LITENING or the Lockheed Martin Sniper Advanced Targeting Pod (ATP). Also included is the Remotely Operated Video Enhanced Receiver (ROVER) to provide sensor data to personnel on the ground. The A-10C has a Missile Warning System (MWS), which alerts the pilot to whenever there is a missile launch, firendly or non-friendly. The A-10C can also carry a ALQ-184 ECM Pod, which works with the MWS to detect a missile launch, figure out what kind of vehicle is launching the missile or flak (i.e: SAM, aircraft, flak, MANPAD, etc) and then jams it with confidential emitting, and selects a countermeasure program that the pilot has pre-set, that when turned on, will automatically dispense flare and chaff at pre-set intervals and amounts.
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