Premesse

Nel 1954 lo Strategic Air Command dell'USAF (United States Air Force) indisse un concorso per una cisterna a reazione adatta ad effettuare il rifornimento in volo. La versione tanker dell’aereo passeggeri Lockheed L-193 con i motori montati in coda (mai realizzato) fu dichiarato vincitore nel 1955. Dal momento che la proposta Boeing era già volante e poteva essere consegnata due anni prima il Segretario dell'Air Force Harold E. Talbott ordinò 250 cisterne KC 135A come misura temporanea fino a quando il modello Lockheed poteva essere disponibile. Alla fine gli ordini per i Lockheed furono cancellati in quanto si ritenne inutile supportare due progetti analoghi. Lockheed non costruì mai il suo jet, mentre il modello Boeing avrebbe poi finito per dominare il mercato con la fortunata famiglia di aerei di linea 707.

Genesi

Il 15 luglio 1954 il celebre prototipo Boeing modello 367-80 prese il volo per la prima volta. Il quadrireattore da trasporto ad ala a freccia fornì la base per il Modello 707 civile mentre la designazione Modello 717 (C 135) fu adottata per il tanker e fu un enorme successo per la Boeing. Il Modello 717, anche se molto simile in apparenza, si differenzia principalmente dal modello 707 da un diametro inferiore della fusoliera, l'eliminazione di quasi tutti i finestrini e dimensioni e peso minori.
La cellula di base è caratterizzata da ali e deriva a freccia, quattro turbogetti montati in gondole sub-alari, uno stabilizzatore orizzontale montato sulla fusoliera con diedro positivo sui due piani orizzontali ed un’antenna radio ad alta frequenza che sporge in avanti dall'alto dello stabilizzatore verticale.
Nel settembre 1955, al termine dei collaudi di successo con il prototipo "Dash Eighty" configurato con una sonda rigida posizionata sotto la fusoliera posteriore, Boeing ricevette il primo ordine per il KC 135A. Il primo aereo (# 55-3118) volò il 31 agosto 1956. Il KC 135A entrò in servizio con l’USAF il 28 giugno 1957, l’ultimo venne consegnato invece nel 1965.
Un totale di 732 KC 135 sono stati costruiti in un ciclo di produzione lungo ed efficiente. I primi 582 velivoli montavano una deriva più corta, in seguito ne fu introdotta una più alta per rendere più stabile il velivolo durante il decollo (la stessa modifica fu apportata ai 707 civili). Questa caratteristica fu poi introdotta direttamente sulla linea di produzione.
Quasi 500 tanker’s, tutti costruiti dalla Boeing presso le proprie strutture di Seattle, rimangono in servizio oggi. Inoltre, Boeing costruì altri 88 esemplari in oltre 30 varianti diverse per vari usi presso l’USAF, fra cui trasporti cargo, posti di comando volanti, velivoli per la ricognizione elettronica e per la mappatura fotografica. L'ultimo di questi aerei per impieghi speciali fu consegnato nel tardo 1966. La responsabilità del programma KC 135 venne trasferito alla Boeing di Wichita (Kansas) nel 1969.

Impiego

Durante la guerra del Vietnam i KC 135 Stratotanker resero la guerra aerea diversa da tutti i conflitti precedenti. Il rifornimento in volo fece sì che lontani obiettivi dei bombardamenti fossero a portata di mano. Gli aerei da combattimento, non più limitati nell’autonomia, furono così in grado di trascorrere più tempo nelle aree delle operazioni.
La flotta dei KC 135 fornì anche un prezioso contributo al successo dell’operazione Desert Storm (1991) nel Golfo Persico, volando “around-the-clock” in innumerevoli missioni per mantenere l’operatività continua dei cacciabombardieri alleati. I KC 135 costituiscono insieme ai più grandi KC 10 la spina dorsale della flotta delle aerocisterne della Forza Aerea statunitense, soddisfacendo i requisiti di rifornimento in volo di bombardieri, caccia, trasporti e ricognitori, così come le esigenze della Marina, dei Marines, e delle nazioni alleate.
Oltre che nell’USAF i KC 135 sono attualmente operati dalla forze aeree di Francia, Turchia e della Repubblica di Singapore.

Disegno

Il KC 135 dispone di quattro motori a turbogetto, montati su piloni a sbalzo sotto un ala a freccia di 35 gradi, che danno la spinta necessaria per decolli fino ad un peso lordo di 146.300 kg. Quasi tutto il combustibile interno può essere pompato attraverso una sonda rigida di rifornimento per il trasferimento del combustibile all’aereo da rifornire. Uno speciale cestello a forma di canestro, attaccato all’estremità del boom, può essere utilizzato per il rifornimento degli aeromobili dotati di sonde. L’operatore del braccio mobile utilizza una stazione montata sotto il ventre della fusoliera nella parte posteriore del velivolo e controlla il braccio, in posizione prona, visualizzando attraverso tre ampi finestroni le operazioni di rifornimento. La stiva principale offre spazio a sufficienza per sei pallet standard tipo 463L, che vengono caricati attraverso una grossa porta di carico laterale. A seconda della quantità di combustibile imbarcato, il KC 135 può trasportare fino a 38.000 kg di carico oppure sino a 80 passeggeri. L’equipaggio tipico di quattro persone è composto da due piloti, un navigatore ed un operatore della sonda.
In volo, durante le operazioni di rifornimento, il flying boom è manovrato da un operatore, comunemente chiamato "boomer". Dalla posizione prona nella carenatura sotto la fusoliera posteriore c'è una vista eccellente del boom e dell'aereo ricevitore. Normalmente, il “boomer” è in contatto radio con il velivolo ricevitore. Un piccolo joystick controlla le superfici mobili sull'estremità del braccio. Ulteriori comandi sono forniti per estendere e ritrarre l'asta e per il funzionamento di luci direzionali che forniscono informazioni della posizione ai piloti ricevitori.
Internamente il KC 135 ha serbatoi alari integrali posizionati tra i longheroni e serbatoi addizionali montati nel lobo inferiore della fusoliera, per un totale di 22. Le celle a combustibile sono realizzate in tessuto nylon di meno di un sedicesimo di un pollice di spessore, ogni cella pesa 37 chili e può contenere sino a sette tonnellate di carburante. Il sistema di alimentazione è gestito dalla cabina di pilotaggio del co-pilota. Il carburante può essere scaricato ad una velocità di 2.948 kg al minuto.

Aggiornamenti

Tra il 1975 ed il 1988 Boeing ha sostituito il rivestimento inferiore delle ali di tutti i KC 135 in servizio al fine di estendere la loro vita operativa fin oltre il 2020. Il lavoro ha comportato la sostituzione di circa 140 metri quadrati di alluminio sul lato inferiore delle ali, che supportano la maggior parte del carico alare in volo, con una lega di alluminio migliorata. La superficie alare originale consisteva di un tipo di alluminio più suscettibile alla fatica. I pannelli sono stati fresati, lavorati e sagomati dalla Boeing. La sezione inferiore dell'ala vecchia è stata tagliata e sostituita dalle nuove sezioni. Oltre ai pannelli sono stati sostituiti gli attacchi dei piloni motore. Ogni unità ha richiesto un totale di 564 pezzi, 32.200 dispositivi di fissaggio in acciaio e 19.500 rivetti di alluminio.
Nel 1981 iniziò il lavoro per la rimotorizzazione con turbofan di una gran parte della flotta dei KC 135A per sostituire i rumorosi, fumosi ed inefficienti turbogetti J57-P-59W. Il programma meno ambizioso era quello di aggiornare oltre 160 KC 135A della Air National Guard e della Air Force Reserve (insieme ad un piccolo numero di aerei per missioni speciali EC/NKC/RC 135) con motori TF33-PW-102 ricondizionati prelevati da 707 commerciali ritirati dal servizio. Dopo la modifica gli aerei furono ridenominati KC 135E.
Il montaggio del TF33 offre diversi miglioramenti importanti rispetto all'originale J57. La spinta maggiore consente all'aeromobile di operare con margini di sicurezza molto maggiori rispetto a prima e di utilizzare piste più brevi. In secondo luogo i turbofan sono più efficienti, consentendo un risparmio di costi e un’offerta di un quantitativo di carburante maggiore su profili di missione simili. Inoltre sia il rumore che l'inquinamento atmosferico sono notevolmente ridotti, un fattore importante per le unità della Guardia Nazionale che di norma operano su aeroporti civili. Infine i TF33 incorporano invertitori di spinta garantendo una maggiore sicurezza durante gli atterraggi.
Nel 1980, Boeing annunciò un importante programma di aggiornamento per il KC 135 che prevedeva il montaggio di moderni turbofan ad alto rapporto di diluizione CFM International CFM56 (designazione militare F108) in grado di offrire un’efficienza di gran lunga maggiore, una considerevole riduzione del rumore e superiore flessibilità operativa rispetto ai TF33 montati sui modelli E. Inoltre nel pacchetto di modifica era compresa l’installazione di un Auxiliary Power Unit (APU) caratterizzata da prese di aspirazione e di scarico sul lato sinistro della fusoliera posteriore che permette al velivolo di effettuare operazioni autonome da luoghi privi di infrastrutture. Con la denominazione ufficiale KC 135R, la prima conversione effettuò il primo volò il 4 agosto 1982.
La prima consegna del KC 135R ebbe luogo nel luglio 1984. Boeing ha consegnato circa 400 “R” ri-motorizzati. Ogni kit di conversione comprende piloni, gondole, 12,2 chilometri di cavi ed altri componenti di modifica del sistema. Il KC 135R può scaricare il 50 % di combustibile in più, ha un consumo inferiore del 25 %, e quindi costa il 25 % in meno. Inoltre è del 96 % più silenzioso rispetto al KC 135A. Il raggio operativo KC 135R è del 60 % superiore al KC 135E a parità di combustibile disponibile per i rifornimenti, offrendo una gamma più ampia di opzioni operative. Questa versione migliorata del venerabile KC 135 rappresenta oggi il cardine della flotta di aerei cisterna della US Air Force essendo l'ultimo KC 135E andato in pensione a Davis-Monthan AFB nel settembre 2009.
Nei primi anni 1990, uno studio di fattibilità venne intrapreso per adattare ai KC 135R dei POD subalari per il rifornimento tramite cestelli ai velivoli americani ed allearti dotati di sonda fissa. Il sistema di rifornimento Multi-Point Program è uno sforzo per migliorare l'efficienza e la flessibilità della flotta dell'Air Force. Quarantacinque KC 135R Stratotanker sono stati attrezzati per montare POD del tipo “probe-and-drogue”. Con il numero di operazioni congiunte in tutto il mondo in aumento con la capacità di rifornimento sia “probe-and-drogue” che con sonda rigida aumenta la versatilità degli aerei in una stessa missione. Inoltre estende la capacità di rifornimento a due aeromobili contemporaneamente. L’USAF ha in programma un ulteriore upgrade per migliorare il KC 135 aggiornando i cockpit con avionica più moderna.

Specifiche (KC 135R)
Caratterisitche generali

Equipaggio: quattro = pilota, co-pilota navigatore ed operatore della sonda.
Capacità: 37 passeggeri
Carico utile: 83,000 lb (37,600 kg)
Lunghezza: 41.53 m
Apertura alare: 39.88 m
Altezza: 12.70 m
Superficie alare: 226 mq
Peso a vuoto: 44,663 kg
Peso operativo: 135,000 kg
Carico disponibile: 90,700 kg
Peso massimo al decollo: 146,000 kg
Impianto propulsivo: quattro turbofan CFM International CFM56 (F108-CF-100) da 21,634 lbf ciascuno
Carburante massimo: 31,275 US gal (118 m³)

Prestazioni

Velocità massima: 580 mph (933 km/h)
Velocità di crociera: 530 mph (853 km/h) a 30.000 feet (9.144 m)
Autonomia: 1.500 mi (2.419 km) con 150.000 lb (68.039 kg) di carburante disponibile per i rifornimenti
Autonomia massima: 11.015 mi (17.766 km)
Tangenza massima operativa: 50.000 ft (15.200 m)
Rateo di salita: 4.900 ft/min (1.490 m/min)

English translation by Dario Cocco

The "Bretagne" was officially formed on January 1st, 1942 in Fort Lamy (Chad) and placed in the employ of the Permanent Air Force Detachment of Chad (DPFAT), one of its most famous characteristic was to remain under a French Commander within the Free French Air Force. The department consisted of two flying squadrons, "Rennes" and "Nantes", the aircraft available were some Lysander, Glenn Martin, Potez 29 and 540 and a single Bloch 210.
The permanent detachment at Fort Lamy in addition to ensuring the links between bases in Chad was responsible for the coverage of the French-Italian border.
Until 1943, despite the difficult conditions and with limited resources, the department has fulfilled all the tasks assigned: medical evacuations, bombing, support to the infantry and artillery, reconnaissance, refueling, liason, ground strafing, assuming responsibilities that went well beyond the norm.
His remarkable team spirit and dedication has allowed the group to write memorable pages of aviation, these actions granting the acquisitions of six awards, including the Croix de Guerre and the Legion of Honor.
In May 1944 the group moved to Villacidro, Sardinia, under commando of 31st Escadre, part of the 11th Brigade de Bombardement Moyen; from here were made primarily missions over Southern Italy. While the battle to liberate Rome began in the spring of 1944, on June 6th, with the Allied landings in northern France, the emotion wss high within the group, the bombing missions were every time closer to the much missed French territory. During one of these missions, the search for a target near Ventimiglia allowed aircrews to see, at least for a while, the French territory. On August 25th,1944, the group was involved in a new series of missions, some attacks in the south of France were also the prelude to making the first landings in the homeland territory.
With the return to France the unit was stationed on improvised airfields, first at Saint-Chamas, then at Lyon Bron, and finally on March 20th, 1945 at Saint-Dizier.
On June 18th, 1945 the B 26 Maraudes of “Bretagne”, together with those of "Lorraine" had the privilege of flying over the Champs Elysées, a symbol of newfound freedom for France. Next September, the group was transferred to Mengen, on German land.
On July 1st, 1947 the group was transformed into Transport Group "GT 1/63" and transferred on the base of Thies in Senegal, the Marauders were simultaneously replaced by Ju 52 “Toucan”, which later gave way to the North 2501 "Noratlas" (1955).
The group continued to ply the skies of Africa until 1965 when the base was returned to the Senegalese authorities. During this period in Africa the group accomplished more than 250,000 flight hours in military, economic and social operations contributing to the maintenance of the French presence in Africa; together with the departure from the base of the Thies, the GT 1/63 group was dismantled.
Also in 1965, on the "ashes" of the old department of transportation, the Escadron de Bombardement EB 2/91 was set up, with the advent of jet bombers the new department was placed under the Strategic Air Forces (Forces Aériennes Stratégiques - FAS); equipped with Mirage IVA it became part of the French Nuclear deterrence apparatus, with Cazaux (BA 120) being the base chosen for the department.
The Squadron became operational in July 1965 on a 24/7 basis with a response time of 15 minutes in case of nuclear alert.
Another time a July 1st, this time in 1996, marks another turning point for the "Bretagne", the noble banner and traditions of the department land on the Istres le Tubè air base, and are conferred to the Escadron de Ravitaillement en Vol 00 093, hence transitioning from the Mirage IVP to the C 135FR, still under command of the Strategic Air Force, but with a change in the role, from bombing to air refueling. The department acquires the eleven C 135FR and three KC 135FR and a new Squadron, the "Louve Romaine", which joins the now historic "Rennes" and "Nantes".
Both before and after the period of the acquisition of the symbol of Brittany, the Department has operated on the five continents with dedication and honor to serve the country participating in the most demanding international operations.
We cite below the most representative:
Operation Manta Epervier (Chad 1983);
Operation Chevesnes (Lebanon 1984);
Operation Daguet and Alysse (Gulf War Saudi Arabia 1990/1991);
Operation Aconit (Turkey 1992/1996);
Operation Crécerelle and Salamanders (Bosnia 1993);
Operation Turquoise (Rwanda 1994);
Operation Trident (Kosovo 1999);
Operation Heracles (Afghanistan 2001-2002);
In September 2004 the department was renamed IBC 93, and from September 1st, 2009 the department acquired its present name GRV 2/91 "Bretagne" (Groupe de Ravitaillement en Vol).
The GRV 2/91 depends from the Air Force Strategic Command (CFAS Commandament des Forces Aériennes Stratégiques) based on the airbase BA 921 "Frères Mahé" at Taverny (20 km north of Paris). The air base which is home to the Squadron is that of Istres Le Tube (BA 125 Charles Monier), located a few kilometers from the city of Marseille, one of the most important and larger of the French Air Force.
The primary task of the "Bretagne" is the nuclear deterrent, the C 135FR form with the Mirage 2000N, Rafale F3 and the ASMP missile an aeronautic "quartet" that plays a primary role in defending the nation. The support to nuclear-capable bombers of Armèe de l'Air is a task that the department has developed through its decades-long history, even in years of major development was done from three different air bases, Avord, Mont de Marsan and of course Istres, since the early sixties in support of the Mirage IVA, then, with the retirement of the big Dassault twin jet, the task has been transferred to the Mirage 2000 (Nuclear Strike) and to the Rafale F3 of CFAS, the Mirage 2000N being the nuclear bombing version of the M 2000C fighter.
Same for the Rafale, the task of nuclear deterrence is guaranteed by the carriers with the ability to carry the medium-range air-ground missile ASMP-A (Air Sol Moyenne Portée Amélioré) equipped with a "TNA" Thermonuclear Airborne warhead of 300 kt.
One of the so-called "secondary" tasks of GRV 2/91 is to provide support for in-flight refueling to all tactical aircraft of Armée de l'Air and Marine Nationale, therefore Mirages 2000C/D/5F/N, Rafales B/C/F3/M and Mirages F 1CR/CT, both during their normal activities at the national level and in the event of activities abroad, including of course activity on the national colonies overseas, particularly in French Guyana by the "Centre Spatial Guyanas" at Kouros, European Space Agency's launch base. Remaining at the national level another employ of Istres’ tankers is to provide support for the E 3F AWACS (Airborne Warning and Control System) based at Avord and for the C 160 Transall based at Evreux, while international agreements are in place to support the air forces NATO.
Another institutional task assigned to “Bretagne” is transportation, particularly in support of missions "outside the area"; currently two C 135FR are assigned to international missions, one in Chad and one in Afghanistan, both playing in the field AAR and transport missions. It should be pointed out that the transport role of both personnel and goods is carried out exclusively by the C 135FR purchased directly by the Armée de l’Air from Boeing because the KC 135R acquired second-hand by the USAF do not have a loading platform designed for the transport, the floor being made wood then unsuitable to house the heavy pallets and even hook the normal seats.
Instead we see now another extremely topical task, recently been pointed out by the "White Paper", prepared on annual budget by the French armed forces, that the tankers of 2/91 also have to cater for MedEvac (Medical Evacuation) operations, each of the two kits acquired for the task of medical evacuation able to accommodate four to six injured people with medical accompanying personnel, which is why the Group may be called at any time to support the populations in the event of environmental disasters, the first mission of MedEvac made by a specially configured C 135FR was held in 2010 following the terrorist attack in Karachi (Pakistan). Another task assigned to the department is the reconnaissance, the aircraft for obvious reasons having a limited capacity in this role, while thanks to a HF radio communication system is one of the vectors of AdlA that can provide strategic communications over oceanic distances.
Concluding we say that Brittany has been delegated by the Command of Chief of Staff to plan and organize operations “outside the box” and long-term for Air Force, through a dedicated operations room are implemented all actions necessary, including overflight clearances, coordination with other assets, organization of logistical and technical support for aircraft that are transferred on the BA 125 base as a starting point for planned missions. A recent planning activity was put in favor of the structure of the Belgian Air Force and Navy for the transfer to Afghanistan, while training activities are planned missions on a yearly basis when an aircraft is being sent to the U.S. for a month.
Since June 1993 the department has the use of a flight simulator for training of crews, which is mainly used for initial training of pilots and navigators coming from the Air Force schools, and to train crews to all emergency procedures that may arise during the flights.
The current equipment of GRV consists of eleven C 135FR, purchased directly from Boeing as C 135F as in 1962-1963, one aircraft was lost in 1972, and three KC 135R purchased second hand by the USAF in 1997-1998. The original C 135F were re-engined in the early eighties by replacing the original Pratt & Whitney J57 turbojets with current turbofan CFM 56-2B. The C 135FR recently have been equipped with underwing (Wingtip) Hose-and-Drogue MK 32B Pods made by Flight Refueling Ltd, the addition of these two pods under the wing tips allows to supply two planes simultaneously, and together with the Flying Boom allows to refuel all types of aircraft.
A further update of the C 135FR and KC 135R will be introduced from 2013, the improvements will cover the cockpit with the installation of multi-function displays (MFD) and new navigation systems, with aircraft upgrades to be completed by 2015.
About the replacement of the C 135FR the decision is still far away and will not be taken before 2017; the new Hollande government, however, will necessarily take the decision no later than 2020, date set for the final withdrawal of Boeing four-jet. GRV expects to make no predictions, the A 330 MRTT is playing at home, but the experience of a US made airplane has left its mark.

The Boeing KC-135 Stratotanker

Background

In 1954 USAF’s Strategic Air Command held a competition for a jet-powered aerial refueling tanker. Lockheed's tanker version of the proposed Lockheed L-193 airliner with tail-mounted engines (never built) was declared the winner in 1955. Since Boeing's proposal was already flying, the KC-135 could be delivered two years earlier and Air Force Secretary Harold E. Talbott ordered 250 KC-135 tankers until the Lockheed's design could be manufactured. In the end, orders for the Lockheed tanker were dropped rather than supporting two tanker designs. Lockheed never produced its jet airliner, while Boeing would eventually dominate the market with a family of airliners based on the 707.

Genesis

On 15 July 1954, Boeing's famous Model 367-80 prototype took to the air for the first time. The four-jet, swept-wing transport provided the basis for the prolific Model 707 civil airliner and Model 717 (C-135) tanker/transport families, and also set the design philosophy which extended throughout Boeing's hugely successful airliner dynasty. The Model 717, although very similar in appearance, differs primarily from the Model 707 by having a smaller-diameter fuselage, deletion of cabin windows, and reduced size and weight.
The basic airframe is characterized by swept wings and tail, four underwing-mounted engine pods, a horizontal stabilizer mounted on the fuselage near the bottom of the vertical stabilizer with positive dihedral on the two horizontal planes and a hi-frequency radio antenna which protrudes forward from the top of the vertical fin or stabilizer.
In September 1955, following successful trials with the "Dash Eighty" prototype configured with a Boeing-designed flying boom under the rear fuselage, Boeing received the first order for the KC-135A tanker. The first aircraft (#55-3118) flew on 31 August 1956. The KC-135A entered service with the U.S. Air Force on 28 June 1957. The last tanker was delivered to the Air Force in 1965.
A total of 732 KC-135s were built in a long and efficient production run. The first 582 aircraft were built with a short tailfin, but from then on a taller fin was introduced to make the aircraft more stable during takeoff. This feature was eventually retrofitted to all aircraft in the production line (including civilian 707s).
Almost 500 of the tankers — all built by Boeing at its Seattle facilities — remain in service today. In addition, Boeing built 88 aircraft in over 30 different models for other USAF uses, such as cargo transports, flying command posts, electronic reconnaissance and photo mapping. The last of these special-purpose aircraft was delivered in late-1966. Responsibility for the KC-135 was transferred to Boeing in Wichita in 1969.

In service

During the war in Vietnam, KC-135 Stratotankers made the air war different from all previous aerial conflicts. Aerial refueling brought far-flung bombing targets within reach. Combat aircraft, no longer limited by fuel supplies, were able to spend more time in target areas.
The KC-135 tanker fleet also made an invaluable contribution to the success of Operation Desert Storm (1991) in the Persian Gulf, flying around-the-clock missions to maintain operability of allied warplanes. The KC-135s form the backbone of the Air Force tanker fleet, meeting the aerial refueling requirements of bomber, fighter, cargo and reconnaissance forces, as well as the needs of the Navy, Marines, and allied nations.
In addiction to USAF KC-135s are currently operated by the French Air Force, the Turkish Air Force and the Republic of Singapore Air Force.

Design

The KC-135 has four turbojet engines, mounted under 35-degree swept wings, which power it to takeoffs at gross weights up to 322,500 pounds (146,300 kg). Nearly all internal fuel can be pumped through the tanker's flying boom, the KC-135's primary fuel transfer method. A special shuttlecock-shaped drogue, attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. A boom operator stationed in the rear of the aircraft controls the boom while lying prone monitoring through three large windows the refueling operations. The main cargo hold provides enough room for six standard 463L-type cargo pallets, which are loaded through a side cargo door. Depending on fuel storage configuration, the KC-135 can carry up to 83,000 pounds (38,000 kg) of cargo or up to 80 passengers. A crew of four is comprised of two pilots, a navigator and a boom operator.
While in flight, the aircraft's large flyable boom is controlled by a boom operator, commonly called "boomer". Performed from a prone position in a fairing under the rear fuselage, there is an excellent view of the boom and the receiver aircraft. Normally, the boomer is in radio contact with the receiver aircraft. A small control column is provided which is linked to control surfaces on the end of the boom. Further controls are provided for extending and retracting the boom and the operation of director lights which provide positional information for receiver pilots.
Internally, the KC-135 features integral wing tanks between the spars, and further tanks in the lower lobe of the fuselage, making a total of 22. The fuel cells are made of nylon fabric less than one-sixteenth of an inch thick — a cell weighing 80 pounds will hold seven tons of fuel! The fuel system is managed from the cockpit by the co-pilot. Fuel can be offloaded at a rate of 6,500 pounds (2,948kg) per minute

Upgrades

Between 1975 and 1988, Boeing replaced the lower wing skins of all surviving KC-135s to extend their useful lives to beyond the year 2020. The work involved replacing about 1,500 square feet of aluminum on the underside of the wings, which carry most of the wing load in flight, with an improved aluminum alloy. The original wing surface consisted of a type of aluminum more susceptible to fatigue. Skin panels were milled, machined and contoured at Boeing. The wing then went into a rivet assembly jig where stiffeners and skins were joined. The bottom section of the old wing was cut away and replaced by the new sections. In addition to the skin panels, engine strut fittings were also replaced. Each unit required a total of 564 parts, 32,200 steel fasteners and 19,500 aluminum rivets.
In 1981, work also began on re-engining a large portion of the C/KC-135A fleet with turbofans to replace the noisy, smokey, and inefficient J57-P-59W turbojet engines. Of the two programs, the least ambitious was that to upgrade over 160 KC-135A tankers of the Air National Guard and Air Force Reserve (together with a small number of special mission EC/NKC/RC-135 aircraft) with refurbished TF33-PW-102 engines taken from used, commercial 707 airliners. After modification, the airplanes were redesignated as KC-135E.
Fitment of the TF33 provides several important improvements over the original J57. The greater thrust allows the aircraft to operate on far greater safety margins than previously possible, and to use shorter runways. Secondly, the fan engines are more efficient, offering cost-saving and greater fuel offloads on similar mission profiles. Also, noise and air pollution is considerably reduced, a major factor for Guard units operating from civilian airports, and lastly the TF33s incorporate thrust-reversers for enhanced safety during landings.
In 1980, Boeing announced a major upgrade program for the KC-135 involving the fitment of CFM International's CFM56 (military designation F108) high bypass-ratio turbofan engine to offer far greater fuel efficiency, noise reduction and operational flexibility than the E-model's TF33s. Also included was the addition of a Quick Start Auxiliary Power Unit (QSAS), characterized by intake and exhaust ports on the port side of the rear fuselage, which allows the aircraft to undertake autonomous operations from austere locations. Under the company designation KC-135RE, the first conversion took to the air on 4 August 1982. Designated KC-135R in service, the first delivery took place in July 1984. Boeing has delivered approximately 400 re-engined KC-135Rs. Each kit includes struts, nacelles, 12.2 miles of wiring, and other system modification components. The KC-135R can offload 50 percent more fuel, is 25 percent more fuel efficient, costs 25 percent less to operate and is 96 percent quieter than the KC-135A. The KC-135R's operational range is 60% greater than the KC-135E for comparable fuel offloads, providing a wider range of basing options. This re-engined and enhanced version of the venerable KC-135 tanker is now the mainstay of the U.S. Air Force's tanker fleet as the last KC-135E was retired at Davis-Monthan AFB in September 2009.
In the early-1990s, a feasibility study was undertaken to fit the KC-135R with wing pods for the refueling of probe-equipped aircraft from U.S. and foreign services. The Multi-Point Refueling System Program is an effort to enhance the efficiency and flexibility of the Air Force’s air refueling fleet. Forty-five KC-135R Stratotankers are being outfitted to accept wingtip hose-and-drogue and air refueling pods for refueling NATO and U.S. Navy aircraft. With the number of worldwide joint and combined military operations on the rise, the Department of Defense directed the Air Force to outfit part of its KC-135 fleet with the capability of refueling both probe-and-drogue and boom receptacle aircraft on the same mission. This also the capability of refueling up to two probe-and-drogue aircraft at the same time. The U.S. Air Force will continue its effort to improve the KC-135 fleet fitting the cockpits with updated avionics.

Specifications (KC-135R)

General characteristics

Crew: 4: pilot, co-pilot, navigator and boom operator
Capacity: 37 passengers
Payload: 83,000 lb (37,600 kg)
Length: 136 ft 3 in (41.53 m)
Wingspan: 130 ft 10 in (39.88 m)
Height: 41 ft 8 in (12.70 m)
Wing area: 2,433 ft² (226 m²)
Empty weight: 98,466 lb (44,663 kg)
Loaded weight: 297,000 lb (135,000 kg)
Useful load: 200,000 lb (90,700 kg)
Max. takeoff weight: 322,500 lb (146,000 kg)
Powerplant: 4 × CFM International CFM56 (F108-CF-100) turbofan, 21,634 lbf () each
Maximum Fuel Load: 31,275 US gal (118 m³)

Performance

Maximum speed: 580 mph (933 km/h)
Cruise speed: 530 mph (853 km/h) at 30,000 feet (9,144 m)
Range: 1,500 mi (2,419 km) with 150,000 lb (68,039 kg) of transfer fuel
Ferry range: 11,015 mi (17,766 km)
Service ceiling: 50,000 ft (15,200 m)
Rate of climb: 4,900 ft/min (1,490 m/min)

Maintenance is carried out by a body in charge called ESTS 15/92 (Escadron de Soutien Technique Spécialisé), this unit consists of about 350 people who work in various technical specialties: avionics, electronic, mechanical, structural etc..
The ESTS staff carries out all maintenance activities on the Istres air base, utilizing a hangar which can accommodate two C 135 at the same time; there is also another hangar recently built which cannot fully accept the aircraft, leaving out of the rear part of the tail.
In case of out of area operations necessary personnel is to be taken on board following the mission to ensure adequate assistance in military bases outside the national borders.
While in the detachments where the presence of Istres tankers is stable, as in Chad and Afghanistan, there are cells of specialists who perform the necessary maintenance activities.
At Istres maintenance center are carried out two levels of maintenance, Level 1 on all aircraft, Level 1 "plus" on certain parts, while for Level 3 aircraft are sent to Nimes-Garons at Sabena Technics FNI commercial company, while for some intermediate check the work is entrusted to the technical section of the national airline Air France.

The air refueling (AAR - Air to Air Refueling) is a technique that allows to transfer fuel in flight from a supply aircraft (tanker) to another aircraft (Receiver), this technique, used exclusively by the military allows to significantly increase the aircraft autonomy.
The first experiments with air refueling date back to the twenties, the method was very similar to that of today, a hose was lowered from the aircraft flying at an altitude greater than that of the other flying at a lower level, the fuel was transferred with the same system used for the ground supply, via a dispenser inserted directly into the tank, making it extremely dangerous. In 1935 the brothers Fred and Al Key experimented during their flights a particular system designed by AD Hunter which was very similar to the systems which are now on board of modern tankers.
In 1949 (between February 26th and March 3rd) a Boeing B 50 "Lucky Lady II" of USAF (United States Air Force) completed an around the world flight in 95 hours and one minute without making landings, the three in-flight supplies made by eight KB 29M which enabled it to make the first circumnavigation of the world's history, demonstrating unequivocally that there was no longer any geographical boundary for the first world power, putting the Air Force in a foreground strategic role.
The KB 29, made by converting the powerful propeller four-engine bomber B 29 Superfortress, was the ancestor of all modern tankers, another prominent transformation was that of KC 97 Stratotanker, derived from C 97 Stratofreighter. The quintessential tanker remains the KC 135, very similar to the B 707 but designed and built specifically for the "AAR" role. Several other aircraft were adapted for this role, such as: KA 3 Skywarrior,, KA 6 Intruder, KC 130 Hercules, KC 10 Extender, up to the modern KC 767 and A 330 MRTT. Even the UK industry has been very active in this area, just quote the Vailant, the Victor, the Vc 10 and the TriStar, all these Royal Air Force aircraft using exclusively the Probe-and-Drogue system . Obviously also the Soviet Union during the years has been using tanker aircraft, most notably the Myasishchev 3MS2 and M-4-2, the Tupolev TU 16 and the Ilyushin IL 76 (the only one currently in service).
There are many air forces that have the "AAR” capacity, the main fleets are in force at the major world powers: the United States, Russia, United Kingdom, Germany, France, India, Pakistan, Italy, Japan and China, many other nations have structures that vary in number and quality of its air force inventory, we list the most representative: Canada, Brazil, Venezuela, Chile, Iran, Israel, Morocco, South Africa, Singapore, Saudi Arabia, Turkey, Netherlands, Spain and Sweden, while the United Arab Emirates and Australia are acquiring this capability with the arrival of the new A 330 MRTT (Multi Role Tanker Transport).
During the decades of the modern era, more than once the specialty of the refueling revealed to be indispensable, as a typical example we mention the Falklands War of 1982 (Islas Malvinas), conflict developed between Argentina and the United Kingdom for possession and control of the archipelago, after the initial invasion of a handful of commandos from Armada Argentina, followed by more substantial naval and land activities. The British found that diplomacy had failed, had to organize to send a naval task force able to operate at very large distances, while for air operations the task was much harder; it was chosen Wideawake airbase, on the island of Ascension, as a decentralized base to set up the necessary arrangements. The Royal Air Force decided to deploy there its own Avro Vulcan bombers and Victor tankers. These four-jets to reach the Falklands had to fly for 6000 km, the distance that separates the Islands in the Atlantic Ocean, the missions were carried out by performing as many as 11 supplies for each bomber in flight, necessary to cover the outbound and return missions. As added value these missions showed to the South American military dictatorship that the British bombers were also able to cover the remaining 450 km that were missing to get straight on Argentine soil.
Another massive use of air refueling took place during the redeployment of NATO forces in the Middle East to respond to the Iraqi invasion of Kuwait (Desert Shield), and subsequently to develop the first Gulf War, the aero-tactical structures of the coalition during "Desert Storm" operated from several air bases arranged in neighboring countries thanks to the tankers. A record for the occasion was made by some B 52H of the United States Air Force which took off from Barksdale Air Force Base AFB (Louisiana) and flew directly to the Gulf targets; the round-trip lasted a total of 35 hours of uninterrupted flight thanks to the support of KC 135 and KC 10.
There are two ways to refuel in flight, the first is via a rigid telescopic probe (or High-Speed Flying Boom), which, managed by the "boomers" is inserted into the receptacle at the top of the receiver aircraft; the "receiver" once positioned at a stable speed plays a passive role all in all, the rigid probe is extended to a maximum extension of 20 feet (6 meters), and with a downward angle of 50 degrees. The rigid probe can be also regulated laterally (azimuth) with a maximum angle of 10 degrees on both sides, the correct engagement into the receptacle allows the release of the electric valves and fuel delivery, the management of the pumps for the transfer and the amount of fuel delivered is managed by the supply operator (boomer), the pilot of the "receiver" in addition to being in radio contact with the boomer is helped by some light signal placed under the refueller, this system can deliver fuel to only one aircraft at a time. The USAF is the largest user of the rigid probe, almost all the aircraft in service with the U.S. Air Force. We mention some of the most popular models: F 16, F 15, F 22, F 35, C 17, C 5, B 52, B 1, B 2, have just the receptacle.
The second system is called Probe-and-Drogue, in this context there are several subsystems on the market, the most common until a few years ago was the flexible probe that was applied on the boom, now there also are the pods Hose-and-Drogue applied on the wing tips, the same pod can also be applied on the rear of the fuselage, the IL 76 and IL 78 are the main users of this variant. Another system that uses the flexible probe is the "Buddy Buddy", in this case pods are used exclusively by specific tactical aircraft such as the Tornado or the F / A 18. In modern aircraft, like the KC 767 and A 330 MRTT, three flexible probes are used, Multi-Point Refueling System (MPRS) in addition to the rigid, the Hose-Drogue are placed on the outer wing and near the Flying Boom, thus allowing to refuel up to three aircraft simultaneously.
The use of Hose-Drogue system is relatively simple, the supply aircraft releases at his rear for approximately twenty meters the pipe ending with the classic basket, the "receiver" is equipped with an external probe that through the action of the pilot is inserted in the drum, in this case the boomers following operations from the cockpit on a dedicated console, the release of the fuel takes place with the same modalities of the rigid probe, the visual inspection of the situation takes place by means of the video-cameras. This system "Probe-and-Drogue" is the prerogative of all aircraft of not American design, then French, English and Italian, but not exclusively because even the U.S. Navy and U.S. Marines have employed this system. The French with their Mirage and Rafale, are the promoters of the use of not retractable external probes, mechanically simpler but less aerodynamically efficient, while the most of the remaining aircraft designed for the use of the flexible probe are equipped with a retractable probe that fits completely within the fuselage, we remember the Tornado, Typhoon, the F/A 18.
Finally, one can not mention that this system can also refuel helicopters (CH 53, EH 101, CH 47 and UH 60) and some large transport aircraft (C 130, C 27, A 400M), in this case the receiver is equipped with a probe much longer that extends well ahead of the cockpit.
The two types of refuelling also differ for the quantity of fuel transfer, the rigid probe allows you to transfer about 6,000 pounds per minute of JP-8 (Avtur, Jet A1, JP-4 JP-8 or kerosene is used almost exclusively as jet fuel), while the flexible probe allows the transfer of approximately 4,000 pounds per minute, and then is less performant, even if the considerable advantage in favor of the second is, as amply illustrated previously, the ability to supply more aircraft simultaneously.

Our presence at the GRV 2/91 took place in a span of three days, this time allowed us to carry out two flight missions on board the French Tankers, it should be emphasized that good corporate governance by Sirpa Air in Paris has made sure that we were inserted in a excercise of primary importance, we have been "invited" to be present during a week called "La Fayette Exercise week".
The event included multiple sessions of in-flight refueling by Startotankers in favor of various tactical planes of the French, Belgian and Spanish Air Forces.
The Belgische Luchtmacht (Belgian Air Force) was present at Istres with three F 16AM "call sign Bugatti", the Ejercito de l'Aire with four EF 18A of Wing 15 "call sign Tapas", but also from Zaragoza redeployed at Istres for the occasion, the Armee de l'Air Mirage 2000N of course with the CFAS Istres (EC 02,004 La Fayette) "call sign Porsche" with Mirage 2000-5F and Rafale C BA 118 from Mont de Marsan "call sign Peugeot (Mirage)", with Mirage 2000C / B of the BA 115 Orange/Caritat "call sign Lada", with the former BA 103 Mirage 2000C of Cambrai "call sign Lada", finally with the Rafale B BA 113 at Saint-Dizier "call sign Benz".
The first mission was carried out on board a C 135FR (F-UKCH AF 63-12736), call sign of the mission "Shell 47", in a standard configuration with the two underwing pods and the rigid probe, in this way it was possible evaluate two completely different types of AAR. The second mission has instead been carried out aboard a KC 135R (F-UKCM AF 62-3497), call sign "Petrofin 97" with the Probe-and-Drogue system installed on the Flying Boom, allowing them to attend a further supply system and in effect covering 100% of the existing types. Both missions were carried out in an area located to the west of France near Perpignan and close to the Pyrenees, both outputs have lasted four hours, divided in 45 minutes for the outbound flight and the same for the return, about a time circuits during refueling (15 aircraft with the first mission, about 12 second), the final half hour of the flight was spent in a series of training procedures for approach and touch-and-go on the Istres base simulating different configurations: normal procedures, and tactical landing simulation plus "engine failures”
The crew type for both flights was made by a Commander Pilot, one Co-Pilot, a Navigator, a Technical Officer which doubled as "boomer", the only difference for the second task, the presence of an additional Navigator under training.
Certainly the experience is to be classified as exciting, it would be to say much more yet, but we conclude by saying that the KC 135 Tanker is still the only aircraft in service that allows you to see and almost "touch" the peculiar activity of the supply in flight by sending all sensations imaginable and possible, plus a lot easier for photograph taking, using exactly the location of the boomer.