Role of strategic tanker in PAF

The Air-to-Air refuelling (AAR) became a norm in air operations in Afghanistan and Iraq. During air operations in recent Afghanistan/Iraq missions, the U.S. and its allies had continuous support of airborne air-to-air refuelling platforms and logistic support from U.S. bases in the Middle East. Logistics and supply challenges were not faced during mission planning and operations of these conflicts. But this is not the same case each time. War plans are made in the worst case scenarios—running out of gas, shortage of supply, unavailability of resources at the crucial time. These setbacks cause forces to change from offensive role to defensive.

The operations conducted by Pakistan Air Force (PAF) in past six decades had been mostly against fixed and pre-planned targets. These pre-planned targets have a scheduled time-on-target depending upon the mission planning. The surface attack missions conducted on the Indian Air Force (IAF) bases during 1965 and 1971 wars are two such examples. During the precision air strike missions conducted in FATA/South Waziristan in recent times, ‘On-call’ targeting was achieved in time sensitive environments. In these operations, the Air Force conducted precision strikes on the request of ground forces operating in the area. These missions did not require the use of air borne AAR platforms.

Even in the past, the PAF felt the need to have longer on-station time for its fighter aircraft. To increase the operational range of these aircraft, the PAF in 1980s, improvised the design of F-6 (Mig-19) aircraft by the addition of Gondola fuel tank. It was mounted under the lower fuselage/centreline station of the aircraft.

For a fighter squadron, maintaining operational readiness of its aircraft during a long distance mission is an absolute necessity. If a formation of such aircraft runs out of fuel, their replacement is mandatory. Two things can be done to address this issue: one, availability of replaceable and operational aircraft from the nearest airbase; two, addition of external fuel stations, during weapon loading, to enhance the range of the aircraft. However, external fuel tanks add noticeable amount of drag in performance of the aircraft. The drag factor decreases the agility and performance during flight.

The aircraft in interceptor role, such as scrambled in case of an imminent threat aircraft—vectored to a nearest destination, requires little or no external fuel. On the other hand, the use of external fuel stations is mandatory for an aircraft on long-distance Combat Air Patrol (CAP) or long-distance training mission.

Limited fuel scenario of fighter aircraft:

Now consider a scenario of a fighter aircraft participating in an offensive/counter-offensive operation during a conflict: the aircraft has been in the air for a long period of time. Either it has to return to base, refuel and be airborne again or it has to ask for aerial refuelling.

Without getting refuelled, accomplishing desired objectives under a vulnerable airspace or over enemy territory is difficult to achieve. In case of any imminent threat from ground or air, the pilot has to jettison its external fuel stations to achieve a low-drag and agile configuration. If his aircraft is with smaller amount of fuel then returning home safely with appropriate fuel reserves is the only prayer a fighter pilot needs!

In present day air defence operations, fighter aircraft are flown to patrol both long and medium distance sectors. Their patrol is in collaboration with Airborne Early Warning & Control (AEW&C) systems and ground based air defence assets. The farther the patrolling position is from its operating base, the more will be the fuel requirements. To provide continuous air defence coverage, constant patrolling is required.

A solution to this ‘shorter leg’ patrol problem is deployment of an AAR tanker aircraft. Aircraft with good amount of available fuel can be vectored towards the patrolling fighter aircraft, which can continue combat patrol till their replacements arrive.

PAF current fleet & AAR needs:

Today PAF operates a mixture of U.S built F-16 Fighting Falcon, Chinese built F-7P/PG, Pak-China’s JF-17 and French built Mirage-III/V aircraft. Acquisition of two squadrons of FC-20/J-10 multirole fighter/bomber aircraft from China is also under discussion since past few years. According to the modernization doctrine of PAF, F-7P and most of Mirage-III/V aircraft will eventually be replaced by JF-17 Thunder till 2015/2016. F-7PG will be used in air superiority role, hence operating in the friendly skies with shorter legs most of the times. Two squadrons of ROSE-III upgraded Mirage-V aircraft will be the backbone of PAF in deep strike and night strike operations till the arrival of FC-20/J-10 aircraft.

IL-78 MRTT & its role in PAF:

In late 2009, PAF received first IL-78 Multi-Role Tanker Transport (MRTT) aircraft from Ukraine. The fourth and last IL-78 was delivered to PAF in late 2011. The acquisition of these mid-air refuellers turned a new leaf in the PAF’s book of air operations. IL-78 MRTT has a hose drogue refuelling system with a capacity of carrying 85,720 kg(188,977 lb)fuel. It has four turbofan engines, each of which is capable of delivering 118 kN (26,500 lbs) thrust. It has the capability to refuel two aircraft at one time but aerial refuelling probe in the recipient aircraft is a pre-requisite. It can be used in both tanker and transport role too.

In 2010, PAF procured 30 refuelling probes from South Africa for its ROSE upgraded Mirage fleet. The flight trials of IL-78MP with Mirage aircraft were conducted in Exercise High Mark 2010. PAF has plans to integrate retractable aerial refuelling probe in the second block of JF-17 Thunder aircraft, whose production will commence from mid-2012.

PAF also operates a fleet of 63 F-16s. The Block-15 F-16 A/B fleet is undergoing modernization program known as Mid Life Update (MLU), which will enhance the service of these aircraft till next two decades. The acquisition of boom-type mid-air refueller for these aircraft came under discussion in the past, but it was declined in favour of F-16C/D Block52 aircraft with Conformal Fuel Tanks (CFT) and JF-17 aircraft. PAF F-16s have also conducted in-flight refuelling missions with USAF KC-135 and KC-10 tankers in various multi-national exercises, but procurement of an F-16 specific boom type refueller is currently not on the list.

The Pak-China JF-17 will be the mainstay aircraft in PAF for a very long time. It has loiter time of over 3 hours and strike range of 1,352km (730nm). For it to become a point defence fighter, addition of an aerial refuelling probe is a necessary requirement. Refuelling and continuing the mission will not only increase the on-station time of these aircraft, but it will also help PAF in maintaining its operational readiness level.

The induction of strategic tanker aircraft will enhance endurance and range of the fighter fleet, allowing these aircraft to patrol for much longer time or strike deep inside the enemy territory. Furthermore, it also enhances the strategic airlift capability of PAF. It can also be used as a Forward Air Refuelling Point (FARP), providing greater loiter time to the fighter aircraft. In-flight refuelling to a considerably large package will meet various operational needs of PAF. These aircraft can also be deployed to a remote base along with small number of fighter aircraft. Such deployment can itself operate as an autonomous fighting unit. IL-78 Strategic tanker and transport aircraft can also be used to carry large amount of fuel, ration and equipment to remote army stations. Their use for carrying military personnel, vehicles and tanks could prove to be a game changer in any situation. Such economy of effort, better performance and multi-mission profile under one package makes IL-78 as both strategic AAR and strategic airlift platform.

In 1980s, PAF improvised the design of F-6 (Mig-19) aircraft by the addition of under-belly Gondola fuel tank. The purpose was to increase range of these aircraft.

A ROSE-I upgraded Mirage-III formation and IL-78 MRTT during mid-air refuelling trials in Exercise High Mark 2010. PAF has procured four such mid-air refuelling platforms.

PAF F-16s en route to USA for participation in Exercise Red Flag 2010 is being refuelled by a USAF KC-135 tanker over Atlantic Ocean. The acquisition of boom-type mid-air refueller for these aircraft came under discussion in the past, but it was declined in favour of F-16C/D Block52 aircraft with Conformal Fuel Tanks (CFT) and JF-17 aircraft.

This article was published in The Weekly Pulse, Islamabad on April 06, 2012 .

Maintenance Programs of Pakistani Falcons

Pakistan Air Force (PAF) inducted F-16 Fighting Falcon in January 1983. This provided a quantum leap to the PAF. It was PAF’s first experience of handling such a modern day fighter aircraft. From 1986 to 1988 F-16s participated in air defence missions carried out in Afghan War (1979-1988). F-16s played a vital role in guarding the western borders of Pakistan from Soviet/Afghan intruding aircraft. During the war PAF flew a total of 10,939 sorties and logged 13,275 hours.
This extreme usage of F-16s in the start of its career raised serious questions about its service life in coming decades. PAF went for development of in-house facilities for maintenance and overhaul of F-16 components. A F-16 Upgrade Cell was established at Sargodha Air Base. This cell was capable of performing depot level structural and avionics related modifications in the F-16s. These modifications include Operational Capability Upgrade (OCU), 479 Bulk Head Replacement Module and Wing box modifications.
In 1989, Mirage Rebuild Factory (MRF) at Pakistan Aeronautical Complex (PAC), Kamra was assigned the task of overhauling the Pratt & Whitney F100-PW-200 turbofan engine that powers the F-16 fleet in PAF service. The F-16’s structural modifications were made in engine, fuselage, ailerons and flaps. These structural modifications were a part of its type extension program. Reinforcement plates were also added on the fuselage to strengthen the structural integrity of the F-16s, thus extending its service life.
MRF has also upgraded the F100 engine from 200 to 220E configuration. The -220Econfiguration provides better performance and greater reliability. Up to 26 modifications were made in F-100 engines modules including fan, engine core, fuel nozzles, gearbox, high pressure turbine…etc
Improvement in the service life of various F-100 modules is as follows:

Fan Module 1800-4000 Hours
Core Module 4000 Hours
 Turbine 3500 Hours
Augmentor Module 4000 Hours
Gearbox Module 4000 Hours

The repair, up-gradation and overhaul of F-100 Engine, replacement of wing and fuselage fuel cells are also carried out by MRF. MRF has been certified for aircraft painting and de-painting as well.The F-16’s avionics, structuraland engine related modifications allowed the PAF to maintain a high level of readiness despite U.S. sanctions and arms embargo from the West and did not hamper the operational preparedness of the fighting force during both times of peace and war.
Over the years,F-16s have participated in various multinational exercises around the globe. The devoted ground crew has always ensured the combat ready status of these falcons. F-16s participation in counter insurgency operations in Global War on Terror are the recent example of their combat record.

In June 2009, PAF, Lockheed Martin and United States Turkish Aerospace Industries (TAI) signed a contract of Mid Life Update (MLU) of these F-16s. Under this program, TAI will upgrade 41 F-16 A/B Block-15E aircraft at the TAI facility in Ankara, Turkey. It will also provide training to PAF technicians and engineers on MLU F-16s. After getting the MLU, these aircraft will be a mainstay aircraft in PAF for at least two decades. PAF will use these modified F-16s as a deterrent to regional threats and to strengthen the defence of Pakistan.

A F-16B with structural reinforcement plate visible on its fuselage. Inset is close up of a structural reinforcement plate.

A F-16 fuselage without structural reinforcement plates.

F100-PW-220/-220E Cutaway View (Newest Configuration) [P&W graphic]

F-100 engine undergoing testing.

Engineers working on F-100 power plant at MRF facility. The F-100 modules repair/overhaul consists of Inlet Fan Module (IF), Fan Drive Turbine (FDT) Module, Core Module, Gearbox Module, and High Pressure Turbine Module (HPT).

F-16A undergoing painting at aircraft painting facility, MRF.

An example of neat paint job done.