Avionics Technical Paper PDF

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My avionics technical paper for the final year avionics module, in mission/tactical avionics....

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COURSEWORK ASSIGNMENT Module Title: Avionics Systems

Module Code: 6ENT1059

Assignment Title: Avionics Technical Paper

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14022310

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Mission or tactical avionics Avionics technical paper

Abstract This is a technical paper outlining the principles of mission/tactical avionics, and the effects it has on military aircraft. It covers several different avionics systems employed on military air operations, and describes in detail the purpose of each system, as well as the way they are used.

SRN: 14022310 1

Contents Introduction........................................................................................................................................... 2 Situation awareness sensors.................................................................................................................. 2 Weapons systems.................................................................................................................................. 3 Air-to-air missiles............................................................................................................................... 3 Air-to-surface missiles........................................................................................................................3 Bombs................................................................................................................................................ 3 Rockets..............................................................................................................................................4 Aircraft defence systems........................................................................................................................4 Airborne command centres...................................................................................................................4 Tactical communication methods..........................................................................................................5 Conclusion.............................................................................................................................................5 References............................................................................................................................................. 5

Introduction Mission/tactical avionics is avionics which assists a military aircraft undertake its duty in either gathering intelligence or delivering a weapon to a target. There are a variety of types of mission/tactical avionics for both the aforementioned duties, featuring as implemented systems within an aircraft, to full aircraft dedicated to gathering intelligence.

Situation awareness sensors Situation awareness sensors are systems which detect the situation in real time around the pilot, including enemy or friendly detection, as well as other hazards, for example ground-to-air missiles. It also provides a higher accuracy for air-to-ground missiles fired from attack aircraft. An example of a system that does this is the electro-optical and infrared (EO/IR)1. This utilises automatic tracking and fire control solutions, using line-of-sight to guide a weapon to its target. It also assists in identifying targets, and can be used at night. Electro-optical and infrared lighting are used together to provide the best of both variants. Electro-optical lighting has a long range, and is easily interpretable, because it can be viewed by a human. Infrared lighting on the other hand cannot be easily interpreted by a human, and the range is limited, but it can be used in the day and night, where electro-optical lighting cannot. They are processed using field-programmable gate arrays, which captures the fibre-optic stream from the combined lens, after which is converted to a viewable picture using a graphics processing unit. Another example of a situational awareness sensor would be a wearable helmet, such as those used on the F-35 Joint strike fighter2. The helmet projects all the information that would otherwise be on a cockpit panel or Heads-Up Display (HUD) onto the helmets visor. This reduces the pilots’ workload and increases situational awareness. The helmet can also project real-time images of outside the airframe, preventing it from becoming an obstruction at crucial times within a mission. Like the EO/IR sensor mentioned earlier, this helmet provides night vision using infrared, for visual reference during a mission after light hours. 2

Weapons systems Many military aircraft, mainly attack and ground support aircraft, carry a variety of weapons systems to complete a mission. These come in a variety of forms, such as air-to-air and air-to-ground missiles; guided and unguided bombs, and rockets.

Air-to-air missiles Missiles are powered and guided explosives. Air-to-air missiles are fired upon other aircraft or even missiles, and are used to gain air superiority or take out tactical aircraft on intelligence-gathering or similar missions. They are released by the pilot from an activation switch in the cockpit, and the pilot may or may not need to have the target in their line-of-sight to shoot it, depending on the type of missile used. Shorter range missiles often use infrared tracking for its heat seeking capabilities, whereas longer range missiles often use active radar homing to achieve the required range. An example of a short-range missile is the American AIM-9 sidewinder, which is used on the RAF’s Eurofighter Typhoon, amongst others3. It has a range of 22 miles, and is activated by a proximity fuse, which detects when the missile is close to the target for maximum effectiveness. An example of a long-range missile is the British Meteor, currently under development by MBDA. It is due to be used on the Eurofighter Typhoon and the F-35, and uses inertial guidance and radar homing to reach its target4. In addition, a mid-course update is provided during the flight of the missile via datalink to check on progress to the target.

Air-to-surface missiles These missiles are used to destroy or damage targets on land or sea – these targets can vary considerably – but are mainly ships, tanks, buildings, or personnel. Like the air-to-air missiles, they are released by an activation switch in the cockpit, but the pilot is usually far away from the target before they do this. The guidance systems depend on the type of target it is aimed at – for example ships often use radar homing as they are large and slow-moving, with laser-guided missiles being more prevalent in faster moving land forces. Perhaps the most famous British air-to-surface missile is the Brimstone, also developed by MDBA. It is intended for armoured formations, and is usually released at least 37 miles away, to avoid potential lock on from anti-air defences5. It uses both active radar homing and laser guidance for increased accuracy on moving targets and to limit civilian/friendly casualties. Using the laser guidance, the missile can also detect the best place to target the missile for maximum effect.

Bombs Bombs are unpowered explosives, and can be both unguided and guided. They are dropped from a pylon on the aircraft from directly above the target, which can be any surface target. The accuracy of the bomb depends on the type of bomb – guided bombs can be provided with pre-set targets and directs itself towards it, whereas unguided bombs simply drop from the aircraft and land where gravity and forward motion takes it, irrespective of where the target is. An example of a guided bomb is the Joint Direct Attack Munition (JDAM). This is a guidance kit, which entails it being fitted onto an unguided bomb to make it guided. It uses GPS and inertial guidance, which, after the coordinates of the target are entered, directs the bomb it is fitted to onto the objective6. It has a guaranteed accuracy of 5m, much higher than that of the unguided bomb it is fitted on to.

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Rockets Rockets are powered, unguided explosives. They can be used on almost any target – both in the air and on the surface. As they are unguided, the pilot needs to be aiming specifically at the target to hit it, and cannot do anything about its trajectory once it has been fired 7. They are typically used for short range applications, such as close air support roles which usually focus on reducing personnel capability. Because of their light weight, they are more frequently found on helicopters, as they move slower so can more accurately ensure the rocket hits its required objective. It is also more lightweight, which makes it easier for helicopters to carry over their guided missile counterparts.

Aircraft defence systems Aircraft defence systems are systems that protect the aircraft from incoming attacks from land, sea and air when it is undergoing its mission. There are 2 types of aircraft defence system – passive and active. Passive defence systems are those that help both prevent the detection of an aircraft, and reduce the effect of damage once hit. An example of a passive measure that prevents detection is the use of radiation absorbent material which reduces the radar cross-section of an aircraft. An example of a passive measure that reduces the effect of damage is a plate of armour on the aircraft which helps reduce the impact area of a weapon. On the other hand, active defence systems reduce the effectiveness of the weapon attacking the aircraft before it hits. Active systems are split into 2 subcategories – hard-kill and soft-kill measures. Hard-kill measures physically intercept the enemies weapon and impede it from reaching the aircraft being attacked, whereas soft-kill measures interrupt the signature of the aircraft, altering the projection of the threat8. An example of a hard-kill measure is a towed decoy attached to the end of an aircraft that takes the impact of a threat, rather than the aircraft itself. An example of a soft-kill measure is chaff, which is small pieces of aluminium that an aircraft can release to make enemy radar show multiple returns of primary targets, which in turn prevents them from locking onto the target aircraft. A representation of what each type of system is designed to stop in relation to the aircraft using the defence systems is represented in this multi-level approach diagram 9: Detected Seen Hit

Soft-kill Hard-kill

Penetrated Killed

Passive

Airborne command centres Airborne command centres are aircraft that host a variety of communication and surveillance equipment to gather and distribute intelligence and other information. They are often large and contain workstations that enables personnel to carry out their duties. With regards to the equipment they carry, they often contain encrypted communications so the information cannot be intercepted by the enemy. In addition, they also usually feature sophisticated radar systems, which can be used for wide and area-specific surveillance, as well as air surveillance. Finally, they also normally feature

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an operations room to map out locations of the enemy and to assist in planning the missions of friendly air forces. Two examples of an airborne command centre are the E-3 Sentry and the Joint Surveillance Target Attack Radar System (Joint STARS). The Joint STARS is mainly operated by the US air force and is primarily used as an airborne command centre 10. In contrast, the E-3 Sentry, mainly operated by the RAF, is an airborne command centre in its secondary role11. They both feature passive electronically scanned array for their surveillance, but the E-3 uses a rotating radar system above the aircraft, compared to the Joint STARS side-looking stationary radome located under the fuselage.

Tactical communication methods Tactical communications are a method in which military information is transferred from one station to another12. This information is usually in the form of an order or intelligence, and is used in most military aircraft on operations. Due to the high sensitivity of this information, these systems usually use a complex encryption method to prevent the enemy from retrieving the information. They also normally feature systems that don’t allow the enemy to find the location of, or change, the signal. In addition, they can have features that prevent the jamming of the communications. One such way of preventing jamming and localisation is by frequency hopping. This entails a rapid change of frequency, so the enemy would only get a fraction of a second’s worth of signal to localise or jam it, which would be a near impossible task. Another way to inhibit threats to communication is to reduce the broadcasting power of the system used, which decreases the range of detectability.

Conclusion In conclusion, mission/tactical avionics play a key role in any military aircraft. The more developed the mission/tactical avionics on an aircraft, the higher advantage that aircraft will have over its enemy counterparts, which is why the market for this type of avionics is so high. In the future, mission/tactical avionics will develop to increase weapon accuracy and damage, decrease pilot workload, and decrease the aircrafts vulnerability as each manufacturer strives to surpass its competition, both from friendly and enemy nations.

References 1. Wilson J. EO/IR sensors boost situational awareness [Internet]. Militaryaerospace.com. 2016

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asNQ&hl=en&sa=X&ved=0ahUKEwjwuN2J3v7SAhWHKcAKHUmAA2o4ChDoAQgoMAQ#v= onepage&q=rockets%20helicopter%20weapon&f=false 8. Kerchey S. Advancing Soft Kill Capability Advancing Soft Kill Capability Through Improved Payload Positioning [Internet]. Chemring Countermeasures. 2011 Available from: http://www.chemringcm.com/~/media/Files/C/Chemring-CounterMeasures-V2/pressrelease/mast.pdf 9. Protection Systems [Internet]. Rheinmettall Defence. Available from: https://www.rheinmetalldefence.com/en/rheinmetall_defence/systems_and_products/protection_systems/index.php 10. E-8C Joint Stars > U.S. Air Force > Fact Sheet Display [Internet]. Af.mil. 2015 Available from: http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104507/e-8c-joint-stars.aspx 11. RAF - E-3D Sentry AEW1E-3D Sentry AEW1 [Internet]. Raf.mod.uk. Available from: http://www.raf.mod.uk/equipment/e3d-sentry.cfm 12. Dahinden T. Tactical communication in the air force [Internet]. Crypto magazine. 2015 Available from: https://www.crypto.ch/sites/default/files/cryptoch/magazin/CryptoMagazine_2015_1_EN.pdf

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