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Optimum Aircraft Mission Designs

Issue No 17, 20 February 2023

By: Anthony O. Ives

Each aircraft design is usually optimised for a specific mission. Military aircraft have a larger variety of missions than civilian aircraft. While I generally prefer to stay away from any involvement with military projects, military aircraft can be very interesting as they use the latest technology. Some of the latest technology in the civilian world was derived from military applications, so you may learn something that you can apply for peaceful means. Civilian aircraft will also be discussed and compared with military aircraft missions.

Next to helicopters the only other aircraft that ever interested me was fighter jets in a way they still fascinate me. My fascination is probably do the high performance of these aircraft as well as the different hi-tech systems that they carry. I even thought of becoming a military pilot as I was thinking along the line that you feel ultimate freedom flying these aircraft. However, there is a number of things that put me off I have listed them below starting with the most important:

  1. Fighter jets are designed and built purely to destroy targets which may or may not involve the loss of human life. This may be justified to protect your own people but I still had a problem being involved in something that is purely designed and built to destroy. While I am not quite a pacificist being a military pilot is a big responsibility as you are making life or death decisions. Designing and building military aircraft is an even bigger responsibility as you are potentially giving someone else the authority and power to make life or death decisions possibly over which you have little control. So I just do not feel comfortable with this life or death decision making responsibility.

  2. The next reason was I do not like keeping secrets. In order to carry out military operations, operate military equipment, design and build military equipment you will be required to keep secrets often from the people closest to you including your spouse. It is as the old World War 2 American idiom says 'Lose lips sink ships' so I can see how this is necessary but I would feel I had lost part of my freedom as 'The truth will set you free' John 8:32 Ref [1], secrets are generally a big burden for most people.

  3. Vetting is the next reason again very necessary in order to be sure everyone involved is trustworthy. However I am not quite sure why this makes me feel uncomfortable because I have never had anything to hide. I think maybe it is same as my second reason it almost feels like you have lost some of freedom. If you think about it, it would be nice to live a world where you do not have to prove your identity with passports, etc it would also make life a lot simpler. Unfortunately there are certain people that exploit this sort of freedom so we all have to give it up.

  4. The last one is militaries are highly institutionalised. It is not discipline I have a problem, it is more the regmental routine system with very little freedom I have a problem with. Though like the other points this is probably necessary for the military to function correctly. Saying that this goes for any large company or organisation you sort of lose your individuality and freedom, you are essentially just a number.

So that was all just really a disclaimer while I maybe causally interested in military aircraft I am aware of their dark sides and generally prefer not to get involved with them. I also want to encourage you to think very carefully before getting involved in military projects or operations. In reality I have been told that two thirds of the aircraft industry is related to military applications. So there are plenty of other people designing and building military aircraft hopefully more will not required in the future.

Why I want to talk about military as well as civilian aircraft in this blog article is because military aircraft have a wider range of missions requiring them to be optimised for different performance parameters compared to civilian aircraft. For each military role I will try to compare with or suggest a civilian application. Soviet/Russian aircraft typically have a NATO codename associated with them which makes it easier for NATO forces to identific them, a similar practice was used during the World War 2 to identify Japanese aircraft. For the Russian NATO code names, Fighters use a word beginning with 'F' such as 'Foxhound', 'Flanker' or 'Felon', for bombers its 'B' such 'Bear' or 'Blackjack', for helicopters its 'H' such as 'Hind', 'Helo', 'Hokum' or 'Havoc' and C for military airlift aircraft (assuming C refers to cargo?) such as 'Candid', etc. Russian forces would rarely refer to their aircraft using NATO codenames for some they have their own names such as 'Swan' for Tu-160 (NATO code:Blackjack) and 'Alligator' for the Ka-52 (NATO code:Hokum).

Interceptors

Interceptors are a specific type of air-air combat aircraft which are specifically designed to reach an intruding enemy aircraft and destroy it, tyically bomber type aircraft. Interceptors are typically equiped with long range air-air weapons which can be classed as beyond visual range (BVR). A typical mission would be to get to height and location of the intruding aircraft as fast as possible, destroy it once the interceptor's weapons come into range, then evade the area. Interceptors are typically not designed for close air-air combat so generally interceptors will try to destroy their targets from as far away as possible. The Mikoyan MiG-31 (NATO code:Foxhound) is the only specific designed interceptor (that I can think of) which is currently in service. The MiG-31 is currently in service with the Russian Air Force but was originally designed for the Soviet Air Force. The Mikoyan MiG-31 is also one of the few aircraft capable of Mach 3 which is three times the speed of sound. The McDonnell F4 Phantom II was essentially designed as an interceptor and probably the last high speed fighter jet which could go at Mach 2 or twice the speed of sound in the US Air Force (USAF) and the first not to be equiped with an internal gun or cannon. At one time interceptors with BVR weapons where thought to be the future and days of close air-air combat were over but USAF experiences in Vietnam proved this was not the case see Ref [2] for more details. Interceptors are designed to perform optimally for climb rate and speed so they are the aircraft that can climb and fly the fastest. Their is really no civilian applications for interceptors but they are actually used rarely in modern combat but more to assist airliners or other aircraft in distress or that have got lost.

Air-Air Fighters

Air-Air Fighters are designed to be highly manunevorable and designed to be optimised for high turn performance so usually not as fast as interceptors. This type of performance is necessary for close air-air combat. Typical aircraft are General Dynamics F16 Fight Falcon and Sukhoi Su-35 (NATO codename:Flanker). As with interceptors there is not really a civilian application for these type of aircraft usually these aircraft perform the same role as an interceptor however aerobatic display aircraft are designed with the similar sort of performance.

Air Supremacy Fighter

Air supremacy is a term used by the USAF to suggest a state of the art fighter that is capable of defeating anything in air-air combat typical aircraft are the Boeing F15 Eagle and Lockheed Martin F22 Raptor, Ref [5]. These have combined aspects of all air-air fighters and interceptors but designed only for air-air combat. However, the Russian Air Force has the Sukhoi Su-57 (NATO Codename:Felon) which is designed to challenge aircraft like the F15, F22 and F35 but the Su-57 is not techincally a air supremacy fighter by USAF definition as it carry out ground attack as well.

Bombers

Bombers have a similar optimum design as an airliner which is designed to carry a payload a certain distance. Bombers like airliners are designed for maximum range with the exception their payload is not people or cargo but some sort of ground attack weapon. Like airliners, bombers can come in various different sizes such as light, medium and heavy. The Strategic Bomber was an important development that justified the creation of independent air forces with the ability to strategically win wars. Before the strategic bomber air forces were really just used to provide a similar role as artillery to support ground forces. It is often suggested that Germany's failure to realise the value of the strategic bomber was one possible factor that lost them the second world war, see Ref [3].

Close Air Support or Ground Attack Aircraft

Close Air Support or Interdiction aircraft are specialised bombers which can carry out air strikes on enemy forces close to friendly forces typical aircraft are the Fairchild A10 Thunderbolt and Sukhoi Su-25 (NATO code:Frogfoot). These aircraft are optimised for endurance as well as range as they may need to loiter for some time. Fast aircraft are generally not ideal for close air support, hence the argument by some defense analysts that the F35 will not be as good as the A10 at close air support, see Ref [4]. Attack helicopters are in really a form of close air support aircraft their ability to land almost anywhere and their slow speed make them ideal for role. The main disadvantage is that helicopters cannot carry as much payload as a fixed wing close air support aircraft hence why the McDonnell Dougas AV8 Harrier II and more recently Lockheed Martin F35B Lightening II are used by the US Marines Corps (USMC) for the close air support role as well. However, attack helicopters are very good at providing very close air support as they can move very slowly and easily identify exactly what they are about to shoot at. Civilian aircraft that require the same kind of optimum design are those used for search and rescue (SAR), firefighting, police operations, fishery/border patrols and agriculture operations. Some other specialised military aircraft would have a similar optimum design such as those in engaged in surveillance and anti-submarine operations.

Multi-role Fighter

Sukhoi Su-57 (NATO Code:Felon) is a highly advanced multi-role fighter used by the Russian Air Force. The Lockheed Martin F35 Lightening II is the USAF equivalent which is also designed to be a multi-role aircraft. In reality most modern combat are used to carry out a number of missions maybe with exception of the F22 which the USAF has insisted is purely for air-air combat, Ref[5]. Muli-role aircraft are an attempt to have one combat aircraft that can do a number of different missions, it reduces the need for air forces to have diffent types of aircraft. In reality modern combat aircraft rarely engage in air-air combat and are typically more used for carrying out air strikes so it does not make a lot sense to have dedicated air-air combat aircraft that will never get used. However, some defence analysts argue that one aircraft cannot perform all missions as an aircraft can only be designed to perform one mission well, Ref [4].

Helicopters and Tiltrotors

Helicopters are generally designed to hover and the main reason and advantage for using a helicopter is that it can land almost anywhere if you can use a runway you are probably better of using a fixed wing aircraft. In terms of range, endurance and speed fixed wing aircraft have higher performance than helicopters. Tiltrotors such as Boeing V-22 Osprey, Agusta Westland AW609 and Sikorsky V-280 Valor where designed to gain some of the advantages of fixed wing aircraft and helicopters however they are generally somewhere in between in terms of performance. Tiltrotors cannot give the same range, endurance and speed as a pure fixed wing aircraft they also do not hover as efficiently as helicopters. Tiltrotors also require more complicated systems than both helicopters and fixed wing aircraft, V-280 has attempted to simplfy the tilting mechanism. Earlier tiltrotors tilted the entire engine units, the V280 only tilts the rotors which reduces stresses on tilting mechanism as well as allowing use of all the doors for hoist/rope operations. The hot exhaust in hover from the earlier tiltrotors prevented hoist/rope operations near the engine units. Tiltrotors have had other undesirable effects in autoration and vortex ring with a number accidents, Ref [6]. USAF and other US militaries will probably contiunue to use tiltrotors only time will tell whether they will be adapted elsewhere.

Summary

Generally an aircraft can be optimised to provide for range, endurance, speed, turning performance or climbing performance. An aircraft can be designed to generally perform very well for one of these parameters but usually not all. Therefore an aircraft is designed to give the best performance for the mission it is intended to carry out. Helicopters are generally designed to have best performance in hover, in all other aspects fixed wing aircraft perform better hence why they are used more than helicopters. Helicopters are generally used where a mission requires access to place not accessable to fixed wing aircraft or requires a very low speed as in the case of surveillance. Hence why Igor Sikorsky said: 'If you are in trouble anywhere in the world, an airplane can fly over and drop flowers, but a helicopter can land and save your life.'

Please leave a comment on my facebook page or via email and let me know if you found this blog article useful and if you would like to see more on this topic. Most of my blog articles are on:

  1. Mathematics

  2. Helicopters

  3. VTOL UAVs (RC Helicopters)

  4. Sailing and Sailboat Design

If there is one or more of these topics that you are specifically interested in please also let me know in your comments this will help me to write blog articles that are more helpful.

References:

[1]The Holy Bible

[2] McDonnell F4 Phantom II: Spirit in the Skies (World Air Power Journal), Jon Lake, 1992, Aerospace Publishing Ltd

[3] Goring: A Biography, David John Cawdell Irving, 1989, William Morrow & Co

[4] 'Can the F-35 Replace the A-10?', Nickolai Sukharev, December 03, 2013

[5] Carlson, Maj. Gen. Bruce. "Subject: Stealth Fighters." Archived 29 August 2010 at the Wayback Machine U.S. Department of Defense Office of the Assistant Secretary of Defense (Public Affairs) News Transcript. Retrieved 28 August 2011.

[6] 'Why the V22 Osprey is Unsafe', 2003, Carlton Meyer, https://www.g2mil.com/V-22safety.htm

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