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Posts Tagged ‘design’

Balancing a fighter design

Posted by Picard578 on September 1, 2017

Introduction

Producing a balanced fighter design is a key element of an effective air force. Yet it is also very hard, as tactical capability has to be balanced against strategical capability. “The best is the enemy of good enough” holds true for fighter design as it does for everything else. Fighter design is a balance of compromises, and focusing too much on one side of design leaves gaping holes in the other side of design. Amongst modern fighters, F-22 is tactically an excellent design but is garbage when it comes to strategic capability. F-35 is tactically good for certain ground attack missions (SEAD, DEAD) but worthless for other ground attack missions (CAS) and air superiority, and also strategically worthless. On the other side of the spectrum, original Su-27 and MiG-29 designs were adequate in strategic ability, but were tactically very lacking to say at the least. The only well balanced design in existence is likely Swedish Saab Gripen, with some other designs – F-16, F-18, Tejas and Rafale – being merely adequate.

Tactical capability

Situational awareness and emissions stealth

Sensoy suit should be primarily passive. This way, fighter will be able to achieve surprise in aerial combat. Since surprise is number one issue when gaining kills, all active emissions by fighter itself – radar, radio, dana links etc. – should be avoided. Where such emissions are necessary, they should be provided to the fighter by offboard means, such as unmanned aerial vehicles (UAV) and airborne warning and control systems (AWACS). This will allow fighter to achieve surprise, and deny enemy the opportunity to use fighter’s own emissions to find and possibly even target it. Issue with this approach is that IRST has limited rangefinding ability, though its angular resolution is superior to that of the radar. Rangefinding options exist, but passive rangefinding is comparatively imprecise, while active rangefinding warns the opponent. While a degree of surprise is achieved merely by initial detection being passive, even if active rangefinding gives away fighter’s presence, this still limits missile probability of kill as the enemy has time to prepare while a targeting solution is calculated and missile launches and traverses the distance. Completely passive surveillance and targeting avoids that issue, but at the price of more limited situational awareness due to range and scan time issues. IRST also has the advantage of not being easily jammed. Midwave IRST is better for ground attack aircraft due to lower susceptibility to aerosoil, while longwave IRST is better for air superiority fighters as it is less affected by water droplets, and can see straight through thin cloud cover. IRST also allows for detection of stealth fighters at useful tactical distances, and just as importantly, allows for somewhat reliable identification of targets, thus making BVR combat possible. By using PIRATE IRST as a basis, subsonic fighters may be detected at 90-160 km, depending on the altitude and aspect. Supersonic fighters may be detected at 250-500 km distance, again depending on the altitude and aspect.

Radar may be provided either onboard, or through offboard means. If radar is provided in an integrated package, care should be taken that a quest for radar performance does not compromise other fighter’s characteristics, such as size, maintenance or flight performance. However, small fighters are limited by radar’s output and aperture size. For this reason, and due to radar giving away fighter’s presence, an integrated radar is not an ideal solution. Another possibility for an onboard radar is a radar pod. This way, radar is not limited by the size of the fighter’s nose cone, and does not have to be carried by all fighters in a squadron. Radar may also be carried by a command fighter or an AWACS, preferably both. Command fighters would be large, twin-engined, two-seat fighter aircraft with extensive sensory suite. Ideally, they would have nose, cheek and rear sensory arrays – consisting of RADAR and IRST, and possibly LIDAR – as well as standard radar, laser and missile warners, providing a 360* situational awareness. Due to their relative vulnerability, they would be kept back while providing sensory feed to other fighters. Last option is AWACS. This aircraft is even larger and more vulnerable than a command fighter, but also has even more powerful radar. Due to relatively large crew, AWACS is an ideal coordination center, but even so maximum autonomy should be provided to fighter pilots and flights. Overall, a combination of radar pods, command fighters and AWACS aircraft seems to be an ideal solution. A radarless fighter design can be seen here. Offensive fighter however would likely not be able to rely on either AWACS or ground radars, and should thus be equipped with its own onboard radars. Ideally, it would have nose, cheek and tail X-band arrays, and leading edge L-band arrays.

Fighter should also have good cockpit visibility, with bubble canopy and general nose area design optimized so as to provide good over-the-nose, over-the-side and rearward visibility. Canopy would ideally be frameless, though a separate windshield may be provided so as to protect the pilot in the case of mid-air canopy failure (e.g. accidental ejection of the canopy).

Pilot training

Pilot is the most important part of the aircraft, and thus pilot training is the most crucial for performance, including survivability. Pilot training heavily outweighs any technical concerns. In war, 10% best pilots score 60-80% of all kills. During Battle of Poland in1939., a few Polish pilots became aces in 225 mph open cockpit biplanes while fighting against 375 mph Me-109 modern monoplane fighters. Meanwhile, during 1940 Battle for France, French and British pilots did poorly despite their fighters being as good as German ones, due to using incorrect tactics. Later Battle for Britain was not lost because of fighter production, but because Germans were incapable of recovering pilot losses: while 50% of British pilots shot down were recovered safely, all German pilots were lost due to fighting over a hostile territory. Likewise, air war against Germany in late 1944 was won because Germans were not able to replace fighter pilots at adequate rate.

Training is made easier by simulators, but live training in actual aircraft is still irreplaceable. Consequently, pilot has to be able to fly regularly, and often – one hour per day or more. To fulfill this requirement, aircraft has to have several characteristics. It has to have low maintenance downtime, low operating cost and high system reliability. Peacetime availability has to be high to very high, which is achieved by having adequate ground crews as well as an excess of spare parts and fuel available. Ideally, there would be an excess number of fighter aircraft compared to pilots, for two main reasons. First, such a situation would mean that pilots are not limited in training and combat by their machines. If a fighter aircraft is not available due to damage or maintenance, pilot simply uses a spare one. Second, it would provide a pool of spare fighters to be cannibalized if spare parts are not available for whatever reason. This situation should be avoided as much as possible, but expecting it to never happen is moronic. To achieve this however, fighter aircraft has to have both low procurement cost and low operating cost, combined with high reliability. All these requirements lead to a final requirement for a small, simple fighter design. Fighter should also be single-role, as single-role aircraft and especially single-role pilots are far superior in their designed role than aircraft and pilots carrying out multiple roles.

Human-machine interface

In order to simplify both training and operation, allowing pilot to focus on tactics instead of managing the aircraft, interface has to be simple and intuitive. This can be achieved through usage of design utilizing large touch screens with as few switches and buttons as possible. Another important factor is the ability to optimize HUD/HMD symbology so as to avoid cluttering. This would ideally include the ability to quickly switch between different programmed HUD layouts, as required by the situation. Layouts themselves should be as minimalist as possible. This would reduce the amount of information forced onto the pilot by the aircraft systems, allowing him to focus on actual combat. Each pilot should be given possibility to personalize HUD and screen layouts. Information should be presented in a graphic form as much as possible, with numbers and letters being used only where absolutely necessary.

Physical stealth

Aircraft should have as low visual, IR and EM signature as possible. Visually, this means that fighter itself should be small, less than 15 meters in length and 10 meters in wingspan. It should also be painted light gray, and have as few protrusions as possible. Care should be taken to ensure that engines have as little smoke emissions as possible, regardless of the operating conditions, as smoke can increase visual detection distance by a factor of 3 to 5. As noted before, situational awareness should be provided primarily through passive means, and aircraft should have an option of IR BVRAAM.

While internal weapons carriage is not an option due to other concerns, radar cross section should also be minimized. There are several approaches which can minimize RCS on conventional fighters. First, airframe should be optimized so that there is a minimum number of unnecessary protrusions – everything should be flush with the airframe. Refueling probe can be internal, or else aircraft could use boom refuelling so that fighter itself has no protrusions. Missiles should be carried conformally, with ideally two wingtip stations and two to four body stations allowing for conformal carriage. This way, missile rail as well as a gap between the missile and aircraft’s airframe would be eliminated. Missiles themselves should have retractable wings, which would eliminate scattering from the missiles as well as the possibility of missile wings acting as corner reflectors. Aircraft’s wings and canards should both be canted – downwards for wings, upwards for canards – not only to achieve adequate separation for aerodynamic purposes, but also to avoid forming a corner reflector with vertical stabilizer. This approach would also prevent missile winglets, if conventional missiles are carried on wingtip stations, from forming a corner reflector with coplanar radar source.

In IR spectrum, aircraft should be capable of supercruise so as to minimize the need for afterburner. This should be reinforced by having high thrust-to-weight ratio, even on dry thrust. Consequently, engine should be capable of achieving high percentage of total thrust without afterburner, pointing to a low bypass ratio, possibly even a turbojet. Engine woud have dual nozzles, with outer nozzle hiding the hotter inner nozzle as well as the hottest portion of afterburner. Additional cooling channel may also be provided, coupled with the outer nozzle. This cooling channel would utilize cool air from the boundary section layer, instead of the hotter air provided by the engine itself. Aircraft should be aerodynamically well designed and small, so as to minimize the engine emissions necessary. Air exhaust for the electronics cooling would lead into the engine air duct, so the hot air would be ejected with already superheated engine exhaust.

For a multirole fighter, acoustic stealth is also important. This means limiting the aircraft size, weight and thus engine power. Aerodynamic design should also be with as few protrusions as possible in order to eliminate irregularities in the air flow.

Weapons

Weapons should allow both quick reaction during close combat and silent kills during long-range combat. As a result, normally used weapons would be 30 mm revolver gun, short-range IR missile, medium-range IR and dual mode RF/anti-radiation missiles, and long-range dual mode RF/anti-radiation missiles. Missile ranges should be in brackets of 25, 50, 100, 150, 300 and 500 kilometers. Going with noted, IR missile option should be present for missile ranges of 25, 50 and 100 kilometers, with RF/AR missiles being available for ranges of 50 kilometers and greater. Usage of IR missiles would result in improved reliability as well as reduced vulnerability to countermeasures.

Fighter should have at least one onboard kill in adverse conditions. Assumed probability of kill used here are 0,31 for revolver cannon, 0,26 for rotary gun, 0,15 for IR WVRAAM, 0,11 for IR BVRAAM and 0,07 for RF BVRAAM against uncooperative targets. Against cooperative targets, Pk values assumed will be 1 for gun, 0,73 for IR WVRAAM, 0,59 for IR BVRAAM and 0,46 for RF BVRAAM (pilot training and situational awareness are the primary determinants of aircraft’s ability to avoid the missile). With four conformal stations – two wingtip and two body stations – and four wing stations being assumed, fighter should be able to carry eight missiles, plus 6 gun bursts to allow for two kills. In “stealth” configuration, with two IR WVRAAM and two IR BVRAAM, total number of kills is 2,38 against uncooperative targets and 8,64 against cooperative targets. If normal configuration is assumed to be two IR WVRAAM, two IR BVRAAM and four RF BVRAAM, total number of kills should be 2,66 against uncooperative targets and 10,48 against cooperative targets. BVR missiles overall have limited effectiveness against fighter aircraft, and are mostly useful against large targets such as AWACS or transport aircraft. They are useful when pursuing a retreating target due to longer range, and can be used to force the enemy into unfavourable situation for the merge. It should also be noted that the missile effectiveness noted here is for visual range only; at BVR, BVRAAM Pk is halved compared to the values noted.

In order to maximize kill probability at beyond visual range, BVRAAM should be of a ramjet design, so as to maintain thrust during the terminal phase. Long-range BVRAAMs could combine ramjet primary missile with solid-fuel rocket secondary stage, coasting in a ballistic path until close enough to target. Unless this is done, there is no chance of a BVR missile hitting an aware target outside the visual range, as it will lack energy and maneuvering capacity to do so – probabilities of kill noted earlier are all achieved within visual range. Probability of kill at altitude is low even with maneuvering ability intact. A missile that pulls 40 g at sea level will only pull 13 g at 10.000 meters and 2,85 g at 20.000 meters, unless 40 g is a structural limit. AIM-9 for example can pull 40 g at SL and at 10.000 ft, and 35 g at 20.000 ft. At 40.000 ft, AIM-9 should be able to pull no more than 13 g. Meanwhile, F-16 for example can sustain 9 g at up to 10.000 ft, and Rafale can sustain 9 g at 40.000 ft. In terms of more relevant (for missile evasion) instantaneous turn performance, F-16 can pull 9 g at altitudes up to 35.000 ft; at 40.000 ft, maximum limit is 7 g, and 5 g for most of the envelope. Missile on the other hand needs at least five times the g performance of a fighter aircraft to achieve a hit, possibly even more (lowering the speed of a missile does not improve turn rate as missiles typically operate well below their corner speed). As it can be seen, even AIM-9 is very unlikely to hit a maneuvering F-16 at 20.000 ft, and basically impossible to hit it at 40.000 ft. As a consequence, fighter aircraft should carry a large number of missiles and be able to fire them in pre-programmed salvos if goal is a BVR engagement. If fighter is optimized for visual-range combat, it should be able to carry missiles conformally, and fire them even from high off-bore angles, as well as to maintain missile lock during rapid maneuvers so that pilot can fire off a missile immediately upon achieving a desired position.

Gun is most likely to be used against large, undefended targets such as AWACS or transport arircraft in order to avoid wasting missiles. Other scenario is usage against targets that are too fleeting to achieve a missile lock, or are within missile’s minimum engagement distance. As a result, premium is placed on damage output in quick bursts. Firing opportunities in a dogfight are brief, and length of a burst is never longer than 1,5 seconds. This means that gun has to pump out as much damage as quickly as possible, which in turn requires quick acceleration and high HE-I content of the shell. Overall, the best choice is a high-calibre (30 mm) revolver cannon.

Kinematic performance

Aircraft should be capable of supercruise, so as to minimize the infrared signature while supersonic, as well as extending the time it can spend at supersonic speeds. This would allow the pilot to surprise the enemy from the rear, and avoid getting surprised himself. It would also allow it to dictate the terms of the engagement, avoiding the unfavourable engagements. Supercruise speed goal should be at least Mach 1,5 with six conformal missiles and no external fuel tanks. Fighter should be able to spend at least 20 minutes at that speed in the combat zone. Combat radius calculations should include the supercruise as well as combat. For defensive purposes, fighter should be assumed to operate without external fuel tanks, while in offensive purposes normal load would be six missiles and two to four external fuel tanks. Therefore, 300-400 km combat radius with 20 minute supercruise on internal fuel would be acceptable performance. This will likely lead to fuel fraction of 0,35-0,45, depending on the aircraft performance, aerodynamics, engines and size. For a dedicated offensive design, target combat radius would be 500-800 km with 20 minute supercruise on internal fuel.

Fighter should have 9 g turn capability in both instantaneous and sustained turn. If possible, 11 g instantaneous turn capability should be pursued as normal performance, with 13 g in override. Roll onset should be very rapid in order to allow fast transients, both in level flight and during the turn (at angle of attack). This is important for both dogfight and missile evasion purposes, as missile guidance lags behind an aircraft. Climb capability should be at least 300 m/s when clean at sea level, >350 m/s if possible. Ideally, turn rate would be above 30 deg/s instantaneous, 24 deg/s sustained and 300 deg/s roll rate. Fighter should be able to both gain and lose speed quickly, to allow outmaneuvering the opponent in a dogfight, as well as missile evasion. For this, moderate-to-high sweep tailless delta is a best choice. Engine should be turbojet in order to allow for quick changes in fan rotation rate and thus engine output – larger diameter of turbofan engine leads to comparatively more sluggish response. Just as importantly, turbojet engine should be capable of achieving higher thrust-to-weight ratio, especially at dry thrust. This would reduce the need for afterburner, leading to improved persistence even though fuel consumption at same engine setting will likely increase. Fighter’s combat weight should be low in order to reduce inerta and allow quick transients that are key to winning an air engagement. Reduction of roll inertia specifically can be achieved through single-engined configuration, low wing span, and locating heaviest ammunitions as well as most fuel as close to the aircraft centre as possible. Offensive design however would do well with two engines so as to ensure backup in the case of a failure or a hit by a SAM or AAA, in order to get the pilot back to the friendly territory.

Strategic capability

Ground survivability

Despite the name “air craft”, modern aircraft – especially fighter jets – are less air craft and more air hoppers. Fighter aircraft in particular spend only a portion of time in the air – no more than a third, and many far less. Most of the time is spent on the ground, undergoing maintenance, repair, refit and refuelling. As a result, ground survivabilty is a crucial aspect of aircraft survivability. To achieve this, fighter should be capable of operating from road bases. Minimum takeoff and landing distances should be less than 500 and 400 meters, respectively. Wingspan should also be less than 8,75 meters for a defensive design. A dedicated offensive fighter would likely have to have larger wingspan as well as longer takeoff and landing distances, thus placing emphasis on dirt strip performance. Logistics requirements should also be low, in particular in terms of spare parts and fuel. Low fuel usage means that fighter itself should be relatively small. Easy repairability in field would mean usage of aluminium alloys instead of composites, though decision should be made after taking into account impact on aircraft performance.

Numbers in the air

In order to carry out all the task, fighter force has to be able to launch enough sorties – best weapon in the world is useless if it cannot cover all necessary areas, and planet is a large place. Larger number of aircraft than the enemy’s also allows for tactical (as well as operational and strategic) flexibility, allowing one portion of the force to engage the defending fighters while remainder goes after crucial targets that had been left without cover. This means that fighter’s procurement and especially operating cost should be low, as well as its logistics requirements. Again, this leads to requirement for a small, easily maintained fighter aircraft.

Ease of maintenance

Aircraft should have a simple and maintenance-friendly design. Number of individual components should be kept to minimum, and all important components should be placed so as to allow easy access from the outside. Components themselves should be grouped into easily replaceable modules – which themselves should be repairable in the field. Minimum number of parts should be used in construction.

Logistical footprint

Logistical support is the most vulnerable element of any force. If supply chain is disrupted, the entire combat force is quickly rendered impotent. For this reason, minimizing logistical footprint for any given force is mandatory. Chain itself consists of several main elements. First one is the producer, albeit it is not always relevant in the war. Items produced in the factory are stored in the depots at home, and then shipped to military bases – which, in the case of expeditionary military forces such as the US military, are often overseas, requiring shipping over large distances. Once transferred over the sea, they are unloaded at port, and either stored there or transferred to inland supply depots. From there, items are transferred to military units and bases that require them (not all bases are large enough to function as supply depots on their own). In a specific case of fighter aircraft, the chain consists of manufacturers (aircraft parts, weapons, fuel), supply depots and air bases at home, supply depots / large air bases abroad, and forward operating bases (e.g. road bases).

Supply footprint of a fighter unit is not limited to fighter aircraft themselves, but also to any and all support elements – AWACS, tankers, air bases themselves, ground forces providing security for said air bases. Most modern fighter aircraft are large and complex machines, requiring dedicated air bases for operation. Such fighters themselves already have high logistical footprint due to complex maintenance and high fuel usage. Footprint is only increased by the equally complex tools required for maintenance – especially when it comes to stealth fighters such as the F-35. Further, air bases themselves require constant maintenance. Not only tools for fighter maintenance have to be maintained, but also the aircraft runway (FOD walks!), hangars, living quarters for pilots and ground crews. Dedicated air bases themselves are very vulnerable to attacks, and are also very lucrative targets. This means that they require security in the form of extensive missile and air defense systems, as well as powerful ground forces for defense against ground assaults. These forces require massive supplies as well, which typically means usage of large transport aircraft. Due to importance, vulnerability and obviousness of these air bases, they are typically situated far behind the front line. As a result, fighter aircraft have to traverse long distances to the combat zone, requiring tanker support to reach their targets, further increasing their logistics footprint.

For this reason, fighter aircraft has to be able to operate from FOBs (Forward Operating Bases). That way, fighters would be close to friendly ground troops, increasing the time spent in the combat zone, and thus reducing the size of the force necessary for the effect. These bases should be very small, holding no more than a few fighters each (ideally, a pair or a flight of four). Fighters and everything else present would be camouflaged with the use of multispectral camouflage nets, making finding them more difficult. Crews would live in tents, which would be camouflaged the same way. In the case some are discovered and attacked, wide dispersal of forces achieved in this way would limit damage compared to attack agaist conventional air bases. Due to necessarily small size of such bases, any fighters used from there have to have small logistics footprint, and ground forces present would also be small. All of this would result in very small logistics footprint of each base, as well as reduced footprint of the force as a whole. Small logistics footprint required would necessarily mean a light (5-7 metric tons empty) single-engined fighter design, however measures could be taken to reduce footprint of larger aircraft as well – specifically, dirt strip / open field capability.

Conclusion

As it can be seen, fighter design may change in major ways depending on its role and expected environment. However, most basic things are common for all fighters, and it would be a mistake to ignore them.

Further reading

https://defenseissues.net/2014/08/02/air-superiority-fighter-proposal-6/

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Posted in weapons | Tagged: , , , , | 54 Comments »

A-10 Thunderbolt survivability design

Posted by Picard578 on December 11, 2016

When the A-10 was about to be introduced, USAF leadership used the exact same arguments to prevent that as they are using now in an effort to kill it. They saw merely a clunker that flew at 300 knots or less, an anachronistic dud unfit to operate on the modern battlefield where it was to kill Russian tanks. In fact, the A-10 would never had been introduced if the USAF was not engaged in the budgetary battle against the US Army. Army was about to introduce the new attack helicopter, the Cheyenne. Cheyenne was a compound helicopter, designed to overcome the inability of normal helicopters to achieve higher speeds when necessary, and its high price would see financial resources redirected away from the US Air Force and into the Army’s purse. USAF would have none of it, and it decided to finally take responsibility for the close air support mission it was supposed to do anyway, and so introduced the A-10. Technical requirements were outlined mainly by Pierre Sprey after talks with surviving US and German pilots who carried out close air support in World War II and the Vietnam war, while the overall effort was directed by the Colonel Avery Kay. More heavily armed, survivable and less expensive, A-10 easily killed off the Cheyenne, and the USAF never placed any orders beyond the first batch. In fact, the A-10 was the first and the last US fighter designed for close air support. Read the rest of this entry »

Posted in weapons | Tagged: , , , , , , | 29 Comments »

Aircraft carrier proposal 3

Posted by Picard578 on September 6, 2014

Aircraft used

 

Aircraft used will be an air superiority fighter (FLX), CAS fighter (AX) and observation aircraft (OLX), plus transport aircraft (C-2). This will allow it to be useful for carrier’s primary tasks: defending fleet from an attack by enemy ground-based aircraft, as well as supporting amphibious landings and providing close air support for ground troops. Read the rest of this entry »

Posted in proposals | Tagged: , , , | 34 Comments »

Close Air Support fighter proposal

Posted by Picard578 on November 2, 2013

Historical lessons

While Gullio Douhet’s theory that bombardment of the enemy heartland can win the war has dominated USAF (USAAF during WWII) procurement ever since its formation has been thoroughly discredited (more about that in another article), Western air forces still procure far too many strategic bombers and deep strike fighters, while procuring insufficient number of close air support fighters; this often results in a situation where all ground attack aircraft, regardless of their suitability for the role, have to be used for close air support.

But Close Air Support is a very hard mission with strict requirements, which aircraft designed for other missions (“multirole” fighters, most tactical bombers with exception of aircraft designed specifically for CAS, any strategic bombers) do not meet. It is therefore paramount for these requirements to be well understood if CAS fighter is to be effective.

First concern is that crew of a CAS aircraft has to think of themselves and their mission as a ground soldiers, and understand infantry, armor and/or mechanized tactics. From this follows the requirement for CAS squadrons to be assigned to specific battallions and be colocated with them, but also a requirement for pilots to study ground combat – tactics, visual specifics of different vehicles. All of this means that “multirole” pilots are psychologically incapable of carrying out effective CAS, and that complex “multirole” aircraft are similarly incapable of satisfying basing requirements. In exercises, observers should sometimes swap places with ground troops and participate in them as infantrymen or otherwise members of ground units they are assigned to. Whenever CAS crews train, it should be with the unit they are assigned to, and observers should eventually reach the level where they will be capable of taking command of ground units.

Second problem is that Close Air Support is a very demanding mission. It is carried out at low altitude, so pilot will have a lot of trouble avoiding anti-air fire and avoiding to fly into the ground. This means that there should be a separate observer who will also command the aircraft, freeing up pilot to focus on flying.

Third concern is a coordination with both supported unit and the artillery. This means that ground unit should have attached ground FAC. Also, CAS aircraft should be survivable enough so as to be able to fly slow and low enough to identify targets.

It should also be noted that Close Air Support, while extremely useful, is an emergency procedure. Read the rest of this entry »

Posted in proposals | Tagged: , , , , , | 42 Comments »

F-35 and its troubles

Posted by Picard578 on May 11, 2013

While people term F-35 a “multirole” aircraft, and Lockheed Martin stated that it is second-best air superiority fighter in the world, F-35 is primarly a dedicated ground attack aircraft. This can be seen relatively easily, as there are different requirements for fighters and for ground attack aircraft.

Primary requirement for ground attack aircraft is ability to fly low and fast. This means that gust sensitivity should be minimal, which is done by high wing loading; only exception are close air support aircraft, which have to be able to fly low and slow, and be agile at low speeds. Air superiority aircraft, on the other hand, has to be able to turn while maintaining energy, which is achieved through having low wing loading, low drag and high thrust to weight ratio.

F-35s EOTS IR sensor (not to be confused with EO DAS which is defense system) can only detect targets right in front of, and below, aircraft.

Eots-Angles

Wavelengths used by it are also optimised for detecting ground targets.

Even F-35s name says it all: “strike fighter”. Unlike multirole fighters, which are designed to operate primarly in air superiority role but can also carry out ground and (sometimes) maritime strike missions, strike fighter is designed to operate primarly in strike role, with air-to-air capability being secondary and usually limited to self-defense (even A-10 can carry Sidewinders for self-protection purposes).

At 50% fuel, thrust-to-weight ratio of all three fighters is below that of modern fighter aircraft at air-to-air configuration takeoff weight, with exception of Saab Gripen. For both F-35A and F-35B, wing loading at 50% fuel is above 400 kg per square meter, with F-35C achieving barely acceptable 340 kilos per square meter. While there is a degree of wing-body blending, amound of body lift is not comparable to air superiority aircraft like F-16, Gripen or Rafale. STOVL requirement also resulted in stubby, fat body, making F-35 a drag queen, especially when compared to clean F-16 – and for all three aircraft listed, clean configuration includes 2 AAM, either BVR or WVR, whereas Typhoon carries 4 BVR AAM in clean configuration. Result is that F-35 has rather sluggish acceleration, and looses energy quickly.

Its cockpit visibility is also good only to front, sides and above aircraft – and in these areas, it is still limited by bow canopy frame. Rearward visibility is nonexistent, thanks to STOVL requirements of B variant – and when pilot brought up that flaw, general Bogdan stated that he can always “put pilot in cargo aircraft where he won’t have to worry about getting gunned down”. Its high-tech HMD, counted at to adress problems of limited cockpit view, also experienced problems, making it possible that information to F-35s pilots will be limited to only what they can see directly through canopy – which is not much – and what can de displayed from sensors on screens within cockpit. This means that problems with canopy bow and ejection seat headrest impeding visibility might get F-35 gunned down in visual combat.

F-35 is also seriously flammable – fuel literally surrounds the engine, and fire protection measures have long since been deleted from the design in order to make it lighter. As result, hits from any kind of weapon which can penetrate its skin – basically anything from 20 mm cannon and above – will turn it into fireball.

Due to everything described above, it has to rely on stealth to survive. But stealth aircraft since SR-71 have been routinely detected by radars and IR sensors during and after Cold War; USSR luckily never chose to shoot any US aircraft, while Iraq did not have capability to do so, even if indications exist that Iraqis did detect F-117. But Serbs easily solved the VHF radar’s problem with low resolution, using it to guide IR SAM close enough to F-117 for missile to acquire and engage the target. Result are two F-117s taken out of action during Kosovo war, one shot down and one mission-killed.

Radar-based BVR combat has never been reliable either. Radar-guided missiles never achieved Pk of over 8% against capable opponent, and this is unlikely to improve, despite all USAFs self-deluding exercises where F-22s BVR missiles are assigned probabilities of kill of 90%. Even this “capable” should be taken with bit of salt, as it refers to North Vietnamese – but at very least, and unlike Iraqis, they did try to evade the missiles.

In fact, by using Air Power Australia report and fixing it with calculable data, it is possible to calculate likely BVR missile Pk against modern, 12-g capable fighter. As g forces pulled in tracking turn are square of speed difference, it can be calculated how much of forces required can modern missiles achieve. AIM-120 travels at Mach 4, and can pull 30 g within its NEZ, yet it would need 768 Gs to reliably hit a modern fighter which is maneuvering at corner speed of Mach 0,5, or 237 Gs if target is still at standard cruise speed of Mach 0,9. This results in Pk between 3 and 13% against fighter aircraft with no ECM, which fits perfectly with 8% Pk demonstrated against (mostly) maneuvering aircraft without ECM to date. If fighter is maneuvering at corner speed, but is still limited to 9 g by FCS (is not in override), BVR missile Pk is 5,2%. Thus, we have following kill-chain against modern fighter aircraft in g override (12 g capable) at M 0,5 (most likely scenario, as RWR will have warned pilot of radar lock):

Action – likelyhood of failure – hit probability

  1. Active missile confirmed on launch rail — 0.1% — 0,999

  2. Search and track radar jammed – 5% — 0,949

  3. Launch or missile failure – 5% — 0,902

  4. Guidance link jammed – 3% — 0,875

  5. Seeker head jammed or diverted — 30% — 0,612

  6. Chaff or decoys seduce the seeker — 5% — 0,581

  7. Seeker chooses towed decoy — 50% — 0,29

  8. Aircraft out-maneuvers missile — 97% — 0,00873

  9. Fuse or warhead failure — 2% — 0,00856

Total: 0,86%

Against 9 g capable fighter aircraft, it goes this way:

  1. Active missile confirmed on launch rail — 0.1%
  2. Search and track radar jammed – 5%
  3. Launch or missile failure – 5%
  4. Guidance link jammed – 3%
  5. Seeker head jammed or diverted — 30%
  6. Chaff or decoys seduce the seeker — 5%
  7. Seeker chooses towed decoy — 50% — 0,291
  8. Aircraft out-maneuvers missile — 94,8% — 0,015
  9. Fuse or warhead failure — 2% — 0,0146

Total: 1,46%

This can be compared to 0,36% probability of kill shown by modern SAMs against capable opponent (with 2 hits being a non-maneuvering VLO light bombers at low altitude and with no ECM; if only actual fighters are counted, probability of kill is 0,12%, as 1 F-16 was shot down out of 842 launches).

In WVR combat, if missile travels at Mach 3 and fighter aircraft travels at Mach 0,5 (corner speed of many modern fighters) and can pull 12 g maneuvers, missile needs to pull 432 g to hit fighter aircraft. This gives a Pk of 14% for WVR missiles, as even IRIS-T can “only” pull 60 gs. Against targets limited to 9 g, it has to pull 324 g, for Pk of 18,5%.

As such, for visual-range missiles, against aircraft maneuvering at corner speed, calculation goes this way:

  1. Active missile confirmed or on launch rail – 0,001 – 0,999
  2. Launch or missile failure – 0,03 – 0,969
  3. DIRCM effective – 0,00 (rarely fitted to fighters)
  4. Flare or decoys seduce the seeker – 0,05 – 0,921
  5. Aircraft out-maneuvers the missile – 0,86 – 0,13
  6. Fuse or warhead failure – 0,1 – 0,12

Total Pk: 12%

Against fighter aircraft limited to 9 g it goes this way:

  1. Active missile confirmed or on launch rail – 0,001 – 0,999
  2. Launch or missile failure – 0,03 – 0,969
  3. DIRCM effective – 0,00 (rarely fitted to fighters)
  4. Flare or decoys seduce the seeker – 0,05 – 0,92
  5. Aircraft out-maneuvers the missile – 0,81 – 0,17
  6. Fuse or warhead failure – 0,1 – 0,157

Total Pk: 15,7%

As such, BVR missiles will have Pk of 0,86% – 1,46%, and WVR missiles will have Pk of 12% – 15,7%. As F-35 can carry 4 missiles, combined Pk will be 3,44% – 5,84% for BVR missiles, or 48% – 62,8% for WVR missiles. Because F-35 is very expensive and maintenance-intensive, it will find itself outnumbered, and forced to engage opponents with gun. This will mean F-35s loss against most fighter aircraft, as it is performance-limited: only one version can regularly pull 9 g maneuvers, and other two are limited to 7 and 7,5 g, respectively – which also means that opponent’s IR missiles will have higher Pk against them (~20%) than other way around. They can’t run either, as maximum speed when clean is Mach 1,6 – theoretically, as current aircraft are unable to go past Mach 0,9. While all three versions likely have ultimate load limit of 13,5 g, it is unknown wether F-35B and C will be allowed to go into g override to same limit as F-35A.

F-35s technology, once thought to be best of the best, is now outdated. Its IRST is no better than European counterparts, and is actually worse for air-to-air work as it is designed – and uses wavelengths suited for – air-to-ground work; and by the time F-35 enters service, Eurocanards will have AESA radars.

As a ground attack aircraft, it is only somewhat better. It can carry only two 900-kg bombs in its bomb bays, making it a rather average bomber. It is unable to carry out close air support, as it is too vulnerable to get low enough to engage tactical targets, too fast to put weapons precisely on target even if it does come low, and too fuel-thirsty to loiter over ground troops in need of air cover.

In March 2013, F-35A was forbidden from doing following things:

  • descent rates of more than 30 meters per second
  • airspeed above Mach 0,9 (compare to advertised Mach 1,6)
  • angle of attack beyond -5 and +18 degrees (compare to advertised +50 degrees)
  • maneuvers beyond -1 and +5 g (compare to advertised 9 g for A version)
  • takeoffs or landings in formation
  • flying at night or in bad weather
  • using real or simulated weapons
  • rapid stick or rudder movements
  • air-to-air or air-to-ground tracking maneuvers
  • refuelling in the air
  • flying within 40 kilometers from lightning
  • use of electronic countermeasures
  • use of anti-jamming, secure communications or datalinks
  • electro-optical targeting
  • using DAS to detect targets or threats
  • using IFF interrogator
  • using HMD as “primary reference”
  • use of air-to-air or air-to-ground radar modes for electronic attack, sea search, ground-moving targets or close-in air combat modes.

It also had quite a list of other problems:

  • liable to explode if struck with lightning
  • F-135 jet engine exceeds weight capacity of traditional replenishment systems and generates more heat than previous engines
  • extensive damage will require returning aircraft to factory for repairs
  • fuel dump subsystem poses fire hazard
  • survivability issues (rumored to be about stealth)
  • airframe unlikely to last through required lifespan
  • using the afterburner damages the aircraft
  • poor radar performance

But this is hardly end of F-35s troubles list. Performance shortfalls are compounded by development problems: at one point, Lockheed Martin had to cannibalize LRIP production line for spares so prototypes can continue with testing.

F-35s costs are understated. Sometimes-heard 59 and 79 million USD values are those of early days of the programme, specifically from 2002. But even without inflation, costs have doubled by 2012, with flyaway cost being 197 million USD for F-35A, 237,7 million USD for F-35B and 236,8 million USD for F-35C. And these are unlikely to get any lower than they are for very simple reason: modern fighter aircraft are complex, and for them learning curve barely exists. And what of learning curve does exist has already been largely absorbed by reduction in cost which lowered F-35As unit flyaway cost from 207 to 197 million USD. One of reasons is that fighter aircraft get continuous upgrades which do not allow production to stabilize and invest in truly effective cost reduction measures. F-22s unit flyaway costs went backwards late in production: whereas flyaway cost mid-production was 200 million USD, last aircraft produced cost 250 million USD flyaway. Same happened with F-14, F-15 and F-16, due to increased complexity of new technology put in to make them “more capable”; F-16A would, today, cost 30 million USD, but F-16C costs 70 million USD.

F-35 is also very unreliable, which means that pilots won’t be able to fly it as often as required, and it is not meeting reliability growth targets. One in seven training sorties in late 2012 resulted in mission aborts. By late 2012, F-35 was barely achieving one sortie every 3 days. It had 4 flight hours between critical failures, and by 2013 mean elapsed time for engine removal and installation was 52 hours (system treshold being 120 minutes). Flights were also aborted due to battery problems whenever temperature dropped below 15 degrees Celzius, making F-35 utterly unsuitable to Canada, Great Britain or Scandinavian countries.

I have already mentioned HMD problems. These include misaligned horizons; inoperative or flickering displays; double, unfocused, jittery, washed-out and/or latent images. Due to all that confusion, HMD more hurts situational awareness than it helps – and F-35, due to STOVL requirement for Marine version, has nil rearward visibility.

While F-35 has met 7 out of 10 objectives, several objectives – like “begun lab testing” – were impossible to fail. But these do not show how well – or bad – programme is progressing. And in the end, it cannot be expected that dedicated strike aircraft can perform well in air superiority role; role which, despite wishful thinking by weapons designers, is still visual-range unless enemy is outmatched in every way imaginable. But if it is, F-15A and Tornado ADV are perfectly capable of handling him; there is no need for stealth fighters; and if it isn’t, F-35, with its disastrous visual-range performance, cannot be anything more than cannon fodder, soaking up enemy missiles so more capable fighters – be it F-22, F-15 or F-16 – can take out enemy aircraft without heavy losses. But F-35 is too expensive for that, which means that USAF will be in trouble as soon as F-16 is replaced by F-35.

Pig-that-ate-the-Pentagon.Lockheed-Martin flying-pig-325x275

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Aircraft carrier proposal

Posted by Picard578 on March 9, 2013

Aircraft carrier has to be able to do following things:

a) carry as many aircraft as possible

b) launch them as quickly as possible

c) recover them as quickly as possible

d) have as many aircraft on deck as possible

 

While ski ramp is simpler, more reliable, and is safer than catapult-assisted takeoff, it puts heavy limits on payload carried. While two catapults can launch two aircraft in the air nearly simultaneously, there isn’t much difference in long-term launch rate. Thus ramp-equipped carrier is better for fleet defense, while catapult-equipped one is better for attack.

 

Both Navalised Typhoon and Rafale M are able to take off from ramp-equipped carrier with no catapult assistance. Rafale version will also carry E-2 Hawkeye AWACS, and A-262 Panther multipurpose helicopter.

 

Carrier would have four elevators, so that aircraft can be brought on deck as fast as possible. Bridge and Air Control Tower will be on opposite sides of the carrier, so there is no need to compensate for their weight, as they cancel each other out.

 

I have also decided to propose two possible sizes. First, smaller carrier will be 271,5 meters long and 46,4 meters wide (not counting superstructure). It will carry 21 Rafale and 2 Panthers on flight deck, and either 30 Rafales and 6 Panthers or 41 Rafale and 4 Panthers in hangar. Total will thus be 51 – 62 Rafales and 6 – 8 Panthers.

 

layout_carrier_small_EU

 

Second, larger carrier, will be 362 meters long at 69 meters wide, not countring superstructure. It will carry 31 Rafales, 3 Hawkeyes and 4 Panthers on flight deck, and either 35 Rafale, 2 Hawkeye and 10 Panther or 74 Rafale, 5 Hawkeye and 11 Panther in hangar. Thus, total will be 66 – 105 Rafales, 5 – 8 Hawkeyes, and 14 – 15 Panthers.

layout_carrier_large_EU

 

I personally prefer smaller carriers due to smaller number of eggs in one basket, and better handling in closed seas. While smaller EU carrier cannot launch AWACS, it can rely on AWACS from land bases, or use fighters for reconnaissance. They would also be used to escort larger carriers.

 

 

 

For United States, F/A-18C Hornet with IRST and DRFM jammer, EA-18G Growler, E-2 Hawkeye, C-2 Greyhound and SH-60 seahawk will be used. However, these have to use catapults for launch.

 

Carrier dimensions would remain same as EU carriers, but fighter compliment would differ. Small carrier would have 26 F-18s, 1 Hawkeye and 2 Seahawks on flight deck and either 29 F-18s, 3 seahawks and 2 Hawkeyes or 27 F-18s, 5 Seahawks and 2 Hawkeyes in hangar. Total would thus be 55 F-18s, 3 Hawkeyes and 5 Seahawks, or 53 F-18s, 3 Hawkeyes and 7 Seahawks.

layout_carrier_small_US

Large carrier would have 31 F-18, 3 Hawkeyes and 3 Seahawks on flight deck and either 40 F-18s, 2 Hawkeyes and 10 Seahawks or 65 F-18s, 8 Hawkeyes and 20 Seahawks in hangar. Thus, total would be 71 – 96 F-18s, 5 – 11 Hawkeyes and 13 – 23 Seahawks.

layout_carrier_large_US

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Saab Gripen analysis

Posted by Picard578 on February 16, 2013

Program history

SAAB Gripen is a result of relaxed-stability fighter rush initiated by (at the time) revolutionary F-16 fighter aircraft. It is not surprising that SAAB opted for delta-canard layout they themselves pioneered in 1960s, but other options were also evaluated (and rejected). This was influenced by testing programme of Viggen in late seventies, which verified benign high AoA characteristics of the layout. To Sweden, choice of small, cheap but highly capable fighter aircraft was obvious.

In 1979, after cancellation of too expensive B3LA project (a development of subsonic trainer and light attack aircraft), Swedish Air Force carried a reexamination of its requirements. Conclusion was that only affordable option was development of multirole aircraft capable of carrying out air superiority, ground attack and reconnaissance missions. Thus the JAS programme was born, drawing name from specified requirements (Jakt – fighter, Attack – attack, Spaning – reconnaissance).

In March 1980, Government endorsed the plan, but insisted that foreign contractors should be allowed to bid for the contract. As a response, Swedish (state-owned) aircraft industry formed a JAS Industry Group, comprising Saab-Scania, Volvo-Flygmotor, Ericsson Radio Systems and FFV to manage the bid by Swedish industry. Formal proposals were requested in 1981, and JAS IG submitted their proposal on 1 June 1981. After evaluation of proposals, it was decided to go forward with JAS proposal. On 30 June 1982, a fixed-price proposal was signed between the FMV and IG JAS for 5 prototypes and 30 JAS-39A aircraft. Following month, name Gripen was selected for the aircraft.

Ericsson was tasked with developing multi-mode radar, while FFV developed navigation and attack systems.

Mock-up of the final design was unveilled in early 1986. However, development of Flight Control System caused delays in final assembly of the aircraft, with first Gripen rolling out of assembly on 26 April 1987, after 7 years of development. First flight was achieved on 9 December 1988, but after its sixth flight, on 2 February 1989, aircraft veered off the runway and carwheeled. Following that, FCS was fixed, and on 4 May 1990, JAS-39-2 flew with new software. Fifth and final prototype flew on 23 October 1991. Testing showed drag to be 10% lower than predicted, and airfield performance was also better than specifications. In June 1992, contract for second batch of aircraft was approved.

On 4 March 1993, first production Gripen (JAS-39-101) made its flight, with second production aircraft delivered for service testing on 8 June 1993. It soon crashed during air display over Stockholm due to the pilot loosing control and having to eject. Following the accident, further flight testing was suspended until FCS was revised. Revisions included changes to canard deflection angles in combat mode. Testing continued on 29 December 1993.

One JAS-39A was converted from production line to serve as prototype for twin-seated trainer, JAS-39B. It features 65,5 cm fuselage stretch, and rear cockpit that is, except for lack of HUD, identical to the front one.

On 12 June 1995, SAAB and British Aerospace announced joint development of export variant. In 2001, joint venture was registered in Sweden as Gripen International. As Gripen was designed solely for Sweden’s needs, Export Baseline Standard was developed, resulting in C and D variant of the aircraft. Soon, Swedish Air Force decided to also acquire the new version, with last 20 aircraft of Batch 2 and 30 aircraft of Batch 3 conforming to EBS specification.

EBS featured retractable inflight refuelling probe on the port air intake, full-color English-language cockpit displays in Imperial units, new computers, night-vision compatible cockpit lightning, FLIR and reconnaissance pods, more powerful air conditioning system, OBOGS and stronger wings with NATO standard pylons.

In December 2004, BAe sold large portion of its stake in Gripen International to Saab, finally selling remaining 10% of their stake to Saab in June 2011. On 26 April 2007, Norway signed an agreement on common development of aircraft, with agreement between Saab and Thales Norway following in June, concerning development of communications systems. In June 2007, NATO Link 16 was added to datalink systems of Gripens in Swedish service.

On 23 April 2008, Gripen Demo (requested in 2007) was presented, serving as demonstrator for Gripen NG. On 27 May 2008 it had maiden flight, and demonstrated supercruise ability on 21 January 2008, flying at Mach 1,2 without reheat.

In 2010, Sweden awarded 4-year-contract for improving Gripen’s radar and other equipment. On 25 August 2012 Sweden announced plan to buy 40-60 Gripen NGs, following Switzerland’s decision to buy 22 Gripens of the same variant. On 17 January 2013, Sweden’s government approved decision to buy 60 Gripen E’s, with first deliveries in 2018.

Unlike with Viggen, Gripen’s test flights revealed no aerodynamic, structural or engine deficiencies; in fact, all of them were better than predicted. Only structural “fix” was added strake behind each canard surface.

Basic data (Gripen C)

Length: 14,1 m

Wing span: 8,4 m

Height: 4,5 m

Wing area: 25,54 m2; 30 m2 with canards

Wing loading:

326 or 383 kg/m2 with 100% fuel, 4 AMRAAM and 2 Sidewinder

287 or 337 kg/m2 with 50% fuel, 4 AMRAAM and 2 Sidewinder

266 or 313 kg/m2 with 50% fuel and 2 Sidewinder

(*depending on wether canards are counted)

Thrust-to-Weight ratio: (80,51 kN – 18 100 lbf – thrust)

0,95 with 50% fuel, 4 AMRAAM and 2 Sidewinder

Fuel fraction:

0,27 (6 622 kg empty, 2 400 kg fuel) – 2 270 kg fuel was for A version’s “peace setting”; C version has only war setting

Weight:

6 622 kg empty

7 997 kg with 50% fuel and 2 Sidewinder

8 605 kg with 50% fuel, 4 AMRAAM and 2 Sidewinder

14 000 kg max takeoff

Maximum AoA:

>100 degrees (aerodynamic limit)

50 degrees (FCS limit)

Speed:

Mach 2,0 dash

Mach 1,15 cruise

Combat radius:

Ground attack, lo-lo-lo: 650 km

PS-05/A:

Range: 120 km vs 5m2 target (80 km vs 1m2 target)

Operational G capability: 9 g

Flyaway cost: 38 to 44 million USD (in FY 2013 dollars)

Cost per flying hour: 4 700 USD

Design

General

Saab Gripen is designed as a lightweight, highly maneuverable fighter. Close-coupled canard + delta wing arrangement was chosen to optimize maneuvering performance while also providing acceptable strike capabilities. Testing programs have verified excellent recovery capabilities for both Gripen versions. Further, delta canard configuration has inherently good battle damage tolerance due to “overlapping” surfaces, as well as positive trim lift on all surfaces, high maximum lift coefficient, good air field performance, and spin recovery capability. Floating canard also offers stable aircraft if EFCS fails.

To minimize weight, 30% of the structure is carbon-fibre composite. Aircraft is inherently unstable, and SAAB claims that it is first inherently unstable canard fighter to enter production.

While Gripen has low wing loading and good lift at high angles of attack, as well as relatively short wingspan, its thrust to weight ratio is below 1 at combat weight. Aircraft has operational service life of 8 000 flight hours.

Fuselage

One of things that can be noticed is large degree of wing/body blending, similar to F-16, which results in higher lift during maneuvers, as well as little or no interference drag that usually originates from wing-body juncture. Only exception to that are intakes, which are in side arrangement, with flat surfaces used for mounting canards. Body itself, having a “waist” noticeably thinner than parts immediately in front or aft of it, is clearly designed for transonic maneuvre.

Two small strakes are visible on the upper fuselage, located just behind canard surfaces, and single strake can be seen at bottom of fuselage; their purpose is to help enhance directional and lateral stability at high angles of attack.

Canards

Saab Gripen has canards that are relatively large compared to the wing. Canards are positioned close in front and slightly above the wing, and are tilted upwards, with large sweep-back. Location of canards at sides of air intakes prevents obstruction of air flow.

Primary purpose of close-coupled canards is not to act as control surface, but to increase lift at high angles of attack, where aircraft relies mostly on vortices to provide lift, by strengthening vortices generated by the wing and preventing their breakdown. Size and angle of Gripen’s canards are used to achieve as good as possible separation – vertical and horizontal – between canard’s tip and wing’s lifting surface, thus allowing for maximum vortex lift during high-alpha maneuvers – improvement of lift due to the close coupled configuration could be up to 50%, when compared to lift produced by surfaces in isolation. While thrust vectoring only increases maneuverability at very low speeds, and in supersonic regime, close-coupled canards are effective at any speed, though level of effectiveness varies with speed. As such, aircraft with close-coupled canards can have smaller wings for same lift at higher AoA (improving roll rate), being able to turn tighter at any air speed than otherwise possible with same wing size and angle of attack value, and achieving higher instantenenous turn rate. This also means that aircraft will be able to have lower wing span for same wing sweep and lift values, improving roll rates; smaller wing and reduced angle of attack also mean reduced drag when turning, allowing fighter to maintain energy better. However, downwash from canards also reduces wing lift at low angles of attack, reducing maximum payload fighter can carry.

Compared to LEX, canards are more versatile. Aside from being able to act as a control surface, canards can adjust position so as to produce maximum lift at any given angle of attack.

While Gripen managed to achieve angles of attack between 100 and 110 degrees during flight testing, normal AoA limit is 50 degrees as extremely high AoAs have no tactical use. Further, position of canards contributs to the fuselage lift of the fuselage just behind the canards during the turn, and canards themselves create lift, both in level flight and in turn.

Canard also has advantage over tail as the control surface – as center of gravity for modern aircraft is towards rear of the aircraft, usage of canard results in longer moment arm.

Canards can be tilted forward to nearly 90 degrees in order to aid braking during landing.

Wing

Wing itself is standard delta wing, offering large surface area, large volume and high strength for its weight. Shape of the wing ensures creation of vortexes at high angles of attack by wing’s leading edge, improving lift; wings are also equipped with small LERXes to strengthen said vortices. Another high lift device are leading edge flaps, which are used to increase lift at high AoA. When deployed during high-alpha maneuvers, flaps improve lift; however, they can also cause vortex breakdown. They also redirect air flow towards root of the wing, countering the tendency of air flow over delta wing to move towards wing tip. While usage of flaps can reduce drag, it only happens at speeds near stall speed, while in most other cases they increase drag. When flaps are not deployed, dogtooth leading edge configuration results in creation of single strong vortice at each wing, helping lift by countering tendency of delta wings to move air flow towards wing’s tips, and leave rest of the wing in stall. Wing is neither anhedral or dihedral, being located at half of the hull height. Due to wing’s (lack of) thickness, external actuators are required to control elevons.

Due to the Gripen being aerodynamically unstable aircraft, usage of delta wing also results in large trimmed lift during level flight, improving maximum lift by 10-20%, possibly more. Combination of close-coupled canards and low wing loading further improves air field performance, allowing for STOL capability.

While mechanism of lift creation at high AoA create additional drag, they increase lift and thus turn rate. But what some ignore while talking about drag “penalty” of close-coupled arrangement is that flow separation, aside from causing loss of lift, also causes major increase in pressure drag.

Rail launchers are located at wing tips, improving weapons loadout and allowing two missiles to be carried with minimum increase in drag, as well as improving lift/drag ratio of the wing.

Air intakes

Gripen’s air intakes are two-dimensional intakes, similar to those used at RA-5C. Intakes are separated from aircraft’s surface by fuselage boundary layer splitter plate, and provide adequate handling of fuselage boundary layer. High-alpha testing revealed no deficiencies in intake performance.

Fin

Tail fin is small relative to fighter’s size, compared to that of other Eurocanards and F-16. This might theoretically result in problems at high AoA; but usual way to change direction of aircraft is to rotate around X axis and pull nose up, and Gripen has additions on lower surface that may make fin unnecessary for directional stability.

Cockpit

One of major downsides of Gripen is its cockpit. While it allows good forward and side visibility, rearward visibility is very limited. This is dictated by its strike requirements, where exhaust from cooling unit is located behind cockpit to hide it from ground-based IR sensors. While SAAB did attempt to attenuate the problem by installing mirrors on forward canopy frame, it is only a partial solution.

Cockpit originally featured three monochrome multi-function displays, and wide-angle holographic HUD. It also has HOTAS controls that allow pilot to select many functions without lifting hands off the control stick or throttle. Ejection seat, unlike in previous aircraft, is not SAAB’s, but from Martin-Baker.

Engine

Engine is based on General Electric F-404 engine. Version used in Gripen, lincense manufactured by Volvo, had thrust boosted from 16 000 to 18 000 lbf (that is, from 7 257 to 8 165 kgf).

Operational characteristics

Gripen is capable of taking off and landing on roads, and could be capable of using unpaved runways. It can take off from 800 meter long snow-covered landing strips. Landing distance is reduced to 500 meters through usage of canards as air brakes, which is activated automatically when nose wheel establishes ground contact, as well as usage of elevons and large air brakes located at each side of fuselage behind the wing.

Further, it can be maintained by team of one specialist and five minimally-trained conscripts, and has very good combat turnaround time – less than 10 minutes. Gripen requires 10 man hours of maintenance for each hour in the air, and mean time between failure is 7,6 flight hours. Engine can be changed on road by 5 people in less than one hour. Airplane’s on-board systems include built-in “self-test” capabilities, with data being downloaded to technician’s laptop. All service doors to critical systems are at head level or lower for the easy access. Result is that Gripen requires only 60% of maintenance work hours of Viggen.

Aside from providing superior agility, Gripen’s FBW system is capable of automatically compensating for combat damage, including disabled or destroyed control surfaces – for example, using canards if aelirons are disabled.

Handling

Due to its aerodynamic layout, Gripen can be “parked” at 70 to 80 degrees of alpha. When giving adverse aeliron input, flat spin starts at up to 90 degrees per second rotation, and can be stopped by pro aeliron input. Aircraft has demonstrated spin recovery capability for complete cg and AOR range, as well as control capability in superstall, allowing recovery. During the spin testing, in one occasion when spin entrance was gained by wild maneuvering in afterburner, surge in thrust was recorded at high AoA and side-slip angles, but was immediately followed by instant recovery to full power.

Aircraft has operational G load limit of 9, and ultimate limit of 13,5 Gs.

Weapons

Gripen is armed with single Mauser BK-27 cannon, housed in a fairing on port side of aircraft’s belly (can be seen here). It currently also uses Sidewinder IR AAMs, though these are to be replaced with IRIS-T missiles. BVR missile is AIM-120 AMRAAM, though aircraft is also capable of using MBDA Meteor, Matra Mica, and BAe Sky Flash (built in Sweden as Rb-71).

For anti-ship combat as well as ground attack, it can carry SAAB RBS-15 missile (though only Mk3 version of the missile supports land attack missions). Dedicated air-to-ground missiles are AGM-65 Maverick (built in Sweden as Rb-75).

Fact that Gripen uses revolver cannon is a large advantage over aircraft using Gattling guns: while Gattling guns typically take 0,5 seconds to achieve full rate of fire, revolver cannons take only 0,05 seconds. As such, while M61A1 will fire 25 rounds in first half of second, weighting total of 2,5 kg, BK-27 will fire 13,45 rounds, weighting total of 3,5 kg. Larger caliber also ensures greater damage-per-hit, important due to stronger airframes of modern fighters.

Aside for gun, Gripen also has 6 missile hardpoints on wings. Two of these are in wingtip configuration, ensuring minimal drag in flight, while other four are mounted on low-drag pylons. Another hardpoint is located at the bottom of aircraft’s hull in centerline configuration. It is usually used for fuel tank carriage, though it can also carry targeting pods as well as ground attack ammunitions.

Sensors & EW suite

Gripen is equipped with radar PS-05/A, that is capable of detecting targets with RCS of 5 m2 at distance of 120 kilometers, which translates into 80 kilometers against 1 m2 target.

EW suite is built around AR-830 Radar Warning Receiver, with receiveing antennas at front and back of missile launch rails. BOL dispensers are bult into ends of missile launch rails and have capacity of 160 chaff packs or flares; BOP/C dispensers are built into the fuselage, and BOP/B into end of the wing pylons. Lattermost can trail BO2D towed repeater RF decoy, which can be used at supersonic speeds.

Gripen’s limited sensory suite in versions so far is a large shortcoming in combat – namely, lack of IRST, which means that Gripen pilot will have to rely on visual detection (not possible during night, insufficient in bad visibility conditions) or on opponent using his own radar (relying on opponent being an idiot should never be part of any plan). This was realized by SAAB, and Gripen NG will be given IRST; earlier version of Gripen, however, will either have to be retrofitted with an internal IRST system, or settle for using FLIR pod for both air-to-air and air-to-ground missions (if possible). That is probably connected to the fact that Gripen was always intended as a defense weapons, and could thus rely on directions from the ground.

Signature reduction

While the fact that Gripen is relatively small aircraft automatically means smaller IR and visual signatures, there were some specific attempts made at further reduction. Just behind cockpit are located ducts, which are used to release exceess heat from heat exchangers, reducing Gripen’s IR signature as seen from ground.

As far as radar signature is concerned, care was taken to reduce frontal RCS, though side RCS is not likely to be large as long as radar emitter is not at precise 90 degrees angle relative to the aircraft, which would result in return from aircraft’s side surfaces – in particular tail, nose and intake surfaces.

Datalinks and communications

Flygvapnet pioneered the use of datalinks in the combat aircraft, fielding first versions on SAAB 35 Draken in mid 1960s. Gripen is equipped with four high-bandwidth, two-way data links, with range of around 500 kilometers. This allows for exchange of targeting information and other data, even when one of aircraft is on the ground. One Gripen can provide data for four other aircraft, as well as get access to ground C&C systems and SAAB-Ericsson 340B Erieye “mini-AWACs” aircraft. It can also allow fighters to quickly and accurately lock on to target by triangulation of data from several radars. Annother possibility includes one fighter jamming the target while another tracks it, or several fighters using different frequencies at the same time to penetrate jamming easier.

Gripen NG

For Gripen E, SAAB has stated that empty weight will be under 7 000 kg, and engine also apparently has 22 500 lbs of thrust. It also has 3 300 kg of internal fuel, achieving 1 300 km combat radius with 30 minutes loiter time in AtA configuration on internal fuel, or 1 800 km with no loiter time. OTIS IRST will also be added.

Gripen NG will be significantly cheaper than other 4,9 generation aircraft, such as Eurofighter Typhoon or Dassault Rafale, and with 22 ordered by Switzerland and 40-60 by Sweden itself, it has prospect to achieve success on export market as well. Some sources place flyaway cost at less than 50 million USD; my estimate is that it will likely be around 45 – 55 million USD per aircraft.

According to some reports, wing area is double of Gripen C’s, fuselage is 20% longer, but it is made out of carbon nanotube reinforced polymer composites, reducing weight compared to Gripen C. All images of Gripen NG to date, however, seem to be using Gripen C / Gripen Demo as basis (Gripen Demo is test aircraft built by using Gripen C airframe, and images that could indicate wing area don’t show any difference in fuselage dimensions). Another presentation also shows Gripen NG’s empty weight as 7 120 kg, and wing loading as 317 kg/m2 in combat configuration with 50% fuel. (Interesting point is that same presentation states that IRIS-T will be able to shoot down BVR missiles from other aircraft, though slide in question is not entirely clear). OTIS IRST will operate in 3 – 5 and 8 – 11 micron wavelengths.

Conclusion? I won’t draw conclusion about NG until it is airborne and in service.

Image of Gripen landing. Take note of air brakes and canard position:

JAS-39 Gripen landing

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