On 21 and 22 Aug, Ian Knight who is a pilot flying with the Royal Netherlands Air Force posted a few pictures & videos of Small DiameterBomb or SDB being dropped from F 35. The video depicted F-35A dropping a full load of 8 SDBs. He mentions that 16 SDBs were launched in the test - 8 from F-35A of the Royal Netherlands Air Force and another 8 from F-35A of the US AirForce. Viewers may note that Royal Netherlands AirForce is a partner in the F-35 program, has been extensively involved with the F-35's flight testing and optimization with aircraft and personnel operating out of Edwards AFB for years.
The Dutch Parliament approved an order for eight Lockheed Martin F-35As in March 2015, confirming the aircraft as the official replacement for the F-16 for the Royal Netherlands Air Force. The Netherlands may acquire up to 37 aircraft. This article, analyzes howGBU-39 Small Diameter Bomb makes F35 Lightning II a deadly adversary? Let’s get started. The Lockheed Martin F-35 Lightning II which is a single-seat, single-engine, all-weather stealth multirole fighters is undergoing final development and testing by the United States. The Pentagon began the F 35 program in 2001with an aim to develop a cost-effective replacement for the U.S. military’s F15 fighters, F16 and F18 fighter bombers and reconnaissance aircraft, and A10 close in support warplanes. The F-35 has three main models: the conventional takeoff and landing F-35A (CTOL), the short take-off and vertical-landing F-35B (STOVL), and the catapult-assisted take-off but arrested recovery, carrier-based F-35C (CATOBAR).
Apart from the United States, the primary customer and financial backer, the United Kingdom, Italy, the Netherlands, Canada, Australia, Norway, and Denmark are also part of the program. Many other nations like Japan and Israel are also deploying the fighters. These major partner nations, including theU.S, plan to acquire over 2,000 F-35s through 2035, which, if delivered will make the F-35one of the most numerous jet fighters. On 2 August 2016, the U.S. Air Force declared its first squadron of F-35A fighters combat-ready. Fighter aircraft are expected to remain in service till 2050. F 35 is a 5th generation fighter that is developed from grounds up to be stealthy. Its external structure is designed to deflect signals away from the emitting radar which makes it hard to detect or track.
This is done by having no sharp edges or protruding elements and having a smooth external curvature. Also, it has a coating of RAM (Radar Absorbing Material) that reduces the number of signals getting reflected. Classified techniques have been used to reduce the heat signature of F 35. This thermal profile management of the jet makes it difficult for Infrared (IR) homing missiles to target it. F 35 has the lowest Radar Cross Section (RCS)of all the fighter jets except the F 22 Raptor. • Against x-band radars, it is stealthy from the front and rear • Against S-band radar, it is stealthy from the narrow front aspect • Against L-band radar, the limited reduction is achieved from direct front It is a very Low Observable (LO) platform in reality, unlike some of its so-called competitors.
For example, Chinese Chengdu J-20 got sometime back. Indian pilots on Russian-made Su-30MKIs from Indian airspace managed to detect and track the new Chinese jets when they were conducting flight training over Tibet. The disclosure didn’t come from any independent analysts but from an official source. Indian Air Force commander Arup Shaha said, "The Sukhoi's radar can see them. The new Chinese jets are not so invisible after all. No special technology is required to detect the J-20, as it can be detected by ordinary radar stations.” This has ignited debates that the J 20 is nothing more than a decorated 4++ generation fighter. But in this mode, F 35 has limited weapons carriage capacity as everything has to be accommodated internally. This is where the GBU-39 Small Diameter Bomb comes in.
The GBU-39 Small Diameter Bomb SDB is a 250lb or 110 kg precision-guided glide bomb that is intended to provide aircraft with the ability to carry a higher number of more accurate bombs. Most aircraft carry these using the BRU-61/Arack The small size of the bomb allows a single strike aircraft to carry more of the munitions than is possible using currently available bomb units. The SDB carries approximately 36 lb or 16kg of AFX-757 high explosive. It also has integrated "Diamond Back" type wings which deploy after release, increasing the glide time and therefore the maximum range. Its size and accuracy make it an effective munition with less collateral damage. Warhead penetration is 1 m (3 ft 3 in) of steel-reinforced concrete under 1 meter (3 ft 3 in) of earth and the fuze has an electronic safe and fire (ESAF) cockpit selectable functions, including air burst and delayed options.
The SDB I has a circular error probable (CEP)of 5–8 m or 16–26 ft. CEP is reduced by updating differential GPSoffsets prior to weapon release. These offsets are calculated using an SDBAccuracy Support Infrastructure, consisting of three or more GPS receivers at fixed locations transmitting the calculated location to a correlation station at the theatre Air Operations Center. The corrections are then transmitted by Link16 to SDB-equipped aircraft. The F-35 and the F-22 as well as 4th generation fighters can leverage the GBU-39 for air to ground strikes. Also, SDB is suitable for future unmanned combat air vehicles (UCAVs) especially the smaller once because of the compact dimensions F-35A’s stealth characteristics enable it to penetrate deep inside enemy territories and with SDB it could wreak havoc behind the enemy lines.
For example, 2-3 F-35A carry a full load of SDB could takeout almost all the aircraft sitting in a base or destroy air defense component guarding a high-value target. In 2002, while Boeing and Lockheed Martin were competing to develop the Small Diameter Bomb, Darleen A. Druyun—at that time Principal Deputy Assistant Secretary of the Air Force for Acquisition and Management—deleted the requirement for moving target engagement, which favored Boeing. She was later convicted of violating a conflict of interest statute The GBU-39 has been operational for 14 years and work is going on a new variant named GBU-57 SDB II Stormbreaker that can engage moving targets in any weather. It will incorporate a tri-mode seeker and a new data-link - so radar, infrared homing, and semi-active laser guidance will be added to the INS and GPS guidance pack of the original SDB.
This will further enhance SDB and enable it to perform tasks such as close air support against moving ground targets and anti-ship attacks. F 35s has great situational awareness thanks to its sensor fusion capability and this makes the fighter an excellent launch platform for the SDB. It is clear that SDB is a huge force multiplier for stealthy tactical aircraft like the F-35 which has very finite weapons carrying capabilities.