The Armament Research and Development Establishment, Pune is the primary agency that started developing HSLD with the help from other DRDO laboratories to upgrade the conventionalfree fallunguided ordnance used by the Indian Air force fighter pilots while Ordnance Factory Board is the lead production agency. The development started with the aim to replace the older generation imported general purpose bombs that impose huge drag loss on fighter aircraft used by the IAF. The HSLD bomb is specially designed to productively use the higher speed of up to Mach 1.1 and wider flight envelop of newer generation NATO and Russian origin as well as Indian made aircraft. High Energy Materials Research Laboratory developed the conventional type warhead that features blast, fragmentation and shaped charge for bunker buster role which uses Dentex as primary explosive for HSLD 450 and Torpex-4B mixed with RDX that act as explosive booster for HSLD 500. The warhead can be used to effectively destroy runway, railway track, bridge, industrial facility, dock and bunker. The family of HSLD comes in two versions namely a general purpose bomb and a precision guided high speed low drag unit under three different weight class category which features semi-active laser homing and anti-jammingsatellite navigation antenna. HSLD is designed to carry a nose extension unit with fixed canard for lift, stability and two different types of smart tail unit with individual independent fins controlled by a flight control unit attached to a telemetry module to cover the whole spectrum of mission profile. The STU features a retarder tail unit that is for low-level bombing missions while a ballistic tail unit that can used for strategic high level bombing. HSLD can be launched from variety of aircraft that are under IAF inventory like Dassault Mirage 2000, Mikoyan MiG-29, SEPECAT Jaguar, Sukhoi Su-30MKI and HAL Tejas. IAF has already successfully tested PGHSLD 500 from Su-30MKI platform.
Trials
From 22 May 2017, ARDE and IAF conducted a series of carriage as well as carriage release trials for High Speed Low Drag 500 kg class unit, with both general purpose and precision guided variant at Pokhran range, Rajasthan. In initial carriage trial, the bomb carried sensors, telemetry and data logger while during the separate CRT session, satellite guidance units were added which flew on Su-30MKI from Jodhpur Air force Station. The bomb touched the carriage limit of 1041 km/h at 150 metre altitude on Su-30MKI that performed a 6.5 g full roll manoeuvre during the first GPB 500 trial while the PGHSLD 500 separation was carried out from an altitude of 5 km at a speed of 900 km/h. Both bombs cleared the flight envelop and completed all the required parameters without any form of mechanical damage during the high speed release from the aircraft. The trials were conducted with the help of Hindustan Aeronautics Limited, Indian Air Force Test Pilot School and Centre for Military Airworthiness and Certification.
