Haubits 77 (Swedish "Field Howitzer 77") or FH77 is a Swedish 155 mm howitzer. It was developed and manufactured by Bofors. It was available in two versions, the original (sometimes referred to as Haubits 77 A) with a sliding block mechanism, and the later FH77 B export version with an interrupted screw breech. India is currently developing an upgraded (155mm/45 calibre) version of the FH-77 called FH-77 B02.
Design and development
In the 1960s Sweden started to look for a replacement for the French Haubits F (Obusier de 155 mm Modèle 50). The American M109 howitzer was offered and tested. Though the price was low the Swedish Arms Administration found the high maintenance costs, the low rate of fire and the not so good mobility of the M109 made it worth the effort to develop a domestic howitzer.
The requirements for a new gun would be:
- High mobility.
- High momentary rate of fire.
The result was a compromise between a more expensive self-propelled howitzer and a less mobile conventional towed howitzer.
The FH77 was the first field howitzer featuring an APU to make it self-propelled for tactical movement.
The rate of fire was, at the time, exceptionally high for a 155 mm howitzer. The FH77A (which uses semi-fixed ammunition) could fire 3 rounds in 8 seconds, or 6 rounds in 25 seconds. In a sustained firing role it could fire 6 rounds every two minutes for 20 minutes (i.e. 3 rounds per minute). The FH77B uses bagged charges and so has a lower rate of fire.
Driving & Deploying
The dedicated towing vehicle for the FH77 was the Scania SBA111 (Tgb 40). The truck was equipped with a crew compartment behind the driving cab and a HIAB-crane for ammunition handling. The Howitzer's APU can be started and controlled by the driver of the towing vehicle to give an extra boost during off road driving. The maximum towing speed is 70 km/h (45 mph).
The FH77 is maneuvered by controlling the torque of the two main wheels. Speed is regulated by changing the RPM of the APU. The howitzer is deployed by spreading the trail legs, raising the castor wheels and driving the howitzer in reverse.
The FH77 is powered by a Volvo B20 Auxiliary power unit (APU). The engine is connected to three hydraulic pumps, of which two pumps are linked to the wheels and one is used for a traverse, elevation, ramming and ammunition crane.
The crew consists of 10-14 men. The minimum crew setup would be 4 men; commander, layer, loader 1 and loader 2
- The commander directs all the activity of the crew from a platform to the left of the gun layer.
- The layer sits on the left hand side of the gun, operating the fire control computer and driving the howitzer when in self-deployment mode.
- Loader 1 is located to the right hand side of the gun and is in charge of supplying the shells from the loading table in front of him.
- Loader 2 and 3 would be working on the ground, providing shells to loader 1 by means of a hydraulic crane and loading cases in the loading trough.
The FH77A uses the m/77 (42 kg) 155mm HE shell combined with a plastic casing, containing 6 increments. The FH77A could also use base bleed ammunition developed for the FH77B.
- FH77 A - original baseline version.
- FH77 B - export version with a modified breech block and lower rate of fire.
- FH77 B02 Upgraded - Indian upgrade of FH77 B to 155mm/45 calibre with electronic and mechanical overhaul (currently under development).
- FH77 B05 L52 - further development of the basic version from 39 to 52 caliber gun barrel with improved overall performance.
- Archer Artillery System - self-propelled version with a 52 caliber gun mounted on the chassis of a Volvo articulated hauler.
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