Haubits FH77/A
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[edit] History
Fälthaubits 77-systemet (FH77) (field Howitzers 77) was developed in the late 60’s by Bofors. During the development 77-system the following specifications where emphasized.
- Ease of movement on road and in field
- High rate of fire, also a be able to fire at great distance with good precision
The Bofors designed Haubits 77 was like its predecessors well built and well designed.
When the FH77/A entering service with the Swedish armed forces, Sweden has only a limited number or modern guns, most of the artillery at this time was dating back to the second world war. The most modern artillery at the time in service with the Swedish army was the Bandkanon 1 a Swedish designed self propelled Gun Howitzer and the French designed Haubits 15.5 F (Obusier de 155 mm Modèle 50) manufactured under license in Sweden since the 1950’s.
The FH77/A was the first field howitzer in the world featuring an APU (auxiliary power unit). The FH77/A was developed as a compromise between the more expensive Self propelled tracked howitzer and the conventionally towed field howitzer.
All the Haubits 77/A howitzers were delivered between 1978-1985, Today there is only a limited numbers still in active service. Some have been modified with new fire control equipment and these have the designation Haubits 77AP.
The rate of fire was at the time of it entering service one of the highest in the world for a 155mm field howitzer, the FH77/A could fire 3 rounds in 8 seconds or 6 rounds in 25 seconds. In a sustained firing role the FH77/A could fire 6 rounds every second minute for 20 minutes.
Due to the risk of counter battery fire and the risk air attack, most artillery units fires of no more than 6-8 rounds and then moves off to a new firing location to prevent the destruction of the unit. This is something that the self-deployable FH77/A excels at.
There are only relay two design flaws on the FH77/A, The first one is the problem that the FH77/A is unable to fire the standard NATO round. This is due to the use of the disposable casing. The other one is the limitation of the elevation of the barrel, the highest elevation at 50° prevents the FH77/A to fire over grade trajectories. And due to the above limitations the FH77/A it was more or less impossible to export the Howitzer.
[edit] Specification
- Era: Modern
- Name: 155 mm FH77/A Haubits
- Type: Howitzer
- Nation: Sweden
- Manufacturer: Bofors
- Target: General
- Date: 1978
- Production Date: 1978-1984
- Service Date: 1978-2000’s
- Numbers Built 206
- Operators: Sweden
- Breech: vertically sliding breech block, Hydraulic ramming (semi automatic)
- Barrel: 38 cal (5890 mm)48 grooves, 7° twist
- Elevation: -5 to +50°
- Traverse: 30°
- Caliber: 155×787 mm
- Carriage: Split trail with castor wheels
- Weight: 11500 kg
- Length: X
- Shell Types: se below
- Action: semi-fixed ammunition, propellant charge is contained in a disposable plastic cartridge case with a steel head.
- Muzzle velocity: 300-770 m/s
- Tactical range: 21 km (24 km with base bleed)
- Maximum range: 24 km
- Rate of Fire: 3 rounds in 8 seconds or 6 rounds in 25 seconds, sustained fire 6 rounds every second minute for 20 minutes
- Crew: 10 -14
- Transportation: self deployable with APU and towed using Scania SBAT
- Miscellaneous: Perforated muzzle brake
[edit] Ammunition
The FH77/A Howitzer uses the m/77 155mm HE shell combined with a disposable casing; the casing is made of plastic with a steel head. The cases came with either the number 1 to 4 or 5 to 6 increments. The charge is ignited with a standard percussion primer. Using the number 6 charge with the m/77 HE the maximum range would be 21.000m (21km).
If you want to shoot with the number 3 charge you would take a 1-4 charge and remove the number 4 charge.
The FH77/A could also fire the older HE m/54-77 - but is unable to use the number 6 charge.
The FH77/A can also use the Base bleed round m/77B bf1 developed for the FH77B but without the automatic loading and this reduces the rate of fire dramatically.
The maximum range for the gun using a base bleed round would be 24.000m (24km), but you would be limited to single round loading.
The FH77/A is deployed by lowering the castor wheels on the trail legs, thus lifting the lunette from the towing hook. The driver then drives the howitzer to the deployment position and swings it to one side, and then to the other, in this way spreading the trail legs and locking them in their outer positions. He then raises the castor wheels and drive the howitzer in reverse, digging the trail spades in. The whole operation takes less than a minute and can be performed by only two men.
[edit] APU - Auxiliary power unit
The howitzer has a APU powered by a 2.0 Liter Volvo B20 petrol engine. This makes the FH77A self maneuvering on the battle field. The engine is linked to three hydraulic pumps two are linked to the wheels and one hydraulic pump for the traverse, elevation, ramming and to the ammunition crane.
When the FH77/A is in driving mode the hydraulic fluid goes to the hydraulic pumps linked with the wheels on the howitzer. When in firing mode the hydraulic fluid is moved out of the hydraulic pumps linked to the wheels and is transferred to the hydraulic pump powering the traverse, elevation, ramming and to the ammunition crane.
You maneuver the howitzer but regulating the flow of hydraulic fluid between the wheels. The speed is regulated by changing the RPM on the Volvo B20 petrol engine. The hydraulic system also provides power to the two castor wheels at the end of the carriage.
[edit] Crew
The crew consists of 10-14 men. The minimum crew setup would be a 5 person crew, one commander (conscript / 10 month service), aimer/in charge of aiming the howitzer (conscript / 10 month service ), loader 1, loader 2 and driver/loader 3 (all with 7.5 month service) .
The commander would direct all the activity of the howitzer from standing on a plate located to the left of the aimer.
The aimer would sit on the left hand side controlling the fire control computer and he would also be the driver of the howitzer when in self deployment mode.
Loader 1 is located to the right of the breech and is in charge of supplying the shells form the load table located in front of him.
Loader 2 and 3 would be working on the ground directly behind the howitzer providing shells to go up on the load table and providing the charges and ensure that the charges has the right charge in them.
The crew normally consists of two setups of the above crew to provide a 24/hrs capability.
[edit] Deploying & Firing
Using a towing vehicle
The most common towing vehicle for the FH77/A was the Scania SBAT (tgb40), The Scania SBAT is one of the most powerful all-train vehicles in the world, equipped with a turbo charged 296hp diesel and with automatic transmission both of Scania design. The truck is equipped with a personal compartment just behind the driving cab for the crew and it also has a HIAB-crane for ammunition handling. The built-in engine on the FH77/A can also be started and controlled by the driver in the towing vehicle to give an extra boost to off road driving. The maximum speed on the road with a full load of ammunition and crew is 70 km/h (45 mph)
Deploying for Firing
The FH77/A is deployed by lowering the hydraulic operated castor wheels on the end of the trail legs, thus lifting the lunette from the towing hook. The crew drives the FH77/A to the deployment position and moves the carriage out to its firing position by moving the howitzer to the left and to the right. When the trail has been put in its firing position the driver raises the castor wheels and drives the howitzer in reverse to dig the trail spades in. The procedure usually takes no more than one minute and can be done with only two crew members.
Firing
The number 1 loader sits on the right hand side of howitzer and has a loading table in front of him; the shells are hoisted in 3’s with the help of the hydraulic crane up onto the load table. Before firing the number one loader sets the fuse settings and then places the shell in the loader, at the same time as the number 1 loader places the shell in the loader, the remaining crew has prepared the charge casings with the correct charge and then places the charge onto the loading bridge, at this time the shell moves on to the loading bridge and is joined with the charge casing, after the shell and casing has joined the loading bridge moves up to the breech and the hydraulic rammer rams the now complete round into the breech and the breech block closes and the howitzer is now ready for firing.
When the aimer presses on the firing pedal the round is fired and the recoil forces the breech to open and ejects the empty casing, while this was taking place the loading crew has prepared another round and the whole procedure starts all over until the load table is empty.
