OT-90 - External Details

External Features of the OT-90

For a design with it's roots in the 1950's the BMP series of vehicles has a reasonably good ballistic profile when head on compared to other vehicles, The acute slope of the lower glacis plate and the shallow slope of the upper deck were good at defeating the artillery of their day - indeed head on they remain reasonably effective today. same with the turret profile of both the original BMP and SKOT turrets. Looking at the side profile you can get a feel for how low the profile is, Have a look at the comparisons page to see how it compares with it's Nato equivalents. You may also get a feel for just how cramped the interior gets when fully loaded

NOTE: If any image is too small to see the details clearly simply click on the image and a larger one will open for you to study at your leisure.

Function vs Form

The original design brief for the BMP series, originally known as Ob'yekt 764, laid down six primary considerations for the project:

Speed.,
Good armament,
The ability for all squad members to fire from within the vehicle.
The armament had to provide direct fire support for dismounted infantry in both attack and defense.
To be able to destroy comparable light armored vehicles.
The vehicle needed to protect the crew from .50 cal machine gun fire and 20-23 mm calibre weapons across the frontal arc as well as from light shell fragments at distances between 500 metres and 800 metres..

The original turret fitted to the BMP-1 housed a 73mm auto-loading smoothbore, low muzzle pressure cannon as well as a launcher rail for the Malyutka anti-tank wire-guided missile (NATO code name "Sagger"). As already stated the SALT talks that imposed a limit on the amount of anti-tank weaponry meant a lot of the BMP-1 series were liable for either scrappage or sales to satellite countries. However, following an intensive engineering program at the PPS Detva engineering works a number were converted to OT-90's The smaller SKOT turret has the high angle mount for the 14.5mm KVPT allowing the weapon to be used for a range of roles from direct fire support to antiaircraft support. During the remodelling program some issue noted by the Czechs were addressed - notably the suspension. Originally the BMP-1 only had shock absorbers on the 1st and 6th road wheels. The Czechs added an additional shock absorber on the 2nd road wheel greatly enhancing ride quality for the driver and commander. When going cross country neither were prone to bouncing their skulls off closed hatches. Other modifications included adding a carrying point for a sustained fire tripod mount for a PKM, increasing the main fuel tanks capacity from 300 to 350 litres. In line with its underpinnings as a BMP-1 though the design retains all the original features like a front mounted engine and twin rear access doors that are actually balanced for easy opening and closing. The OT-90 also retains the ability to meet 5 out out of the 6 original design briefs - No's 1 to 4 and 6.

Offensive Weapons Main turret gun is the 14,5mm calibre KVPT heavy machine gun. Heavy in name and nature this weapon stands at just over 6' (1.8 metres) in length. Installation requires a minimum of 4 people!

This weapon has an aimed range of 2000 metres and a rate of fire of 500 rounds per minute.
The coaxial mount in the turret is a 7.62mm calibre PKT machine gun - a derivative of the PKM squad weapon but with solenoid firing rather than a conventional trigger.

This weapon has an aimed range of some 1500 metres and a rate of fire of 2000 rounds per minute. Note in this picture the cable hanging down - this connects to a junction box on the turret cradle and is the firing mechanism

Needless to say - both of these have been deactivated in accordance with UK Firearms Regulations.

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Defensive abilities The OT-90 has two defensive tricks up it's sleeve. Firstly is the ability to make itself disappear - that is to say a lay a smoke screen. The vast majority of armoured vehicles rely on smoke grenades to accomplish this, the draw back being once fired the launchers have to be reloaded. Not always - in fact rarely - possible, on a battlefield. The OT-90 however uses the method of injecting diesel oil into the exhaust system. This produces instant clouds of thick smoke provided the engine RPM are held above 2,0000. This is sufficient to hide the vehicle whist it beats a hasty retreat.

If retreat is not an option then the vehicle can make use of the exceptional maneuverability it is endowed with by means of its light steering and low ground pressure. If you can imagine driving a 13 ton go-kart you can imagine what it's like to drive an OT-90!! This short video clip gives an idea of how nimble it can be.

Note the exhaust plume whist running - you should be able to envisage how effective a smoke screen generated by dumping MORE diesel into the exhaust would be!! Unfortunately I do not have any film of this yet.

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Offensive Abilities As noted in the design brief above and on the "Internal Details" page the 8 troops in the rear fighting compartment can engage the enemy without dismounting from the vehicle and without compromising the vehicles amphibious capabilities. This is achieve by the use of closable firing ports in the side of the vehicle. Looking at these images you can clearly see these firing ports in the open position:

When closed these port doors seal onto rubber pads tightly preventing water ingress. Note the difference in shape of the leading port - whereas the 3 rearmost ones are tear-drop shaped the front is more of a "D" shape - this is because the port is for the PKM machine gun which mounts on a 30 deg angle of fire.

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Weak Points As ever in life - nothing is perfect and this as true of the BMP-1 design as any other. Conventional Warsaw pact vehicles carry their additional fuel in cylindrical external tanks which can be dropped before combat by a simple cable release. However in the case of the BMP/OT-90 the designer wanted a low silhouette and opted to make use of the rear doors instead as these were already hollow as a buoyancy aid. As a result each door can hold up to 180 litres of diesel.

Imagine the fun this can cause to the occupants when an anti-tank round comes in through a door containing fuel!!

This is the L/H door and you can see the fuel filler at the top of the door. This door also has the provision for rear defence - note the vision block currently covered by a steel shroud that is liftable from inside and the firing port in the closed position. Both rear doors carry a spare track section - the armoured equivalent of a spare tyre!

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Ingress and Egress Or in other words - getting in and getting out!!
For the driver and commander the method of entry is to approach from the front of the vehicle (always the manner to approach any armoured vehicle for safety sake unless circumstances dictate otherwise) and place one foot on the right hand front drive sprocket, grasp the lifting handle for the front engine deck and pull oneself up and on. If the vehicle is closed the commanders hatch is opened by means of the "Tee" key and then either one may lean in and forwards to release the drivers hatch.

The gunner enters from the right hand rear of the vehicle cia the troop door, slides along the seat and thence up into the turret The troops in the fighting compartment also approach from the rear and enter, 4 a side via the rear doors. Once inside space is at a premium but the four overhead hatched can be opened to allow light and air to enter unless in a combat zone.

The above image give an idea of how tight the rear is for space - with only 3 men in this side. The roof hatches can clearly be seen in the open position though and, in the event of emergency can act as escape hatches for the troops and gunner. - they are sprung loaded and as soon as the release catch is operated are designed to fly open in a more or less vertical position.

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External Storage As with all armoured fighting vehcles a lot of equipment including what is termed "Pioneer" kit is stored on the outside of the hull in desgnated hard points. For the OT-90 there should be:

A pick axe
A long handled shovel
a 2.5 metre pry bar
Towropes/chains
A 3 metre llong vaulk of timber dor use in un-ditching operation
Camouflage nets - stored in straps on the rear of the turret

In addition to al this any personal kit for the crew and troops that cannot fit inside the vehicle is usually lashed to the roof of the figting compartment . The exception to this is when the vehicles are in use in an area likley to be infested with IED's - the floor of the hull has been found to offer inadequate protection against such things and in these circumstances it is normal for the crew to ride on top of the vehicle and for the personal kit to be stowed inside. This defeats the primary purpose of this type of vehicle as then the troops are exposed to hostile fire - however space inside is so tight that the usual expediaent of lining the floor with sand bags to enhance protection cannot be used.

One other item worth of note in this section is the vehicles radio aerial - it mounts onto a sprung point at the L/H rear of the vehciles and is broken down into 4 sections for storage. The aerial is fairly flexible and it is not uncommon when manouevering rapidly and braking hard for the tip to deflect downards far enough to deliver a sharp rap to the drivers head or neck!

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Welcome to the OT-90

External Details

Related Documents

External Links

External Features of the OT-90

Function vs Form