EE-11 Urutu with 60 mm Gun/Mortar

Federative Republic of Brazil (Late 1970s)
Armored Personnel Carrier – 1 Prototype Built

When Engesa started manufacturing the Cascavel and Urutu in the early 1970s, the idea of an armored personnel carrier armed with a 60 mm gun/mortar armed turret was conceived. Such a vehicle was already mentioned in early catalogs and a single prototype would be realized somewhere in the late 1970s. The exact goal or customer for the 60 mm Gun/Mortar Urutu is unknown, but it is likely that the success of the 60 mm gun/mortar armed AML-60 in Africa may have had some influence.

The Urutu was meant to transport troops and provide close fire support for infantry against resistance points and in urban combat. The Gun/Mortar carrier was not successful as no vehicles of the variant seem to have been sold. In the end, like a number of other variants of the Urutu, it seems to have mainly been a project for the sake of providing extra options and hoping to enter an oversaturated market of 60 mm gun-mortar carriers in Africa.

The Urutu

The Urutu was Engesa’s troop transport, designed by Engesa and the Brazilian Navy. The vehicle was designed from the ground up to be amphibious, and was approved in 1972 after successful testing in various conditions. it was modified with multiple snorkels, propellers, and a wave breaker for operation on open sea.

Serial production began in 1975, using the same suspension, engines, and transmission as the Cascavel. It managed to achieve large sales to Iraq, Libya, and most of South America, but the Urutu would never reach the same success as the Cascavel. Both the Cascavel and Urutu were upgraded throughout their production runs with different engines, transmissions, and brakes, as well as different hull designs. The Urutu was operated by a driver and commander, and could carry 10+2 fully equipped infantrymen (with the +2 sitting at the side doors of the vehicle).

In addition, it could be equipped with a multitude of different turrets (including Anti-Aircraft). The Gun/Mortar Urutu was made by mounting a 60 mm mortar armed turret on it. Apart from the turrets, the Urutu could also receive various optional components, like an automatic fire suppression system, amphibious equipment and Nuclear Biological Chemical (NBC) protection, all at the client’s discretion.

The Gun/Mortar Concept

Why exactly Engesa decided to offer a gun/mortar carrier is unknown, but a reasonable deduction can be made from the French Panhard AML and the South African Eland armored cars. According to SIPRI, about 3,100 60 mm gun/mortar and 90 mm D921 armed AMLs and Elands were sold to many African and South American countries, of which at least about 580 were armed with various versions of 60 mm gun/mortars.

The gun/mortar concept was meant to provide close infantry support, the protection of logistical routes and troop deployment zones, the neutralization of small resistance points, like machine guns or strengthened positions, terrain clearing, and urban combat. In short, these vehicles were meant to provide all sorts of infantry support, be it direct or indirect fire. Especially the indirect fire capability would give the gun/mortar a wheel-up over the 90 mm armed AMLs, which would only be able to fire at direct targets and may not have been as cost-efficient per shot.

The Prototype, Further Marketing

Considering the amount of gun/mortars sold to African nations and the relative ease of incorporating such a platform on an existing vehicle. It is perhaps not surprising that Engesa offered it as an option for the Urutu. The Urutu was an APC which transported troops to the battlefield. Since the Urutu was now at the front anyway, it might as well have been able to support the infantry it just dropped off with the mortar. In essence, Engesa did not have to do much more than either buy a 60 mm armed turret or just buy the mortar and design a simple turret around it. Apart from that, they had to offer ammunition stowage racks inside the vehicle.

The first mention of a gun/mortar variant of the EE-11 is in a brochure dating after 1976. Here, the possibility of arming an Urutu with a turret mounted 60 mm mortar is mentioned. Interestingly, this exact brochure also already shows the prototype having been built on the cover. The prototype was converted from an M2 hull, which would suggest that the prototype was built somewhere in between 1976 and 1980 (from that point on, the EE-11 M3 hull was introduced).

From then on, the 60 mm Urutu would continue to be marketed for more recent hull models. Instead of the manual transmission which was used on the M2 hulls, the automatic MT-643 transmission was offered. The marketing would be to no avail however, as not a single country is known to have acquired the 60 mm Gun/Mortar Urutu.

The Gun/Mortar EE-11 Urutu in Detail

Overall dimensions were the same as the normal Urutu, with the exception of the height and weight, due to the turret. It was 6.15 m (20.2 feet) long, 2.59 m (8.5 feet) wide, and about 2.7 m (8.9 feet) tall, which was about 0.5 m (1.6 feet) taller than the original Urutu. It weighed around 13 tonnes (14.3 US tons), about 1 tonne (1.1 US tons) more than the Urutu. This could change even further depending on the engine used. It was operated by a crew of two plus eight (commander and driver and 8 passengers).

Hull

The Gun/Mortar Urutu’s hull was the same as the regular Urutu’s with no major difference whatsoever except the redesigned troop compartment for ammunition stowage. The choice of engine, transmissions and modifications, such as automatic fire extinguishers, were up to the client’s discretion.

The Urutu was armored with 12 mm (0.5 inch) thick armor at the front and 6 mm (0.25 inch) on the sides and rear. It used Bimetal steel which offered an improved protection to weight ratio compared to standard steel. The Bimetal armor offered around 1.8 times the effective thickness of an equivalent homogeneous plate against 7.62 mm ammunition, meaning the Urutu had an effective homogeneous thickness of 21.6 mm (0.85 inch) at the front and 10.8 mm (0.43 inch) at the sides and rear against 7.62 mm fire.

The hull was welded and angled at the front, with a minor angle at the sides and rear. The rear angle varied depending on the model, with earlier models having a triangular shape, while the later models had a flat rear. The rear door was operated by the driver or manually by the passengers. All Urutus had two side doors.

The driver was positioned in the front left of the vehicle, next to the engine. The engine was located in a separate compartment. The exact placement of the crew members is unknown, but based on other Urutus with similar troop transporting capabilities, it is likely that 6 soldiers would be located in the troop compartment and a soldier per side door, totalling 8 troops. The commander/gunner/loader was positioned in the gun/mortar turret.

The placement of the frontal headlights also varied with the hull version. Early versions had external headlights mounted on the upper front plate, while later versions had hull integrated headlights. Attachment hooks for towing cables were present in the front, sirens could be attached to the front sides of the hull. A stowage point for a towing cable was present in the left side of the vehicle, while, on some versions, the right side was occupied by the exhaust pipe. The Urutu was fully amphibious, although amphibious equipment such as propellers, rudders and snorkels were optional. A swimming vane operated by the driver was fixed to the top of the frontal hull plate.

The driver had a steering wheel and, depending on the version, would have a brake and gas pedal to the right side of the steering wheel. The gear shift for the automatic transmission was located on his right side and the instrument panel was located on his left side. The driver had 3 periscopes at his disposal, which could be upgraded to day/night periscopes.

Mobility

The Gun/Mortar Urutu was offered with 2 main engines in combination with various transmissions, although more options were possible depending on the client’s wishes.

Engine	Fuel	Horsepower	Torque
Mercedes OM352A (turbocharged)	Diesel	190 at 2,800 rpm	431 Nm at 1,800 rpm (318 ft-lb)
Detroit DDA 6V53N	Diesel	210 at 2,800 rpm	598 Nm at 1,800 rpm (441 ft/lb)

The engines were offered with a range of transmissions depending on the timeframe. From 1976 to 1980, it would have used a manual Clark transmission with 5 forward and 1 reverse gears, and an Allison MT-643 automatic transmission with 4 forward and 1 in reverse gears afterwards. Only the MT-643 could be paired with the Detroit engine. In addition, the Urutu used an Engesa 2 speed transfer case, which allowed the vehicle to be used in reduced and high gear. By putting the Gun/Mortar Urutu in reduced gear, it sacrificed horsepower for torque, making it more effective at climbing slopes. The vehicle also offered a power take off function for the propellers through the transfer case.

The Urutu had a maximum road speed of around 95 km/h and a maximum water speed was around 8 km/h. The Urutu also would have had access to a remote tire pressure control system to allow pressure regulation of the tires from within the vehicle.

Its gradeability was around 60%, with the maximum side slope being 30%. The Urutu had a ground clearance of 0.375 m (1.2 feet) and could cross a 0.6 m high vertical obstacle. It had an operational range of 850 km with a 380 l fuel tank. It could also be airlifted, much like all other versions of the Urutu.

The vehicle was 6 x 6 driven, of which the rear 4 wheels were part of the Boomerang suspension. The Boomerang suspension, in combination with the Engesa 2 speed transfer case, would enable the Urutu to cross challenging terrain and provide maximum traction in most situations. The power of the engine was distributed to a differential on the front side of the vehicle, and a differential in the rear. The rear differential drove the Boomerang suspension with a single axle, which is what makes it such an ingenious design.

Turret and Armament

It is unknown if the turret for the Gun/Mortar was made by Engesa or if they bought it from Thomson Brandt, which sold the mortars. Arguments could be made for both possibilities. The turret is not much more than a few plates welded together and a gun mount, something which Engesa would definitely be capable of building. The other perspective is that it was just a single prototype and that Engesa may have figured that they would design a turret themselves when they actually sold one. In either case, the turret seems to be very thinly armored. If the turret was designed by Engesa, it is possible that it was created from bimetal steel.

The turret was open-topped, with the gun/mortar located in the front middle. To the left of the gun, on the interior side, seems to have been some sort of gun laying device. The turret offered one sighting periscope with x3 magnification fitted to the gun mount. A 7.62 mm or .50 caliber pintle mounted machine gun was offered as an option as well.

The mortar could be both muzzle and breech loaded, with safety systems preventing double loading and a lock on the firing pin on an improperly closed breech. It was a smoothbore gun weighing 82 kg and with a maximum recoil force of about 17,000 N (1,700 kg). The recoil mechanism consisted of a large recoil spring which was coiled around the barrel exterior. The gun/mortar could provide direct fire up to 300 m and indirect fire up to 2,600 m while offering a gun depression of -15° and +75°.

The gun/mortar had access to high explosive, high explosive anti-tank, smoke, illumination, and canister ammunition. The vehicle had 82 rounds at its disposal and 2,000 7.62 or 600 .50 caliber machine gun rounds, depending on which armament was selected for the pintle mount, if one was bought in the first place.

Ammunition Type	Model	Performance	Muzzle Velocity	Range
High Explosive	Mle 72	–	205 m/s	2600 m
High Explosive Anti-Tank	60 mm CC	Up to 200 mm penetration	200 to 255 m/s depending on sources	500 m
Smoke	Mle 61	–	–	2050 m
Illumination	Mle 63	Minimum burning period of 30 s with a 150 m light radius	–	1700 m
Canister	60-132-C1	132 balls of hardened lead buckshot covering 25 m2 at 50 m	–	100 m

Fate

It simply seems that the large supply of the AMLs saturated the market and that countries were not interested in reducing the troop transport capacity from 12 soldiers to just 8. Especially the latter reason could cause issues with squad sizes within armies. In addition, it is unknown how many mortar rounds were on-hand in the one-man turret, but considering the size and the significant compromise with transportable personnel, it is thought to be very little. This would mean that the gunner would have had to leave his turret and get ammunition from the hull to keep on firing. Even worse is that the turret bustle slightly overhung the two frontal passenger top hatches as well, rendering them useless. The fate of the single prototype is unknown, but it is quite likely that it was reconverted to a standard Urutu or scrapped.

Conclusion

The Gun/Mortar Urutu was perhaps one of Engesa’s most pointless vehicles. It did not make much sense on paper, nor would it likely have been a good vehicle in reality. The compromises needed to make the mortar carrier work seem to have been too significant to get any buyers for the concept. Not only that, the French had spent about a decade before the Gun/Mortar Urutu appeared in flooding the African and South American markets with 60 mm mortar armed Panhard AMLs which were arguably more effective vehicles.

The Gun/Mortar Urutu seems to have been not much more than trying to chip in on an already saturated market by putting the armament on a decent platform. It almost seems that the only reason it really existed in the first place, is that it was cheap to make and it was an extra variant for the Urutu platform for the sake of having more variants.

Specifications EE-11 Urutu 60 mm Gun/Mortar
Dimensions (L-W-H)	6.15 (20’) , 2.59 (8’) , 2.7 m (9’)
Total weight	13 tonnes (14.3 US tons)
Crew	2+8 (driver, commander and 8 passengers)
Propulsion	Diesel Mercedes Benz OM352A-S
Suspension	Boomerang suspension
Speed (road)	Around 95 km/h (59 mph)
Operational range	850 km (528 Miles)
Armament	HB60 60 mm gun/mortar
Armor	Hull Front 12 mm (0.5 inch, Bimetal) at 70º Front (Lower Glacis) 12 mm (0.5 inch, Bimetal) at 30º Sides 8 mm (0.3 inch, Bimetal) Rear 8 mm (0.3 inch, Bimetal) at 10º Turret Unknown
Produced	1 Prototype

Sources

Blindados no Brasil – Expedito Carlos Stephani Bastos
Engesa’s Marketing Brochures
Engesa’s User and technical manuals for the Urutu and Cascavel
Personal correspondence with Ex-Engesa employees
Jane’s Armour and Artillery 1985-1986