An armoured vehicle designed to withstand two simultaneous blasts from anti-tank mines failed to save the lives of six Canadian soldiers killed Wednesday when their RG-31 Nyala patrol vehicle hit a roadside bomb in southern Afghanistan.
An Afghan interpreter was also killed.
Canadian soldiers in Afghanistan have long regarded the four-wheeled armoured truck as the ultimate protection against such attacks.
Over the last 18 months, Canada has purchased 75 RG-31s at a cost of about $91 million.
The sturdy vehicle, built by a South African subsidiary for the British defence giant BAE Systems Inc., can carry up to 10 passengers and a driver.
The RG-31 has become widely used by the United Nations and the U.S. army. Canada received its first fleet in March 2006.
But some experts have questioned whether the vehicle could stand up to roadside or car bombs, as improvised explosive devices in Afghanistan appear to have become more powerful.
Until the latest attack, troops riding in the vehicle had often survived roadside blasts with minor or no injuries.
Four Canadian soldiers credited the Nyala RG-31 with saving their lives in a suicide attack last September. The vehicle was damaged, but the soldiers inside it were unscathed.
Some, however, have not been so lucky.
Trooper Mark Wilson of the Royal Canadian Dragoons was killed last October as he rode on a Nyala truck that hit a roadside bomb in southern Afghanistan.
The force of the explosion penetrated the vehicle's thick armour and a shield designed to deflect blasts, killing Wilson who was riding in the gunner's seat. The other soldiers inside the vehicle survived.
In the Nyala, the gunner operates a machine-gun remotely from inside the cabin.
The RG-31 has hulls shaped to deflect blasts from below.
Usually, this means a V-shaped bottom with a minimum of angles, allowing the blast force to "flow'' unimpeded past the structure. Parts of the vehicle likely to be in the path of the explosion are designed to be sacrificed _ wheels and axles are easily blown off, but such running-gear parts can be readily re-attached.
The RG-31 became a battlefield necessity as it became clear to the army in late 2005 that it would need a better protected patrol vehicle than the lightly armoured Mercedes G-Wagon it was using.
However, the Nyalas have seen their share of wear and tear.
Army records show that at the height of fierce fighting in Afghanistan last summer, more than a quarter of the RG-31 fleet were in the shop with maintenance problems. The vehicles had a series of electrical and software glitches, many relating to the roof-mounted remote-controlled machine-gun.
Nyala maintenance logs, obtained by The Canadian Press under the Access to Information Act, show the vehicles arrived with a series of minor defects.
Records show that between mid-June and mid-July last year, 13 of the 50 Nyalas -- some with as few as 550 kilometres on them -- were deemed "non-mission capable'' by the army.
The ratio has since improved, with only one or two of the current complement of 75 RG-31s down for maintenance at any time.
In May, the Defence Department signed a deal with a U.S. defence contractor to acquire 10 Buffalo and Cougar mine-protected vehicles -- five each -- for Canadian troops in Afghanistan.
Unlike, the Nyala, the new trucks have no windows and are capable of carrying more troops and equipment.
They are expected to be delivered in August and are destined for duty in Afghanistan.
