The Wrong Type Of Sand:
UK MoD Penny Wise, Pound Foolish?- One of the 'Lessons Learned' from the joint Omoni-UK "Swift Sword II" exercise was articulated by Chief of General Staff General Sir Michael Walker, who at the end of October 2001 reportedly said that the "wrong type of sand... rather like talcum powder" brought a Regiment of "Challenger 2" main battle tanks to a halt when it clogged their air filters.
The British MoD made a conscious decision to send the 67 Challengers of the Royal Dragoon Guards and Queen's Royal Lancers fitted out for European operations, with the expectation that the crews would simply have to change the filters more often. The MoD expected 48 to 24 hours out of a filter and actually got as little as 6-7 hours (or 4, in some cases). Replacement air filters were taken along, but these wore out in the harsh conditions sooner than anticipated.
The MoD apparently had the option to equip the British tanks sent on "Saif Sareea II" (Swift Sword 2) with the same filter system as the Omani Challenger 2. The modification to increase filter life would have been far cheaper than the cost of the regular replacement filters that were required. Just the desert filter alone was 1300 and the entire conversion kit would have been even more expensive. The 2.5m UK Challengers also suffering extensive damage to their road wheels and track pads.
This is not the first time in history that British tanks have had problems with clogged filters. Supposedly, in the mid 70's all the UK's "Chieftain" MBT fleet was grounded due to dust getting into the engines through the filters. One unit had just deployed and were stuck on the training area for two weeks without tanks.
The Omani Army's Challengers (which were fitted with the desert use filters) supposedly performed far better during the exercise - Adam Geibel