A bit late in the reply, I had to chat to somebody about it, but to clear up a question.
(Why did our Merlins have to be "tropicalised", while the big American (and British) radials just took it in their stride?)
It's matter of construction. A Merlin is a twin block water cooled engine and if it starts to wear out because of dust ingestion then it has to be rebored or re-lined. This is almost a factory job so if the facility is more than a few hundred miles away then it comes under the heading of 'far too difficult' and is scrapped.
A radial engine is different. It has all the cylinders bolted to a central crankcase so if one goes pearshaped; usually the one behind the CSU; you just change it. New ones come complete with a lapped piston in shopping bag sized boxes to you can sling a dozen or so in the back of a jeep. If some of your pilots keep blundering into trees with nearly new engines you can recover a few pots as spares. Two blokes can do a fourteen pot change in a day, in situ, so dust erosion is not such a problem.
They still use filters. Not fixed wing as they generally operate from concrete and those that operate from dirt do so singly so the dust is blown behind. Helicopters have to use them in those conditions because of compressor erosion. They used to be paper filters like a car engine intake but now they use particle seperators. They are corkscrew shaped bits that force the air to violently spiral and throw out all the crud. The Dyson vacuum cleaner uses the same principle.
They still haven't found out a way of filtering the dust so you can see where you are going.