The "Shamal" sandstorms in the Persian Gulf are northerly winds that are particularly brisk in the Spring. Coming in at over 70 kilometers an hour, they make the use of helicopters dangerous and dropping paratroopers impossible. Fixed wing aircraft are also at risk, because the fine dust that becomes airborne can get into engines in sufficient quantities to cause engine failure. The dust us so thick that visibility is severely restricted, making landings very dangerous. The rest of the year, the Shamal (meaning "north" in Arabic) winds are a milder and rather pleasant. But when they speed up in the Spring, and turn into sandstorms, they mean trouble for anything that flies.