Harrier jump jets.

Originally posted by Now_Then

Yep, but something a lot of people overlook is that Harriers cannot hover for long periods, the engine gets very hot (a jet engine with no airflow? it's gonna blow up!) So the Harrier carries water in a tank and injects it into the engine, of course the flow rate can be adjusted but at full flow the Harrier can only hover for 90 seconds!

They can hover longer than that though, I suppose it depends on the conditions and such, maybe it can only hover for 90 seconds in dry dessert heat but cooler damper air maybe 5 or more minutes.

The distilled water is mainly used for adding extra thrust to the engine exhaust (see water injection - water expands quicker than air, and is heavier, so expelling it through the exhaust adds a significant amount of extra thrust), allowing for hovering at higher weights, and is limited to 90 seconds of use. At lower weights the Harrier can hover for several minutes - it was not unusual to see Harriers hovering for up to five minutes alongside the carriers in the Falklands war while they queued to land.