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When piloting a Harrier or F35 can the pilot just hover at will?

Or is this possibly something that will eat up lots of fuel, and should only be done when planned? (like for landing)

Is spontaneously hovering even a thing? There are some media-depictions of these planes doing it (F35 hovering in Die Hard 4, Harrier hovering in True Lies, Harrier in Metal Gear Solid 2, etc)

I remember an article saying something like "VTOL takeoff is avoided, as then the plane needs to be air-refuelled immediately", but I haven't been able to find a good source for this.

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    $\begingroup$ Just FWIW, "at will" and "spontaneously" are kinda odd choices of wording here... Like asking if a pilot can spontaneously, or at will, slow down and lower the flaps for landing. It isn't totally clear what your confusion might be, but you have a good answer already so maybe I'm just being picky. $\endgroup$ Jun 17, 2023 at 18:29

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There are weight limitations associated with hovering and vertical landings. The F-35B, as I understand it, requires a A/C gross weight under 40,000 lbs in order to safely do this. This roughly translates to no stores aboard the airplane, as well as an internal fuel load of only 40% or so of total capacity. Harrier variants will have similar restrictions as well in regards to when a vertical takeoff or landing may be performed.

As the airplane will be operating close to full thrust during hover and/or vertical landing, it is consuming fuel at a great rate, so hovering operations are limited, generally only do a couple of minutes during final approach and landing during shipboard operations. At terrestrial airports, the F-35B and Harrier generally perform conventional landings. I also know, at least in the case of the F-35B, there are concerns about using the vertical lift system at terrestrial airports due to the risk of hot exhaust gas either cracking or damaging runways or parking aprons.

Due to the complexity of the lift fan system, an F-35B does not use it for anything aside from STOVL operations. There may be speed limitations as well with engaging the lift fan system on that aircraft, possibly somewhere in the area of below 250 KIAS. Harriers, however, could use nozzle position during all aspects of flight, including combat. Marine Corps tests performed in the 1970s in both computer simulations and on actual aircraft revealed the potential for using VIFF (Vectored thrust In Forward Flight) for both offensive and defensive maneuvering of the jet.

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VTOL pilots (and helicopter pilots) also prefer to avoid hovering unless necessary for another reason: safety.

Since the aircraft is operating at or close to 100% power output, if something in the propulsion system is going to break, it is more likely to break when under the greatest stress.

And when hovering, the pilot has the least number of options to deal with a loss of power problem, as they are entirely dependent upon the engine(s) for control.

Generally speaking, helicopters and VTOL aircraft get into forward flight as soon as possible, and stay there as much as possible, as it reduces fuel consumption, reduces stress on the aircraft, and gives the pilot more time and options to deal with a potentially fatal problem.

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