Why do helicopters/choppers need to do circles in the air before landing?
In: Engineering
Even if helicopters are capable of hovering and translating backwards or side to side it is much easier for the pilot to move forward as this provides much better viability over where they are going. So it is much easier to do circles over the landing site as you do your final preparations then it is to stop and hover. These final preparations includes slowing down to landing speed as the helicopter still have quite a lot of momentum, checking for any obstacles in the landing area like tree branches, wires, fences, people or animals, checking the wind direction, speed and conditions as well as configuring the helicopter for landing. Once the helicopter is ready for the final landing it is also easier to do so while still moving forward. And to reduce the relative speed to the ground and prevent the wind from blowing them off the landing area they will try to land against the wind. So you might see a helicopter do a couple of circles above their landing site before landing, once to prepare for landing and observe the landing area and once to do final checks and get into position for landing.
Circling is the most compact (in terms of land overflown) was to descend. You can go down more quickly than just down-hovering. As an added bonus is allows the pilot an excellent opportunity to scan the landing zone for obstacles and convey to people (and animals) on the ground where some helicopter stuff is about to occur so they can clear out.
They don’t, but it’s good practice to overfly the landing zone to get a good look at it, make sure it’s clear, and get an idea of the wind.
uh?
they dont, at least not for any major technical reason. if anything a a practice for pilots to survey the landing Area to make sure its clear.
there is a small technical aspect they might wanna do this but its not major unless its an emergency, since its merely the fact the helicopter is setup in a way there the pilot has a lil more mobility when moving forward than if they just hover down so they might circle around while descending, this is by on means necessary but it speeds up the landing process.
You don’t want to be standing still (hovering) at low but non-trivial altitudes in a helicopter.
When a helicopter loses power it can do something called “autorotation”, which basically uses the force of air moving through the rotor to force the rotor to turn. The problem is this doesn’t work very well unless you have significant forward speed. So if you’re hovering at say 100ft and lose power it’s possible to hit the ground at a potentially fatal velocity. [The specific altitudes/velocites required by a helicopter are reported in a helight-veloicty diagram](https://en.wikipedia.org/wiki/Helicopter_height%E2%80%93velocity_diagram). This means it is in the helicopter pilots interest to maintain forward air velocity at low altitudes.
So if the pilot has a reason to hang around the landing area while not in the actual process of landing (like say checking wind directions, or verifying that the landing area is clear) the slow circling is the safest way to operate at low altitude while also remaining in the area of the landing pad.
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