Recently a frifinish asked me why the police helicopter was constantly circling over his home in the middle of the night. He asked why they didn’t just fly earlier and also forth or hover up high. As a chopper pilot, tbelow are some excellent factors why we circle.
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Helicopters use much less power to fly at 60 knots in a circle over a location compared to the power compelled to hover. This permits for much longer time on terminal and also gives the residents or pilot an entire 360° view of the scene to film, observe or recon prior to making a strategy to land.A few of these these might start to make a tiny feeling so now lets look at the details of why helicopters circle rather than perform somepoint else.
Why Do Helicopters Circle Overhead?Police and news helicopters are the two a lot of common forms of helicopters that you might have viewed circling your home or surrounding and also the reason for those 2, in certain, is because tright here is something of interemainder on the ground that the human being on board wish to view.When the object in question is stationary, prefer a road web traffic accident, or addressed, like a structure or item of land also, the finest means to store that object in check out at all times is to circle or orlittle roughly it.Most pilots will certainly set up an orlittle at roughly 500ft over the object and fly approximately 60 knots(kts) airspeed. This gives an altitude that is high enough to be able to plainly watch the object by eye, while keeping a safe elevation over the object.The direction in which the helicopter orbits counts on who is wanting to check out the object. Many passengers in a helicopter will sit on the left-hand side of the aircraft, so if they are the ones wanting to watch the object, then the pilot will do orbits to the left or anti-clockwise to offer them the optimal see.If the aircraft has a camera placed on its nose then a good majority of the moment the pilot is the one wanting to see the object to be able to store it in sight, so they will certainly fly the orlittle to the appropriate. This helps the video camera operator save the shot framed with minimal work bereason the pilot is able to quickly store the object in sight.
Why Does A Helicopter Circle Before Landing?Circling in a helicopter is the best way to view an area from all sides to look at the landing spot. When a helicopter pilot is landing at an unall set area like a baseball diamond, city park, or even a hole in the trees out in the remote parts of the nation, they need to look and also assess a number of factors:Wind – Landing into the wind is the desired option, but will the approach route in and out of the landing website be clear of objects to facilitate this?Wires – Are tbelow wires throughout or near the landing spot. Pilots typically look for supporting frameworks prefer poles or towers as wires can be impossible to view at timesObjects – Trees, towers, structures, people, debris. Are any type of of these in the means in the time of approach, landing, or departure?Sun – Will the glare of the sun on the home window obscure vision once approaching to land?Shape – What is the form of the clear location to land, lengthy and also skinny or wide open? This can dictate the direction of strategy to landSlope – Is the ground sloping where the pilot desires to land. Many helicopters have actually between a 5-10° slope landing limitationLanding Spot – Is the landing spot clear of obstructions, debris, people etc
All of these factors must be assessed before the pilot formulates the best setup to safely technique, land, and also decomponent the spot. The simplest means the pilot have the right to perform this is by using 2 orbits:High Orbit – Typically 500ft over the spot to look for the primary objects, asses wind, and also look at the strategy and departure pathsLow Orlittle – Generally 100ft – 200ft above the spot for last observations of the specific landing pointA excellent, experienced pilot deserve to execute all of this in 1-2 orbits while descfinishing to begin the technique. Many orbits will be done clockwise as a lot of helicopter pilots sit on the appropriate side of the helicopter. This will provide the pilot the finest view of the whole location.Flying an orlittle likewise helps to views feasible covert obstacles. Shadows and also sunlight deserve to really hide objects from up high and also depth perception have the right to be extremely obscured. By taking the time to circle the landing spot, the pilot gets the best opportunity to discover anything that could reason them troubles when on last approach.
Circling Vs HoveringThe one point that renders helicopters distinct is that they can hover. They deserve to hover numerous feet off the ground or, if enough power is easily accessible they have the right to hover countless feet in the air – So why don’t pilots just hover to look at a spot or object?
HoveringHovering have the right to be an excellent way to check somepoint and also the main ways that hovering is offered rather of orbits are:Tall Buildings – When trying to look dvery own right into the street that is surrounded by tall structures a high float is a far better choice. If a helicopter orbits, the neighboring structures deserve to block the watch.By maneuvering the helicopter right into the best stationary position it enables the object to be observed easily.Limited Airspace – When many type of news helicopters like to cover an event the pilots have the right to talk to one one more and each organize their place. I experienced this take place at Boeing Field close to Seattle once 6 news helicopters all sat hovering to the sides of the runmethod once the brand-new Boeing 787 Dreamliner flew in for the first time.By doing this, Air Traffic Control allowed them to get closer and each news channel got a perfectly clear swarm of the technique and landing of the airplane.
CirclingHere are the the majority of common determinants why flying an orbit at approximately 60 kts airrate is done in a helicopter:Power Required – Hovering a helicopter needs the most amount of power from the engine/s, especially as soon as they are around 20ft-60ft above the ground. By flying at 60kts it calls for the least amount of power from the engines, hence reducing fuel usage.
A Usual Helicopter ‘Power Required Curve’
When the helicopter is at a slow speed the rotor system hregarding produce all the lift just from the engine power. As the helicopter starts to acceleprice the major rotor mechanism starts gain a hand also from aerodynamics and the power required to save the helicopter flying reduces.At 6o knots this is when the power forced to fly is at its lowest. Once the helicopter goes past this rate, drag on the aircraft begins to call for even more power to get rid of it and press the helicopter with the air.By flying orbits at 60 knots it permits the helicopter to usage the least amount of power, which indicates the least amount of fuel burn, hence the pilot is able to reprimary on scene much longer than just sitting tbelow in a float.
H/V DiagramThe H/V or Height Velocity Diagram is a diagram issued by the helicopter manufacturer that tells the pilot when a helicopter can be landed safely if their engine were to sheight. This diagram is based on elevation over the ground and airrate.Height and airrate are the two finest friends to a pilot in an engine faiattract case and having both are great but what if you just have one…If I have actually lost you, simply hang in tbelow and also I will certainly explain:If the aircraft is low and sluggish when then engine falls short then the possibilities of the helicopter making a safe autorotation landing are slim.If the helicopter is low and fast and the engine quits the pilot may be unable to slow the helicopter down in time prior to it sinks and also contacts the ground.
In the diagram above, to avoid these scenarios, the pilot will certainly acceleprice to approximately 50 knots while remaining 5-10ft above the ground then start to climb ameans. By doing this the pilot stays clear of the red ‘Avoid’ areas.So exactly how does his apply to a circling helicopter? One of the concerns my friend asked was why not just hover? In the diagram, to hover (0kts) the helicopter would certainly have to be over 800 feet high to be able to make a safe autorotation landing, and that’s offered tbelow is an open location pretty close by.By circling approximately at 60 kts the pilot does not need to worry around the H/V Diagram and if the engine were to quit, the best autorotational speed for a lot of helicopters is 60 kts, which they are currently at. Tright here may additionally be even more chances of finding an open landing area as the forward rate they have permits them to cover even more distance throughout the glide.
To FinishThe primary factors why helicopters circle overhead are to burn less fuel and continue to be on terminal longer, provide the citizens the best view of the scene, and to save the helicopter in a safe flight problem if the engine were to ever before quit.It is likewise a lot much easier to fly in a stable orlittle at 60kts than attempt to preserve a high float without visual recommendations to let the pilot know if they are drifting or transforming elevation.
Further Reading:If you uncovered this post amazing and also would certainly like to store analysis, I highly recommend the adhering to posts from my blog:Can Police Helicopters Detect Grow Operations? Worried?!This is What Police Helicopters Actually Do!This Is Why Helicopters Are So Loud! A Pilot Weighs in!Do Helicopter Pilots Wear Parachutes?This is Why a Helicopter MUST Have 2 Rotors, or Does It??
Rick JamesI am an aviation nut! I"m an ATP rated helicopter pilot & former flight instructor through over 3000 hours spanning 3 nations and many kind of various flying jobs. I love aviation and whatever about it. I use these write-ups to pass on cool facts and indevelopment to you whether you are a pilot or simply love aviation too!If you want to recognize more about me, just click on my picture!
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Hi, I"m Rick James and I am an aviation nut! I"m an ATP rated helicopter pilot & previous trip instructor through over 3000 hours spanning 3 countries and also many type of different flying work. This website was created to help pass on indevelopment and also expertise of all things aviation!About Me
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