Magnetic Compass Errors: Acceleration

today we will talk about the magnetic compass errors caused by acceleration as we mentioned in previous videos the magnetic compass is basically a magnet that is free to rotate about a pivot point and therefore since it has such a simple design it has certain inherent errors that pilots should be aware of these errors are magnetic variation compass deviation and magnetic dip which in turn can be divided into acceleration error and turning error in the last video we already talked about variation and deviation so in this video we will focus on the acceleration error however before going into detail with this let's see what is magnetic dip as we know a magnet always aligns with the flux lines of the earth's magnetic field and as we can see in this image these flux lines are parallel to the surface at the equator however as they approach the poles they become more vertical let's see it in more detail with this other example the planet's core will act as a giant magnet therefore this will create a magnetic field around it which is represented with this flux line the point at which this line leaves the planet is known as the magnetic south pole while the point where a tree enters the planet is known as the magnetic north pole if we observe and detail the flux lines of the magnetic field we can see that they have this pattern here as we can see in the equator the lines are parallel to the surface so we can say in other words that the force that orients the compass is completely horizontal while on the other hand at the poles these lines are very steep almost vertical so we can say that in this case the force that orients the compass is totally vertical at this point we might be wondering how does this affect a compass well we must remember that in essence a compass is a magnet free to rotate around a pivot point however in order to give the heading indication this magnet should rotate horizontally therefore to do so it requires the horizontal component of the earth's magnetic field so in other words it needs the horizontal force which is parallel to the surface not the vertical one with this in mind if we look at the previous example we can see that if we place a compass at the equator the magnetic force acting on it is completely horizontal since it is parallel to the earth's surface then the compass will rotate horizontally giving the heading indication properly however if we place the compass far from the equator and closer to one of the poles it will not only experience the horizontal force of the magnetic field but also a vertical component this vertical component will cause the magnet to tilt around the pivot point as we can see in this example in summary then if we put a compass on the surface of the equator it will only experience the horizontal component of the magnetic field so it will be completely balanced and will work correctly however if we place the compass closer to the north pole it will not only rotate horizontally but will also tilt due to the vertical component of the magnetic field this tilting of the compass is known as magnetic dip and as we just said it is not present at the equator since in this case the force is completely horizontal therefore we can say that in the equator the compass indication does not experience magnetic dip errors now if we are at any point between the equator and one of the poles the magnet will tilt due to the vertical component of the magnetic field and although in this position the compass can still rotate horizontally this tilting will produce errors in the compass indication under certain flight conditions such as accelerations or turnings in this video we will focus on the acceleration error so let's get started the thing is that when accelerating or decelerating the inertia combined with the magnetic dip will cause the compass to show an erroneous heading indication temporarily but in order to understand why this happens let's see the next example here we have a compass at the equator which is completely balanced in this case the center of gravity of the magnet is aligned with the pivot point so the compass reading will not be affected by acceleration or deceleration however if the compass is placed in the northern hemisphere the magnet will tilt due to the magnetic dip effect and here as we can see the center of gravity is no longer aligned with the pivot point now although what really happens is that the whole magnet shifts to one side if we see it from a top point of view we would see as if the center of gravity of the magnet shifts to the blue side so with this in mind let's see what effect this has on the compass indication in the northern hemisphere when flying on a west or east heading the inertia caused during acceleration will cause the compass indication to deviate slightly to the north and the opposite happens during a deceleration in this case the inertia will cause the compass indication to deviate slightly to the south but let's see why this happens here we have an aircraft flying to the east with heading 0-9 or zero as we can see inside the compass we have the magnet with the center of gravity shifted towards the blue side due to the magnetic dip so in this situation if the aircraft accelerates inertia will pull the magnet's center of gravity backward causing the compass to give a false turn indication to the north although the aircraft is actually still flying on the same heading this effect will occur as long as the aircraft continues to accelerate since once the acceleration finishes and the aircraft flies with a constant speed again the inertia will disappear and the compass will gradually return to the correct heading indication and the opposite happens if the aircraft decelerates in this case inertia will pull the magnet's center of gravity forward causing the compass to give a false turn indication to the south now again this will happen as long as the aircraft continues to decelerate since once the deceleration finishes and the aircraft flies with a constant speed again the inertia will disappear and the compass will gradually return to the correct heading indication exactly the same effect occurs when flying to the west in this case with heading 270 here if the aircraft accelerates the compass will give a false turn indication to the north and once the aircraft stops accelerating and maintains a constant speed the inertia will disappear and the compass will return to the correct heading indication if the aircraft decelerates the compass will give a false turn indication to the south and once the aircraft stops decelerating and maintains a constant speed the inertia will disappear and the compass will return to the correct heading indication so far we have seen what happens if the aircraft flies with a west or east heading but let's see what happens if the aircraft flies with a north or south heading well in this case inertia will not affect the heading indication so in other words there will be no errors when accelerating or decelerating this happens because the center of gravity the pivot point and the inertia are aligned with each other so the magnet has no tendency to rotate to either side in summary then this effect is greater when flying on a west or east heading and in the northern hemisphere when the aircraft accelerates the compass indication deviates slightly to the north while when the aircraft decelerates the compass indication deviates slightly to the south we can easily remember this with the acronym ends which stands for accelerate north decelerate south now it is important to mention that the magnitude of this acceleration error will depend on the latitude and how fast the acceleration or deceleration is so far we have seen what happens in the northern hemisphere let's now see the case of the southern hemisphere again we know that at the equator the magnetic field force is totally horizontal and therefore the center of gravity is aligned with the pivot point however in the southern hemisphere the magnet will tilt like this because of the magnetic dip effect and as we can see if we look at the top view the center of gravity is shifted to the red side of the magnet so it is the opposite of what happened in the northern hemisphere where the center of gravity was shifted to the blue side this implies that the errors due to acceleration will be opposite let's look at the examples in the southern hemisphere when flying on a west or east heading if the aircraft accelerates inertia will cause the compass indication to deviate slightly to the south and if the aircraft decelerates the compass indication will deviate to the north so here for example we have an aircraft flying to the east with heading zero niner zero and inside the compass we have the magnet with the center of gravity shifted towards the red side due to magnetic dip here if the aircraft accelerates inertia will pull the magnet's center of gravity backward causing the compass to give a false turn indication to the south although the aircraft is actually still flying on the same heading this effect will occur as long as the aircraft continues to accelerate since once the acceleration finishes and the aircraft flies with a constant speed again the inertia will disappear and the compass will gradually return to the correct heading indication on the other hand if the aircraft decelerates inertia will pull the magnet's center of gravity forward causing the compass to give a false turn indication to the north now this will happen as long as the aircraft continues to decelerate since once the deceleration finishes and the aircraft flies with a constant speed again the inertia will disappear and the compass will gradually return to the correct heading indication the same effect is present if the aircraft flies to the west in this case with heading two seven zero in this situation if the aircraft accelerates the compass will indicate a turn to the south this will happen until the acceleration finishes then the inertia disappears and the compass returns to the correct heading indication now if the aircraft decelerates the compass will indicate a turn to the north until the aircraft stops decelerating and maintains a constant speed then the compass will return to the correct heading indication and just like in the northern hemisphere if the aircraft flies with a north or south heading inertia will not affect the heading indication which means that there will be no acceleration or deceleration errors since the center of gravity the pivot point and the inertia are aligned with each other in summary then this effect is greater when flying on a west or east heading and in the southern hemisphere when the aircraft accelerates the compass indication deviates slightly to the south while when the aircraft decelerates the compass indication deviates slightly to the north we can easily remember this with the acronym sand which stands for south accelerate north decelerate and just like in the northern hemisphere the magnitude of this acceleration error will depend on the latitude and how fast the acceleration or deceleration is now something important to mention is that these northern and southern hemispheres are determined in relation to the magnetic equator instead of the geographic equator and as we can see in this image they do not always match and therefore we must highlight that the effects caused by the magnetic dip will depend on the position in relation to the magnetic equator not the geographic one we can see more clearly the distribution of these hemispheres in this image here the green line represents the magnetic equator the blue area corresponds to the magnetic northern hemisphere and the red area to the magnetic southern hemisphere i hope the information presented in this video was useful if so don't forget to share like subscribe and leave a comment down below thanks for watching [Music] you

Channel: Aviation Theory

Views: 30,120

Keywords: Aviation Theory, Aviation, Airplanes, Instruments, Navigation, Aerodynamics, ATPL, CPL, PPL, Tutorial, Explanation, Pilot, Aircrafts, Knowledge, Magnetic, Compass, Errors, Acceleration, Turning, Deviation, Variation, Heading, ANDS, SAND, UNOS, ONUS, Part 2, Deceleration

Id: UvhooB--P2s

Length: 13min 15sec (795 seconds)

Published: Wed Jun 02 2021