posted by Krysten on .
Your airplane leaves 20 degrees north (linear velocity = 845 nm/h), heading to a point due north at 25 degrees north (linear velocity = 815 nm/h). You set the autopilot for due north and go to sleep. If your flight time is 30 mins, how far off in what direction are you if you take no corrective action?
20 degrees north? Normally it should be north of east, east of north, west of north or north of west.
heading to a point due north at 25 degrees north is sketchy too.
I think maybe the 25 and 20 are latitude and we are talking about Coriolis?
A point on earth is moving faster East at 20N than at 25N
Therefore if you head true north. You will end up Eats of the longitude you started out. (Likewise a parcel of air headed toward a low pressure to the North will end up East of the low in the Northern hemisphere. South motion ends up west. So hurricane is counterclockwise)
That clears it up
Yes it's coriolis I'm talking about. I'm still somewhat confused. Im understanding in what directiion the plane is off but how to I calculate the distance the plane is off?
So the question is really asking how fast a point at 20 N moves east due to earth rotation.
That is about 360*60 = 21600 nautical miles in 24 hours times cos of 20
East speed = 21600*.94 nm /24 hr = 845 nm/hr. WE MAINTAIN THAT EAST SPEED because we are now in the air not touching earth.
That is where that came from.
Now if you used cos 25 I suspect you would come out with the 815 given
Now in half an hour you move 845/2 = 423 miles East
BUT the point you headed for only moved 815/2 = 408 nm East
so we end up
423 - 408 = 15 nm East of our landing field.
Calculate the Coriolis acceleration and see what sideways deviation it makes from the desired path during the flight, when using flat-earth non-rotating coordinates.
Deviation = (1/c)*a_c( t^2
Where a_c is the Coriolis acceleration
You could also do it the way Dr WLS said but the question gave you those two east speeds so you might as well use them.