Prepping for IR checkride - questions

Ross Oliver wrote:

Matt Whiting wrote:

Your flight instructor doesn't understand very well how a VOR
transmitter works. The cone of confusion gets larger with increasing
altitude. If you fly over the VOR about 50' above it, then the
deflection would be for "just an instant." If you fly over at 10,000
feet, the full scale deflection can last for quite some time (several
seconds at least), depending on how fast an airplane you are flying.



If you are getting full scale deflection then you are not in
the cone of confusion. You are also not passing directly over the
station. The cone of confusion is the volume directly over the
station where there is no VOR signal. That's why it's called the
cone of confusion. If you are getting a signal, then you should
not be confused.

The goal should be to go from a needle-centered TO indication, to a
no-signal flag for 1-2 seconds, to a needle-centered FROM indication.
There should not be any full-scale swing of the CDI needle. While
this is challenging and takes practice, it is by no means
impossible. Autopilots do it all the time.

Every VOR I've flown has a needle the swings wildly from side to side or
goes full-scale to one side when crossing a VOR. Doesn't matter how
precisely the VOR is crossed. The off flag appears as well, but the
needle doesn't just sit in the donut through all of this. Maybe you'll
believe the Air Force.

http://www.vusaf.org/aetc/documents/VOR%20MANEUVERS%20_PART%202.pdf#search='vor%20cone %20of%20confusion'


Matt

Matt Whiting wrote:
Every VOR I've flown has a needle the swings wildly from side to side or
goes full-scale to one side when crossing a VOR. Doesn't matter how
precisely the VOR is crossed. The off flag appears as well, but the
needle doesn't just sit in the donut through all of this. Maybe you'll
believe the Air Force.

http://www.vusaf.org/aetc/documents/VOR%20MANEUVERS%20_PART%202.pdf#search='vor%20cone %20of%20confusion'


From the referenced document:

The cone of confusion is an area above the station where the signal
from the antenna is not receivable and therefore is not reliable.

So, yes, I do believe the Air Force. Show me a CDI that does not center
the needle when the VOR signal is lost.

I also challenge your claim that the needle will swing "wildly from side
to side." Passing slightly abeam the station will cause the needle to
go full deflection in one direction and stay there until after station
passage. In a properly functioning CDI, there should be no side-to-side
swinging.