Hi Airbourne
The VOR is a command instrument when the OBS and the DI (compass) are in agreement - this is useful when tracking directly TO or FROM the VOR. However the concept of
command and
reverse command is not that helpful when try to orientate yourself relative to the aid.
Getting back to Q21, this is the type of problem that needs to be performed in the cockpit in real time - there is no time or room for pencil and paper - that being said pencil and paper is a good way of solving the problem in an exam environment.
That being said, here is what is presented to you in the cockpit when you are told to track 090M inbound - how do I do it? You use your imagination!
Step 1 - see diagram
Imagine that the VOR station is at the centre of the VOR dial. The outside compass rose now shows the VOR radials.
Step 2 - where am I? (see diagram)
If the TO/FROM indicator shows TO you are below the horizontal CDI dots. If the TO/FROM indicator shows FROM your are above the CDI dots. Now since the CDI is centred with a FROM indication we are somewhere on the 290 radial - see blue aircraft on diagram. Next read the DI heading of 050M and turn your imaginary blue aircraft onto a heading of 050M using the VOR compass rose - you don't have to be exact.
Step 3 - where do I want to go? (see diagram)
You are told to track 090M inbound - ie to track in on the 270 radial. The radial that you want is to your right so turn right onto heading 090+30 = 120M.
When on a heading of 120M set the OBS to 090 - the instrument is now a command instrument.
I hope this helps. This is how you do it in the air and this is how the HSI does it.
