Winter is time for training. With low visibility and unpredictable weather, long trips in VFR are uncertain business. Staying on the ground is not an option, staying close to the airport is a compromise. I’m using the occasion for some navigation training. My plan today is a simple triangle to a near by VOR and back.
The air is cold and the plane is light. “Kilo Sierra” is eager to get of the ground.
The first leg is easy. I have dialed in the VORs frequency in the navigation radio. On the “Omni Bearing Indicator” (OBI), I turn the dial until the indicator needle moves into the center at around 140°. That is the course to the VOR.
The way is not very far and after about 15 minutes I am near the VOR. Directly over it, there is no reception. The NAV flag on the instrument comes up to indicate bad reception, so I know that I have reached the waypoint.
Now comes the second part. I turn the OBI to my new course, bank “Kilo Sierra” to the left and watch the directional giro turn slowly. The “to” flag on the OBI switches over to “from” and I am on my way. On this leg I don’t have a physical way point. I will request my bearing from the airport to determin the turning point.
I’m flying a triangle. From the airport I flew south-east to the VOR. From the VOR I’m flying north-east to my next way point. And from there I am planning to fly south-west, heading 230° for approach into runway 23. So my next turning point will be when my bearing to the airport is 230° (or a bit before as the airpane needs time to turn).
Todays flight is a training mission. I know the area and I have a pretty good idea of where I am. After the calculated time I see the town that is close to the mark on my map for the turning point. I start calling the airport “Delta Kilo Sierra, requesting QDM”.
“QDM” means the the magnetic heading from the aircraft to the airport. There are many “Q-codes”. Their origin is marine morse code, when brevity was key. The most common one for aviation is “QNH” which is the local atmospheric pressure calculated to mean sea level.
“270″ is the somewhat expected answer from the tower. I am 40° away from my desired course. After a few moments I ask again. “262″ is the instant reply. The radio operator at the airport has a large display for “QDM” and its counter part “QDR”, the magnetic heading from the station. With every transmission from an aircraft, the display lights up and shows the direction the aircraft is in. A very helpful tool for the small airport which does not have radar vectoring.
I am close to the airport so the degrees go fast. I decide to start my turn onto the desired course of 230°. When I am on course, I ask again for the “QDM” to confirm the heading. “226″, almost perfect.
Back on the ground I taxi to the apron and park “Kilo Sierra” next to another Cessna. An instructor I know is near by, his student is doing the pre flight. He smiles at me “I was wondering who it was requesting ‘QDM’ on a clear day like today”. I smile back “It was hard work trying not to see the airport from where I was”. The instructor looks at his student “Beautiful day for some navigation practice, don’t you think?”
To be continued…
(originally posted on March 13, 2014 by tilbo at aloft.blog.com/navigation-training/)