O Airport Where Art Thou?

O Airport Where Art Thou?

Visibility: not great, about 3k
Temperature: -2°C
Wind: 070°, 7 knots
QNH: 1020hPa
Location: EDAZ (Schönhagen)
Equipment: D-EKKS (Cessna 172N)

My new license has arrived more than a week ago and is still unused. The sky has been gray for weeks and I am ground-sick. Today the clouds are slightly higher and there is only moderate snow in the forecast for the afternoon. So I am off to the airport to see what is possible.

The target for the day is EDAZ, Schönhagen. It is a nice airfield south of the big city and about 40 minutes away from the home base. I do a quick flight plan-gestimation and am off. The visibility is not great, the ceiling is at about 2500 feet. There are patches of blue visible every now and again.

The radio beacon in Fürstenwalde (FWE VOR) is my waypoint. I fly on its radial 250° towards Schönhagen. The ground is snow covered. Lakes are frozen, from above it is difficult to tell them from meadows. Navigation by ground reference is very limited.

I use radial 305° of the KLF VOR as cross reference. The airport should be at the intersection of the two radials. EDAZ is located north of a little village and surrounded by forrest. I watch the needle of the second VOR slowly move to the middle and start looking for the airport. I have drifted a bit to the south but how bad can it be, really.

When I think I should see the airfield any minute now, I call in and announce my location, altitude and intention. Runway 07 is in use, there is not much going on on the Schönhagen frequency.

A few more moments pass and I still don’t have the airport in sight. The KLF needle is in the center now and the FWE needle is about 2 degrees to the right. Not a big deal as I want to enter the traffic pattern from the south anyway. I look ahead and to the right and I can only see gray sky and white ground. I turn a bit to the north and keep looking. I don’t want to accidentally get too close to the traffic pattern. I watch for a runway and wrestle down a slight feeling of uneasiness.

A few more minutes pass. The needle of the KLF VOR has moved out of the center again. I start thinking about options. What if I don’t find the airport?

I have fuel for about three hours – no problem here
Engine instruments are looking good – no reason to worry
I can simply fly back to the FWE VOR and go back home from there – safe exit strategy
I don’t have to pee – no need to hurry

Aviate, navigate, communicate

My situation is annoying and a bit embarrassing but not dangerous. I am at a safe altitude and I have enough fuel. So I start checking my map for a good point of reference. I did not take the approach chart with me and I start regretting the hasty flight planning already, when I see a city in front of me. The only larger city close to the airport is Luckenwalde, about 5 miles south. Could I be off my course by so much?

Recovery

I decide to follow the town to an intersection directly south of the airport and try to shoot straight up from there. I keep looking and before long I see the black of the runway through the mist. What a relieve!

I am one of only two guests at the airport restaurant in Schönhagen. I order a big glass of juice – my mouth is just a bit dry…

Incident investigation

Back home at my desk I try to figure out what went wrong. I start with my map. I gestimated a course of 250° from the FWE VOR to Schönhagen. The actual course should have been 252°, so that is a error of 2°.

Next I check the GPS log on CloudAhoy. From the VOR I flew a pretty straight line at first. Then, there is a slight change of course, about half way between the VOR and Schönhagen. Not much, maybe another 3° or 4°.

I am surprised to see how far this little deviation brought me from my course. How many miles does 5° translate to?

The distance from the VOR to Schönhagen is about 38 nautical miles. Remembering high school geometry, 2\pi x 38 miles gives me a circle of 239 miles. Divide that by 360 degrees and the distance per degree deviation in Schönhagen was about .66 NM.

So 5 lousy degrees – clearly within the margin of error of the junior aviator – translates into a miss of more than 3 nautical miles (3.5 statute miles or 5.5 kilometers)! Well beyond the visibility of the day.

Add the inaccuracy of the VOR indicator (the scale is analog and pretty approximate) and it becomes clear what has happened.

My Instructor smiles knowingly when I tell him the story. “Feels pretty bad if you can’t find the airport, doesn’t it?”

To be continued…

 

(originally posted on February 26, 2013 by tilbo at aloft.blog.com/o-airport-where-art-thou/)

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