Lesson 3 – Ground Reference Maneuvers

Today’s lesson started out with a 45 minute discussion about ground reference maneuvers. The purpose of ground reference maneuvers is to start the pilot thinking about the traffic pattern. The traffic pattern is a box with the wind coming from a fixed location. To maintain a specified distance away from a fixed point, such as a runway, you must compensate for the effects of the wind.

To familiarize the student with this maneuver, it is broken down into various parts. The first part consists of doing turns around a point. You take a point on the ground, in our case it was a clump of three large power lines in the middle of a salt flat on the shore of the bay. The challenge is to maneuver in a circle around this point, keeping your radius the same the whole way around. You must also maintain your altitude within 100 ft and your airspeed within 10 knots through the whole maneuver. The key is to first determine where the wind is coming from. Once that is determined, you can then figure out where your steepest bank will be and where your shallowest bank will be.

In the ground lesson my instructor drew a circle on the white board and gave me a wind direction and velocity and asked me where the steepest bank would be and where the shallowest would be. Now, my mistake was I began to think of this as crab angles; that is, I figured when you were turning into the wind, since it would be forcing you the other direction, you would need a steeper turn to make it around. My instructor said this is a common misconception but it helps to think of the problem in terms of speed. If the wind is coming from the north at 20 knots and the plane is traveling South at 80 knots then the actual ground speed of the plane is 100 knots. If the plane is going north, then the ground speed of the plane is 60 knots. Which direction will you get off course quicker? Going South at 100 knots will get you off course more quickly then going North at 60 knots so when you are on the downwind is where you need to make the steepest bank and not when you are turning upwind. Traveling faster means you need a tighter turn in order to keep the radius the same as when you are traveling slower.

We also talked about S-Turns which is a turn around a point that is broken down into two circles. You start by taking a ground reference object, in our case a straight pier supporting the towers that extended out for a mile. A straight road is another common ground reference point for this maneuver. You cross the road with wings level and begin a turn to the right. The goal is to establish a radius that you are going to use for the rest of the maneuver. You must cross the road again with your wings perpendicular to the road and then start a turn to the left, keeping the same radius as the previous leg. This draws an ‘S’ shape on the ground and, if you performed the maneuver correctly, consists of two half circles of equal radius.

So with the ground lesson concluded, it was time to “kick the tires and light the fires,” as they say. I performed the preflight check this time by myself without my instructor watching me. It went without a hitch except we were in a newer Citabria now and there were a few differences. The one I could not figure out was how to take the fuel sample from the wings as it did not have a valve sticking down like on the older Citabria. My instructor showed me how to pull off the attachment and turn it upside down and then stick it in a bolt on the wing which then produced a flow of fuel into the container. I would have never figured that one out if he hadn’t told me.

Anyway, I got to work the radios a bit today. I wrote down the ATIS information and called up the ground controller and sounded like a professional. “Palo Alto ground, Citabria 374 Delta Mike at West Valley, taxi to runway 31 for right Dumbarton departure with Whiskey.” We got the clearance to taxi, I did the run-up, called tower and let them know we were ready for departure. This takeoff was a bit different than the last two. My instructor wanted me to control the rudders this time and he would take care of the stick and power. We started our takeoff roll and I anticipated the torque pulling us to the left so I dialed in a little right rudder. We started off great but as we gained speed that little bit of right rudder turned into too much so I let off it a bit and we started to go left a little also. By then we had already lifted off and I was spared any more zigzag lines on the runway.

We flew to the bridge and turned right this time instead of or normal left departure. We leveled off at 1,200 feet to stay below the Bravo airspace which bottoms out at 1,500 feet. We crossed the bay pretty quickly and flew over Coyote hills and Leslie flats. We had a nice view of the rock quarry below. I never realized how deep that went into the ground. We turned to the right and headed toward the salt flats. The salt flats lie in the north part of Moffet Fields airspace so I dialed in Moffet tower and said, “Moffet tower, Citabria 374 Delta Mike over Leslie Flats request permission to do ground reference maneuvers in the North West part of your airspace.” They responded with the clearance and we were told to stay below 1,500 and squawk 0342. Now, I made a little mistake on that call because we were actually going to be in the North part of their airspace. The North West would be back over by Palo Alto but the controller seemed to know what I really meant.

Once we reached the area, we flew around and surveyed it from the air. We picked out a landing spot should the engine die. We do this because the ground reference maneuvers must be performed within 600-1000 feet of the ground which doesn’t give you much time to land should the engine quit. Once that was taken care of we determined the wind direction by looking at the dust coming up from some of the plows that were working the salt flats. It was blowing in a South East direction so we flew North West which is upwind and then flew downwind of our point to start the maneuver. Once our wings were perpendicular to the big towers, I began the turn.

This maneuver went really well. We did about 4 or 5 circles around the point and then did it again in the other direction. I maintained altitude and airspeed on all but one of the revolutions. My instructor was impressed and said that was good enough to pass the check ride. The S-Turns were not quite as good but given this was the first time I have ever performed these maneuvers, they were not bad at all. The hardest challenge was making your radius exactly equal on both sides. When you do turns around a point, you are fixated on one object so it is easy to reference that object and determine if you are getting too far or too close. On the S-Turns, you have multiple objects you are fixating on so it makes it a bit more challenging.

After we did about 7 or 8 S-turns, we established crab angles into the wind to follow directly over the power lines. If you were to just fly straight over them, the wind would eventually push you downwind of them so you need to turn into the wind a bit to maintain the ground track that you desire.

We then headed back across the bay, contacted tower, entered the downwind into the traffic pattern and I made a slight mistake. The controller told us to continue downwind to the amphitheater, and then 30 seconds later he said “4 Delta Mike, cleared to land number two for landing.” Now, the other times I had flown, when the controller cleared us for landing, we started our turn to base and started our descent. So, this time I started my turn and my instructor asked what I was doing. I stopped the turn and told him what I was doing and he said we were cleared but that we were instructed to go to the amphitheater first then make our turn. I thought the clearance to land overrode the instruction to go to the amphitheater but apparently not.

After that was straightened out, we turned to base and then final over the amphitheater. The approach was bumpy in this little bird as there was a bit of wind but we came in nice enough and I did the flare and held it off as instructed. The landing was a bit more forceful than I anticipated but my instructor didn’t say anything. I assume I may have held it off a tad high again. Anyway, we taxied in and shut her down and my instructor must have congratulated me 3 or 4 times on how I did with the maneuvers today which was encouraging.

I have another lesson tomorrow and what we work on will depend on the weather. My instructor thinks the ceiling will be low which will mean we will stay in the pattern and practice take offs and landings. If the weather is good, I am not sure what we will practice but there is still a lot left on the agenda so we will see. See you in the air...