Eights on Pylons
How to Begin…
First, you’ll need to find Pivotal Altitude. What is Pivotal Altitude? Great question!
Pivotal altitude is the height for a given ground speed at which the line of sight from the cockpit directly parallel to the lateral axis of the aircraft will remain stationary on an object on the ground.
Fancy words right?? What is it in plain speak?
The altitude that when you are making a turn around a point on the ground, the point will stay perfectly on your wing tip when you are at that altitude (pivotal altitude).
How do you find pivotal altitude?
To find Pivotal Altitude, you will first calculate your groundspeed (so if you plan to fly 100 knots and have a tailwind of 10 knots, your groundspeed will be 110knots).
You will then square your ground speed, and divide by 11.3 (you only divide by 15 when using MPH instead of Knots).
Example: Groundspeed = 110kts. 110 x 110 = 12,100 Then divide 12,100 / 11.3 = 1,070.8, thus Pivotal Altitude is 1,071 feet AGL.
If you fly a circle around a point banking your wing to line up the point right on the tip of your wing, and begin your turn at 1,071′ AGL then with those conditions (airspeed and tailwind giving you 110knots groundspeed) you will keep the point in sight right on your wingtip.
So that’s it?
Nope, because as you make that turn your tailwind will eventually die off and then become a headwind, changing your groundspeed, which will CHANGE YOUR PIVOTAL ALTITUDE. Meaning to keep the point right on your wingtip, you’ll have to DESCEND as your groundspeed DECREASES and PIVOTAL ALTITUDE decreases as well.
How it Starts:
Enter the maneuver on the downwind (with a tailwind) at a 45-degree angle to the road or line that joins your two points (pylons).
Start the turn when you’re abeam your first pylon, and turn towards the pylon so that your wingtip stays “attached” to the pylon throughout the maneuver.
If the pylon moves ahead of the wing tip, push forward, lower the nose, increase your ground speed. If the pylon starts “moving behind the wing”, then raise your nose, slow your ground speed, and watch the pylon “catch up” to your wing tip.
Make small pitch changes (no more than 10 degrees up and 5 degrees down). The better you get at this maneuver, the smaller the pitch changes you will need (maybe only 2-3 degrees nose up and 2 degrees nose down).
You end the maneuver after making a figure eight pattern around both pylons. The altitude you end the maneuver at does not matter.