What is Pivotal Altitude?

During the initial training of pilots, they learn how various flight controls pressure input affects the aircraft. The pilots were also told basic maneuvers during their initial training. However, in commercial pilot training, they need to master advanced maneuvers, and one of the maneuvers is eight on-pylons. The advanced maneuvers are required to evaluate the student's piloting abilities further. 

When performing this maneuver, the students must be able to divide attention between precise airplane control and turning around a ground reference at a specific pivotal altitude. The pivotal altitude constantly changes with the ground speed due to the effects of the wind. These advanced maneuvers shouldn’t discourage students, as they can easily be achieved once the concepts are well understood. 

In this blog, we will provide the pilot students with all the information they need to comprehend pivotal altitude and safely execute the eight-on-pylons maneuver.

What is Pivotal Altitude?

Pivotal altitude is the most appropriate altitude for performing eights-on-pylons. It is a specific altitude at which the aircraft turns at a given groundspeed from the pilot’s point of view. The aircraft wingtip appears to pivot around a single fixed ground reference point.

Calculation of Pivotal Altitude

The pivotal altitude doesn’t remain constant at a specific altitude but changes with the ground speed. For the calculation of pivotal altitude, the ground speed instead of the IAS (Indicated Airspeed) is used because the pivotal altitude depends upon the horizontal speed of the airplane relative to the ground. The IAS remains constant during the flight, but the ground speed changes, especially when the flight transitions from headwind to tailwind or vice versa. 

To measure your aircraft's pivotal altitude theoretically, you have to take your ground speed and square it. If the ground speed was measured in miles per hour, then divide the squared groundspeed by 15. In this case, your groundspeed is calculated as knots and then divided squared by 11.3. Doing this will give you an approximate pivotal altitude above the ground level (AGL). You have to add the ground’s altitude to get the altitude above MSL (Mean Sea Level)

Formula in Miles Per Hour

Pivotal Altitude = (Groundspeed)^2/15 

Formula in Knots

Pivotal Altitude = (Groundspeed)^2/11.3

The formula shows that the faster the groundspeed, the higher your pivotal altitude will be. You must know how to calculate the pivotal altitude manually based on your groundspeed. Some pilots create a cheat sheet for common ground speeds.

When there is no wind, the pivotal altitude remains the same because the groundspeed is also the same. But no-wind conditions are rare, and your groundspeed will change. To maintain the reference line on the pylon, you have to adjust your altitude throughout the turn-in together with the ground speed changes. This means that when you are in a headwind position, the pylon will start to move ahead of your reference line, and you have to descend since both the pivotal altitude and groundspeed are decreasing.

When you are in a tailwind position, the ground speed increases; this causes the pylon to move behind your reference line, and then you must climb to maintain the proper pivotal altitude. The success of this maneuver depends upon the pilot's ability to maneuver the aircraft accurately while dividing attention between the chosen pylon on the ground and the flight path.

What are Eights on Pylons?

Eights-on-pylons are advanced maneuvers that must be mastered to earn commercial pilot and flight instructor certificates. This advanced skill is built upon fundamentals such as executing S-turns, flying a rectangular course, and making turns around a point. To master this skill, student pilots must be proficient in straight-and-level flight, S-turns, slow flight, stalls, and other maneuvers that support the development of pilot skills. 

This skill also requires concentration and handling difficult distractions, specifically holding the pivotal altitude while making good turns and being aware of other airplane positions over the ground. The eights on pylons are built on a skill called eights around pylons. When performing eights on pylons, you must fly around each pylon or a stationary point on the ground. The focus is to maintain your altitude and constant distance from the pylon.

This skill tests your ability to change your bank angle to correct for wind drift. As you move into the wind, you must lessen your bank. When you go downwind, then your bank should be steeper. When you master eights around pylons, you can start learning eights on pylons. The aim of eights on pylons is to show the skill to pre-plane maneuvers, visualize results, and adjust for the impact of wind and other factors.

You must demonstrate that you can execute this challenging skill, which demands full concentration while handling distractions and maintaining awareness of other traffic. Your airplane position should be relative to the ground throughout the maneuver.

When you have learned to adjust the bank angle during the eights around pylons maneuver, the eights on pylons maneuver will take this to an advanced level. As pivotal altitude is determined based on ground speed rather than maintaining a constant altitude throughout the maneuver, you have to adjust your pivotal altitude according to your groundspeed.

To know how well you’re holding your pivotal altitude, you will get the clues from the location of the pylon relative to your airplane reference point. If you notice that the reference point started to move behind the pylon, your altitude is higher, and you must descend to reach the pivotal altitude. And if the reference point moves ahead of the pylon, your altitude is lower, which means you must ascend to reach pivotal altitude.

How to master Eights on Pylons?

To master the eights on pylons, you must correctly calculate the pivotal altitude. Create a pivotal altitude cheat sheet for the ground speeds that are common to you and your aircraft. Always select your pylons carefully. The pylons along the road's side and other easily visible straight lines are the easiest to use. You must understand the relationship between the pivotal altitude and groundspeed.

Know that a higher ground speed requires a corresponding higher pivotal altitude, and a decrease in ground speed requires a reduction in altitude. You must also know how to read shifts in the relative location of your airplane reference point and the pylon. Your groundspeed is too high when the reference point is behind the pylon and too low when it is ahead of the pylon. 

What is the reason that our actual pivotal altitude is sometimes different from the calculated altitude?

To calculate the pivotal altitude theoretically, you have to add certain key assumptions. To measure actual aircraft maneuvers, you must create the desired pivoting appearance at the calculated altitude; we must fulfill the assumptions of constant airspeed, coordinated flight, calm winds, and level turn. 

You will rarely experience a complete absence of wind, and the airspeed will not remain the same. The pivotal altitude formula is considered as a rule of thumb that gives us a starting point. As we start to make our turns, we have to adjust the altitude to correct for the impact of the wind and our varied speeds.

Conclusion

To conclude, student pilots must understand pivotal altitude, essential for mastering eights on pylons. Some maneuvers are fundamental to learn before going for eights on pylons. This blog thoroughly discussed pivotal altitude and how to calculate it for different measurements. Furthermore, we have discussed how you can master the eights on pylons quickly. 

You must avoid the most common errors in performing eights on pylons. Carefully select your pylons. Check the surrounding area for safety hazards, initially and throughout the maneuver. Avoid skidding or slipping in turns. Mastering the eights on pylons requires correctly calculating the pivotal altitude.