What is pivotal altitude?
Pivotal altitude is the specific altitude at which, when an airplane turns at a given groundspeed, from the pilot’s point of view, the plane’s wingtip seems to pivot around a single fixed reference point on the ground.
(Vector of Plane by brgfx on Freepik )
How is pivotal altitude calculated?
Pivotal altitude is not a single constant altitude but varies based on groundspeed. To calculate the theoretical pivotal altitude for your aircraft at its current groundspeed, take your groundspeed and square it. If your groundspeed was measured in miles per hour, divide the squared groundspeed by 15. If you measured your groundspeed in knots, divide the squared groundspeed by 11.3. This gives you your approximate pivotal altitude above ground level (AGL). Add in the ground’s altitude to get your altitude above mean sea level (MSL).
As you can see by the formula, the faster your groundspeed, the higher your pivotal altitude will be. Although you should know how to manually calculate your pivotal altitude based on your groundspeed, many pilots also make themselves a cheat sheet for common groundspeeds.
Groundspeed in knots
Groundspeed in mph
Approx. Pivotal Altitude
Why is our actual pivotal altitude not always the same as the calculated altitude?
When performing a theoretical pivotal altitude calculation, there are certain key assumptions that are included. For the actual aircraft maneuver to create the desired pivoting appearance at the calculated altitude, we would have to meet the assumptions of constant airspeed, coordinated flight, calm winds, and a level turn.
Since it is very rare that we will ever experience a complete absence of wind, and our airspeed will not remain constant, the pivotal altitude formula is viewed more as a “rule of thumb” to give us a starting point. From there, as we make our turns, we will have to adjust altitude to correct for the impact of the wind and our varied speed.
Why should I care about pivotal altitude and what is it used for?
“That’s all very interesting,” you may be thinking, “but why should I care about pivotal altitude? When will I ever use this, and what does it matter?”
Most pilots will be introduced to pivotal altitude by their flight instructor as they are preparing for their commercial pilot or flight instructor checkride. The ability to establish and maintain pivotal altitude is a skill which is needed to excel in a maneuver commonly referred to as “Eights on Pylons.”
What is “Eights on Pylons?”
“Eights on Pylons” is the name of one of the most advanced and difficult flight maneuvers that you must be able to ace in order to pass your checkride and become a commercial pilot or a certified flight instructor. It is the final skill that builds on basic fundamentals like flying a rectangular course, executing s-turns and making turns around a point.
The intermediary building block for eights on pylons is a skill called eights around pylons. In eights around pylons, you fly around each pylon (or designated stationary point on the ground) with a focus on maintaining your altitude and a constant distance from the pylon.
Eights around pylons tests your ability to vary your bank to angle to correct for wind drift. As you are going into the wind, you must shallow out your bank. When you are downwind, your bank will need to be steeper.
When you have mastered eights around pylons, you will advance to eights on pylons. The purpose of eights on pylons is to demonstrate an ability to pre-plan maneuvers, visualize results, and adjust for the impact of wind and other factors.
You will need to show that you can execute a challenging skill which demands concentration while also handling distractions and maintaining an awareness of other traffic and your aircraft’s position relative to the ground throughout the maneuver.
While you learned to adjust your bank angle during eights around pylons, eights on pylons takes it a step further. Because pivotal altitude is determined based on groundspeed, rather than maintaining a stable altitude throughout the maneuver, you will need to adjust your altitude to maintain pivotal altitude for your changing groundspeed.
When you are downwind and your groundspeed increases, you must immediately increase your altitude to compensate and maintain pivotal altitude for the new speed. Likewise, when your groundspeed slows as you turn into the wind, you will need to decrease your altitude to hold pivotal altitude for the slower speed.
The location of the pylon relative to your aircraft’s reference point (usually along the wing tip) will give you clues as to how well you are holding your pivotal altitude. If the reference point begins to move behind the pylon, your altitude is too high, and you need to descend to reach pivotal altitude. If the reference point shifts ahead of the pylon, your altitude is too low, and you must ascend to reach pivotal altitude.
How to ace the Eights on Pylons maneuver
- Know how to do your pivotal altitude calculations
- Make and post a pivotal altitude cheat sheet for your most common groundspeeds
- Choose your pylons carefully. Pylons located along a road or other easy to see straight line are the easiest to use.
- Understand the relationship between groundspeed and pivotal altitude. Remember that increased groundspeed requires a corresponding increase in altitude. Decreased groundspeed requires a decrease in altitude.
- Know how to read shifts in the relative locations of your aircraft reference point and the pylon. If the reference point is moving behind the pylon, you are too high for your groundspeed. If the reference point is moving ahead of the pylon, you are too low for your groundspeed.
- Remember to not get tunnel vision and become so focused in on the pylons that you lose awareness of other traffic and of your position relative to the ground. Your ability to multitask is also being judged during this maneuver.
- Watch a commercial eights on pylons training overview to get a feel for the maneuver prior to attempting it in the air
Real-world application of pivotal altitude maneuvers
Naturally you are wondering if there are real-world applications for pivotal altitude, or if it is simply something you must learn to pass your checkride.
The reality is, there is a reason that mastery of pivotal altitude and the complex eights on pylons maneuver are part of the pipeline to obtaining a commercial pilot or flight instructor certification.
Once you have aced these skills, you will have gained an intuitive understanding of precision aircraft handling. What started out with you doing calculations and consciously adjusting to compensate for variables will have become second nature.
You will naturally control the aircraft with smoothness and precision while retaining awareness of your surroundings and managing other distractions. Your understanding of pivotal altitude will have made you a better, safer, more highly skilled pilot.
Want to learn more? Check out ASA Lesson Plans to Train Like You Fly, Fourth Edition.
ASA Lesson Plans to Train Like You Fly, Fourth Edition
Whether you're a CFI-in-training or a seasoned flight instructor, your realize the effectiveness of your lesson presentations is critical to student success - and your career as a CFI. To help you get the essentials across, Master CFI and 2009 National Flight Instructor of the Year Arlynn McMahon shares her scenario-based lesson plans covering every maneuver in the Private and Commercial training curricula.