Eights On Pylons
 

Had a student just take his commercial ride but he told me the DE was not to happy with the explanation of how my student found pivotal altitude in the airplane. We have always done them at 1,200 MSL and they work out nice. He passed and everything but I was just curious if any of you knew a simple way to figure PA out in the airplane. The GS is right there on the GPS but obviously you wont know your GS if your on the ground before the flight. Should he have broke out a calculator or something??

(GS * GS)/11.3 + Field Elevation = PA in MSL

http://www.aopa.org/asf/publications...fm?article=226
~ GS/3 *20

How I learned PA was this:

Using the formula (GS^2)/11.3 , come up with a range of PAs for different groundspeeds..... say between 70 knots and 120 knots..... write those down on your clipboard (for your actual checkride). When you've determined your ground speed, use the closest PA as written on the chart for your current GS.

Make a table:

Yes - before even meeting with the examiner.
Prior to the checkride, get a copy of the local weather and use the winds to find your [student's] groundspeed. Using that groundspeed, calculate pivotal altitude and write that on the same paper that will be used for writing down the WX report in the plane.
Using the same pivotal altitude regardless of surface winds is indicative of a serious training deficiency.

you're a CFI and you don't know the formula for PA?

GS(knots)^2/11.3
GS(mph)^2/15

I typically just enter the manuever at 1000 feet and just establish PA.

It will change at numerous points though.......

Figure it out on the ground.

More than likely, if you're doing them properly you won't need it, it will turn out that the alt. you computed was close.

How did you become an instructor without knowing how to compute this and teaching it to your students when you introduce Eights-on? That formula is first and foremost in nearly every aviation text out there.

Wow, can you believe the feds still expect you know that crap? PA calculations will never save your life. What a waste of time.

physics of 8s on pylons
 

My guess is the FAA thinks if you have the skill required to fly a good eight on pylon circuit then you will be a better pilot and better able to handle emergencies when they happen. In and of itself pylons is a less useful maneuver compared to something like a performance takeoff but it develops skill in anyone who performs it well. I managed to get through commercial without insight into how pivotal altitude actually works in a physical sense. I knew the P.A. formula and to dip or climb as required, but I did not have a very complete understanding of groundspeed and why it changes with altitude. Very few instructors know the actual physics involved either. I found a nice webpage on it here. Having some insight into the physics of dipping and climbing makes it less mysterious and makes pylons a demonstration in physics rather than a task on a list.