Eights On Pylons
#1
Gets Weekends Off
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Joined APC: Jul 2007
Position: Lear 55 CA
Posts: 244
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??
#3
http://www.aopa.org/asf/publications...fm?article=226
~ GS/3 *20
To estimate pivotal altitude, square the groundspeed and then divide by 15 if you use mph, or 11.3 if you prefer knots. That will provide a starting altitude. For example, 100 mph times 100 equals 10,000, divided by 15 equals 666 feet approximate pivotal altitude. A groundspeed of 95 mph results in a pivotal altitude of 600 feet. Hence, traveling at 100 mph on the fast side, pivotal altitude is 666 feet. On the slower side-the side into the wind-95 mph results in a pivotal altitude that is 60 feet lower than the fast side.
#4
Gets Weekends Off
Joined APC: Jan 2008
Posts: 1,201
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:
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:
Code:
Ground Speed | Pivotal Altitude 70 kts 433 ft 80 566 90 717 100 885 110 1071 120 1274
#5
Gets Weekends Off
Joined APC: Jul 2006
Posts: 1,857
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.
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.
#6
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(knots)^2/11.3
GS(mph)^2/15
#8
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.
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.
#10
physics of 8s on pylons
Last edited by Cubdriver; 06-03-2008 at 04:16 AM.
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