How do you teach pivotal altitude?

Wing_96

Wing_96

Well-Known Member
How do you teach pivotal altitude to your students?

Do you use the chart in the Airplane Flying Handbook, or use the "square the TAS and divide by x" method for estimating the pivotal altitude? Is there some other method of teaching/explaining pivotal altitude that's better than these two mentioned?
 
I have my students make a chart for the various speeds and I teach them the theory behind pivotal alt. I used to think that it was the altitude that we crossed at initially but later learned that it is your altitude through out the entire eights on maneuver. The altitude changes every second you're doing the maneuver as long as your ground speed is changing.
 
taildragger173 said:
I have my students make a chart for the various speeds and I teach them the theory behind pivotal alt. I used to think that it was the altitude that we crossed at initially but later learned that it is your altitude through out the entire eights on maneuver. The altitude changes every second you're doing the maneuver as long as your ground speed is changing.
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:yeahthat:

I teach the formula, but also use a little chart that has the math done already.

BuickCFI said:
Gs^2 / 11.4
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Not to nitpick; but:

Pilots Handbook of Aeronautical Knowledge said:
A rule of thumb for estimating pivotal altitude in calm wind is to square the true airspeed and divide by 15 for miles per hour (m.p.h.) or 11.3 for knots
Click to expand...
 
yeah
GS(squared)/ 11.3 = PA

Basically, the faster your GS the higher your PA.

Teach them how to visualize a constant line of SIGHT to the pylon, and why we are changing our bank angle and altitude to maintain that sight picture.
 
the number to work with would of course be groundspeed..it's a ground reference maneuver and we would thus be concerned with speed across the ground. and pivotal airspeed is going to vary with groundspeed. indicated or true airspeed may be used as a 'rule of thumb' unless you have a gps providing instantaneous groundspeed readouts, otherwise you're just going to wind up estimating speed as best you can. in a zero-wind condition, tas would equal groundspeed, so..
 
exleardriver said:
the number to work with would of course be groundspeed..it's a ground reference maneuver and we would thus be concerned with speed across the ground. and pivotal airspeed is going to vary with groundspeed. indicated or true airspeed may be used as a 'rule of thumb' unless you have a gps providing instantaneous groundspeed readouts, otherwise you're just going to wind up estimating speed as best you can. in a zero-wind condition, tas would equal groundspeed, so..
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Yes, I noticed that the Airplane Flying Handbook says that the TAS formula is "rule of thumb". The airplane does have a GPS with groundspeed, so how do I know what the pivotal altitude should be based on the groundspeed? If the GPS shows the groundspeed to be 110 kts, then what is the pivotal altitude for that groundspeed?
 
Wing_96 aksed: "If the GPS shows the groundspeed to be 110 kts, then what is the pivotal altitude for that groundspeed? "


A couple of the replies above gave the formula, but since you asked again....I'll do the math for you :-)

Formula for knots: GS squared, divided by 11.3
110kts squared = 12,100
divided by 11.3 = 1070.80 ----> That is your pivotal altitude

1100 would be a lot easier to read on the altimeter, so set your altitude and start adjusting throughout the maneuver. Happy flyin'

Oh..as others have suggested....you can whip up a cheat sheet of different ground speeds and have the pivotal altitude already calculated.

90 knots = XXXX
95 knots = XXXX
100 knots = XXXX

You get the idea..just plug the knots into the formula and BAM, your done.

Pac Man
 
PacMan4x4 said:
Wing_96 aksed: "If the GPS shows the groundspeed to be 110 kts, then what is the pivotal altitude for that groundspeed? "


A couple of the replies above gave the formula, but since you asked again....I'll do the math for you :-)

Formula for knots: GS squared, divided by 11.3
110kts squared = 12,100
divided by 11.3 = 1070.80 ----> That is your pivotal altitude

1100 would be a lot easier to read on the altimeter, so set your altitude and start adjusting throughout the maneuver. Happy flyin'

Oh..as others have suggested....you can whip up a cheat sheet of different ground speeds and have the pivotal altitude already calculated.

90 knots = XXXX
95 knots = XXXX
100 knots = XXXX

You get the idea..just plug the knots into the formula and BAM, your done.

Pac Man
Click to expand...

This is a direct quote from the Airplane Flying Handbook (FAA-H-8083-3A) 2004:

"A rule of thumb for estimating pivotal altitude in calm wind is to square the true airspeed and divide by 15 for miles
per hour (m.p.h.) or 11.3 for knots."

Notice it says true airspeed, not groundspeed. My question is then, can you use the same formula you used above replacing true airspeed with groundspeed?
 
Wing_96 said:
This is a direct quote from the Airplane Flying Handbook (FAA-H-8083-3A) 2004:

"A rule of thumb for estimating pivotal altitude in calm wind is to square the true airspeed and divide by 15 for miles
per hour (m.p.h.) or 11.3 for knots."

Notice it says true airspeed, not groundspeed. My question is then, can you use the same formula you used above replacing true airspeed with groundspeed?
Click to expand...
i have, it seems to work out, next time i do these with a student i am going to try the TAS^2 method and see if there is a difference

edit: there should be it is a ground ref. manuever
 
Wing_96 said:
This is a direct quote from the Airplane Flying Handbook (FAA-H-8083-3A) 2004:

"A rule of thumb for estimating pivotal altitude in calm wind is to square the true airspeed and divide by 15 for miles
per hour (m.p.h.) or 11.3 for knots."

Notice it says true airspeed, not groundspeed. My question is then, can you use the same formula you used above replacing true airspeed with groundspeed?
Click to expand...

Note that the AFH says "in calm wind" to use TAS. This is identical to GS.

However, the AFH is fundamentally wrong using the language they do. Any ground reference maneuver depends on ground speed and it should be stated that way. (The ground has no way of knowing your TAS.) In a calm wind, TAS will equal GS.
 
I recommend that they (the student) figure out what their slowest and fastest ground speed will be for that day. Then, utilizing those two figures finding out their lowest and highest pivotal altitude for the whole maneuver - by using the formula. Now they know what "block" of altitude they will be utilizing.

That's how I teach it on the ground, along with how it will adjust throughout the maneuver. Along with why it's increasing or decreasing (GS relation).
 
tgrayson said:
Note that the AFH says "in calm wind" to use TAS. This is identical to GS.

However, the AFH is fundamentally wrong using the language they do. Any ground reference maneuver depends on ground speed and it should be stated that way. (The ground has no way of knowing your TAS.) In a calm wind, TAS will equal GS.
Click to expand...

nice to see someone in agreement. ;) groundspeed fellas..gs = tas in 'no wind'..it's a ground reference maneuver'. true airspeed rules of thumb assume you're basing your pivotal altitude estimates based basically upon your indicated airspeed you read while flying..shortcut method of approximation.
 
Now the golden question:

Do you adjust altitude to stay on your "pivital Altitude" as your GS changes or do you adjust your power to maintain the same GS (and thus the same altitude) throughout the manuver?

Instructors at my old dlight school used to debate this alot.
 
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