power off climb, altitude gain numbers

[exncsurfer]

I can try this myself next time I'm goofing off in the airplane, but I'm wondering if anyone has tried this and what are your ballpark numbers?

Say, in a 172 at cruise speed of 120 indicated, power to idle, how high can you climb before you reach best glide? What is the best way to get the most altitude, steeper or shallower climb?

 

[iWantWings]

I don't have a value for altitude gained, but I can describe something similar I did that during my private pilot certificate checkride: while crusing at about 110Kts, DPE pulled power to idle.

My first reaction to was "convert" energy to altitude and pitched up to get to Vx until reaching best power off glide with flaps retracted.

1. i pitched up the instance i felt DEP pulling power out
2. the rate of pitch change was a little slower at first until speed decayed to inidicated Va (did not want to do abrupt pitch up before indicated speed had decreased to Va - for weight based on 2 occupants and 1/2 fuel)
3. after getting to Va, I continued to pitch "deliberatly/firmly" as necessary to get to "about" Vx.
4. once I pitched up to a degree that gave me "about" Vx, I had to relax back pressure continuously to maintain Vx during power off ascend, to maintain Vx
5. As energy was consumed during climb, I eventually leveled off and then lowered the nose descend at best glide speed with flaps up.

This was a C172 "S"

Now all of this happened pretty quickly and airspeed and pitch change continuously until you begin the descend at best glide speed. (DPE said it was very good, all things considered). But it would be interesting to try and get the value you were asking for. I'm guessing the amount of altitude you climb would depend (among other things) on the weight of the aircraft as well as the density altitude at which you start your power off (for example, power to idle at 3000 feet and start climbing, versus starting at over 10000).

 

[Sac Arrow]

I can try this myself next time I'm goofing off in the airplane, but I'm wondering if anyone has tried this and what are your ballpark numbers?

Say, in a 172 at cruise speed of 120 indicated, power to idle, how high can you climb before you reach best glide? What is the best way to get the most altitude, steeper or shallower climb?

Forget about what will give you the most altitude, focus on what will give you the least drag. Pitch to best glide immediately. Will a slow climbing transition give you more altitude? Don't know, but in any case your range will be reduced.

 

[exncsurfer]

Forget about what will give you the most altitude, focus on what will give you the least drag. Pitch to best glide immediately. Will a slow climbing transition give you more altitude? Don't know, but in any case your range will be reduced.

Yea, good point, I was thinking more of time vs. range. Mainly for a low altitude fail.

 

[exncsurfer]

I don't have a value for altitude gained, but I can describe something similar I did that during my private pilot certificate checkride: while crusing at about 110Kts, DPE pulled power to idle.

My first reaction to was "convert" energy to altitude and pitched up to get to Vx until reaching best power off glide with flaps retracted.

1. i pitched up the instance i felt DEP pulling power out
2. the rate of pitch change was a little slower at first until speed decayed to inidicated Va (did not want to do abrupt pitch up before indicated speed had decreased to Va - for weight based on 2 occupants and 1/2 fuel)
3. after getting to Va, I continued to pitch "deliberatly/firmly" as necessary to get to "about" Vx.
4. once I pitched up to a degree that gave me "about" Vx, I had to relax back pressure continuously to maintain Vx during power off ascend, to maintain Vx
5. As energy was consumed during climb, I eventually leveled off and then lowered the nose descend at best glide speed with flaps up.

This was a C172 "S"

Now all of this happened pretty quickly and airspeed and pitch change continuously until you begin the descend at best glide speed. (DPE said it was very good, all things considered). But it would be interesting to try and get the value you were asking for. I'm guessing the amount of altitude you climb would depend (among other things) on the weight of the aircraft as well as the density altitude at which you start your power off (for example, power to idle at 3000 feet and start climbing, versus starting at over 10000).

Yes, this was exactly what I was looking for. But you didn't happen to look at the peak. Just wondering about the range of numbers people might have gotten, is it in the low hundreds of feet, a thousand?

 

[OzPilot]

I used to have to practice a zoom climb with idle power to gain around 150 to 200 feet depending on day (sundowner), but then your pitch over to glide needs to be near perfect or you eat up the altitude gain. Faster birds of course can gain 300 or so but also typically have a higher glide.

My instructor in australia had me do this for simulated engine outs over water but near shore. The concept was to gain a little more time but I'm not sure if the physics worked out well (such as the glide time between a Gross loaded vs unloaded plane). Same glide distance but less time when Gross loaded etc I believe

 

[GeorgeC]

I don't know anything about anything, but this made me fall down a trajectory optimization rabbit hole.
Converting all excess kinetic energy to potential energy without drag gives about 450 feet. Real world swag, maybe half that?
I wrote a simple point mass simulator with notional lift/drag curves and got about the same answer.
My guess is, pull hard but do not stall, and pitch over when you get near best glide.

 

[OkieFlyer]

I don't know anything about anything, but this made me fall down a trajectory optimization rabbit hole.
Converting all excess kinetic energy to potential energy without drag gives about 450 feet. Real world swag, maybe half that?
I wrote a simple point mass simulator with notional lift/drag curves and got about the same answer.
My guess is, pull hard but do not stall, and pitch over when you get near best glide.

Sound like you know a lot more about something than I ever will.