What makes soaring so interesting, especially in the mountains, is that you are constantly changing the reference for determining your total energy state.
Thank you for your excellent question. Most pilot training manuals mention mechanical energy only briefly, and I've never found one that references specific energy. While all glider students learn that we can exchange airspeed for altitude and vice versa, we can't know the rate of exchange without considering our specific energy. The screenshot in the video is of a spreadsheet I've made for my glider -- it is not from the AFM. Pilots can greatly improve their situational awareness by considering their glider's energy state.
Since specific energy represents the theoretical instantaneous transfer of energy, the glide ratio isn't considered in the calculation. In the real world, however, glider type and pilot technique would affect the efficiency of energy transfer. Once reduced, the equation for specific energy is: e = h + V^2 / 2g.
Great video, just a quick question? How do you apply this while flying besides just arbitrarily flying faster. If are you are low are you trying to ensure you have 150m altitude ready to be converted from increased airspeed? If really low maybe 300m?
Thank you for your kind words! No, we don't arbitrarily fly faster when we're close to the terrain, and there's no "one-size-fits-all" rule-of-thumb to insure that we have sufficient energy. We have to analyze each situation and identify how our potential energy is restricted.; we need to know the question before we can determine the answer. Specific energy only provides us with the conversion between airspeed and altitude. A future video will go into much more detail about how to apply it while flying.
Very nice video! It would be better if it was possible to see the dashboard or the indicators of the altitude, speed and variometer instruments. This would make it possible to analyze the changes (overflow) of energies into each other. And also see where the glider gains or loses height. Thanks for the video!
Thank you for your kind words. I show the instrument indications where appropriate in other videos. This video is only intended to be an introduction to specific energy. A future video will have a thorough explanation, including instrument indicators.
Great video and great explanation as always! 👍 I just got a little bit confused with the formula for specific energy (8:00), as specific energy is defined as e = E/m and weight is defined as W = m•g. So taking formula 6:15 specific energy shall be defined as e = g•h + 1/2 • V^2 Not?
Thank you for your kind words and for your excellent question. Specific energy (e) is normally calculated without acceleration (1g), so it would be defined as total energy (E) divided by mass (m). But since gliders are not always at 1g, we must take acceleration into account by dividing total energy by mass times acceleration, which as you know is weight (W), or e = E / W. Once reduced, the equation for specific energy becomes e = h + V^2 / 2g.
Chris, wonderful to see you and a new video from you! It was a thoughtful video, indeed. I equated it to several flights I made last season, when potential energy was all I considered. I was at the point in my glider experience where I was not willing to give up altitude (cushion) to venture across potentially unlandable terrain (39/1 glider). However, I’m starting to learn the value of kinetic energy (even though I fall off the polar pretty rapidly above 60kts) and not just fly around at min sink. This new video of yours has gelled that for me. And, I still blame you for causing me to become a glider pilot! Happy New Year!
I like the calm and instructional nature of your videos! There is a bit of a strange disconnect between the sensationalist title of the video and the actual, calm, content though 😄
you have to substract the kinetic energy of your stall speed from your energy state. The difference is what you have available for a pull-up (transformation back in altitude).
Specific energy includes the total mechanical energy of the glider, regardless of aerodynamic stall. But yes, "available kinetic energy" will be the subject of another video. Thanks for your comment!
Another fantastic video Chris! Educational and beautiful cinematography. Huge fan of Scott Buckley’s very fitting music too! Do you happen to know the name of the mountain with switchbacks @2:26? Looks like a fun one to hike👍
Congratulations another great video. Best use of a 360° camera. The only little improvement i wish for is, that you indicate when the footage is sped up.
Thank you for your kind words. Re your wish, I’m concerned about overwhelming the audience with excess information. I’ll give it some thought - but my first idea would be a 2x in a corner. What do you think?
@@FayenceSoaring for me it would make things clearer, because if you were flying as fast as sometimes shown and full of ballast, i guess, you would have a higher percentage of kin energy stored. Maybe indicated with two arrows, sth like ">> 2x"?
Energy can’t be lost, but it can become unavailable. If we are flying close to the ground, or if our planned flight path will take us close to the ground, our potential energy will be limited. If we’re flying well above the mountain peaks, all of our potential energy is available.
The point of highest threat actually occurs prior to reaching the middle of the ridge, and is where we need to carry extra kinetic energy to mitigate that threat. Once we’ve reached the ridge, continuing straight ahead becomes unobstructed - our potential energy becomes available - and where we may return to a normal airspeed.
Attention à l'interprétation des courbes vitesses/altitude, il faut garder un minimum de vitesse pour je pas décrocher, vous ne pouvez pas atteindre 0km/h!
L'énergie spécifique comprend l'énergie mécanique totale du planeur, quel que soit le décrochage aérodynamique. Mais oui, "l'énergie cinétique disponible" fera l'objet d'une autre vidéo. Merci pour votre commentaire!
The multiple “quick breaks” are extremely annoying and unnecessary. One per video, or even just a quick annotation would be more than enough. Just a suggestion.
Thanks for your suggestion. There was only one advertisement break in this video. RU-vid’s advertisement breaks are usually automatic, which are much more annoying IMHO. By setting them manually, at least they don’t interrupt the video at inconvenient locations. I hope you were able to enjoy my video nevertheless.
