You don't understand how helpful this was to me. My hometown airport is in the Los Angeles area and calculating altitudes for all the waypoints I need gets extremely complicated. Thank you
small tip - instead of interpolating the values for wind (or any values for that matter) use the values at 2/3 of the climb and for descents use the values at 1/2 of the descent. This is because values dont vary liniarly.
Thanks for the comment and thanks for sharing. This sounds like an easy method for planning outside of a test or check ride because you are right, the values don’t always vary linearly. Another short cut is to just use the next, least-favorable value in the table or chart (I call it rounding pessimistically). In General Aviation it is almost always better to plan to need more gas and not use it. However, most of the DPE in our area want to know you can use the FAA-approved tools during your check ride. So, for now that means knowing and understanding interpolation. One question I have for you, is how did you decide to use 2/3 of the value during climb and 1/2 of the value during descent? Was it based on a table, calculations or a “rule of thumb”? Thanks again for the comment.
How come for “rounding pessimistically” for the airport elevation we go down, but cruise altitude we go up? Thank u so much for a fantastic video ! Subscribed
Thanks for the question. It is a very good one. My reasoning is that the least desirable outcome would be to climb for a longer period of time because it would use more fuel. The larger the difference between the pressure altitude of the airport and the pressure altitude of cruise the longer the climb would take. With that in mind, I rounded the cruise altitude up and the airport elevation down. I hope that helps. Thanks again for the question! And thanks for the Subscribe!!
Hi sir, great job. But, i could not understand why you assumed our TAS was 90 kt. In the climb chart, our IAS is 76. So, we should calculate our TAS based on that speed. We can calculate it by using EB6 as our altitude and OAT is available. I calculated as 85 TAS. Then, we add tailwind in this case which is almost 8 kt. Finally, our ground speed is 93 kt. Am i missing something?
Perfect question. And, to be honest, unless the climb is a long one, I’m not sure there will be enough difference between the result of your answer and mine to matter much for planning (I believe the difference in distance during the 8 minute climb would be 2/3 of a NM). In the video I note that the text section of Chapter 5 states “The time, fuel, distance to climb chart assumes no-wind conditions”. It further states “the effect of winds aloft must be considered by the pilot when computing climb, cruise and descent performance.” But it doesn’t suggest a specific method for doing so. There are three reasons I don’t do it the way you did. These don’t disqualify your method, they are just the reasons I don’t use it. First, angle of attack (especially high angles of attack) can impact IAS accuracy. So, even though your airspeed indicator says 76 kts, you may not actually be at that airspeed. Second, if you picture a climb in profile, it is (sort of) a right triangle with the distance you move through the air as the longer hypotenuse and the distance over the ground a shorter base side. Third, during a climb your altitude and temp (and therefore true airspeed) is constantly changing as you climb, so which true airspeed do you use? Again, the differences will likely be minimal, so perhaps you could just use the worst TAS. In any case, all these factors complicate the calculation of ground speed and the effect of wind. If you reduce the no-wind times and distances from the results of the chart back into KNOTS, you will get something over 76 kts (in fact the example used on the chart in Chapter 5 results in an “over the ground airspeed” of 80 rather than 76 kts). So I use that as the basis then factor the effects of wind as shown in the video. Still not perfect, but it attempts to overcome the issues I mentioned above. As noted above, there doesn’t seem to be a single, approved method for doing this so if your instructor taught the method you describes please continue to use it. Thank you for the question. I hope this helps explain why I did the calculations as I did.
@@ScottKoonCFI In total, i got your point. Thank you for answering but i have more questions if you dont mind. 1. "angle of attack (especially high angles of attack) can impact IAS accuracy. " Why is that? IAS is not affected by compresibility or position errors. IAS should show exatly the affect of dynamic pressure, right? 2. The reason why you took 8 minutes time as fixed and calculate the new distance from there is wind doesnt affect climb time, is that right? It doesnt come naturally tough. Is there any advice for me to visualize that fact better? 3. "a right triangle with the distance you move through the air as the longer hypotenuse and the distance over the ground a shorter base side." You mean if we take 98 instead of 93 (my version of GS) we are closer to that hypotenuse side as this distance is longer and we are closer to more realistic calculation? Sorry for overwhelming questions but i try to learn as much as i can. Thanks for your patience and interest.
Scott - I'm learning to fly in my 1965 Piper Cherokee 140 and the performance charts in my POH and AFM are uhm... a bit light. They're 2 axis graphs with "standard altitude" on the "up" axis and FPM (for the rate of climb) going across but there is nothing adding the temperature element to the equation. I would assume in this case I would use density altitude instead of pressure altitude. You're the one RUclips CFI that uses Piper (I've grown to loath the assumption that everyone learns in a Cessna 172) but your Piper is a couple decades in the future. I have an excellent CFI but he's never dealt with uh... uhm a vintage aircraft such as mine (I still have 1970's avionics - no GPS). Another curious aspect to this POH/AFM - there's no "Calibrated Air Speed" chart. I asked another 1965 Cherokee 140 YouTubing owner (who's also on the learning journey and our planes are very close in serial numbers) and he too has nothing. So to distill the two questions: Do I use DA instead of PA with my performance charts? Do I just use INDICATED if it's CALIBRATED when calculating my True Air Speed?
Jeffrey. This is an excellent question. And I apologize, the answer will be long. I was able to grab a copy of a Cherokee 140 Owners Handbook. You described it perfectly. The performance charts are “light”. However, I would recommend the following. To your first question… Yes, you will need to calculate density altitude in order to calculate performance. You can do that two ways. First, you can use an E6B (either electronic like Sportys, or the whizwheel) or use the “Altitude Conversion” chart in part IV of the handbook. Both should provide similar answers. By the way, the charts used in my videos actually use density altitude too. They just build the calculation into the single performance chart. Yours requires separate charts. Also, please notice that each of the performance charts in your handbook has two versions-one for 1950 pounds gross weight and one for 2150 pounds. In each case, use the chart that best fits your situation. Once you have the appropriate density altitude you’ll need to do several things. 1. Use that density altitude and the “Rate of Climb vs. Density Altitude” chart to get an average feet per minute. Earlier in the chapter, the handbook notes the best rate of climb is at 85 MPH, so, you should use that figure to estimate distance from the airport when Top of Climb (TOC) is reached. To help, please notice that 85 MPH is about 1.4 Miles per Minute. Also note, since weather is in Celsius and Knots, you’ll need to convert into Nautical Miles to do wind correction. 2. Once you’ve found your climb rate and TOC estimate, you can work on the rest. Start by using the Power vs. Altitude chart to determine fuel burn and percent power at the appropriate density altitude. 3. Once you’ve determined what percent power, use that to help determine True Airspeed from the True Airspeed vs Density Altitude chart. Again, this airspeed (or the wind speed) will need to be converted since one will be in MPH and the other will be KTS. To your second specific question, you should use True Airspeed as your base for determining ground speed. All the indicated airspeed charts and calibration error charts are trying to get you to a true airspeed for calculating ground speed. This chart tries to give you all that in one place. Because these charts are “light” I would definitely recommend rounding pessimistically during your calculations. It would be better to over-estimate time and fuel usage, while under-estimating ground speed rather than the opposite. I hope this helps. If it isn’t clear and you and your colleague would like me to walk through this, send me an email at Scott.Koon at online-CFI.com and we can talk about setting something up. I’m happy to speak with your CFI, too. Please note: My legal team recommends me saying that this only an example using sample information. To ensure a safe flight real planning must be done using real-world conditions and the specific performance charts for your aircraft.
@@ScottKoonCFI Oh my goodness! You are so generous and I am so grateful for your time. I have the original POH that I keep in the plane and I have a reprint that I ordered from Airspruce that I keep in my flight bag. I think the reprint differs slightly (extra chart maybe). Your reference to the Altitude Conversion chart really opened my eyes because, some how I have missed this chart after I searched and searched... did you sneak it in there? I will copy and paste this comment into my Apple notes. As for the Indicated to Calibrated speed conversion chart question. I'm not sure if I got your message. I understand that the goal is to get to True Air Speed (Indicated > Calibrated > True) in order to make the wind/ground speed calculations on the wind side of the E6B - BUT - I am missing the Calibrated Speed "link". There isn't a chart that I could find in the POH. I'm guessing, by pessimistically rounding you mean that I should just minus a knot or two from the Indicated Air Speed to estimate the Calibrated Speed. I may just take you up on your offer. Thank you so much Scott Koon!
Hello. Very interesting. I used to fly a Cherokee 140, but haven’t for awhile… so don’t have the handbook anymore-it went with the airplane. But I remember using the charts… Here is a link to the online POH I used. houltonflyingclub.com/wp-content/uploads/2017/04/Cherokee-140-Owner_s-Handbook.pdf. This was published in 1964, so it should be at least close... In any case, the altitude conversion chart should be on page 26. The Power VS Altitude charts are on page 24 and 25. The True Airspeed vs Density Altitude charts are on pages 22 and 23. As for rounding pessimistically, it sounds like you have the general idea. If you’d like more detail, I do have a video that talks about it. Here is the link: ruclips.net/video/7AkwJ8SLckI/видео.html Just let me know if you’d like to arrange a live chat. Take care, fly safe, and have a great day!!
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
You had me at, “Today we’ll be using the Piper chart”
Awesome! Glad to hear it! Stay tuned. More Piper charts to come! Thank you for watching!
You don't understand how helpful this was to me. My hometown airport is in the Los Angeles area and calculating altitudes for all the waypoints I need gets extremely complicated. Thank you
Awesome! Glad you found it useful! Thanks for the comment!
Excellent video, very well explained!
Thank you! Glad you found it useful!
small tip - instead of interpolating the values for wind (or any values for that matter) use the values at 2/3 of the climb and for descents use the values at 1/2 of the descent.
This is because values dont vary liniarly.
Thanks for the comment and thanks for sharing. This sounds like an easy method for planning outside of a test or check ride because you are right, the values don’t always vary linearly. Another short cut is to just use the next, least-favorable value in the table or chart (I call it rounding pessimistically). In General Aviation it is almost always better to plan to need more gas and not use it. However, most of the DPE in our area want to know you can use the FAA-approved tools during your check ride. So, for now that means knowing and understanding interpolation.
One question I have for you, is how did you decide to use 2/3 of the value during climb and 1/2 of the value during descent? Was it based on a table, calculations or a “rule of thumb”? Thanks again for the comment.
Good Job again Scott!
Thank you!
As usual, a star :)
Thank you!
How come for “rounding pessimistically” for the airport elevation we go down, but cruise altitude we go up? Thank u so much for a fantastic video ! Subscribed
Thanks for the question. It is a very good one. My reasoning is that the least desirable outcome would be to climb for a longer period of time because it would use more fuel. The larger the difference between the pressure altitude of the airport and the pressure altitude of cruise the longer the climb would take. With that in mind, I rounded the cruise altitude up and the airport elevation down. I hope that helps. Thanks again for the question! And thanks for the Subscribe!!
Hi sir, great job. But, i could not understand why you assumed our TAS was 90 kt. In the climb chart, our IAS is 76. So, we should calculate our TAS based on that speed. We can calculate it by using EB6 as our altitude and OAT is available. I calculated as 85 TAS. Then, we add tailwind in this case which is almost 8 kt. Finally, our ground speed is 93 kt. Am i missing something?
Perfect question. And, to be honest, unless the climb is a long one, I’m not sure there will be enough difference between the result of your answer and mine to matter much for planning (I believe the difference in distance during the 8 minute climb would be 2/3 of a NM).
In the video I note that the text section of Chapter 5 states “The time, fuel, distance to climb chart assumes no-wind conditions”. It further states “the effect of winds aloft must be considered by the pilot when computing climb, cruise and descent performance.” But it doesn’t suggest a specific method for doing so.
There are three reasons I don’t do it the way you did. These don’t disqualify your method, they are just the reasons I don’t use it. First, angle of attack (especially high angles of attack) can impact IAS accuracy. So, even though your airspeed indicator says 76 kts, you may not actually be at that airspeed. Second, if you picture a climb in profile, it is (sort of) a right triangle with the distance you move through the air as the longer hypotenuse and the distance over the ground a shorter base side. Third, during a climb your altitude and temp (and therefore true airspeed) is constantly changing as you climb, so which true airspeed do you use? Again, the differences will likely be minimal, so perhaps you could just use the worst TAS. In any case, all these factors complicate the calculation of ground speed and the effect of wind.
If you reduce the no-wind times and distances from the results of the chart back into KNOTS, you will get something over 76 kts (in fact the example used on the chart in Chapter 5 results in an “over the ground airspeed” of 80 rather than 76 kts). So I use that as the basis then factor the effects of wind as shown in the video. Still not perfect, but it attempts to overcome the issues I mentioned above.
As noted above, there doesn’t seem to be a single, approved method for doing this so if your instructor taught the method you describes please continue to use it.
Thank you for the question. I hope this helps explain why I did the calculations as I did.
@@ScottKoonCFI In total, i got your point. Thank you for answering but i have more questions if you dont mind. 1. "angle of attack (especially high angles of attack) can impact IAS accuracy. " Why is that? IAS is not affected by compresibility or position errors. IAS should show exatly the affect of dynamic pressure, right?
2. The reason why you took 8 minutes time as fixed and calculate the new distance from there is wind doesnt affect climb time, is that right? It doesnt come naturally tough. Is there any advice for me to visualize that fact better?
3. "a right triangle with the distance you move through the air as the longer hypotenuse and the distance over the ground a shorter base side." You mean if we take 98 instead of 93 (my version of GS) we are closer to that hypotenuse side as this distance is longer and we are closer to more realistic calculation?
Sorry for overwhelming questions but i try to learn as much as i can. Thanks for your patience and interest.
❤❤❤❤❤
Thank you!
Scott - I'm learning to fly in my 1965 Piper Cherokee 140 and the performance charts in my POH and AFM are uhm... a bit light. They're 2 axis graphs with "standard altitude" on the "up" axis and FPM (for the rate of climb) going across but there is nothing adding the temperature element to the equation. I would assume in this case I would use density altitude instead of pressure altitude. You're the one RUclips CFI that uses Piper (I've grown to loath the assumption that everyone learns in a Cessna 172) but your Piper is a couple decades in the future. I have an excellent CFI but he's never dealt with uh... uhm a vintage aircraft such as mine (I still have 1970's avionics - no GPS). Another curious aspect to this POH/AFM - there's no "Calibrated Air Speed" chart. I asked another 1965 Cherokee 140 YouTubing owner (who's also on the learning journey and our planes are very close in serial numbers) and he too has nothing. So to distill the two questions: Do I use DA instead of PA with my performance charts? Do I just use INDICATED if it's CALIBRATED when calculating my True Air Speed?
Jeffrey. This is an excellent question. And I apologize, the answer will be long.
I was able to grab a copy of a Cherokee 140 Owners Handbook. You described it perfectly. The performance charts are “light”. However, I would recommend the following.
To your first question… Yes, you will need to calculate density altitude in order to calculate performance. You can do that two ways. First, you can use an E6B (either electronic like Sportys, or the whizwheel) or use the “Altitude Conversion” chart in part IV of the handbook. Both should provide similar answers. By the way, the charts used in my videos actually use density altitude too. They just build the calculation into the single performance chart. Yours requires separate charts.
Also, please notice that each of the performance charts in your handbook has two versions-one for 1950 pounds gross weight and one for 2150 pounds. In each case, use the chart that best fits your situation.
Once you have the appropriate density altitude you’ll need to do several things.
1. Use that density altitude and the “Rate of Climb vs. Density Altitude” chart to get an average feet per minute. Earlier in the chapter, the handbook notes the best rate of climb is at 85 MPH, so, you should use that figure to estimate distance from the airport when Top of Climb (TOC) is reached. To help, please notice that 85 MPH is about 1.4 Miles per Minute. Also note, since weather is in Celsius and Knots, you’ll need to convert into Nautical Miles to do wind correction.
2. Once you’ve found your climb rate and TOC estimate, you can work on the rest. Start by using the Power vs. Altitude chart to determine fuel burn and percent power at the appropriate density altitude.
3. Once you’ve determined what percent power, use that to help determine True Airspeed from the True Airspeed vs Density Altitude chart. Again, this airspeed (or the wind speed) will need to be converted since one will be in MPH and the other will be KTS.
To your second specific question, you should use True Airspeed as your base for determining ground speed. All the indicated airspeed charts and calibration error charts are trying to get you to a true airspeed for calculating ground speed. This chart tries to give you all that in one place.
Because these charts are “light” I would definitely recommend rounding pessimistically during your calculations. It would be better to over-estimate time and fuel usage, while under-estimating ground speed rather than the opposite.
I hope this helps. If it isn’t clear and you and your colleague would like me to walk through this, send me an email at Scott.Koon at online-CFI.com and we can talk about setting something up. I’m happy to speak with your CFI, too.
Please note: My legal team recommends me saying that this only an example using sample information. To ensure a safe flight real planning must be done using real-world conditions and the specific performance charts for your aircraft.
@@ScottKoonCFI Oh my goodness! You are so generous and I am so grateful for your time. I have the original POH that I keep in the plane and I have a reprint that I ordered from Airspruce that I keep in my flight bag. I think the reprint differs slightly (extra chart maybe). Your reference to the Altitude Conversion chart really opened my eyes because, some how I have missed this chart after I searched and searched... did you sneak it in there? I will copy and paste this comment into my Apple notes. As for the Indicated to Calibrated speed conversion chart question. I'm not sure if I got your message. I understand that the goal is to get to True Air Speed (Indicated > Calibrated > True) in order to make the wind/ground speed calculations on the wind side of the E6B - BUT - I am missing the Calibrated Speed "link". There isn't a chart that I could find in the POH. I'm guessing, by pessimistically rounding you mean that I should just minus a knot or two from the Indicated Air Speed to estimate the Calibrated Speed. I may just take you up on your offer. Thank you so much Scott Koon!
Hello. Very interesting.
I used to fly a Cherokee 140, but haven’t for awhile… so don’t have the handbook anymore-it went with the airplane. But I remember using the charts…
Here is a link to the online POH I used. houltonflyingclub.com/wp-content/uploads/2017/04/Cherokee-140-Owner_s-Handbook.pdf.
This was published in 1964, so it should be at least close... In any case, the altitude conversion chart should be on page 26. The Power VS Altitude charts are on page 24 and 25. The True Airspeed vs Density Altitude charts are on pages 22 and 23.
As for rounding pessimistically, it sounds like you have the general idea. If you’d like more detail, I do have a video that talks about it. Here is the link: ruclips.net/video/7AkwJ8SLckI/видео.html
Just let me know if you’d like to arrange a live chat. Take care, fly safe, and have a great day!!
This doesn’t account for wind tho ?
But it does. Starting at 5:05, the video discusses how to account for wind. Thanks!