Aircraft Performance EXPLAINED (PPL Lesson 51)
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- Опубліковано 23 лис 2022
- How does pressure altitude, density altitude, humidity, and aircraft weight affect the performance of your aircraft? This video explains all that and everything else you need to know about airplane performance. I also explain crosswind component charts and the how to use the clock method to determine your crosswind component. This is Private Pilot Ground lesson 51! This training is intended to follow the aeronautical knowledge areas in Part 61.105 section b for single engine aircraft.
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You explain things better than anything I have seen online or in books, very much appreciated!
Thanks! That means a lot!
I just hang around until another airplane kinda like mine takes off and if he doesn't crash I figure I'm good to go.
Lol
I lol'd
Lol
Man you really help me understand all about performance with your rule of thumb the 4h´s
Have a good flights!
I am glad I came across your channel, I am 20y Current VFR pilot, and it So nice to hear all that again.. I will probably watch them all
Awesome! Thank you!
very comprehensive tutorial on a very important subject
Thanks!
Love all your videos, thanks so much for helping me and all of us on our way to the privilege of flight!
You’re welcome Dan! Thanks for watching!
I've watched quite a few videos on this subject but this is the first one that actually "clicked" for me. Thank you!!!
Awesome! You’re welcome!
Awesome!!!! A new video!! Thanks for posting all of this content!
Thanks Al! Happy Thanksgiving!
This video and your series would've saved me a lot going through this in college right now, I have my written in a month, this is truly well explained. Thank you!
You’re welcome! Thanks for watching! Good luck on that written!
thanks for these vids and i love that you said a summary at the end since this is all verry complicated for people like me that are new to aviation
You’re welcome! Thanks for watching
This was just wonderful ,thnak you so much for your time spending and nice presentation,well done
You’re welcome! Thanks for watching!
Thank you for your time to explain these things.
You’re welcome!
🛫📖🛬
Happy Thanksgiving Josh.
This is one lecture that is really needed because so many students and holders of ppl's are lost in the fog when they are asked to explain this or trying to teach someone else.
Most people cram this information in right before they go for their flight test and after that is complete it doesn't take long for the memory to start to fade, especially if you're not using it quite frequently.
Great work Josh as always you're doing a great service for a lot of people, I hope they're smart enough to take advantage of it.
GOD Bless
📖🛐✈️🐆
Happy Thanksgiving! Thank you so much!
WOW !! That was a great video!! I really enjoyed all the ties of each component together and how they affect each other ! Not gonna lie I will need to watch this a few times :) Great Job !!
Thanks Tom! That means a lot!
Appreciate the effort you put into this
You’re welcome!
Obviously, a very good flight instructor - well done, and thank you.
Thanks! I appreciate that!
Another great video with excellent info!
Thank you!
Thx Josh for all the cool videos and lessons
You’re welcome! Thanks for watching!
Awesome video as always, Josh!
Thank you so much!
Thanks for these great lessons!!
You’re welcome! Thanks for watching!
Excellent training video.
Thanks Simon!
Best video out there thank you
Thanks Troy!
Explained very well!
Thanks!
Great video Josh!
Thanks!
Hey, this is some excellent content
Thank you! That’s my goal!
Thanks for that clock method...I've been flying since 2000 1st I'm hearing about this method. I'm pretty good at guestimating calculations but this is very useful
Awesome! Yeah, it’s an excellent tool! Thanks for the comment!
Amazing, man
Thanks!
Excellent video Josh !! - Happy Thanksgiving
Thank you! Happy Thanksgiving to you too!
With all due respect, both the engine and the airplane perfom based on density , in other words DENSITY altitude , where the temperature has a significant effect
Lift = ½ density × TAS² × area × Cl
Cl = lift coefficient = AOA × dcl/da
Cl = AOA × 0,1047 × AR/(AR + 2)
AR = wing aspect ratio = span²/area
now density = press / (R × Tabs)
R = 8314 /29 Joule/ kg K
The engine power is also proportional to density
at any pressure altitude cold air is denser than hot air.
The designation density altitude takes that into effect.
The airplane performs according to Calibrated air speed.
As you did say .
sea level density × CAS² = dens × TAS²
TAS = CAS × √ (SL dens/ dens)
I believe you may need to get a little farther into the video. I include density altitude in the discussion
@@FreePilotTraining Sorry, my mistake
just erase my comment but the equations might be useful for you.
I just love these videos.... How do you determine whether you add or subtract the conversion factor from the field elevation?
Thank you! You always add them. When you come up with a negative number you add the negative to the positive and that reduces the altitude. Just like high school math
@@FreePilotTraining ok.
What if there was two examples 29.92-30.06=-0.14*1000=-140
Field elevation is 16. -140+16=-124
Second example is 30.06-29.92=0.14*1000=140
Field elevation=16
140+16=156
Which of the two would be the correct way of performing this calculation?
I’m not sure why I’m confused 😩
@@ProdbyBarryB your PA in that example would be -124 as you calculated in the first example. It’s just confusing because you’re so close to sea level and it seems weird with a negative number
@@FreePilotTraining ok thank you!!! I’ll continue to support this great channel!!
@@ProdbyBarryB thanks! That means a lot!
Excellent!
Thanks!
Base leg 1.4xVSO and final 1.3xVSO. Most instructors teach well above that. A C-172 can be landed at 52 kts with full flaps but just about all CFI’s want you at 60-65 kts for safety. Remember control speed with pitch and decent speed with power. I reduce my power to idle as the plane settles, makes a much smoother touchdown.
This is very true. Thanks for the comment!
Great job
Thanks!
Very informative video! Would it be possible for you to add chapters in future videos? It makes it a little easier if I want to turn back and find something in your videos to use for studying PPL theory :)
I definitely want to do that. I need to figure out how. Lol
@@FreePilotTraining that's easy. You just enable it in the settings for the video, and then type in the video description for example 0:00 XXX 2:30 XXX 4:50 XXX etc. :)
@@flymexx320 thank you so much! I will work on this when I get a chance!
OHJ MAN ! U SHOULD HAVE BEEN MY FLT INSTRUCTOR GOOD JOB
Thanks! I appreciate that!
48:15 pitch controls airspeed, and power for altitude, applies at any airspeed, not just slow flight. This is mathematically correct and provable, and is necessary to understand for aircraft design. I actually just taught this as a STEM lecture last week in fact, showing the math in the lecture.
There used to be a subreddit for people like you. I don’t know if it still exists, but it was called r/iamverysmart. You’d fit right in
@@tylerbrown4483 sounds like jealousy to me. Knowing what engineers knew way back in the 1940s is nothing special. You don't have to be very smart to read a book and learn such things. But, then again, illiteracy is on the rise in recent years.
@@SoloRenegade it’s not that what you’re saying is wrong, but that it’s overly reductive to the point that I feel confident you’re not as educated on the subject as you think you are. And it’s how smug and pedantic and self-satisfied you are in making and qualifying your silly correction.
You know what he was trying to say, that below L/Dmax you can’t pitch up and trade air speed for altitude to any effect, which is true. You’ll stall really fast if you try it. Whereas above L/D max you can certainly pitch up for altitude, at least until your airspeed bleeds down to L/D max, and if you pitch gently with good power you won’t go below L/Dmax at all and you’ll just establish a climb.
But you felt the need to take it in the most literal way possible and offer a correction in the tone of a 14 year old with a severe case of the dunning-Kruger. One read through Stick and Rudder doesn’t make you an expert on fluid mechanics.
At 28:57, what video are you talking about please? I don't quite get the topic you refer to in order for me to search for it from your channel.
ua-cam.com/video/-fRhVbseTx0/v-deo.htmlsi=r39OvEHhUVHBux6z
This is your best video yet! Do you have any discount codes for your merch? $70 is just a little bit too much for a frugal flyer me to pay for a hoodie and a hat. Anything helps 🙏🏼
I can’t figure out how to offer coupons, BUT my merch store should be having a sale tomorrow of 22% off of everything. Or if you’d rather, you can do free standard shipping if you order between 16-20 Feb.
At 30:39, I'm wondering why I was told that we should never land with tail-wind?
Basically, it could cause you to land way too long. If you have a short runway, you could easily go off the end of you don’t know how to account for the wind
Question! I came here to see your recommendations for calculating take off distances using normal procedures, since the Cessna 172 POH does not provide a chart for that. Foreflight offers a Safety Distance Factor so I can use that to help the calculations. You recommend doubling the take off distance, and I agree, but you throw in the caveat that "if you're below these numbers, I recommend you use the short field takeoff procedures just in case." I just wanted to clarify which numbers you're talking about being below? Do you mean if you double the takeoff distance and the runway is shorter than that distance? Thank you in advance!
Great question Ryan. So as I recommend, I like to double the distance for a normal takeoff. If my short field takeoff distance was 1,500 feet, then I’d say it would be fine to do normal procedures as long as the distance is 3,000 feet or more. If the distance was 2,999 feet, I’d just do a short field takeoff. It doesn’t hurt to practice short field takeoff procedures anyway after you’ve got that license.
Great question Ryan. So as I recommend, I like to double the distance for a normal takeoff. If my short field takeoff distance was 1,500 feet, then I’d say it would be fine to do normal procedures as long as the distance is 3,000 feet or more. If the distance was 2,999 feet, I’d just do a short field takeoff. It doesn’t hurt to practice short field takeoff procedures anyway after you’ve got that license.
@@FreePilotTraining Thank you for that and for the reply!
It is generally bad practice to round or try to add safety margin by padding steps within a calculation. (This applies to many subjects, not just aviation.) Unfortunately I see this a lot in the CFI world in an erroneous, though well intended, attempt at improving safety.
Do the calculation to the best availible accuracy, then determine how much safety buffer you want to add at the end. Rounding up and adding margins at intermediate points just increases the uncertainty of the calculation leaving you with an arbitrary unkown amount of buffer.
To be clear, I am talking about the proccess of calculation and use of tables. If you know your inputs have a range (margin of error in the measurment) then it is ok to do the calculations using the conservative side of those inputs. This input selection is different from fudging the actual calculation or chart-reading process.
Same goes for fuel calculations, eta, weather, weight and balance. Do the most accurate calculation you can then add in adjustments for specific factors and finally add the safety margin.
You’re the first person I’ve ever heard say that. If I add safety factors in my calculations, I do not doubt my numbers. I have more confidence in my numbers because I know I built in multiple safety factors. Because of this, I’m always pleasantly surprised by the capabilities of my aircraft, and adding ONE safety factor AT THE END of your calculations does not account for the fact that you may have made a mistake, and EVERY human will make mistakes in their calculations. If you made one mistake and added one safety factor at the end, you have created more risk because you cannot even make ONE mistake in your calculations. Doing so could result in disaster. I do agree however, that the numbers you come up with should never be blurry. You should never consider your performance numbers negotiable after you’ve made a calculation, even if safety factors were added through the process.
How do we set for 75% power at different altitudes on steam gages only?
Great question! Your poh shows you the basic horsepower relationship to RPM and pressure altitude in the cruise table. So, you use your tachometer
@@FreePilotTraining thx
No problem
Bedankt
Thanks for the Super Thanks Rob! It means a lot
💯 🙌🏼
🙌🏻
10% for each 9 knots, but what if i have, say, 15 knots or 5 knots?
Personally, I would add 5% for 5 knots in that case. It’s not accurate, but it’s conservative
I think you made an error at about 44:30. 28 kts * sin(45) = 19.8 kts. Below the limit, not over.
That said, I do love this and ALL your videos. Thank you for the hard work!!!
I appreciate this. You are probably right, but that raises a good point about these charts they aren’t always accurate. These calculations are based purely on the charts, but great catch though
Thanks!
The point is that it is at the recommended max within practical accuracy tolerances. (not a hard limit anyway) The crosswind chart doesn't need accuracy to tenths because the weather sock isn't that accurate, and the pilot wouldn't notice a 5% difference anyway. (1/20 is 5%)
Right at the beginning you correctly say ISA sea level temperature is DEFINED as 15°C
What you don't say is that the temperature lapse is also DEFINED as - 6.5 °C per 1000 meters elevation change , not pressure measured altitude .
When in reality the temperature distribution with altitude differs from this CONSTANT -6.5 °C lapse , the altitude measured with an altimeter setting of 29.92 inches or 1013.25 hektopascals, the new name for millibars, then the indicated altitude is different from elevation, true altittude in feet. Example there is an inversion in temprature, meaning it gets warmer across that inversion, then the altimeter will show a significantly HIGHER altitude: The surrounding terrain is higher. Yes that has led to controlled flight into terrain.
I believe I mention that somewhere in here. If not, I’ve mentioned the lapse rate in multiple videos
The aeronautic family try in many ways to make things safer, but in this instance of using the term "higher density altitude" where as you climb higher the air is thinner and therefore less dense. Seems to me the authorities that allow a confusing term to exist seems it is the authorities are the ones who are dense. Should be an overhaul of the terminology.
Yeah. I don’t like it either
620foot paved runway. Is there real? Where?
Lol, it’s not real.
@@FreePilotTraining thanks. Closest I’ll get to flying is my computer chair. Still I do very much enjoy your work. Guess I’ll have to continue playing at EGVP on their 900foot paved 04/22 runway.
The story of icarus apply to pilots alot eh, fly to high toward the sun and you will lose your wing and die 💀💀
In USA we dont use the metric system. ??? What country are you from?. Everyone knows the communist country are trying constantly to change our standard system !! Even though our system ( americans) have a more accurate outcome. I have seen your system introduced into American pilots causing fatalities. Because one or the other is using the American(standard) System and the other using what most communist countries use. Are you teaching American or others.? Is that why its free??
Dude. It’s a joke. Relax. The metric system is much better than standard
@@FreePilotTraining YOUR VIDEOS ARE INCREDIBLY COOL. THANKS FOR POSTING.!!! ENJOYING THEM ( NEW Subscriber)! BUT US OLD TIMERS ARE STILL HERE Lol. I'll edited the post. But it just don't feel right. Using a different system????
@@TheVoiceofKevinC thanks! It’s no problem! Sometimes jokes get lost in translation when folk’s watch my videos. I try to be somewhat aggressive with the humor because I think the lesson sticks much better. I hope to see you around the comments a lot more
Strictly for American. Talk fast and use weird words.
Lol sorry about that
@@FreePilotTrainingstill a good video though. I was trying to figure out what does; We spin (spin?) a corrected altimeter setting” is.