Every Pilot Should Know THIS About the Altimeter (Private Pilot Ground Lesson 32)
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- Опубликовано: 14 июн 2024
- How to use the Altimeter! I also explain everything else you should know about the altimeter. Plus, I explain the different types of altitudes that you need to know as a Private Pilot. This information will help you study for the Private Pilot written exam and the oral exam for your check ride. This training is intended to follow the aeronautical knowledge areas in Part 61.105 section b for single engine aircraft.
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Correction on the verbiage at 4:20... the video should say “any time you are at high density altitude” not “high air pressure” I apologize for the mistake
Great video thank you!
@@Virtualmix you’re welcome!
I caught that and came to the comments to see if anyone commented on it. :)
Thank you for this. I saw that part and got really confused, pulling out my FAA handbook to try and figure out what you were saying.
great video it all make sense the way show howit works thank you for this video.
Mate, I’m a Private Pilot and I remember spending hours trying to understand this years ago when I was studying for my PPL. These videos are honestly brilliant. If you were in the Branson area I would love to gain some knowledge as I’m pushing forward towards my CFI. Cheers brother!
Thanks Ian! I appreciate that! I love Branson. I wish I was closer
@@FreePilotTraining Anytime your’e in Branson let me know and we will do some dinner. My treat. It’s the least I can do for your time and service here giving away valuable information.
@@TheGhostInWhiteOfficial This is the best video by far on this topic and I’ve watched many videos… good luck on getting that’s CFI rating!
As others have mentioned, it's counterintuitive that at higher than standard temperatures, the altimeter reads lower than it should, since warmer air is less dense. The FlightInsight channel has a video called "High to Low Look out Below! I Put My Altimeter in the Freezer!" which explains that. The air pressure is the weight of the column of air above. At higher temperatures, that column of air expands upward, getting taller while containing the same amount of air. The Qnh setting at an airport is corrected for temperature, but at higher than standard temperatures the pressure at higher altitudes decreases more slowly than the standard lapse rate which the altimeter is calibrated for. At higher than standard temperature, the airplane has climbed through a smaller than standard proportion of the atmosphere at a given altitude, so more of the atmosphere is still above it, pushing down with higher pressure than at standard temperature.
I love this explanation.
The altimeter is such an overlooked piece of equipment... thank you for your detailed lesson!
Yes it is! You’re welcome!
High, hot, heavy, humid. Wow! What a handy memory tool. I've been struggling with that one, too, so thanks for the tip!
Yep! It’s a good one! Thanks for watching!
My brain just exploded
😂
Another great lesson! And great job on creating the clip. Well done!
Thank you!
These are Golden tips!!! Thank you for all you do, Keep it up!!!
I appreciate that! Will do! See you in the next one
From videos, checking the weather gives you a setting for the altimeter .
Excellent very clear explanation of an often confusing topic. Thank you!
No problem! Thanks for watching!
You are my savior. Thank you! Keep up the amazing work!
Thanks! I’ll keep em coming!
Very well explained! Thank you!
You’re welcome! See you in the next one!
GREAT JOB! I JUST NEED TO WATCH IT A FEW MORE TIMES ON A SLOWER SPEED! THANKS FOR THIS TRAINING!
Thank you!
I see now, the altimeter setting is very important for flight. Thanks for great explanations and video.
You’re welcome! Thanks for watching!
You did a great job explaining this topic. Thanks .
Thanks Derek!
I learned so manything
From you!
For me this is the most clear and easy-to-understand , thanks guy😊
You’re welcome!
Another great video!
Thanks!
Excellent video
Thank you!
You're always on top awesome 😎
Thank you!
Man, This one is very good. I have always had a problem understanding the altimeter setting. But, I will have to watch it again. Didn't know it was a couple of attitudes.
Thanks!
This is amazing!👍
Thank you so much!
very good
Thanks!
Grea video 🎉
Thanks!
Thanks!
You’re welcome! Thank YOU for the Super Thanks!
I’m learning a lot more with this training than with Jepessen ,thank you !
That means a lot! Thank you!
Not a pilot but considering taking lessons soon. I have been watching several of your training videos as well as some other flight training videos by other people. Your videos make the most sense to me and easier to understand than some others. I appreciate all the work you put into them and I did subscribe to your channel and will be watching all of your videos to learn as much as I can before starting lessons to have as much available knowledge I can perceive beforehand to help speed my training up. Thanks a lot.
Thank you Danny! I appreciate the compliment! That’s super motivating! I’ll see you in the next one!
This is all about flying an airplane I had to watch back videos in order to figure this out by the way
completed
It'd be interesting to see what NO2 could do for take off as well as touch and goes, but it'd also be interesting to see what would happen if oxygen were fed to the engine at high altitude. It probably wouldn't be cost feasible probably, it'd add stresses to the engine, (maybe???), the NO2 anyway. But it'd be impressive seeing a Cessna 172/182, walk off and leave other faster planes.
Lol, I’m sure there are videos out there. Probably not with Cessna 172s, but experimental airplanes can do all kinds of stuff like that.
best videos!
Thank you!
Question- when flying to/from an area of different pressures, you could avoid the dangers altitude change by obtaining the ATIS/AWOS and putting in the correct altimeter setting, correct?
Yes you can. If you are using “flight following,” when you are passed off to the next controlling agency, if the pressure is different they will often give you an updates altimeter setting
Great video! I just have a quick question at 9:05, How did you get the feel altimeter setting of 28.18? I thought the altimeter setting was 3018 and don’t you compare that with the internal pressure of 29.92 in the sealed aneroid wafers? Who is about 260ft difference. Thank you!
A commercial pilot told me that it is also called Attitude, if you are plunging, they say the plane is having a bad attitude.
cool
Thanks!
I have always been interested in flying and just started thinking about taking lessons. Your explanations are appreciated.
For most this question is probably common sense, how do you know what the barometric pressure is where you are flying into, if you are going to another airport?
Awesome! Thank you! Happy to do it! You get the local altimeter setting at the field before you arrive. You will receive this on an AWOS,ASOS, or ATIS frequency where we get the weather prior to your arrival at the field
@@FreePilotTraining yes, but how about along the way? Do you get regular barometer setting updates, and from whom?
@@gvc76 you can listen to the different weather frequencies along the route, but if you are receiving VFR flight following, they will periodically give you an update
@@gvc76 ATC will give you the local altimeter setting along your route if you speak to them (when IFR or VFR flight following). Since ATC is responsible for IFR aircraft separation, they want all aircrafts in the same area to use the same altimeter setting. Before take off or landing, you get the altimeter setting from the ATIS or ASOS/AWOS. If you can't get the local altimeter setting while on the ground (for example before take off from a private field) the procedure is to set the altimeter to the field elevation.
This is much more complicated than I thought it would be.
Yes, unfortunately it is. That’s why it’s an important lesson
Yes, Just give yourself time to let it sink in, it does make sense but took me awhile to understand…
I kinda understood few but still am confused.I better learn this. do you have more examples?
I do, but they’re mixed in with a lot of my future lessons
Studying for PPL, so which attitude to use on an airplane?
I’m assuming you mean altitude? If so, when you are flying, you will primarily use indicated altitude, and when you are calculating performance you will primarily use density altitude and pressure altitude. Absolute altitude is used a lot in the airplane as well, but you will have to make quick calculations to find those numbers unless your lucky enough to have a radar altimeter
Is it better to set the altimeter before every flight based on the airport you take off from or would it be better to leave it on msl? Would the answer change based on I'm flying around for fun or I'm going somwhere with a different altitude?
Set the altimeter before you takeoff. You can update it periodically in flight by listening to nearby AWOS and ASOS frequencies
Awesome videos. I know how to give the correct answers but it annoys if I don't fully understand why. With the altimeter reading higher than you actually are, how does that work? As denser air molecules are found the closer you go to the ground I would think the altimeter would read lower than you are.
Is it that whole portion of sky is compressed?
My logic so far would be there's a full jar of water, we are floating halfway with a reading of 10,000feat for example. Then the next jar is half full and again we're halfway at 10,000 feet but when compared to the other were closer to the bottom of the jar but with the same reading?
Think of it like a swimming pool. As you swim closer to the bottom of the pool, there is more pressure on your ears. Technically, the altimeter is nothing more than a pressure gauge that works backwards. The lower you are, the more pressure there is, so the altimeter gets lower. Hope this helps you
@@FreePilotTraining ok I get there's more pressure the lower you go. My querie is if you're at ground level in a pool that's 13⁰c why would the altimeter read higher than you are.ie( you're lower than you think you are)
@@FreePilotTraining Put simply just so I understand. With everything else equal I'm sitting in a float plane at msl, it's 15⁰c my altimeter reads 0.
I'm in exactly the same spot the next day however it's 13⁰c will my altimeter read higher than 0? If so why.
I’m confused like Daniel is. Using as slight modification to his example, if temp is 15C one day and your altimeter is reading 100ft, and the next day in the exact same spot it is 13C, that means the air is denser, so the altimeter would think you are lower than you were the day before. Maybe it reads 0 that day (don’t know the actual value, but my point is that it would read lower), when in actuality you are at 100ft MSL, so you are actually higher (100ft) than you think based on the altimeter reading of 0ft. Am I thinking about this the right way?
I’m confused like Paul and Daniel are. At 5:05 you say that because the Altimeter’s aneroid wafers were set at the factory at 29.92 Hg and roughly 59°F, if the temperature changes but the true altitude remains the same, the pressure on the aneroid wafers will reflect the increase or decrease in pressure. If hot temperatures spread the air molecules apart from each other thus causing less pressure on the aneroid wafers, wouldn’t that mean the wafers will expand thus indicating a higher altitude than you really are? This is my understanding and doesn’t jive with hotter temperature means you are higher “than you think”. Please help me understand this concept. Thanks and I love your videos!
So what happens if you adjust your altimeter at airport A as per ATIS. When you're getting ready to descend at airport B, they don't have ATIS or AWOS and all you have is the airport elevation. How do you adjust your altimeter in flight to get your current elevation? Given that you know you went from sea level to now you have a rough idea that airport height should be 2000 above sea level.
Good question. If you’re talking with ATC, they should give you a new altimeter setting. If not, find the closest airport on the chart and get the altimeter from them. I dont think there’s any way to use the field elevation in flight
Hello, dear Josch! I forgot to ask if the AOA is measured from the geometric or the reference line.
Geometric angle of attack, " - the angle between the airfoil chord line and the freestream velocity vector. Induced angle of attack, "i - the angle formed between the local relative wind and the undisturbed freestream velocity vector.
This is very confusing!
It’s measured from the chord line to the relative wind
"HIGH TO LOW, LOOK OUT BELOW" (which can be used with either air pressure or outside air temperature [OAT]) is the simplest way to remember the need to take pressure and/or temperature changes into account. The opposite adage: "LOW TO HIGH, HIGH IN THE SKY", or "LOW TO HIGH, YOU'RE IN THE SKY" also works well.
It was good that you pointed out that setting the altimeter to the current reported altimeter setting is preferred over setting it to field elevation, since some airports have more than 100 feet difference between opposite ends of the same runway (LAS -- Las Vegas --Harry Reid [aka McCarran] International Airport springs to mind -- the difference between the east and west ends of Runway 26R and 8L is 148 feet).
Thanks for the comment! 148 feet is a huge difference! I definitely don’t want to be that much off on my altimeter setting
DAAAAAMMMMN I live in Vegas and had no idea! I'm in a&p school rn 9:59
one thing if you could explain with example why when temperature is higher than 15 then we are higher than we think
Because the air pressure is reduced in hotter temps
8:06
Look at that image.
High pressure on the left, low pressure on the right.
Now high pressure = cool air, cold fronts, lower temperatures, dense air
And low pressure = warmer air, warm fronts, higher temperatures, rarer air
Is this correct?
I found images on Google showing similar isobars going down from high pressure to low pressure areas, but the temperature was hotter on the left and cooler on the right. What am I missing here? Shouldn't it be "Cold to Hot, look out below", instead of "Hot to cold, look out below"?
Ok, this is a great question. Non standard temperature does not affect your altimeter nearly as much as non standard pressure. There is a chart in the AIM and the PHAK that shows you exactly how big of a difference it is, but it’s relatively insignificant when the temp is somewhat close to standard. You might be think how much temperature affects density altitude
where do you get the temperature from?
ATIS or the METAR
At 5:04 shouldn’t it read “higher temps = higher pressure”?
Because, if it’s higher temp (hotter temp) then the air molecules will try to “push” out more and will result in more pressure. Whereas when the air is cold then air pressure drops because when it gets colder the molecules contract and “push” less.
For example a basketball or car tire can lose 1-2 lbs of PSI when it gets 10 degrees colder.
I could be using the wrong type of frame of reference here so correct me if I am. I’m still learning 😅
In AIM 7-3-1:
“When the ambient (at altitude) temperature is colder than standard, the aircraft's true altitude is lower than the indicated barometric altitude.”
That would mean the altimeter is reading higher than true altitude. That would mean the pressure would be lower than it should be (lower pressure = increase in altimeter reading)…
so wouldn’t that mean: “lower temps = lower pressure”?
Higher temps mean lower air pressure which makes pressure altitude higher. The warm low air pressure air doesn’t push up, it is picked up because it’s lighter
@9:36 , I thought that the higher the altitude, the less air pressure is? Why is it that bigger number 30.1 vs 29.92 as an example, the higher altitude it will read?? I’m so confused!
Bigger numbers like 30.10 means higher pressure and that means a lower pressure altitude. Hope that helps
@@FreePilotTraining@9:30, what does it mean when it says “the bigger the number, the higher the altimeter will read??
Why not set the altimeter to zero feet at the airport? I know in some other countries they use QFE. Why is it more important to use the standard barometric pressure?
At some airports where the elevation is higher, you may not be able to set the altimeter to zero. I believe most altimeters are limited to 28.00.” That would mean that If you are at an airfield where the field elevation is above 3,000, you may not be able to set the QFE to zero in this case. Also, if you are able to set the altimeter at zero, it will read your absolute altitude (height above the surface) for a short period of time until you fly into an area of different pressure, and unless you are getting constant air pressure updates, your altimeter would not be accurate. Also, if you fly below the altitude at which you set the altimeter to zero, your altimeter would read subterranean and that would not do you any good at all. Hope this helps you!
@@FreePilotTraining Thanks for the info.
@@ComdrStew you’re welcome!
3:15 remark about oxygen:
It is not the oxygen content (always 21% in the air, independent of altitude) that determines the engine power, when properly leaned, it is the density, that matters:
sealevel standart density : 1.225 kg/m³
21800 feet altitude: exactly half SLD
33013 feet altitude: exactly ⅓ SLD
12000 feet altitude: 1/1.44 SLD
all those for ISA conditions
Engine ouput power is proportional, given rpm, to density , of which 21 % is available oxygen , to burn the fuel, containing 43000 Kilo Joule per kilogram gasoline thermal combustion energy.
In the cylinder it is the amount of air, 78% nitrogen, does most of the work.
The rest is steam and co², the combustion products.
The mass in the cylinder prior to compression is volume times the air density.
I find you have stated two contradictory theories. At time stamp 3:42 you say as temperature increases, the static air pressure decreases. - (This is of course in an open system such as the atmosphere). Ex.) Assume you are at 5,000 feet and the temperature suddenly increases. According to that, the pressure would decrease proportionally to the temperature increase. The second statement I could not wrap my head around is at time stamp 5:09 when you mention, the temperature being hotter than 15-degree Celsius and being higher than you think(Altitude). I don't see how this could be possible according to the first statement. If the temperature is hotter, the pressure would be lower. This would cause the altimeter to read an altitude higher than you are, resulting in you being lower than you think(Altitude). This would be true for its opposite. If the temperature is lower than 15- degree Celsius, the pressure would increase resulting in the altimeter to read an altitude lower than you are. This would mean you are higher than you think(Altitude).
I have looked up the 2 contradictions and found when relating to a closed system such as a balloon or a pressure cooker, if you increase temperature that would also increase the pressure. Same for its opposite. If you decrease the temperature this would decrease the pressure. This is pressure and temperature in a directly proportional relationship. In this case the statement at 5:09 would make perfect sense. If the temperature increases the pressure would increase as well. Increased pressure would be reported on your altimeter as a decrease in altitude. This would result in you being higher than you think(Altitude). Something doesn't quite add up here. Can you please look into this. I know it's a bit confusing but just try and follow the logic. Thanks
Don’t read more into this than you need to. Pressure decreases as temperature increases. And your altimeter IS affected by this. It’s not as much as what you might think, and we typically don’t account for this when the temperature is higher than standard, because if you’re higher than your altimeter reads, it’s usually not a big deal. If you’re lower on the other hand, that’s when you can start running into towers and stuff cuz you’re lower than you think you are. When the temps are AT freezing and below is when you should start considering cold weather corrections
Thank you for being way more eloquent than I was. I had the same problem understanding this concept stated here.
You should make a video with an actual altimeter to better illustrate what you mean about adjusting it properly. Im not really understanding why the altimeter would read zero.
I’ll keep that in mind. Thanks!
For the 4H’s, why is it that with high air pressure the airplane suffers? Prior to that talking about 1min or so, it is mentioned that with low air pressure, the airplane performs badly. That makes me confused.
You found the mistake in this video. That should say “high pressure altitude”
Yeah but you didn't mention the black and white diagnals?
This is true... do you know what they are?
@@FreePilotTraining it's called the striped segment. It's visible below 10,000', while above, a mask begins to cover it until 15,000', where it is fully covered.
@@Virtualmix thanks! This might be a good “short” video for my aviation nuggets
7:29 -- please explain.
-- We know that every 1 inch Hg lower means 1000 feet higher;
-- We know that there is 30.00 inHg at sea level:
-- airfield is on 625 feet above sea level.
So I do an easy math: 30 - 625/1000 = 30 - 0.625 = 29.375.
But you say 29.9. Why?!
And as always, thank you for the video.
You may not have caught it, but the altimeter setting you are receiving IS NOT the actual altimeter setting at the field. It is the altimeter setting at sea level based on the current pressure at your field. Hope this helps
Kinda picky but you mention performance being related to the amount of Oxygen in the atmosphere. More accurate to say ”air” (which oxygen is only one element of). Otherwise brilliant video as always.
Yes, you’re correct. Thanks for the comment. Although, I guess technically, when it comes to engine performance, it is oxygen that affects the power that the engine produces
The more I hear about the altitude corrections, the more I think I want a radio altimeter for agl confirmation.
They are nice
You said low pressure is bad performance followed by high pressure is bad performance. Which is it?
Yes, I made an error right there. Low pressure and high pressure ALTITUDE = bad performance. Sorry about that
isn't the altimeter reading 3620 feet at 1:10?
No. The short fat one is 100s not 1000s
@@FreePilotTraining Thx, just bought MS FS 2020, I flown other sims usually with HUD, flying a Cessna, so no HUD:) Someday once I get to grips with things I'll transfer to the real thing hence the Cessna...
@@daysofgrace2934 sim work will help you so much! Ive seen it first hand
Awesome video, but you should back away from the microphone and cut out the high frequency of your voice with an equalizer. It'll make less mouth sounds.
Thanks! And thank you for the feedback! I will try that!
Free Pilot Training
You're very welcome, a lot of music recording DAW's (like studio one) have an equalizer you can put over your audio
Can you be my CFI
I am having trouble understanding how hot temperature causes you to be higher than you think you are. I thought hot air caused a lower pressure because the aneroid wafers are expanding due to the lower air pressure or higher density altitude perception by the altimeter.
Your altimeter is basically a pressure gauge. At high altitudes, there is less pressure. At high temperatures, there is less pressure so your altimeter will read higher
The aneroid inside is a nearly perfect vacuum, no molecules inside, temperature is velocity² of molecules, no molecules, temperature is meaningless.
A altimeter is essentially the ambient air pushing the aneroid flat against a calibrated spring and the displacement of this spring from full extension is amplified mechanically and displayed and calibrated to give zero altitude at the equivalent of 29.92 inches of mercury in a u-tube , connected on one side to a vacuum , and the other side open to the air on the beach on the ocean. With the knob you can change this displacement and observe it in the Colesman window, on a scale calibrated in pressure terms.
when the spring is unloaded by half it's full deflection the altimeter should display 17970 feet. ⅔ unloaded, the dial should read 27434 feet. Never unloaded completely unless you are an astronaut floating around the space station, the dial out of scale.
A chli compliziert , aber so isch es halt.
Mer wänd nöt unter de Furka Pass inne flüge, so wie die drü Venoms von Mollis vo der Staffel 11.
@@arturoeugster7228 Great explanation. Thanks
Higher temperature, higher pressure. That’s why when you move to an area with higher temperature, your altimeter indicate lower altitude. Isn’t it?
Higher temperature = lower air pressure
@@FreePilotTrainingIsn’t higher temperature lower air density and higher pressure? Otherwise why when we enter an area with higher temperature the altimeter is indicating a lower altitude than the real one? The altimeter is perceiving a higher pressure with respect to the standard atmosphere temp.
Higher temperature -> Higher pressure and Higher temperature -> Lower density.
No .
Great video. Watch your spelling - when listing things required in the aircraft you have "guage" not "gauge", and further on "acutally" instead of "actually". I'm sorry to do this but I am very pedantic and find spelling mistakes extremely distracting. I have only just found your channel so I will be going back to lesson 1 shortly.
Alan, thank you so much. I spend so much time on these videos, I don’t always catch all the spelling errors. I’m not a huge fan of this software since it doesn’t have spell check. Guess I should have my wife look over it before I upload. She sees all my mistakes 😂 anyway, I hope you enjoy the rest of my videos!