AirTalk.org Aviation discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Air density / O2 question          AirTalk.org Forum Index -> Aviation (Students) View previous topic :: View next topic   Author Message A Lieberma Guest Posted: Thu Nov 23, 2006 4:25 am    Post subject: Air density / O2 question Now that fall is here, and the air is much colder, "density altitude" isn't as much an issue. Thinking in my head is that for airplane performance purposes, the plane will enjoy the cooler temperatures and I won't have to lean nearly as much since there is more oxygen in the air. Also due to the cool air, I will get rather good climb performance. Believe it or not, the temp down here is suppose to be 30F on departure Thanksgiving morning, and this is the coldest weather I have ever flown in. Does this same concept apply to human physiology or am I thinking this through too much? By this, I figure if it's 90 degrees outside, and I am cruising along at 9000 feet, and I have to lean much more due to the less air available, would this concept apply to the O2 level in human physiology? Is there less air flowing through our blood stream in hot weather as compared to cold or is it a constant figure on climb no matter what the temperature is? I am flying from KMBO (Madison MS) to KEKY (Bessemer AL) and normally fly at 7000. I will have a first time passenger in the plane and figured if it was just as efficient to climb to 9000 just for the heck of it and get a more panoramic view of the world I will do this. I just don't want my sister to suffer O2 deprivation on her first XC flight in a GA plane *big smile*. She's already dizzy enough on the ground! Can't ask for more this Thanksgiving!!! Get to do what I love (fly) AND spend time with family!!!! HAPPY THANKSGIVING ALL. Allen Back to top Jay Beckman Guest Posted: Thu Nov 23, 2006 4:40 am    Post subject: Re: Air density / O2 question "A Lieberma" <lieberma (AT) myself (DOT) com> wrote in message news:Xns9883A718BC986liebermamyselfcom (AT) 216 (DOT) 77.188.18... Quote: Now that fall is here, and the air is much colder, "density altitude" isn't as much an issue. Thinking in my head is that for airplane performance purposes, the plane will enjoy the cooler temperatures and I won't have to lean nearly as much since there is more oxygen in the air. Also due to the cool air, I will get rather good climb performance. Believe it or not, the temp down here is suppose to be 30F on departure Thanksgiving morning, and this is the coldest weather I have ever flown in. Does this same concept apply to human physiology or am I thinking this through too much? By this, I figure if it's 90 degrees outside, and I am cruising along at 9000 feet, and I have to lean much more due to the less air available, would this concept apply to the O2 level in human physiology? Is there less air flowing through our blood stream in hot weather as compared to cold or is it a constant figure on climb no matter what the temperature is? I am flying from KMBO (Madison MS) to KEKY (Bessemer AL) and normally fly at 7000. I will have a first time passenger in the plane and figured if it was just as efficient to climb to 9000 just for the heck of it and get a more panoramic view of the world I will do this. I just don't want my sister to suffer O2 deprivation on her first XC flight in a GA plane *big smile*. She's already dizzy enough on the ground! Can't ask for more this Thanksgiving!!! Get to do what I love (fly) AND spend time with family!!!! HAPPY THANKSGIVING ALL. Allen I may be wrong, but doesn't the percentage of O2 remain constant until you get really, really high up in the atmosphere? IOW, the air density may change but there is no less actual O2 available? If your theory were correct (and it may be...I'm not actually sure...) then wouldn't the 12,500' oxygen requirement "float" with air density? You'd need suplimental O2 starting at 8500' on hot days but you wouldn't need it until say 14,500' on cold days? Very Good Q. Happy Turkey Day to you and yours as well. Jay Beckman PP-ASEL Chandler, AZ Back to top Morgans Guest Posted: Thu Nov 23, 2006 5:06 am    Post subject: Re: Air density / O2 question "Jay Beckman" <jnsbeckman (AT) cox (DOT) net> wrote Quote: I may be wrong, but doesn't the percentage of O2 remain constant until you get really, really high up in the atmosphere? Nope. Well generally speaking, anyway. Very, Very high, the O2 pecentages start to be different. Quote: IOW, the air density may change but there is no less actual O2 available? Air density and O2 available is a different way of saying the same thing. Quote: If your theory were correct (and it may be...I'm not actually sure...) then wouldn't the 12,500' oxygen requirement "float" with air density? You'd need suplimental O2 starting at 8500' on hot days but you wouldn't need it until say 14,500' on cold days? The hot and cold on the ground is not what would make the altitude float, but the temperature at and around 12,500. Still, it is hard to make a rule from that. Much simpler to put down a "set in stone" altitude. Some people don't need O2 at 12,500. Some need it at 8,000. Shoot, there have been around 100 people that have climbed Everest without a bit of extra O2. . Sure, they stayed at higher elevations, a step at a time to aclimate, but they still managed. If we opened the door to your pressurized airplane (if it could get that hight <g>) at that altidude, you would be unconsious in seconds, and dead in minutes. -- Jim in NC Back to top karl gruber Guest Posted: Thu Nov 23, 2006 5:12 am    Post subject: Re: Air density / O2 question "Jay Beckman" <jnsbeckman (AT) cox (DOT) net> wrote in message news:ql49h.364$zd1.36 (AT) newsfe16 (DOT) phx... Quote: I may be wrong, but doesn't the percentage of O2 remain constant until you get really, really high up in the atmosphere? IOW, the air density may change but there is no less actual O2 available? If your theory were correct (and it may be...I'm not actually sure...) then wouldn't the 12,500' oxygen requirement "float" with air density? You'd need suplimental O2 starting at 8500' on hot days but you wouldn't need it until say 14,500' on cold days? Very Good Q. O2 does change with altitude, theoretically. But due to mixing it stays the same at lower altitudes. Breathing is not density altitude related. Karl "Curator" N185KG Back to top Morgans Guest Posted: Thu Nov 23, 2006 5:27 am    Post subject: Re: Air density / O2 question "karl gruber" <removeskywagon (AT) gmail (DOT) com> wrote Quote: Breathing is not density altitude related. You might want to rethink that. It is a fact that we have more difficulty sustaining a good oxygen saturation at 10,000 feet. At 1 thousand, or two or even 4 thousand, it is not much different. Density altitude is measurable to our planes, in takeoff distance, drag, ect. The density change means there is less air to support lift. There must be less O2 , also. Is it a noticeable factor? Not really. Even when the altitude is getting lean for breathing, if you did not know what the density altitude was, you would be hard pressed to be able to tell the difference of a few hundred feet change. I have never seen any support to this argument, one way or the other, but logically, there has to a difference in breathing, if there is a change in density altitude - be it due to temperature, or elevation. -- Jim in NC Back to top Mxsmanic Guest Posted: Thu Nov 23, 2006 5:51 am    Post subject: Re: Air density / O2 question Morgans writes: Quote: Some people don't need O2 at 12,500. Some need it at 8,000. Shoot, there have been around 100 people that have climbed Everest without a bit of extra O2. . Sure, they stayed at higher elevations, a step at a time to aclimate, but they still managed. If we opened the door to your pressurized airplane (if it could get that hight <g>) at that altidude, you would be unconsious in seconds, and dead in minutes. You'd have a minute or two of useful consciousness. If you were used to the altitude or simply lucky, you could stay conscious for a much longer period. Death from hypoxia would take far longer--typically hours at least. The crew and passengers of Helios Airways flight 522 were at a cabin pressure of some 34,000 feet for two hours and were still alive when the aircraft hit the ground after flaming out, although most of them had been unconscious during that time. At least one person (a flight attendant) was still conscious without supplemental oxygen at the time the aircraft flamed out. David Sharp lived for hours on Everest without oxygen, although he was left to die. Lincoln Hall was without oxygen near the summit for more than 12 hours, remained conscious during that time, and recovered fully after a team abandoned their summit attempt in order to rescue him. -- Transpose mxsmanic and gmail to reach me by e-mail. Back to top Doug Guest Posted: Thu Nov 23, 2006 6:34 am    Post subject: Re: Air density / O2 question The human body is a density altitude dependent oxygen/carbon burning machine, yes. Much the same as an internal combustion engine. However, the human body can adapt to higher altitudes thus becoming "aclimatized" so it is more complicated. But move up 10,000' and yes you have less oxygen and yes your body will not perform as well. Also, there is mountain sickness which is due to high altitude (headaches etc). And of course there is severe altitude symptons when you get above 20,000' or so. Back to top Andrew Sarangan Guest Posted: Thu Nov 23, 2006 7:12 am    Post subject: Re: Air density / O2 question A Lieberma wrote: Quote: Now that fall is here, and the air is much colder, "density altitude" isn't as much an issue. Thinking in my head is that for airplane performance purposes, the plane will enjoy the cooler temperatures and I won't have to lean nearly as much since there is more oxygen in the air. Also due to the cool air, I will get rather good climb performance. Believe it or not, the temp down here is suppose to be 30F on departure Thanksgiving morning, and this is the coldest weather I have ever flown in. Does this same concept apply to human physiology or am I thinking this through too much? By this, I figure if it's 90 degrees outside, and I am cruising along at 9000 feet, and I have to lean much more due to the less air available, would this concept apply to the O2 level in human physiology? Is there less air flowing through our blood stream in hot weather as compared to cold or is it a constant figure on climb no matter what the temperature is? I am flying from KMBO (Madison MS) to KEKY (Bessemer AL) and normally fly at 7000. I will have a first time passenger in the plane and figured if it was just as efficient to climb to 9000 just for the heck of it and get a more panoramic view of the world I will do this. I just don't want my sister to suffer O2 deprivation on her first XC flight in a GA plane *big smile*. She's already dizzy enough on the ground! Can't ask for more this Thanksgiving!!! Get to do what I love (fly) AND spend time with family!!!! HAPPY THANKSGIVING ALL. Allen The amount of oxygen absorbed by your lungs depends on the partial pressure of O2, not the density. Therefore, pressure altitude is a better measure. This does not vary too much summer to winter. Back to top Dave S Guest Posted: Thu Nov 23, 2006 7:12 am    Post subject: Re: Air density / O2 question A Lieberma wrote: Quote: Does this same concept apply to human physiology or am I thinking this through too much? Yes.. Density altitude is what YOU feel, in addition to what the plane performs at. Back to top Ron Natalie Guest Posted: Thu Nov 23, 2006 7:33 pm    Post subject: Re: Air density / O2 question The "quantity" of O2 in the air is really not as important to your lungs as the partial pressure of O2. The pressure affects how your body takes it up. This is why you can breathe 100% O2 at 3psi or regular air at 14 and get the same effect. So density isn't so important. Set your altimeter to 29.92 and that will tell you the physiological effects. Back to top The_navigator Guest Posted: Fri Nov 24, 2006 6:22 am    Post subject: Re: Air density / O2 question A Lieberma wrote: Quote: Now that fall is here, and the air is much colder, "density altitude" isn't as much an issue. Thinking in my head is that for airplane performance purposes, the plane will enjoy the cooler temperatures and I won't have to lean nearly as much since there is more oxygen in the air. Also due to the cool air, I will get rather good climb performance. Does this same concept apply to human physiology or am I thinking this through too much? By this, I figure if it's 90 degrees outside, and I am cruising along at 9000 feet, and I have to lean much more due to the less air available, would this concept apply to the O2 level in human physiology? Is there less air flowing through our blood stream in hot weather as compared to cold or is it a constant figure on climb no matter what the temperature is? The air you use in your lungs is at 37oC all the time... 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