Density altitude is the biggest factor in aircraft take off on a given runway length, temperature, and altitude. I know this from firsthand experience as I used to be a private pilot – until my hearing got so bad that I decided I was a danger to myself and others. This study published in the Bulletin of the American Meteorological Society claims the number of days with a density altitude issue at some airports will increase per RCP model scenarios in 2050-2070. Of course they are assuming that the RCP models produce an accurate output, and that airplanes of the 2050-2070 era have the same airfoil efficiency and takeoff power of today.
Climate change and the impact of extreme temperatures on aviation
Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA.
Abstract
Temperature and airport elevation significantly influence the maximum allowable takeoff weight of an aircraft by changing the surface air density and thus the lift produced at a given speed (Anderson 1999). For a given runway length, airport elevation, and aircraft type there is a temperature threshold above which the airplane cannot take off at its maximum weight and thus must be weight restricted. The number of summer days necessitating weight restriction has increased since 1980 along with the observed increase in surface temperature. Climate change is projected to increase mean temperatures at all airports and significantly increase the frequency and severity of extreme heat events at some (Scherer and Diffenbaugh 2013; Donat et al. 2013; IPCC 2012). These changes will negatively affect aircraft performance, leading to increased weight restrictions especially at airports with short runways and little room to expand. For a Boeing 737-800 aircraft, we find that the number of weight restriction days between May and September will increase by 50-200% at four major airports in the United States by 2050-2070 under the RCP8.5 emissions scenario (Moss et al. 2010). These performance reductions may have a negative economic effect on the airline industry. Increased weight restrictions have previously been identified as potential impacts of climate change (National Research Council 2008; US Global Change Research Program 2009), but this study is the first to quantify the effect of higher temperatures on commercial aviation. Planning for changes in extreme heat events will help the aviation industry to reduce its vulnerability to this aspect of climate change.
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>>Unmentionable November 26, 2014 at 10:46 pm
>>I seriously doubt density-altitude due to high temperature at sea level will
>>ever be a flight limitation though, it has to be combined with actual altitude.
Oh, it can be. And extending the runway is not always the answer. Any airport with high ground or mountains around it, is going to have performance restrictions, no matter how long the runway is.
And then we have the WAT or Climb limitation, which kicks in at higher temperatures (no matter how long the runway is). The B737-800 starts getting WAT limited at 38º at sea level, and loses 5t of performance weight by 46º. At an airfield at 2,000′ altitude, the same weight limits occur at eight degrees cooler (30º and 38º). Extending the runway in these cases has little effect on overall performance.
But, as I said before, more advanced aircraft designs could easily overcome the proposed 2º increase in temperature, that the alarmists are forecasting.
And since there has been no Global Warming in 18 years – just what is the problem? Perhaps Coffel and Horton (the authors), should also investigate the dire problems aviation will face in the future, when aircraft start colliding with the offspring of Pegasus. Should TCAS be made compulsory for all winged equi? Now that is the real question…… 😉
R
“And since there has been no Global Warming in 18 years – just what is the problem?”
The problem is a former President’s daughters will (allegedly) have to forgo a jet flight to the Coral Sea because the coral will be gone for some completely unexplained reason, if the on-going total lack of change in global temperature continues to do nothing. I won’t go into here the fact that we natives were the ones who put it up for world heritage listing and debated and discusses and planned to create research and regulatory agencies to manage the coral reef, or that the workers on all construction sites, in all mines, in all trucks, trains, restaurant kitchens, cleaning toilets, teaching in class rooms and flying the public around from in cockpits are the very same people who elected to do all that to preserve the reef – AND STILL ARE BTW – and to likewise continuously pay a hefty price in on-going taxation to make sure that it was always preserved for all future generations of human beings to visit. Just a little thing there that Obama glossed-over and totally ignored, almost nothing at all really, as he grossly insulted us all with his baseless insinuation that the country was full of remorseless environmental vandals, and that the total lack of a temp increase for 18 years spells certain doom. But hey, who cares about reality when you have a snazzy teleprompter injected fantasy?
Re runway lengths and density altitudes, in all aircraft I’m directly familiar with the answer is to use a longer takeoff roll to rotate at higher speed and remove unnecessary payload weight (fewer people, less baggage, less fuel, perhaps necessitating a further fuel stop before destination) then fly within the certification limits and in all cases you’re going to get safely to cruising levels. Stay clear leeward ridge lines, best climb, turn early, std rate.
Yeah maybe some locations can’t build a longer runway, so takeoffs can’t be made faster, but there are always going to be those limits, and as you would know, there always has been. I don’t see any significant change/impact/disruption even if the models were right. In that case the economics, regs and operator practicalities would simply require a different aircraft type be used.
We also should not ignore that turbine aircraft are getting bigger and heavier with more thrust and payload with every iteration, in order to access the economies of scale efficiency dividends and that their numbers are increasing as well every year.
That is the real practical cap on airspace usage and capacity constraints (as I expect you understand), temperature is as I said, just one fairly minor factor within a much more complicated calculation, where other constraints are rather more significant than density altitude. Like you said, no temp change in 18 years – why are we forced to talk/debate nothing? (i.e. same problem/distraction at the G20 too … gee, how’d that happen?)
Now there’s a good question.
(Anthony/Mods, think I exceeded the link limit with a comment still in moderation )
meanwhile the Airlines keep figuring out ways to pack us in like lemmings in shinny metal boxes, more weight .. I guess they didn’t get the memo?
I was just wondering the other day if “Global Warming” would have a discernable impact on air pressures. More atmospheric heat, more atmospheric energy, more atmospheric pressure?
Instead of Global Warming, should we be calling it Global Pressurizing?
They say that the high temps on Venus are due to high pressures. High pressure fronts are often associated with higher temperatures than lower pressure fronts, at least from my layman’s view. Just curious, has there been any attempt to systematically look at whether atmospheric pressures have changed over time?
Atmospheric pressure (F/a) is a function of the total *mass* (m) of the air over a given unit of area (a), under the influence of gravity (g) according to the equation F=m*g. None of these factors will be significantly influenced by temperature. A gram of hot air weighs exactly the same as a gram of cooler air.
The issue for aircraft performance is air *density*, which varies with temperature AND humidity.
Read these:
http://www.pilotfriend.com/training/flight_training/met/atmos.htm
http://www.pilotfriend.com/training/flight_training/met/atmos_wt.htm
This is one of the posts that Sou (Miriam O’Brien) has chosen to comment on at HotWhopper. See my post at MoreOnMiriamO’Brien’sHotWhopper:
http://moreonmiriamobrien.wordpress.com/2014/11/27/miriam-obrien-says-various-views-flying-about-at-wuwt/
In this post, Miriam comments on about a dozen comments. Wow! (sarc off.)
More weight is overcome by higher thrust. Higher thrust of newer engines comes from burning about the same quantity of fuel at a higher temperature and pressure, in the core of a larger diameter turbofan engine, with a much bigger fan. The aim is to achieve a higher core exhaust pressure therefore a larger and/or faster spinning fan, so higher thrust for the same fuel. So they make larger jets with larger payloads to get a better margin return on investment, so can stay in (a profitable) business. That, and better airfoil shapes and avionics precision, is airline efficiency growth in a nutshell.
What you’re referring to are to be blunt, “the cheap seats”, (in Titanic terms, “Steerage Class”) and those seats only exist at low price due to those efficiency gains. So the cheap seats only exist due to that efficiency growth, and most people who fly can only fly because that efficiency made affordable airline seats possible, for a larger proportion of highly mobile people in the economy.
Sorry, not much dystopic consolation to offer but there it is, the filthy proletariate can enjoy flying with the Promenade Deck Class Jet-setters. Are you not ever so lucky when you think about it in those terms? And within the same jets you volunteer your mortal soul to fly there are also not-so-cheap seats, for the, er, more aspiration oriented, which look like this:
http://www.news.com.au/travel/travel-ideas/what-its-like-to-fly-on-the-20000-singapore-airlines-suite-class/story-fnjpj945-1227076691741
So keep working really, really, I mean reeealy hard and one day you may be privileged to blow $20k on not very much at all. No doubt, now that you realize you’ve been arriving at the very same destinations, for years, at comparatively negligible cost, this has cheered you up enormously, as you realize what a lucky sod you have been all this time.
The greatest weakness of the alarmist view is their flawed fixation on the static nature of things. We live in a dynamic and vibrant world where the only constant is change itself. The fact that everything is in motion and consantly evolbing is utterly ignored by those screaming about catastrphe.
Back in my day we called misjudgements involving density altitude, overgross weight, underestimated takeoff roll etc. Pilot error…….. now it’s climate change? ah! well you live and learn.
Easy fix:
*Arrive & depart in mornings or evenings
*Bigger wing or bigger engine
*Less weight (alarmists banned from flying….)
*Give the aero engineers a few minutes, they’ll figure it out.
*Biggest problem we face is when it gets colder, not hotter.
Ron Richey
N70NB
Easier fix: Don’t fly. Use the Internet for conferences and telework. The less time I spend around TSA agents the better I like it.
PS: Happy Thanksgiving
Here’s a link to a B-29 Flight Manual if such things interest you. Takeoff performance starts at about page 100. http://www.avialogs.com/viewer/avialogs-documentviewer.php?id=2717
With reduced lift comes reduced drag so overall there will be a benefit for most of the world’s air transport.
Either they fly lower to get the same limit point so do not have to climb so far or they can fly higher and save fuel. That is not so good for climate alarmists to publicise, is it?
Reblogged this on Centinel2012 and commented:
In the view of the Greens fewer planes would be a good thing!
As we say, it´s hard to fly like an eagle when you´re surrounded by turkey´s
apostrophe catastrophe – try turkeys
See
http://www.greatseal.com/symbols/turkey.html
http://www.chron.com/life/article/The-turkey-was-almost-our-national-bird-1732163.php
The authors said their model predicted take-offs with weight restrictions “will increase by 50 to 200% at four major airports” in the US. Oh, really? That could mean increasing from 2 days to between 3 and 6 days. Or, perhaps it means increasing from 20 days to between 30 and 60 days. Since they specified a percentage and NOT actual numbers (at least as far as can be seen in the abstract), it seems they opted for sensationalism. I would have given them more credence if they had reported an avg number of days +/- s.d. and then stated the model result. Of course, I wouldn’t have to guess or infer if I could read the paper.
Why should we take any claims seriously unless we can see the data? I don’t care to leave the analysis to the “experts” who may very well have a conflict of interest in telling me the truth, whatever that is.
It is encouraging that ‘environmental scientists’ are learning about issues such as these. It is disconcerting that they were able to become ‘environmental scientists’ without knowing about them in the first place.
They have all exhibited the naive self-confidence of a sophomore since they starting raising alarms about the ‘climate’. They are now displaying the understanding of a third-year student. Still not ready for graduate-level work, though.
If a computer model said so, it must be true.
This relentless drum-beat of goofy and gauche announcements of global warming impending disasters is pulling down the whole genre of disaster prophecy to the level of self parody.
Once again its the end of the world as we know it and I feel fine.
A few decades ago, I had to delay takeoff from Phoenix Sky Harbor from late afternoon until almost midnight during a spell of 120° F daytime temperatures. [Boeing 737-300]
The problem was not airplane performance because of density altitude, although that is always in the calculation. Takeoff performance is calculated for every take off. “If it is off the chart it is off the menu.”
The reason for the delays, which was later “corrected” was that the performance data charts had not been established to that temperature. The “fix” was to establish performance figures for more extreme temps. The only change to make it “legal” was to correct the data base.
The same thing was a big factor in the Desert Storm and later mideast airlift operations. The idea that any believable global temperature change would seriously impact todays aircraft within their operational lifespan, or that future aircraft will not have better performance than yesterdays’ is worse than “unscientific” it is aeronautically “silly.”
We should, however, encourage overtly ignorant red herrings because the public, even the Gruberesque Stupid segment, can see through it.
The article that launched this thread sounds more like it was written by one of Al Gore’s Facebook “friends” than by a serious scientist.
Here’s what Robert Ballard (discoverer of the Titanic wreck) thinks about models. Go to 7.15:
Interesting video, thanks.
Great video, thank you for posting it.
Well the solution is quite trivial, and was seriously suggested back when SSTs were going to be the commercial planes of the future.
The answer was to simply build a continuous banked oval around the whole airport. Do as many laps as you need to get to take off speed in your desired (headwind) direction. No more crosswind landings either.
You first 🙂
I’d be glad to. I did some of my flight training at an old WW-II era air field that had eight intersecting runways in parallel pairs, forming an octagon pattern. My instructor would take me over there (actually verse vicea) whenever he wanted me to practice crosswind TO&L. Was quite a place with grass growing in every crack of the old concrete strips.
Anyway, on a banked track, going in circles is not a tracking problem. Nascar and Monza demonstrate banked circling.
Of course pilots know about air temperature affecting takeoff. But just how hot would the air have to be in order to prevent a regular commercial airliner from taking off? And would humans be able to survive it?
LonestrM makes a telling point: there are runways in the Middle East, where it gets hot all the time.
I remember a number of years ago when temperatures in Phoenix were consistently above 120F. At that time, the performance tables for most airplanes didn’t go above 120F. Now, most of that has been taken care of by computerized performance software. At high density altitudes now, maximum tire speed is the limiting factor.
A good topic for Burt Rutan, who has an incredibly detailed AGW site, and slipped below the radar years ago. His canard airfoils don’t have good STOL characteristics, and the Mojave Desert isn’t a cool spot.
http://rps3.com/Pages/Burt_Rutan_on_Climate_Change.htm
http://www.burtrutan.com/
I forgot this link with the video of Anthony Watts and Burt Rutan, the one I really wanted to post, 2012, and I’m glad I was wrong about Rutan’s recent AGW-sanity work.
http://www.burtrutan.com/
Who wants to come out and play ?