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Thursday, November 27, 2014

Various views flying about at WUWT

Sou | 8:51 PM Go to the first of 4 comments. Add a comment


There's not a lot happening in the deniosphere today as far as I can see. Anthony Watts posted another of his "claim" headlines, this time with slight variation (archived here). His headline read "Model claim: airplanes of the future won’t be able to take off at some airports due to global warming". His headline implies some airports would have to close, which isn't what the paper said.

The copy and paste this time was the abstract from a paper in the AMS journal, Weather, Climate and Society, about how the increase in surface temperatures is affecting aircraft. (For some reason, Anthony Watts said it was published in BAMS, but it wasn't.) The abstract, which was all Anthony published, states in part:

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.
It goes on to discuss how it will be a particular problem in the future for airports having short runways and no room to extend them.




Getting off the ground will be more difficult


Here is what the problem is according to the paper (my paras):
As air warms at constant pressure it becomes less dense, and an airplane wing traveling through this thinner air will produce less lift at a given speed than in cooler, thicker air. As a result, on warm summer days commercial airplanes have higher takeoff speeds (Anderson 1999).
Barometric pressure variations are used in day-to-day flight planning, but since weather-related pressure changes are usually less than 30 hPa at all airports worldwide this is a much smaller factor than temperature and is not considered here; all performance data assumes a standard pressure of 1013 hPa.
For each airport and aircraft type, there is a temperature threshold above which the airplane’s minimum flying speed at its maximum takeoff weight is too high to reach on the available runway, and the airplane must be weight restricted. Airlines respond by removing either passengers or cargo to decrease the aircraft’s weight and thus lower its takeoff speed.
Here we investigate how the number of days per summer (May-September) on which a Boeing 737-800 must be weight restricted may change during the 21st century as a result of climate change.

The researchers looked at different aircraft at different locations, and the likely constraints, such as whether planes need a full load of fuel or not and whether or not runways can be extended.  The four airports they chose:
...may be particularly susceptible to increasing temperatures: Phoenix Sky Harbor International Airport (PHX), Denver International Airport (DEN), New York’s LaGuardia Airport (LGA), and Washington, DC’s Reagan National Airport (DCA). PHX was chosen due to its frequent extremely high summer temperatures, DEN due to its relatively high elevation, and LGA and DCA due to their short runways, limited space for expansion, and high traffic loads.

The researchers said weight restriction will be an important factor, and suggested that the airlines might need to use different aircraft in summer. They can also think about making sure that heavily loaded aircraft aren't scheduled to take off in the hottest part of the day. Neither of which problems would be insurmountable, I'd have thought. Extending runways isn't possible at some airports - or would be very difficult. So they'll have to find a workaround for that.

What the authors came up with was the number of weight-restricted days at the different airports over time, as temperatures rise. The paper has a bunch of charts. In the abstract, it says that
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).

There was quite a bit more, for example:
The aircraft analyzed here, the 737-800, is still in production and individual airframes will likely be in operation for several decades. The effects of climate change on weight restriction are already detectable and are projected to become increasingly significant within the lifetime of these aircraft. All other commercial aircraft will also experience the effect of increasing temperatures to varying degrees, making the results presented here highly relevant for current and future airline operations. Changes in technology will no doubt revolutionize the aviation industry in the next 50 years. Carbon fiber structures will make aircraft lighter and new engines will produce more thrust with less fuel. However, these changes do not inherently result in better takeoff performance – aircraft manufacturers may need to prioritize this in the future.

The paper also mentioned other climatic influences, such as potential changes in storm frequency or intensity, sea level rise and its impact on low lying airports and other things.

Keep all that the authors wrote in mind when you read what some of the WUWT-ers had to say. Fake sceptics often take the line that researchers are stupid and fake sceptics are really, really clever and know it all.


From the WUWT comments


Quite a few people at WUWT said how they'd observed the effect of hot weather, either flying themselves or as passengers. Others were poo-pooing the research and the facts of the matter. Some were assuming that global warming is happening but arguing that aircraft engineers will solve the problem by changing the design of aeroplanes. They didn't say why that hasn't happened yet or whether it's happened yet. The paper was looking out to 2050-2070. That's not all that far away when you think about the time taken to design, build and get a new design into operation with most airlines. Especially when you think how long companies hang onto aeroplanes for.

John Coleman was first to comment, proclaiming the research "silly". I guess he doesn't fly much. Or maybe he's like Pavlov's dogs and this is an automatic response to Anthony's "claim" headline. For sure, like most fake skeptics at WUWT, he didn't click through to the article or he would have seen it wasn't published in the Bulletin.
November 26, 2014 at 7:37 am
Why did I allow my membership in the AMS to expire? The political silliness had taken total control of my professional society. Publishing this fantasy in the Bulletin is a good example.

tgmccoy, who says he works as a co-pilot, seems to think that the researchers - who referred to the effect being observed since 1980, were treating the issue "like something new". Just as well he's not still flying is all I can say.
November 26, 2014 at 11:58 am
hifast- Agreed- back in the 90’s I was working as a Co- Pilot on a DC-7 airtanker out of ABQ,SLC etc, We ‘d depart ABQ south or west bound usually, and due to the high, hot, conditions and the fact that the R-3350 radials were ah, sensitive to temp extremes i,e, too hot, too cold, killed them, you did a METO climb very rarely past 500 agl and did a cruise climb at whatever would keep the temps down.
We’d have conversations with departure like this: “Ah do you know your mode C shows you BELOW field elevation?”-as we would dip into the Rio Grande Canyon to cool off and raise the takeoff flaps….
The Salt river drainage was handy at Phoenix too …
Now the next gen is coming on for Airtankers, RJ85’s BE146’s,MD87’s DC10’s
etc. Single engine airtankers or SEATS also..
Models are just that-nothing based on reality. the real world blows on past the model…What I am amazed at is density altitude issues on aircraft performance is treated like something new…

Crispin in Waterloo thinks all the airports in Sahelian countries have runways that are too short. He says:
November 26, 2014 at 4:44 pm
I guess the weight restrictions from warm temperatures means we will never be able to fly ti the Sahelian countries, of the Gobi desert in summer. Shame. I was looking forward to the introduction of powered flight to Africa.
I will have to communicate this emerging danger to the Ukrainian pilots in the DRC who routinely take off with 150% overload from the Lubumbashi airport delivering equipment to the mining companies in the triangle.

Curious George is a member of the scientific illiterati and says:
November 26, 2014 at 8:30 am
Not just the AMS. When I see words “Center for Climate Systems Research”, I expect drivel. I have promoted the Columbia University to a Columbia High – no, Columbia Middle.

GeneDoc is a shuffler with a shaking head who doesn't think airline manufacturer's and airports should be bothered with such details to help them plan for higher surface temperature 35 years from now:
November 26, 2014 at 10:31 am
Amen! What complete drivel. What will we be flying in 35-55 years? What were we flying 55 years ago? In 1960 the 707 and DC8 were king and queen with their huge capacities of 250,000 lbs maximum takeoff weight powered by four relatively scrawny 15,000 lbs of thrust turbojet engines. Compare to GE and RR motors of today with upwards of 90,000 lbs of thrust lifting takeoff weights over 1 million pounds.
I do remember a seemingly endless takeoff roll in a stretched United DC-8 loaded for a trip to Boston at the old Denver airport in the early 1980s on a hot summer day–we used all of that runway! Density altitude is of course a real consideration.
Oh, and aren’t the models (and the observed warming) more about higher low temperatures than higher high temps?
Shuffles off, muttering and shaking head. 

There are a lot of aeroplanes in service today that were made twenty or thirty years ago. Probably even some that were built 35 years ago. In any case, it's already getting hotter and the increased heat has had a noticeable effect since the 1980s, according to the paper.


Jbird is another one who hasn't twigged to the need for longer runways in hot conditions:
November 26, 2014 at 7:47 am
Am I the only person who thinks this is utter bull sh*t? How do planes function at the equator where it is hot all the time? How did the Japanese and Americans ever manage to fight an air war in the Pacific islands during World War II? You just work around temperature, air density, and altitude restrictions, and if there is an economic effect, it is probably very little. If it costs more, how is that any different from what carbon taxes would add to the cost?

There were a lot more people swearing black and blue that the research must be wrong because they've seen planes taking off on hot days.

There were a few people who understood what the researchers were on about, too. Which is a surprise given the woeful articles seen at WUWT recently. Anthony Watts doesn't have to always pander to the ignorant bigots. There is the odd person with a brain who reads his blog, he'll be surprised to learn.  M Courtney for example asked:
November 26, 2014 at 7:50 am
How many flights worldwide are delayed today due this phenomenon?
The physics seems logical. But are we so close that it will become a real problem?
Some days are quite hot in some places, even now.

Robert has his thinking cap on, too, and says:
November 26, 2014 at 8:00 am
I would think a secure and inexpensive source of quality fossil fuels to actually run the jets would be more of a concern in 2070. Anybody ever land or takeoff from Lima Peru?


Several people rushed to the aid of patrick healy, who asked:
November 26, 2014 at 8:06 am
Not being a scientist, can some one explain to me what exactly is 200% ?
When I learned basic maths at primary school percentages were expressed in one hundreds.
I hope these climate “scientists” are not designing aircraft. 

MarkW got a bit over-enthusiastic in his science denial, and talked about oceans melting:
November 26, 2014 at 8:22 am
Of course if the oceans started to melt as fast as the models claim they should, then the height above sea level for all of these airports will be reduced which will result in the air at those airports getting thicker.

He recovered quickly:
November 26, 2014 at 8:23 am
Oops, I meant glaciers melting, causing the oceans to rise.
My bad. 

Lowell Wickman will use any excuse to "doubt Global Warming" and says the scientists "assume", though they don't:
November 26, 2014 at 8:30 am
Its articles like this that cause me to doubt Global Warming. This is a pointless study to booster the case for global warming solutions. If they exaggerate in this article, how many other areas are they exaggerating? They assume that the Engineers at Boeing will do nothing to accommodate lower atmospheric densities. If there is warming airplanes will be redesigned to accommodate the warming and runways will be lengthened. If this study came from Boeing or Airbus it would carry some weight.

There were a few who took it as read that the world is going to get hotter, and they came up with all some solutions, including building longer runways - just as the researchers pointed out. What this suggests though, is that if deniers put their brains to work they'll come up with ideas for adaptive measures even when most of the time they reject the fact that the world is warming. Which is a hopeful sign in some ways. more soylent green! wrote:
November 26, 2014 at 10:11 am
We seem to do OK with the altitude and temperatures at the Las Vegas airport (McCarran International). The solution to this imaginary problem is simple — build a longer runway. Also, reduce the take-off weight of the flight. There are many other possible solutions. Perhaps in this imaginary future aviation technology doesn’t advance.

David L. Hagen decided to restrict passengers and weight, or stop mid-afternoon take-offs, which won't be so easy at busy airports:
November 26, 2014 at 10:33 am
Lesson – we have amazing adaptability. Simple solutions:
1) Weigh ALL passengers and luggage and adjust as necessary – as done since DC3 days.
2) Reschedule flights to avoid the 1-3 PM and depart during cooler times of day. 

Mike Singleton is all mixed up. He agrees that density altitude has always been a consideration but thinks that a study relating to the subject is a waste for some weird reason.  It's like saying that smoking is a problem but let's not look for a solution.
November 26, 2014 at 11:09 am
Which idiot approved the funding for this garbage?
The whole CAGW movement are starting to reveal more and more the fiscally and socially irresponsible idiots that they are. I was also a private pilot and as stated by experienced commercial jockeys above weight calculations for density altitude have always been and always will be a part of aviation.
Desperation me thinks. 


Coffel, E. and Horton, R "Climate change and the impact of extreme temperatures on aviation."  Weather, Climate, and Society 2014 ; e-View doi: http://dx.doi.org/10.1175/WCAS-D-14-00026.1

4 comments :

  1. MCourtney (who also denies science on The Guardian climate site) breathes the same toxic air as that desperately unattractive specimen, dbstealey, yet Courtney is unfailingly and insanely civil.

    At first I thought it might have been an act but it didn't take too long to realise that Courtney is governed by a ridiculously resilient ridge of decency.

    ReplyDelete
    Replies
    1. And one exception to the rule of "like father like son". (His dad shouts a lot and is very bossy.)

      Delete
  2. Hey I learned something today! Obvious in retrospect, but I'd never realized temperature affected planes' lift.

    Lighter airframes or stronger engines will mitigate the issue, but engineers could instead spend their effort improving safety, reliability, or costs.

    ReplyDelete
  3. "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."

    This is a situation that those of us who have worked with aircraft from aircraft carriers have long appreciated. An aircraft and a particular weight, fuel and weapon load, can be shot of using a catapult because the carrier is at, near, sea level even in the tropics. The same aircraft may be too heavy to take off from a runway especially at an elevated altitude because of the low air density. A longer runway will not help because the limit is in the tyres. Long before the aircraft reaches V1 the tyres have burst through a combination of heat build up and rotational speed.

    This was one factor consider in the case of the Air France Concorde crash - a possible overload and also a longer than normal taxi to a more distant runway, where heat builds in tyres, and that she had a tail wind on take off.

    ReplyDelete

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