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Contrails: How tweaking flight plans can help the climate.

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Contrails: How tweaking flight plans can help the climate.

Old 23rd Oct 2021, 10:20
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Contrails: How tweaking flight plans can help the climate.

From The BBC " Contrails: How tweaking flight plans can help the climate." IMHO this looks like a non starter but what do I know.

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Old 23rd Oct 2021, 10:35
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Worthy effort I’m sure, and something worth considering, something must be done etc… but when you read:

“Prof Hayward says the next challenge is for airlines to work out how altitude changes of a "few thousand feet" can be made mid-flight to avoid contrails while also not disrupting passengers' comfort. A pilot would need to spot these in "sufficient time for an aircraft to adapt gracefully", he adds.”

You realise that this is yet another area where some of the researchers, ever willing to comment, have perhaps had little if any exposure to operational flying.

Neve mind upsetting the G&T, I think more of a challenge might be how these “few thousand feet” altitude changes are going to be facilitated for presumably multiple aircraft in busy RVSM airspace…

(BTW and as a FWIW umpteen decades back some Met forecasts included/details the minimum contrail/ “Mintra” levels/altitudes, I guess now there’s the ability to do it much more accurately than in days of old).
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Old 23rd Oct 2021, 10:47
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Personally….I think passenger comfort is overrated.
People do NOT book airline tickets based on smoothness, they only look at cost despite the best efforts at virtue signaling and corporate branding.
No-contrail flying definitely worth looking into.
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Old 23rd Oct 2021, 10:49
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Been reading the annual report of a met agency and how many millions of dollars they have value added to the aviation industry by helping them save tens of millions of litres of fuel by providing them with enough information for choosing favourable flying altitudes. Methinks the good professor should stand back a little and look at the big picture.
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Old 23rd Oct 2021, 10:50
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Lots of routes I fly in Europe e.g UK to Canaries or over Austria/N Italy where there is a lot of traffic there are often high level clouds caused by so many planes making persistent contrails. A way of reducing these would definitely be beneficial from a climate perspective.
Operational challenges: given most flights I fly we go as high as possible for efficiency generally. Flying higher isn't normally an option, flying lower will generally increase fuel burn. Which may be of more climate benefit if it prevents enduring contrails despite higher CO2.
But then you'd either need to carry more fuel all the time = higher fuel burn or just on some flights when it's possible.
Looking at a rear facing camera and adjusting sounds nice but isn't too realistic.
Disclaimer yes I know that relative headwind/tailwind can sometimes exceed benefit of climbing.
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Old 23rd Oct 2021, 11:01
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Forgive an ignorant question from humble SLF, but isn't it normal to change altitude for optimum performance during cruise? For example, 4,000ft 'step climb' as fuel is used up? Pax never notice.
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Old 23rd Oct 2021, 11:15
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Yes, it's normal. You tend to go up in 2,000ft increments. However, winds change aloft and sometimes your flight plan may well ask you to drop down 2,000ft to take advantage of a jetstream for example. All I know is always looking to go higher works mostly, but it does pay to look at the upper winds first. Sometimes you are given lower levels to avoid slots and restrictions on a part of the route, which in reality are not needed. other times it's for weather and helps a lot. Just being aware and paying attention can make the difference. Not that managers will ever credit you for doing it..
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Old 23rd Oct 2021, 11:17
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I rarely take a news story at face value; particularly from the BBC. This is probably a tentative opening shot in a campaign to severely restrict aviation in line with the zero net carbon thing.
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Old 23rd Oct 2021, 11:58
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Yes it is, for the reasons RVF750 mentioned…on a long haul flight you may well step up (rarely down but it happens) several times during the cruise and as you say the pax hardly ever notice….

I hope the Prof on the article was making a slightly light hearted comment….from a practical POV it’s the handling of all traffic approaching a block of contrail prone airspace all wanting to step up/down to avoid that probably much much more of a real world problem.
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Old 23rd Oct 2021, 12:17
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Most research starts at the level of "Is there an effect here?", not "What are the full implications of this effect and how shall we best exploit it?"

I don't think Wilbur and Orville envisioned moving 500 people at a time halfway around the world at 38,000 feet when they worked out that they could fly a few hundred feet just above some sand dunes in North Carolina.

The press, of course, like to spruik the most spectacular possible outcome when reporting really basic research. Outside of aviation, hydroxychloroquine in a petri dish comes to mind.
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Old 23rd Oct 2021, 13:07
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Soo, we should burn more fuel in order to not produce contrails? Seems legit....
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Old 23rd Oct 2021, 15:02
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Can you imagine the number of TCAS RA having this big mass of a/c changing level every second ? It remind me the circular runway solution …
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Old 23rd Oct 2021, 15:08
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Life, including aviation, is full of trade-offs.
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Old 23rd Oct 2021, 16:36
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The ICA thanks you for your service.
Dimmer skies for a brighter future. 😁
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Old 23rd Oct 2021, 17:08
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So there are already processes in place that safely allow a/c to fly at their 'optimal' altitude. If the effect can be predicted (i.e. what's the best altitude to reduce contrails), is it not just a case of using those processes but to now fly at what is the new 'optimal' altitude - having taken account of the trade offs...
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Old 23rd Oct 2021, 17:52
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You could save a lot of pollution and fuel by not flying fruit across the globe.
Do we really need Sharon Fruit, Cumquots, Kiwi fruit and the like (In Farnborough) flown from places like New Zealand (or whereever they come from).
Lets go back to home grown seasonal produce.
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Old 23rd Oct 2021, 18:51
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That’s great if you are the only aircraft in a block of sky…you get your optimum level.

What we already know is that in the real world with multiple flights operating RVSM (1000’ vertical separation) combined with quite possibly tight horizontal separation it’s often not possible for everybody to be at their optimum level because somebody adjacent will have already got it…now at worse you might only be a few thousand feet off your optimum so it’s hopefully not a major problem…

However now chuck in this new idea that involves avoiding the trail levels - which might (and this is one for a met person) be a block of airspace thousands of feet thick- and it’s IMHO going to get much much more difficult to manage.

Who goes above the block? who goes below? …What happens in a few hundred or thousand miles when the contrail levels change and everybody wants or needs to shift up or down to avoid? In busy areas (e.g. States/Europe/North Atlantic Tracks once they really busy again) is there actually enough volume available to sanitise an entire block of airspace to avoid contrails and also still have the required separation between traffic?

Not saying it can’t be done but at a first glance there’s probably a bit more to it than simply saying just avoid certain levels and then coming up with procedures to avoid uncomfortable climbs and descents….

Last edited by wiggy; 23rd Oct 2021 at 19:04.
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Old 24th Oct 2021, 02:59
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Did 'Concorde' leave a contrail at FL650 or whatever?

Or 'The Sled' at FL800 (?)

At least they would be the 'only' aircraft 'up there'.... apart from other military types of course...
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Old 24th Oct 2021, 03:38
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I understand that contrails can sometimes form into wide cloud bands, I’ve seen it dozens of times over my career but the same amount of water vapor is still produced by any aircraft whether or not it leaves a contrail behind it.

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Old 24th Oct 2021, 06:55
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"Contrail cirrus" is the term used to refer to that phenomenon.
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