Here I’m expanding on my earlier words on aircraft Contrails.
Airspace is a busy place. It’s most busy over Europe and the US. Over the oceans there’s more room, although on certain routes, like the North Atlantic, there’s plenty of daily air traffic.
Those who manage the airspace are primarily concerned with ensuring that aircraft collisions do not occur. The impact of mid-air collisions is devastating. There’re few people in aviation who can forget the events of an evening in July 2002. Over Überlingen, Germany[1], 71 people lost their lives at a time when the sky was not busy at all.
Managing the use of airspace is more than collision avoidance. Flying is perpetually concerned with the weather. What’s it doing, how is it changing and is it a hazard? It’s not just the safety of flying that demands up-to-date meteorological information. Knowing about the winds can enable more efficient operations, and that’s less fuel use for a given route.
Large thunderstorms need to be avoided. Regions of the world (example: intertropical convergence zone) make this a dynamic challenge. Manoeuvres may be planned but flight crews must be ready to act based on the information they have, like weather radar.
Turbulence is another phenomenon to be avoided, if possible. This can occur in clear air. It can be difficult to detect. Which explains the unpleasant examples that hit the News now and then[2].
Back in 2010, aviation had a reminder that avoidance encompassed any hazardous airspace. That was when an unpronounceable volcano in Iceland was spewing out ash at high altitudes. Plumes of volcanic ash, if ingested into aircraft engines, can cause major difficulties.
I’ve written these words to emphasise that the avoidance of contrail formation cannot be done as a stand-along consideration. It becomes one factor in a whole mix of factors.
Avoidance of contrail formation is about considering the mechanism that cause them to form. Clearly, the warmer the air is the harder it is for a contrail to form. The more humidity there is in the air, the easier it is for a contrail to form. Outside Air Temperature (OAT) and atmospheric humidity vary at each altitude. That relationship interacts with the aircraft inflight, and the outcome may be different for each aircraft type.
At least one academic study[3] says that adjustments of aircraft altitude of around 2000 ft could have a useful effect on contrail formation. That’s good to know but let’s not forget that Reduced Vertical Separation Minima (RVSM) [4] means a vertical spacing of 1000 ft in busy airspace.
My take on this fascinating subject is that there both a tactical and operational approach that can be practically taken by aviation.
At the tactical level, airlines can factor contrail avoidance into flight planning. Creating an algorithm that will weigh all the relevant flight factors. Improved sources of accurate and timely meteorological data and predictions will be needed.
At the operational level, it’s down to the flight crews to take advantage of environmental conditions as the opportunity arises. Much as dealing with turbulence, that is when safety and operational rules permit. To change altitude when its beneficial, computational help is likely to be needed. Over the ocean, air-ground communications systems may need to be further improved. An altitude change that avoids contrail formation but increases fuel consumption would not be a sustainable solution.
These computational tasks may well be well suited to machine learning. A useful application of artificial intelligence. I can imagine a cockpit weather radar display with a new set of symbology that indicates a low probability contrail formation zone ahead.
[Back in the 1990s, I worked on RVSM when the ARINC organisation was creating international standards. Safely increasing traffic in the North Atlantic region. Additionally, I participated in the certification of Future Air Navigation System (FANS) 1/A for use over the ocean. FANS led to more efficient aircraft operation due to shorter flying times and decreased fuel burn.]
POST: Looks like data crunching is underway Flight plans, but greener: The ICCT and Google’s mission to refine the Travel Impact Model – International Council on Clean Transportation
[1] https://www.bfu-web.de/EN/Publications/FinalReports/2002/Report_02_AX001-1-2_Ueberlingen_Report.pdf?__blob=publicationFile&v=1
[2] https://www.flightglobal.com/safety/turkish-777-rapidly-descended-during-crews-aggressive-response-to-turbulence-encounter/162937.article
[3] https://www.imperial.ac.uk/news/195294/small-altitude-changes-could-contrail-impact/
[4] https://skybrary.aero/articles/reduced-vertical-separation-minima-rvsm
John Vincent 