Bjorn’s Corner: Sustainable Air Transport. Part 3. Low hanging fruit.

By Bjorn Fehrm

January 21, 2021, ©. Leeham News: Whatever is done in terms of new Sustainable technology for the aircraft, will have a limited influence on the amount of Greenhouse gases that Air Transport emits before 2050.

We will only get the new aircraft types into operation about 15 years before the deadline and with, on average, 100 to 200 aircraft per year. That’s 1,500 to 3,000 of the total of 25,000 aircraft that operate in our skies daily. It will not reduce our Greenhouse gas emissions significantly.

Sustainable Aviation Fuel, SAF, will help, but only when it’s available in quantity and to a reasonable cost. We can do things that have a much faster effect, and that’s how we manage our flights.

Figure 1. The US flights as seen on Flightradar24 yesterday. Source: Flightradar24.

A smoother flow of the 100,000 flights a day

When the pandemic subsides, we will be back to about 25,000 airliners flying around 100,000 flights a day. None of these flights fly optimized routes. Investigations have shown that at least 10% of the emissions from these flights could be avoided if we could manage the flights better.

I talked to a Chief Pilot for one of our leading European airlines at the Airbus Summit in Toulouse in September. He told me he switched off the datalink-based CPDLC communication when he came to land at the London airports.

The chaos in terms of reroutes, speed adjustments, and holdings to cater for the typical London area congestion just couldn’t be managed other than by constant talking between Traffic Controllers and Pilots.

It’s the same in many areas of our air traffic system. Reroutes, delay tracks, and holdings are the tools Air Traffic Control (ATC) must use to separate bunched-up arrivals so that the typical 2 minutes spacing between landings for a runway is achieved.

There are fixes to the chaos

For decades, work has been going on in the ATC area to improve this, such as NextGen in the US and CESAR in the EU. But progress is slow. The changes require new hardware, new airflow routines, retraining of air traffic controllers, and adaptations of operational procedures and equipment by the airlines.

I work as a Mentor of sustainability upstarts at the Sustainable Aero Lab in Hamburg. There I came to Mentor a really practical and intelligent approach to the above.

A Captain in one of the world’s largest airlines grew tired of all the delays and thought out a system that can fix a lot of the mess without changes to ATC, the aircraft, or airline procedures. It’s a cloud-based system that makes sure airliners fly to their destinations such that they arrive in the time grid ATC needs to guarantee a direct route for landing.

There are enough airline trials done with the system in different countries to prove it works, and new countries now queue up to trial it. We work hard to get this clever approach sufficient funding and Worldwide traction so it can be the tool we need to change the amount of fuel consumed at destinations and, by it, CO2 emissions.

The approach doesn’t replace any of the other measures that are in the works; it complements these. Its key feature is that it doesn’t require any new hardware, software, or procedures at airports, ATC, or aircraft. CO2 gains of over 20% in the landing phase have been proven in over 600 test flights on two continents to date.

The lowest hanging fruit

Changes to how we fly our existing aircraft in our current air traffic control system are the only immediate gains we can make regarding emissions from aircraft. All other changes take a longer time.

New generations of existing aircraft technology, such as improved engines, come in 10 years intervals. New propulsion techniques such as hybrids or hydrogen-based systems take another five to ten years to get it to smaller aircraft, representing a tiny bit of our traffic.

Until it migrates to the mainstream single aisles, we talk 15 years or more. And then, we only replace a maximum of 1,000 aircraft per year (at best).

So before we look at new aircraft technologies and their problems, our top priority measure shall be a better flow for the existing aircraft we fly.

45 Comments on “Bjorn’s Corner: Sustainable Air Transport. Part 3. Low hanging fruit.

  1. One would assume ATC like Eurocontrol would have the whole route 4D decided and sent digitally to the aircraft to follow and if no disruptions due to weather, emergency traffic, military etc. +99% would follow these preprogrammed tracks in the sky avoiding any altitude overshoots and do TOGA if unstable approach. The pilot can of cause send a message that problems arises and break out of the given route to selected alternate preprogrammed route and then be given a new 4D track to land.

    • Tere is a lot happening in that domain.
      direct p2p routes.
      after top of climb “glide path”
      micromanagement for early queuing

  2. Aviation in many ways is not a leader. We may find self driving cars on roads before the ATC problem is solved.

    As far as I can see each aircrafts position and velocity must be precisely tracked “centrally” in 4 dimensions with GPS/Gallileo/GLONAS fused with radar transponder returns and telemetry from inertial navigation system returned via satellite when available. These would return aircraft serial numbers and other data such as barometric. Some kind of distributed cloud and block chain technology will be needed to guarantee robustness and avoid political interference.

    Guidance commands must be injected into the autopilot to ensure the aircraft route is completely deconflicted of possible collisions and lines up with the runway and lands at exactly the correct time. Obviously a flight plan must be filed electronically and also accepted. Obviously we must have no more hold patterns (except in the case of emergency)

    The technology (such as communications satellites) is becoming available.

    It is more akin to missile guidance than air traffic control.

    Elon Musk once stated “one day it will be illegal to drive on a public road” by which he meant roads with self driving cars would loose all of the gains if there were manual drivers still on them. It may be the same in trafficked airspace.

    I think the land area taken up by airports will themselves come into question one day.

    • Yes, I think those not flying fully automatic with ATC selecting and transmitting 4D keypoints for each aircraft in the future will be banned from the most economical routes and the smart missile analogue is vaild. Aircrafts will be “slow SM-6 missiles with self loading cargo” and maybe use special fast glidepaths from top of climb to dedicated runways not running ILS systems but something more advanced allowing faster landings and thus increased landing frequencies as you clear the runways faster as well. It will take time before each EU country will let control go to an AI compter in Brussells…

      • The kind of system I describe will I suspect first be implemented for delivery drone and eVTOL flights in cities perhaps in corridors from which manually controlled aircraft are banned unless specially equipped for worthy purposes such as first respond Medivac. The slow response and update time for man in the loop air traffic control and piloting simply are unable to respond fast enough to provide a safe system that can be tightly optimised for 300kmh eVTOL and drones.

        In addition it’s just way too expensive having highly trained and responsible pilots and air traffic controllers. We can maybe afford such personnel for 244 seat A321neo but it makes smaller aircraft increasingly unaffordable.

        A 10% reduction in fuel burn likely also broadly equates to a 10% increase in airport slots and a 10% decrease in transit time and a 10% increase in capacity for the airliner.

        This is the only way to make aviation affordable.

        • You can have 4D routes programmed into the FMS that also reads GPS time signals. Then ATC just need to select a suitable proprogammed 4D track and indicate start time. Boeing just invested into Pittsburgh-based Near Earth Autonomy doing similar stuff. Still ATC will charge alot to send those route approvals as they will be the only ones approved to do it.
          Historically you like to have the militar taking the early cost of development.

      • Just looking at what would be required for a fully automated Air Traffic Control System with fully autonomous aircraft.

        I’m assuming 4 levels of redundancy.

        1 Aircraft position and velocity vectors measured by GPS/Galileo/GLOANAS. if there is no GPS or radar available INS, Star tracker(should be cheap given today electrooptic on a chip) and some sort of ground based radio system (e.g. old VOR/DME LORAN)

        2 Above position and velocity vector data transmitted via satellite to an air traffic control system.
        3 Above position and velocity data also transmitted directly to ground receivers when in range.
        3 Above data also broadcast directly to other aircraft in the vicinity. This would require something similar to the DRSC “Dedicated Short-Range Communications” IEEE 802.11p for WAVE (Wireless Access in Vehicular Environments) that is designed to allow vehicle to vehicle communications (sort of WiFi). This means if the aircraft loose satellite communications they can revert to algorithms in a local cooperative environment. Threading and mesh networking technology would allow the data to be relayed from aircraft to aircraft back to ground stations.

        4 The position should also be measured by ground-based 3D tracking radar (primary and secondary) which fuses with the GPS data (when in range).
        5 Heading data is injected directly to the autopilot is transmitted backed to the aircraft via satellite, direct ground link and direct links ultimately to the point of landing.
        (Similar to the way F1102/F106 were controlled in the SAGE “Semi-Automatic Ground Environment” where the time critical task was intercepting nuclear bombers and manually controlled intercepts would have been too slow)

        Meteorological and barometric data, plus weather radar would be transmitted by satellite to allow routing around bad weather.

        Most of the above systems are already in existence such as the new IMARSAT satellites.

        What is missing is the aircraft to aircraft network and the software.

        Hence there would be 3-4 independent communications links from aircraft to ground and direct to other aircraft. There would also be as many positioning systems as possible (GPS, Radar, ground based radio etc).

        The key to getting there will be to implement the sub systems piece by piece with communications ability so that the system can be ‘switched on’ when needed.

    • Too funny…. did they try it out in a wind tunnel, or was a computer simulation ?

      • They did it in real life with real wide body aircraft. They’d developed LIDAR that measures the wake position and its velocity vectors. They then fly in that wake. They also computed the wake position by simulation, that can be done, but they can actually measure it’s precise position with LIDAR so that they can ‘surf’ the wake.

        • This is marketing fluff designed to help Airbus with its brand image but will never be used in practice. I wish manufacturers and airlines would stop spending 100% of their time on greenwashing.

          • Well, this is AB spending money on R&D while BA spends money on servicing its crippling debt burden.

          • The airlines and aviation industry have no choice since the anti aviation environmental ‘attackers’ for the most part have abandoned reason and are quite willing to use fear mongering and emotionally based scare tactics. How do you fight that with reason? You can’t. Anyway the SAF demo flights of today will be real SAF flights in a few years time. In a really advanced ATC system formation flying may be relatively easy to organise and achieve.

    • The USAF tried this ten years ago on a round trip test between California and Hawaii. They reported double digit fuel savings.

      • Indeed they did and I think Boeing was involved. I think the difference is the Airbus LIDAR wake sensor with those USAF flights based around a calculated position. It still worked. It is a natural for an Airforce to fly in formation.

      • what kind of proximity?
        like in mil formation flying?
        IMU Airbus tested this with more “civil” separation
        and instrument cueing.

        Uptake will depend on how to share the savings.

  3. On the subject of routing efficiency, airlines could also do more to remove inefficient routes from their ticketing. It won’t happen, of course, because it means lost revenue — and most passengers don’t check these things — but it certainly qualifies as low-hanging fruit. For example:
    – I know someone who flew a few years ago from Atlanta (GA) to Phoenix (AZ). This was not done using an airline with a hub in Atlanta (e.g. Delta) or Phoenix (e.g. Southwest) but using United via Denver. This goes unnecessarily north and then south again.
    – I also know someone who flew from Bangkok to LA using Emirates! That means 8 hours to Dubai, followed by 17 hours to LA. If he had flown using Delta (direct) or using an intelligent stopover like Tokyo, he could have done the journey in 16-18 hours.

    Intelligent ticketing doesn’t just save time — it saves a lot of fuel / emissions.

    • A colleague I was travelling with on a work trip organised tickets to fly Qantas from Sydney to London thence to Moscow with BA and thence to Siberia with S7. His motivation was to increase his frequent flyer points with Qantas.

      I decoupled from this unnecessarily long flight and travelled Sydney-Dubai-Moscow-Yakutsk. What should have been a flight straight north of of Sydney for 10,000km became a 25,000km dog leg for him and maybe 18,000 for me. It proved impossible to get to Siberia via China or Japan because there were such few flights.

      There is a lot that can be done regarding political borders as well. No airline wants to hub through semi dysfunctional states with dysfunctional airports that would otherwise be optimal.

      • Google flights suggest the lowest CO2 for that sort of destination means going to Phuket- Vladivostok-Yakutsk. Its almost a direct route.
        The advantage and disadvantage its mostly A320 single aisle and some longish layovers.

        • Yes, our Russian brothers, presumably the ones suffering SADS in a Siberian winter especially like Thailand and I’ve noticed Bali during those winters so these would be mainly holiday type airlines. It was 6 years ago, Internet booking was much harder and I was booking flights myself at the last minute. Idiot ‘points boy’ colleague didn’t leave me time.

          An important point. Major airlines and major agencies route through the hubs and airlines profitable for them with carriers they have relationships with. They dominate the internet booking space.

          • Normally a non stop to say Hong Kong , Seoul or Shanghai and then direct to Vladivostok and then Yakutsk which is same general region of Russia

          • That would be a very valuable additional parameter to the google search results

  4. Agreed on the tech aspects of low hanging fruit.

    The issue is the highly public visible image of Aviation. The Press runs with it and the public sees it as a simple issue.

    The Optics are daunting and the public is short sighted and does not nor will they get it.

    It would take a huge PR campaign and a lot of questionable if that would even work.

  5. The key issue to adoption of such a system is being able to understand the stability under perturbations. Highly optimized systems are subject to collapse should there be large disruptions. The purpose of optimization is to take advantage of unused capacity in the system, however, this unused capacity can also be considered as resiliency or a buffer. One can foresee that point-to-point could create a system where slight disruptions, like for example, a go-around or rain squall, creates a bow wave for arriving flights which would not only decrease the fuel savings but also create new safety concerns.

    • > Highly optimized systems are subject to collapse should there be large disruptions. The purpose of optimization is to take advantage of unused capacity in the system, however, this unused capacity can also be considered as resiliency or a buffer.. <

      As we are presently experiencing- for one example- in our long, complex, and fragile
      Supply Chains.

      Thank you for the above important comment.

      • Unfortunately, current unused capacity can’t be used as a buffer since the system is unable to manage it. We wind up with lower capacity than we might otherwise have and are still vulnerable to large scale disruptions.

    • There is a branch of applied mathematics called ‘queuing theory’ which describes the probability of the number of cars waiting at lights and the flow of data traffic. The human condition made a lot ore sense when I was forced to study it in the telecommunications side of my EE degree course.

      I think the software folks have a very good understanding on how to handle perturbations and so forth. The simplest way is simply to build in spare slots to buffer these perturbations (say 1 in 10) and then allow a compression of the slots (say from 60 seconds to 55 seconds with 20seconds in extremes (wake turbulence allowing)). There is simply no way around building in reserves for perturbations such as technical faults, flight delays, bomb threats, storms etc. Ultimately secondary airports will still be needed. Man in the loop ATC and pilots would seem to require even more reserves.

      • Any buffer potential the sane minded engineer introduces will be homesteaded by the paper pushers and _used heavily_ .
        If it breaks the engineers are berated 🙂

        • As we saw with the US FCC unilateral decision to sell of the 3.7GHz-3.98GHz spectrum in only 2 years.

  6. 5 -10 Years ago Ford took a Press beating for its big Excursion.

    It had nothing to do with reality, it was nothing more than a big Van, but as it was labeled an SUV (The S is a PR spin that has been added, they actually are UV aka Utility Vehicles)

    No one was going to buy it unless they needed the large number of seats and if it was not there they would buy the Chevy Suburban or a big Van.

    So the optics can be weird and distorted by the press.

    • This kind of statement doesn’t belong in technical comments section about air traffic control improvements designed to reduce harmful emissions. All humans are hypocrites and westerners are no worse. We know from evolutionary psychology that its built into our natures as a hierarchical social animal. I suggest a reading of Johnathan Haidt’s “Righteous Mind”. We might call one type of hypocrisy (the word means acting) ‘virtue signalling’ for purposes of status seeking. Non other then a teacher of mankind, Jesus, warned of it cautioning people to express their goodness sincerely and inwardly rather than for public display. You might consider that you have conducted some hypocrisy and virtue signalling yourself. By throwing other Westerners under the bus but in a backhand way saying you are better than they because you recognise it. I’m sure when you said “We” you didn’t really mean you as part of we.

      • You can make your point without bringing “Jesus” into it: it’s bad enough when people bring politics into the discussions here, but all hope will be lost if Abrahamic religion gets dragged into the forum 😉

        Why not instead allude to neutral figures such as Confucius, Socrates or Erasmus?

        • I referred to Jesus as a teacher I did not invoke religion. I am an atheist. Warning of the human foible of hypocrisy and for public consumption displays of virtue and it’s pitfall to one’s inner character in particular is a notable one of jesus teachings that’s had a strong but sadly waning influence. Others religious or philosophical leaders may have made such points as well but it’s certainly not a billionaire stoic like Seneca nor Socrates. Socrates was virtuous and ethical but not really a teacher of character.

  7. Dude, William, Bryce, et al, let’s get back on topic and stay there. Otherwise I will close comments.


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