Even if airlines carry out ISSR avoidance deviations whilst maintaining planned Cost Index (ie planned cruise speed) for the flight, the fuel penalty for the flight in question might be anywhere between zero and a couple of percent. That is for the specific flight in question and the outcome will vary depending on the wind field across different flight levels.
If the number of flights needing to deviate for ISSRs is only, say, 5% then the fuel penalty averaged across the entire airline’s operation will be one twentieth of that amount. Perhaps a total of 0.1% of total fuel burn?
Going further, if aircraft carrying out ISSR avoidance reduce their Cost Index (ie cruise speed), they will trade reduced fuel burn for extended flight time. In many cases this will allow ISSR deviations to be carried out for ZERO fuel penalty, especially on longhaul flights.
This is no different to the way that pilots deal with flying “off level” eg due to turbulence or other aircraft occupying their flight planned cruise level.
How do I know this?
Retired airline Captain for a large international airline, with aeronautical engineering background.
People need to stop talking about “fuel penalties incurred by ISSR avoidance” because such fuel penalties are negligible… indeed, with a slight tweak to operating philosophy, the “fuel penalty” could be ZERO.
Talk of fictitious multi-percentage “fuel penalties” is killing the chance of live contrail mitigation ops being implemented at scale.
This is a great perspective with a really insightful take on the fuel-burn debate. Essentially, any avoidance flight would still operate within the parameters of additional fuel burn set aside for any ordinary flight. It completely negates the notion of fuel burn being an inhibiting factor for contrail avoidance. Good stuff.
I may just use this in a future post if you don't mind.
Fire away! We are just about to reach an inflection point. The UK Government is about to announce the next phase of the Jet Zero Task Force programme and it appears they are NOT going to continue with the contrail mitigation aspect of this critical body. This is nothing short of a scandal because it will cede the UK’s world-leading position on contrail mitigation to other nations. As explained, the UK is uniquely placed to run at-scale contrail mitigation trials on the North Atlantic because NATS controls the eastern half of the airspace (NavCanada runs the other half and they are far more engaged with this idea). Airlines, academics, NGOs, pilots and ATCOs are keen to do this, but the UK Govt has decided not to bother?!?! Outrageous!
Definitely within the aviation community - manufacturers, airlines, academics, service providers. What we need is significant weight being thrown behind this at regulatory level, and there are worrying signs that the resource to do this properly (ie a permanent regulatory oversight / coordination body) is not going to be made available.
Let’s shoot the elephant in the room.
There is NO multi-percent fuel penalty.
Even if airlines carry out ISSR avoidance deviations whilst maintaining planned Cost Index (ie planned cruise speed) for the flight, the fuel penalty for the flight in question might be anywhere between zero and a couple of percent. That is for the specific flight in question and the outcome will vary depending on the wind field across different flight levels.
If the number of flights needing to deviate for ISSRs is only, say, 5% then the fuel penalty averaged across the entire airline’s operation will be one twentieth of that amount. Perhaps a total of 0.1% of total fuel burn?
Going further, if aircraft carrying out ISSR avoidance reduce their Cost Index (ie cruise speed), they will trade reduced fuel burn for extended flight time. In many cases this will allow ISSR deviations to be carried out for ZERO fuel penalty, especially on longhaul flights.
This is no different to the way that pilots deal with flying “off level” eg due to turbulence or other aircraft occupying their flight planned cruise level.
How do I know this?
Retired airline Captain for a large international airline, with aeronautical engineering background.
People need to stop talking about “fuel penalties incurred by ISSR avoidance” because such fuel penalties are negligible… indeed, with a slight tweak to operating philosophy, the “fuel penalty” could be ZERO.
Talk of fictitious multi-percentage “fuel penalties” is killing the chance of live contrail mitigation ops being implemented at scale.
Consider the elephant shot!
This is a great perspective with a really insightful take on the fuel-burn debate. Essentially, any avoidance flight would still operate within the parameters of additional fuel burn set aside for any ordinary flight. It completely negates the notion of fuel burn being an inhibiting factor for contrail avoidance. Good stuff.
I may just use this in a future post if you don't mind.
Fire away! We are just about to reach an inflection point. The UK Government is about to announce the next phase of the Jet Zero Task Force programme and it appears they are NOT going to continue with the contrail mitigation aspect of this critical body. This is nothing short of a scandal because it will cede the UK’s world-leading position on contrail mitigation to other nations. As explained, the UK is uniquely placed to run at-scale contrail mitigation trials on the North Atlantic because NATS controls the eastern half of the airspace (NavCanada runs the other half and they are far more engaged with this idea). Airlines, academics, NGOs, pilots and ATCOs are keen to do this, but the UK Govt has decided not to bother?!?! Outrageous!
I'm surprised to hear that. All signs seemed to point towards a concerted effort from the UK to address contrails.
Definitely within the aviation community - manufacturers, airlines, academics, service providers. What we need is significant weight being thrown behind this at regulatory level, and there are worrying signs that the resource to do this properly (ie a permanent regulatory oversight / coordination body) is not going to be made available.