10 ms·

> Concorde burned 52% of its fuel just taxiing and taking off and later in the article: > Remember, Concorde burned 52% of its fuel just taxiing down the runw

by nluken 9mo ago

> Concorde burned 52% of its fuel just taxiing and taking off and later in the article: > Remember, Concorde burned 52% of its fuel just taxiing down the runway. Setting aside that these are completely different claims, the author does not cite this claim at all and it fails my personal gut check. Where is this information coming from?

vablings 9mo ago
https://news.ycombinator.com/item?id=24283386 https://news.ycombinator.com/item?id=24283386 They did burn a crazy amount of fuel on getting up to supersonic speeds though.
wat10000 9mo ago
It used about half of its fuel for taxiing, takeoff, climb, and acceleration to cruising speed. Maybe that's where the number came from originally and it got mangled in translation.
- saalweachter 9mo ago
  When I looked into this in another context (not supersonic jets), while "a lot" of fuel was used just getting the jet up to speed going down the runway, "most" of the fuel was going from 1 foot off the ground to N0,000 feet. (I was curious if there was any opportunity for some sort of system to power take-off from the ground, be it catapults like on air craft carriers or just power-transmission for electric planes, and the numbers I found were that while a surprising amount of fuel was used by the time the plane lifted off, it was more like 5% than 50%.)
masklinn 9mo ago
Yes, it sounds like the repetition of a mangled version of the SR71 stories. Burning 45 tonnes of fuel on the runway would be completely insane. Checking various links on taxiing burn yields about 2 tonnes which is a lot more realistic and reasonable (a previous HN comment indicates the 767 burns about a tonne taxiing: https://news.ycombinator.com/item?id=24283386 https://news.ycombinator.com/item?id=24283386 concorde burning twice that sounds fair) The OP might have gotten confused reading articles like https://simpleflying.com/concorde-fuel-consumption/ https://simpleflying.com/concorde-fuel-consumption/ stating concorde burned half its tank from the gate to cruise (mach 2 at FL600)
- Reason077 9mo ago
  > ”the 767 burns about a tonne taxiing” This seems incredibly inefficient. Is there a future for hybrid aircraft, which would feature both traditional turbofans and large batteries for energy storage? Batteries would eliminate the need for an APU and power the aircraft during taxi, allowing the engines to be started just before actual takeoff, and shut down immediately after landing. Either the batteries could power wheel motors directly during taxi, or the aircraft could mix turbofans with e-fans (which could also allow energy recovery during descent and help power the aircraft during cruise, reducing fuel consumption further).
  - kamarg 9mo ago
    > This seems incredibly inefficient. Is there a future for hybrid aircraft, which would feature both traditional turbofans and large batteries for energy storage? I would assume the extra weight would make it not really worth the added cost and complexity.
    - elmomle 9mo ago
      Honestly it sounds like the "right" way to do it would be electric ground vehicles pulling the planes into position, as with tugboats in water. Plane never need carry batteries into the sky and saves a literal ton of fuel.
      - masklinn 9mo ago
        IIRC towing to and from the runway has two major issues: - standard towing tractors are really slow when towing, nowhere near taxiing speed, so you need a fleet of heavier duty "fast tow", possibly dedicated (depending on price) - more traffic around the runway, which creates more airport complexity Taxibot does exist tho, and is certified, and used in a few airports. Though I think it's only hybrid not electric.
        TylerE 9mo ago
        Bigger issue is that the engines need to be idled for a while anyway to get up to proper temps, etc. you don’t want to start the engines and jam them into full takeoff thrust 5 seconds later.
dwroberts 9mo ago
American coverage of the Concorde has to try and make out that it was technically bad, otherwise they would have to face up to the fact that their country squashed the possibility of supersonic travel, through political bullying and protectionism of their own aircraft industry
- BobaFloutist 9mo ago
  And also through supersonic travel being annoying as hell and super expensive.
- fragmede 9mo ago
  Though, given the investment into the Concorde led to Airbus and all of their planes, disrupting Boeings dominance of that industry, I think they might have gotten the last laugh.
pixelesque 9mo ago
Roughly that figure (45%) was used to get to Mach 2.0 at 60,000 feet, about 45 minutes after takeoff from LHR (normally over the Bristol channel) to JFK. Takeoff and climb / accel to Mach 1.7 was done with re-heat (afterburners), which did use a lot of fuel. After that, normal power (no re-heat) was used to get to Mach 2.0 and cruising (supercruise).
prof-dr-ir 9mo ago
The article is just generally sloppy. > .. my recent trip from Abu Dhabi to LA. 24 hours door-to-door. We have the technology to reduce that to under 10. The direct flight (by Emirates) takes 16h15 mins, so that leaves 7h45 mins not in flight. If we want to bring that down to 10 hours just by making the flight supersonic then that would require a flight time of 2h15, corresponding to a (ridiculous) speed well over Mach 4.
- Reason077 9mo ago
  Not ridiculous if you’re flying above the atmosphere. SpaceX has proposed point-to-point rocket-powered hypersonic flights that connect New York to Paris in around 30 minutes. Obviously the real problem with this idea is environmental: emissions would be substantial and nobody wants an extremely noisy rocket port near their city.
  - ghaff 9mo ago
    Musk has proposed lots of things.
  - LargoLasskhyfv 9mo ago
    How do you imagine that? First thing coming to mind is the loudness of rocket starts and powered landings. Even for airports that would be too loud. At least with current regulations. So you'd probably waste time getting to some dedicated facility, far out in the midst of nowhere to care about, and getting out of a similar hole on the other side of the trip. And again regulations regarding the closure of airspaces and seas for starts and landings, as it's currently done. Which seems rather incompatible with the current system of commercial flight ops, as it's currently done. Other relevant regulations coming to mind are evacution procedures/general survivability provisions for conventional commercial flights, which are mandatory by law. However I turn that idea, no matter from which point I'm looking at it, I'm not seeing it going anywhere.
  - jrjeksjd8d 9mo ago
    Whenever I hear people talk about rocket flights I think of the Stephen King short story "The Jaunt". Humans develop near-instant transportation but you have to be unconscious while travelling. A kid avoids being sedated and is driven insane by whatever interdimensional stuff he sees in transit. Likewise for every fit 20-something being launched at Mach 5 you'd have 10 octogenarians dying of cardiovascular complications.
kens 9mo ago
The claim in the article, "Concorde burned 52% of its fuel just taxiing down the runway", is completely wrong and kind of ruins my confidence in the article. A Concorde used less than 1% of its fuel taxiing down the runway, not 52%. Source: Air France Flight 4590 Accident Report states that the plane had 95 t of fuel on board when the aircraft started out and used 800 kilos of fuel during taxiing (page 17) and 200 kilos after taxiing before takeoff (page 159). https://www.faa.gov/sites/faa.gov/files/2022-11/Concorde_Accident_Report.pdf https://www.faa.gov/sites/faa.gov/files/2022-11/Concorde_Acc... (Since there's a bunch of discussion about how to reduce taxiing consumption, I'll point out that one tonne of aviation fuel is about $700, so there's not much money to be saved by creating battery-powered tugs or whatnot.) As far as takeoff, "at the start of cruise 20% of the total fuel burnoff will have been consumed while only 9% of the total distance will have been covered." From "Operation Experience on Concorde", a paper by the Design Director. While 20% is a lot, it is much less than 52%. https://www.icas.org/icas_archive/ICAS1976/Page%20563.pdf https://www.icas.org/icas_archive/ICAS1976/Page%20563.pdf
- consp 9mo ago
  9% of the distance but 100% of the altitude. That statement completely ignores the hardest part of the flight (with respect to building potential energy) of getting at altitude.
- labcomputer 9mo ago
  > (Since there's a bunch of discussion about how to reduce taxiing consumption, I'll point out that one tonne of aviation fuel is about $700, so there's not much money to be saved by creating battery-powered tugs or whatnot.) Probably the biggest win in aviation emissions would be converting all the ground support vehicles to electric. They’re currently classified as off-road vehicles, so don’t have to adhere to the same emission standards and normal cars and trucks. Additionally, they already spend a lot of time parked at the gate, which makes charging convenient and means that workers are never “waiting” for the vehicle to charge.

by nluken 9mo ago

vablings 9mo ago

https://news.ycombinator.com/item?id=24283386 https://news.ycombinator.com/item?id=24283386 They did burn a crazy amount of fuel on getting up to supersonic speeds though.

wat10000 9mo ago

It used about half of its fuel for taxiing, takeoff, climb, and acceleration to cruising speed. Maybe that's where the number came from originally and it got mangled in translation.

saalweachter 9mo ago
When I looked into this in another context (not supersonic jets), while "a lot" of fuel was used just getting the jet up to speed going down the runway, "most" of the fuel was going from 1 foot off the ground to N0,000 feet. (I was curious if there was any opportunity for some sort of system to power take-off from the ground, be it catapults like on air craft carriers or just power-transmission for electric planes, and the numbers I found were that while a surprising amount of fuel was used by the time the plane lifted off, it was more like 5% than 50%.)

masklinn 9mo ago

Yes, it sounds like the repetition of a mangled version of the SR71 stories. Burning 45 tonnes of fuel on the runway would be completely insane. Checking various links on taxiing burn yields about 2 tonnes which is a lot more realistic and reasonable (a previous HN comment indicates the 767 burns about a tonne taxiing: https://news.ycombinator.com/item?id=24283386 https://news.ycombinator.com/item?id=24283386 concorde burning twice that sounds fair) The OP might have gotten confused reading articles like https://simpleflying.com/concorde-fuel-consumption/ https://simpleflying.com/concorde-fuel-consumption/ stating concorde burned half its tank from the gate to cruise (mach 2 at FL600)

Reason077 9mo ago
> ”the 767 burns about a tonne taxiing” This seems incredibly inefficient. Is there a future for hybrid aircraft, which would feature both traditional turbofans and large batteries for energy storage? Batteries would eliminate the need for an APU and power the aircraft during taxi, allowing the engines to be started just before actual takeoff, and shut down immediately after landing. Either the batteries could power wheel motors directly during taxi, or the aircraft could mix turbofans with e-fans (which could also allow energy recovery during descent and help power the aircraft during cruise, reducing fuel consumption further).
- kamarg 9mo ago
  > This seems incredibly inefficient. Is there a future for hybrid aircraft, which would feature both traditional turbofans and large batteries for energy storage? I would assume the extra weight would make it not really worth the added cost and complexity.
  - elmomle 9mo ago
    Honestly it sounds like the "right" way to do it would be electric ground vehicles pulling the planes into position, as with tugboats in water. Plane never need carry batteries into the sky and saves a literal ton of fuel.
    - masklinn 9mo ago
      IIRC towing to and from the runway has two major issues: - standard towing tractors are really slow when towing, nowhere near taxiing speed, so you need a fleet of heavier duty "fast tow", possibly dedicated (depending on price) - more traffic around the runway, which creates more airport complexity Taxibot does exist tho, and is certified, and used in a few airports. Though I think it's only hybrid not electric.
      - TylerE 9mo ago
        Bigger issue is that the engines need to be idled for a while anyway to get up to proper temps, etc. you don’t want to start the engines and jam them into full takeoff thrust 5 seconds later.

dwroberts 9mo ago

American coverage of the Concorde has to try and make out that it was technically bad, otherwise they would have to face up to the fact that their country squashed the possibility of supersonic travel, through political bullying and protectionism of their own aircraft industry

BobaFloutist 9mo ago
And also through supersonic travel being annoying as hell and super expensive.
fragmede 9mo ago
Though, given the investment into the Concorde led to Airbus and all of their planes, disrupting Boeings dominance of that industry, I think they might have gotten the last laugh.

pixelesque 9mo ago

Roughly that figure (45%) was used to get to Mach 2.0 at 60,000 feet, about 45 minutes after takeoff from LHR (normally over the Bristol channel) to JFK. Takeoff and climb / accel to Mach 1.7 was done with re-heat (afterburners), which did use a lot of fuel. After that, normal power (no re-heat) was used to get to Mach 2.0 and cruising (supercruise).

prof-dr-ir 9mo ago

The article is just generally sloppy. > .. my recent trip from Abu Dhabi to LA. 24 hours door-to-door. We have the technology to reduce that to under 10. The direct flight (by Emirates) takes 16h15 mins, so that leaves 7h45 mins not in flight. If we want to bring that down to 10 hours just by making the flight supersonic then that would require a flight time of 2h15, corresponding to a (ridiculous) speed well over Mach 4.

Reason077 9mo ago
Not ridiculous if you’re flying above the atmosphere. SpaceX has proposed point-to-point rocket-powered hypersonic flights that connect New York to Paris in around 30 minutes. Obviously the real problem with this idea is environmental: emissions would be substantial and nobody wants an extremely noisy rocket port near their city.
- ghaff 9mo ago
  Musk has proposed lots of things.
- LargoLasskhyfv 9mo ago
  How do you imagine that? First thing coming to mind is the loudness of rocket starts and powered landings. Even for airports that would be too loud. At least with current regulations. So you'd probably waste time getting to some dedicated facility, far out in the midst of nowhere to care about, and getting out of a similar hole on the other side of the trip. And again regulations regarding the closure of airspaces and seas for starts and landings, as it's currently done. Which seems rather incompatible with the current system of commercial flight ops, as it's currently done. Other relevant regulations coming to mind are evacution procedures/general survivability provisions for conventional commercial flights, which are mandatory by law. However I turn that idea, no matter from which point I'm looking at it, I'm not seeing it going anywhere.
- jrjeksjd8d 9mo ago
  Whenever I hear people talk about rocket flights I think of the Stephen King short story "The Jaunt". Humans develop near-instant transportation but you have to be unconscious while travelling. A kid avoids being sedated and is driven insane by whatever interdimensional stuff he sees in transit. Likewise for every fit 20-something being launched at Mach 5 you'd have 10 octogenarians dying of cardiovascular complications.

kens 9mo ago

The claim in the article, "Concorde burned 52% of its fuel just taxiing down the runway", is completely wrong and kind of ruins my confidence in the article. A Concorde used less than 1% of its fuel taxiing down the runway, not 52%. Source: Air France Flight 4590 Accident Report states that the plane had 95 t of fuel on board when the aircraft started out and used 800 kilos of fuel during taxiing (page 17) and 200 kilos after taxiing before takeoff (page 159). https://www.faa.gov/sites/faa.gov/files/2022-11/Concorde_Accident_Report.pdf https://www.faa.gov/sites/faa.gov/files/2022-11/Concorde_Acc... (Since there's a bunch of discussion about how to reduce taxiing consumption, I'll point out that one tonne of aviation fuel is about $700, so there's not much money to be saved by creating battery-powered tugs or whatnot.) As far as takeoff, "at the start of cruise 20% of the total fuel burnoff will have been consumed while only 9% of the total distance will have been covered." From "Operation Experience on Concorde", a paper by the Design Director. While 20% is a lot, it is much less than 52%. https://www.icas.org/icas_archive/ICAS1976/Page%20563.pdf https://www.icas.org/icas_archive/ICAS1976/Page%20563.pdf

consp 9mo ago
9% of the distance but 100% of the altitude. That statement completely ignores the hardest part of the flight (with respect to building potential energy) of getting at altitude.
labcomputer 9mo ago
> (Since there's a bunch of discussion about how to reduce taxiing consumption, I'll point out that one tonne of aviation fuel is about $700, so there's not much money to be saved by creating battery-powered tugs or whatnot.) Probably the biggest win in aviation emissions would be converting all the ground support vehicles to electric. They’re currently classified as off-road vehicles, so don’t have to adhere to the same emission standards and normal cars and trucks. Additionally, they already spend a lot of time parked at the gate, which makes charging convenient and means that workers are never “waiting” for the vehicle to charge.