6 ms·

Epic Forum Thread on Concorde (2010)

115 points by idlewords 12y ago

idlewords 12y ago
This starts off as a discussion of APUs but turns into a Q/A with participation by Concorde pilots, designers, and even a flight attendant who all clearly pine for their favorite plane ever. I couldn't pick one of the many anecdotes to highlight, so I posted a link to the entire monster thread. It rewards digging.
- brianbreslin 12y ago
  What was an APU?
  - jzwinck 12y ago
    On the Concorde, the APU did not exist. On both contemporary and modern planes, the APU is the Auxiliary Power Unit, which is a fancy way of saying electric generator. Basically a moderate-size internal combustion engine (relative to the plane; big planes have big APUs) with the usual arrangement to generate electricity. Why? Well, it's handy if a plane can start its own engines, and big engines can't usually be started by batteries, so batteries start the APU and the APU starts the turbines. The APU is also used to drive climate and entertainment systems when on the ground (and not connected to the Ground Power Unit, also mentioned early in the thread). Finally, the APU can provide fault tolerance: if the turbines are disabled in flight, the APU can provide hydraulic pressure for the control surfaces, as well as electricity for safety systems and the potential to restart the turbines. There is some correlation in turbine failures (flying through something, fire, one turbine blade flies out and destroys a second engine), but the APU is inside and less likely to fail at the same time. Related is the Ram Air Turbine, which is basically a small wind generator that can pop out of the fuselage if needed to provide some power to critical system when really nothing is working.
    - robryk 12y ago
      Minor addition: engines need compressed air to start and APU provides that, too (used for engine starting, cabin pressurization and some anti-icing systems).
creamyhorror 12y ago
Enjoyable, nostalgic thread. Later on one member (age 78) of the core Concorde design team even appears. Here's an amusing anecdote from early in the thread: ======== Whilst on the Concorde conversion course at Bristol, occasionally crews would have the privilege of meeting some of the original design engineers and draughtsmen who had worked on the Concorde project. ... Suffice to say that the senior fire officer who misread litres-per-minute as gallons-per-minute during an Olympus water ingestion test probably would not want any further publicity, likewise the apprentice who didn’t defrost the chicken before firing it into an engine running at full power in the bird ingestion test. My favourite was the supersonic hailstone story, fired as part of a hailstone ingestion test, but with uncertain results, the final resting place of said hailstone still being slightly obscure to this day. If anyone in the greater Bristol area got hit by a particularly hard snowball in the early sixties, the Filton test engineers are very sorry, and would like to apologise! However, it is often the little insights into the past that amuse one the most and stick in one’s mind. During one such conversation, with a couple of thermodynamicists, I ventured to ask how they had settled on the (rather difficult to memorise) various temperature limits associated with Concorde. For instance, why a nose temperature limit of +127°C, why not +130°C, much easier for a pilot to remember? “Isn’t it obvious?” one replied politely, genuinely puzzled by my question. “Computer generation,” replied his colleague to him, pointing his pipe stem at me. “Ah yes,” said the first, “that would be it.” They then went on to explain, in ever such a kindly manner, that, in thermodynamics, apparently the square, and the square root, of the absolute temperature of a material are terms used in many equations. Being armed mostly only with slide rules (and as they were in the vicinity of 120°C to 130°C as a limit anyway) it had been decided to make life easy and settle on +127°C as the limit, a temperature for which they could easily calculate the square and square root in their heads. Noticing my bewilderment at the thought that anyone might be able to calculate the square or the square root of 127 in their heads, they proceeded to explain it to me still further, very slowly; in the manner that one would speak to an aged and rather deaf great aunt! • Absolute zero = -273°C = Zero Kelvin = 0K • Max Nose temp = +127°C equal to 400K • √400 = 20 • 400² = 160,000. These are the people with the amusing stories to tell!
- spiritplumber 12y ago
  I thought it'd be 127°C to avoid 8 bit signed overflow...
mmaunder 12y ago
If you're wondering why the air isn't full of supersonic passenger aircraft, one of the main reasons is that high bypass turbofan engines are much more efficient than turbojet engines like the Olympus engines in the concord. (And way quieter) Turns out a lower volume or air in a gas turbine engine moving at supersonic speed is much less efficient than a large volume of air moving at lower speed.
- idlewords 12y ago
  Each engine type has a range where it's superior. Turbojets are much more efficient at high speeds, while high-bypass turbofans are better at low speeds. The Concorde burned remarkably little fuel at Mach 2, but used up ludicrous amounts of fuel at idle, taxi and takeoff. Read the thread, it's all in there.
  - Tloewald 12y ago
    If you read further into the thread, a pilot says that the high fuel consumption during takeoff was a consequence of the aircraft's weight being higher, and higher air density at lower altitudes -- the engines were not more efficient at higher speeds as an earlier post suggested. Note that the idle fuel consumption (1t/hour; not sure whether that figure was per engine or for the entire plane) was not higher than cruising (4-6t/hour) -- it was just high in absolute terms.
    - idlewords 12y ago
      Thank you; I didn't mean to imply the plane used more fuel at idle than at supersonic cruise. Fuel consumption during takeoff and climb was something like 25 tons an hour. Part of this is because the Concorde's wing has high drag at high angles of attack, most of it was due to the engines needing to be in full afterburner. The plane needed full afterburner to take off even without a full load of fuel on board. At low speeds, most of the turbofans' power goes to creating a really high-speed stream of exhaust. That's what I mean about the engines being fundamentally more efficient (at converting fuel into forward motion) at higher speeds, where the exhaust speed more closely matches the speed of the plane.
serf 12y ago
that's a cool thread, and a cool website to discover. Thank you.
aburan28 12y ago
Here is a thought, Imagine if a Concorde got hijacked? An F16's top speed is approx 1320 mph and the Concorde's is 1350 mph per wikipedia. I feel like there might have been some government pressure to take this plane out of service with all the fear mongering post 9/11
- zhte415 12y ago
  You may be interested in the movie http://www.imdb.com/title/tt0078740/plotsummary?ref_=tt_ov_pl http://www.imdb.com/title/tt0078740/plotsummary?ref_=tt_ov_p... where a Concorde isn't quite hijacked, but has some chase scenes between a Concorde and various rouge missiles and airforces.
- oh_sigh 12y ago
  A concorde going 1350 mph still has less kinetic energy than a 747 going 600mph. Also, I'm not positive, but I'd suspect that the concorde couldn't hit 1350mph at only a few hundred feet due to the really soupy atmosphere down here.
  - masklinn 12y ago
    > A concorde going 1350 mph still has less kinetic energy than a 747 going 600mph. Not really no. Remember that Ek grows with the square of speed, so you need 4.5g of 747 for each gram of Concorde, something you only get when closing in on a 747 at MTOW (400t for a -400, 440t for a -8i) and a completely empty Concorde (80t). Comparing the 747-400 and Concorde using maximum takeoff weights, the 747 comes out at 15GJ[0] when Concorde is 33GJ[1]. Using empty weight has roughly the same ratio. Even swapping the -400 for a -8i yields only marginal improvements to 17GJ[2]. With a loaded but dry plane (simulating the arrival at the end of a flight, under the assumption that fuel is a much bigger part of a Concorde than a 747) and maximum fuel load at takeoff, Concorde comes out at 16GJ[3] and the 8i at 10GJ[4]. Even if we use the same route, halve the 8i's fuel load (to account for twice the range) and replace it all with additional payload (which I'm not sure makes any sense), it's still only 13GJ. Going back to the first paragraph, fully loaded 747's 15~17GJ[0][2] would indeed beat a completely empty Concorde's 14GJ[5], but that's about it. [0] http://www.wolframalpha.com/input/?i=1%2F2+*+396890+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+396890+kg+*+%28... [1] http://www.wolframalpha.com/input/?i=1%2F2+*+185000+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+185000+kg+*+%28... [2] http://www.wolframalpha.com/input/?i=1%2F2+*+442253+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+442253+kg+*+%28... [3] http://www.wolframalpha.com/input/?i=1%2F2+*+%28185000+-+95680%29+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+%28185000+-+956... [4] http://www.wolframalpha.com/input/?i=1%2F2+*+%28442253+-+216840+*+0.81%29+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+%28442253+-+216... [5] http://www.wolframalpha.com/input/?i=1%2F2+*+78700+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+78700+kg+*+%282...
jimmcslim 12y ago
I lived in London in the early 2000's before Concorde stopped flying; I was in Fulham so happened to be under one of the Heathrow approach flight paths. I remember seeing and HEARING the Concorde coming in for landing at Heathrow. Absolutely the loudest thing in the sky! (apart from the occasional RAF flyover for Her Maj's birthday or some such...) You couldn't mistake it for anything else.
- Erwin 12y ago
  The Concorde engines were apparently based on the Vulcan Bomber's engines. There's still one of those that flies, and you can see it at airshows in Britain once in a while. I saw it at this year's Farnbourough which was an awesome experience (as was seeing the Airbus A380 take off at an extremely short distance -- when it's not loaded with fuel and cargo it's incredibly powerful and agile). The Vulcan was load, and has an incredible "howl": https://www.youtube.com/watch?v=H_ARSE8jEHQ https://www.youtube.com/watch?v=H_ARSE8jEHQ
owenversteeg 12y ago
I noticed in the second post how the MEPU was developed by Sundstrand - the same company that made calculators in the 70s. (I, as a vintage calculator collector, actually have one.) On HN we hear about pivots all the time, typically not too drastic, but imagine going from manufacturing MEPUs for the Concorde to manufacturing calculators!
b_emery 12y ago
From wikipedia: "The only thing that tells you that you're moving is that occasionally when you're flying over the subsonic aeroplanes you can see all these 747s 20,000 feet below you almost appearing to go backwards, I mean you are going 800 miles an hour or thereabouts faster than they are. The aeroplane was an absolute delight to fly, it handled beautifully. And remember we are talking about an aeroplane that was being designed in the late 1950s – mid 1960s. I think it's absolutely amazing and here we are, now in the 21st century, and it remains unique." —John Hutchinson, Concorde Captain, "The World's Greatest Airliner" (2003)[114] I really hope we get to fly in one of these, or a modern version, someday.

115 points by idlewords 12y ago

This starts off as a discussion of APUs but turns into a Q/A with participation by Concorde pilots, designers, and even a flight attendant who all clearly pine for their favorite plane ever. I couldn't pick one of the many anecdotes to highlight, so I posted a link to the entire monster thread. It rewards digging.

brianbreslin 12y ago
What was an APU?
- jzwinck 12y ago
  On the Concorde, the APU did not exist. On both contemporary and modern planes, the APU is the Auxiliary Power Unit, which is a fancy way of saying electric generator. Basically a moderate-size internal combustion engine (relative to the plane; big planes have big APUs) with the usual arrangement to generate electricity. Why? Well, it's handy if a plane can start its own engines, and big engines can't usually be started by batteries, so batteries start the APU and the APU starts the turbines. The APU is also used to drive climate and entertainment systems when on the ground (and not connected to the Ground Power Unit, also mentioned early in the thread). Finally, the APU can provide fault tolerance: if the turbines are disabled in flight, the APU can provide hydraulic pressure for the control surfaces, as well as electricity for safety systems and the potential to restart the turbines. There is some correlation in turbine failures (flying through something, fire, one turbine blade flies out and destroys a second engine), but the APU is inside and less likely to fail at the same time. Related is the Ram Air Turbine, which is basically a small wind generator that can pop out of the fuselage if needed to provide some power to critical system when really nothing is working.
  - robryk 12y ago
    Minor addition: engines need compressed air to start and APU provides that, too (used for engine starting, cabin pressurization and some anti-icing systems).

creamyhorror 12y ago

Enjoyable, nostalgic thread. Later on one member (age 78) of the core Concorde design team even appears. Here's an amusing anecdote from early in the thread: ======== Whilst on the Concorde conversion course at Bristol, occasionally crews would have the privilege of meeting some of the original design engineers and draughtsmen who had worked on the Concorde project. ... Suffice to say that the senior fire officer who misread litres-per-minute as gallons-per-minute during an Olympus water ingestion test probably would not want any further publicity, likewise the apprentice who didn’t defrost the chicken before firing it into an engine running at full power in the bird ingestion test. My favourite was the supersonic hailstone story, fired as part of a hailstone ingestion test, but with uncertain results, the final resting place of said hailstone still being slightly obscure to this day. If anyone in the greater Bristol area got hit by a particularly hard snowball in the early sixties, the Filton test engineers are very sorry, and would like to apologise! However, it is often the little insights into the past that amuse one the most and stick in one’s mind. During one such conversation, with a couple of thermodynamicists, I ventured to ask how they had settled on the (rather difficult to memorise) various temperature limits associated with Concorde. For instance, why a nose temperature limit of +127°C, why not +130°C, much easier for a pilot to remember? “Isn’t it obvious?” one replied politely, genuinely puzzled by my question. “Computer generation,” replied his colleague to him, pointing his pipe stem at me. “Ah yes,” said the first, “that would be it.” They then went on to explain, in ever such a kindly manner, that, in thermodynamics, apparently the square, and the square root, of the absolute temperature of a material are terms used in many equations. Being armed mostly only with slide rules (and as they were in the vicinity of 120°C to 130°C as a limit anyway) it had been decided to make life easy and settle on +127°C as the limit, a temperature for which they could easily calculate the square and square root in their heads. Noticing my bewilderment at the thought that anyone might be able to calculate the square or the square root of 127 in their heads, they proceeded to explain it to me still further, very slowly; in the manner that one would speak to an aged and rather deaf great aunt! • Absolute zero = -273°C = Zero Kelvin = 0K • Max Nose temp = +127°C equal to 400K • √400 = 20 • 400² = 160,000. These are the people with the amusing stories to tell!

spiritplumber 12y ago
I thought it'd be 127°C to avoid 8 bit signed overflow...

mmaunder 12y ago

If you're wondering why the air isn't full of supersonic passenger aircraft, one of the main reasons is that high bypass turbofan engines are much more efficient than turbojet engines like the Olympus engines in the concord. (And way quieter) Turns out a lower volume or air in a gas turbine engine moving at supersonic speed is much less efficient than a large volume of air moving at lower speed.

idlewords 12y ago
Each engine type has a range where it's superior. Turbojets are much more efficient at high speeds, while high-bypass turbofans are better at low speeds. The Concorde burned remarkably little fuel at Mach 2, but used up ludicrous amounts of fuel at idle, taxi and takeoff. Read the thread, it's all in there.
- Tloewald 12y ago
  If you read further into the thread, a pilot says that the high fuel consumption during takeoff was a consequence of the aircraft's weight being higher, and higher air density at lower altitudes -- the engines were not more efficient at higher speeds as an earlier post suggested. Note that the idle fuel consumption (1t/hour; not sure whether that figure was per engine or for the entire plane) was not higher than cruising (4-6t/hour) -- it was just high in absolute terms.
  - idlewords 12y ago
    Thank you; I didn't mean to imply the plane used more fuel at idle than at supersonic cruise. Fuel consumption during takeoff and climb was something like 25 tons an hour. Part of this is because the Concorde's wing has high drag at high angles of attack, most of it was due to the engines needing to be in full afterburner. The plane needed full afterburner to take off even without a full load of fuel on board. At low speeds, most of the turbofans' power goes to creating a really high-speed stream of exhaust. That's what I mean about the engines being fundamentally more efficient (at converting fuel into forward motion) at higher speeds, where the exhaust speed more closely matches the speed of the plane.

serf 12y ago

that's a cool thread, and a cool website to discover. Thank you.

aburan28 12y ago

Here is a thought, Imagine if a Concorde got hijacked? An F16's top speed is approx 1320 mph and the Concorde's is 1350 mph per wikipedia. I feel like there might have been some government pressure to take this plane out of service with all the fear mongering post 9/11

zhte415 12y ago
You may be interested in the movie http://www.imdb.com/title/tt0078740/plotsummary?ref_=tt_ov_pl http://www.imdb.com/title/tt0078740/plotsummary?ref_=tt_ov_p... where a Concorde isn't quite hijacked, but has some chase scenes between a Concorde and various rouge missiles and airforces.
oh_sigh 12y ago
A concorde going 1350 mph still has less kinetic energy than a 747 going 600mph. Also, I'm not positive, but I'd suspect that the concorde couldn't hit 1350mph at only a few hundred feet due to the really soupy atmosphere down here.
- masklinn 12y ago
  > A concorde going 1350 mph still has less kinetic energy than a 747 going 600mph. Not really no. Remember that Ek grows with the square of speed, so you need 4.5g of 747 for each gram of Concorde, something you only get when closing in on a 747 at MTOW (400t for a -400, 440t for a -8i) and a completely empty Concorde (80t). Comparing the 747-400 and Concorde using maximum takeoff weights, the 747 comes out at 15GJ[0] when Concorde is 33GJ[1]. Using empty weight has roughly the same ratio. Even swapping the -400 for a -8i yields only marginal improvements to 17GJ[2]. With a loaded but dry plane (simulating the arrival at the end of a flight, under the assumption that fuel is a much bigger part of a Concorde than a 747) and maximum fuel load at takeoff, Concorde comes out at 16GJ[3] and the 8i at 10GJ[4]. Even if we use the same route, halve the 8i's fuel load (to account for twice the range) and replace it all with additional payload (which I'm not sure makes any sense), it's still only 13GJ. Going back to the first paragraph, fully loaded 747's 15~17GJ[0][2] would indeed beat a completely empty Concorde's 14GJ[5], but that's about it. [0] http://www.wolframalpha.com/input/?i=1%2F2+*+396890+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+396890+kg+*+%28... [1] http://www.wolframalpha.com/input/?i=1%2F2+*+185000+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+185000+kg+*+%28... [2] http://www.wolframalpha.com/input/?i=1%2F2+*+442253+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+442253+kg+*+%28... [3] http://www.wolframalpha.com/input/?i=1%2F2+*+%28185000+-+95680%29+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+%28185000+-+956... [4] http://www.wolframalpha.com/input/?i=1%2F2+*+%28442253+-+216840+*+0.81%29+kg+*+%28988+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+%28442253+-+216... [5] http://www.wolframalpha.com/input/?i=1%2F2+*+78700+kg+*+%282158+km%2Fh%29%5E2 http://www.wolframalpha.com/input/?i=1%2F2+*+78700+kg+*+%282...

jimmcslim 12y ago

I lived in London in the early 2000's before Concorde stopped flying; I was in Fulham so happened to be under one of the Heathrow approach flight paths. I remember seeing and HEARING the Concorde coming in for landing at Heathrow. Absolutely the loudest thing in the sky! (apart from the occasional RAF flyover for Her Maj's birthday or some such...) You couldn't mistake it for anything else.

Erwin 12y ago
The Concorde engines were apparently based on the Vulcan Bomber's engines. There's still one of those that flies, and you can see it at airshows in Britain once in a while. I saw it at this year's Farnbourough which was an awesome experience (as was seeing the Airbus A380 take off at an extremely short distance -- when it's not loaded with fuel and cargo it's incredibly powerful and agile). The Vulcan was load, and has an incredible "howl": https://www.youtube.com/watch?v=H_ARSE8jEHQ https://www.youtube.com/watch?v=H_ARSE8jEHQ

owenversteeg 12y ago

I noticed in the second post how the MEPU was developed by Sundstrand - the same company that made calculators in the 70s. (I, as a vintage calculator collector, actually have one.) On HN we hear about pivots all the time, typically not too drastic, but imagine going from manufacturing MEPUs for the Concorde to manufacturing calculators!

b_emery 12y ago

From wikipedia: "The only thing that tells you that you're moving is that occasionally when you're flying over the subsonic aeroplanes you can see all these 747s 20,000 feet below you almost appearing to go backwards, I mean you are going 800 miles an hour or thereabouts faster than they are. The aeroplane was an absolute delight to fly, it handled beautifully. And remember we are talking about an aeroplane that was being designed in the late 1950s – mid 1960s. I think it's absolutely amazing and here we are, now in the 21st century, and it remains unique." —John Hutchinson, Concorde Captain, "The World's Greatest Airliner" (2003)[114] I really hope we get to fly in one of these, or a modern version, someday.