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Comment by peeters | Hacker News Reader

The cause analysis of how they ended up with half a tank of fuel is crazy. The crew loading the fuel mistook lbs for kg. The plane's fuel indicators were faulty and required a manual procedure before takeoff. The engineer communicated that to a pilot and the pilot misunderstood. That pilot relayed his misunderstanding to the next pilot and that next pilot misunderstood the misunderstanding. And then that next pilot misunderstood the checklist indicating whether it was legal to fly with the non-functioning fuel gauge. And the flight engineer didn't catch the lbs/kg mistake. Then during a brief stopover in Ottawa, the captain thought to re-measure the fuel with the floatstick, but still used the incorrect conversion factor.

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Why don't they just ditch imperial measurements altogether?

Also, that description sounds like tracing a bug through a few layers of software where there wasn't proper error handling along the way, just trusting the data being passed around.

If I'm remembering correctly, they were in the process of switching from imperial to metric at the time.

Amusingly, the reason why the confusion was there was because at that time Canada was in the process of converting from the Imperial system to the Metric, but they had to manually convert some things still!

I wonder how many lives are lost each year (not just in aviation but globally) because the US refuses to convert to the metric system.

Or spacecraft lost: https://en.m.wikipedia.org/wiki/Mars_Climate_Orbiter

The loss of MCO is actually a very interesting story about both engineering culture (engineers noticed a problem but the organization didn’t respond to investigate/fix it) and the conversion to metric. The root came from NASA deciding to use metric on this project and a contractor using the wrong units. But it’s the kind of thing that the process should be able to catch and handle. It bugs me to dismiss this failure as “haha why doesn’t NASA use metric” because not only is it a direct result of NASA switching to metric, there are really good engineering lessons that get ignored.

> I wonder how many lives are lost each year (not just in aviation but globally) because the US refuses to convert to the metric system.

Keep in mind that the U.S. is not the only place where measures are mixed. If anything, British people end up using more measures than Americans. Here in Canada, we have a lot of things read out in both, because of the immense sticking power of customary measures.

U.S. organizations are actively encouraged and (for the most part) fully allowed to adopt SI measures, but it's not like switching road sides, where everything makes sense after you hear "drive on the right now".

Keep in mind that powered flight was basically entirely developed by Americans and pre-SI Brits, and already had more than fifty years of history by the time either pioneering country adopted SI in any significant way. It should not surprise you in the slightest that an American plane expected to hear fuel mass given as weight in pounds; in fact, it should astonish you that anyone is trying to measure it in kilograms in North America.

I'm British, so you don't need to explain using mixed systems, however in any kind of academic, engineering or scientific contexts metric units are used almost exclusively. Yes, people still refer to height in feet and inches a lot, and we'll drink a pint (a real pint! None of your mini-pints!), but that does change over time. For example older people will use stone and pounds for their weight but being younger the doc doesn't bother telling me my weight in anything but kilograms so I don't even know my weight except in Kg.

Even in Britain, in almost all engineering contexts, SI units would be assumed. Your point about Americans assuming imperial units is precisely wwhy it's so dangerous that metrification hasn't happened there.

If the US went metric, then there would no longer be any need to assume anything but metric anywhere, and it would be safer for it.

Yes, there's a long standing tradition, but it only takes a couple of generations to completely change, and that would likely be hastened by being the last large country to do so and having a large cultural footprint on the rest of the world.

If the US did convert to metric, in 3 or 4 generations the whole world would be metric, and there wouldn't be any "wrong assumptions", and it is making bad assumptions that lead to preventable failures.

If China can manage to go metric, the US can too.

> however in any kind of academic, engineering or scientific contexts metric units are used almost exclusively

This is true in the United States as well, but fueling a commercial airplane is not an academic, scientific, or even an engineering exercise. It is as routine and pedestrian as refueling a bus.

> Your point about Americans assuming imperial units is precisely wwhy it's so dangerous that metrification hasn't happened there.

Or maybe it's an argument for why "metrification" is itself dangerous. The problem is the transition, not being on either side of the fence. It seems to me that the only safe mode of transition is first to dual readout, and only then to SI-exclusive.

Don't get me wrong, I like SI units, I use them every day, and I don't long to spend any time multiplying and dividing by irregular fractions; I just don't like the dismissive "shoulda been metric" rhetoric that floats around everywhere; as though you can just stop selling letter paper and force everyone to use A-series compatible envelopes, and convert the clean (if baroque) markings on the paper products to bizarre decimal fractions of a g/m² without any empathy for the old guard.

Some people care about how Britain still drives on the wrong side of the road, but that doesn't mean they should berate you every time a drunk roadtripping Frenchman turns out into oncoming traffic.

Even in academia doesn't the US use CGS, and most of the rest of the world uses SI/MKS? We can't use the same physics textbooks.

I took high-school and college physics in the US around 30 years ago. It was all SI then, and I suspect it still is.

A British bus will be refuelled in litres, which I think was the point.

> as though you can just stop selling letter paper and force everyone to use A-series compatible envelopes, and convert the clean (if baroque) markings on the paper products to bizarre decimal fractions of a g/m² without any empathy for the old guard.

The first part was done in Britain in the 1950s, but with the weights rounded to convenient metric numbers.

> A British bus will be refuelled in litres, which I think was the point.

Refuelled in litres, but with efficiency measured in miles per gallon. It's kind of a mess.

Miles per US gallon or miles per imperial gallon?

The latter, miles per UK gallon. Watch out for that, because if you don't know better, you'll read about some car in the UK and wonder why it has such astounding fuel economy!

That's the case for cars, but I wouldn't be certain it's the same for buses, especially large fleets of public transport buses.

All three British bus manufactures give all measurements except speed in metric, although none give an actual fuel consumption. (Just "20% better" etc.)

[1], as the first reference I can find, uses both l/100km and mpg.

[1] https://www.whatdotheyknow.com/request/fuel_consumption_of_p...

> If the US went metric, then there would no longer be any need to assume anything but metric

That might be a tiny bit optimistic. I'm in my mid 50s, and UK schooling taught me nothing but metric. I vaguely remember some sort of half-hearted campaign and leaflets about it, I think that was before we joined the EU. In 2019, and we are still not there yet.

I'm not sure the last popular holdouts are ever likely to change at this point.

I'm surprised, but thankful, that the Brexit lunacy hasn't (yet) brought calls to return to Imperial and £sd. :)

> I'm surprised, but thankful, that the Brexit lunacy hasn't (yet) brought calls to return to Imperial and £sd. :)

Unfortunately:

Return of pounds and ounces? Britain might allow firms to use imperial measures after Brexit https://www.telegraph.co.uk/news/2017/02/17/return-pounds-ou...

EXCLUSIVE: Experts Slam "Bonkers" Proposal To Re-Introduce Imperial Measurements After Brexit, In Letters To Government http://www.gizmodo.co.uk/2017/04/exclusive-experts-slam-bonk...

Now that we are to be a sovereign nation again, we must bring back imperial units https://www.telegraph.co.uk/news/2017/04/01/now-sovereign-na...

Sigh. Thankfully I'd missed that. Not surprised it was Heffer, I think he'd like to send us back to about 1912. Gizmodo piece was fairly entertaining though. :)

Fortunately the post-boomer “sanity” generation are not going to accept imperial units other than pint (for beer), regardless of what people pining for a past in which they were relevant may want.

> Keep in mind that powered flight was basically entirely developed by Americans and pre-SI Brits

The french played a very dominant role as well.

> The french played a very dominant role as well.

As far as I've known, that largely involved a tremendous number of English channel crossings, but I will look more into that so I don't stay ignorant; thanks. ;- )

Hopefully you're being deliberately ironic, but your comment indicates a purely anglo-centric perspective. Continental European endeavour irrelevant except when it intersects with the homeland!

Fuselage, Empennage, Ailerons...

To name a few more aviation terms derived from French...

Aviation: https://en.wiktionary.org/wiki/aviation

Aéroplane: https://en.wiktionary.org/wiki/aeroplane

Hélicoptère: https://en.wiktionary.org/wiki/helicopter

Sortie: https://en.wiktionary.org/wiki/sortie

Hangar, Mayday (m'aider), Bombardier, Airport...

So an Frenchman, creator of he first practical monoplane, crosses the English channel before an Brit does... but the Channel is named for the English so the Brits get the credit? Nice dude...

Here are a few places for you to begin your research:

https://en.wikipedia.org/wiki/Aviation_in_the_pioneer_era

https://en.wikipedia.org/wiki/Grande_Semaine_d%27Aviation_de...

https://en.wikipedia.org/wiki/Louis_Blériot

https://en.wikipedia.org/wiki/Soci%C3%A9t%C3%A9_pour_l%27avi...

https://en.wikipedia.org/wiki/A%C3%A9ro-Club_de_France

https://en.wikipedia.org/wiki/Cornu_helicopter

https://en.wikipedia.org/wiki/L%27A%C3%A9rophile

https://en.wikipedia.org/wiki/History_of_the_Arm%C3%A9e_de_l...

Aside: How many American-made components do you see with big bold French labels on them? https://en.wikipedia.org/wiki/File:Fdr_sidefront.jpg

Lives would also be lost in the ensuing confusion if US were to switch to the metric system.

Indeed. It's only due to the skill of the pilots that lives weren't lost during the Gimli Glider incident.

Only partially. Part of it was pure luck, that no one was on the track at that moment when the plane landed on it. There were people at the track at the time, doing races, but the plane just happened to come down at the right time.

They ended up fixing it afterwards and it continued to fly with Air Canada until 2008 and it went up for auction in 2013[0].

[0] https://business.financialpost.com/transportation/air-canada...

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