I expect that most folks would be surprised to hear that Captain Bob Pearson was demoted for six months [0] after this landing, in which he side-slipped a commercial airliner with no functioning engines, and dodged two kids on bicycles on the Gimli 'runway' (read drag strip).
Talk about a uniquely Canadian story - running out of fuel because of a mistake in Imperial to Metric unit conversion. This from someone who was in high school in 1978, The Year Dope Dealers Got an 'A' in Math.
And if you don't get that joke, you're not a Canadian who grew up in the transition from Imperial to Metric.
IIRC they put a few other aircrews into the same scenario in simulators, and they all crashed. I think what the crew accomplished here is one of the most impressive and inspiring human feats I've ever heard of; more people should be familiar with the story.
Like, sure, Pearson had glider experience... but he applied that experience flawlessly in an aircraft with a brick-like glide ratio, landing with no slats or flaps, all the while losing control authority as the airspeed dropped and made the RAT less and less effective, with 69 human lives at stake. Holy shit.
For anyone who's interested, Wikipedia is full of these stories of disasters and near-disasters, and they make for interesting reading.
A glide ration of 12:1 is not great, but isn't exactly brick-like either. A Cessna 172 has a glide ratio of about 9:1. Pilots spend a lot of time practicing gliding in airplanes like that (Cessnas, Pipers, etc) during primary training.
I doubt they practice it much in 767s, though, despite the fact that they actually glide better. :)
You usually don't practice gliding when learning how to fly a small aircraft, they simply don't glide very well.
What you of course do are power-off landings – on airfields, for example from the downwind, and simulated, i.e., you make a go-around just before landing, outside an airfield. Sometimes, it works, sometimes, it doesn't, there are many factors … that's why you actually fly with power idle and not with power off. There're still a few incidents, i.e., somehow the practice becomes tool real!
All in all, power-off landings and other emergency training are an important part of becoming a pilot but you don't spend that much time for them. Other things are much more time-consuming in a typical 45-hour syllabus.
Related fact: the glide ratio does not depend on the aircraft weight, only on the aerodynamic efficiency (the ratio between your lift and your drag), so it is useless to throw weight to reach further like maybe you have seen sometimes on movies. Less weight will make you descend slower but not further. Normally, the longer your wing, the higher your efficiency. See for example the pictures here: https://en.wikipedia.org/wiki/Aspect_ratio_(aeronautics)
Losing weight will reduce stall speed, allowing for a slower and safer landing. Modern competitive gliders carry a substantial quantity of water ballast - the extra weight improves glide speeds, but it can be jettisoned before landing.
where so much of the plane broke that they had to invent a new way to fly it.
I can't turn up a reference right now, but like you say, in the next few years that failure was repeatedly simulated, and all the simulated planes crashed.
(IIRC, Haynes declined to try his hand at any of the simulations, explaining that the one time when it really mattered was enough for him.)
12:1 is actually not bad.. A classic glider trainer (SGS 2-33) in average condition is just a bit better.. The difference is the best glide speed. 50mph vs 150mph.
Slipping to lose altitude fast is a regularly trained maneuver for glider pilot.
I have flown gliders at a beginner level (so no flap) and the reason we did side/straight ahead slips was because we came in too high (emergency procedure or bad estimation) and would have ended up touching down too far with not enough space left to land safely.
Flaps do 2 things: smaller flap deployments increase lift without increasing drag much; larger increase drag without increasing lift much (beyond that of using flaps at all).
You want to be going as slow as possible when you land (aircraft make poor racecars), and most aircraft call for some level of flaps on landing. Increasing lift lowers the stall speed, which is good, and increasing drag allows you to lose altitude without gaining speed. Without flaps they would have to land too fast.
But that is a side effect of flaps. So what you are saying is that they had planned their pattern assuming they would be able to extend flap on final but couldn't and ended up too high?
I assumed they came in a bit too high as an insurance (you can burn height but can invent it), but just ended up with a lot more than they expected just because if their lack if familiarisation with the situation in that plane, so much that the dive break alone weren't sufficient to burn it.
Yes, typically you'd want to come in a bit high (or fast; you can always trade speed for altitude to an extent).
Then, you put in flaps to have a less efficient wing profile and descent more steeply (without gaining excessive speed).
However, here they did not have enough power to do that, so the Captain put it into a slip: flying uncoordinated, with (say) left rudder, but right aileron, flying somewhat diagonally (or rather, flying straight ahead still towards the runway, but presenting not only the nose, but a bit of the aircraft body to the wind).
That gets you down quite well.
Those are really the techniques when you're too high on the approach:
1. Flaps
2. Slip
3. S-Turns
Landing the plane was incredible, but having the plane take off without enough fuel was outright negligence. I'm pretty sure the airline industry is more keen to have pilots who follow procedures and avoid risks in the first place than heroes that miracolously solve trouble they created.
Not that the pilot was the only one responsible off course, but he had his share of blame in the whole thing.
The US doesn't use imperial units. It uses customary units. An imperial pint is 25% larger than a customary one.
Metric conversion in the UK isn't complete: on road signs, distances are in miles and speeds are in miles per hour. Pints are used to serve draught or keg beer.
In aviation, height/altitude is measured in feet or flight levels (hundreds of feet), horizontal distance is measured in nautical miles, and speed is measured in knots.
With milk, the measurements used seem to depend on the type of milk sold. If it's regular milk, it will be sold by the pint. If it's UHT or filtered milk, it seems to be sold by the litre.
Nautical miles and knots kinda make sense because "Historically, it was defined as one sixtieth of the distance between two parallels of latitude separated by one degree."
Feet for altitudes are not ideal, but it's become a convention (in China they use meters) (Now if they were to mix feet and miles in the altitude that would have been bad)
Actually Liberia and Myanmar have been converting to Metric, so the USA is likely the last place where people are not being taught Metric. Unless it's improved and Metric is being taught in American schools?
My science education, at least in secondary school, was all in metric. I graduated from high school in 2003. The issue is that it isn't used here in everyday life, so it becomes "that weird thing from science [which I already disliked because of the math]".
I've done experiments switching to metric. It's not a good idea to rely on my GPS for speed limit information. My home thermostat apparently doesn't have a Celsius setting (and would confuse my wife if it did). It's difficult, but mostly possible to switch here...but what's the point? It's a lot of work for comparatively little benefit.
Metric has been taught in most American schools since the 70s. Nearly everyone here learned it at some point, but most people don't use it day to day, so they don't think in it.
yeah but its not like its pushed much outside of chemistry. my niece and nephew have learned less about it than I did over thirty years ago.
it simply is not a priority, it could be slowly slipped into prominence by emphasizing the measurements on everyday items instead of making those in small print
>yeah but its not like its pushed much outside of chemistry
Every science class I had in high school used metric. We also spent a fair amount of time going through it in elementary and middle school math classes.
My younger sister (by 20 years) spent a good deal of time on the metric system in her math classes.
American influence on Canada means they have oven temperatures in Fahrenheit, recipes in cups, American paper sizes, furniture and buildings in inches etc.
Britain has all of this in metric; the beer, road signs and casual (non-medical) body measurements are the only exceptions.
Ontario build code is hilarious. For example, table 9.23.10.1 specified the size and spacing of studs in walls. For interior walls, the maximum stud spacing is 406mm on center, and minimum stud size is 38x38mm.
If you didn't know this was 16" on center, and 2x2 framing, you'd think some mad drunk person had come up with these numbers. I also like to imagine building inspectors walking into a building and saying "Oh, these studs are 407mm apart. Tear the building down."
And in official government communication, it is nominally metric, but you'll see things in e.g. building codes like "hallways must have a width exceeding 914mm", which is really just 3 feet.
It's boggling that the US hasn't moved over yet. At a minimal, all Interstate speed limit signs should be required to have both mph and kph (there are a few highway signs like this, but they're rare). Mandate in 8 years, they'll be kph only.
Why? Most industries that should be using metric already do in the US. Cars use metric fasteners, etc. When i worked in a lab, everything was metric.
Imperial is only really used in consumer facing situations. If we forced everything over to metric, would it make that much of a difference? Would the US economy suddenly surge due to a more efficient system? Unlikely.
But the consumer-facing side is the largest side. Think of all the extra bolts sold, all the new signs needing changing. This will be a great economy surge! :-)
The US is a huge country. Just to replace the road related signs alone means replacing or modifying hundreds of thousands of signs. There's mile markers (at least 48,000 alone given the 46,876 miles of interstates in the US), exit signs, distance to destination signs, and speed limit signs. These signs are rarely replaced unless they're damaged so 8 years would still require a lot of unexpected maintenance.
Yes, and if you had started in the 1970's it would have been done by now. But since the press thought it was "dictatorial", there wasn't much interest at the time.
So now you have 40 years of new signs to replace :-)
I think the US could gradually move to metric, but as with the UK, there's no need to replace miles as a distance measurement. In some ways, I think it'd be nice to always keep mph/miles... but otherwise, for weights and measures, metric would be superior.
And hey, if it's good enough for NASA, it's good enough for the rest of the states. ;)
Worst hit, would probable be the automobile industry. But I'd say there'd be advantages to metrification there too.
Why? The French system has exactly two benefits: it's popular, and it's easier to perform abstract conversions (i.e., conversions between units on paper). OTOH, it is worse at performing concrete manipulations (i.e., dividing one physical quantity into another): accurately cutting or dividing quantities into tenths without the aid of a guide of some sort (e.g. a ruler or measuring cup) is so difficult as to be basically impossible, while cutting or dividing into halves is so easy that a child can do it, and thirds are not much harder at all.
Yes, it happens that it's easier to 'do science' currently using French units, but that is because all of the standard constants happen to be based in those terms: there's no fundamental reason one couldn't use Rankine instead of Kelvin and so forth.
I won't claim that the standard system of units is perfect (the partial decimalisation the Brits attempted in the 19th century was misguided): indeed, it could get a lot better: nautical miles are probably better than statue miles; a reset in the length of the yard so that there are 1,728 yards in a mile would probably be a decent idea; a cup ought to be 16 cubic inches; and so forth.
But throwing away 12 (with its divisors of 6, 4, 2 & 3) for 10 (with half as many: 5 & 2) was a foolish, foolish decision by the French.
If they'd really wanted to be revolutionary, they'd have adopted base-12 numbering instead of trying to fit the world to base 10.
(I will grant the the French system of paper sizes is elegant, and I wouldn't mind us adopting a similar system based, of course, on the yard)
By your count, it seems that the metric system (do you call it the French system to devalue it? seems like it) has 3 points: elegant paper sizing, easier to do science, and popularity.
By your count, the "standard" system (how is it standard if it's used almost nowhere?) has 1 point: A foot being 12 inches means it has more divisors than 100 cm to a metre.
So, therefore the final score based on your appraisal is Metric 3, Freedom Units 1.
Historically, it seems baffling. Their real name, "imperial units", are a clue that they're all but rooted in freedom. They're inherited from the country that the US broke free from…
Plus, the Metric system stems from the French Revolution, making it a better contender for the term "freedom units".
Finally, wasn't there a whole PC phase in 2003 where expressions with "French" in it, like "French Fries", were renamed "Freedom Fries"? It all makes things rather confusing.
The times when the measurement can be divided by 2 are either so rare as to be irrelevant (the room isn't an even number of inches long anyway, and adding feet makes the calculation worse) or arrive by design (my dishwasher is 900mm wide, check the factors in that).
The paper sizes are German, and adopted by the ISO.
In physical trades like carpentry, brewing, farming & so forth, being able to easily halve, double or treble quantities is quite convenient. The customary units, being based on powers of 2 (with a few 3s thrown in …) tend to be really good at this, as anyone who's ever brewed or handled produce in standard units knows.
Dealing with French units is a pain.
(as an aside, the reason I call them 'French units' is because the name 'metric' privileges them: our standard units are no less a system of measures than are they; this too is my problem with 'SI,' since our system is (or was) likewise international)
The dishwasher was intended as an example for carpentry: standard kitchen cupboards etc are made in multiples of 300mm. It's the same for things like floor tiles, doors, etc.
No farmer or brewer deals in units that are easier to half in American rather than metric units. They use tonnes, hundreds or thousands of litres, and large areas. Outside America, they don't need to convert between units of the same type: no acre-feet, bushels, pounds, tons, or all that crap.
Calling them "French units" sounds like xenophobia. The American system was never international, and the British system didn't extend that much further than the French, at the time of the empire.
> They use tonnes, hundreds or thousands of litres, and large areas. Outside America, they don't need to convert between units of the same type: no acre-feet, bushels, pounds, tons, or all that crap.
In America, anyone who would deal solely in tonnes can deal solely in tons; anyone who would deal solely in hectolitres can deal solely in barrels (traditionally, 128 quarts); anyone who would deal solely in kilolitres can deal solely in tuns (traditionally, 1,024 quarts). No-one in America has to say '7 tuns, 2 hogsheads, 3 gallons, six quarts and a fluid oz' any more than he'd say '7.2850546 kilolitres.'
> Calling them "French units" sounds like xenophobia.
Oh, I'm not xenophobic! I just don't think they deserve a privileged position.
> The American system was never international, and the British system didn't extend that much further than the French, at the time of the empire.
The American system was used in Liberia; prior to the Russian Revolution the majority of the peoples of the world used systems of measurement substantially similar to the Anglo-American system, and could (should have, IMHO) rationalised and standardised that, rather than adopting the objectively inferior decimal principal.
> anyone who would deal solely in tonnes can deal solely in tons
Then your argument that these quantities are easily divided is irrelevant.
> 7.2850546 kilolitres
My house's water meter measures up to 99,999.999m³, or in litres up to 99,999,999 litres.
Europe other than Britain and Ireland didn't use the British system, and neither did their colonies, China, Japan, etc. All the British colonies except the USA chose the metric system after independence.
The SI system is the only one that's truly international, set up by international treaty between many countries.
And really they are SI units, the 'International System of Units', which may or may not 'privilege' them, but is certainly both correct and normal usage.
Yes, easy halving and quartering was important back when the population was not used to decimals. But surely, most people these day can tell that half of 100 cm is 50 cm, a quarter is 25 cm, and a third 33.33 cm.
So, the Gimli glider had a glide ratio of 12:1.
We're 10 km high, how far can we glide? Well, 120 km.
That's how we'd compute it in a metric world. In the real world, the Gimli glider was 32,000 feet high. How many nautical miles can it glide? Quick?
> In the real world, the Gimli glider was 32,000 feet high. How many nautical miles can it glide? Quick?
In the real world, the Gimli glider was 9,753.6 m high. How many km can it glide? Quick?
Of course, in real life one would cheat: a nautical mile is about 6,000 feet, so 32,000 feet works out to about 5 nautical miles, which means that it can glide about 60 nautical miles. One can always grab a calculator (or slide rule — they're actually quicker at this than calculators) to be certain (12:1 at 32,000 feet gives 63 nm/110 km).
> In the real world, the Gimli glider was 9,753.6 m high. How many km can it glide?
117,043.2 m. In about 5 seconds in my head. By doing value × 10 + value × 2. Because multiplying by 10 is so easy, because arabic numerals are in base 10.
And by cheating, which obviously we would do as a first approximation, it is also much more trivial in SI units: 9,753.6m is about 10km, × 12 → 120km. At most 1 second to find. Faster again.
But my fundamental point: we already have the mnemonics ready for base 10, and we won't switch away from arabic numerals any time soon, so we might as well benefit from it.
It isn't a competition. After all, the metric system is screwed up: having 60 seconds in a minute is a pain (but wow, so many divisors! — really though, just an inheritance of an ancient culture that did not use base 10 numerals; using higher bases isn't an indication of modernity) and the fundamental definition of the second doesn't map to any physical reality in an intuitive way anymore.
And you can count by twelves on the knuckles of your fingers, so anyone who still needs to count on his fingers can still do it (I'm not certain why this is such a selling point for decimals: surely we're all intelligent enough to use higher bases?).
In most English-speaking, metric-using countries, hospitals use the metric system for measuring weight and height, but it's common to still hear imperial units used in casual conversation. In Australia I definitely still hear people talking about height in terms of feet and inches. Weight tends to be in kilograms these days though.
This is fairly new in Canada. 10 years ago (long after the conversion to metric), hospitals and doctors used to speak in feet/pounds. As they have switched to metric fairly recently, I expect people to slowly get used to it and soon starting using metric for height and weight as well.
Britain has switched entirely to metric in healthcare, removing the last "friendly" bit of communicating to patients in Imperial.
The risk of confusion was too high, and there was at least one case of a severe overdose when a weight was accidentally given in pounds rather than kilogrammes.
If an American child was hurt outside the USA, and the parent overheard the nurse saying their weight was 55kg, would they know whether that's accurate? That's why it's important that the same units are used at home and in science.
So it turns out that passenger jets do not carry backup batteries. This poses problems when all engines fail, as many functions are fly-by-wire, and require power.
Th RAT comes to the rescue in such situations. Its a Ram Air Turbine which pops out of the body when called upon. The turbine spins and generates just enough electricity to power the crucial instruments and controls.
I was touring a Hamilton Sundstrand factory a long time ago that manufactured these RATs. They had a tally board up that listed situations where the RAT was deployed and the number of people that survived the incident.
Modern jetliners have batteries in case of engine or generator failure (you can buy a 767 battery here for about $11,000[0] http://www.skygeek.com/saft-018550-000-nicad-battery.html). And, of course, to start the plane should you not have any ground power.
Of course, they don't power much - typically a few backup instruments and the APU starter - so the RAT[1] is used to power certain hydraulics/instruments so that the pilots can maintain control.
The RAT is backup power for the hydrolics. Do you have a citation that there's no backup battery for the electronics, because I don't believe it. Even for the crappy 25 year old not-approved-for-IFR GPS I had in my Cessna needed the engine/alternator to fail plus two separate batteries to drain before it would turn off. I can't believe the electronics on a fly-by-wire airliner are less redundant.
RAT provides electrical generation too. Its all layers of protection, there are batteries for limited duration and limited equipment. RAT provides more (duration and functionality).
There are some components that are considered like that GPS that have small enough power requirements and are critical enough that they can have significant battery and others that are powered by the RAT, and yet others that just don't work with a main engine failure.
Highly suggest watching some of the Mayday episodes about the power failure incidents like Gimli, its very educational.
I was trying to paint a picture of why the RAT is needed, in order to share my admiration about the people who build it.
I don't know exactly which systems it powers, but have been told that in the case of engine failure, the plane cannot fly without it. You may be correct about the specifics.
The APU provides electrical power but only when there's fuel for it to burn. In the case of the Gimli Glider, it therefore would not have worked.
If we look at the case of Cactus 1549 [1], though, we see Capt. Sullenberger turned on the APU immediately after both engines failed. This has been hailed [1,2] as a good decision -- no doubt because the A320 relies so heavily on electronics for control and it could have helped them restart the failed engines.
Commercial jets certainly do also carry traditional batteries for various uses. Take the Boeing 787 as an example; its onboard batteries originally presented a fire hazard [3].
No, an APU is (in most aircraft that have them) actually a small jet engine that GENERATES electrical power, as opposed to storage. In some aircraft, the distinction between the onboard battery and the APU is quite clear. I know one jet that this is true of the the A320 family.
The startup procedure for that aircraft relies on either a tether from the ground to provide external electricity, or on the battery to provide electrical power to the instruments/HUD before the APU is spun up.
"Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress"
As the page says, they did not detect the cloud, because it was not clearly visible and onboard instruments dedicated to detecting ashes did not work with that particular dry type of ash.
1) Per my first flight instructor, this is the reason students now learn how to forward slip. Up until then it was just viewed as a glider move. Thankfully the captain was an experienced glider pilot. It's required to demonstrate this maneuver for your private license (not sure about sport license).
2) This ultimately led to overhaul and standardizations for fuel / weight calculations.
3) Because the engines powered the electrical systems via the alternator, the plane lost a number of electrical systems until the ram air turbine kicked in (amazing little invention and kinda saved the day). Afterwards, many subsequent aviation systems were designed to be operated independently from requiring the alternator to be running.
Good documentary/recreation on the incident: https://www.youtube.com/watch?v=Bct1mWUp8to. Miraculous that everyone survived, the captain deserves an accolade for quick thinking.
> 2) This ultimately led to overhaul and standardizations for fuel / weight calculations.
You have no idea how hard it is to get Americans to use 100% metric everything, even in the year 2016 in a highly technical field. It's incredibly frustrating. I'm amazed at the number of people under age 30 who have clearly not been taught even the basics of the metric system in middle school and high school, or intentionally disregarded/forgot it.
Working in the US domestic economy is unavoidable to do many things in US customary units when construction/physical engineering of things is involved. For example if building mission critical telecommunications towers to EIA/TIA 222G standards, everything is going to be in US customary units (the tower structure itself, the fasteners, the guy cables, the anchors, the foundation/concrete job, the dimensions of the equipment shelter, the electrical conduit, etc).
>You have no idea how hard it is to get Americans to use 100% metric everything, even in the year 2016 in a highly technical field.
American in a highly technical field here. I have no issues with using SI units when appropriate. But there is a tremendous lock-in, at least in some areas. Aerospace is a nasty mishmash, resulting in things like aircraft that "think" about altitude in feet, fuel in pounds, gear displacement in inches, but electric field strengths in W/m^2 and geopositioning in meters. All of those choices were made long ago, I'm stuck with them. My only defenses are to keep meticulous track of units and convert where necessary (while paying attention to things like numerical error).
we are pretty much resigned to the fact that buying all of the pieces to build a datacenter/colo/telecom facility, everything is going to be in US customary units, because that's what the suppliers have. It's a vicious cycle of nobody in the US choosing to stock metric items, so nobody can buy it, and all of the end users just use things that are US units. It can be the smallest things like threaded rod uses to hang overhead fiber trays in a datacenter (all of the fasteners, bolts, nuts, the rod itself, etc) are all in US units. All the way up to the largest things like $150,000 generators where all of their specifications are in US units and fuel consumption figures in gallons, etc. If it involves the construction industry it's 99% of the time going to be US customary units.
We only get down to proper metric units when dealing with the fiber itself, but even that is lashed to aerial pole-to-pole strands, where the steel strand is in US units, all of the hardware is US.
The battery backup shelves for large AGM lead acid batteries: All US units. The batteries themselves are specified in inches and pounds. Once again it can all be converted, but that's the default unit from the manufacturer. Floor loading calculations? Pounds per square foot.
>However, on September 23, 1999, communication with the spacecraft was lost as the spacecraft went into orbital insertion, due to ground-based computer software which produced output in non-SI units of pound (force)-seconds (lbf·s) instead of the SI units of newton-seconds (N·s) specified in the contract between NASA and Lockheed.
I know of Chinese manufacturers making parts for US customers using out-of-spec metric materials that happen to also be in-spec for imperial. Eg a 6.5 mm steel plate that was made too thin for the 6.5 mm tolerance might be within tolerance for 1/4 inch (6.35 mm). There's a market for this "faulty but turns out to be useful" material because metric is more readily available in China.
I have a feeling that with the decline of American manufacturing, they'll feel more pressure to convert to metric because it's a bit cheaper on imported things and there's less locally made stuff that needs to convert.
The thing is that what's left of American manufacturing tends to be producing the things that you just mentioned: steel, fasteners, rebar, etc. The labor advantage that China has is more than offset by the massive weight and volume construction materials have for a given price.
Non-construction materials are already readily available in metric units. I can buy grade 8 bolts in any size, metric or US customary. I can't buy 400 x 800 plywood, and why the hell would I want to? Everything here is built on 24 or 18 inch centers. You'd have to be insane to build a house using metric dimensions.
US customary units are nowhere as difficult to use as people make them out to be, especially at the scales being used for construction. I find metric and US customary equally easy to use, and I think that metric is much easier to use when it comes to electricity, but I find US customary much easier to use for everything else.
For instance, the meter is widely held to be better than the traditional US customary units. I think this is true for science, but when it comes to everyday uses I find the US system easier to perform math with purely because it's base 2 rather than base 10, and most of the time I'm dividing things in half several times.
Need to find the center of a 1-7/8" board? It's 15/16ths, which is really easy to calculate if you understand fractions. That's basically like figuring out the center of a 50mm board -- 25mm, obviously. However if you divide each board again, you get 15/32nds, or 12.5mm. If you divide again, into eighths, you get 15/64ths, or 6.25mm.
Maybe 15/64ths seems a bit clunky, but my tools usually have markings down to 64ths, and I have bits available all the way down to 64ths. The example I picked was deliberately bad for US imperial, and it still was pretty easy to calculate.
I think US customary units are really confusing to metric types because they don't really have a reason to use fractions in daily life. Math with fractions is really easy to do in your head though, and most tradesman are doing the math in their head.
I wouldn't be surprised if we saw a bigger push towards metric as education shifts away from pencil and paper. Metric makes way more sense than US customary does when you are doing math on a computer.
On the flip side of this I noticed (from attending school in both countries) that in math radian was used more often than in Germany (which is a good thing imo).
> You have no idea how hard it is to get Americans to use 100% metric everything, even in the year 2016 in a highly technical field. It's incredibly frustrating.
I'm equally frustrated by how hard it is to get others to use standard units instead of the French ones. There's no particular reason why 'technical fields' should mandate use of French units: one can fly an æroplane, run power to a lightbulb and get a man to the moon all in standard units — indeed, that's how those things were initially done.
Not quite. At least as far as the flight guidance and navigational systems, NASA used metric internally for the moon missions and had the computer display the converted equivalent in US customary units to the crew.
There is a reason technical fields should mandate uniformity and compatibility, and that isn't going to happen with customary units (so called because they're not even compatible with pre-metric British units).
Sure, you can fly your plane with bolts measured in inches and fuel measured in pounds, but good link getting replacement parts or accurate refueling next time you're in a stopover in Japan or Italy or Egypt. And have a good time trying to sell machine parts into an international market, or trying to buy from that same market.
Zeveb, the US customary units, "based on English measure passed by parliament under the reign of Queen Anne in 1706" [1] are inferior to the international SI units.
- prefixes based on powers of 10 are better aligned with how we calculate today, namely with base 10 numerals, and decimal fractions (unless we switch to base 12 or base 8 numerals).
- a single unit per physical quantity, together with prefixes, is better than the proliferation of units in those customary systems (often with different units of the same physical quantity in different contexts, for example length vs area vs liquid volume vs non-liquid volume, or mechanical energy vs heat energy).
- the system is coherent and somewhat minimal.
- the units are derived from the world, not from the length of some king's feet or arms or what have you. Of course, that's a somewhat subjective benefit.
At any rate: the original metre was 1/10,000,000 the distance from equator to pole (that's why 90*60=5400 nautical miles = 10,000 km, approximately). The original kilogram ("grave") was the mass of 1 dm^3 of water.
Of course, one can fly an aeroplane or get a man to the moon without SI units. One can also do it without GPS and without computers and without internet and without antibiotics and without all the other achievements of civilisation. But why would one?
> Zeveb, the US customary units, "based on English measure passed by parliament under the reign of Queen Anne in 1706" [1] are inferior to the international SI units.
FabHK, no, French units are inferior to the standard units:
- 2 and 5 are poor factors; 2, 3, 6 & 8 are superior. We ought to switch to base 12: among other things, ⅓ is not a non-terminating duodecimal.
- It is better to have multiple units for multiple purposes: anyone measuring interstellar distances in inches or metres rather than in parsecs or lightyears is, simply, wrong. One always has the freedom (and indeed, the professional obligation) to use only one unit where it matters (e.g. anyone measuring bread pans in fractions of a mile or metre is, again, simply wrong.
- The system is scaled to human beings, and eschews superficial minimality (BTW: steres and hectares). There are many useful units at human scale, with a few units where needed outside that scale (there's not really much need for a lot outside of human scale).
The units are derived from the world: the nautical mile is equal to one minute of latitude (that's 1/60th of 1/360th); a pint is a pound of water.
- The units are useful for manipulating concrete quantities. Half a volume of liquid is itself a useful measure, as is double (it goes mouthful → jigger → jack → gill → cup → pint → quart → pottle → gallon and so on, doubling all the way up until a tun). As a computer guy, it's pretty awesome to see 64, 128 & 1,024 in my unit quantities.
As I note elsewhere, I'm in support of rationalisation of the system: history has not been kind (c.f. rulers who kept the tax per unit the same, but decreased the size of the unit). I think that there's definitely improvement to be made.
But throwing it all out and adopting a decimal system goes in exactly the wrong direction.
I enjoy the discussion, and agree that base 10 is suboptimal. Base 8, 12, or 16 would be preferable (8, 16 due to affinity to the binary system; 12 due to the factors). However, we are stuck with 10 for now. (Surely there's an argument against God here.)
If we lived in a base 8 or base 12 world, a radically rationalised version of the customary royal measures based on doubling or factors 8 or 12 might be preferable. But we are not.
> It is better to have multiple units for multiple purposes.
Why?
Differences in scale are easily accounted for with the prefixes:
mili, micro, nano, pico, femto, atto takes you down to 10^-18; with zepto and yocto you get to 10^-24.
kilo, mega, giga, tera, peta, exa takes you up to 10^18; with zetta and yotta you get to get to 10^24.
You'd have a stronger point if you had France vs. US and no other standards.
In reality, you have the accepted world standard and the US one, with a small smattering of UK units thrown in. To argue the entire world should switch back to the US standard instead of the other way around is ridiculously obtuse.
> To argue the entire world should switch back to the US standard instead of the other way around is ridiculously obtuse.
The entire world switched to one country's system once. All of Europe used substantially the same system, and switched from it to one country's radically different system.
There's no reason it couldn't be done again. If it made so much sense to do one thing (of course, I don't actually think it did make that much sense: it was in the main driven through by governments seeking to radically break with the past) then surely if it makes sense to do something else, we all ought to?
Pretty sure #1 isn't accurate. I wasn't required to forward slip (or side slip, for that matter) on my FAA checkride nor have I been required to do so during any biennial flight review.
However, transport category aircraft (among other issues) have swept wings, which are far less stable in a slip - so slips are neither taught nor recommended for jets.
Huh. I'm wrong then obviously. Wonder if it's never come up as I tend to forward slip on crosswind landings. Don't recall a DPE ever even mentioning slips.
It's interesting that slips are now more prevalent in training, because they were absolutely crucial when I learned to fly (In a J3 Cub w/ no flaps). It's absolutely a blast and can get you on the ground a LOT faster than 30 degrees of flaps will.
I remember seeing an entertainingly bad TV movie of a very similar incident. I think it was this one, not the Gimli incident.
But we learnt about the Gimli Glider in my university computer risks course. It was a masterful piece of flying (and you'll note that most people who've tried to reproduce it in simulators fail).
There's a lot of flights there with casualties (including one in 2005 where a pressurisation failure caused the crew to pass out; the autopilot flew the plane to Greece where it entered a holding pattern until it ran out of fuel; interceptors spotted a flight attendant trying to land the plane with portable air equipment, but he didn't make it. No survivors). Airliners don't really glide well.
Many airliners glide quite well - they can glide quite a bit further from a given altitude than can general aviation aircraft that are (probably) more likely to run into a scenario where they'll need to glide. Air Transat 236 managed to glide 120km and land safely after running out of fuel.
The Helios flight in 2005 was unfortunate. The flight attendant trying to control it had some pilot training, but not enough to handle an out-of-fuel airliner at relatively low altitude.
Ah. I read about this in Uncle John's Bathroom Reader (which is an excellent set of books for anyone who is compulsively knowledgable, by the way)
It's a fascinating case study in failure recovery in the worst possible scenerios, and how systems fail to begin with.
...Come to think of it, those are all subjects Cantrill likes to talk about. If you like playing Bryan Cantrill Bingo, I think this might make its way onto your scorecard soon...
A similar incident happened on Air Transat 236.
Pilot had to glide further, about 120km over the Atlantic, before landing on an emergency landing strip in the Azores.
> Following the successful appeal against their suspensions, Pearson and Quintal were assigned as crew members aboard another Air Canada flight. As they boarded the aircraft, they realized that airplane was the same one involved in the Gimli incident.
That's great, but I wonder how big of a coincidence this is - how many aircraft did Air Canada have, especially running on presumably the same leg that Pearson and Quintal would have been running?
"The Crash of Flight 232" is also really interesting. In some ways it's the opposite of the Gimli Glider in that 2/3 engines were still functioning fine, but total hydraulic loss meant that there was no elevator/rudder/aileron/flaps control.
I remember reading about this in Reader's Digest back in the 80s, or possibly early 90s.
One of the passengers mentioned that during the last-minute sideslip manoeuvre, he could almost tell what clubs the golfers on the course below them were using. :)
I can honestly say that after spending the whole day worried about some presentations I have to do this week, reading this makes me believe I can do anything!
Both had the right training and knowledge, Pearson was a glider pilot and Sully taught water landings among other things. But any landing everyone walks away from (or swims) alive is a good landing.
I can highly recommend the Mayday (Air Crash Investigation/Air Emergency/Air Disasters/whatever its called this week) episode that deals with this, https://youtu.be/Bct1mWUp8to, and the show in general.
I've watched this show since I was a kid — I think it's one of the reasons I went into engineering. It makes you think about the different reasons that air accidents happen, and illustrates that there's almost never a single attributable cause.
What seems initially just like pilot error may also be due also to workplace conditions, bad training, a lack of communication, or fatigue — a chain of events and circumstances that culminates in the accident. It's fascinating.
I think the very cool thing with this show is that it really illustrates how crashes are virtually never the byproduct of a single failure.
The most fascinating ones to me are the ones where there is a completely survivable mechanical failure, combined with human failures that lead to crashes. The one that comes to mind there is the plane where the engine was leaking fuel, so the tanks were not equal so the pilots engaged the cross-feed valve, causing BOTH tanks to drain leading to an out-of-fuel situation. If they hadn't done that, they could have easily made it to their ETOPS airport with minimal issues.
Also, that show makes me sound smarter than I am. I've had conversations with pilots, who will ask if I'm a pilot. Its great fun for parties when you run into pilots (GA and commercial).
The fuel imbalance check-sheet also points out to make sure that the fuel imbalance isn't the result of a leak, and they did (somewhat -- it was dark outside) try to check for a leak.
They could also have looked at the rate of fuel consumption across both tanks to determine that the fuel consumption on the right tank was way higher than the engine could consume, but that was not SOP at the time (it is now, and the A330 [and probably other planes] now compute that information and alarm on it).
Its all layers, planes, with minimal exception, really don't crash from a single failure.
> how crashes are virtually never the byproduct of a single failure
There is the wonderfully named "Swiss Cheese model of accident causation" [1] elaborating on that. An accident happens when all the holes in the cheese line up...
Yes, I am always slightly annoyed by findings of pilot error. It is not that the finding is wrong, but the terminology leads the general public to blame the pilot when the reality is usually that the error was due to the pilot having misleading, incomplete, or just plain wrong information, or the controls behaving in a non-intuitive manner or whatever.
I suppose after watching this show, I now understand it better. But I now realize that pilot error is never just pilot error. Without some other failure or extraordinary circumstance, pilots have a damn hard time crashing a plane on their own.
Yes, I think they were definitely incompetent in the AF case. It's fair to question if their incompetence is a result of poor training by AF, but not recognizing a stall very squarely falls into "incompetent" IMO.
I think that's too harsh. The pilot applied what would be appropriate for "normal law" (full fly-by-wire). Unfortunately the plane was in "alternate law", where pulling the stick was the wrong thing to do. I would blame the incident partly to bad user interface and to the fact that the appropriate action is the opposite in normal and alternate law if the plane stalls (whoever came up with thinking this was a good idea). Even worse, the second pilot can't "feel" on the stick what the first pilot does.
Understanding what alternate law is as an airbus pilot is a very basic requirement.
>appropriate action is the opposite in normal and alternate law
I'm not sure what you are referring to here, but the fact that the appropriate action was to push forward to bring the nose down was the same regardless of alternate law/normal law. The bad UI was that the stall alarm shut off when the stall became so severe, which is why the pilots pulled up to stop the stall alarm (making the stall worse).
>Even worse, the second pilot can't "feel" on the stick what the first pilot does.
The system warns on dual input when it conflicts like that. Again, recognizing this condition is a very basic requirement of understanding the airbus control system. Regardless of that, the pilots did not communicate what they thought the problem was and what they were doing to solve it. Competent pilots don't end up in a situation where one is silently doing the opposite of the other and they don't realize it.
I agree with you that the incident is clearly attributable to pilot error, maybe even incompetence. However when searching for details I came across this: https://flightsafety.org/asw-article/stop-stalling/
I am convinced that much of human error is due to bad user interface, especially in technical settings. I think it is an important lesson that both pilots failed to recognize (in a stressful situation):
1. the plane was in alternate law
2. either actions contradicted each others
I think you're very right, and we shouldn't get into an Airbus-vs-Boeing discussion here.
Nevertheless, I wonder whether that particular accident would have happened with the physical link between yokes, rather than the side sticks; and whether there are lessons to be learned from that regarding UI/human-system-interface.
Yes it's usually a very interesting mixture of human factors and technical problems. Often in combination, e.g. some technical device not taking human factors into account and leading to usability issues. Quite often a disconnect between software developers and domain knowledge is the cause of mild to very serious issues.
One anecdote of a serious aircraft problem due to a programming shortcut I remember from a conference roughly and very simplified translates to this pseudo code for something related to landing/takeoff:
if wheels_rolling()==false: in_air=true
The problem was of course...plane with wheels on the ground but not rolling due to ice (more like sliding and there was some sensor mishap that also). And well relying on the rotation of the wheels as a height indicator and many other things...
As much as I watch and enjoy Mythbusters, I rarely come out of watching that show feeling like I really learned something new or am particularly more knowledgable on a subject.
Mythbusters is fun and entertaining, Mayday is educational and entertaining.
> Mythbusters, I rarely come out of watching that show feeling like I really learned something
The earliest episodes were more scientific and educational. They spent quite a bit of time explaining how they were going to construct something and then showing how they actually built it. It became pure entertainment--devoted especially to blowing things up--once the show achieved success.
Another example of a show descending to the lowest common denominator: The first years of "Biography" on the A&E Network had stories about explorers, scientists, and world leaders--Michelangelo, Henry Ford, Julius Caesar, Marconi, Marco Polo--but now it's nothing but celebrities.
Agreed, the earlier episodes were better, but I still don't think they were great. The last season of the show (when it was just Jayme/Adam) was actually fantastic though.
I've never actually seen any of the biography series (I just associate it with shallow celebrity profiles) I'll have to dig up the earlier episodes, thanks!
I do wonder how the show by the assistants will do on Netflix. I too cannot say I'm a fan of the original. Their snowplow episode hit way too close to home and came to entirely the wrong (and a dangerous) conclusion. Testing anything having to do with snow, ice, and curved road surface on a flat, dry runway is doomed to failure with horrific reporting of results.
The problem I have with Mayday is that there is only about 10min of footage repeated over an hour (45min + ad breaks). Most of the time is filled with summaries (after ad breaks), suspense (obtained by temporarily truncating explanations), questions and hyperboles. Also, it's very US-centric, as if no citizen of other nation were as competent as US ones. Multiplied explanations for the same fact feel like they think I'm 5, and the repetion feels like brainwashing. I come out of watching feeling like it would fit in 2 minutes, even though the original non-repeated content is probaboy more than that. I'd love if they could do a cross-season episodes: "It has been found that (spoiler alert) flight XYZ failed because of reasons A, B and C. The cause A happens over 3 accidents, let's study the 2 other causes. C happened when landing the space shuttle too and in the building collapse in another country. (etc)"
That's pretty common and makes the show way cheaper to make. Discovery did a what if dragons were real "documentary" which probably had a whole 10 minutes of footage stretched in an hour. The constant repeats after every commercial were hideous.
I see the value of Mythbusters in being able to calibrate your perception to those aspects of real-life physics that you don't typically see in normal life. How does it look like when there is a gas explosion in a house? A hand grenade blow? A bicycle trying to be ridden on the bottom of a pool? Thanks to Mythbusters, I really do understand these things pretty well now.
The important thing about Mythbusters is that they have an idea and they test it. Their methods aren't always the best (or even good at all), but they take the right approach: they get an idea, and they try to verify or invalidate it. Pretty much anyone who watches an episode can think of a way to improve the experiment, and I think it's good that the show provokes that response.
Maybe you won't learn a lot from MythBusters, but it went a long way to imbibe a maker spirit in you. That I think is crucial to becoming a better engineer.
Replying to myself to point out that basically every single air incident that people are bringing up in this thread is also covered on this show. Its well worth a watch.
Outstanding program. Watching it will teach you a lot about flying. You'll become a more informed traveler and understand just how safe modern aviation is.
It's hard to believe that there is not training for a situation in which all engines are out. Heyzeus, just a little bit of knowledge (i.e. glide ratio, etc.) might save a lot of lives.
I question why a plane was allowed off the ground without a working fuel level sensor(s). Budget isnt allowed to rent cars without one. Forget the conversion errors. What if there had been a fuel leak? [1] That a plane ran out of fuel so quickly, leaving no powered landing options, speaks very badly of the regulatory regime of the time.
[1] There is another famous canadian "glider" story involving a jet over the atlantic. All i remember is that the pilot was a former bush pilot who ignored his instuments, refusing to believe he had a fuel leak.
Man it'd be convenient if that was covered in the linked article...
> Pearson consulted the master minimum equipment list (MMEL), which indicated that the aircraft was not legal to fly with blank fuel gauges but due to a misunderstanding, Pearson believed that it was safe to fly if the amount of fuel was confirmed with measuring sticks.[14]
> The 767 was still a very new aircraft, having flown its maiden flight in September 1981. C-GAUN was the 47th Boeing 767 off the production line, and had been delivered to Air Canada less than four months previously.[15] In that time period there had been 55 changes to the MEL, and some pages were blank pending development of procedures.
> Because of this unreliability, it had become practice for flights to be authorized by maintenance personnel. To add to his own misconceptions about the condition the aircraft had been flying in since the previous day, reinforced by what he saw in the cockpit, Pearson now had a signed-off maintenance log that it had become custom to prefer over the MEL. [0]
And there was no reg in place for someone to slap a big 'unfit for flight' sticker on the door. That passengers were allowed to board is totally unacceptable.
You're referring to Robert Piché and Air Transat Flight 236 [0], a dead-stick landing of an Airbus A330 in the Azores after running out of fuel mid-Atlantic.
The flight crew was assigned partial responsibility for the incident as they did not follow a procedural checklist. The originating problem was the installation of an incorrect fuel system component which allowed fuel lines to chafe and subsequently leak.
Piché was discovered to have smuggling experience which took some of the luster off his public image in the days after the incident.
Talk about a uniquely Canadian story - running out of fuel because of a mistake in Imperial to Metric unit conversion. This from someone who was in high school in 1978, The Year Dope Dealers Got an 'A' in Math.
And if you don't get that joke, you're not a Canadian who grew up in the transition from Imperial to Metric.
[0] https://en.m.wikipedia.org/wiki/Gimli_Glider
[edit: duh, added the reference. I get it, after having it being explained to me. Thanks folks. ]