* Posts by hugo tyson

362 posts • joined 20 Apr 2007

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Brit boffins build 'quantum compass'... say goodbye to those old GPS gizmos, possibly

hugo tyson
Go

Re: "AIUI the military signal has a faster chipping rate with longer PRN "

Civilian GPS really is 1023 chips/cycle so the PRN shift-and-feedback 10-bit register never has to go through zero, 'cos if it did it would stay on zero. Repeating every millisecond (nominally, subject to doppler and clock errors).

About the mil signal, the really long cycle time is for security only - makes it really hard to find unless you have pre-loaded tracking data somehow, from that encrypted almanac as you say. But that aspect doesn't add at all to accuracy: only a higher chipping rate can do that, which as you say is 10x the civvy version. But only 10x, so each chip is ~30m. You might get 30cm correlation data out of that.

The ionospheric correction - the naive algorithmic one (ramps up linearly from 0600 local to noon, ramps down from 1800 local to midnight, times cosine something I think) in civilian GPS standards docs anyway - is under 10m, ISTR it being 5m to 7m max usually. So the naive model is good for a system whose overall accuracy is 5-10m anyway. Interesting that of course the mil system needs better Iono corrections from the ephemerides (I guess) 'cos its native accuracy is higher.

But it can never be reliably that accurate. I had a GPS antenna on the windowsill of an office about 15m up. It saw half the sky OK. I generally got accurate positions, being of course the position of the antenna not my computer connected to it. But when it rained, a sloping roof across the road turned into a radio reflector and I could "see" much of the other half of the sky too. Great! you might think, but it saw the new sky with extra path length, since the new signals went across the street and back extra. So my positions were solved for about 10m away, in the middle of the road. Ain't nuthin' you can do to prevent that sort of situation short of rejecting some signals in the solver - but which ones? - whatever your chipping rate and correlation accuracy, it can still be fooled by reflections.

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hugo tyson
Coat

Re: GPS accuracy

You're conflating turning off selective availability (SA), which they did 'cos of various gulf wars, and making access to the military signals available. They didn't do the latter.

SA dithered the civilian signals to cause a wandering inaccuracy of several hundred meters. It is defeated by using a fixed ground station to work out the current offset, and delivering the difference data to receivers - this is Differential GPS. So people were working around it anyway.

With SA turned off as it has now been for decades, the civilian signals are still only accurate to a few metres 'cos the chipping rate of the PRN code (orthogonal CDMA code) is 1023 chips per millisecond, so each chip is about 300 metres long. Curve fitting to multiple correlation results gives timing to fractional chips but it's inherently noisy - so you might get actual results accurate to 10s of meters (30ths of microseconds). Solving with many satellites reduces the combined error, sure, but it's stlll meters not centimeters.

AIUI the military signal has a faster chipping rate with longer PRN sequences and so it's inherently more accurate because the basic unit of "knowing when the signal is" which you have if you're managing to track the signal at all, can be not about a microsecond = 300m, but a fraction of that. It's a 10th of that - 30m - in the old versions, and it's not in wikipedia for the latest actually secret stuff. I only ever worked on civilian receivers, so had no need to look at the mil stuff.

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Russian rocket goes BOOM again – this time with a crew on it

hugo tyson
Alert

Re: Performed as expected... SRB abort

The Shuttle SRBs nearly had a "become safe after lighting" feature which involved explosive detachment of the top cap of both SRBs, so they both became like one of those new wanky double-ended lightsabers. With no net thrust, was the idea.

This was in case only one of them ignited, to prevent making a catherine wheel out of the whole affair... it wasn't implemented; possibly the top-end flame thrower would have killed everyone anyway, and they got SRB ignition reliable enough that they always lit both, or neither.

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TalkTalk shrugs off moaning customers to claim 80,000 more

hugo tyson
Thumb Up

Re: Why? Just Why?

Me too; 79,9xx kB/s from advertised 80Mb FTTC. It's fine (touch wood).

Had one issue, it was a rusty wire just outdoors, where the pair changes to thinner indoor wire.

I should have looked closer myself, but they were fine and not too slow about coming.

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America's forgotten space station and a mission tinged with urine, we salute you

hugo tyson

Re: Men in Black

That's the book - thanks, your memory's better than mine.

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hugo tyson
Black Helicopters

Men in Black

I read in a public, academic book, that when Skylab launched, NASA was keen to see what the wrongly/party deployed solar panels, and associated damage, looked like. The NRO had secret spy satellites, of the kind which drop a film cartridge when it's been filled, which NASA were not allowed to know about, nor anyone else really. Apparently NASA had a visit from sunglasses and dark suits, who said "Your top 4 engineers on this, in here, now; no-one else. Here are some photographs. You may look at them for 15 minutes. They do not leave this room. We were never here, you never saw this." And it helped them decide that fixing it on-orbit was feasible, and what they needed to take and do. According to one of those NASA engineers.

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Time to ditch the front door key? Nest's new wireless smart lock is surprisingly convenient

hugo tyson

Why's it mounted on the door?

Why do they keep mounting locks on the door? If it were mounted on/in the frame, with the striker plate/box in the door, then you could run wires to it for power and cat5, solving several problems....

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How machine-learning code turns a mirror on its sexist, racist masters

hugo tyson

No Asian, African texts?

Problem might be there are few extensive texts in suitable form for input, which were written by Asians or Africans about the white men, nor by woman of any kind, which reflect their attitudes to the cruel imperious selfish arrogant white European male, no? Just choosing English for the language used puts that bias on the whole thing.

Can't see an easy solution, but maybe it could be improved by pre-biasing the corpus the other way.

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Hold the phone: Mystery fake cell towers spotted slurping comms around Washington DC

hugo tyson

Legality is itself location-sensitive

It's legal according to US law for the US to use StingRay in non-US places; doesn't mean it's legal according to the law of those places. What it means is that the US government won't act to prevent itself using such tech outside the US.

Remember, according to US law, US law applies over the entire universe. Really.

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What's silent but violent and costs $250m? Yes, it's Lockheed Martin's super-quiet, supersonic X-plane for NASA

hugo tyson

Re: Only Mach 1.4?

Pretty sure the boom is anywhere the craft passes at faster than mach 1, not just at transition.

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Nest reveals the first truly connected home

hugo tyson

Re: Doorbell as a cost center.

But are they ever actually *welcome* ? Unless you're expecting them by prior arrangement.

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Fancy owning a two-seat Second World War Messerschmitt fighter?

hugo tyson

Re: Why were inverted V12s popular with the Germans?

Ta. So mostly packaging then. But surely it's a dry sump *because* it's inverted, the causality direction I mean. Anyway thanks, I see what you mean.

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hugo tyson
WTF?

Why were inverted V12s popular with the Germans?

As there are nerds here, I'll ask: I've never managed to work out why "we" consistently used V12s the "right" way up, and the Luftwaffe consistently - so it seems - used inverted V12s. Are there advantages to inverted beyond the view from the cockpit - but then you need longer undercarriage; I'd have thought having a single sump is better, but OTOH do you get more reliable valve lubrication if it's all inverted? But what prevents oil pooling in the underside of the pistons besides their violent motion?

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Tsk-tsk, fat cat Softcat: Milk-slurping reseller taken to court

hugo tyson
FAIL

History repeating itself...

There was a time when "troubled Cambridge micro-maker" Acorn Computers couldn't get milk delivered because of unpaid invoices with every last one of the local newsagents and dairies. Because of idiot finance bods going "oh this little one doesn't matter"...

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Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign

hugo tyson

Re: Hmmm... @AC Might not even leak data

The leak may not even be data, it could be as small as a timing change from the spec-ex path taking longer to fault, or not, allowing the attacker to probe the kernel space for not/valid pages - so defeating to an extent the kernel memory-map randomisation? Worse might be a spec-ex branch on spec-read secret data which affects timing similarly, without directly exposing the data itself.

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Blade Runner 2049: Back to the Future – the movies that showed us what's to come

hugo tyson
FAIL

Video Conferencing

Star Trek has videoconferencing that actually works properly. Still beyond our grasp....

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I've arrived on Mars. Argggh, my back!

hugo tyson
WTF?

How much decrease in muscle mass?

The sentence in the article is a bit mangled, do you mean the muscle cross-sectional area decreased to about 80% of what it was originally, the range being 86% in the best case and 72% in the worst case?

Or if it decreased by 86%-72% does that mean only 14% to 28% remained (which seems terrifying)?

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GPS spoofing can put Yik Yak in a flap

hugo tyson
Unhappy

Hardly GPS spoofing

Hardly GPS spoofing is it? Just setting your location somewhere else. Fake location, fair enough.

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Turing, Hauser, Sinclair – haunt computing's Cambridge A-team stamping ground

hugo tyson

Details, details...

In Cambridge it's a Court not a Quad; Quads are from The Other Place ;-)

But yes it's a great photo, so of its time.

Re the pic on the steps of 4a Market Hill, L-R David Johnson-Davies ("DJD"), Hermann, Chris Curry, Roger (now Sophie) Wilson, Nick Toop, holding an Acorn Atom. 4a MH was never an ARM office; only Acorn.

The Turing Room in King's is the College Computer Room as I understand it; named after the great man. But I don't think there's any implication that he lived in that basement room, it's a cellar. As a Fellow he might well have lived in the rooms above, though.

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Great British Great Bake Off gets new judge

hugo tyson
Coat

Needs a proper critic

Why can't we have Brian Sewell? Aside from him being dead. And his bro George as sidekick to introduce some gritty realism.

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The field at the centre of the universe: Cambridge's outdoor pulsar pusher

hugo tyson
Thumb Up

Thanks!

Just: thanks for the article - great stuff, I enjoyed that day out enormously; thanks to Cambridge Wireless too of course.

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Milk IN the teapot: Innovation or abomination?

hugo tyson
Thumb Up

Perfect optimisation

We did exactly that - but in a proper teapot, I'll grant - at (later to be troubled) Cambridge micro-maker Acorn Computers in the early 1980s.

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Brit chip biz ARM legs it to Softbank for $32bn

hugo tyson
WTF?

Re: Apple will never own ARM (again)

I thought the licence those big players have ("foundry") lets them re-implement the hardware as they like, but absolutely not fork the instruction set and software interface generally (ISA, eg. cache behaviour) to make sure code portability can never be sacrificed. Intel IIRC learnt this when they acquired DEC and its Xscale designs, and tried to fiddle with the ISA, and found they couldn't because the ISA is copyrighted in some way separate from the IP licence.

WTF because this is a complete surprise. I could believe it's as simple as SB having a huge mound of cash and looking for the best possible investment, as ARM is starting to work in servers too, and the IoT bubble.

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DARPA's 'flying wing' drone inches closer to lift-off

hugo tyson
Happy

Mmmm.... contra rotating....

But not as sexy as a Fairey Gannet, eh?

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Model's horrific rape case may limit crucial online free speech law

hugo tyson

Re: law enforcement?

It's not clear from the report whether the "agencies" or indeed actual agencies had to be registered or vetted in any way. Is it?

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hugo tyson
Unhappy

Different law?

This does seem separate from the protection afforded to common-carrier-like websites in that law, in that this is abusive readers/consumers of the site, who cause no change to its state -- not abusive speech published via/though/on the site. Tricky.

It does suggest that reader accounts should strongly be vetted, in such cases, and contacts should be only through the site so that they are logged in an evidence-worthy fashion. Otherwise it's just like telling Facebook everything with entirely public access.

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Watch: SpaceX finally lands Falcon rocket on robo-barge in one piece

hugo tyson
Happy

Yay indeed!

I'll drink to that; wups, I was anyway!

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Regular Fast Radio Burst detected outside our galaxy

hugo tyson

Multipath?

...as it's not regular.

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$17 smartwatch sends something to random Chinese IP address

hugo tyson

It's the app that leaks, right?

But do you need the app to use the watch or is it just like the "drivers CD" you get with every little toy that nobody needs because they're actually standard USB devices? Put another way, if it's a proper BlueTooth device it'll use the standard BT profiles to be remote-control for the phone functions, and not need no steenkin' app.

Course it could just be checking for updates...

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Oh TechNation. Britain's got tech talent. Just not like this

hugo tyson
FAIL

Tool users vs tool makers

They're failing to distinguish people who use IT as a tool to run their business - ie. have a website and email and maybe an online shop - and those who actually make new IT/digital things. And the people who make websites for businesses, or set up their email, are somewhere in between, IMHO rather closer to users.

Like people who make TV ads or soap operas are not innovating in the photography business.

It's like classifying every business which acquired a shiny new landline in the 1920s and '30s as a telecoms business. (Might have the decades wrong but YKWIM)

It's like saying that B&Q is part of the steel industry because they sell spanners.

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'I bet Russian hackers weren't expecting their target to suck so epically hard as this'

hugo tyson
Mushroom

Unsigned....

So what's wrong with

for ( u = 100; u < 200; u-- ) { ... }

I think I have seen this as a fix! :-(

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Lights out! Newbie IT manager's dark basement trip

hugo tyson
FAIL

Re: Ah Diesel Generators

One job, the modal cause of genuine fire alarm evacuations was "the temperature is too high in the detached generator building" - following the regular testing... especially in summer.

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You've seen things people wouldn't believe – so tell us your programming horrors

hugo tyson
Coat

So much fun....

Once we shipped some embedded software as a relocatable binary to a customer. It needed to be started with some workspace memory. They were getting nowhere. So I went to Japan, and spent two days working out how the hell to debug/single-step in their useless environment, to find they had started it giving it the memory where the code was, as its own workspace. It ran just fine, initialising its memory, until it shot itself in the head by overwriting the code that was doing the initialising...

In PostScript, double-slash is a meaningful token, prefix to a name for immediate evaluation. It's used a lot in the bootstrap, itself written in PS, of a PostScript-compatible interpreter. Trivial example

/inc { 1 //add } def

For one reason or another, the bootstrap source was macro pre-processed. This was fine until the C-preprocessor - for it was he! - enabled C++ comments by default. Most of the bootstrap disappeared.

Re. sweary messages and customers: in the 1980s, at Acorn, I wrote tests for the very first ARM CPUs, even before we had silicon back - to check the various emulators, and to test in simulation the chip layout before tape-out, to test the chips when they came back. One said - or rather didn't, because it worked OK - "Shifter fucked!" in the error case. This was all lovely, and the same unit tests were still used 10-15 years later by ARM. They even shipped them to customers (making their own ARMs) as binaries. This was lovely too. Until one customer somehow managed to make chips whose shifter was not entirely correct...

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Intel admits Skylakes can ... ... ... freeze in the middle of work

hugo tyson
Mushroom

0xE40001

is that exponent in hex. Interesting. One might wonder if it's all exponents of the form 0xNN0001 (NN > 0)

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The Register's entirely serious New Year's resolutions for 2016

hugo tyson
Devil

Getting "across" the news

(you) "can get across a day's news quickly" - if you're dropping the sexism, you can use correct English and say "keep abreast of the day's news" without sniggering, rather than that revolting neologism. Or even just "catch up" ffs....

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PM wheels out snoop overseer minutes before latest snoops' charter bid lands

hugo tyson
Black Helicopters

What will they log?

So what will the govmt require ISPs to log? DNS lookups? So use 8.8.8.8 or 8.8.4.4 - or will they snoop on DNS request packets en passent for all? Or do they log what IP addresses you open connections to, which reverse-DNS gives domains? So something like Tor or other onion router gets round it. Just curious if anyone knows, if the detail has come out yet. Because it seems likely that a determined operative could circumvent any obvious logging....

Separately, I too worry that someone out of touch will be prone to assertions about what can be done which are not realistic, such as "well force them to decrypt it" given a noisy image + allegation that it contains a steganographic code, for example. Point is old media (paper letters, morse code) are either plaintext or definitely something cryptographic. Modern media/messaging can be perfectly valid gibberish and still be your pictures/music: you can't prove the positive "there is encrypted data here" nor the negative "this is just a picture, no encrypted data present". That's what could cause the traditional legal profession's assumptions problems.

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PC sales will rise again, predicts Intel, but tablets are toast

hugo tyson
FAIL

Intel-based tablets

Exactly, my first thought was: Intel got the market for Intel-based tablets wrong. They did; they're not so good, so people didn't buy many,

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Silicon Valley now 'illegal' in Europe: Why Schrems vs Facebook is such a biggie

hugo tyson
FAIL

Re: Let me count the ways...

I agree the email example is a very poor one: by sending an email to a person you give them the right to do whatever they like with it, stupid legalese boilerplate on the end notwithstanding. And email never has been private. Of course, the public's expectation might be different, but that doesn't make it so.

A better example, and easier to understand would be: you think you order a product from an EU business. Name, address, credit card, implicitly shopping habit. Turns out their servers are in the US. They just exported your personal data without your consent.

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Doctor Who storms back in fine form with Season 9 opener The Magician's Apprentice

hugo tyson
Holmes

Handmines

The "Handmines" is just a crap pun on landmines innit. Cute that they're like the hand-from-the-grave thing in every zombie movie, but with dalek (biological) eyes spliced in.

And my bet is it's the handmines that he's going to exterminate in the opener for Ep.2.

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Typewriters suck. Yet we're infinitely richer for those irritating machines

hugo tyson
WTF?

Re: <pendantry>

Pendantry? Should be bloody well hung...

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IWF shares 'hash list' with web giants to flush out child sex abuse images online

hugo tyson
Go

Re: Am I being a bit thick here

I think that if you change one bit, it is impossible that the signature/hash will not change. With a proper sig/hash/crypto, if you change any single bit of the input, an unpredictable (to an attacker) 50% of the bits in the hash will change (invert).

If you change 2 bits, same as changing 1 then another, 50% change, then some proportion p, whose mean is 1/2, of those change back and proportion 1-p of the others change: making on average a 50% change in all - repeat by changing another bit: so by recursion, any change in the input including complete replacement (whatever that means) changes, on average, half the bits in the output.

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RBS sticks it to customers once again as IT woes continue

hugo tyson

Re: Should be shutting down soon

I haven't had any problems with my banking in over 30 years either. With NatWest. Just FWIW. The last "major cock up" didn't affect everyone, and nor is this one. Put another way, every last company has some customers who have experienced a horror story, and who swear that after switching all was roses...

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Mitsubishi Outlander PHEV: The new common-as-muck hybrid

hugo tyson

Re: A lot I could live with...

I must say I think it's good that we are getting both kinds: those which flaunt design and are uniquely identifiable as EVs, for those who want that, and also the way to the mass market, making EVs *not* remarkable but commonplace, by making it just one variant of an ordinary car.

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hugo tyson
Go

"Charge it" button

Surely the button to force it to eat petrol to charge the battery is for when you are a few miles from entering a ZEV zone or some such, ie. London, and you forgot to use the "keep it full" button for the first part of the journey. Or when all the charging points at the services you planned to use are full, also on the edge of a ZEV zone?

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SpaceX Dragon crew capsule in 'CHUTE ABORT drama – don't panic, no one died

hugo tyson

The Shuttle was indeed intended to be its own escape capsule

http://en.wikipedia.org/wiki/Space_Shuttle_abort_modes details lots of cunning plans; but they all address a detected component failure - nothing's available to deal with an actual explosion or other gross mechanical failure.

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Boeing 787 software bug can shut down planes' generators IN FLIGHT

hugo tyson
Mushroom

Misplaced caution?

I agree it looks like a 100Hz ticker reaching 2^31 and going negative. But I think (without going off into comp.risks) there might be something else going on.

Problematic code can fail at overflow one of two ways: looping forever (very bad) or exiting prematurely (softer). It's not hard to get it right, of course, but if, say, the API changes (!) after you wrote your timer code or something like that it can end up wrong. So, for ultra-cautious safety-critical stuff, how do you make sure? You add asserts. Lots of asserts. Sounds like that's what we have here, as it goes into a fail-"safe" shutdown.

Problem is, if your code would do the soft failure - premature exit from the loop - then the assert makes it less reliable. Because what would otherwise be a single spurious shorter timeout, perhaps no worse than noise in whatever it is you're measuring/updating periodically, perhaps completely harmless, the assert failure turns into a complete shutdown.

In other words, assert - and thus shutdown - if you see insanity in your inputs, or detect an actual failure signal, for example. Asserting for anything less might help find bugs if you test it enough, but when deployed, you want something weaker, that logs an unexpected condition, but doesn't panic the system. IMHO.

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hugo tyson
Coat

Avro Vulcan

You're right, Vulcans weren't fly-by-wire at all; it's pushrods and levers, but the large force to move the control surfaces is electro-hydraulic: each PFC actuator is a self-contained unit taking 200V AC electric power in, to hydraulic pump, to hydraulic piston making a large force on the external hardware - but controlled by a mechanical lever input. The mixing of elevator and aileron signalling to the elevons, and the artificial feel is all (electric-powered) mechanical. Essentially it uses electric instead of hydraulic power to do all the power-assisting, but the control connections are very traditional linkages.

Not sure, but I think the batteries were only 28V for running other control systems, not enough to power the PFCs, enough to operate the RAT or AAPU to work around generator or bus failures.

So complete electrical failure left all the controls locked. Not good at all, especially for the 3 guys in the back. :-(

1
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Microsoft: It's TRUE, you'll get Android and iOS apps in WINDOWS

hugo tyson
Facepalm

Fair point

.... but Java was originally intended to be an ANDF, remember? How these pages were filled with mockery as managers insisted on Java for mainframe projects an other inappropriate targets because it was trendy!

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Health & Safety is the responsibility of Connor's long-suffering girlfriend

hugo tyson
FAIL

It's all about liability

We have to do stupid "how to sit on a chair" training. OK, it's supposed to be "how to set up your workstation" meaning monitor, mouse, keyboard. It's designed so that any moron can pass by picking the middle one of the answers. "Do you set your chair a) too low b) middle c) too high" but in pictures. It's designed to take a certain time by making you mouse over things to see popups for a certain time before you can press "next". The only thing it does is relieve the employer of liability for your bad back or RSI. It's utterly utterly pointless.

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Man asks internet for $1k for pebbles. INTERNET SAYS YES

hugo tyson
Joke

Gotta be nuts!

http://www.screwfix.com/p/hex-nuts-a2-stainless-steel-m20-pack-of-10/38163

There, much cheaper...

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