Beam, Fulcrum, Torque, Law of the Lever and Mechanical Advantage

Posted by PITHOCRATES - April 30th, 2014

Technology 101

(Originally published May 1st, 2013)

A Lever is a Rigid Beam on a Fulcrum

Archimedes said, “Give me a place to stand, and I shall move the Earth with it.”  At least we think he did.  Archimedes of Syracuse was a Greek genius.  Mathematician.  Physicist.  Engineer.  Inventor.  And astronomer.  One of many of the ancient Greeks who advanced modern civilization.  By using math and science.  He did a lot.  And explained why things worked the way they did using math.  Like the Law of the Lever.

In the days before the twist-off bottle cap we used bottle openers.  Because try as we might we could not pry a bottle cap off with our hands.  Most grown men just didn’t have the strength to do that.  But a child could open a bottle if that child used a bottle opener.  For that bottle opener is a lever.  Giving the child leverage.  The ability to use a little bit of force to do a lot of work.

A lever is a rigid beam on a fulcrum.  Like a seesaw.  A common playground fixture.  If two kids of equal weight are on either end of the seesaw and the fulcrum is in the center these kids can effortless push up and down.  But if a grown adult sits on one end and a child is on the other the weight of the adult will drop his side of the seesaw down.  Leaving the child up in the air on the other side.

As the Lever increases in Length the more it will Amplify the Input Force we Apply

Now that’s no fun.  Having the seesaw permanently tipped in one direction.  However, even two people of different weights can enjoy playing on the seesaw.  All they have to do is move the fulcrum towards the heavier person until the seesaw balances.  So that there is a short length of seesaw between the fulcrum and the heavy person.  And longer length of seesaw between the fulcrum and the lighter person.  This creates the same amount of torque on both side of the fulcrum.

Torque is the turning force created by a force acting about a fulcrum.  The force in this case is the weight of the people on the seesaw.  Which we calculate by multiplying their mass by the force of gravity.  With the force of gravity being constant the greater the mass the greater the weight.  This weight pressing down on the beam creates torque.   And the further away from the fulcrum the greater the turning force.  Such that a lighter weight at a greater distance from the fulcrum can balance a greater weight at a shorter distance from the fulcrum.  Allowing a child to play on a seesaw with someone of far greater mass.  Because the lever amplified the smaller force of the child.  Allowing the child to move a heavier weight.  To illustrate this consider the following table.

Lever

This is just a visual aid.  The numbers don’t represent anything.  It just shows a relationship between force and the length of the lever.  In this example we need 1000 units of force to move something.  If we use a lever that is 10 units from the fulcrum we need to apply 100 units of force.  If we have a lever that is 40 units from the fulcrum we only need to apply 25 units of force.  If we have a lever that is 80 units from the fulcrum we only need to apply 12.5 units of force.  As the lever increases in length the more it will amplify the input force we apply.  Which is why a child can open a bottle with a bottle opener.

A Wheelbarrel combines the Lever with the Wheel and Axle

A lever gives us mechanical advantage.  The amplification of a small input force into a larger output force.  Such as a hand-held bottle opener.  But what about the kind that used to be fastened to pop machines?  When you bought a glass bottle of pop out of a vending machine?  The fulcrum is the fixed bottle opener.  And the lever is the bottle.  A can opener was often on the other end of a bottle opener.  Instead of a grip to latch onto a bottle cap this end had a triangular knife.  When we lifted up on the lever it pressed down and pierced a hole in a can.

A wheelbarrel allows us to move heavy loads.  This device combines two simple machines.  A wheel and axle.  And a lever.  The wheel and axle is the fulcrum.  The lever runs from the fulcrum to the handles of the wheelbarrel.  We place the load on the lever just before the axle.  When we lift the far end of the lever we can tilt up the load and balance it over the axle.  The lever amplifies the force we apply.  And the wheel and axle reduce the friction between this load and the ground.  Allowing us to move a heavy load with little effort.

Today’s pop bottles have screw-top caps.  Some people still use a lever to help open them, though.  A pair of pliers.  We use the pliers because we don’t have the strength to grip the cap tight enough to twist it open.  The pliers are actually two levers connected together at the fulcrum.  The pliers amplify our hand strand-strength to get a very secure grip on the bottle cap.  While our hands compress the two levers together getting a firm grip on the cap we can then use our arm to apply a force on the handles of the pliers.  Providing a torque to turn the bottle cap.  Very simple machines that make everyday life easier.  Thanks to the knowledge Archimedes handed down to us.

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Bucket Brigade, Fire Engine, Sprinkler System, Sprinkler Head, Fire Pump, Jockey Pump, Wet-Pipe and Dry-Pipe

Posted by PITHOCRATES - April 23rd, 2014

Technology 101

(Originally published March 20th, 2013)

A Fire Engine can move Water Faster and Farther with an Internal Combustion Engine than with a Steam Engine

Some of our earliest firefighters were bucket brigades.  Where people would form lines between a fire and a water source.  Someone would dip a bucket into the water source.  And then pass it to the next person in line.  Who would then pass it to the next person in line.  And so on until the bucket reached the person at the other end of the line.  Who then poured the water on the fire.  Then the empty buckets would work their way the other way back towards the water source.  Buckets of water moved from the source of water to the fire.  While empty buckets moved from the fire to the water source.

This was state of the art firefighting at the time.  As long as there were enough people to form a line from the water source to the fire.  The people didn’t tire out before the fire did.  And the fire wasn’t so large that buckets of water couldn’t put it out.  But soon we developed the hand-operated pump on our first fire engines.  And the fire hose.  Then we just had to run a fire hose from the water source to the fire engine.  And a fire hose from the fire engine to the fire.  People could take turns hand pumping, producing a steady stream of water.  That someone could direct onto a fire.  These new firefighting crews could put out large fires in shorter times.  Fire companies appeared in cities with trained firefighters.  Providing safer cities.  A great improvement over the bucket brigade.  But not as good as what came next.

Men pulled the early fire engines.  Then horses replaced men.  But the big advancement was in the fire pump.  When steam power replaced hand power.  Allowing greater flows of water at higher pressures.  Allowing firefighters to attack a fire from a safer distance.  But steam had some drawbacks.  It took time to boil water into steam.  Steam engines needed boiler operators to carefully operate the boiler so it didn’t explode.  And being an external combustion engine there were a lot of moving parts in the open.  That could be dangerous to the firefighters.  And being exposed to the elements they needed constant oiling.  The internal combustion engine didn’t suffer any of these drawbacks.  The modern fire engine is safer.  Easier to operate.  More efficient.  And can move more water faster and farther.

A Jockey Pump in a Sprinkler System maintains the Water Pressure when there’s no Fire

But even the modern fire engine has one drawback.  We park them at firehouses.  While all our fires are not at firehouses.  So they have to drive to the fire.  Which they can do pretty quickly.  But that’s still time a fire can grow.  Causing more damage.  Become stronger.   And more difficult to put out.  Which is why we brought fire-fighting water into buildings.  To use on a fire even before the fire department arrives on the scene.  Buildings today have fire sprinkler systems.  Pipes filled with water covering every square inch of a building.  That will release their water through the various sprinkler heads attached to these pipes.

The sprinkler head is a marvel of low-tech.  It is basically a threaded fitting that screws into the water-filled pipe.  The sprinkler head has a hole in it.  A glass bulb with a liquid inside of it holds a plug in the hole.  Preventing the flow of water.  If there is a fire under this head the heat will cause the liquid in the glass bulb to expand.  Eventually shattering the glass bulb.  The water pressure inside the pipe will blow out the plug.  Allowing the water to flow out of the pipe.  As it does it hits a deflector, producing a spray pattern that will evenly cover the area underneath the head.  Only areas where there is a fire will break these glass bulbs.  So only the sprinklers over fires will discharge their water.  Preventing water damage in areas where there is no fire.

Some buildings can operate off of city water pressure.  But larger buildings, especially multistory buildings, need help to maintain the water pressure in the system.  These buildings have fire pumps.  A large pump that can maintain the pressure in the sprinkler lines even if all the sprinkler heads are discharging water.  And a smaller jockey pump.  Which maintains the pressure in the system when there is no fire.  If the pressure drops below a lower limit the jockey pump comes on.  When the pressure rises above a higher limit the jockey pump shuts down.  If there is a fire in the building the fire pump will run until it melts down.  Putting water on the fire as long as it can.

A Dry-Pipe Fire Sprinkler System in an Unheated Area is often attached to a Wet-Pipe System in a Heated Area

If water would greatly damage an area (such as a hardwood basketball court) they may add a valve on the pipe feeding the sprinkler piping over the floor.  Keeping the water out of the pipes over the expensive hardwood floor.  Smoke detectors in the ceiling will open the valve when they detect a fire.  Letting water flow into the sprinkler lines over the floor.  And out of any sprinkler head over a fire hot enough to have broken the glass bulb to release the plug.

Water damage is a real concern.  For it may be a better alternative to fire damage.  But water damage in absence of any fire can be costly.  Something many have seen working on a new building in a northern climate.  During the first freeze.   If there was missed insulation on an exterior wall.  Under-designed heating in an exterior glass-enclosed stairwell.  Or both in a glass-enclosed vestibule that juts outside of a heated building.  As temperatures fall cold air migrates around these sprinkler lines.  Freezing the water inside.  Causing them to burst.  And when they do it releases the water pressure behind these frozen sections.  Flooding these areas with water.  Causing a lot of damage.  Not to mention the damage to the fire sprinkler system.

Some unheated areas need a sprinkler system.  But these pipes can’t be a wet-pipe system.  Because if there was water in the pipes it would freeze.  Breaking the pipes.  So we use a dry-pipe system in unheated areas.  Which is often attached a wet-pipe system.  Such as a dry-pipe system in an exterior canopy attached to a heated building.  There is a valve between the interior wet-pipe system and the exterior dry-pipe system.  An air compressor will put air under pressure in the dry-pipe system.  This air pressure will hold the valve close to the wet-pipe system.  If there is a fire underneath the canopy the glass bulb in a sprinkler head will expand and break.  Releasing the air from the dry-pipe system.  Allowing the water pressure in the wet-pipe system to open the valve.  Flooding the dry-pipe system.  And flowing out of the sprinkler head over the fire.

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Short Circuits, Ground Faults and Ground Fault Circuit Interrupter

Posted by PITHOCRATES - April 9th, 2014

Technology 101

AC Power uses Reciprocating Currents to produce Rotating Electromagnetic Fields

There is a police crime lab television show that can solve a crime from a single fiber.  Many crime lab shows, actually.  Where they use high-tech science and music montages to solve many a crime.  Which is great if you DVR’d the shows as you can fast forward through them.  And save some time.  In one of these shows the writers goofed, though.  Because they didn’t understand the science behind the technology.

Someone murdered a construction worker by sabotaging a power cord.  By cutting off the grounding (or third) prong.  The fake crime scene person said this disabled the ground fault circuit interrupter (GFCI) device in the GFCI receptacle.  Leaving the user of the cord unprotected from ground faults.  So when said worker gripped the drill motor’s metallic case while standing in water and squeezed the trigger he got electrocuted.  And when the investigator saw that someone had cut off the grounding prong of the cord he said there was no way for the GFCI to work.  Which is, of course, wrong.  For the grounding prong has little to do with tripping the GFCI mechanism in a receptacle.

If you look at an electrical outlet you will see three holes.  Two vertical slots and one sort of round one.  Inside of these holes are pieces of metal that connect to wiring that runs back to the electric panel in your house.  One of the slots is the ‘hot’ circuit.  The other slot is the ‘neutral’ circuit.  And the third slot is the ‘ground’ circuit.  Now alternating current (AC) goes back and forth in the wiring.  It will come out of the hot and go into the neutral.  Then it will reverse course and come out of the neutral and go into the hot.  Think of a reciprocating engine where pistons go up and down to produce rotary motion.  AC current does the same to produce rotating electromagnetic fields in an electric motor.

The Current in our Electric Panels wants to Run to Ground

If the current can come out of both the hot and the neutral why aren’t both of these slotted holes hots?  Or both neutrals?  Good question.  The secondary winding on the pole-mounted transformer feeding your house has three wires coming from it.  The secondary is a very long wire wrapped many times around a core.  If you measure the voltage at both ends of this coil of wire you will get 240 volts.  They also attach a third wire to this coil of wire.  Right in the center of the coil.  So if you measure the voltage from this ‘center tap’ to one of the other two wires you will be measuring the voltage across half of the windings.  And get half of the voltage.  120 volts.

These are the three wires they bring into your house and terminate to your electric panel.  The center tap and the two wires coming off the ends of the secondary winding.  They attach each of the two ‘end wires’ to a hot bus bar in the panel.  And attach the center tap to the neutral bus.  They also connect the ground bus to the neutral bus.  A 1-pole circuit breaker attaches to one of the two hot bus bars.  Current travels along a wire attached to the breaker, runs through the house wiring, goes through the electrical load and back to the panel to the neutral bus.  So this back and forth current comes from the 120 voltage produced over half of the secondary coil of wire in the transformer.  Where as a 2-pole breaker attaches to both hot bus bars.  Current travels along a wire attached to one pole of the breaker, runs through the house wiring, through the electric load and back to the panel.  But instead of going to the neutral bus bar it goes to the other pole of the 2-pole breaker and to the other hot bus bar.  So this back and forth current comes from the 240 voltage produced across the whole secondary coil in the transformer.

Current wants to run to ground.  It’s why lightning hits trees.  Because trees are grounded.  The current in our electric panels wants to run to ground, too.  Which we only let it do after it does some work for us.  When we plug a cord into an electric outlet we are bringing the hot and neutral closer together.  Like when we plug in our refrigerator.   When the temperature falls a switch closes completing the circuit between hot and neutral through the compressor in the refrigerator.  So the current can run to ground.  Which is actually a back and forth motion through the conductors to create a rotating electromagnetic field in the compressor.  Which runs back and forth between one of the hot bus bars and the neutral bus bar in the panel.

Ground Faults don’t trip Circuit Breakers when finding an Alternate Path to Ground

When we stand on the ground we are grounded.  We are physically in contact with the ground.  We can lie on the ground and not get an electric shock.  Despite all current wanting to run to ground.  So if all current is running to ground why don’t we get a shock when we contact the ground?  Because we are at the same potential as the ground.  And no current flows between objects at the same potential (i.e., voltage).  This is the reason why we have a ground prong on our cords.  And why we install a bonding jumper between the neutral bus and the ground bus in our panels.  So that everything but the hot bus bars is at the same potential.  So no current flows through anything UNLESS that something is also connected to a wire running back to a hot bus in the panel.

Of course, if there is lightning outside we don’t want to be the tallest object out there.  For that lightning will find us to complete its path to ground.  Just as electricity will inside our house.  This is the purpose of the grounding prong on cords.  And why we ground all metallic components of things we plug into an electric outlet.  So if a hot wire comes loose inside of that thing and comes into contact with the metal case it will create a short circuit to ground for that current.  The current will be so great as it flows with no resistance that it will exceed the trip rating of the circuit breaker.  And open the breaker.  De-energizing everything in contact with that loose hot wire.  Eliminating an electric shock hazard.  For example, you could have a fluorescent light with a metal reflector in your basement.  It could have a loose hot wire that energizes the full metallic exterior of that light.  If you were working in the ceiling and had one hand on a cold water pipe when you came into contract with that light you would get a nasty electric shock.  But if it was grounded properly the breaker would trip before anyone could suffer an electric shock.

Ground faults are a different danger.  Because they don’t trip the circuit breaker in the panel.  Why?  Because it’s not a short circuit to ground.  But current taking a different path to ground.  That doesn’t end inside the electric panel.  For example, if you’re using a hair dryer in the bathroom you may come into contact with water and cold water piping.  Things that can conduct electricity to ground.  And if you are in contact with these alternate paths to ground some of that current in the hot wire will not equal the current in the neutral wire.  Because that back and forth current will be going in and out of the hot bus.  And in and out of a combination of the neutral bus and that alternate path to ground through you.  Electrocuting you.  But because of your body’s resistance the current flow through you will not exceed the breaker rating.  Allowing the current to keep flowing through you.  Perhaps even killing you.  This is why we have GFCI receptacles in our bathrooms, kitchens and anywhere else there may be an alternate path to ground.

So how does a GFCI work?  When current flows through a wire it creates an electromagnetic field around the wire.  If you’re looking into the wire as it runs away from you the field will be clockwise when the current is going away from you.  And counter clockwise when coming towards you.  In an AC circuit there are two conductors with current flow.  And at all times the currents are equal and run in opposite directions.  Cancelling those electromagnetic fields.  Unless there is a ground fault.  And if there is one the current in the neutral will decrease by the amount running to ground.  And the electromagnetic field in the neutral conductor will not cancel out the electromagnetic field in the hot conductor.  The GFCI will sense this and open the circuit.  Stopping all current flow.  Even if the ground prong was cut off.

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Binary Numbers and Computer Speed

Posted by PITHOCRATES - April 2nd, 2014

Technology 101

Computers are Good at Arithmetic thanks to Binary Numbers

Let’s do a fun little experiment.  Get a piece of paper and a pen or a pencil.  And then using long division divide 4,851 by 34.  Time yourself.  See how long it takes to complete this.  If the result is not a whole number take it to at least three places past the decimal point.  Okay?  Ready……..start.

Chances are the older you are the faster you did this.  Because once upon a time you had to do long division in school.  In that ancient era before calculators.  Younger people may have struggled with this.  Because the result is not a whole number.  Few probably could do this in their head.  Most probably had a lot of scribbling on that piece of paper before they could get 3 places past the decimal point.  The answer to three places past the decimal point, by the way, is 142.676.  Did you get it right?  And, if so, how long did it take?

Probably tens of seconds.  Or minutes.  A computer, on the other hand, could crunch that out faster than you could punch the buttons on a calculator.  Because one thing computers are good at is arithmetic.  Thanks to binary numbers.  The language of all computers.  1s and 0s to most of us.  But two different states to a computer.  That make information the computer can understand and process.  Fast.

A Computer can look at Long Streams of 1s and 0s and make Perfect Sense out of Them

The numbers we use in everyday life are from the decimal numeral system.  Or base ten.  For example, the number ‘4851’ contains four digits.  Where each digit can be one of 10 values (0, 1, 2, 3…9).   And then the ‘base’ part comes in.  We say base ten because each digit is a multiple of 10 to the power of n.  Where n=0, 1, 2, 3….  So 4851 is the sum of (4 X 103) + (8 X 102) + (5 X 101) + (1 X 100).  Or (4 X 1000) + (8 X 100) + (5 X 10) + (1 X 1).  Or 4000 + 800 + 50 + 1.  Which adds up to 4851.

But the decimal numeral system isn’t the only numeral system.  You can do this with any base number.  Such as 16.  What we call hexadecimal.  Which uses 16 distinct values (0, 1, 2, 3…9, A, B, C, D, E, and F).  So 4851 is the sum of (1 X 163) + (2 X 162) + (15 X 161) + (3 X 160).  Or (1 X 4096) + (2 X 256) + (15 X 16) + (3 X 1).  Or 4096 + 512 + 240 + 3.  Which adds up to 4851.  Or 12F3 in hexadecimal.  Where F=15.  So ‘4851’ requires four positions in decimal.  And four positions in hexadecimal.  Interesting.  But not very useful.  As 12F3 isn’t a number we can do much with in long division.  Or even on a calculator.

Let’s do this one more time.  And use 2 for the base.  What we call binary.  Which uses 2 distinct values (0 and 1).  So 4851 is the sum of (1 X 212) + (0 X 211) + (0 X 210) + (1 X 29) + (0 X 28) + (1 X 27) + (1 X 26) + (1 X 25) + (1 X 24) + (0 X 23) + (0 X 22) + (1 X 21) + (1 X 20).  Or (1 X 4096) + (0 X 2048) + (0 X 1024) + (1 X 512) + (0 X 256) + (1 X 128) + (1 X 64) + (1 X 32) + (1 X 16) + (0 X 8) + (0 X 4) + (1 X 2) + (1 X 1).  Or 4096 + 0 + 0 + 512 + 0 + 128 + 64 + 32 + 16 + 0 + 0 + 2 + 1.  Which adds up to 4851.  Or 1001011110011 in binary.  Which is gibberish to most humans.  And a little too cumbersome for long division.  Unless you’re a computer.  They love binary numbers.  And can look at long streams of these 1s and 0s and make perfect sense out of them.

A Computer can divide two Numbers in a few One-Billionths of a Second

A computer doesn’t see 1s and 0s.  They see two different states.  A high voltage and a low voltage.  An open switch and a closed switch.  An on and off.  Because of this machines that use binary numbers can be extremely simple.  Computers process bits of information.  Where each bit can be only one of two things (1 or 0, high or low, open or closed, on or off, etc.).  Greatly simplifying the electronic hardware that holds these bits.  If computers processed decimal numbers, however, just imagine the complexity that would require.

If working with decimal numbers a computer would need to work with, say, 10 different voltage levels.  Requiring the ability to produce 10 discrete voltage levels.  And the ability to detect 10 different voltage levels.  Greatly increasing the circuitry for each digit.  Requiring far more power consumption.  And producing far more damaging heat that requires more cooling capacity.  As well as adding more circuitry that can break down.  So keeping computers simple makes them cost less and more reliable.  And if each bit requires less circuitry you can add a lot more bits when using binary numbers than you can when using decimal numbers.  Allowing bigger and more powerful number crunching ability.

Computers load and process data in bytes.  Where a byte has 8 bits.  Which makes hexadecimal so useful.  If you have 2 bytes of data you can break it down into 4 groups of 4 bits.  Or nibbles.  Each nibble is a 4-bit binary number that can be easily converted into a single hexadecimal number.  In our example the binary number 0001 0010 1111 0011 easily converts to 12F3 where the first nibble (0001) converts to hexadecimal 1.  The second nibble (0010) converts to hexadecimal 2.  The third nibble (1111) converts to hexadecimal F.  And the fourth nibble (0011) converts to hexadecimal 3.  Making the man-machine interface a lot simpler.  And making our number crunching easier.

The simplest binary arithmetic operation is addition.  And it happens virtually instantaneously at the bit level.  We call the electronics that make this happen logical gates.  A typical logical gate has two inputs.  Each input can be one of two states (high voltage or low voltage, etc.).  Each possible combination of inputs produces a unique output (high voltage or low voltage, etc.).  If you change one of the inputs the output changes.  Computers have vast arrays of these logical gates that can process many bytes of data at a time.  All you need is a ‘pulsing’ clock to sequentially apply these inputs.  With the outputs providing an input for the next logical operation on the next pulse of the clock.

The faster the clock speed the faster the computer can crunch numbers.  We once measured clock speeds in megahertz (1 megahertz is one million pulses per second).  Now the faster CPUs are in gigahertz (1 gigahertz is 1 billion pulses per second).  Because of this incredible speed a computer can divide two numbers to many places past the decimal point in a few one-billionths of a second.  And be correct.  While it takes us tens of seconds.  Or even minutes.  And our answer could very well be wrong.

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The Doppler Effect and Malaysian Flight 370

Posted by PITHOCRATES - March 26th, 2014

Technology 101

A Swan Pushes Waves Together in front of it and Pulls Waves Apart behind it as it Paddles across Water

Throw a stone in the water and what do you see?  Little circular ripples in the water moving away from and centered on where the stone broke the surface of the water.  These are waves.  Energy.  They are more intense the closer they are to the point of disturbance.  And become less intense the further they are from the point of disturbance.  So you’ll see larger circular ripples in the water closer to where the stone hit the water.  And smaller circular ripples at increasing radii from the point of impact.

You’ll see these little circular waves, too, when something else disturbs the surface of the water.  Like a swan.  Or a duck.  As they paddle their feet they move forward in the water.  Pushing the water out ahead them.  If you look closely you’ll see ripples bunched up in front of them.  And ripples spaced further apart behind them.  This is because of their movement towards the previous ripple.

These waves ripple through the water at the same speed (assuming the swan or duck is paddling at a constant speed).  So each ripple will travel the same distance at the same speed from the paddling bird.  But as the bird moves forward each subsequent wave in that direction is starting its journey at a point further along in that direction.  So one wave may have gotten to a point (let’s call it Point A) in the water 3 inches ahead of where the bird created it.  Since creating that wave the bird continued to paddle.  And created another wave.  This one created only 2 inches from Point A.  And then the bird created another wave at only 1 inch from Point A.  So subsequent waves are ‘catching up’ to previous waves.  Thus bunching the waves up in front of the bird.  While the bird is pushing these waves closer together the bird is traveling away from the waves behind it.  Stretching those waves further apart from each other.

A Guitar makes Sound by Vibrating the Soundboard in the Body of the Guitar

If you’ve ever played a guitar or watched someone play the guitar you’ve probably noticed how the sound changes depending on where the player fingers the string on the fingerboard (or fretboard).  If the player presses down on the string closer to the body of the guitar the note sounds higher.  If the player presses down on the string further away from the body of the guitar the note sounds lower.  Why?  Frequency.

A guitar makes sound by vibrating the soundboard in the body of the guitar.  The faster it vibrates the higher pitch the sound.  The slower it vibrates the lower pitch the sound.  The string vibrates back and forth a number of times each second.  The more it moves back and forth in one second the higher the frequency and the higher the pitch.  The fewer times it does the lower the frequency and the lower the pitch.  Thinner strings vibrate faster than thicker strings.  Shorter strings vibrate faster than longer strings.  So a typical guitar has 6 strings of various thickness stretched from the soundboard across the fingerboard.

The vibrating soundboard creates sound waves that move through the air.  Similar to a rock breaking the surface of the water.  As a guitar player fingers different notes on the fingerboard the soundboard vibrates at different frequencies.  Making music.  If you’re attending a small concert where a soloist is playing, say, Spanish Dance No. 2: Oriental by Enrique Granados you would hear the same beautiful music wherever you were sitting in the room.  The sound waves would be radiating throughout the room like the ripples created when a rock breaks the surface of the water.  However, if the soloist was moving like a swan through the water it would be a different story.

Using the Doppler Effect they determined Malaysian Airlines Flight 370 traveled the Southern Route

Ever listen to the sounds of cars and trucks traveling down a highway?  Maybe while visiting your aunt and uncle who live on a highway out in the country?  Did you notice that they had a higher-pitched sound when they approached you than when after they had passed you by?  The next time something noisy passes you by listen.  Especially if they’re blowing their horn.  It’ll go from a higher-pitched sound to a lower-pitched sound just as it passes you.  Why?  Think of the waves a swan makes gliding through the water.  Bunching waves closer together in front of it.  And stretching them further apart behind it.  The same thing happens with sound waves.  Austrian physicist Christian Doppler noted this in 1842.  Something we now call the Doppler Effect.

If a train is travelling down the track while blowing its horn it sounds the same aboard the train from the moment the engineer starts blowing it until he or she stops.  Just as the sound of a soloist playing Spanish Dance No. 2: Oriental sounds the same wherever you are in the room.  Because the distance between the source of the sound and the listener of the sound does not change.  But if you were standing stationary near the railroad track as the train traveled past you the frequency of the horn changes.  Because as it is approaching you it is pushing sound waves closer together.  Creating a higher frequency (or a higher-pitched sound).  As the train passes it is stretching those sound waves further apart.  Creating a lower frequency (or a lower-pitched sound).  This is the Doppler Effect.

When Malaysian Airlines Flight 370 shut off its transponder and ACARS (Aircraft Communications Addressing and Reporting System) stopped broadcasting the plane vanished.  But a satellite communicating with the airplane still ‘pinged’ the aircraft every hour of its remaining flight time.  And electronic handshake.  The satellite says, “Are you still there?”  And the plane responds, “Yes I am.”  No data was transmitted.  Only a sent and received signal.  Just a pulse of a constant frequency.  A ping.  But from those pings they could measure the time it took to send and receive those pings.  Which they could calculate distances between the satellite and the plane from.  Giving us the northern and southern possible routes as it traveled in an arc around the satellite.  But which way it went on that arc was a mystery.  Until they analyzed the frequencies of those pings.  And they detected a slight change in the frequencies.  Using the Doppler Effect they determined which side of the plane was bunching up the sound waves and what side of it was stretching them out.  And concluded the plane was traveling on the southern route.  Which is why all search efforts are now in the south Indian Ocean southeast from Australia.  Because, according to Christian Doppler, that’s the direction the plane flew.

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On the Flightdeck during Aviation Disasters

Posted by PITHOCRATES - March 19th, 2014

Technology 101

USAir Flight 427 on Approach to Pittsburgh flew through Wake Vortex and Lost Control

Malaysian Airlines Flight 370 search is still ongoing.  We’re seemingly no closer to understanding what happened than before.  There has been a lot of speculation.  And rebuttals to that speculation.  With many people saying things like why didn’t the crew radio?  Why didn’t they report a problem?  While others are saying that it is proof for their speculative theory.  That they were either under duress, had no time or were in on it and, therefore, went silent.  So what is it like on the flightdeck when something happens to an aircraft?  Well, because of past CVR (cockpit voice recorder) transcripts from previous accidents, we can get an idea.

On September 8, 1994, USAir Flight 427 flew into the wake vortex (little tornados trailing from a large plane’s wingtip) of a Delta Airlines Boeing 727 ahead of it.  This sideways tornado disrupted the airflow over the control surfaces of the USAir 737.  Disrupting it from level flight, causing it to roll left.  The autopilot tried to correct the roll as the 737 passed through the wake vortex core.  Causing more disruption of the airflow over the control surfaces.  The first officer then tried to stabilize the plane.  Control of the aircraft continued to deteriorate.  We pick up the CVR transcript just before this event (see 8 September 1994 – USAir 427).  CAUTION: The following recounts the final moments of Flight 427 and some may find it disturbing.

CAM-1 = Captain
CAM-2 = First Officer
CAM-3 = Cockpit Area Mike (cabin sounds and flight attendants)
RDO-1 = Radio Communications (Captain)
APP: Pittsburgh Approach

APP: USAir 427, turn left heading one zero zero. Traffic will be one to two o’clock, six miles, northbound Jetstream climbing out of thirty-three for five thousand.
RDO-1: We’re looking for the traffic, turning to one zero zero, USAir 427.
CAM-3: [Sound in engines increasing rpms]
CAM-2: Oh, yeah. I see the Jetstream.
CAM-1: Sheez…
CAM-2: zuh?
CAM-3: [Sound of thump; sound like ‘clickety-click’; again the thumping sound, but quieter than before]
CAM-1: Whoa … hang on.
CAM-3: [Sound of increasing rpms in engines; sound of clickety-click; sound of trim wheel turning at autopilot trim speed; sound similar to pilot grunting; sound of wailing horn similar to autopilot disconnect warning]
CAM-1: Hang on.
CAM-2: Oh, Shit.
CAM-1: Hang on. What the hell is this?
CAM-3: [Sound of stick shaker; sound of altitude alert]
CAM-3: Traffic. Traffic.
CAM-1: What the…
CAM-2: Oh…
CAM-1: Oh God, Oh God…
APP: USAir…
RDO-1: 427, emergency!
CAM-2: [Sound of scream]
CAM-1: Pull…
CAM-2: Oh…
CAM-1: Pull… pull…
CAM-2: God…
CAM-1: [Sound of screaming]
CAM-2: No… END OF TAPE.

At 19:03:01 in the flight there was a full left rudder deflection.  The plane yawed (twisted like a weathervane) to the left.  A second later it rolled 30 degrees left.  This caused the aircraft to pitch down.  Where it continued to roll.  The plane rolled upside down and pitched further nose-down.  The pilots never recovered.  The plane flew nearly straight into the ground at 261kts.  The crash investigated focused on the rudder.  Boeing redesigned it.  Pilots since have received more training on rudder inputs.  And flight data recorders now record additional rudder data.  This incident shows how fast a plane can go from normal flight to a crash.  The captain had time to radio one warning.  But within seconds from the beginning of the event the plane crashed.  Illustrating how little time pilots have to identify problems and correct them.

An In-Flight Deployment of a Thrust Reverser breaks up Lauda Air Flight 004

A plane wants to fly.  It is inherently stable.  As long as enough air flows over its wings.  Jet engines provide thrust that push an airplane’s wings through the air.  The curved surfaces of the wings interacting with the air passing over it creates lift.  As long as a plane’s jet engines push the wing through the air a plane will fly.  On May 26, 1991, something happened to Lauda Air Flight 004 to disrupt the smooth flow of air over the Boeing 767’s wings.  Something that isn’t supposed to happen during flight.  But only when a plane lands.  Reverse thrust.  As a plane lands the pilot reverses the thrust on the jet engines to slow the airplane.  Unfortunately for Flight 004, one of its jet engines deployed its thrust reverser while the plane was at about 31,000 feet.  We pick up the CVR transcript just as they receive a warning indication that the reverse thruster could deploy (see 26 May 1991 – Lauda 004).  CAUTION: The following recounts the final moments of Flight 004 and some may find it disturbing.

23.21:21 – [Warning light indicated]

23.21:21 FO: Shit.

23.21:24 CA: That keeps, that’s come on.

23.22:28 FO: So we passed transition altitude one-zero-one-three

23.22:30 CA: OK.

23.23:57 CA: What’s it say in there about that, just ah…

23.24:00 FO: (reading from quick reference handbook) Additional system failures may cause in-flight deployment. Expect normal reverse operation after landing.

23.24:11 CA: OK.

23.24:12 CA: Just, ah, let’s see.

23.24:36 CA: OK.

23.25:19 FO: Shall I ask the ground staff?

23.25:22 CA: What’s that?

23.25:23 FO: Shall I ask the technical men?

23.25:26 CA: Ah, you can tell ’em it, just it’s, it’s, it’s, just ah, no, ah, it’s probably ah wa… ah moisture or something ’cause it’s not just, oh, it’s coming on and off.

23.25:39 FO: Yeah.

23.25:40 CA: But, ah, you know it’s a … it doesn’t really, it’s just an advisory thing, I don’t ah …

23.25:55 CA: Could be some moisture in there or somethin’.

23.26:03 FO: Think you need a little bit of rudder trim to the left.

23.26:06 CA: What’s that?

23.26:08 FO: You need a little bit of rudder trim to the left.

23.26:10 CA: OK.

23.26:12 CA: OK.

23.26:50 FO: (starts adding up figures in German)

23.30:09 FO: (stops adding figures)

23.30:37 FO: Ah, reverser’s deployed.

23.30:39 – [sound of snap]

23.30:41 CA: Jesus Christ!

23.30:44 – [sound of four caution tones]

23.30:47 – [sound of siren warning starts]

23.30:48 – [sound of siren warning stops]

23.30:52 – [sound of siren warning starts and continues until the recording ends]

23.30:53 CA: Here, wait a minute!

23.30:58 CA: Damn it!

23.31:05 – [sound of bang]

[End of Recording]

The 767 Emergency/Malfunction Checklist stated that upon receiving the warning indicator ADDITIONAL system faults MAY cause an in-flight deployment of the thrust reverser.  But that one warning indication was NOT expected to cause any problem with the thrust reversers in stopping the plane after landing.  At that point it was not an emergency.  So they radioed no emergency.  About 10 minutes later the thrust reverser on the left engine deployed in flight.  When it did the left engine pulled the left wing back as the right engine pushed the right wing forward.  Disrupting the airflow over the left wing.  Causing it to stall.  And the twisting force around the yaw axis created such great stresses on the airframe that the aircraft broke up in the air.  The event happened so fast from thrust reverser deployment to the crash (less than 30 seconds) the crew had no time to radio an emergency before crashing.

Fire in the Cargo Hold brought down ValuJet Flight 592

One of the most dangerous things in aviation is fire.  Fire can fill the plane with smoke.  It can incapacitate the crew.  It can burn through electric wiring.  It can burn through control cables.  And it can burn through structural components.  A plane flying at altitude must land immediately on the detection of fire/smoke.  Because they can’t pull over and get out of the plane.  They have to get the plane on the ground.  And the longer it takes to do that the more damage the fire can do.  On May 11, 1996, ValuJet Flight 592 took off from Miami International Airport.  Shortly into the flight they detected smoke inside the McDonnell Douglas DC-9.  We pick up the CVR transcript just before they detected fire aboard (see 11 May 1996 – ValuJet 591).  CAUTION: The following recounts the final moments of Flight 592 and some may find it disturbing.

CAM — Cockpit area microphone voice or sound source
RDO — Radio transmissions from Critter 592
ALL — Sound source heard on all channels
INT — Transmissions over aircraft interphone system
Tower — Radio transmission from Miami tower or approach
UNK — Radio transmission received from unidentified source
PA — Transmission made over aircraft public address system
-1 — Voice identified as Pilot-in-Command (PIC)
-2 — Voice identified as Co-Pilot
-3 — Voice identified as senior female flight attendant
-? — Voice unidentified
* — Unintelligible word
@ — Non pertinent word
# — Expletive
% — Break in continuity
( ) — Questionable insertion
[ ] — Editorial insertion
… — Pause

14:09:36 PA-2 flight attendants, departure check please.

14:09:44 CAM-1 we’re *** turbulence

14:09:02 CAM [sound of click]

14:10:03 CAM [sound of chirp heard on cockpit area microphone channel with simultaneous beep on public address/interphone channel]

14:10:07 CAM-1 what was that?

14:10:08 CAM-2 I don’t know.

14:10:12 CAM-1 *** (’bout to lose a bus?)

14:10:15 CAM-1 we got some electrical problem.

14:10:17 CAM-2 yeah.

14:10:18 CAM-2 that battery charger’s kickin’ in. ooh, we gotta.

14:10:20 CAM-1 we’re losing everything.

14:10:21 Tower Critter five-nine-two, contact Miami center on one-thirty-two-forty-five, so long.

14:10:22 CAM-1 we need, we need to go back to Miami.

14:10:23 CAM [sounds of shouting from passenger cabin]

14:10:25 CAM-? fire, fire, fire, fire [from female voices in cabin]

14:10:27 CAM-? we’re on fire, we’re on fire. [from male voice]

14:10:28 CAM [sound of tone similar to landing gear warning horn for three seconds]

14:10:29 Tower Critter five-ninety-two contact Miami center, one-thirty-two-forty-five.

14:10:30 CAM-1 ** to Miami.

14:10:32 RDO-2 Uh, five-ninety-two needs immediate return to Miami.

14:10:35 Tower Critter five-ninety-two, uh, roger, turn left heading two-seven-zero.  Descend and maintain seven-thousand.

14:10:36 CAM [sounds of shouting from passenger cabin subsides]

14:10:39 RDO-2 Two-seven-zero, seven-thousand, five-ninety-two.

14:10:41 Tower What kind of problem are you havin’?

14:10:42 CAM [sound of horn]

14:10:44 CAM-1 fire

14:10:46 RDO-2 Uh, smoke in the cockp … smoke in the cabin.

14:10:47 Tower Roger.

14:10:49 CAM-1 what altitude?

14:10:49 CAM-2 seven thousand.

14:10:52 CAM [sound similar to cockpit door moving]

14:10:57 CAM [sound of six chimes similar to cabin service interphone]

14:10:58 CAM-3 OK, we need oxygen, we can’t get oxygen back here.

14:11:00 INT [sound similar to microphone being keyed only on Interphone channel]

14:11:02 CAM-3 *ba*, is there a way we could test them? [sound of clearing her voice]

14:11:07 Tower Critter five-ninety-two, when able to turn left heading two-five-zero.  Descend and maintain five-thousand.

14:11:08 CAM [sound of chimes similar to cabin service interphone]

14:11:10 CAM [sounds of shouting from passenger cabin]

14:11:11 RDO-2 Two-five-zero seven-thousand.

14:11:12 CAM-3 completely on fire.

14:11:14 CAM [sounds of shouting from passenger cabin subsides]

14:11:19 CAM-2 outta nine.

14:11:19 CAM [sound of intermittant horn]

14:11:21 CAM [sound similar to loud rushing air]

14:11:38 CAM-2 Critter five-ninety-two, we need the, uh, closest airport available …

14:11:42 Tower Critter five-ninety-two, they’re going to be standing by for you. You can plan runway one two to dolpin now.

14:11:45 one minute and twelve second interruption in CVR recording]

14:11:46 RDO-? Need radar vectors.

14:11:49 Tower critter five ninety two turn left heading one four zero 14:11:52

RDO-? one four zero

14:12:57 CAM [sound of tone similar to power interruption to CVR]

14:12:57 CAM [sound similar to loud rushing air]

14:12:57 ALL [sound of repeating tones similar to CVR self test signal start and continue]

14:12:58 Tower critter five ninety two contact miami approach on corrections no you you just keep my frequency

14:13:11 CAM [interruption of unknown duration in CVR recording]

14:13:15 CAM [sounds of repeating tones similar to recorder self-test signal starts and continues, rushing air.]

14:13:18 Tower critter five ninety two you can uh turn left heading one zero zero and join the runway one two localizer at miami

14:13:25: End of CVR recording.

14:13:27 Tower critter five ninety two descend and maintain three thousand

14:13:43 Tower critter five ninety two opa locka airports aout ah twelve o’clock at fifteen miles

[End of Recording]

The cargo hold of this DC-9 was airtight.  This was its fire protection.  Because any fire would quickly consume any oxygen in the hold and burn itself out.  But also loaded in Flight 592’s hold were some oxygen generators.  The things that produce oxygen for passengers to breathe through masks that fall down during a loss of pressurization.  These produce oxygen through a chemical reaction that produces an enormous amount of heat.  These were hazardous equipment that were forbidden to be transported on the DC-9.  Some confusion in labeling led some to believe they were ’empty’ canisters when they were actually ‘expired’.  The crash investigation concluded that one of these were jostled on the ground and activated.  It produced an oxygen rich environment in the cargo hold.  And enough heat to start a smoldering fire.  Which soon turned into a raging inferno that burned through the cabin floor.  And through the flightdeck floor.  Either burning through all flight controls.  Or incapacitating the crew.  Sending the plane into a nose dive into the everglades in less than 4 minutes from the first sign of trouble.

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Aviation Incidents and Accidents

Posted by PITHOCRATES - March 12th, 2014

Technology 101

The Pilots of Aloha Airlines Flight 243 landed Safely after Fatigue Cracks caused Part of the Cabin to Disintegrate

The de Havilland Company introduced the jet airliner to the world.  The Comet.  A 4-engine jet airliner with a pressurized cabin that could carry 36 passengers.  It could fly at 40,000 feet at speeds close to 500 mph.  Just blowing the piston-engine competition away.  Until, that is, they started breaking up in flight.  A consequence of pressuring the cabin.  The inflating and deflating of the metal cabin fatiguing the metal of the cabin.  Until fatigue cracks appeared at stress points.  Cracks that extended from the cycles of pressurizing and depressurizing the cabin.  Until the cracks extended so much that the pressure inside the cabin blew through the cracks, disintegrating the plane in flight.

Japan is a nation of islands.  Connecting these islands together are airplanes.  They use jumbo jets like buses and commuter trains.  Packing them with 500+ passengers for short hops between the islands.  Putting far more pressurization cycles on these planes than typical long-haul 747 routes.  On August 12, 1985, Japan Airlines Flight 123 left Haneda Airport, Tokyo, for a routine flight to Osaka.  Shortly after takeoff as the cabin pressurized the rear pressure bulkhead failed (due to an improper repair splice of the pressure plate using a single row of rivets instead of a double row following a tail strike that damaged it).  The rapid force of the depressurization blew out through the tail section of the aircraft.  Causing great damage of the control surfaces.  And severing the lines in all four hydraulic systems.  Leaving the plane uncontrollable.  The crew switched their transponder to the emergency code 7700 and called in to declare an emergency.  But they could do little to save the plane.  The plane flew erratically and lost altitude until it crashed into a mountain.  Killing all but 4 of the 524 aboard.

Hawaii is similar to Japan.  They both have islands they interconnect with airplanes.  Putting a lot of pressurization cycles on these planes.  On April 28, 1988, Aloha Airlines Flight 243 left Hilo Airport bound for Honolulu.  Just as the Boeing 737 leveled off at 24,000 feet there was a loud explosive sound and a loud surge of air.  The pilots were thrown back in their seats in a violent and rapid decompression.  The flightdeck door was sucked away.  Looking behind them they could see the cabin ceiling in first class was no longer there (due to fatigue cracks radiating out from rivets that caused pressurized air to blow out, taking the ceiling and walls of the first class cabin with it).  They could see only blue sky.  They put on their oxygen masks and began an emergency descent.  The first officer switched the transponder to emergency code 7700.  The roar of air was so loud the pilots could barely hear each other as they shouted to each other or used the radio.  The flight controls were operable but not normal.  They even lost one of their two engines.  But the flight crew landed safely.  With the loss of only one life.  A flight attendant that was sucked out of the aircraft during the explosive decompression.

The Fact that 185 People survived the United Airlines 232 Crash is a Testament to the Extraordinary Skill of those Pilots

On June 12, 1972, American Airlines Flight 96 left Detroit Metropolitan Airport for Buffalo after arriving from Los Angeles.  The McDonnell Douglas DC-10 took on new living passengers in Detroit.  As well as one deceased passenger in a coffin.  Which was loaded in the rear cargo hold.  As the DC-10 approached 12,000 feet there was a loud explosive sound.  Then the flightdeck door was sucked away and the pilots were thrown back in their seats in an explosive decompression.  The aft cargo door (improperly latched—its design was later revised to prevent improperly latching in the future) had blown out as the cargo hold pressurized.  As it did the rapid decompression collapsed the floor above.  Into the control cabling.  The rudder was slammed fully left.  All three throttle levels slammed closed.  The elevator control was greatly inhibited.  The plane lost a lot of its flight controls but the pilots were able to bring the plane back to Detroit.  Using asymmetric thrust of the two wing-mounted engines and ailerons to compensate for the deflected rudder.  And both pilots pulling back hard on the yoke to move the elevator.  Due to the damage the approach was fast and low.  When they landed they applied reverse thrust to slow down the fast aircraft.  At that speed, though, the deflected rudder pulled them off the runway towards the terminal buildings.  By reapplying asymmetric thrust the pilot was able to straighten the aircraft out on the grass.  As the speed declined the rudder force decreased and the pilot was able to steer the plane back on the runway.  There was no loss of life.

On July 19, 1989, United Airlines Flight 232 took off from Stapleton International Airport in Denver for Chicago.  About an hour into the flight there was a loud bang from the rear of the plane.  The aircraft shuddered.  The instruments showed that the tail-mounted engine had failed.  As the crew responded to that the second officer saw something more alarming.  Hydraulic pressure and fluid quantity in the three hydraulic systems were falling (a fan disc in the tail-mounted engine disintegrating and exploded like shrapnel from an undetected manufacturing flaw, taking out the 3 hydraulic systems).  The flight crew soon discovered that they had lost all control of the airplane.  The plane was making a slight turn when the engine failed.  And the flight control surfaces were locked in that position.  The captain reduced power on the left engine to stop the plane from turning.  The two remaining engines became the only means of control they had.  Another DC-10 pilot traveling as a passenger came forward and offered his assistance.  He knelt on the floor behind the throttle levels and adjusted them continuously to regain control of the plane.  He tried to dampen the rising and falling of the plane (moving like a ship rolling on the ocean).  As well as turn the aircraft onto a course that would take them to an emergency landing at Sioux City.  They almost made it.  Unfortunately that rolling motion tipped the left wing down just before touchdown.  It struck the ground.  And caused the plane to roll and crash.  Killing 111 of the 296 aboard.  It was a remarkable feat of flying, though.  Which couldn’t be duplicated in the simulator given the same system failures.  As flight control by engine thrust alone cannot provide reliable flight control.  The fact that 185 people survived this crash is a testament to the extraordinary skill of those pilots.

On July 17, 1996, TWA Flight 800 took off from JFK Airport bound for Rome.  About 12 minutes into the flight the crew acknowledged air traffic control (ATC) instructions to climb to 15,000 feet.  It was the last anyone heard from TWA 800.  About 38 seconds later another airplane in the sky reported seeing an explosion and a fire ball falling into the water.  About where TWA 800 was.  ATC then tried to contact TWA 800.  “TWA800, Center…TWA eight zero zero, if you can hear Center, ident…TWA800, Center…TWA800, if you can hear Center, ident…TWA800, Center.”  There was no response.  The plane was there one minute and gone the next.  There was no distress call.  Nothing.  The crash investigation determined that an air-fuel mixture in the center fuel tank was heated by air conditioner units mounted below the tank, creating a high-pressure, explosive vapor in the tank that was ignited by an electrical spark.  The explosion broke the plane apart in flight killing all 230 aboard.

The Greatest Danger in Flying Today may be Pilots Trusting their Computers more than their Piloting Skills

On December 29, 1972, Eastern Airlines Flight 401 left JFK bound for Miami.  Flight 401 was a brand new Lockheed L-1011 TriStar.  One of the new wide-body jets to enter service along with the Boeing 747 and the McDonnell Douglas DC-10.  Not only was it big but it had the latest in automatic flight control systems.  As Flight 401 turned on final approach they lowered their landing gear.  When the three landing gear are down and locked for landing there are three green indicating lights displayed on the flightdeck on the first officer’s side.  On this night there were only 2 green lights.  Indicating that the nose wheel was not down.  So they contacted ATC with their problem and proceeded to circle the airport until they resolved the problem.  ATC told them to climb to 2000 feet.  The 1st officer flew the aircraft on the course around the airport.  The captain then tried to reach the indicating light to see if it was a burnt out lamp.  Then the flight engineer got involved.  As did the first officer after turning on the automatic altitude hold control.  Then another person on the flightdeck joined in.  That indicating lamp got everyone’s full attention.  Unable to determine if the lamp was burnt out the pilot instructed the flight engineer to climb down into the avionics bay below the flightdeck to visually confirm the nose gear was down and locked.  He reported that he couldn’t see it.  So the other guy on the flightdeck joined him.  During all of this someone bumped the yoke with enough pressure to release the automatic altitude hold but no one noticed.  The airplane began a gradual descent.  When they approached the ground a ground proximity warming went off and they checked their altitude.  Their altimeters didn’t agree with the autopilot setting.  Just as they were asking each other what was going on the aircraft crashed into the everglades.  Killing 101 of the 176 on board.

On June 1, 2009, Air France Flight 447 was en route from Rio de Janeiro to Paris.  This was a fly-by-wire Airbus A330 aircraft.  With side stick controllers (i.e., joysticks) instead of the traditional wheel and yoke controls.  The A330 had sophisticated automatic flight controls.  They practically flew the plane by themselves.  With pilots spending more of their time monitoring and inputting inputs to these systems than flying.  Flight 447 flew into some turbulence.  The autopilot disengaged.  The aircraft began to roll from the turbulence.  The pilot tried to null these out but over compensated.  At the same time he pitched the nose up abruptly, slowing the airplane and causing a stall warning as the excessive angle of attack slowed the plane from 274 knots to 52 knots.  The pilot got the rolling under control but due to the excessive angle of attack the plane was gaining a lot of altitude.  The pitot tube (a speed sensing device) began to ice up, reducing the size of the opening the air entered.  Changing the airflow into the tube.  Resulting in a speed indication that they were flying faster than they actually were.  The engines were running at 100% power but the nose was pitched up so much that the plane was losing speed and altitude.  There was no accurate air speed indication.  For pilot or autopilot.  The crew failed to follow appropriate procedures for problems with airspeed indication.  And did not understand how to recognize the approach of a stall.  Despite the high speed indicated the plane was actually stalling.   Which it did.  And fell from 38,000 feet in 3 and a half minutes.  Crashing into the ocean.  Killing all 228 on board.

It takes a lot to bring an airplane down from the sky.  And when it happens it is usually the last in a chain of events.  Where each individual event in the chain could not have brought the plane down.  But when taken together they can.  Most times pilots have a chance to save the aircraft.  Especially the stick and rudder pilots.  Who gained a lot of flying experience before the advanced autopilot systems of today.  And can feel what the airplane is doing through the touch of their hand on the yoke and through the seat of their pants.  They are tuned in to the engine noise and the environment around them.  Processing continuous sensations and sounds as well as studying their instruments and the airspace in front of them.  Because they flew the airplane.  Not the computers.  Allowing them to take immediate action instead of trying to figure out what was happening with the computers.  Losing precious time when additional seconds could trigger that last event in a chain of events that ends in the loss of the aircraft.  That’s why some of the best pilots come from this stick and rudder generation.  Such as Aloha Airlines Flight 243, American Airlines Flight 96 and United Airlines Flight 232.  Sometimes the event is so sudden or so catastrophic that there is nothing a pilot can do to save the aircraft.  Such as Japan Airlines Flight 123 and TWA Flight 800.  And sometimes pilots rely so much on automated systems that they let themselves get distracted from the business of flying.  Even the best stick and rudder pilots adjusting to new technology.  Such as Eastern Airlines Flight 401.  Or pilots brought up on the new technology.  Such as Air France Flight 447.  But these events are so rare that when a plane does fall out of the sky it is big news.  Because it rarely happens.  Planes have never been safer.  Which may now be the greatest danger in flying.  A false sense of security.  Which may allow a chain of events to end in a plane falling down from the sky.  As pilots rely more and more on computers to fly our airplanes they may step in too late to fix a problem.  Or not at all.  Trusting those computers more than their piloting skills.

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Inkjet Printing

Posted by PITHOCRATES - March 5th, 2014

Technology 101

A Sunday Afternoon on the Island of La Grande Jatte is similar to Ink Jet Printing

Stephen Sondheim and James Lapine created a musical based on the painting A Sunday Afternoon on the Island of La Grande Jatte by Georges Seurat.  Giving us Sunday in the Park with George.  Seurat used a technique called pointillism.  Where he painted dots of color.  Points.  Up close the eye saw only a mass of different colored dots.  But when you moved back from the painting the brain blended those dots together into an image.

This is the same technique our televisions use to recreate an image on the screen.  Using only the 3 primary colors of light.  Red, blue and green.  Different colors of phosphor are energized to glow.  Causing a combination of these three dots of phosphor to glow creates a pixel of color.  A screen full of different colored pixels creates an image.  It’s similar to inkjet printing.  Where a print head places dots of different colors on a piece of paper.  Much like George did in Sunday in the park with George.  Although an inkjet printer can do it faster.  And without destroying a relationship.

George painted one dot at a time.  So it took him a very long time to create an image.  —SPOILER ALERT—   So much time that Dot left him and had a baby with Louis the baker.  Leaving George alone.  A true suffering artist.  Who died young.  Never realizing that Dot’s baby was his.  Which gave us a second act.  A great musical.  With some of Sondheim’s best music and lyrics.  The original Broadway recording with Mandy Patinkin and Bernadette Peters should be in everyone’s collection.  Do yourself a favor and buy it.  Support the arts.  But I digress.

Droplets of Ink are shot out of the Print Head onto the Paper without any Physical Contact with the Paper

If you have a large art museum near where you live you can probably see a work of art done in the pointilism technique up close.  And if you do you’ll probably notice that the dots are rather big.  Unlike they are with an inkjet printer.  Where the dots are much smaller.  It’s the same technique.  Pointillism.  But it is much harder to see that with inkjet printing.  Why?

George painted with a paint brush.  And even when the bristles are smoothed into a point it’s still pretty thick.  And makes large dots.  An inkjet, on the other hand, doesn’t ‘brush’ on the ink.  It spits it on.  Droplets of ink are shot out of the print head, across an air-gap and onto the paper.  Without any physical contact.  The only physical contact with the paper is the roller that loads a sheet.  And the roller that advances the sheet.  While the print head glides above the paper.  Spitting droplets of ink.

Well, it doesn’t actually spit ink.  It boils it.  In the ink cartridge.  Which is a marvel of engineering.  For the ink cartridge not only contains the ink.  But it also contains the print head.  A few hundred holes where droplets of ink jet out of.  As well as a lot of copper etched circuits.  To take the information from the computer when printing a document.  And transferring it to the proper ink port.  Which are very, very tiny holes.  So tiny that the droplets they produce make for near photo-like quality compared to a pointillism painting.

The Ideal Gas Law tells us if we incrase the Temperature while holding the Volume Constant the Pressure Increases

The ideal gas law is PV = nRT.  Which can be solved such that P = nRT/V.  Where pressure (P) equals the chemical amount in moles (n) times the universal gas constant (R) times the temperature (T) divided by the volume (V).  A lot of information there.  But the only things we want to focus on are pressure, temperature and volume.  The ideal gas law tells us if we incrase the temperature while holding the volume constant the pressure increases.  Which is how inkjet printing works.

Each ink port has ink in it.  But the hole is so tiny that the ink in its normal state will not flow through it.  Because it’s too thick.  However, when you heat the ink to boil it into a vapor the pressure is so great that it pushes a droplet of ink out of the print head onto the paper to releive the pressure.  All of this happens in a fraction of a second in all of those hundreds of ink ports.  An electric circuit turns on.  Boils ink.  Forces out a droplet.  The electric circuit shusts off.  And the ink just used to print with is replaced with fresh ink.  Waiting for the next electric current to boil it.

Complex software and hardware to advance the paper and move the print head over the paper are all coordinated to place thousands of droplets of ink with each pass of the print head.  A black ink cartridge is used for text documents.  And a color ink cartridge (red, blue and yellow) is used to add color to a text document.  Or to print color images.  Doing the work of a thousand Georges.  Faster.  And with tinier dots.  So tiny that they are impossible to detect with the naked eye.  Unlike Seurat’s A Sunday Afternoon on the Island of La Grande Jatte.  But few printed items will look as good.

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Snow Ski

Posted by PITHOCRATES - February 26th, 2014

Technology 101

Gravity and Speed keeps a Skier’s Skies in contact with the Mountain and Provides Control

The Winter Olympics have come and gone.  And if you are a big fan of the Winter Olympics you probably were somewhat disappointed.  Especially if you’re a fan of alpine skiing.  Because it was just too warm.  They have the Olympics in February for a reason.  Because February is a very cold month.  And the mountains have a couple of months of snow on them by February.  Allowing the snow groomers to do their magic.  And turn those mountains into hard sheets of ice.

Yes, ski racers ski on ice.  Not snow.  If you ever skied on a mountain where there was once an Olympic downhill racecourse you will see very steep slopes of ice.  If you ski slowly across the fall line of the slope at the top of the mountain you will slide further down hill than you ski across the slope.  With your ski edges sliding across the ice.  And about the only thing that will stop your ‘free-fall’ slide down that steep ice-covered slope is the loose snow on the sides of the slope.  But if you travel down this same slope at speeds around 70 mph your skies will carve into that ice.  Giving you great control.  If you have the skills of an Olympic downhill skier, that is.  If you’re not as skilled as a downhill racer then you shouldn’t try this.  Because if you fall at speed up there you can do some real damage to yourself.

Downhill skiers love that speed, though.  And will give themselves up completely to gravity.  And let it pull them down these steep, sheets of ice at breakneck speeds.  With nothing to keep them from flying off the mountain and breaking their necks but their skies.  As gravity and speed keeps their skies in contact with the mountain.  Giving them control to stay on their skies.  And carve their way down the mountain.  Literally.

When a Skier leans over on a Ski the Curved Edge of the Ski carves into the Snow or Ice and Turns the Skier

In alpine skiing there are 5 different races.  The downhill.  The super giant slalom (known as super G).  Giant slalom.  Slalom.  And combined.  Which is a combination of two ski races.  One downhill race and one slalom race.  The downhill is the straightest and fastest down the mountain.  The super G is a little more ‘turny’ and a little slower than downhill.   The giant slalom is more ‘turny’ and slower than Super G.  And the slalom is more ‘turny’ and slower than giant slalom.  The downhill is all about speed.  The turns aren’t that sharp.  While the slalom is all about the turns.  With speeds that aren’t that fast.

Each of these races requires different types of skies.  The downhill race needs long skies that will absorb the bumps of rough terrain without bouncing off.  And speed is more important than turning.  While slalom skies need shorter skies to make sharper turns.  And because they are shorter they may come off the snow as they bounce over rough terrain.  So they match the ski to the race.  And because of the requirements of downhill racing these skies are available only to professional skiers.  You will not find them in any sporting goods store.  As amateur and recreational skiers could not control them safely on steep sheets of ice at downhill speeds.

If you look at a ski lying on the ground you will see that it is narrower at the center where it attaches to the ski boot and wider at the tip and the tail.  And it goes from wide to narrow to wide in a continuous curve.  This curve is the side-cut radius.  This is what turns the ski.  When a skier leans over on the ski the curved edge of the ski carves into the snow or ice.  Turning the skier.  The more curved the side-cut radius the tighter turns it will allow.  So slalom skies are more curved in the side-cut radius than downhill skills.

The Winter Olympics are in February so Ski Racers can ski on Mountains that are Hard Sheets of Ice

Looking at a ski resting on a hard surface you will notice something else.  The center of the ski will be off that hard surface.  While the tip and the tail will be in contact with that surface.  This arch—or camber—of the ski helps to force the ski into contact with the snow when you place weight onto them.  Especially the steel edges when turning.  When a skier carves a turn he or she will literally carve that turn into the ice of the mountain.  In a clean turn the tail of the ski will follow the same groove carved by the tip.  With a minimum loss of speed.  If the tail slides out of this groove and carve its own groove it will slow the skier down.  And in downhill skiing where first and second place can be separated by one one-hundredth of a second one slight skid in a turn can be the difference between winning and coming in second.

As downhill skiers leave the starting gate they will take a couple of pushes with their ski poles to help gravity pull them down faster and then assume a tuck position.  To decrease their air drag.  As they approach a gate they will turn by leaning on their edges.  The sharper the turn the more they will lean onto to their edges to carve a tighter turn.  And the more speed they will lose.  Which is why racers will look for the best ‘line’ down the mountain.  One that minimizes sharp turns.  Once out of the turn they will release their edges and ski on the bottom of their skies.  Gaining speed.  They will absorb the rough terrain in their legs.  And fight the compression of the g-forces with their legs.  They lean into turns, release their edges, ride on the bottoms of their skis in the flats, lean on their edges, etc.  At speeds around 70 mph.  As they carve their way down a mountain of ice to cross the finish line in the shortest amount of time.

As spring approaches the ski resorts warm up.  Some people love this.  Spring skiing conditions.  Loose snow on the slopes but warming weather.  So warm that a lot of ski areas will have events like bikini races or lingerie races where girls will ski down the mountain half naked in the warming weather.  It can be a real party on the slopes.  But the skiing will be horrible.  The snow will be melting.  It will be wet.  Granular.  Pushed up into piles.  Making it easy to catch an edge and fall.  And difficult to build up any speed.  Which is why the Winter Olympics are in February.  In the coldest part of winter.  With a lot of snow frozen on the mountain.  And they typically don’t hold them in subtropical climates.  Where the average temperature in February is 50 degrees Fahrenheit.  Like in Sochi, Russia.  Where skiers had to deal with spring skiing conditions.  And varying conditions.  As the snow at the top of a run was different from the snow at the bottom of the run.  Despite the amount of chemicals they put on the snow to try and raise the melting temperature of the snow.  Making these Winter Games not as good as past Winter Games.  If you’re a fan of alpine skiing, that is.  Or prefer seeing cold winter vistas at the Winter Olympics.  And not people lying on the bare grass catching a suntan.

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Engine Block Heaters and Battery Heaters

Posted by PITHOCRATES - February 19th, 2014

Technology 101

As Matter loses Heat it shrinks from a Gas to a Liquid to a Solid

There is no such thing as cold.  Cold is simply the absence of heat.  Which is a real thing.  Heat.  It’s a form of energy.  Warm things have a lot of energy.  Cold things have less energy.  The Kelvin scale is a measurement of temperature.  Like degrees used when measuring temperature in Celsius or Fahrenheit.  Where 32 degrees Fahrenheit equals 0 degrees Celsius.  And 0 degrees Celsius equals 273.15 kelvin.  Not ‘degrees’ kelvin.  Just kelvin.

When something cools it loses heat energy.  The molecular activity slows down.  Steam has a lot of molecular activity.  At 212 degrees Fahrenheit (100 degrees Celsius or 373.15 kelvin) the molecular activity decreases enough (i.e., loses energy) that steam changes to water.  At 32 degrees Fahrenheit (0 degrees Celsius or 273.15 kelvin) the molecular activity decreases enough (i.e., loses energy) that water turns into ice.

The more heat matter loses the less molecules move around.  At absolute zero (0 kelvin) there is no heat at all.  And no molecular movement.  Making 0 kelvin the ‘coldest’ anything can be.  For 0 kelvin represents the absence of all heat.  As matter loses heat it shrinks.  Gases become liquid.  And liquids becomes solid.  (Water, however, is an exception to that rule.  When water turns into ice it expands.  And cracks our roadways.)  They become less fluid.  Or more viscous.  Cold butter is harder to spread on a roll than warm butter.  Because warm butter has more heat energy than cold butter.  So warm butter is less viscous than cold butter.

Vehicles in Sub-Freezing Temperatures can Start Easily if Equipped with an Engine Block Heater

In a car’s internal combustion engine an air-fuel mixture enters the cylinder.  As the piston comes up it compresses this mixture.  And raises its temperature.  When the piston reaches the top the air-fuel mixture is at its maximum pressure and temperature.  The spark plug then provides an ignition source to cause combustion.  (A diesel engine operates at such a high compression that the temperature rise is so great the air-fuel mixture will combust without an ignition source).  Driving the piston down and creating rotational energy via the crank shaft.

For this to happen a lot of things have to work together.  You need energy to spin the engine before the combustion process.  You need lubrication to allow the engine components to move without causing wear and tear.  And you need the air-fuel mixture to reach a temperature to burn cleanly and to extract as much energy from combustion as possible.  None of which works well in very cold temperatures.

Vehicles operating in sub-freezing temperatures need a little help.  Manufacturers equip many vehicles sold for these regions with engine block heaters.  These are heating elements in the engine core.  You’ll know a vehicle has one when you see an electrical cord coming out of the engine compartment.  When these engines aren’t running they ‘plug in’ to an electrical outlet.  A timer will cycle these heaters on and off.  Keeping the engine block warmer than the subfreezing temperatures.

The Internal Combustion Engine is Ideal for use in Cold Temperatures

At subfreezing temperatures engine oil because more viscous.  And more like tar.  This does not flow well through the engine.  So until it warms up the engine operates basically without any lubrication.  In ‘normal’ temperatures the oil heats up quickly and flows through the engine before there’s any damage.  At subfreezing temperatures oil needs a little help when starting.  So the oil sump is heated.  Like an engine block heater.  So when someone tries to start the engine the oil is more like oil and less like tar.

Of course, for any of this to help start an engine you have to be able to turn the engine over first.  And to do that you need a charged battery.  But even a charged battery needs help in sub-freezing temperatures.  For in these temperatures there is little molecular action in the battery.  And without molecular activity there will be little current available to power the engine’s starter.  So there are heaters for batteries, too.  Electric blankets or pads that sit under or wrap around a battery.  To warm the battery to let the chemicals inside move around more freely.  So they can produce the electric power it needs to turn an engine over on a cold day.

Once an engine block, the engine oil and battery are sufficiently warmed by external electric power the engine can start.  Once it warms up it can operate like it can at less frigid temperatures.  The engine alternator powers the electrical systems on the vehicle.  And recharges the battery.  The engine coolant heats up and provides heat for the passenger compartment.  And defrosts the windows.  Once the engine is warm it can shut down and start again an hour or so later with ease.  Making it ideal for use in cold temperatures.  Unlike an electric car.  For the colder it gets the less energy its batteries will have.  Making it a risky endeavor to drive to the store in the Midwest or the Northeast during a winter such as this.  Something people should think about before buying an all-electric car.

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