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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Helicopter

Posted by PITHOCRATES - January 15th, 2014

Technology 101

Varying the Pitch of the Tail Rotor Blade counters the Twisting Force caused by the Helicopter Engine

If you have a rear-wheel drive car with a longitudinally mounted engine (the crankshaft in the engine runs from front to back) you’ve probably noticed the car twisting along the longitudinal axis when starting or revving the engine.  If you ever operated a hand-drill and had the drill bit get stuck in the material you’re drilling through you’ve probably felt the drill twist in your hands.  These are examples of torque.  As the engine or drill motor spins in one direction they also create a counter torque in the opposite direction.  If a drill bit spins clockwise the motor is trying to spin counterclockwise.  Around the axis of the drill bit.

A helicopter has an engine spinning in one direction.  This spins the rotor that creates lift and directional motion.  But a helicopter is not attached to anything.  Motor mounts hold an engine in place in a car that prevents it from spinning in the opposite direction of the crankshaft.  With the car in contact with the ground.  We hold a drill motor to prevent it from spinning in the opposite direction of the drill bit.  With ourselves in contact with the ground.  A helicopter hovers over the ground, though.  It has no physical attachment to prevent the counter torque from spinning the helicopter in the opposite direction from the rotor.  Which is why there is a tail rotor on a helicopter.

Running out from behind the engine/cockpit of a helicopter is a tail boom.  At the end of that boom is a small rotary wing that spins like a propeller.  We can vary the pitch of this blade to push air through in either direction.  Or move it to a neutral position and move no air through it.  By varying the pitch of the tail rotor blade we can provide a counter force to balance the twisting force caused by the engine.  This is what we do with the foot pedals in the helicopter.  Change the pitch in the tail rotor blade to apply more or less counter-twisting force.  To cancel that created by the engine.  And to turn the helicopter to face a new direction.  Especially when hovering.  Helicopters with two large lift-producing rotors/engines (like a Boeing CH-47 Chinook) don’t need tail rotors.  The two engines just spin in opposite directions.  And cancel each other’s twisting torque.

On a Helicopter they Twist the Rotor Blade to Produce more Lift and Increase the Angle of Attack

Both planes and helicopters produce lift with a wing.  A fixed wing on an airplane.  And a rotary wing on a helicopter.  Air passing over the curved surfaces of a wing produces lift.  The more curved the wing the more lift.  And the greater the angle of attack of the wing the greater the lift.  Which is why planes take off with the nose/wings pitched up to create the maximum amount of lift.

Powerful engines on airplanes produce thrust to move the wing through the air.  Requiring long runways to take off.  And dangerous high speeds on the ground.  About 100 mph or so to get airborne.  Making the take off the most dangerous part of flying.  A helicopter, on the other hand, needs no runway.  For it can take off and land vertically.  Because the engine spins the wing through the air to create lift.  It doesn’t have to accelerate the helicopter to produce lift.

Airplane wings have leading-edge slats and trailing edge flaps to increase the curvature of the wing.  And a tail-mounted elevator that can deflect air up pushing the tail down, pitching the nose and wings up.  Increasing the angle of attack of the wings.  On a helicopter they twist the rotor blade to produce more curvature and increase the angle of attack.  With something called the swash plate assembly.

If you let go of the Controls of a Helicopter it will likely Crash for a Helicopter is Inherently Unstable

The rotor shaft rises up vertically from the engine and terminates in the rotor blade assembly above the helicopter.  And passes through the swash plate assembly.  A fixed lower swash plate that doesn’t spin.  And an upper swash plate that spins with the rotor.  Sandwiched between the swash plates are ball bearings.  Allowing these two plates to be in physical contact with each other.  Yet allows the top plate to spin while the bottom plate remains stationary.

Attached between the upper swash plate and the rotor blades are control rods.  Attached between the lower swash plate and the helicopter control levers in the pilot’s hands are control rods.  It is via the swash plate assembly that the pilot’s control inputs are transferred to the rotor blades.  When the pilot pushes the swash plate assembly up with the collective control in his or her left hand (looks like a parking brake on a car) the control rods on the upper plate push up on one side of each rotor blade equally.  Increasing its angle of attack and curvature of each blade equally.  Creating lift.  And drag.  Causing the engine to slow down from the increased load on it.  So when the pilot lifts the collective he or she also twists the handle to increase engine speed (like the accelerator on a motorcycle).

The pilot’s right hand controls the cyclic.  Or the stick coming up between his or her knees.  This is what gives a helicopter its directional motion.  When the pilot moves the cyclic forward it tips the swash plate assembly forward.  The back side of the swash plate assembly rises up while the front side remains roughly where it was.  So as a rotor blade rotates from the front position (forward of the cockpit) to the back position (behind the cockpit) the control rod begins to push up the leading edge of the blade.  Increasing its angle of attack and the curvature of the blade.  Reaching its highest position at the very back of its rotation.  Producing its maximum lift.  As it travels from the back to the front the control rod begins to lower the leading edge of the blade.  Decreasing its angle of attack and the curvature of the blade.  Reaching its lowest position at the very front of its rotation.  This uneven lifting force of the rotor blade tips the helicopter forward and pulls it forward in directional motion.  If the pilot tips the cyclic to the left lift increases on the right side of the rotor, pulling the helicopter to the left.  If the pilot pulls back on the cyclic the lift increases on the front of the rotor, pulling the helicopter backward.

Planes are inherently stable.  If you let go of the controls it will fly true and straight.  For awhile at least.  If you let go of the controls of a helicopter it will likely crash.  For a helicopter is inherently unstable.  And requires constant inputs to the flight controls from the pilot to maintain stable flight.  As it is a delicate balancing act between the collective, the cyclic and the foot pedals.  For every input of one creates an imbalance that must be corrected by the input of another.  Making the helicopter pilot perhaps the most skilled of all pilots.  Especially those kids just out of high school who flew in Vietnam.  Who flew these complicated flying machines like sports cars as they avoided enemy fire.  Making them without a doubt the finest pilots ever to fly.

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Aircraft De-Icing Systems

Posted by PITHOCRATES - October 23rd, 2013

Technology 101

A build-up of Ice on Airfoils causes a Reduction of Lift and a Loss of Stability

In the classic movie Airport (1970) after the guy pulled the trigger on his briefcase bomb the plane suffered a massive decompression.  When Dean Martin got back to the cockpit he told the flight engineer to give them all the heat they had.  Because it’s very cold flying above 10,000 feet without pressurization.  That’s why World War II flight crews wore a lot of heavy clothing and thick mittens in their bombers.  As well as oxygen masks as the air was too thin to breathe.  The B-17 even had open windows for the waste gunners.  Making it very cold inside the plane.  Because the air is very, very cold at altitude.

There is another problem at altitude.  Because of these very frigid temperatures.  Water droplets in the air will freeze to any surface they come into contact with.  They can reduce engine power for both propeller and jet engines.  They can freeze on ports used for instrumentation and give inaccurate readings of vital aircraft data (such as engine pressure ratio, aircraft speed, etc.).  And they can freeze on airfoils (wings, rudder, tail fin, etc.).  Disturbing the airflow on these surfaces.  Causing a reduction of lift and a loss of stability.

Ice and airplanes are two things that don’t go together.  As ice forms on a wing it disturbs the airflow over the surface of the wing.  Increasing drag.  And reducing lift.  Causing the plane to lose speed.  And altitude.  If the ice continues to form on the wing eventually it will stall the wing.  And if the wing stalls (i.e., produces no lift) the plane will simply fall out of the sky.  In the early days of aviation pilots were highly skilled in flying their planes where there were no icing conditions.  Flying over, under or around masses of air containing water droplets in subfreezing temperatures.  Today we have anti-icing systems.

The most common Anti-Icing System on Commercial Jets is a Bleed Air System

One of the most common anti-icing systems on turboprop aircraft is the use of inflatable boots over the leading edge of the wing.  Basically a rubber surface that they can pump air into.  When there is no ice on the wing the boot lies flat on the leading edge without interrupting the airflow.  When ice forms on the leading edge of the wing the boot inflates and expands.  Cracking the ice that formed over it.  Which falls away from the wing.

Commercial jets have larger airfoils.  And require a larger anti-icing system.  The most common being a pneumatic manifold system that ducts hot air to areas subject to icing.  Which works thanks to a property of gas.  If you compress a gas you increase its temperature.  That’s how a diesel engine can work without sparkplugs.  The compressed air-fuel mixture gets so hot it ignites.  This property comes in handy on a jet plane as there is a readily available source of compressed air.  The jet engines.

As the air enters the jet it goes through a series of fast-spinning rotors.  As the air moves through the engine these rotors push this air into smaller and smaller spaces.  Compressing it.  Through a low-pressure compressor.  And then through a high-pressure compressor.  At which time the air temperature can be in excess of 500 degrees Fahrenheit.  It is in the high-pressure compressor that we ‘bleed’ off some of this hot and pressurized air.  We call this a bleed air system.  The air then enters a manifold which ducts it to at-risk icing areas.  From the engine cowling to the wings to the instrumentation ports.  Using the hot air to raise temperatures in these areas above the freezing temperature of water.  Thus preventing the formation of ice.

The Drawback of a Bleed Air System is Reduced Engine Efficiency

The bleed air system does more than just anti-icing.  It also pressurizes the cabin.  As well as keeps it warm.  Which is why we don’t have to dress like a crewmember on a World War II bomber when we fly.  It also powers the air conditioning system.  And the hydraulic system.  It provides the pressure for the water system.  And it even starts the jet engines.  With the source of pressurized bleed air coming from the auxiliary power unit mounted in the tail.  Or from an external ground unit.  Once the jets are running they disconnect from the auxiliary source and run on the bleed air from the engines.

There is one drawback of a bleed air system.  It bleeds air from the jet engine.  Thus reducing the efficiency of the engine.  And a less efficient engine burns more fuel.  Raising the cost of flying.  With high fuel costs and low margins airlines do everything within their power to reduce the consumption of fuel.  Which is why pilots don’t top off their fuel tanks.  They’d like to.  But extra fuel is extra weight which increases fuel consumption.  So they only take on enough fuel to get to their destination with enough reserve to go to an alternate airport.  Even though it seems risky few planes run out of fuel in flight.  Allowing the airlines to stay in business without having to raise ticket prices beyond what most people can afford.

To help airlines squeeze out more costs Boeing designed their 787 Dreamliner to be as light as possible by using more composite material and less metal.  Making it lighter.  They are also using a more efficient engine.  Engines without a bleed air system.  In fact, they eliminated the pneumatic system on the 787.  Converting the pneumatic components to electric.  Such as using electric heating elements for anti-icing.  Thus eliminating the weight of the bleed air manifold and duct system.  As well as increasing engine efficiency.  Because all engine energy goes to making thrust.  Which reduces fuel consumption.  The key to profitability and survival in the airline industry.

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Moving Big Things in Small Spaces

Posted by PITHOCRATES - September 11th, 2013

Technology 101

Ships once used Tugs to Maneuver around in Small Spaces but Today they use Tunnel Thrusters

As technology progressed the more things we needed to make other things.  Small factories grew into large manufacturing plants.  Which consumed vast quantities of material to produce vast quantities of goods.  Requiring ever larger means of transportation.  And we have built some behemoths of transportation.

Water transport has been the preferred method for heavy transport.  Which is why most early cities were on rivers.  As time passed our cities got bigger.  Our industry got bigger.  And our ships got bigger.  Huge bulk freighters bring iron ore, coal, limestone, etc., from northern ports across the Great Lakes to docks on small rivers and harbors further south.  On the open lakes these ships can put the pedal to the metal.  Roaring across these lakes at breakneck speeds of 15 mph.  If you’ve ever seen a Great Lakes freighter at full throttle you probably noticed something.  They push a lot of water out of their way.  Something they can’t do in those small rivers and harbors.  As their wake would push the river over its banks.  So they slow down to a non-wake speed of something slower than a person walking.

Lakes are huge bodies of deep water.  But these Great Lakes freighters, or lakers, often enter narrow and shallow rivers.  Some rivers even too shallow.  So they dredge a channel in them.  So these lakers don’t bottom out.  Some lakers have to travel upriver to offload.  Then turn around.  Which isn’t easy in a shallow river when your ship is 700-1,000 feet long.  They once used tugs to push these ships around.  But today they use tunnel thrusters.  An impeller inside a tunnel through the ship at the bow and stern perpendicular to the beam and below the water line.  Which can turn a ship without the forward motion a rudder requires.  Allowing it to move as if a tug is pushing it.  Only without a tug.

Interesting thing about Trains is that they don’t have a Steering Wheel

With the introduction of the railroad cities moved away from rivers and coastlines.  But the railroads only became a part of the heavy transport system.  Cities grew up along the railroads.  Where farmers in a region brought their harvests to grain elevators.  Trains took their harvests from these elevators to ports on rivers and coastlines.  Where they could offload to ships or barges.  And it would take a large ship or a barge.  Because one long train can carry a lot of harvest.

Interesting thing about trains is that they don’t have a steering wheel.  For there is only two directions they can go.  Forward.  And backward.  If you’ve traveled passenger rail to the end of the line you may have experienced a train turning around.  The train will reduce speed to a crawl as they switch over to a perpendicular-running track.  For trains do not travel well on curves.  Because the wheels are connected to a solid axel.  So in a turn the outer wheel needs to travel faster to keep up with the inner wheel.  But can’t.  Causing the wheels to slip instead.  Causing wear and tear on the train wheels.  And track.  Which is why curved track does not last as long as straight track.  The train travels a while on this perpendicular track at a crawl until the rear end passes another switch.  It then stops.  And goes backward.  Switching back to the track it was originally on.  Only now backing up instead of traveling forward.  The train then backs into the passenger terminal.  Ready to leave from this end of the line going forward.  To the other end of the line.

Freight trains are a lot longer than passenger trains.  Some can be a mile long.  Or longer.  And rarely turn around like a freight train.  Rail cars are added to each other creating a consist in a rail yard.  A switcher (small locomotive) moves back and forth picking up cars and attaching them to the consist.  In the reverse order which they will be disconnected and left in rail yards along the way.  Once they build the consist they bring in the go-power.  Typically a lashup of 2-3 locomotives (or more if they’re the older DC models).  The lead locomotive will typically face forward.  Putting the engineer at the very front of the train.  In the old days they had roundhouses to switch the direction of these locomotives.  Today they turn them around when they need to like the passenger train turning around.  Which is much easier as they only have to turn around one locomotive in the lashup.

Planes may Fly close to 500 mph in the Air but on the Ground they move about as Fast as Someone can Walk

Airplanes are big.  In flight they’re as graceful as a bird in flight.  But it’s a different story on the ground.  Planes are big and heavy.  They have a huge wingspan.  And the pilots sit so far forward that they can’t see how close their wingtips are to other things.  Such as other airplanes.  When they leave a gate they usually have a tug push them back and get them facing forward.  At which time they start their engines.  As it would be dangerous to start them while at the gate where there are a lot of people and equipment servicing the plane.  They don’t want to suck anything—a person or a piece of equipment—into the jet engines.  And they don’t want to blow anything away moving behind the engines as the jet blast from a jet can blow a bus away.  And has.  In flight they use their ailerons to turn.  The flaps on the tips of each wing that roll a plane left or right.  Causing the plane to turn.  The rudder is used for trimming a plane.  Or, in the case of an engine failure, to correct for asymmetric thrust that wants to twist the airplane like a weathercock.  On the ground they use a little steering wheel (i.e., a tiller) outboard of the pilot (to the left of the left seat and to the right of the right seat) to turn the nose gear wheel.

Pilots can’t see a lot out of the cockpit window while on the ground.  Which is why they rely on ground crews to give them direction.  And to walk alongside the wings during the pushback.  To make sure the wings don’t hit anything.  And that no one hits the plane.  Once the tug disconnects and the plane is under its own power the flight crew takes directions from ground controllers.  Whose job is to safely move planes around the airport while they’re on the ground.  Planes may fly close to 500 mph in the air but on the ground they move about as fast as someone can walk.  For planes are very heavy.  If they get moving too fast they’re not going to be able to stop on a dime.  Which would be a problem if they’re in a line of planes moving along a taxiway to the runway.

When we use big things to move people or freight they work great where they are operating in their element.  A ship speeding across an open lake.  A train barreling along straight track.  Or a plane jetting across the open skies.  But when we rein these big things in they are out of their element.  Ships in narrow, shallow rivers.  Trains on sharply curved track.  And planes on the ground.  Where more accidents happen than when they are in their element.  Ships that run into bridges.  Trains that derail.  And planes that hit things with their wings.  Because it’s not easy moving big things in small places.

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Thrust, Drag, Lift, Weight, Concorde, Center of Pressure, Center of Gravity, Boeing 747, Slats and Flaps

Posted by PITHOCRATES - January 16th, 2013

Technology 101

The Drawback to increasing Thrust and Lift with more Powerful Engines is the Weight of Greater Fuel Loads

To get an airplane off of the ground requires two things.  To produce thrust that is greater than drag.  And to produce lift that is greater than weight.  You do this and you’ll get any airplane off of the ground.  Of course, getting these two things is not the easiest thing to do.  Primarily because of the purpose of airplanes.  To move people and freight.  People and freight add weight.  Which increases the amount of lift needed.  And they make the plane bigger.  A bigger object displaces more air increasing drag.  And thus requiring more thrust.

Engines provide thrust.  And wings provide lift.  So the obvious solution to overcome greater drag is to produce greater thrust.  And the solution to overcome greater weight is to produce greater lift.  And we do both with fuel.  Greater amounts of fuel can power bigger engines that can produce more thrust.  And larger wings can produce greater lift.  But larger wings also produce more drag.  Requiring additional thrust.  And fuel.  Or, we can produce greater lift by moving air over the wings faster.  Also requiring additional thrust.  And fuel.

Of course, the obvious drawback to increasing both thrust and lift is the added weight of the fuel.  The more fuel carried the more weight lift has to overcome.  Requiring more powerful engines.  Or bigger wings.  Both of which require more fuel.  This is why our first planes were small by today’s standards.  The thrust of a propeller engine could not produce enough thrust to travel at high speeds.  Or operate at high altitudes.  And the first wings were relatively fixed.  Having the same surface area to produce lift at takeoffs and landings.  As well as at cruising altitudes.  Big wings that allowed the lifting of heavier weights produced a lot of drag.  Requiring more fuel to overcome that drag.  And the added weight of that fuel limited the number of people and freight they could carry.  Or they could trade off that fuel for more revenue weight.  The smaller fuel load, of course, reduced flying times.  Requiring an additional takeoff and landing or two to refuel.

A Wing that produces sufficient Lift at 600 MPH does not produce sufficient Lift at Takeoff and Landing Speeds

The supersonic Concorde was basically a flying gas can.  It was more missile than plane.  To travel at those great speeds required a very small cross section to reduce drag.  Limiting the Concorde to about 100 revenue paying passengers.  Its delta wing performed well at supersonic flight but required a drooping nose so the pilot could see over it to land and takeoff due to the extreme nose pitched up attitude.  As Concorde approached supersonic speeds the center of pressure moved aft.  Placing the center of gravity forward of the center of pressure.  Causing the nose to pitch down.  You correct this with trim controls on slower flying aircraft.  But using this on Concorde would create additional drag.  So they trimmed Concorde by pumping the remaining fuel to other fuel tanks to move the center of gravity to the center of pressure.

They designed Concorde to fly fast.  Which came at a cost.  They can only carry 100 revenue paying passengers.  So they can only divide the fuel cost between those 100 passengers.  Whereas a Boeing 747 could seat anywhere around 500 passengers.  Which meant you could charge less per passenger ticket while still earning more revenue than on Concorde.  Which is why the Boeing 747 ruled the skies for decades.  While Concorde flies no more.  And the only serious competition for the Boeing 747 is the Airbus A380.  Which can carry even more revenue paying passengers.  How do they do this?  To fly greater amount of people and freight than both piston-engine and supersonic aircraft?  While being more profitable than both?  By making compromises between thrust and drag.  And lift and weight.

Jet engines can produce more thrust than piston engines.  And can operate at higher altitudes.  Allowing aircraft to take advantage of thinner air to produce less drag.  Achieving speeds approaching 600 mph.  Not Concorde speeds.  But faster than every other mode of travel.  To travel at those speeds, though, requires a cleaner wing.  Something closer to Concorde than, say, a DC-3.  Something thinner and flatter than earlier wings.  But a wing that produces lift at 600 mph does not produce enough lift at takeoff and landing speeds.

Planes need more Runway on Hot and Humid Days than they do on Cool and Dry Days

The other big development in air travel (the first being the jet engine) are wings that can change shape.  Wings you can configure to have more surface area and a greater curve for low-speed flying (greater lift but greater drag).  And configure to have less surface area and a lesser curve for high-speed flying (less lift but less drag).  We do this with leading-edge slats (wing extensions at the leading edge of the wing).  And trailing-edge flaps (wing extensions at the trailing edge of the wing).  When fully extended they increase the surface area of the wing.  And add curvature at the leading and trailing edge of the wing.  Creating the maximum amount of lift.  As well as the greatest amount of drag.  Allowing a wing to produce sufficient lift at takeoff speeds (about 200 mph).  Once airborne the plane continues to increase its speed.  As it does they retract the slats and flaps.  As the wing can produce sufficient lift at higher speeds without the slats and flaps extended.

But there are limits to what powerful jet engines and slats/flaps can do.  A wing produces lift by having a high pressure under the wing pushing up.  And a low pressure on top of the wing pulling it up.  The amount of air passing over/under the wing determines the amount of lift.  As does the density of that air.  The more dense the air the more lift.  The thinner the air the less lift.  Which is why planes need less runway on a cold winter’s day than on a hot and humid summer’s day.  If you watch a weather report you’ll notice that clear days are associated with a high pressure.  And storms are associated with a low pressure.  When a storm approaches meteorologists will note the barometer is falling.  Meaning the air is getting thinner.  When the air is thinner there are fewer air molecules to pass over the wing surface.  Which is why planes need more runway on hot and humid days.  To travel faster to produce the same amount of lift they can get at slower speeds on days cooler and dryer.

For the same reason planes taking off at higher elevations need more runway than they do at lower elevations.  Either that or they will have to reduce takeoff weight.  They don’t throw people or their baggage off of the airplane.  They just reduce the fuel load.  Of course, by reducing the fuel load a plane will not be able to reach its destination without landing and refueling.  Increasing costs (airport and fuel expenses for an additional takeoff and landing).  And increasing flying time.  Which hurts the economics of flying a plane like a Boeing 747.  A plane that can transport a lot of people over great distances at a low per-person cost.  Adding an additional takeoff and landing for refueling adds a lot of cost.  Reducing the profitability of that flight.  Not as bad as a normal Concorde flight.  But not as good as a normal Boeing 747 flight.

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Air, Low Pressure, High Pressure, Lateen Sail, Flight, Wing, Lift, Drag, Leading Edge Slats, Trailing Edge Flaps and Angle of Attack

Posted by PITHOCRATES - October 10th, 2012

Technology 101

There’s more to Air than Meets the Eye even though it’s Invisible

When you take a shower have you noticed how the shower curtain pulls in towards you?  Have you ever wondered why it does this?  Here’s why.  Air has mass.  The water from the showerhead sends out a stream of water drops that also has mass.  So they fall to the floor of the shower.  Pushing air with it.  And pulling air behind it.  (Like drinking through a straw.  As you suck liquid out of the straw more liquid enters the straw.)  So you not only have a stream of water moving down alongside the shower curtain.  You also have a stream of air moving down alongside the shower curtain.

As the falling water sweeps away the air from the inside of the shower current it creates a low pressure there.  While on the outside of the curtain there is no moving water or air.  And, therefore, no change in air pressure.  But there is a higher pressure relative to the lower pressure on the inside of the shower curtain.  The low pressure inside pulls the curtain while the high pressure outside pushes it.  Causing the shower curtain to move towards you.

There’s more to air than meets the eye.  Even though it’s invisible.  It’s why we build modern cars aerodynamically to slice through large masses of invisible air that push back against cars trying to drive through it.  Making our engines work harder.  Consuming more gas.  And reducing our gas mileage.  While race cars will use spoilers to redirect that air up, forcing the weight of the car down on the tires.  To help the tires grip the road at higher speeds.  We even design skyscrapers to be aerodynamic.  To split the prevailing winds around the buildings to prevent large masses of air from slamming into the sides of buildings, minimizing the amount buildings sway back and forth.

We put the Engines on, and the Fuel in, the Wings to Counteract the Lifting Force on an Aircraft’s Wings

Air can be annoying.  Such as when the shower curtain sticks to your leg.  As it steals miles per gallon from your car.  When it shakes the building you’re in.  But it can also be beneficial.  As in early ship propulsion before the steam engine.  Large square-rigged sails that pushed ships along the prevailing winds.  And triangular lateen sails that allowed us to travel into the wind.  By zigzagging across the wind.  With the front edge of a lateen sail slicing into the wind.  The sail redirects the wind on one side of the sail to the rear of the boat that pushes the boat forward.  While the wind on the other side follows the curved sail creating a low pressure that pulls the boat forward.  Like the inside of that shower curtain.  Only with a lot more pulling force.

Harnessing the energy in wind let the world become a smaller place.  As people could travel anywhere in the world.  Of course, some of that early travel could take months.  And spending months on the open sea could be very trying.  And dangerous.  A lot of early ships were lost in storms.  Ran aground on some uncharted shoal.  Or simply got lost and ran out of drinking water and food.  Or fell to pirates.  So it took a hearty breed to travel the open seas under sail.  Of course today long-distant travel is a bit easier.  Because of another use for air.  Flight.

Like a lateen sail an aircraft wing splits the airflow above and below the wing.  And like the lateen sail an aircraft wing is curved.  The air pushes on the bottom of the wing creating a high pressure.  While the air passing over the curve of the top of the wing creates a low pressure.  Pulling the wing up.  In fact, it’s the wind passing over the top of the wing that does the lion’s share of lifting airplanes into the air.  The low pressure on top of the wing is so great that they put the engines on the wings, and the fuel in the wings, to counteract this lifting force.  To prevent the wings from curling up and snapping off of the plane.  Planes with tail-mounted engines have extra reinforcement in the wings to resist this bending force.  So those lifting forces only lift the plane.  And not curl the wing up until it separates from the plane.

To make Flying Safe at Slow Speeds they add Leading Edge Slats and Trailing Edge Flaps to the Wing

Sails can propel a ship because a ship floats on water.  The wind only propels a ship forward.  On an airplane the wind moving over the wings provides only lift.  It does not propel a plane forward.  Engines propel planes forward.  And it takes a certain amount of forward speed to make the air passing over the wings fast enough to create lift.  The faster the forward air speed the greater the lift.  Today jet engines let planes fly high and fast.  In the thin air where there is less drag.  That is, where the air has less mass pushing against the forward progress of the plane.  At these altitudes the big planes cruise in excess of 600 miles per hour.  Where these planes fly at their most fuel efficient.  But these big planes can’t land or take off at speeds in excess of 600 miles per hour.  In fact, a typical take-off speed for a 747-400 is about 180 miles per hour.  Give or take depending on winds and aircraft weight.  So how does a plane land and take off at speeds under 200 mph while cruising at speeds in excess of 600 mph?  By changing the shape of the wing.

We determine the amount of lift by the curvature and surface area of the wing.  The greater the curvature the greater the lift.  However, the greater the curvature the greater the drag.  And the greater the drag the more fuel consumed at higher speeds.  And the more stresses placed on the wing.  Also, current runways are about 2 miles long for the big planes.  That’s when they land and take off at speeds under 200 mph.  To land and take off at speeds around 600 mph would require much longer runways.  Which would be extremely costly.  And dangerous.  For anything traveling close to 600 mph on or near the ground would have a very small margin of error.  So to make flying safe and efficient they add leading edge slats to the front edge of the wing.  And trailing edge flaps to the back edge of the wing.  During cruise speeds both are fully retracted to reduce the curvature of the wing.  Allowing higher speeds.  At slower speeds they extend the slats and flaps.  Greatly increasing the curvature of the wing.  And the surface area.  Providing up to 80% more lift at these slower speeds.

At takeoff and landing pilots elevate the nose of the aircraft to increase the angle of attack of the wing.  Forcing more air under the wing to push the wing up.  And causing the air on top of the wing to turn farther away for its original direction of travel as it travels across the top of the up-tilted wing.  Creating greater lift.  And the ability to fly at slower speeds.  However, if the angle of attack it too great the smooth flow of air across the wing will break away from the wing surface and become turbulent.  The wing will not be able to produce lift.  So the wing will stall.  And the plane will fall out of the sky.  With the only thing that can save it being altitude.  For in a stall the aircraft will automatically push the stick forward to lower the nose.  To decrease the angle of attack of the wing.  Decrease drag.  And increase air speed.  If there is enough altitude, and the plane has a chance to increase speed enough to produce lift again, the pilot should be able to recover from the stall.  And most do.  Because most pilots are that good.  And aircraft designs are that good.  For although flying is the most complicated mode of travel it is also the safest mode of travel.  Where they make going from zero to 600 mph in a matter of minutes as routine as commuting to work.  Only safer.

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Airbus proposing Measures to Reduce the Aviation Carbon Footprint that may make Flying more Dangerous

Posted by PITHOCRATES - September 9th, 2012

Week in Review

Airplanes are very complex machines.  They fly at speeds 3-4 times the speeds they land and take off at.  Which requires leading edge slats and trailing edge flaps to curve the wing more at low speed to increase lift.  While flattening it out more at high speeds to reduce drag.  When landing pilots put the engines into reverse thrust to help slow the plane down.  So they even use fuel to slow down.

And speaking of fuel it’s expensive.  Airlines carry as little of it as possible in their airplanes to reduce weight which reduces costs.  Sometimes bad weather forces planes to go to an alternate airport.  Sometimes there are strong headwinds.  Sometimes they fly into Heathrow and have to circle for a half hour or so to land.  Because they only have two runways.  Compounding this problem planes are getting lighter and engines are getting more efficient.  Allowing airlines to carry even less fuel.  So it is not uncommon for a pilot to declare a fuel emergency because of unexpected additional flying time.

When flying in the air highways air traffic controllers keep airplanes separated by large distances.  To keep them from running into each other.  The more distance the better so they can take evasive actions to avoid bad weather cells.  Or allow a plane some leeway in case they have a system malfunction (like plugged pitot tubes feeding false air speed and altimeter readings into the autopilot) that takes the plane off course.  Or in case a plane flies into some clear air turbulence (CAT) and it drops out of the sky 1,000 feet or so.  Or rises 1,000 feet or so.  Two things that allow a plane to recover from unplanned events like these are empty skies around you and altitude.

Aviation has come a long way.  And Boeing and Airbus are making some incredible airplanes.  So they know a thing or two about flying an airplane.  And it shows in their planes.  Which makes it hard to take them seriously when they talk about ways to reduce their carbon footprint by making flying more risky (see Airbus To Present Measures To Reduce Industry’s Environmental Footprint by Jens Flottau posted 9/6/2012 on Aviation Week).

Airbus on Sept. 6 will unveil five measures it says will make the aviation industry environmentally sustainable by 2050 despite projected growth for global air transport…

Airbus also foresees a new method for takeoff, with renewably powered propelled acceleration allowing aircraft to climb steeper and reach cruise altitude faster. This in turn would allow airports to build shorter runways and minimize land use.

Once in cruise, aircraft should be able to self-organize and select the most efficient routes, says Airbus. On dense routes, aircraft could fly in formation, like birds, to take advantage of drag reduction opportunities.

In Airbus’ vision, aircraft will descend without using engine power or air brakes and would be able to decelerate quicker and to a lower final approach speed enabling them to use shorter runways…

Fuel is a key component of Airbus’ proposal, and the manufacturer says the use of biofuels hydrogen, electricity and solar energy will be required to reduce the industry’s environmental footprint.

You simply can’t build shorter runways.  Because planes aren’t perfect.  Sometimes things happen.  If we had shorter runways what would happen to a plane landing with damaged leading edge slats or trailing edge flaps?  And they have to land at a higher speed than normal because they can’t curve the wing to create more lift at lower speeds?  And what if a plane’s thrust reversers failed to deploy?  This is why we have long runways.  To give planes with problems a better chance to land safely.

Flying commercial jets in formation?  Not a good idea.  One of the most dangerous things to do in the Air Force is aerial refueling.  Where two large planes get real close to each other.  If they bump into each other they could cause some damage.  Even cause them to crash.  Flying in formation would be exhausting for a pilot.  Or they could entrust their formation flying to an autopilot.  But if they hit some CAT and get thrown around in that airspace they could get thrown into each other.  Even while flying on autopilot.  Planes also make their own turbulence.  Which is why there are larger distances between the big planes (i.e., the heavies) and the small ones.  So the small ones don’t get flipped over by some spiraling wingtip vortex turbulence off the heavy in front of it.

Solar energy?  Really?  How?  It’s not going to propel a jumbo jet.  And if they think they’re going to save on engine emissions by using solar panels on the wings to produce electricity for the cabin lights and electronics I don’t think that will work.  The emissions from the electrical load on those engines may be negligible compared to emissions they make producing thrust for flight.  And if they add more weight (solar panels) that will only take more fuel for flight.  Which will release more emissions.  Finally, a lot of planes fly at night.  When there is no sunshine.  What then?

Trying to reduce a plane’s carbon footprint will only make flying more dangerous.  It’s one thing to throw money away building solar panels and windmills on the ground.  For that’s just ripping the people off.  But applying this nonsense to aviation may end up killing people.  It’s hard to believe that Airbus is serious with these suggestions.  One wonders if they’re just proposing this to get those proposing that carbon trading scheme to back off as it will increase the cost of flying.  Which will reduce the number of people flying.  And reduce the number of planes Airbus can sell.  Perhaps by dangling this green future of aviation they may buy some time before the carbon trading scheme kills the aviation industry.

Fighting nonsense with nonsense.  It’s just as good an explanation as any.

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Windmills, Rotational Energy, Wing, Lift, Rotary Wing, Angle of Attack, Variable-Pitch Propellers, Drag, AC Power and Wind Turbine

Posted by PITHOCRATES - June 27th, 2012

Technology 101

When an Aircraft Rotates for Takeoff it increases the Angle of Attack of the Wing to Create more Lift

Early windmills turned when the wind pushed a sail or vane.  Thereby converting wind energy into rotational energy.  Mechanical linkages and shafts transferred this rotational motion to power a mill.  Or pump water.  As well as an assortment of other tasks.  Whatever the task it was important to regulate the speed at which the shaft rotated.  Which meant turning the windmill into the wind.  And adjusting the amount of sail catching the wind.  Much like on a sailing ship.  At first by shutting the windmill down and manually adjusting the sails.  Then later automating this process while the windmill was turning.  If the winds were too strong they’d lock the windmill to prevent it from turning.  To prevent damaging the windmill.

They regulated the speed to protect the equipment attached to the windmill, too.  To prevent a mill stone from spinning too fast.  Risking damage to it.  And harm to the people working with the equipment.  Or to protect a water pump form pumping too fast.  Even the small farm windmills had over-speed protection.   These sat atop a well.  The windmill drove a small piston to pump the water up the well shaft.  To prevent this windmill from flying apart in high winds over-speed features either furled the blades or rotated the windmill parallel to the wind.  Shutting the pump down.

But wind just doesn’t push.  It can also lift.  A lateen (triangular) sail on a sailing vessel is similar to an aircraft wing.  The leading edge of the sail splits the wind apart.  Part of it fills the sail and pushes it.  Bowing it out into a curved surface.  The wind passing on the other side of the sail travels across this curved surface and creates lift.  Similar to how a wing operates during takeoff on a large aircraft.  With the trailing edge flaps extended it creates a large curve in the wing.  When the aircraft rotates (increasing the angle of attack of the wing) to take off wind passing under the wing pushes it up.  And the wind travelling over the wing pulls it up.  These lift forces are so strong that planes carry their fuel in the wings and mount engines on the wing to keep the wings from bending up too much from these forces of lift.

A Pilot will Feather the Propeller on a Failed Engine in Flight to Minimize Drag 

When an aircraft carrier launches its aircraft it turns into the wind.  To maximize the wind speed travelling across the wings of the aircraft.  For the faster the wind moves across the wing the great lift it creates.  Commercial airports don’t have the luxury of turning into the wind.  So they lay their runways out to correspond to the prevailing wind directions.  As weather systems move through the region they often reverse the direction of the wind.  When they do planes take off in the other direction.  If the winds are somewhere in between these two extremes some airports have another set of runways called ‘crosswind’ runways.  Or trust in the highly skilled pilots flying out of their airports to adjust the control surfaces on their planes quickly and delicately to correct for less than optimal winds.

Helicopters don’t have this problem.  They can take off facing in any direction.  Because that big propeller on top is a rotary wing.  Or rotor.  A fixed wing airplane needs forward velocity to move air over their wings to create lift.  A helicopter moves air over its rotary wing by spinning it through the air.  To create lift the pilot tilts the rotor blades to change their angle of attack.  And tilts the whole rotor in the direction of travel.  The helicopter’s engine runs at a constant RPM.  To increase lift the angle of attack is increased.  This also creates drag that increases the load on the engine, slowing it down.  So the pilot increases the throttle of the engine to return the rotor to that constant RPM.

Propeller-powered airplanes also have variable-pitch propellers.  To create the maximum possible lift at the lowest amount of drag.  So it’s not just engine speed determining aircraft speed.  When running up the engines while on the ground the pilot will feather the propellers.  So that the blade pitch is parallel to the airflow and moves no air.  This allows the engines to be run up to a high RPM without producing a strong blast of air behind it.  A pilot will also feather the prop on a failed engine in flight to minimize drag.  Allowing a single-engine plane to glide and a multiple engine plane to continue under the power of the remaining engines.  A pilot can even reverse the pitch of the propeller blades to reverse the direction of airflow through the propeller.  Helping planes to come to a stop on short runways.

By varying the Blade Pitch for Different Wind Speeds Wind Turbines can Maintain a Constant RPM

Thomas Edison developed DC electrical power.  George Westinghouse developed AC electrical power.  And these two went to war to prove the superiority of their system.  The War of the Currents.  Westinghouse won.  Because AC is economically superior.  One power plant can power a very large geographic area.  Because alternating current (AC) works with transformers.  Which stepped up voltages for long-distance power transmission.  And then stepped them back down to the voltages we use.  Power equals voltage times current.  Increasing the voltages allows lower currents.  Which allows thinner wires.  And fewer generating plants.  Which saves money.  Hence the economic superiority of AC power.

Alternating current works with transformers because the current alternates directions 60 times a second (or 60 cycles or hertz).  Every time the currents reverse an electrical field collapses in one set of windings of a transformer, inducing a voltage in another set of windings.  A generator (or, alternator) creates this alternating current by converting rotational energy into electrical energy.  Which brings us back to windmills.  A source of rotational energy.  Which we can also use to generate electrical energy.  But unlike windmills of old, today’s windmills, or wind turbines, turn from lift.   The wind doesn’t push the blades.  The wind passes over them producing lift.  Like on a wing.  Pulling them into rotation.

The typical wind turbine design is a three-bladed propeller attached to a nacelle sitting on top of a tall pylon.  The nacelle is about as large as a big garden shed or a small garage.  Inside the nacelle are the alternator and a gearbox.  And various control equipment.  Like windmills of old wind turbines still have to face into the wind.  We could do this easily and automatically by placing the propeller on the downwind side of the nacelle.  Making it a weathervane as well.  But doing this would put the pylon between the wind and the blades.  The pylon would block the wind causing uneven loading on the propeller producing vibrations and reducing the service life.  So they mount the propeller on the upwind side.  And use a complex control system to turn the wind turbine into the wind.

When it comes to electrical generation a constant rotation is critical.  How does this happen when the wind doesn’t blow at a constant speed?  With variable-pitched blades on the propeller.  By varying the blade pitch for different wind speeds they can maintain a constant number of revolutions per minute (RPM).  For a limited range of wind conditions, that is.  If the wind isn’t fast enough to produce 60 hertz they shut down the wind turbine.  They also shut them down in high winds to prevent damaging the wind turbine.  They can do this by feathering the blades.  Turning the propeller blades parallel to the wind.  Or with a mechanical brake.  The actual rotation of the propeller is not 60 cycles per second.  But it will be constant.  And the gearbox will gear it up to turn the alternator at 60 cycles per second.  Allowing them to attach the power they produce to the electric grid.

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Steam Locomotive, Diesel Electric Locomotive, Interstate Highway System, Airplane, Air Travel, Refined Petroleum Products and Pipelines

Posted by PITHOCRATES - March 21st, 2012

Technology 101

The Diesel Electric Locomotive could pull a Train Cross Country and into the Heart of a City with Minimal Pollution

The 1920s were transformative years.  The Roaring Twenties.  It’s when we moved from animal power to mechanical power.  From the horse and plow to the tractor.  From steam power to electric power.  From the telegraph to the telephone.  From the gas lamp to the electric light.  From crowded mass transit to the freedom of the automobile.  From manual labor to the assembly line. 

You can see a glimpse of that world in 1920’s Steam Train Journey Across the United States – Westward Ho!  The beginning of the modern city.  With modern street lighting.  Electric power and telephone overhead wiring.  Streets crowded with automobiles.  Tractors and mechanical harvesters on the farm.  And, of course, the steam locomotive.  Connecting distant cities.  Transferring the freight to feed the modern industrial economy.  And shipping the finished goods.  As well as all that food from the farm to our grocer’s shelves.  Proving the 1920s were vibrant economic times.  With real economic growth.  And not a speculative bubble.  For there was nothing speculative about all of this technology becoming a part of our way of life.

Of course the technology wasn’t perfect.  The coal-burning locomotives belched black smoke and ash wherever they went.  Which wasn’t all that bad in the open country where a train or two passed.  But it was pretty dangerous in tunnels.  Which had to be short lest they suffocated their passengers.  (One of the reasons why all subways use electric trains).  Making for some long and winding railroads in mountainous terrain.  To go around mountains instead of under them.  Slowing trains and increasing travel time.  And they were pretty unpleasant in the cities.  Where the several rail lines converged.  Bringing a lot of coal-burning locomotives together.  Creating a smoky haze in these cities.  And leaving a layer of ash everywhere.  The cleaner diesel-burning locomotives changed that.  The diesel electric locomotive could pull a train cross country and into the heart of a city with a minimal amount of pollution.  As long as they kept their engines from burning rich.  Which they would if they operated them with dirty air filters.  Reducing fuel efficiency by having the air-fuel mixture contain too much fuel.  And causing these engines to belch black smoke.  Similar to diesel trucks running with dirty air filters.

Airplanes can travel between Two Points in a Direct Line at Faster Speeds than a Train or Bus with Minimal Infrastructure

Trains shrunk our country.  Brought distant cities together.  Allowing people to visit anywhere in the continental United States.  And the railroads profited well from all of this travel.  Until two later developments.  One was the interstate highway system.  That transferred a lot of freight from the trains to trucks.  As well as people from trains to buses and cars.  And then air travel.  That transferred even more people from trains to airplanes.  This competition really weakening railroads’ profits.  And pretty much put an end to passenger rail.  For people used the interstate highway system for short trips.  And flew on the long ones.  Which was quicker.  And less expensive.  Primarily because airplanes flew over terrain that was costly to avoid.

Highways and railroads have to negotiate terrain.  They have to wind around obstacles.  Go up and down mountainous regions.  Cross rivers and valleys on bridges.  Travel under hilly terrain through tunnels.  And everywhere they go they have to travel on something built by man.  All the way from point A to point B.  Now trucks, buses and cars have an advantage here.  We subsidize highway travel with fuel taxes.  Trucking companies, bus lines and car owners didn’t have to build the road and infrastructure connecting point A to point B.  Like the railroads do.  The railroads had to supply that very extensive and very expensive infrastructure themselves.  Paid for by their freight rates and their passenger ticket sales.  And when there were less expensive alternatives it was difficult to sell your rates and fares at prices high enough to support that infrastructure.  Especially when that lower-priced alternative got you where you were going faster.  Like the airplane did.

Man had always wanted to fly.  Like a bird.  But no amount of flapping of man-made wings got anyone off the ground.  We’re too heavy and lacked the necessary breast muscles to flap anything fast enough.  Not to mention that if we could we didn’t have any means to stabilize ourselves in flight.  We don’t have a streamline body or tail feathers.  But then we learned we could create lift.  Not by flapping but my pushing a curved wing through the air.  As the air passes over this curved surface it creates lift.  Generate enough speed and you could lift quite a load with those wings.  Including people.  Cargo.  Engines.  And fuel.  Add in some control elements and we could stabilize this in flight.  A tail fin to prevent yawing (twisting left and right) from the direction of flight.  Like a weathercock turns to point in the direction of the wind.  And an elevator (small ‘wing’ at the tail of the plane) to control pitch (nose up and nose down).  Ailerons correct for rolling.  Or turn the plane by rolling.  By tipping the wings up or down to bank the airplane (to turn left the left aileron goes up and the right aileron goes down).  And using the elevator on the take-off roll to pitch the nose up to allow the plane to gain altitude.  And in flight it allows the plane to ascend or descend to different altitudes.  Put all of this together and it allows an airplane to travel between points A and B while avoiding all terrain.  In a direct line between these two points.  At a much faster speed than a train, bus or car can travel.  And the only infrastructure required for this are the airports at points A and B.  And the few en route air traffic controllers between points A and B. Which consisted of radar installations and dark rooms with people staring at monitors.  Communicating to the aircraft.  Helping them to negotiate the air highways without colliding into other aircraft.  And air travel took off, of course, in the 1920s.  The Roaring Twenties.  Those glorious transformative years.

Refined Petroleum Products have Large Concentrations of Energy and are the Only Fuel that allows Air Travel

The most expensive cost of flying is the fuel cost.  The costlier it is the costlier it is to fly.  Not so for the railroads.  Because their fuel costs aren’t the most expensive cost they have.  Maintaining their infrastructure is.  They can carry incredible loads cross country for a small price per unit weight.  Without swings in fuel prices eating into their profits.  Making them ideal to transfer very large and/or heavy loads over great distances.  Despite dealing with all the headaches of terrain.  For neither a plane nor a truck can carry the same volume a train can.  And heavier loads on a plane take far greater amounts of fuel.  This additional fuel itself adding a great amount of weight to the aircraft.  Thus limiting its flight distance.  Requiring refueling stops along the way.  Making it a very expensive way to transport heavy loads.  Which is why we ship coal on trains.  Not on planes.

Trains are profitable again.  But they’re not making their money moving people around.  Their money is in heavy freight.  Iron ore.  Coke.  And, of course, coal.  To feed the modern industrial economy.  Stuff too heavy for our paved roads.  And needed in such bulk that it would take caravans of trucks to carry what one train can carry.  But even trains can’t transport something in enough bulk to make it cost efficient.  Refined petroleum.  Gasoline.  Diesel.  And jet fuel.  For these we use pipelines.  From pipelines we load gas and diesel onto trucks and deliver it to your local gas station.  We run pipelines directly to the fuel racks in rail yards.   And run pipelines to our airports.  Where we pump jet fuel into onsite storage tanks in large fuel farms.  Which we then pump out in another set of pipelines to fueling hydrants located right at aircraft gates.

These refined petroleum products carry large concentrations of energy.  Are easy to transport in pipelines.  Are portable.  And are very convenient.  Planes and trains (as well as ships, busses and cars) can carry them.  Allowing them to travel great distances.  Something currently no renewable energy can do.  And doing without them would put an end to air travel.  Greatly increase the cost of rail transport (by electrifying ALL our tracks).  Or simply abandoning track we don’t electrify.  Making those far distant cities ever more distant.  And our traveling options far more limited than they were in the 1920s.  Turning the hands of time back about a hundred years.  Only we’ll have less.  And life will be less enjoyable.

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