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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Boeing 787 Dreamliner, Fuel Costs, Electric Systems, Auxiliary Power Unit and Lithium-Ion Batteries

Posted by PITHOCRATES - January 23rd, 2013

Technology 101

Auxiliary Devices reduce the Power Output of the Engine available to Drive a Car Forward

If you’re middle age (or old) you may remember looking under the hood of a car.  When you could see things.  In the days of rear-wheel drive cars and big engines.  The front of the engine had a power takeoff pulley attached to the crank shaft.  The thing the pistons spun when it converted reciprocal motion into rotational motion.  Wrapped around that pulley were a lot of belts.  Sometimes three or more.  They transferred the rotational motion of the crankshaft to auxiliary devices.

These devices included the water pump that pumped engine coolant to remove the heat of combustion.  An alternator to generate electric power.  A power steering pump to make steering easier.  An air pump to inject air into the exhaust system to help complete the combustion process to reduce emissions.  (An electronic air pump has since replaced this belt-driven device.)  And an air conditioner compressor.  All of these devices reduce the power output of the engine available to drive the car forward.  Requiring more fuel.

Today’s cars have a lot more stuff under the hood.  Engines are often mounted transversely.  And the multiple belts have been replaced with one serpentine belt that winds around all of these auxiliary devices.  And engines are smaller.  With on board computers that maximize the power output of smaller engines.  That drive lighter cars.  But one thing hasn’t changed.  When you turn on the air conditioning you can still hear the engine labor under the additional load.  While burning more fuel.

The Boeing 787 Dreamliner can do what other Planes can do while Burning less Fuel

In the airline industry the greatest cost is fuel.  So anything that allows airlines to burn less fuel greatly interests the airlines.  And it’s why pilots do careful calculations to determine how much fuel to carry.  That is, to determine the absolute minimum amount of fuel to carry.  If it were up to pilots they’d top off the fuel tanks.  But if they did that the airlines could not operate profitably.  Because you have to burn fuel to carry fuel.  And the more fuel you carry the more you have to burn.  Increasing your fuel costs to the point an airline loses money.  Especially if you’re landing with a lot of fuel in your tanks.  So pilots load less fuel than they would want.  Because to get a paycheck their company has to operate at a profit.  But it doesn’t stop there.  Not for aircraft designers.

Designers have been using more plastic in airplanes.  Because plastic is lighter than metal.  So engines can burn less fuel.  These composite materials are also stronger than metal.  So less of them can replace equivalent metal components.  So engines can burn less fuel.  Airlines have also been charging more for carry-on luggage.  In part to help offset their rising fuel costs.  And in part to encourage people to carry less onto the airplane.  So engines can burn less fuel.  Then Boeing raised the bar on burning less fuel.

The Boeing 787 Dreamliner is a remarkable design.  Remarkable because it delivers what airlines want most.  An airplane that can do what other planes can do.  But does it while burning less fuel.  Boeing has used more composite material than any other manufacturer.  Making the 787 the lightest in its class.  And lighter things allow engines to burn less fuel.  But Boeing did more than just make the airplane lighter.  They used electric systems to replace hydraulic and pneumatic systems normally found on an airplane.

The 787 Dreamliner uses Lithium-Ion Batteries to start their Auxiliary Power Unit

Hydraulic and pneumatic systems bleed power from the aircraft engines.  As the engines drive pumps and compressors for these systems.  By converting these to electric systems more of the power of the engines goes to producing thrust.  Which means they burn less fuel to fly to their destination.  They even replaced the pneumatic starters (that spin the engines during starting) with a combination electric starter/generator.  Saving weight.  And reducing the complexity.  By replacing two parts (pneumatic starter and electric generator) with one (combination starter/generator).

To start the aircraft engines they first start the auxiliary power unit (APU).  The APU is typically mounted near the tail of the aircraft.  The APU provides power, lights, heating, air conditioning, etc., when the main engines aren’t running.  Some provide back up power (electric and pneumatic) should the main engines fail in flight.  The APU also drives an air compressor to provide the pneumatic power to spin the main engines for starting.  Going to all electric systems (except for the engine anti-ice system) removes the air compressor from the APU.  Reducing the weight.  And they further reduced the weight by making another change.  To the battery that starts the APU.

The 787 uses lithium-ion batteries.  Which can provide the same power larger batteries of different technologies can provide.  As lithium-ion batteries has a very high energy density.  But with great energy density comes great heat.  Some of these batteries have actually caught fire.  In electric cars.  Laptop computers.  Cell phones.  Even in Boeing 787 Dreamliners.  They’re not sure why.  And they’ve grounded the fleet until they figure out why.  It may be because they are overcharging.  Or that there are internal shorts causing a thermal runaway (releasing all the stored energy at one time).  Or the caustic electrolyte is leaking and causing a fire.  Until they determine what the problem is the 787 will remain grounded.  Making it very difficult to enjoy the cost savings of that remarkable design.

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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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Kerosene, Jet Fuel, Lockheed Constellation, Boeing 707, Boeing 747-400, Newton’s Third Law of Motion, Turbojet and Fan Jet

Posted by PITHOCRATES - October 3rd, 2012

Technology 101

The only way to make Flying Available to the General Public is to put as many People as Possible on an Airplane

Refined petroleum products have made our lives better.  We have gasoline to drive wherever we want.  We have diesel fuel to transport things on ships and trains like petroleum oil, iron ore, coal, food, medicine, smartphones, coffee, tea, wine, scotch whisky, bourbon whiskey, beer, fresh fish, sushi, etc.  Pretty much everything we buy at a store or a restaurant got there on something powered by diesel fuel.  And sometimes kerosene.  If it must travel fast.  And if it does then it finds itself on a jet aircraft.

Today aviation has shrunk the world.  We can order a new smartphone sitting on a shelf in California and have it the next day in New York.  We can even travel to distant countries.  Some in the time of a typical working day.  Some a half a day or longer.  When but a 100 years earlier it took a couple of weeks to cross the Atlantic Ocean.  While 200 years ago it took a couple of months.  We can travel anywhere.  And get there quickly.  Thanks to the jumbo jet.  And not just the super-rich.  Pretty much anyone today can afford to buy a plane ticket to travel anywhere in the world.  And one thing makes this possible.  The jet engine.

Airplanes are expensive.  So are airports, air traffic control and jet fuel.  Airlines pay for all of these costs one passenger at a time.  Their largest cost is their fuel cost.  The longer the flight the greater the cost.  So the only way to make flying available to the general public is to put as many people as possible on an airplane.  Dividing the total flying cost by the number of passengers on the airplane.  This is why we fly on jumbo jets for these longer flights.  Because there are more people to split the total costs.  Lowering the cost per ticket.  Before the jet engine, though, it was a different story.

The Boeing 747-400 can take up to 660 Passengers some 7,260 Miles at a Speed of 567 MPH

One of the last intercontinental propeller-driven airplanes was the Lockheed Constellation.  A plane with four (4) Wright R-3350-DA3 Turbo Compound 18-cylinder supercharged radial engines putting out 3,250 horsepower each.  Which is a lot considering today’s typical 6-cyclinder automobile engine is lucky to get 300 horsepower.  No, the horsepower of one of these engines is about what one modern diesel-electric locomotive produces.  So these are big engines.  With a total power equal to about four locomotives lashed up.  Which is a lot of power.  And what does that power allow the Constellation do?  Not much by today’s standards.

In its day the Lockheed Constellation was a technological wonder.  It could take up to 109 passengers some 5,500 miles at a speed of 340 mph.  No bus or train could match this.  Not to mention it could fly over the water.  Then came the age of the jet.  The Boeing 707 being the first largely successful commercial jetliner.  Which could take up to 189 passengers some 6,160 miles at a speed of 607 mph.  That’s 73.4% more passengers, a 78.5% faster speed and a 14.1% longer range.  Which is an incredible improvement over the Constellation.  But nothing compared to the Boeing 747-400.  Which can take up to 660 passengers (506% more than the Constellation and 249% more than the 707) some 7,260 miles at a speed of 567 mph.

Now remember, fuel is the greatest cost of aviation.  So let’s assume that a intercontinental flight costs a total of $75,000 for each plane flying the same route.  Dividing that cost by the number of passengers you get a ticket price of approximately $688, $397 and $114 for the Constellation, the 707 and the 747-400, respectively.  So you can see the advantage of packing in as many passengers as possible into an airplane to lower the cost of flying.  Which is why the jumbo jets fly the longest routes that consume the most fuel.  And why we no longer fly propeller-driven aircraft except on short routes to airports with short runways.  These engines just don’t have the power to get a plane off the ground with enough people to reduce the cost of flying to a price most people could afford.  Only the jet engine has that kind of power.

The Fan Jet is basically a Turbojet with a Large Fan in front of the Compressor

Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction.  Think of a balloon you just blew up and are holding closed.  If you release your hold air will exit the balloon in one direction.  And the balloon will move in the opposite direction.  This is how a jet engine moves an aircraft.  Hot exhaust gases exit the engine in one direction.  Pushing the jet engine in the opposite direction.  And because the jet engines move the plane moves.  With the force of the jet engines transferred via their connection points to the aircraft.  The greater the speed of the gas exiting the jet the faster it will push a plane forward.

The jet engine gets that power from the continuous cycle of the jet engine.  Air enters one end, gets compressed, enters a combustion chamber, mixes with fuel (kerosene), ignites, expands rapidly and exits the other end.  The hot (3,632 degree Fahrenheit) and expanding gases pass through and spin a turbine.  Then exit the engine.  The turbine is connected to the compressor at the front of the engine.  So the exhaust gases spin the compressor that sucks air into the engine.  As the air passes through the compressor it compresses and heats up.  Then it enters the combustion chamber and joins fuel that is injected and burned continuously.  Sort of like pouring gas on a burning fire.  Only enormous amounts of compressed air and kerosene are poured onto a burning fire.  As this air-fuel mixture burns it rapidly expands.  And exits the combustion chamber faster than the air entered it.  And shoots a hot stream of jet gas out the tail pipe.  Which produces the loud noise of these turbojets.  This fast jet of air cuts through the surrounding air.  Resulting in a shear effect.  Which the next generation of jet engines, the fan jet, greatly reduces.

The fan jet is basically a turbojet with one additional feature.  A large fan in front of the compressor.  These are the big engines you see on the jumbo jets.  They add another turbine inside the jet that spins the fan at the front of the engine.  Which feeds some air into the compressor of what is basically a turbojet.  But a lot of the air this fan sucks in bypasses the turbojet core.  And blows directly out the back of the fan at high speed.  In fact, this bypass air provides about 75% of the total thrust of the fan jet.  Acting more like a propeller than a jet.  And as an added benefit this bypass air surrounds the faster exhaust of the jet thereby lessening the shear effect.  Making these larger engines pretty quiet.  In fact a DC-9, an MD-80, a 707 or a 727 with standard turbojets are much louder than a 747 with 4 fan jets at full power.  They’re quieter.  And they can push a lot more people through the air at incredible speeds over great distances at a reasonable price per passenger than any other aircraft engine.

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