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The Blow & The Birds

Ever wondered how jet planes hurtle through the skies at about 80 per cent the speed of sound? Captain Lim Khoy Hing explains the ‘Suck, Squeeze, Bang and Blow’ theory, as well as threats to this system.

Words: Captain Lim Khoy Hing

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,The Blow & The Birds,Sooty Terns In The Air

SUCK, SQUEEZE, BANG AND BLOW 

The component responsible for this ‘suck’ function is the fan in the engine intake. This can pull in a large volume of air and direct it into the compressor, which does the ‘squeezing’. More on the squeezing later! 

     A typical commercial jet engine sucks in 1,200 kgs of air per second during take-off. In other words, it could empty the air in a squash court in less than a second! At lower power, the suction can be very lethal too. It can suck in anything located near the front of the engine – be it humans (one mechanic at Texas in 2006!), cargo containers, traffic cones or other objects. 

     The compressor ‘squeezes’ the incoming air through a series of spinning blades in stages. The more stages it has, the higher the compression-ratio and hence, its efficiency. For example, if the compression ratio is 40:1, that means that the pressure of the air at the end is over 40 times that of the air that enters the compressor. 

     The ‘bang’ is produced inside the combustion chamber. Very simply, the combustor is just like a butane cigarette lighter. The compressed air is ignited here. Gases that form expand rapidly, get exhausted and blown through the rear of the combustion chambers creating thrust, typically 110,000 pounds of force in some jet engines!  

     In comparison, the piston engine of your car has also another almost simplistic explanation: Suck, squeeze, burn and blow – with ‘burn’ replacing the ‘bang’. In a car, the final effect of the process turns the crankshaft, ultimately moving the wheels. On a jet engine, the final effect of ‘blow’ is the thrust – similar to the force of releasing the air in a balloon causing it to zoom away.

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,The Blow & The Birds,The Runways,Parking Aprons

POWER OF JET SUCTION 

Now that you know the enormous suction power of the jet engine, never, never stray towards a live jet engine!  To prevent costly damage to jet engines, airlines and aviation authorities put many precautions in place. Amongst them, the manoeuvring area of the plane from the moment it moves from the parking position to the take-off runway has to be spotlessly maintained to prevent debris from being ingested by the engines.  

“THE RUNWAYS AND PARKING APRONS ARE REGULARLY CHECKED TO ENSURE THEY ARE FREE FROM PIECES OF BROKEN CONCRETE, MATERIALS FROM CABIN CLEANING, DETACHED WHEELS FROM LUGGAGE AND OTHER UNWANTED OBJECTS.”

     The runways and parking aprons are regularly checked to ensure they are free from pieces of broken concrete, materials from cabin cleaning, detached wheels from luggage and other unwanted objects. Even small objects can sometimes cause catastrophic damage if sucked into the engine. As part of stringent testing for all new planes, FAA (Federal Aviation Administration) requires that all new engine designs pass a test that includes withstanding the firing of a chicken carcass into a running engine using a small cannon; the impact of the chicken carcass must not affect the operation of the plane. 

     On July 25, 2000, the crash of the Air France Concorde at Charles de Gaulle International Airport in Paris was caused by a metal object found on the runway. This was a piece of debris from part of a Continental Airlines DC-10 plane that had taken off four minutes earlier. This highlights the need for diligent debris removal from the runway and its surrounding areas. 

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,The Blow & The Birds,The Runways,Jet Engine,enormous suction power,damage engine

The enormous suction power of a jet engine can cause serious damage. Never, never stray towards a live jet engine.

BIG BIRDS, BAD HAZARD  

Large birds are considered dangerous flying objects to aircraft engines. On November 20, 1975, a Hawker Siddeley HS 125 plane taking off at Dunsfold aerodrome south of London flew through a flock of birds after lifting off and lost power in both the engines. 

     The crew landed the aircraft back onto the runway, but it overran the end and crossed a road. The aircraft struck a car on the road, killing its six passengers.

     On November 17, 1980 a Hawker Siddeley Nimrod jet plane crashed shortly after taking off from a Royal Air Force station north of Scotland. It flew through a flock of Canada geese, causing three of its four engines to fail. 

     Another famous bird strike accident happened on January 15, 2009 where a US Airways flight flew into a flock of Canada geese and suffered a double engine failure. The pilot, Captain ‘Sully’ safely ditched the plane on the Hudson River, saving all 155 lives on board.

REDUCING BIRD STRIKE THREAT 

Bird strikes account for more than two strikes per 10,000 movements and are becoming even more frequent. Wilbur Wright was the first pilot to record a bird strike in 1905, but the most newsworthy one was caused by Canada geese that downed the Airbus A320 plane into the Hudson River.  

     A bird detection system known as BirdWize was recently launched. This is a software product for reducing bird strikes by more effective tracking of ground-level bird threats. 

ERADICATING LOOSE OBJECTS 

Loose objects (also known in the aviation industry as FOD or Foreign Object Damage) cost the aviation industry around USD13 billion per year in direct and indirect costs.  

     Hence, things such as tools and bolts mistakenly left behind by mechanics or dislodged passengers’ baggage wheels are some of the typical hazards to jet engines. 

     As a result, you may sometimes see (in smaller airfields) sweepings being conducted before flight operations begin. A line of personnel may walk shoulder-to-shoulder along open surfaces searching for and removing loose objects. 

     The U.S. Federal Aviation Administration (FAA) and International Civil Aviation Organization (ICAO) require a daily, daylight inspection of airplane manoeuvring areas and removal of loose objects. 

PRE-EMPTING DAMAGE 

Flying is safe because the airline industry makes a lot of effort to eradicate costly damages caused by loose objects on the ground or in the air. 

     On November 15, 2013, Boston Logan International Airport became the first airport in the US to install a system that automates the job of identifying objects that may damage an aircraft during take-off or landing. 

     So, be kind and proactive. You can also participate in flight safety. Pick up any loose objects – a detached luggage wheel, shoe studs or a metal nut – you come across as you make your way to the plane on an open tarmac. You could save lives with that small, conscientious act. 


From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,AirAsia X Simulator Flight Instructor,Captain Lim Khoy Ling,AirAsia Airbus A320,AirAsia X A330/A340 pilot

     Captain Lim Khoy Hing is a former AirAsia Airbus A320 and AirAsia X A330/A340 pilot who also used to  fly the Boeing 777. He has logged a total of more than 25,500  flying hours and is now a Simulator Flight Instructor with AirAsia X. In his spare time, he shares his opinion on aviation issues with others. For more air travel and aviation stories, check out his website, ‘Just About Flying’ at  www.askcaptainlim.com.

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,AirAsia X Simulator Flight Instructor,Captain Lim Khoy Ling,AirAsia Airbus A320,AirAsia X A330/A340 pilot,Life in the Skies,Just About Flying,AirAsia Megastore

     Capt. Lim’s first book, Life in the Skies, has just been released. You can purchase it onboard all AirAsia and AirAsia X flights, AirAsia Megastore kiosk at LCCT Sepang or online at AirAsia Megastore at www.airasiamegastore.com/life-in-the-skies.html. It is also available in all major book stores in Malaysia and Singapore. Enjoy the great collection of articles, anecdotal stories and observations of this veteran aviator in this book.

RESOURCES:

  • http://www.phooeytofear.com/ Neil Shearing, Ph.D. (Phooey T

    Thanks for the article, Captain Lim. I didn’t realise quite how powerful those jet engines were.