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About engine failures
An engine failure was one of the most typical exceptional circumstances in the era of piston engines–to such an extent that the uneven operation of an engine was not exceptional. Cylinder changes could be carried out by the local mechanic in the open air, and adjusting the ignition of an unevenly running engine was almost a daily routine. As a result, the possibility of total engine failure was already taken into account in the performance calculations for takeoff, and pilots were trained in how to operate in case of engine failure.
The probability of engine failure decreased significantly with the introduction of jet engines. This was because the pistons moving back and forth under major loads were replaced with disks moving more evenly–the rotors of the compressor and the turbine. At the same time, the number of valves and other moving parts was significantly reduced. Thrust increased hugely, and margins to terrain in case of engine failure were markedly bigger. Regardless of all this, we still prepare for engine failures with the conservative approach we’ve learned. Takeoff is the most critical stage in terms of engine failure, but it has to be considered in other stages of the flight as well. Performance calculations are made by the pilots before each takeoff based on the prevailing conditions and the takeoff weight. We make preparations that, in case of engine failure, we can either stop the plane on the remaining runway, or continue the takeoff with one engine out and clear the obstacles ahead with the safety margins specified by the authorities. Cockpit procedures in case of engine failure are revised every day before the first takeoff of the day. The flight path in continued takeoff (which may, depending on the obstacles, be something other than just straight ahead) is discussed before each takeoff. The skills of the pilot are checked in the simulator at least twice a year. I can confirm that these matters are rooted deep in the minds of pilots, although with the current engines, the likelihood of an engine failure during a pilot’s entire career is less than one event. The probability of a failure in which the engine shuts down in a controlled manner before major failures occur (In Flight Shut Down – IFSD) is around one / one million flight hours, and the likelihood of a total engine failure is at least ten or perhaps even one hundred times less likely than that. Giving an exact number is difficult as reliability continues to improve with increasing numbers of non-failure flight hours.
This year, Finnair has had a couple of events in which an engine has been shut down during flight. In twin engine planes, this means landing at the nearest suitable airport for safety reasons. We don’t continue to fly with just one engine. In many cases, passengers don’t even notice that an engine has been shut down until the commander has made an announcement. The Safety investigation authority doesn’t investigate such events either–that’s how harmless they are. In all recent events, the pilots have noticed the situation even before receiving alerts from the plane’s warning systems. Such events do, however, trigger the company’s internal Safety Management System (SMS), which is based on the EU regulation. We determine, for example, if there are any common denominators in such cases; whether maintenance, for example, has been carried out according to the requirements, whether the spare parts and materials used meet the requirements, etc. All of this is done in close cooperation with the engine manufacturers, as it is also in their interests that the engines operate without problems.
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Fear of flying is like riding a roller coaster
I have received a lot of comments and messages on my blog about the fear of flying. I had been meaning to write about the topic for a long time, but I hadn’t found the right way to approach it. In her comment, a reader of mine compared flying to a roller-coaster; that’s where I got the idea for this article.
Fear is wisdom. If we didn’t have a sense of fear, our species would have gone extinct long ago. Evolution has made sure that fear – that powerful feeling we have learned from the experiences of our ancestors – is encoded in our genome. Many phobias are still inherited in their original form today. For example, some people are afraid of snakes, while others have a fear of spiders. Most people have a primitive reaction at the very least when a tarantula creeps along their arm. Evolution is an ongoing process, so it is only natural that individual experiences, in addition to inherited ones, also influence fear. These experiences can also be a tool for managing fear.
Fear is a feeling a person experiences subjectively. When asked about the reasons for fear, it may be difficult for someone to explain why they are afraid of snakes, for example, but not spiders. The same is true when it comes to the fear of flying. Often those who fear flying do not give a clear reason, but instead they begin to list different frightening scenarios or simply say that “the plane might fall out of the sky, or something”. A common factor is often the fear that something bad will happen to oneself or one’s child. For this reason, becoming a mother might trigger a fear of flying. (Please don’t stop here, new mothers, keep on reading!)
So, people have a natural need to feel safe.
On a roller-coaster and on a plane, people seek safety by white-knuckling the edge of the car or the arm rest, as though it were the tree branch one might fall from and become a predator’s meal. On a roller-coaster, then, the brave ones are the ones with their hands up in the air. It’s also a sign for others – body language – saying “I’m not afraaaaaaaaid!”.
People also turn to others for safety. The brakeman is wonderful – a teenage girl’s dream. Outside of the amusement park, it could be a police officer or firefighter. A person who is seen as brave and safe is attractive. On this man, even weathered coveralls look good. Add mating instinct into the mix and you’ve found an ideal candidate for a husband. With him, you will be guaranteed a life of security.
On a plane, those seeking a feeling of safety can turn to the cabin crew, as well as the pilot. Cabin crew members are very knowledgeable and know how to relate to the fear of flying. But the best person to turn to for safety may be your spouse or friend sitting next to you. One doesn’t need to know anything about flying if he/she knows how to emnolden others and to give them a sense of security.
Are brakemen, police officers and firefighters brave? Am I brave myself? Brave is usually a word we use to describe another person. He or she does something that I feel is brave. They most likely do not think of themselves as brave when doing their work. I think they are probably thinking that they are just doing their job.
So why do I go on roller-coasters? I think it would be foolhardy to go to an amusement park in the capital of a country where corruption puts ticket revenues right into the owners’ pockets, leaving the equipment rusty, the place dirty and some of the roller-coaster cars without wheels. But I do dare to go on the roller-coaster at Linnanmäki in Helsinki, even if it scares me a little. I’m not afraid to join the queue to be frightened, because I believe that the amusement park rides have been safely designed and inspected. And, after all, there’s still the brakeman! Subconsciously, I understand that it is safe. The attraction of contraptions like roller-coasters is, however, based on the idea that customers feel they are conquering their fear. I risk going on a ride in which the car creakingly climbs up to dizzying heights and dives down from there at a furious pace towards the ground, only to veer off after the next bend into a frighteningly dark tunnel. After the ride, I step out of the car with my legs shaking slightly from the adrenaline rush. I conquered my fear. I was brave.
After having gone on the ride another twenty-two times that evening, there is no longer that rush of adrenaline. Boring! The brakeman is probably bored too. Should I try going on the adults’ ride next? I realise then that the fear was relative, and my bravery questionable. I have gotten rid of my original fear.
When boarding a flight, you do not need to gather extra courage either. You have made the decision to leave and you recognise that air travel is one of the safest things you can do. In order to be brave, all you have to do is…
Let go of your fear and maybe put your hands up in the air as a sign to others – “I’m not afraid!”.
And enjoy it this time, the next time it might already be boring.
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Rajmund Kozma was worried about what would happen if a Total Glass Cockpit Blackout, i.e. a simultaneous blackout of all electronic display units (CRT or LCD displays), were to occur during a flight. This is an understandable concern as there have been some such incidents.
Airbus, the supplier of Finnair’s fleet, has recorded 50 incidents in which three or more of the six main display units (DUs) have blacked out simultaneously durintg the last 25 years. The blackout of all six display units has occurred only seven times.
In an aircraft, the likelihood of a major electronic defect is in the range of 10-5, or one failure per 100,000 flight hours. In most incidents where all display units have blacked out, the reason has been a double defect – two defects happening at the same time. As the likelihood of such a defect should be extremely small, the electric system needed modification. The conclusion was that the main reason was the fault tolerance of one of the main buses (AC 1). In May 2007, Airbus published Service Bulletin SB A320-24-1120,9 which included a request to make a modification (37317). The modification improved the ability of the aircraft’s electric system to adjust to any failures in the AC 1 bus coupler.
Another significant point is that none of these 50 incidents led to a disaster. In most blackout cases, only half of the display units have blacked out. In this case, one of the pilots has all display units available. If all display units black out, the plane can be flown to the closest airport by using the so-called standby instruments on the captain’s side of the cockpit. The standby instruments consists of an artificial horizon, airspeed and altitude indicators as well as a fluid compass. The instruments get its data from different sensors than the main displays do and the required electricity comes directly from batteries.
An aircraft could depart to a commercial flight even if one of the six display units did not function. With the cockpit switches, data related to the current flight phase can be fed to the remaining display units.
The cause of the blackout of several display units is likely related to power supply. In a two-engine aircraft, both engines have generators which can supply power independently to all systems in the aircraft. The electric system is roughly divided into two separate systems. In case of a defect, one generator can feed power to both sides. However, if there is a short-circuit or a similar situation, the other side (or at least the single defective bus) must be kept separated. In this case, some monitoring instruments are left without power. Nevertheless, as for their power supply, all devices using AC and DC current have been divided logically so that the flight can be continued safely. For this reason, an aircraft always has at least two of all essential devices. If there is a defect in both generators, power supply can be ensured with the so-called APU (Auxiliary Power Unit), which is located in the tail cone of the aircraft. Even if the APU was out of order, there is still two options: a generator can be extended from the fuselage, generating energy in a windmill-like manner. In addition, some devices can be powered directly by batteries. Depending on the type of the aircraft, there are two or three sets of main batteries.
Consequently, the likelihood of being a passenger in an aircraft experiencing a total cockpit blackout is very, very small. And even if such blackout occurred, it would hardly cause a disaster.
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Airplane: another technical gadget
Airplanes, like all technical gadgets, face bugs, faults and defects from time to time. When preparing for a flight, the crew is notified of any defects on the airplane and the defects are compared to the so-called minimum equipment list which includes all the devices and equipment that must be functional. For example, of the three VHF radios used to communicate with air traffic control, the so-called “radio number two” (VHF-2) can be out of order in our Airbus planes for three days provided that the VHF-1 and VHF-3 are fully functional (usually just one radio is used at a time).
Some defects require technical and/or operational procedures, and the captain is responsible for overseeing that these procedures are carried out. The list is quite conservative. For example, if the light of the emergency exit in the cabin is not working, only as many passengers will be allowed on the aircraft as would be approved by authorities when the whole emergency exit is out of order. Even though, in case of an emergency, the door would function just as it should.
Naturally, a defect can appear during flight. In order for the defects not to risk flight safety, every important device has a back-up system and the most vital ones even have back-up systems for the back-up systems.
Here’s an example: landing gear. Landing gear always has two sets of tyres so it won’t be a disaster even if a tyre deflates or there is a problem with a brake. The landing gear also has two detector systems showing the position of the gear. This means that a light or sensor defect will not cause unnecessary emergency preparations in the cabin.
The landing gear also has at least two operating systems. If the gear cannot be lowered with the normal hydraulic system, it can also be dropped down manually. On the other hand, there is only one nose gear steering system as it is not a necessity for flight safety. Landing can be done in an absolutely normal manner even if the nose gear steering system is defective. The only thing is that the plane cannot taxi to the parking spot without assistance. If the way from the runway to the taxiway is a gentle turn (so called high speed exit), the aircraft can be steered away from the runway used by other aircraft using aerodynamic controls (rudder) and asymmetrical braking.
In case something fails when the plane is in the air, the flight crew will go through an electronic or paper check list. With the help of the list, they will try to reset the system. If resetting does not help, the crew will go through the list so that every influential matter will be taken into account. In sudden situations, the checking of the lists will start only after the “known by heart” items. All these are practised annually in a simulator. Also, the cabin crew go through yearly training regarding what to do in case of an emergency.
One of the challenges of being a pilot when something is not working as it should, is that you cannot just park your plane on a cloud for further investigations and democratic decision-making. Decisions have to be made in a changing environment where the pilot must take into account the type of the defect, weather, sufficiency of fuel, the lengths of the runways at alternate airports, direction of the wind and many other things. Sometimes the passengers must just accept the pilot’s decisions, for example landing in an alternate airport. Of course, when the situation is over, the goal is to get every passenger to their destination with minimum delay.
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On spherical navigation
Juhani Suntioinen was looking for a story about long-distance navigation, so here it comes.
Commercial aircraft are normally equipped with two GPS receivers, so on a long-distance flight we mainly navigate with the aid of GPS. Although we would able to fly the shortest and most direct route to the destination, the route still needs to be planned so that it follows airways. This is done mainly because of air traffic control reasons. Airways consist partly of navigation beacons, such as VOR- and ND- beacons. By beacon I refer to a group of antennas – not to a beacon of a traditional marine lighthouse. These ground-based navigation beacons ensure safety when a GPS signal is not available for one reason or another (that is: there is a malfunction in the GPS system or the aircraft).
Most of the waypoints are beaconless points, normally with a five-letter name. Typically they are located at the intersection of two airways or at the boundary of air traffic control areas. Consequently, it is possible to use names instead of coordinates. This makes planning and radio traffic faster and decreases the possibility of human error. While en route, we try to find short cuts from one waypoint to another in order to save time and fuel and reduce emissions.
GPS navigation devices always follow a great-circle route. For many of our readers, this concept may be a bit unfamiliar so a little summary is probably in order.
As we know, the Earth is a sphere. A spherical surface cannot be presented on a two-dimensional map without errors. Depending on the map projection, the map of the Earth distorts angles, shapes, distances or surfaces. The map that is perhaps most generally used at school and in press is based on the Mercator projection where all meridians and parallels are perpendicular to each other. However, this projection exaggerates the size of circumpolar areas: Finland is nearly the size of India and Antarctica is bigger than all the other continents combined. On a Mercator map, the shortest distance, i.e. the great circle line, becomes distorted and bends towards the poles as the spherical surface is “stretched” at the poles when drawing the map. For this reason, in aviation we use gnomonic maps in circumpolar areas and for other areas Lambert conformal conic projections where a great circle is nearly straight. If you have a round globe map at home, it is easy to determine a great circle between two points by using a piece of thread, for instance. So, the word “great circle” is not very descriptive as it refers to the shortest distance – not the greatest: if one were able to drive along it with a car, one would not need to turn the steering wheel. Consequently, it is not a circle (except when thinking of it as a circle around the centre of the sphere). I wonder who came up with such a monstrous word. I suggest that it be replaced with “shortline”!
As meridians converge at the poles and consequently are not parallel as in the Mercator projection, the direction in relation to the great circle changes accordingly. The closer to the poles one is flying, the greater the change in the actual direction. When flying to the north and the south, there naturally is no change – and the same applies to flying to the east or the west on the equator. When looking from Helsinki, the great circle network is rather surprising. For instance, the great-circle route from Frankfurt to Tokyo goes over Helsinki. Finnair’s long-haul traffic strategy is based on this fact. We hold a key position between Central Europe and Asia. You can draw different great circles here, for instance.
When measuring on a Mercator map, the first thought might be that the fastest route to Tokyo is to take the direction of St. Petersburg (108o) and then fly over Russia, northern Kazakhstan, Mongolia, north-eastern China and North Korea, altogether 8,782 kilometres to the destination. However, Finnair heads for Joensuu (051o ) and flies the entire route over Russia directly to Tokyo. The distance is “only” 7,849 kilometres. The difference is 933 kilometres! What do you think, which route gets you there fastest?
The longer the distance in the east-west direction, the more surprising the great circle. For instance, the great circle from Singapore to New York goes to the north (357o) over Cambodia towards Chongqing in China, from there through Mongolia and Russia, near the North Pole to Canada, arriving to New York from the north. A less knowledgeable person would head towards the southern tip of India, over Yemen, across Sahara and over the Canary Islands and the Atlantic Ocean to New York. Via this route the distance would be 3,160 kilometres longer. You can see the differences between routes for yourself here, for instance.
In reality, a flight is carried out along airways following a great-circle route as closely as possible and optimising the route and the en-route altitude according to winds and temperatures at that moment.
Wishing everyone short long-haul flights,
HEL: N 60° 19.0′ E 024° 57.8′
NRT: N 35° 46.0′ E 140° 23.3′ (Tokyo)
NYC: N 40° 38.4′ W 073° 46.7′ (New York)
SIN: N 01° 21.6′ E 103° 59.4′ (Singapore)