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TITANIC of the Skies! - The Untold Story of Air France 447
Air France Flight 447 was supposed to go from Rio to Paris. Flight was scheduled to last 12 hours and 45 minutes and because of that, the flight crew had been augmented with an extra pilot 3 pilots were going to fly. The captain was 58 years old and had a total experience of almost 11 000 flying hours, including over 1 700 hours for the A330. The first officer was 32 years old, with almost 3 000 hours of flight experience including over 800 hours on the A330. He has done his type rating on the Airbus 330 and 340 in 200, the year before the flight. The third pilot, the relief pilot, was a 37 year sold officer with a total time of 6 500 hours including over 4 400 hours on the A330 so he was the most experience on this type. He had flown very little during the previous 3 months because he was also working as a management pilot in Air France. Prior to operate the flight, pilots met up and reviewed planning documentation i ncluding weather, flight plan and NOTAMs. In Paris the weather route looked more complicated. Since flight crossed the equator it would also crossing an area known over the Atlantic as tne Intertropical convergence zone, or the ITCZ In this zone, easterly winds from the northern and southern emisphere willl converge and can force the humid air from the surface of the sea upwards. This can cause thunderstorms which can reach 60 000 feet, way higher than most aircrafts can fly. So aircraft might be subject to fly between or through parts of these storm clouds. These storms can also sometimes contain smaller water content, making them harder to see on the aircraft's weather radar. So pilots need to be careful while navigating around them. Pilots previously discussed this and carried a bit of extra fuel to give them the option to navigate around the storms when needed. The 9 cabin crew was also briefed about possible turbulence.
Most people are familiar with heavy rain and sometimes hail cooming from these storms. But if you look higher, things become more complicated. Because of the very strong currents inside of the cloud, water droplets can be forced upwards into very cold air and become super cooled. But as soon as they hit surface of some sort, the will instantly freeze and create clear ice. Sometimes these super cooled droplets can collide with snowflakes and when that happens, a type of soft ice crystals can be formed, which is not as hard as hail but big enough to be heard when it hits the aircraft if you fly through it. This type of precipitation doesn't create the type of heavy airframe icing that super cooled rain does but it had significant volume and can quickly clog up and overwhelm censors and probes on the aircraft, especially the pilots probes. More than 9 different occurrences of this type of clogging happening to Air France flights have been reported during 2008 and 2009. These reports, together with how to recognize and deal with these issues, had been published in safety bulletins, curculating to all Air France pilots the year before the incident flight. The aircraft here was a new Airbus A330 - 203. It had been delivered to Air France in 2005 and was almost perfect in working order on the evening of the departure.Pilots ordered 70,4 tons of fuel to be loaded prior to the flight. Pilots need a way to accuratly measure tha amount of air flowing over the wings because that's what determines the performance of the aircraft. To do this, they utilize a type of probe known as pilot tube or pilot probe. These probes are often situated along the front of the aircraft below the cockpit and they look a little bit like gun barrels. They have a hole in the front where the air enters and the total pressure is then measured inside of the tube. They are electrically heated and the heating is automatic on the Airbus A330.
But in order to accurately measure the air speed, the static pressure must also be measured so it can be deducted from the total pressure from the pilot probes. The static pressure is measured from a different device called a static port and taht static pressure is then used both for calculating the airspeed and crucially, also the altitude of the aircraft. These different pressures are then sent to the aircraft's computers, called Air Data Modules, or ADMs. The ADMs will calculate the correct true air speed but another thing important in the story is that the static pressure from the static port must be corrected depending on how fast the aircraft is flying. That's because the air flows over the aircraft surfaces surrounding the static port and will therefore create localized pressure difference depending on speed. These corrections are done automatically by the ADM computers and because air speed and altitude are critical values, these are 3 different independant sets of probes and computers fitted to the aircraft. Now because of the problems that Air France and other operators had reported of ice crystals clogging up the pilot's probes, Airbus had started to look into the problem. A newer type of pilot probe had been found to be more effective in preventing and a maintainance bulletin had been issued upgrading their first Airbus 1330 about 1 month prior the final departure of Flight 447. The aircraft was scheduled to have its probed changed to its arrival to Paris after the flight. But why wasn't these changes mandatory instead of just suggestion? Because the temporary loss of air speed due to this issue was both very rare, only lasting for a couple of minutes and there was a defined procedure which the pilots were supposed to follow in case this happened. for Air France the procedure was known as IAS douteuse but it can sometimes be referred to unreliable speed. Because problem was reported several times, it had been included in the recurrent training scenario.
And it was for all Air France crews during 2008 and 2009. Training included air speed unreliable exercices but only at low altitude. That's because when seen as more safety critical because of the closeness of the terrain but the performance of the aircraft was also better than it would be at high altitude to diagnose because the failure will look different depending on what caused it and how severe it is. During the exercices that Air France crew practised, the autopilot didn't disconnected and there were no warnings sounding in the cockpit when the failure occurred. Now the air speed unreliable procedure included the use of memory items meaning safety critical items that needed to be done straight away from memory of the pilots. But using them was optional depending on the situation and that had been interpreted as only needed if the aircraft was close to the ground. Also none of the pilots in Flight 447 received a recent training on how to deal with an approach to stall and recovery, especially at high altitude. The latest stall training they received was was done during their type rating on the Airbus A320 which they done years ealier. That initial training was done at low altitude in which heavy emphasis was put on the use of thrust to recover the aircrcaft and power it out of the stall, achieving it with minimum altitude loss. Decreasing the pitch was a secondary action to take. This idea that the engines will have enough power to pull the aircraft out of an extreme angle of attack is an important point for later.
216 boarded and the plane took off barely 10 minutes behind the schedule only. After climbing to 20 000 feet, the relief pilot left the cockpit to start his scheduled rest period for 3 hours. Crew compartment consisted of 2 bunk beds behind the cockpit. Pilots got clearance to go at level 350, so 35 000 feet of altitude. After Brasilia, they switched to Recife control and they were going to be the last ones to have radar contact with during the flight. Above the Atlantic they would soon be out of radar coverate, and followed by oceanic traffic separation procedures. Flights over oceanic areas require special training procedures and aircraft equipment. Since the curvature of the Earth makes VHF radio communication impossible aircraft are equipped with with something called HF radios. These radios use layers in the ionosphere to bounce the signals off from and can therefore reach much further distances. As the aircraft passed an RNAV point called INTOL pilots checked in with Atlantico control,, one of the 2 HF frequencies that they had been given. The pilots then tried to log into a new system that was being tested at the time in the area called ADS C. This system would use automatic reports sent by the aircraft itself via satellite to update the position of the aircraft to ATC thus showing where it was, een if they didn'thave radar coverage. This system also would send immediatly a report if an aircraft deviated from the course or altitude that it had assigned. Unfortunatly due to a formatting error in the flight plan that had been filed the pilots were unable to log in into the new system so this flight wouldn't be tracked anymore after leaving the radar coverage. Airbus A330 is a fly by wire aircraft meaning that the inputs that the pilots makes on their site stick and rudders willl be electronically interpreted by a computer and then sent to the hydraulic flight control flight actuators for execution.
TITANIC of the Skies! - The Untold Story of Air France 447
Air France Flight 447 was supposed to go from Rio to Paris. Flight was scheduled to last 12 hours and 45 minutes and because of that, the flight crew had been augmented with an extra pilot 3 pilots were going to fly. The captain was 58 years old and had a total experience of almost 11 000 flying hours, including over 1 700 hours for the A330. The first officer was 32 years old, with almost 3 000 hours of flight experience including over 800 hours on the A330. He has done his type rating on the Airbus 330 and 340 in 200, the year before the flight. The third pilot, the relief pilot, was a 37 year sold officer with a total time of 6 500 hours including over 4 400 hours on the A330 so he was the most experience on this type. He had flown very little during the previous 3 months because he was also working as a management pilot in Air France. Prior to operate the flight, pilots met up and reviewed planning documentation i ncluding weather, flight plan and NOTAMs. In Paris the weather route looked more complicated. Since flight crossed the equator it would also crossing an area known over the Atlantic as tne Intertropical convergence zone, or the ITCZ In this zone, easterly winds from the northern and southern emisphere willl converge and can force the humid air from the surface of the sea upwards. This can cause thunderstorms which can reach 60 000 feet, way higher than most aircrafts can fly. So aircraft might be subject to fly between or through parts of these storm clouds. These storms can also sometimes contain smaller water content, making them harder to see on the aircraft's weather radar. So pilots need to be careful while navigating around them. Pilots previously discussed this and carried a bit of extra fuel to give them the option to navigate around the storms when needed. The 9 cabin crew was also briefed about possible turbulence.
Most people are familiar with heavy rain and sometimes hail cooming from these storms. But if you look higher, things become more complicated. Because of the very strong currents inside of the cloud, water droplets can be forced upwards into very cold air and become super cooled. But as soon as they hit surface of some sort, the will instantly freeze and create clear ice. Sometimes these super cooled droplets can collide with snowflakes and when that happens, a type of soft ice crystals can be formed, which is not as hard as hail but big enough to be heard when it hits the aircraft if you fly through it. This type of precipitation doesn't create the type of heavy airframe icing that super cooled rain does but it had significant volume and can quickly clog up and overwhelm censors and probes on the aircraft, especially the pilots probes. More than 9 different occurrences of this type of clogging happening to Air France flights have been reported during 2008 and 2009. These reports, together with how to recognize and deal with these issues, had been published in safety bulletins, curculating to all Air France pilots the year before the incident flight. The aircraft here was a new Airbus A330 - 203. It had been delivered to Air France in 2005 and was almost perfect in working order on the evening of the departure.Pilots ordered 70,4 tons of fuel to be loaded prior to the flight. Pilots need a way to accuratly measure tha amount of air flowing over the wings because that's what determines the performance of the aircraft. To do this, they utilize a type of probe known as pilot tube or pilot probe. These probes are often situated along the front of the aircraft below the cockpit and they look a little bit like gun barrels. They have a hole in the front where the air enters and the total pressure is then measured inside of the tube. They are electrically heated and the heating is automatic on the Airbus A330.
But in order to accurately measure the air speed, the static pressure must also be measured so it can be deducted from the total pressure from the pilot probes. The static pressure is measured from a different device called a static port and taht static pressure is then used both for calculating the airspeed and crucially, also the altitude of the aircraft. These different pressures are then sent to the aircraft's computers, called Air Data Modules, or ADMs. The ADMs will calculate the correct true air speed but another thing important in the story is that the static pressure from the static port must be corrected depending on how fast the aircraft is flying. That's because the air flows over the aircraft surfaces surrounding the static port and will therefore create localized pressure difference depending on speed. These corrections are done automatically by the ADM computers and because air speed and altitude are critical values, these are 3 different independant sets of probes and computers fitted to the aircraft. Now because of the problems that Air France and other operators had reported of ice crystals clogging up the pilot's probes, Airbus had started to look into the problem. A newer type of pilot probe had been found to be more effective in preventing and a maintainance bulletin had been issued upgrading their first Airbus 1330 about 1 month prior the final departure of Flight 447. The aircraft was scheduled to have its probed changed to its arrival to Paris after the flight. But why wasn't these changes mandatory instead of just suggestion? Because the temporary loss of air speed due to this issue was both very rare, only lasting for a couple of minutes and there was a defined procedure which the pilots were supposed to follow in case this happened. for Air France the procedure was known as IAS douteuse but it can sometimes be referred to unreliable speed. Because problem was reported several times, it had been included in the recurrent training scenario.
And it was for all Air France crews during 2008 and 2009. Training included air speed unreliable exercices but only at low altitude. That's because when seen as more safety critical because of the closeness of the terrain but the performance of the aircraft was also better than it would be at high altitude to diagnose because the failure will look different depending on what caused it and how severe it is. During the exercices that Air France crew practised, the autopilot didn't disconnected and there were no warnings sounding in the cockpit when the failure occurred. Now the air speed unreliable procedure included the use of memory items meaning safety critical items that needed to be done straight away from memory of the pilots. But using them was optional depending on the situation and that had been interpreted as only needed if the aircraft was close to the ground. Also none of the pilots in Flight 447 received a recent training on how to deal with an approach to stall and recovery, especially at high altitude. The latest stall training they received was was done during their type rating on the Airbus A320 which they done years ealier. That initial training was done at low altitude in which heavy emphasis was put on the use of thrust to recover the aircrcaft and power it out of the stall, achieving it with minimum altitude loss. Decreasing the pitch was a secondary action to take. This idea that the engines will have enough power to pull the aircraft out of an extreme angle of attack is an important point for later.
216 boarded and the plane took off barely 10 minutes behind the schedule only. After climbing to 20 000 feet, the relief pilot left the cockpit to start his scheduled rest period for 3 hours. Crew compartment consisted of 2 bunk beds behind the cockpit. Pilots got clearance to go at level 350, so 35 000 feet of altitude. After Brasilia, they switched to Recife control and they were going to be the last ones to have radar contact with during the flight. Above the Atlantic they would soon be out of radar coverate, and followed by oceanic traffic separation procedures. Flights over oceanic areas require special training procedures and aircraft equipment. Since the curvature of the Earth makes VHF radio communication impossible aircraft are equipped with with something called HF radios. These radios use layers in the ionosphere to bounce the signals off from and can therefore reach much further distances. As the aircraft passed an RNAV point called INTOL pilots checked in with Atlantico control,, one of the 2 HF frequencies that they had been given. The pilots then tried to log into a new system that was being tested at the time in the area called ADS C. This system would use automatic reports sent by the aircraft itself via satellite to update the position of the aircraft to ATC thus showing where it was, een if they didn'thave radar coverage. This system also would send immediatly a report if an aircraft deviated from the course or altitude that it had assigned. Unfortunatly due to a formatting error in the flight plan that had been filed the pilots were unable to log in into the new system so this flight wouldn't be tracked anymore after leaving the radar coverage. Airbus A330 is a fly by wire aircraft meaning that the inputs that the pilots makes on their site stick and rudders willl be electronically interpreted by a computer and then sent to the hydraulic flight control flight actuators for execution.
Post.
This type of control has benefits like making the aircraft lighter and it allows the aircraft to monitor certain safety parameters. and make sure that those parameters aren't excedeed. Parameters like excessive bank and pitch angles are monitored as well as safeguarding the maximum and minimum speeds and a whole load of others parameters as well. Only maneuvers really extreme and ultimatly dangerous are blocked by the system. Those operating these systems need to understand how they work and when those protections work and don't. It's true for all aircrafts but even more here. For these protections to properly work, the computers who monitor them needs to be absolutly sure that they are using correct parameters to start with. If that's not the case, computers will back off and take away those protections because the computers aren't sure what is going on. Thse computers receive their inputs from a lot of different sources like the pilot probes, the static probes, the inertial reference unit, angle of attack vanes and so on. They combine all of this data into 3 Air Data Reference Units They combined to form Air Data Inertial Reference System ( ADIRS ). As long as these 3 or at elast 2 of the 3 ADIRS agree with each other aircraft control computers are happy and it can operate on what is called normal law. Normal Laws means that all protection are available and that the aircraft is basically impossible to stall or to put in an upset situation. But of 2 of these or more start sending strange information, first of all these inconsistencies might affect the autoflight system like autopilot or autothrottle and the flight directors who show the pilots how to fly. Aircraft will not try to navigate or control the aircraft if unsure on what is going on. Its up to the pilots to figure o it out. Following on same logic, the aircraft computers will degrade from normal law to either alternate law 1 or alternate law 3 depending on the severty of the issues.
Difference between normal law and alternate law 2 is that all protections that the aircraft normally have regarding maximum angle of attack or stall protection will no longer be available. Thsi will be shown by the removal of warning indicators like the barber's pole on the primary flight display as well as yellow crosses where the limitations would normally be shown. Other difference is that the roll control of the aircraft changes. In normal law and alternate law 1, the roll would input on the side stick will command a specific roll rate from the aircraft. If pilot inputs a specific roll rate to be kept, aircraft will give that and gust disturbances will be compensated for. It will be stable and easy to handle. But in alternate law 2 the side stick give direct commands to the ailerons and spoilers rather than commending a specific roll rate. This means no bank protection or stability control. It will also make the aircraft more roll sensitive especially at higher altitude where there is less aerodynamic damping due to the thinner air. Another major difference between conventional aircraft and Airbus fly by wire aircraft is the pitch trim system. If you fly manually in conventional aircraft, the yoke controls the flight controls directly and the trim has to be done deliberatly by the pilots. In the Airbus, the side stick input will ask the control computers for a specific roll rate horizontally and a pitch or a g loading vertically. When the pilots sets a specific pitch, the elevators will initiate the pitch and the massive horizontal stabilizer will then move automatically to continue maintaining that pitch without any pilot input.This also means that there is no big tactile feedback from the stick if the aircraft enters into a strange trim position due to low speed for example. In normal law that's not an issue because the aircraft also guards the aircraft from getting close to an angle of attack high enough to stall but but it's not the case in alternate law.
Cover-Up!? The 2 Nightmare stories of Egyptair Flight 804
This type of control has benefits like making the aircraft lighter and it allows the aircraft to monitor certain safety parameters. and make sure that those parameters aren't excedeed. Parameters like excessive bank and pitch angles are monitored as well as safeguarding the maximum and minimum speeds and a whole load of others parameters as well. Only maneuvers really extreme and ultimatly dangerous are blocked by the system. Those operating these systems need to understand how they work and when those protections work and don't. It's true for all aircrafts but even more here. For these protections to properly work, the computers who monitor them needs to be absolutly sure that they are using correct parameters to start with. If that's not the case, computers will back off and take away those protections because the computers aren't sure what is going on. Thse computers receive their inputs from a lot of different sources like the pilot probes, the static probes, the inertial reference unit, angle of attack vanes and so on. They combine all of this data into 3 Air Data Reference Units They combined to form Air Data Inertial Reference System ( ADIRS ). As long as these 3 or at elast 2 of the 3 ADIRS agree with each other aircraft control computers are happy and it can operate on what is called normal law. Normal Laws means that all protection are available and that the aircraft is basically impossible to stall or to put in an upset situation. But of 2 of these or more start sending strange information, first of all these inconsistencies might affect the autoflight system like autopilot or autothrottle and the flight directors who show the pilots how to fly. Aircraft will not try to navigate or control the aircraft if unsure on what is going on. Its up to the pilots to figure o it out. Following on same logic, the aircraft computers will degrade from normal law to either alternate law 1 or alternate law 3 depending on the severty of the issues.
Difference between normal law and alternate law 2 is that all protections that the aircraft normally have regarding maximum angle of attack or stall protection will no longer be available. Thsi will be shown by the removal of warning indicators like the barber's pole on the primary flight display as well as yellow crosses where the limitations would normally be shown. Other difference is that the roll control of the aircraft changes. In normal law and alternate law 1, the roll would input on the side stick will command a specific roll rate from the aircraft. If pilot inputs a specific roll rate to be kept, aircraft will give that and gust disturbances will be compensated for. It will be stable and easy to handle. But in alternate law 2 the side stick give direct commands to the ailerons and spoilers rather than commending a specific roll rate. This means no bank protection or stability control. It will also make the aircraft more roll sensitive especially at higher altitude where there is less aerodynamic damping due to the thinner air. Another major difference between conventional aircraft and Airbus fly by wire aircraft is the pitch trim system. If you fly manually in conventional aircraft, the yoke controls the flight controls directly and the trim has to be done deliberatly by the pilots. In the Airbus, the side stick input will ask the control computers for a specific roll rate horizontally and a pitch or a g loading vertically. When the pilots sets a specific pitch, the elevators will initiate the pitch and the massive horizontal stabilizer will then move automatically to continue maintaining that pitch without any pilot input.This also means that there is no big tactile feedback from the stick if the aircraft enters into a strange trim position due to low speed for example. In normal law that's not an issue because the aircraft also guards the aircraft from getting close to an angle of attack high enough to stall but but it's not the case in alternate law.
Cover-Up!? The 2 Nightmare stories of Egyptair Flight 804
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DEATHTRAP! The Strange story of Air France flight 736
In December 31st 2020, Air France flight 737 had to go from Brazzaville in Congo, to to Charles de Gaulle airport in Paris. New Year's Eve was approaching. The plane left the Maya Maya Brazzazile airport. Flight was supposed to be quite long with 8 hours so the flight crew was augmented with an extra pilot. Once pre flight planning is completed, before leaving, the pilots decided a final fual of 45,5 tons and then headed over to their cabin crew colleagues to brief them about the flight. Only 136 passengers booked and there were 8 crew members. Among the passengers there were 2 Air France maintenance technicians traveling home for holidays. The captain was a 54 years old pilot with 12 400 horus of total time logged including over 1 000 as captain. He started his career in the military before joining Air France in 2002. He flew on Boeing 737 between 2002 and 2006 at Transavia before being transferred back to mainlad Air France again. He started flying on the A330 as a captain 8 months before the flight. Althought he had 3 800 of experience on that type, only 80 of those have been operated as captain. The 2 first officers had similar experience, similar age, and both of them having military experience. One of them was 53 year sold with 5 600 of flight hours including 550 on this type. The relief pilot was 54 years old with 4 800 flight hours in total including 803 hours on the Airbus A330. He also worked as a synthetic flight instructor or a simulator instructor on that same type for Airbus. But in any case, the senior purser was the most experienced on board, a 57 years old women who amassed 16 400 hours acrcoss several different types including this one. A330 - 203 was waiting for departure. The plane was 18 years old at the time of the flight and had gone through heavy maintenance over China where among other things, the engines had been removed and subsequently refitted again. This engine refitting is particular.
On the plane, 2 tanks on each wing plus a center fuel tank in the belly between the wings, and something known as the trim tank in the horizontal stabilizer. Inside of the inner tanks of each wing, there are so called collector cells from where the fuel is drawn down through the main fuel hoses in the pylon and then into the engines and that means that every time the engine has to be removed, those main fuel hoses also has to be disconnected. The problem though was that the components used to reconnect those boses were known to be fiddly, hard to work with and prone to misalignment. Specifically, a part known as the flange had a tendency to not be seated correctly together with the other connection parts and if this wasn't noticed when the fuel hose was then reconnected well, then the bolts used to make sure that the aprt sealed correctly could be fastened to the correct torque value only to later become a completely loose when this flange would vibrate back into position again. Airbus highlightened the issue in their aicraft maintenance manual back in 2015 already. In fact the original flanges had been replaced by an updated version which was smaller and easier to fit in place. But it wasn't yet mandatory to replace them. The old flanges could be used as long as they were still in stock. Since the aircraft is big and the tanks are located in different parts of the aircraft, there is a bit of tubing required and it's important to see where the fuel is at any given time, especially during takeoff and alnding since several tons of fuel for example in the stablizer in the back will have an impact on the aircraft's center of gravity. Because of that the Airbus A330 is also equipped with something known as a fuel control and monitoring computer or FCMC. This transfers automatically fuel between the different tanks depending on the phase of flight and how much fuel is being used.
For example the FCMC will start an automatic fuel transfer from the inner tanks to the trim tank in the tail whenever the aircraft climbs through flight level 255 and then it will do a similar but reverse transfer during the descent. It will also transfer fuel between the center and the wings on regular intervals, without pilot inputs under normal circumstances If the pilots for whether reason move the engines master switch to off for an engine at any point, this would close the fuel valves providing the fuel to that effective engine, removing fuel completly from it. Back into the plane, the first officer was flying while captain could be monitoring. Then the relief pilot would take the captain's place once the captain rests. Technical log showed no open technical defects All checklists were completed as per standard operating procedures Nothing was noticed during takeoff and climbing and clearance was given to go to flight level 380 or 38 000 feet. Then routine cruise checks were done at flight level 380. It includes filling in the flight plan, updating things like off block and takeoff times and also the first fuel check. This check is done by comparing the expected fuel used with the actual through verifying how much fuel is left in all of the various tanks. When these fuel checks are done whenever passing a certain waypoints but, at a minimum every 30 minutes throughout the flight. Reason to do these tasks is to make sure pilots catch any discrepancies early so they can start dealing with them. It's important to keep track of fuel usage to make sure it can reach destination with the required minimum margins available. It's also important because any significant deviation from the planned fuel use could be an indication of an empending engine issue or fuel leak.
During first check it seemed like 1,4 tons of fuel was missing. It was not good but it didn't bother the captain that much at this point. The top of climb fuel check can be notoriously unreliable since the location of the top of climb often differs due to unexpected level offs, reroutings and weather diversions. But in this cased they received a straight climb without any issue so that shouldn't really be the case. Instead, the captain thought that maybe the fuel quantity was a bit higher if the aircraft was doing one of those fuel transfers because when that happens, quite a big amount of fuel can be hidden inside of the fuel lines as it's being transferred and moved between the tanks. Captain asked his colleagues to monitor the fuel state closely and then went back to the crew bunk to start his scheduled rest period. A 1,4 discrepancy is quite big and even if it was problematic they could return to Brazzaville at any point. An Airbus A330 normally burns between between 4 to 5 tons of fuel per hour so that meant that they were now missing close to 15 minutes of fuel but given his reaction, the captain probably saw similar problems and numbers before. When first officers saw the fuel situation, they saw that for every minute they went by, the difference between how much fuel they should have and what they actually had increased. They also started looking at the weather for their different routes alternatives. After 12 minutes the relief pilot called the captain back in the cockpit. At this point they lost 2,1 tons of fuel, in 1 hour. On top of that fuel imbalance started to form with about 400 kg less in the left tanks compared to the right. There was a possible fuel leak on the left engine. An aircraft like this one will easily handle an imbalance of this size. The imbalance could get as high as 2 900 kilos without any detrimental handling characteristics. Even with 7 500 kilos of difference if one of the inner tanks would be full.
For fuel imbalance some procedures need to be followed, which includes pumping fuel from one side to the other but we wouldn't want to do that if a fuel leak is suspected They started to do the fuel leak non normal checklist from their Quick Reference Handbook or QRB. Some thing that's weird because they already have a ECAM system with electronic checklists to follow if a case like this happens. Thing is that certain problems can be identified quicker by humans than the aircraft systems themselves and the fuel leak is one of those. ECAM had such a procedure but it wouldn't be triggered until the situation had grown considerably worse. But the use of this old checklist would also come with a bit of bias from the crew which would make things more complicated. The first point of the checklist said LAND ASAP meaning that immediate diversion was now required. The captain initially didn't give to this instruction much attention. They waited so long with starting the checklist by leeting the captain sleep back in the crew bunk for 20 minutes. They were now quite close to Yaoundé airport in Cameroon. N'Djamena international airport in Chad was not far away either. Crew was more familiar with the second one. The checklist instructed them to shut down the engine on the side associated with the suspected leak.The reason the checklist started by telling the pilots to divert was because the aircraft could otherwise find itself running out of fuel especially if the leak was identified out over an ocean or a desert. Crucially a fuel leak can also represent a significant fire hazard depending on where the leak is located. An uncontrolled fire is one of the worst emergency. Secondly the list was created to bring the crew through several steps designed to find out where the leak was actually located. If an engine was shut down, using the engine master switch, this would isolate the fuel from that engine.
DEATHTRAP! The Strange story of Air France flight 736
In December 31st 2020, Air France flight 737 had to go from Brazzaville in Congo, to to Charles de Gaulle airport in Paris. New Year's Eve was approaching. The plane left the Maya Maya Brazzazile airport. Flight was supposed to be quite long with 8 hours so the flight crew was augmented with an extra pilot. Once pre flight planning is completed, before leaving, the pilots decided a final fual of 45,5 tons and then headed over to their cabin crew colleagues to brief them about the flight. Only 136 passengers booked and there were 8 crew members. Among the passengers there were 2 Air France maintenance technicians traveling home for holidays. The captain was a 54 years old pilot with 12 400 horus of total time logged including over 1 000 as captain. He started his career in the military before joining Air France in 2002. He flew on Boeing 737 between 2002 and 2006 at Transavia before being transferred back to mainlad Air France again. He started flying on the A330 as a captain 8 months before the flight. Althought he had 3 800 of experience on that type, only 80 of those have been operated as captain. The 2 first officers had similar experience, similar age, and both of them having military experience. One of them was 53 year sold with 5 600 of flight hours including 550 on this type. The relief pilot was 54 years old with 4 800 flight hours in total including 803 hours on the Airbus A330. He also worked as a synthetic flight instructor or a simulator instructor on that same type for Airbus. But in any case, the senior purser was the most experienced on board, a 57 years old women who amassed 16 400 hours acrcoss several different types including this one. A330 - 203 was waiting for departure. The plane was 18 years old at the time of the flight and had gone through heavy maintenance over China where among other things, the engines had been removed and subsequently refitted again. This engine refitting is particular.
On the plane, 2 tanks on each wing plus a center fuel tank in the belly between the wings, and something known as the trim tank in the horizontal stabilizer. Inside of the inner tanks of each wing, there are so called collector cells from where the fuel is drawn down through the main fuel hoses in the pylon and then into the engines and that means that every time the engine has to be removed, those main fuel hoses also has to be disconnected. The problem though was that the components used to reconnect those boses were known to be fiddly, hard to work with and prone to misalignment. Specifically, a part known as the flange had a tendency to not be seated correctly together with the other connection parts and if this wasn't noticed when the fuel hose was then reconnected well, then the bolts used to make sure that the aprt sealed correctly could be fastened to the correct torque value only to later become a completely loose when this flange would vibrate back into position again. Airbus highlightened the issue in their aicraft maintenance manual back in 2015 already. In fact the original flanges had been replaced by an updated version which was smaller and easier to fit in place. But it wasn't yet mandatory to replace them. The old flanges could be used as long as they were still in stock. Since the aircraft is big and the tanks are located in different parts of the aircraft, there is a bit of tubing required and it's important to see where the fuel is at any given time, especially during takeoff and alnding since several tons of fuel for example in the stablizer in the back will have an impact on the aircraft's center of gravity. Because of that the Airbus A330 is also equipped with something known as a fuel control and monitoring computer or FCMC. This transfers automatically fuel between the different tanks depending on the phase of flight and how much fuel is being used.
For example the FCMC will start an automatic fuel transfer from the inner tanks to the trim tank in the tail whenever the aircraft climbs through flight level 255 and then it will do a similar but reverse transfer during the descent. It will also transfer fuel between the center and the wings on regular intervals, without pilot inputs under normal circumstances If the pilots for whether reason move the engines master switch to off for an engine at any point, this would close the fuel valves providing the fuel to that effective engine, removing fuel completly from it. Back into the plane, the first officer was flying while captain could be monitoring. Then the relief pilot would take the captain's place once the captain rests. Technical log showed no open technical defects All checklists were completed as per standard operating procedures Nothing was noticed during takeoff and climbing and clearance was given to go to flight level 380 or 38 000 feet. Then routine cruise checks were done at flight level 380. It includes filling in the flight plan, updating things like off block and takeoff times and also the first fuel check. This check is done by comparing the expected fuel used with the actual through verifying how much fuel is left in all of the various tanks. When these fuel checks are done whenever passing a certain waypoints but, at a minimum every 30 minutes throughout the flight. Reason to do these tasks is to make sure pilots catch any discrepancies early so they can start dealing with them. It's important to keep track of fuel usage to make sure it can reach destination with the required minimum margins available. It's also important because any significant deviation from the planned fuel use could be an indication of an empending engine issue or fuel leak.
During first check it seemed like 1,4 tons of fuel was missing. It was not good but it didn't bother the captain that much at this point. The top of climb fuel check can be notoriously unreliable since the location of the top of climb often differs due to unexpected level offs, reroutings and weather diversions. But in this cased they received a straight climb without any issue so that shouldn't really be the case. Instead, the captain thought that maybe the fuel quantity was a bit higher if the aircraft was doing one of those fuel transfers because when that happens, quite a big amount of fuel can be hidden inside of the fuel lines as it's being transferred and moved between the tanks. Captain asked his colleagues to monitor the fuel state closely and then went back to the crew bunk to start his scheduled rest period. A 1,4 discrepancy is quite big and even if it was problematic they could return to Brazzaville at any point. An Airbus A330 normally burns between between 4 to 5 tons of fuel per hour so that meant that they were now missing close to 15 minutes of fuel but given his reaction, the captain probably saw similar problems and numbers before. When first officers saw the fuel situation, they saw that for every minute they went by, the difference between how much fuel they should have and what they actually had increased. They also started looking at the weather for their different routes alternatives. After 12 minutes the relief pilot called the captain back in the cockpit. At this point they lost 2,1 tons of fuel, in 1 hour. On top of that fuel imbalance started to form with about 400 kg less in the left tanks compared to the right. There was a possible fuel leak on the left engine. An aircraft like this one will easily handle an imbalance of this size. The imbalance could get as high as 2 900 kilos without any detrimental handling characteristics. Even with 7 500 kilos of difference if one of the inner tanks would be full.
For fuel imbalance some procedures need to be followed, which includes pumping fuel from one side to the other but we wouldn't want to do that if a fuel leak is suspected They started to do the fuel leak non normal checklist from their Quick Reference Handbook or QRB. Some thing that's weird because they already have a ECAM system with electronic checklists to follow if a case like this happens. Thing is that certain problems can be identified quicker by humans than the aircraft systems themselves and the fuel leak is one of those. ECAM had such a procedure but it wouldn't be triggered until the situation had grown considerably worse. But the use of this old checklist would also come with a bit of bias from the crew which would make things more complicated. The first point of the checklist said LAND ASAP meaning that immediate diversion was now required. The captain initially didn't give to this instruction much attention. They waited so long with starting the checklist by leeting the captain sleep back in the crew bunk for 20 minutes. They were now quite close to Yaoundé airport in Cameroon. N'Djamena international airport in Chad was not far away either. Crew was more familiar with the second one. The checklist instructed them to shut down the engine on the side associated with the suspected leak.The reason the checklist started by telling the pilots to divert was because the aircraft could otherwise find itself running out of fuel especially if the leak was identified out over an ocean or a desert. Crucially a fuel leak can also represent a significant fire hazard depending on where the leak is located. An uncontrolled fire is one of the worst emergency. Secondly the list was created to bring the crew through several steps designed to find out where the leak was actually located. If an engine was shut down, using the engine master switch, this would isolate the fuel from that engine.