6 aircraft systems that help pilots keep you safe in an emergency
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For most passengers, a good flight is one where you barely notice it: straightforward airport experience, friendly cabin crew, an on-time departure and smooth flying conditions. On rare occasions, however, what pilots call “non-normal” situations do occur.
For those of us on the other side of the flight deck door, your safety is the reason why we’re there. We keep our skills sharp through regular recurrent testing and training to ensure that, should we experience a non-normal situation, we know exactly how to deal with it.
Commercial aircraft are designed with these events in mind. Should they occur, there are systems in place to assist us in keeping the passengers safe and getting the aircraft back on the ground. Here are six of the most important systems on board the 787 Dreamliner.
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An engine fire, although seemingly catastrophic, poses little threat to the aircraft if it’s handled correctly. To protect the aircraft in this event, there are two elements to the engine fire protection system on the 787 Dreamliner: detection and extinguishing.
In each engine, there are multiple dual-channel detector assemblies. Each channel provides both fire and overheat detection. In normal cases, at least one element in each channel must detect a fire or an overheat for the fire warning to go off in the flight deck.
That sounds pretty complicated, so let’s break it down.
The whole point of having two fire detection systems is to guard against false positives — situations where a single system may have a fault and then indicate a fire. This is obviously the safe option in the case of a system failure, but if every time a detection channel failed, the pilots would have no option but to shut the engine down and divert the aircraft.
The presence of the second system guards against these false warnings. It’s like trying to heat a pan of water to an exact temperature. With one thermometer in the pan, when the reading hits the desired temperature, the water could be at that temperature. Or, the thermometer could be broken or inaccurate. With a second thermometer in the pan, if both show the desired temperature at the same time, you can be pretty sure the reading is accurate.
That said, if the aircraft detects that one of the channels has broken, the system reverts to single-channel operation. So, should the remaining system detect a fire or overheat situation, it triggers the appropriate warning in the flight deck.
If both systems were to fail, then no fire detection is available and the aircraft would not be allowed to depart.
When the system detects the presence of a fire in the engine, a number of indications appear in the flight deck. Firstly, the fire bell sounds along with the illumination of the red Master Warning light. On the Engine Indication and Crew Alert System (EICAS) screen, the FIRE ENG L or R is displayed. The relevant fuel control switch illuminates red, as does the relevant engine fire switch.
With the activation of the engine fire system, for this example, in the left engine, the pilots have a well-practised routine to execute.
The pilot responsible for flying the aircraft (Pilot Flying, or PF) will continue to do just that. It is imperative that one pilot continues to monitor the flight path of the aircraft and does not get drawn into dealing with the problem. They will then instruct the Pilot Monitoring (PM) to carry out the “Fire Engine Left” memory items.
As the prompt execution of these items is essential, they are done from memory and not from a checklist. This involves turning off the autothrottle, closing the thrust lever, shutting off the Fuel Control Switch and pulling and turning the fire handle to discharge the fire extinguisher bottle into the engine.
There are two fire extinguisher bottles on the aircraft and these can be used in either engine. Rotating the engine fire switch to the left discharges the first bottle into that engine. If the same switch is then rotated to the right, the second bottle is used in the same engine.
Cabin pressurisation failures
The outside atmosphere at 39,000 feet is pretty inhospitable. Temperatures are a chilly negative 60 degrees Celsius and the air is so thin that breathing unassisted is impossible. It’s for these reasons that airliners have a pressurisation system to ensure you’re kept comfortable in the cabin.
The system is so advanced on aircraft such as the 787 Dreamliner, you can experience the same air composition as being on the ground in Denver, Colorado.
“Should the cabin pressurisation system fail, oxygen will be provided. Pull a mask towards you and breathe normally.”
How many times have you heard this during the safety briefing but never really understood what it meant?
Depending on the aircraft type, supplemental oxygen can be provided in different ways. On the 787 Dreamliner, there are two independent oxygen systems: one for the flight deck and one for the passenger cabin.
At 43,000 feet flying altitude, the altitude in the cabin is around 7,100 feet. Should the cabin altitude reach 15,000 feet due to a loss of pressurisation, the masks in the cabin, galleys and toilets will drop automatically. Oxygen cylinders in the cargo compartments contain enough oxygen for around one hour of use for all passengers on board.
When flying at 43,000 feet, you have around 12 seconds to put your mask on before you will be incapable of doing it yourself. That’s why you must fit your own mask before helping others.
Lavatory fire detection
Some people still think it’s a good idea to smoke in the toilets. It’s really not. By doing so, you’re putting the safety of the aircraft at risk and for that reason, it’s illegal and you could get arrested and prosecuted on landing.
All aircraft have some form of lavatory fire detection and protection. On the 787, this consists of a smoke detector and an automatic extinguisher. If smoke is detected, an aural alert sounds both in the lavatory as well as in the cabin. In addition to this, lights will illuminate in the cabin to alert the cabin crew, and the Master Warning bell and light goes off in the flight deck. If there is smoke in the toilet, the crew will know.
If heat is detected in the waste bin, a fire extinguisher is automatically discharged into the bin. The cabin crew will then tend to the smoke alarm in accordance with their training.
To assist with fires in the cabin, there are a number of fire extinguishers and protective breathing equipment available to the crew. These are strategically located around the aircraft so the nearest one is never more than a few rows away. The extinguishers are designed to remove the oxygen from the area around the fire.
For 99.9% of the time, Air Traffic Control (ATC) does an excellent job of keeping aircraft safely separated by at least 1,000 vertical feet. However, should there be a mistake and risk of collision exists, all commercial airliners have a backup system that’s designed to save the day.
Traffic Collision Avoidance System, or TCAS, uses the aircraft’s transponder to broadcast its position to other aircraft. The receiving aircraft take this information and display it on the navigation display to the pilots.
The TCAS system generates an invisible “safe zone” around the aircraft based on time to a potential collision. This zone isn’t fixed but varies depending on how quickly targets are moving towards the aircraft.
The system constantly makes calculations on the trajectory of all the aircraft it’s tracking, ensuring that none of them conflicts with the “safe zone,” and if it looks like a particular aircraft is heading towards a position where they could become a threat, the system escalates the warnings to the pilots.
If the TCAS system determines that the separation from the threat may not be sufficient, it increases the warning level to the highest alert — a resolution advisory, or “RA.”
This consists of the traffic display changing to a solid red square, an aural alert and a command to change the pitch of the aircraft. A resolution advisory will be issued 35 to 15 seconds from a potential collision.
The key to a successful RA is that the TCAS systems on both aircraft communicate with each other and coordinate their commands. If one aircraft instructs its pilots to climb, the other will instruct its pilots to descend. Once an RA has been issued, it’s imperative the pilots obey the TCAS instruction and ignore any climb or descent commands given by ATC.
Resolution advisories are very rare. Most pilots will go a whole career and maybe have only a few. In the 15 years I’ve been flying, I’ve had just a single RA.
The cargo holds, too, have a sophisticated system of fire protection. Depending on the variant of the 787, there are a number of smoke detectors in the cargo compartments. The 787-9 has more than the 787-8, and the 787-10 has more than the 787-9. It’s directly proportional to the size of the aircraft.
As with the engine fire detection, two cargo compartment smoke detectors must be activated for the flight deck alarm to be set off.
In the flight deck, the indications of smoke in the cargo compartment are very similar to that of an engine fire. The Master Warning light and bell are activated and the EICAS message is illuminated.
Depending on the ETOPS certification of the aircraft there are a number of fire extinguisher bottles available.
Most 787s are certified for ETOPS 180 (180 minutes flying time from the nearest diversion airport) and will have five extinguisher bottles fitted to cover this time period. With higher ETOPS-rated aircraft, such as ETOPS 330 as some 787s are rated, more extinguisher bottles are required to cover this longer time span.
If a CARGO FIRE warning is activated in flight, the system automatically discharges two extinguisher bottles into the relevant compartment. After 15 minutes, the remaining bottles are discharged, but at a slower rate.
The pilots can also activate this system by pressing the CARGO FIRE DISCHARGE switch in the flight deck.
Getting seriously ill whilst in a sealed tube 7 miles above the ground is less than ideal. Should the worst happen, however, we have an ace up our sleeves.
Banner University Medical Centre in Tuscon, Arizona, is not your average hospital.
At the centre of the emergency room sits the Medlink operations hub. From this high-tech centre, specialist doctors are able to take sick passenger information passed by airline crew and suggest treatment depending on the facilities available on board the aircraft.
Pilots can make a call directly to Medlink’s control room in Arizona using satellite communications (SatCom). Here, one of the Medlink staff answers the call and speaks to the pilot.
After taking a few details of the flight, the operative is able to see on a screen where exactly in the world the aircraft is. They are also able to see what medical equipment is on board the aircraft. When the patient details have been relayed to Medlink, a doctor is then called from the emergency room whose speciality best suits the situation.
Once the doctor is on the phone and talking to the pilot, quite often the best way to get the most accurate and up-to-date information is to speak directly to the crew dealing with the situation. But how do you connect a doctor in the U.S., via a satellite, to the flight deck of an airliner and to a seat 40 rows back?
On modern aircraft, such as the Boeing 787 Dreamliner, the pilot is able to transfer the call from the flight deck directly to the nearest cabin phone. This not only enables the cabin crew to talk directly to the doctor but also negates the need to constantly open the flight deck door — an important aspect of today’s security-conscious aviation world.
The doctor is then able to get real-time information from the cabin crew and suggest a course of treatment. In addition to a basic first aid kit, most aircraft will have a more advanced medical kit. If there’s a medical professional on board, Medlink may also suggest that they assist.
Based on the information provided to Medlink about the patient, they can then recommend that we either continue with the flight to the destination or, if the situation is serious, divert to a nearby airfield so the passenger can get proper medical assistance.
Whilst punctuality and service are important, your pilots and crew are primarily concerned with your safety. With that in mind, we have a variety of systems available to us should any highly unlikely emergency occur.
Whether it’s a loss of cabin pressurisation or a fire in the cargo hold, you can relax on your flight knowing you’re in safe hands.
Featured image by Charlie Page/TPG.
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