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The passenger emergency oxygen system of DAe Systems: your best choice

The Problem

The Solution

Description of the Chemical Oxygen System

Operation of the System

Advantages of Chemical Oxygen

Advantages of the DAe Systems solution

Certification and Approvals

The Problem

In accordance with the standards and recommended practices of the ICAO (International Civil Aviation Organization), laid down in Appendix 6 to the Convention on International Civil Aviation, Part 1, sections 4.3.8, 6.7.5 and 6.7.6, all aeroplanes intended to be operated at flight altitudes at which the atmospheric pressure is less than 376 hPa, or which, if operated at flight altitudes at which the atmospheric pressure is more than 376 hPa, cannot descend safely within four minutes to a flight altitude at which the atmospheric pressure is equal to 620 hPa, shall be provided with automatically deployable oxygen equipment for passengers and crew members.

The above requirement has been made mandatory by most national civil aviation authorities worldwide and in many cases applies to aeroplanes for which the individual certificate of airworthiness has been first issued before November 9, 1998 as well.

Several years ago the vast majority of the older Russian-/Soviet-built airliners such as the Tupolev Tu–154B, Tu–134, Ilyushin Il–62M, a certain portion of the Tupolev Tu–154M and Antonov An–72/74 aircraft fleets as well as many Ilyushin Il–86s and Yakovlev Yak–42s did not yet have a passenger emergency oxygen system on board.

The Solution

Following the joint efforts of DAe Systems and BASA, its representative in Central and Eastern Europe, Russia and the CIS at that time, in 1997 a Tupolev Tu–154M airliner belonging to Balkan Bulgarian Airlines, LZ-BTQ, was retrofitted with a passenger emergency oxygen system with chemical oxygen generators and a kit of Oxycrew Protective Breathing Equipment (PBE) of DAe Systems. The retrofit was performed in accordance with the technical documentation of the General Designer of the aircraft at Tupolev PSC and was certified by the Bulgarian Civil Aviation Administration.

The passenger emergency chemical oxygen system of DAe Systems has since been installed on 85 aircraft, including most Tu–154Ms in service as well as Tu–154B, Tu–134, Tu–204–300, Il–62M, An–72/74, An–74TK–300 and An–26B–100 aircraft belonging to Russian, CIS, East European and South American airlines.

The modification of Tu–154 airliners is performed at the Vnukovo Aircraft Overhaul Plant (VARZ–400) in Moscow, Russia.

On your request, we will be pleased to assist you with technical information so that you can develop your own documentation and perform an oxygen system retrofit at your maintenance base. We will also help you with engineering solutions for unusual cabin configurations (VIP etc.) and new aircraft types.

The passenger emergency oxygen solution of DAe Systems is extremely flexible — a proof of this is the above range of modified aircraft types and the retrofit of an airliner such as the Ilyushin Il–18 that has taken place in the past.

Description of the Chemical Oxygen System

The passenger emergency oxygen system with chemical oxygen generators consists of lightweight containers that have been initially designed for the Airbus narrowbody aircraft family. For installation on Russian/CIS aircraft, DAe Systems currently delivers containers that are optimized for the Eastern market.

Each container holds a chemical oxygen generator and breathing masks for passengers connected with supply tubes and lanyards to the generator. The container lid is fixed in closed position by an electrical latch, which will open in case of a cabin decompression.

On Russian/CIS-built aircraft, two main chemical oxygen container types are normally installed:

The Type I container is intended for installation into hatracks in passenger aircraft cabins. It is a light, robust box manufactured from a single sheet of aluminium using a high-technology deep drawing process. There are configurations of this container type with 2, 3 and 4 oxygen masks.

The Type II container with 2 oxygen masks is compact and is intended for installation in aircraft lavatories and entrance areas. Its distinctive feature is the possibility to install it at any spatial angle.

The color of the lids of the oxygen containers is chosen by the customer to comply with the aircraft cabin interior.

Operation of the System

Upon emergency (decompression in the aircraft cabin during flight), an altitude switch located in the front section of the aircraft automatically produces a signal, which powers the electrical network of the passenger emergency chemical oxygen system, activating the container latches and thus causing the lids to open so that the passenger oxygen masks fall out of the containers.

The flight crew also has the possibility to activate the passenger emergency oxygen system manually from the cockpit. On the Tu–154, the power supply network of the oxygen system containers has been designed to be redundant and to provide information on the operating/serviceability status of the electrical network.

After activation of the system, the passengers in each seat block would pull one or more of the oxygen masks, thus starting the chemical oxygen generator. Then, oxygen would flow for the passengers to breathe for a certain period of time, which is sufficient for the aircraft to descend to a lower, oxygen-richer altitude.

The oxygen generator flow profile is designed to correspond to a typical aircraft emergency descent profile.

The chemical oxygen generators of DAe Systems normally used on Russian/CIS airliners have an oxygen flow duration of 15 minutes. Apart from that, a 22-minute chemical oxygen system is available — it has already been installed on board An–74TK–300 and An–26B–100 aircraft.

Advantages of Chemical Oxygen

Emergency oxygen systems for passengers and cabin attendants that are based on chemical generators offer significant advantages in comparison with same-class gaseous oxygen systems.

Oxygen generator-based systems are:

• substantially lighter than gaseous systems (no bottles, tubing and other heavy high-pressure equipment);
• cheaper than gaseous systems; much cheaper and easier to install into an aircraft due to the fewer components (often only wiring and switches are needed in addition to the chemical oxygen containers);
• due to the same reasons, chemical systems are more flexible and allow easy reconfiguration in case of changes in the seating arrangement of the aircraft cabin;
• chemical systems are substantially safer due to the lack of high-pressure oxygen. Moreover, oxygen is produced from chemicals in the generator only when it's needed. Therefore, there is no storage of oxygen, which completely eliminates any resulting fire hazard;

• chemical oxygen systems are reliable. In case of malfunction, an entire gaseous oxygen system or large sections of it may fail. This is impossible to happen with а chemical system thanks to its modularity, where each container is autonomous and can be also manually opened by the cabin crew upon necessity.

  In addition, unlike gaseous oxygen systems, chemical system containers will also operate in case of a total power supply failure on board the aircraft;

• chemical oxygen systems are virtually maintenance-free (one routine check in five years, done on board without any disassembly), whereas gaseous oxygen systems are subject to frequent, massive overhaul procedures including removal of most components from the aircraft for testing in lab conditions. On the contrary, a chemical oxygen system is truly an “install-and-forget” solution;
• chemical oxygen systems are always ready for use. There is no constant monitoring of the oxygen pressure in the system, no leakage, no dangerous and expensive refilling at airports, no flight delays due to the insufficient amount of oxygen in the system.

Therefore, chemical emergency oxygen systems are extremely attractive not only to airlines, but to aircraft manufacturers as well, allowing substantial savings in costs, material, working hours and improving the dispatch reliability and overall safety of the fleets.

Advantages of the DAe Systems solution

The passenger emergency chemical oxygen solution of DAe Systems is superior to similar equipment in many aspects. The most significant of these are:

• the chemical reactions which take place in the chemical oxygen generator after its activation are as follows:

  • 2 NaClO₃ → 2 NaCl + 3 O₂
    Fundamental reaction
  • 2 Na₂O + O₂ → 2 Na₂O₂ + Q (heat)
    Heat generating reaction
  • Na₂O₂ + Cl₂ → 2 NaCl + O₂
    Chlorine absorption reaction

  The final products of the whole chemical process are just oxygen (O₂) and salt (NaCl).

  Some chemical generators of other manufacturers may contain heavy metals and other toxic and carcinogenic substances, which can lead to usage limitations due to incompliance with environmental regulations and will require substantial expenses for the disposal of used and expired generators following a special procedure;

• the surface of DAe Systems chemical oxygen generators is made of polished stainless steel, which provides better heat exchange characteristics during operation. Therefore, the aircraft hatrack receives less heat in comparison with the systems of other manufacturers;
• the oxygen generators and containers are lighter than similar systems (up to 7% lower system weight);
• the produced oxygen has very high purity and is comparable to medical oxygen;
• the time between system checks is adequately long (once in 5 years);
• the useful life of the chemical oxygen generators amounts to 15 years. After expiration of the useful life it is necessary to replace only the generator, since the remaining components of the chemical oxygen container are operated on technical condition;
• the built-in door stop assembly offers the opportunity to visually check the contents of the oxygen container as well as the serviceability of the door latch.

And last, but not least: the passenger emergency oxygen system of DAe Systems is engineered and manufactured in Germany with very high quality — in correspondence with the best German traditions. This advantage is supplemented by the rich experience of the company based on the more than 100,000 oxygen containers produced since 1991.

Certification and Approvals

The passenger emergency chemical oxygen system of DAe Systems has all necessary approvals and certificates.

In particular, it is approved by the Moscow-based Interstate Aviation Committee (IAC) Aviation Register with issuance of Appliance Design Approvals (see left). This allows the installation of the system on any airliner produced and operated in Russia and the CIS member states.

The manufacturing of the system has also been approved by the IAC Aviation Register.

All Tu–154 aircraft equipped with the system have been retrofitted in accordance with the respective documentation of the General Designer at Tupolev PSC.