Fokker 100: New highly efficient filters in the cabin air recirculation system
Introduction:
Nowadays, many aircraft types (including the Fokker 100) are equipped with a recirculation system, which maintains sufficient ventilation at a reduced fuel burn. The systems are additional to the basic Environmental Control System (ECS) which provides fresh air.
Although this method is effective in maintaining the comfort, the risk of catching a bacterial or viral infection is increased unless air filtration is improved. To reduce this risk to the original level associated with 100 % fresh air systems, optimum filtration of the cabin air to limit air contamination is essential.
Passenger standards for air quality are much higher than in the past and passengers are demanding a good and healthy environment especially in confined areas like an aircraft cabin. In reaction to the growing public interest on better air quality, comfort and health, several airline operators have launched programs to enhance the comfort in their aircraft and reduce the health risk introduced with recirculation systems.
To strive to better air quality, Fokker Services B.V. has certified new highly efficient cabin recirculation filters for the Fokker aircraft. These so-called HEPA (High Efficiency Particulate Arrestor) filters improve the comfort in the passenger cabin and reduce the risk of infections considerably by removing bacteria, viruses, tobacco smoke etc. in a more effective manner up to an efficiency of 99.997 %.
In addition, contamination of systems (outflow valves, cabin air-cooled avionics) as well as interior components are reduced.
The new HEPA filters have the highest attainable collecting efficiency.
| Cabin recirculation filters | ||
| Current type | New HEPA | |
| Filter efficiency for particle sizes of > 0.5 µm | exceeds 90 % | 100 % |
| Filter efficiency for particle sizes of 0,3 µm | 50 % | 99.997 % |
| Specification/Standard | ANSI/ASHREA 52.1-1992 90% dustspot European standardEN779, classification F7 |
DOP Mil-STD 282 European standard EN1822, classification H13 |
To put this in perspective, it should be realized that 99.9 % of the most harmful particles are smaller than 1 mm. Furthermore, the smaller the particles are, the further down into the lungs they get.| Typical particle sizes | |
| Tobacco smoke | 0.01 - 1 µm |
| Bacteria | 0.3 - 10 µm |
| Viruses | 0.002 - 0.06 µm |
| Micro organism harmful to the lungs | 0.5 - 5 µm |
| Smog | < 2 µm |
Other applications of HEPA filters include:
- sterile hospital operating rooms
- clean rooms class 100
- Sterile bacteriological laboratories
Interchangeability
The new HEPA filters are interchangeable with the current cabin recirculation filters and can be fitted without modification of the air filter housings. Replacement is simple because of the quick-release latches, which makes the introduction of these new HEPA filters easy with no effect on aircraft operation and availability.
The cabin air recirculation system of the Fokker 100 consists of 4 fans mounted at the top of the passenger compartment. Each fan installation includes four recirculation filters i.e. 16 filters are installed in the aircraft.
The present scheduled maintenance on the recirculation filters can be maintained although it is emphasized that the maximum service life of the HEPA filter may differ slightly from the present situation. This depends on the individual type of operation and the environment.
If your aircraft is equipped with the optional filter test system that allows in-situ measurement of the pressure drop over the filter installation in the cabin, the optimal replacement interval can easily be determined using the current limitations in the Aircraft Maintenance Manual.
Availability
The modification is certified for the Fokker 100 per Services Bulletin SBF100-21-069. Please contact your account manager for more details.