Abbreviated Component Maintenance Manual
p/n’s 40997001, 40997002, 40997003

1. GENERAL

Ozone is a form of oxygen that is found naturally in the upper atmosphere. Ozone enters the airplane cabin with the outside air at high altitudes through the air conditioning system.

Often, some symptoms attributed to "jet lag" or "air sickness" may actually be caused by ozone in the cabin air in high flying aircraft.

Headaches, fatigue, shortness of breath, coughing, irritation of the eyes, nose, or throat and chest pains are some of the conditions that can be experienced by exposure to ozone.

Because of the adverse effects of ozone, the FAA regulates airplane cabin ozone concentration not to exceed 0.25 ppm(volume) at any point in time or 0.1 ppm(volume) on a time weighted average.

The catalytic converter is mounted in the air conditioning ducts of the aircraft. The converter contains a catalyst which causes the ozone to decompose to oxygen. The catalyst does not take part in the chemical reaction and, therefore, is not used up.

2. TESTING FAULT ISOLATION

The only mode of failure of the converter is through very gradual deactivation of the catalyst. That is, the catalyst ceases to convert ozone to oxygen. The catalyst is deactivated by the contaminants in the air entering the cabin. The contaminants deposit on the surface of the catalyst, thereby, preventing the ozone from reaching the surface of the catalyst. However, the contaminants are present in only a very thin layer and, therefore, do not prevent or effect the flow of air through the converter.

The only method of testing the converter is to pump large amounts of heated air containing ozone through it. In this test, the amount of ozone converted to oxygen is measured. Then the percentage of ozone converted to oxygen, or efficiency, can be calculated. Contact Engelhard for information regarding return of converters for testing.

The operator must determine if the ozone converter efficiency is adequate to maintain the ozone concentration in the cabin below the levels specified in FAR 121.578. An acceptable method for calculating the minimum allowable ozone converter efficiency is given in FAA advisory circular AC 120 38 dated 10/10/80.

Three calculations are required. The ratio of cabin pressure(P) to sea level pressure(Po) must be calculated. Then, one must determine the efficiency necessary to ensure that the maximum cabin ozone concentration is below 0.25 ppmv and, in addition, must show that the time weighted average of 0.1 ppmv is not exceeded for each flight segment that exceeds 4 hours.

The aircraft manufacturer has recommended that the following value be used for the retention ratio(R):
R=0.34 (34% of the ambient ozone enters the cabin)

The following example assume that operator X wishes to use an A330/340 aircraft on a six hour route in the eastern North American region, where the expected cruise altitude will be 40000 feet. The take off altitude will be 5000 feet. The numbers used in the calculation are for example only. The operator should consult the FAR and determine the numbers to be used for the flight route.

The aircraft manufacturer has determined the ratio of cabin pressure(P) to sea level pressure(Po) is to be calculated using the cabin pressure, ambient pressure, and take off altitude shown in TABLE 1. The following is an example of the calculation of P/Po.

Refer to TABLE 1. For an expected cruise altitude of 40000 feet and a take off altitude of 5000 feet, the cabin pressure will be 10.85 psi.
P/Po=10.85/14.696=.739

The following example calculation shows the converter efficiency necessary to limit the cabin ozone concentration to a maximum of 0.25 ppmv in the A330/340.

At flight level 400, the maximum ozone concentration at an 84% confidence level is found to be 1.15 ppmv(OZ16) during February at 80 degrees north latitude in the eastern North American region. This ozone concentration is obtained from AC 120 38, page 15.

Minimum required converter efficiency:
=(1 [0.25/(OZ16)(R)(P/Po)])100
=(1 [0.25/(1.15)(.34)(.739)])100
=13%

The following calculation shows the converter efficiency necessary to limit the time weighted average ozone concentration to 0.1 ppmv.

Assume total flight segment time(Tfs) is 6 hours and flight level is 400.

Minimum required converter efficiency:
={1 [(0.1)(Tfs)/(OZ16)(R)(P/Po)(Tfs 1)]}100
={1 [(0.1)(6)/(1.15)(.34)(.739)(5)]}100
=58%

In this example calculation, the minimum required converter efficiency must be the highest of the two above calculated cases, that is, 58%. Thus, if the converter test efficiency is 49%, for example, the converter must be repaired or scrapped.

There are additional examples in the FAR if the operator wishes to use other conditions regarding ambient ozone concentration, flight time, and/or flight level.

After the efficiency has been determined by testing at Engelhard, the operator can determine how much longer the converter can be installed on the aircraft. The reduction in efficiency is estimated to be 0.003%/flight hour.

An example is given below to show how this information can be used to predict how much longer a converter can be used.
Assume: 76% Test efficiency
58% Minimum required efficiency

Remaining flight hours=(76 58)/0.003 = 6,000 flight hours

The above calculation is only an estimate. We recommend that a converter be returned to Engelhard for testing at the recommended flight hour duration published in the Airbus Industrie Maintenance Planning Document. This will assist the operator and Engelhard in developing more accurate predictions of efficiency vs. flight hours.


3. DISASSEMBLY

The converter is of all welded construction and should not be disassembled in the field. The converter should be disassembled only by Engelhard because of the requirement to maintain the proper fit between the internal parts. Improper assembly can result in failure of the internal parts.


4. CLEANING

The inside of the converter should not be cleaned in the field. The use of improper cleaning techniques or chemicals can permanently deactivate the catalyst.

5. CHECK

The converter must be returned to Engelhard for testing. The only check that can be done in the field is for obvious internal or external damage.


6. REPAIR

The converter is a line replaceable unit and is, therefore, not repairable in the field. See DISASSEMBLY.
The converter can be repaired by Engelhard if testing by Engelhard indicates that the catalyst must be replaced. P/N’s 40997001 and 40997002 are no longer in production, however, they can be returned to Engelhard for replacement of catalyst. See TESTING FAULT ISOLATION.
Contact Engelhard for information regarding return of converters for testing and/or repair.


7. ASSEMBLY (INCLUDING STORAGE)

Assembly is not applicable.

The converter should be stored in the shipping container and indoors. There are no limitations on storage temperature or humidity. The shelf life is indefinite.

8. FITS AND CLEARANCES

Not applicable because the converter is not field repairable.


9. SPECIAL TOOLS, FIXTURES, AND EQUIPMENT

The converter does not require any special tools, equipment, or preparation for installation. The converter does not require any special preparation for return to Engelhard for testing. Protective caps should be placed on the converter flanges and the converter shipped in the original container.


10. DIMENSIONS AND WEIGHT

Dimensions in inches(mm)

P/N 40997001. Maximum weight 25.5 pounds (11.6 kg):

P/N 40997002. Maximum weight 13.6 pounds (6.19 kg):

P/N 40997003. Maximum weight 13.6 pounds (6.10 kg):

TABLE 1

CABIN PRESSURE

dependence on

AMBIENT PRESSURE AND TAKE OFF ALTITUDE