AIRCRAFT FUNCTIONAL TESTING AFTER REPAIR

FUNCTIONAL TESTING AFTER REPAIR

Following repair, and before in­spection plates, cover plates, or upholstering are replaced, test the entire system.

Open the cylinder valve slowly and observe the pressure gauge on a high-pressure system. A pressure of approximately 1,800 psi (at 70 °F) should be indicated on the gauge. (Cylinder pressure will vary considerably with radical temperature changes.)

(1)       Check the system by installing one of the mask hose fittings (minus the mask) in each of the cabin wall outlets to determine whether there is a flow. If a demand mask is used, check by breathing through the mask and, if appropriate, clean the mask according to paragraph 7.9.4.

(2)       Check the complete system for leaks in accordance with the procedure outlined in paragraph 9-49b(2)(d).

(3)       If leaks are found, close the cylinder valve and open an outlet to reduce the pressure in the system to zero.

The following checks may be made for a pressure drop check of the system.

(1)       Open the cylinder valve and pres­surize the system. Observe the pressure gauge (a pressure of approximately 1,800 psi at 70 °F should be indicated). For the light weight ICC 3HT 1850 cylinders, pressurize the sys­tem to approximately 1,850 psi at 70 °F.

(2)       Close the cylinder valve and wait approximately 5 minutes for temperatures to stabilize.

(3)       Record the pressure gauge reading and temperature and after 1 hour, record the pressure gauge reading and temperature again.

(4)       A maximum pressure drop of 100 psi is permissible.

NOTE: Conduct the above tests in an area where changes of temperature will be less than 10 °F. If a leak oc­curs during the 1-hour period, suit­able corrections would be required, or reconduct the test under conditions of unvarying temperatures.

SERVICE REQUIREMENTS OXYGEN CYLINDERS: Standard-weight cylinders must be hydrostatic tested at the end of each 5-year period. This is a Department of Transportation (DOT) requirement. These cylinders carry an ICC or DOT 3AA 1800 classification and are suitable for the use in­tended: The lightweight cylinders must be hy­drostatic tested every 3 years, and must be re­tired            from    service           after    24 years         or 4,380 pressurizations, whichever occurs first. These cylinders carry an ICC or DOT 3 HT 1850 classification and must be stamped with the approval after being in­spected.

CAUTION: Use only aviation breathing oxygen when having the oxygen bottle charged.

Charging High-Pressure Oxygen Cylinders: The following are recommended procedures for charging high-pressure oxygen cylinders from a manifold system, either per­manently-installed or trailer-mounted.

CAUTION: Never attempt to charge a low-pressure cylinder directly from a high-pressure manifold system or cylinder.

(1)       Inspection. Do not attempt to charge oxygen cylinders if any of the follow­ing discrepancies exist:

(a)    Inspect for contaminated fittings on the manifold, cylinder, or outside filler valve. If cleaning is needed, wipe with stabilized trichloroethylene and let air dry. Do not permit the solvent to enter any internal parts.

(b)    Check the hydrostatic test date of the cylinder. DOT regulations require ICC or DOT 3AA designation cylinders to be hydro­static tested to 5/3 their working pressure, every 5 years. Cylinders bearing designation ICC or DOT 3HT must be hydrostatic tested to 5/3 their working pressure every 3 years, and retired  from service15 years or 4,380 filling cycles after the date of manufac­ture, whichever occurs first.

(c)    If the cylinder is completely empty, do not charge. An empty cylinder must be removed, inspected, and cleaned before charging.

(2)       Charging:

(a)    Connect the cylinder valve outlet or the outside filler valve to the manifold.

(b)    Slowly open the valve of the cylinder to be charged, and observe the pres­sure on the gauge of the manifold system.

(c)    Slowly open the valve of the cyl­inder on the manifold system having the low­est pressure and allow the pressure to equalize.

(d)    Close the cylinder valve on the manifold system and slowly open the valve of the cylinder having the next highest pressure. Continue this procedure until the cylinder has been charged in accordance with 

.

(e)    Close all valves on the manifold system.

(f)     Close the valve on the filled cyl­inder and remove the cylinder from the mani­fold.

(g)    Using a leak detector, test for leakage around the cylinder valve threaded connections. (If leakage is present, discharge the oxygen and return the cylinder to the facil­ity for repair.)

(h)    Let the cylinder stabilize for a pe­riod of at least 1 hour, and then recheck the pressure.

(i)      Make any necessary adjustments in the pressure.

Charging of Low-Pressure Oxygen Systems and Portables. For recharging a low-pressure aircraft oxygen system, or port­able cylinders, it is essential that the oxygen trailer or cart have a pressure-reducing regu­lator. Military types E-2 or C-1 reducing regulators are ` satisfactory. These types of regulators reduce the large cylinder pressure from 2,000 psi to a line pressure of 450 psi. (A welding pressure-reducing regulator is not satisfactory.)

CAUTION: When refilling the low pressure system or portable cylinders, open the oxygen filler tank valve slowly to allow the system or portable cylinders to be filled at a slow rate. After the refilling operation is com­pleted, check for leaks with a leak de­tector. 

AIRCRAFT Lines and Fittings

Lines and Fittings:

(1)       Replace any oxygen line that is chafed, rusted, corroded, dented, cracked, or kinked.

(2)       Clean oxygen system fittings showing signs of rusting or corrosion in the threaded area. To accomplish this, use a cleaner recommended by manufacturers of oxygen equipment. Replace lines and fittings that cannot be cleaned.

(a)    The high-pressure lines which are located between the oxygen bottle (outside the oxygen service filler) and the regulator are normally fabricated from stainless steel or thick=wall, seamless copper alloy tubing. The fittings on high-pressure lines are normally silver brazed.

NOTE: Use silver alloys free of cad­mium when silver brazing. The use of silver brazing alloys, which contain cadmium, will emit a poisonous gas when heated to a molten state. This gas is extremely hazardous to health if inhaled.

(b) The low-pressure lines extend from the pressure regulator to each passenger and crew oxygen outlet. These lines are fabricated from seamless aluminium alloy, copper, or flexible hose. Normally, flare- or flange type connections are used.

CAUTION: Do not allow oil, grease, flammable solvent, or other combusti­bles such as But or dust to come in contact with threads or any parts that will be exposed to pressurized oxygen.

(c)    It is advisable to purge the oxy­gen system any time work has been accomplished on any of the lines and fittings. Use dry nitrogen or dry air for purging the system. All open lines should be capped immediately after purging.

(d)    When oxygen is being lost from a system through leakage, a sequence of steps may be necessary to locate the opening. Leak age may often be detected by listening for the distinct hissing sound of escaping gas. If this check proves negative, it will be necessary to soap-test all lines and connections with a cas­tile soap and water solution or specially com­pounded leak-test material. Make the solution thick enough to adhere to the contours of the fittings. At the completion of the leakage test, remove all traces of the soap and water.

Regulators, Valves, and Gauges: Line maintenance of oxygen regulators, valves, and gauges does not include major repair. These components are precision made and their re­pair usually requires the attention of a repair station or the manufacturer. Care must be taken when reinstalling these components to ascertain if the threaded area is free of nicks, burrs, and contaminants that would prevent the connections from sealing properly.

CAUTION: Do not use petroleum lu­bricants on these components.

Masks and Hoses:

(1)       Troubleshooting. If a mask assem­bly is defective (leaks, does not allow breath­ing, or contains a defective microphone), it is advisable to return the mask assembly to the manufacturer or a repair station.

(2)       Maintenance Practice and Cleaning.

(a)    Clean and disinfect the mask as­semblies after use, as appropriate.

NOTE: Use care to avoid damaging the microphone assembly while cleaning and sterilizing.

(b)    Wash the mask with a mild soap solution and rinse it with clear water.

(c)    To sterilize, swab the mask thor­oughly with a gauze or sponge soaked in a water merthiolate solution. This solution should contain 1/5-teaspoon of merthiolate per 1 quart of water. Wipe the mask with a clean cloth and air dry.

(d)    Replace the hose if it shows evi­dence of deterioration.

(e)    Hoses may be cleaned in the same manner as the mask.

(f)     Observe that each mask breathing tube end is free of nicks, and that the tube end will slip into the cabin oxygen receptacle with ease and not leak.

AIRCRAFT OXYGEN SYSTEMS

Oxygen Systems      

During the maintenance of the oxygen system, the aircraft manufacturer's information must be followed along with the safety requirements men­tioned earlier. Some general rules concerning oxygen system maintenance that must be followed are: keep hands, tools and working area clear of grease, dirt, water and all foreign matter. All oxygen system components must be keep clean and dry until they are installed. The use of com­pounds on fitting threads is normally not allowed unless the aircraft service manual calls for their use. Always check the oxygen cylinder for con­tamination, the hydrostatic test date, and for being completely empty. If the cylinder is found to be completely empty the cylinder generally needs to be sent for a complete inspection by an FAA ap­proved repair station. After a thorough inspection of all the components in the system, an operational check should be performed to ensure the system is functioning normally. The specific inspection procedures for the aircraft that is being serviced will be in the aircraft's service manual; follow these closely.

The following instructions are to serve as a guide for the in­spection and maintenance of aircraft oxygen systems. The information is applicable to both portable and permanently-installed equipment.

7.7.1 Aircraft Gaseous Oxygen Systems: The oxygen in gaseous systems is supplied from one or more high or low-pressure oxy­gen cylinders. Since the oxygen is compressed within the cylinder, the amount of pressure in­dicated on the system gauge bears a direct re­lationship to the amount of oxygen contained in the cylinder. The pressure-indicating line connection is normally located between the cylinder and a pressure-reducing valve.

NOTE: Some of the gaseous oxygen systems do not use pressure-reducing valves. The high pressure is reduced to a useable pressure by a regulator. This regulator is located between the high- and low-pressure system.

CAUTION: Oxygen rich environ­ments are dangerous.

7.7.2   Portable Oxygen Systems: The three basic types of portable oxygen systems are: demand, pressure demand, and continuous flow. The components of these systems are identical to those of a permanent installation with the exception that some parts are minia­turized as necessary. This is done in order that they may be contained in a case or strapped around a person's shoulder. It is for this port­ability reason that special attention be given to assuring that any storage or security provision for portable oxygen equipment in the aircraft is adequate, in good condition, and accessible to the user.

NOTE: Check portable equipment including its security provisions fre­quently, since it is more susceptible to personnel abuse than a permanently installed system.

INSPECTION

Hands, clothing, and tools must be free of oil, grease, and dirt when working with oxygen equipment. Traces of these organic materials near compressed oxy­gen may result in spontaneous combustion, explosions, and/or fire.

Oxygen Tanks and Cylinders: In­spect the entire exterior surface of the cylinder for indication of abuse, dents, bulges, and strap chafing.

(1)       Examine the neck of cylinder for cracks, distortion, or damaged threads.

(2)       Check the cylinder to determine if the markings are legible.

(3)       Check the date of the last hydro­static test. If the periodic retest date is past, do not return the cylinder to service until the test has been accomplished.

(4)       Inspect the cylinder mounting bracket, bracket hold-down bolts, and cylin­der-holding straps for cracks, deformation, cleanliness, and security of attachment.

(5)       In the immediate area where the cylinder is stored or secured, check for evi­dence of any types of interference, chafing, de­formation, or deterioration.

 Lines and Fittings:

(1)       Inspect oxygen lines for chafing, corrosion, flat spots and irregularities, i.e., sharp bends, kinks, and inadequate security.

(2)       Check fittings for corrosion around the threaded area where lines are joined. Pres­surize the system and check for leaks. See paragraph 7.9.2(2) (d)

CAUTION: In pressurizing the sys­tem, actuate the valve slowly to avoid surging which could rupture the line.

Regulators, Valves, and Gauges:

(1)       Examine all parts for cracks, nicks, damaged threads or other apparent damage.

(2)       Actuate the regulator controls and the valve to check for ease of operation.

(3)       Determine if the gauge is function­ing properly by observing 'the pressure build-up and the return to zero when the system oxygen is bled off.

Masks and Hoses:

(1)       Check the oxygen mask for fabric cracks and rough face seals. If the mask is a full-face model, inspect the glass or plastic for cleanliness and state of repair.

(2)       When appropriate, with due regard to hygienic considerations, the sealing quali­ties of an oxygen mask may be tested by placing a thumb over the connection at the end of the mask tube and inhaling very lightly. Re­move the thumb from the disconnect after each continuous inhalation. If there is no leakage,, the mask will adhere tightly to the face during inhalation, and definite resistance to inhalation will be noticeable.

(3)       Flex the mask hose gently over its entirety and check for evidence of deteriora­tion or dirt.

(4)       Examine the mask and hose storage compartment for cleanliness and general con­dition.

(5)       If the mask and hose storage com­partment is provided with a cover or release mechanism, thoroughly check the operation of the mechanism.

MAINTENANCE.

Oxygen Tanks, Cylinders, and Hold Down Brackets.

(1)       Remove from service any cylinders that show signs of abuse, dents, bulges, cracks, distortion, damaged threads, or defects which might render them unsafe. Typical examples of oxygen cylinder damage..

(2)       When replacing an oxygen cylinder, be certain that the replacement cylinder is of the same size and weight as the one removed.

AIRTCRAFT PREVENTION OF OXYGEN FIRES OR EXPLOSIONS

Prevention Of Oxygen Fires Or Explosions

Safety precautions for oxygen servicing are similar to those required for fuelling or refuelling an aircraft. The airplane and service cart should be electrically grounded and all vehicles should be kept a safe distance away. There should be no smoking, open flame or items which may cause sparks within 50 feet or more depending upon the ventilation of the area during servicing operations. Since the clothing of a person involved in servicing an oxygen system is likely to be permeated with oxygen, no one should smoke within ten or fifteen minutes after completing the oxygen servicing.

The most important consideration when servic­ing any type of oxygen system is the necessity for absolute cleanliness. The oxygen should be stored in a well ventilated part of the hangar away from any grease or oil, and all high pressure cylinders not mounted on a service cart should be stored upright, out of contact with the ground and away from ice, snow or direct rays of the sun. Protective caps must always be in place to prevent possible damage to the shutoff valve. The storage area for oxygen should be at least 50 feet away from any combustible material or separated from such material by a fire resistant partition. When setting up an oxygen storage area, you should be sure that it meets all of the requirements established by your insurance company and by both Federal and State Occupational Safety and Health Act (OSHA).

Because of the extreme incompatibility of oxygen and any form of petroleum products, it is a good idea to set aside some tools to be used exclusively with oxygen equipment. Any dirt, grease or oil that may be on the tools or on any of the hoses, adapters, cleaning rags, or even on your clothing is a possible source of fire.

AIRCRAFT REPLACING TUBING, VALVES AND FITTINGS

Replacing Tubing, Valves And Fittings

It is extremely important when installing any oxygen line in an aircraft that no petroleum product is used as a thread lubricant, and that the lines are thoroughly cleaned of any trace of oil that was used in the flaring or presetting operation. Trichloroethylene or some similar solvent may be used to clean the tubing and fittings, and after they are thoroughly clean, they should be dried either with heat or by blowing them dry with water­ pumped dry air or dry nitrogen.

Tapered pipe threads must never be lubricated with a thread lubricant that contains any form of petroleum. Oxygen-compatible thread lubricant that meets specification MIL-T-5542 maybe used, or the male threads may be wrapped with Teflon tape and the fittings screwed together.

Before any tubing or fitting is replaced in an oxygen system, the part must be thoroughly cleaned and inspected. Check the part for evidence of corrosion or damage, and degrease it with a vapour degreaser or ultrasonic cleaner. Flush the new line with stabilized trichloroethylene, acetone, or some similar solvent, and dry it thoroughly with water-pumped dry air or nitrogen. If neither water pumped air nor nitrogen are available, the part may be dried by holding it at a temperature of about 250 °F until it is completely dry. When the parts are dry, close them with properly fitting protective caps or plugs, but never use tape in any form to seal the lines or fittings, as small particles of the tape are likely to remain when it is removed. 

AIRCRAFT FILLING A LIQUID OXYGEN SYSTEM

 Filling A Liquid Oxygen System

Service carts for liquid oxygen normally carry the LOX in 25- or 100-liter containers. Servicing systems from these carts is similar to that described in the previous section on gaseous oxygen systems. And here again, cleanliness and care are of the utmost importance. Liquid oxygen has such a low boiling point that it must not be spilled on your skin; it would be sure to cause serious frostbite. Protective clothing and an eye shield must be worn.

Before servicing an empty LOX system or one that hasn't been in use for some time, you should purge it for a few hours with heated water pumped dry air or nitrogen.

Attach the service cart to the aircraft system and, after placing the build-up and vent valve in the vent position, open the valve on the service cart. As the LOX flows from the service cart into the warm converter, it vaporizes rapidly and cools the entire system. Considerable gaseous oxygen is released during the filling procedure, and it vents to the outside air through the build-up and vent valve. This venting of the gaseous oxygen will continue until liquid oxygen starts to flow out of the vent valve. A steady stream of liquid indicates that the system is full.

Be sure that the system vents freely as it is being filled and that frost forms only on the outlet and the hoses. If any frost forms on the supply con­tainer, it could be an indication of an internal leak, and since the pressure can build up extremely high, any trace of a leak demands that the equip­ment be shut down immediately and the cause of the frosting determined.

When you attach the liquid oxygen cart to the aircraft system, open the valve fully, then close it slightly. If you do not do this, it is possible that the oxygen flowing through the valve could cause the valve to freeze in the open position and it may be difficult or impossible to close.

There are two ways LOX converters are serviced. Some are permanently installed in the aircraft and are serviced from an outside filler valve. The build-up and vent valve is placed in the vent position, the service cart is attached to the filler valve, and liquid oxygen is forced into the system until liquid runs out of the vent line. When the system is full, the build-up and vent valve is returned to the build-up position to build up pressure in the converter. Other installa­tions have quick-disconnect mounts for the con­verters so the empty converter can be removed from the aircraft and replaced with a full one. Exchanging converters allows oxygen servicing to be done much more quickly and safely than can be done by filling the converter in the aircraft.

Inspecting the masks and hoses disposable masks such as those used with many of the portable systems should be replaced

with new masks after each use, but the permanent masks used by crew members are normally retained by the individual for his exclusive use. These masks are fitted to the face to exclude leakage and are usually treated as personal flight gear. They should be occasionally cleaned with a lukewarm detergent bath by washing them with a cloth wet with the detergent solution and then allowing them to dry at room temperature. The face portion of the mask may be disinfected with a mild antiseptic.

Check the masks and hoses for leaks, holes or rips, and replace them rather than attempting to repair any damaged component. When storing the mask in the airplane, be sure to protect it from dust and dampness, and especially from any type of grease or oil.

OXYGEN SYSTEM SERVICING, INSPECTION AND MAINTENANCE PRACTICES

Oxygen System Servicing, Inspection And Maintenance Practices

 INTRODUCTION

Oxygen system requires some careful maintenance activities. This week highlight different type of  servicing, inspection and maintenance procedures.

  Oxygen System Servicing: GENERAL

Care and attention to detail is the mark of professional aviation maintenance, and nowhere is this characteristic more important than when servicing aircraft oxygen systems. Compressed gaseous oxygen demands special attention be­cause of both its high storage pressure and its extremely active chemical nature.

When possible, all oxygen servicing should be done outdoors, or at least in a well ventilated area of the hangar. Oxygen systems having removable or portable supply cylinders should have these containers removed from the operation, and all electrical work within the aircraft should be suspended during the servicing. In all cases the manufacturer's service information must always be used while performing service, maintenance or inspection on aircraft oxygen systems.

Servicing Gaseous Oxygen Systems

  Leak Testing Gaseous Oxygen Systems:  Leaks should be searched out by using a special leak detector material which is a form of non-oily soap solution. Spread this solution over every fitting and at every place a leak could possibly occur, and the presence of bubbles will indicate a leak. If a leak is found, release the pressure from the system, and check the fittings for proper torque. It is especially true of flare less fittings where over tightening can intensify a leak. If the fitting is properly torqued and still leaks, remove the fitting and examine all of the sealing surfaces for indication of damage. It may be necessary to replace the fitting and reflare the tube or install a new flare less fitting.

Draining The Oxygen System: Draining of the oxygen system should normally be done after the high pressure bottle has been removed or isolated from the system. Either out­doors or in a well ventilated hangar, open the aircraft's doors and windows, then bleed the system's pressure off by opening the appropriate fitting to allow the oxygen pressure to bleed off. Normally a system will require purging after the system has been drained. All the safety precau­tions mentioned later in this chapter should be followed during any oxygen draining procedure.

 Filling An Oxygen System: Fixed base operators who do a considerable amount of oxygen servicing will usually have one of the larger oxygen servicing carts such as the one seen in Figure 7.1. This cart carries six large cylinders, each holding approximately 250 cubic feet of aviators breathing oxygen. A seventh cylinder, facing the opposite direction and filled with compressed nitrogen, is normally carried to charge hydraulic accumulators and de-icer cylinders. Fittings on the nitrogen cylinders are different from those on the oxygen cylinders, to minimize the possibility of using nitrogen to fill the oxygen system, or of servicing the other systems with oxygen.

If you ever fill a low-pressure oxygen system from a high-pressure supply, be sure the proper regulator is installed and the output pressure is adjusted to that required for the system.

Various manufacturers of oxygen equipment use different types of connections between the supply and the aircraft, and a well equipped ser­vice cart should have the proper adapters. These adapters must be kept clean and protected from damage. Never improvise when adapting a supply cart to the aircraft. Leakage during the filling operation is not only costly, but it is hazardous as well.

Before filling any aircraft oxygen system, be sure that all of the cylinders are of the approved type, and that they have all been hydrostatically tested within the required time interval.

No oxygen system should be allowed to become completely empty. When there is no pressure in­side the cylinder, air can enter, and most air contains water vapour. When the water vapour is mixed with the oxygen and expanded through the small orifices in the system, the water is likely to freeze and shut off the flow of oxygen to the masks. Water in a cylinder can also cause it to rust on the inside and weaken it so it will fail with catastrophic results. A system is considered to be empty when the pressure gets down to 50 to 100 psi. If the system is ever allowed to get completely empty, the valve should be removed and the cylinder cleaned and inspected by an FAA-approved repair station.

When filling an airplane from a large supply cart, start with the cylinder having the lowest pressure. The pressure should be written on the container with chalk or a record kept with the cart. Momen­tarily crack the valve on the cylinder and allow some oxygen to purge all of the moisture, dirt and air from the line; then connect the line to the aircraft filler valve and slowly open the valve on the cylinder. Most all filler valves have restrictors that prevent too high a flow rate into the cylinder. When the pressure in the aircraft system and that in the cylinder with the lowest pressure stabilizes and there is no more flow, mark this pressure on the cylinder with chalk and close the cylinder valve. Slowly open the valve on the cylinder having the next lowest pressure and allow oxygen to flow into the system until it again stabilizes. Continue this procedure until the pressure in the aircraft system is that which is required.

The ambient temperature determines the pres­sure that should be put into the oxygen system, and a chart similar to the one in should be used to determine the pressure needed. For example, if the ambient temperature is 90 °F and you want a stabilized pressure in the system of 1,800 psi, you should allow the oxygen to flow until a pressure of 2,000 psi is indicated on the system pressure gauge. When the oxygen in the system drops to its standard temperature of 70 °F, the pressure should stabilize at 1,800 psi. If the ambient temperature is low, you must stop filling the system at a lower pressure, because the oxygen will expand and the pressure will rise when it warms up to its standard temperature.\

Purging A Gaseous Oxygen System: If the oxygen system has been opened for servic­ing, you should purge it of any air that may be in the lines. To purge a continuous flow system, plug masks into each of the outlets, turn on the oxygen supply valve, and allow the oxygen to flow through the system for about ten minutes. Diluter demand and pressure demand systems may be purged by placing the regulators in the EMERGENCY posi­tion and allowing the oxygen to flow through them for about ten minutes. After the system has been thoroughly purged, fill the cylinders to the re­quired pressure.

AIRCRAFT MISCELLANEOUS EQUIPMENT

MISCELLANEOUS EQUIPMENT

Parachutes. With reasonable care, parachutes can remain in service indefinitely. They should not be carelessly tossed about, left in aircraft to become wet, or left where someone may tamper with them. They should not be placed where they may fall on oily floors or be subject to acid fumes from adja­cent battery chargers.

(1)       When repacking is scheduled, to comply with the 120-day requirement in Ti­tle 14 of the Code of Federal Regulation (14 CFR) part 105 section 105.43 a careful in­spection of the parachute shall be made by a qualified parachute technician (rigger). If re­pairs or replacements of parts are necessary to maintain the airworthiness of the parachute as­sembly, such work must be done by the origi­nal parachute manufacturer or by a qualified parachute rigger, certificated in accordance with 14 CFR, part 65.

(2)       The lead seal should be inspected periodically to ensure the thread has not been broken.  If broken, or broken and retied or appears to have been tampered with, the para­chute must be repacked by a properly certified rigger.

Safety Belts. All seat belts and re­straint systems must conform to standards es­tablished by the FAA. These standards are contained in Technical Standard Order TSO C22 for seat belts and TSO C 114 for re­straint systems.

(1)       Safety belts eligible for installation in aircraft must be identified by the proper TSO markings on the belt. Each safety belt must be equipped with an approved metal to metal latching device. Airworthy type certificated safety belts currently in aircraft may be removed for cleaning and reinstalled. However, when a TSO safety belt is found un­airworthy, replacement with a new TSO-approved belt or harness is required.

(2)       The webbing of safety belts, even when mildew-proofed, is subject to deteriora­tion due to constant use, cleaning, and the effects of aging. Fraying of belts is an indication of wear, and such belts are likely to be unair­worthy because they can no longer hold the minimum required tensile load.