AC 43.13-1A 1972 number "1", "2", etc., to signify the sequential number of retreads applied thereon.
(b) Display the speed category increase if the tire is qualified for the increased speed in accordance with the requirements specified in FAR 87.167 (Technical Standard Order TSO-
(c) Display the month and year of retread application.
(d) Display the name of the person retreading the tire.
(7) Balance. Each repaired or retreaded tire should not exceed the static unbalance limits as forth in Technical Standard Order TSO-C62.
(8) Tire Installation. Install the tire on the wheel in such a manner that the tire-bead chafing area will not be torn or the tube pinched during the mounting process. When mounting tubeless tires, use procedures that assure a positive seal between the tire-bead and the wheel-rim area.
(9) Clearance. For retractable landing gears, maintain sufficient clearance between the tire and the surrounding structure during the retraction process. Carefully check clearances following installation of wheel assemblies equipped with retreaded tires because of the growth factor which may have increased the tire diameter and cross section.
b. Refreading Types VIl and VIll High-Speed Tires. The following paragraphs describe ways of substantiating the acceptability of methods, techniques, and practices to be used in retreading of high-speed tires. Other methods may be
(1) Number of Retreads. The wide variation in tire operating environments which may affect total carcass life and serviceability makes it inadvisable to prescribe arbitrarily the maximum number of times a high-speed tire should be retreaded. This aspect, therefore, is controlled by thorough inspection of the carcass before retreading.
(2) Condition of Tire to be Retreaded. Retread only those tire carcasses found serviceable by thorough inspection. During inspection, use equipment, techniques, and procedures which Chap 6 Page 147 are recommended by the tire manufacturer or that are equivalent to those in general use by FAA certificated repair agencies rated for retreading of high-speed aircraft tires. Determine the acceptability of damaged tires for retreading in accordance with established industry practices.
(3) Retreading Criteria,
(a) Processes, Methods, Techniques, Pracfices, and Equipment. The suitability of specific retread manufacturer's injury limitations, retreading processes, and equipment used is determined either by satisfactory service experience or substantiating tests.
(b) Materials. The acceptability of materials used in a retreading process may be determined by following the tire manufacturer's recommendations, or the materials may be sub- • stantiated by analysis and tests, such as dynamometer testing, or through satisfactory service experience.
(c) Unbalance. The moment of static unbalance in ounce-inches shall be no greater than the following moment values:
1. Tire diameters up to and including 28 inches: Moment = 01D' + 38D.
2. Tire diameters greater than 28 inches: Moment = 034D' - .804D.
D = Tire diameter (actual).
(d) Balance Marker. To indicate the lightweight point of the tire, remove old balance marker, and durably affix a new relocated balance marker, consisting of a single red dot of appropriate size to the sidewall of the tire immediately above the bead.
(e) Burst Pressure. Retreaded tires shall be capable of withstanding without failure, a burst pressure of at least 8 times the rated inflation pressure.
(f) Temperature. The airworthiness of retreaded tires shall not be adversely affected as a result of their being subjected to extreme ambient temperatures expected to be encountered during normal airplane operation.
(g) Tread Design. Substantiate decreases or increases in the number of tread ribs and grooves and changes in skid depth by dynamometer tests that are applicable to the tire groundspeed range.
Par 332
(h) Underskld Thickness. The thickness of the rubber between the carcass and the bottom of the tread pattern (underskid) is not normally less than 80% of the mold skid depth.
Requalify by dynamometer test, tire underskid/ tread thickness which is greater than that previously qualified.
(I) Venting. Substantiate changes in venting pattern by dynamometer test.
(4) Marking and Identification. Do not obliterate the original manufacturer's marking and identifying data, unless it is necessary for proper retreading or repair. Permanently emboss the tire sidewall with retread information. If necessary, replace original identifying markings and include the following retread identification:
(a) Name of identifying letters of the retreading company.
(b) The letter "R" followed by a numeral "1", "2", etc., to signify frst, second, etc., time the tire has been retreaded.
(c) Plant location of the retread manufacturer.
(d) Month and year of retread in numerical figures.
(•) If the dynamometer retread qualification speed is less than the previous (original) tire qualification speed, remove the previous speed marking and indicate the new (lower) rated speed. Identify tires that have been retreaded for use only on aircraft of a specific make/model and type design.
(5) Quality Control. The retreader's quality control system will be expected to maintain a satisfactory level of workmanship throughout the retreaded process including assurance that each retreaded tire is vented to prevent tread breakdown or separation.
(6) Records of Work Performed. Include at least the following information in the retreader's work record for each tire processed:
(a) Tire size.
(b) Ply rating.
(c) Speed rating.
(d) Serial number.
(•) Retread number.
(f) Type of tread applied.
(g) Month and year applied.
Par 332 AC 43.13-1A 1972
(7) Dynamometer tests. An acceptable means of determining that the methods, techniques, and practices utilized in the retread process will produce a tire that meets the requirements of FAR 48.18 is by subjecting a representative tire to the following dynamometer tests:
(a) General, Load-speed-time data compiled by the airplane manufacturer is the basis for establishing representative dynamometer tests. To determine tire performance, simulate the most critical combination of takeoff weight, speed, and airplane center-of-gravity position. Also, consider increased speeds resulting from elevated airport operations and high ambient temperatures.
(b) Selection of Tires for Qualification Testing. Retread only tires that are worn at least 80% from actual aircraft useage or which have undergone simulated equivalent operation during dynamometer testing. The sample retreaded tire must be properly identified and bear the qualifying retreaders markings.
(c) Test Inflation Pressure. Inflate the sample tire to the pressure necessary to obtain the same defection on the flywheel (under the rated static load) as the flat-plate deflection the tire would have at its rated static load and inflation.
(d) Test Speeds. The applicable dynamometer test speeds corresponding to the maximum operational groundspeeds are as follows:
lium operation prold speed of alreract Dynamometer test speed (m.p.h.)
Over Not over 160 180 180 180 200 200 200 225 226 225 250 250
(e) Test Landing Interval. Schedule minimum time between landings to assure carcass peak temperatures of not less than 160° F. or contained air peak temperatures of not less than 140° F. for each run. Measure the carcass temperatures within 1 inch of the rim flange and also in the shoulder or crown area. Record any unavoidable deviations in the substantiating test data.
(8) Dynamometer Test Procedures. The highspeed retreaded tire shall withstand 100 dynamometer landings and at least three taxi-test Chap •
AC 43.13-1A CHG 1 1975 cycles. The dynamometer landings will consist of 50 Test A, load-speed-time cycles and 50 Test B, energy cycles.
(a) Test A, Load-speed-time.
I. Speed cycle. Land the tire against a dynamometer flywheel rotating at n peripheral speed of S, m.p.h. Immediately thereafter, decrease the flywheel speed at an average deceleration rate of D ft./sec./sec. until a value of S, is attained. No specific rate of deceleration is required after the flywheel's peripheral speed reaches a value of S2. Decrease the speed of the flywheel in the above manner until a roll distance of RD feet has been covered, at which time the tire is unlanded.
2. Load cycle. After landing, increase the load from zero to L, pounds within T, seconds. Linearly increase the load with time to a value of Is pounds within T, seconds after landing, or at the moment of unlanding, whichever occurs first. If it is necessary to continue the roll after Ta seconds to complete the required roll distance (RD), maintain the load at L pounds.
3. Symbol definitions. Determine the numerical values, which are used for the following symbols, from the applicable airplane load-speed-time data:
S, = Initial dynamometer test speed.
S=Speed at which the average deceleration between S, and S, does not exceed the specified values.
D=Constant rate of deceleration between S, and S, speeds.
RD = Roll distance in feet.
I, = Initial tire load.
L=Maximum rated static load of the tire.
T, =Time for applying L, load. A T, tolerance of +1 second is acceptable.
S1-VS -2D (RD) T¿= D T, is the elapsed time for applying the Ly load A T, tolerance of +10% is acceptable.
When T, is calculated by the aforementioned formulu, S, may be ignored and D is assumed constant throughout roll distance (RD).
Chap 8 Page 149
4. Test load adjustment. If the test load curve results in loads at a given speed being less than those dictated by the applicable aircraft data, eliminate the condition by making adjustments in Ta, L, and/or T1
(b) Test B, Energy.
1. Kinetic energy. Calculate and adjust the kinetic energy of the flywheel for the rated maximum static load of the tire. In the event that the correct number of flywheel plates cannot be used to obtain the calculated kinetic energy value or proper flywheel width, select a greater number of plates and adjust the dynamometer speed to achieve the required kinetic energy.
2. Kinetic energy computation. Compute kinetic energy as follows:
KE=CWV:
Where KE = Kinetic energy, ft.-lb.
C=0.011 W=tire load, pounds V = 120 m.p.h.
3. Speed cycle. Land the test tire at 90 m.p.h. and unland at 0 m.p.h. Decrease the landing speed as necessary to assure that 56% of the calculated kinetic energy is absorbed by the tire.
4. Load cycle. Upon landing, and during the entire roll test, force the tire agninst the flywheel at its rated static load.
(c) Taxi Test.
1. Test parameters. Conduct a minimum of three dynamometer taxi tests under the following conditions:
Speed = 35 m.p.h.
Tire Load = Maximum static rating Roll Distance =35,000 feet.
2. Tire temperature. Heat the test tire to a temperature of not less than 120° F. at the start of each of the three taxi test cycles. Rolling the tire on the dynamometer is acceptable in obtaining this minimum tire temperature.
Make no adjustments in the tire inflation pressure to compensate for increases due to temperature rise.
(9) Alternate Dynamometer Tests.
(a) Variable Loading. An alternate dynamometer test which more realistically simulates Par 332
Page 150 AC 43.13--1A CHG 1 1975 actual airplane performance on the runway may be used in lien of the deceleration load-speedtime schedule, An acceleration lead-sperd-time tube is not pinched. A pinched tube will chafe against the walls of the carcass and a thin spot will result in the rubber. In time, the tube wall schedule, wherein the dynamometer flywheel is will leak at this point. The pinching generally accelerated to the applicable conditions, is accept- is due to the sticking of the tube to the cauass wall during the first inflation and the failure
(b) Alternate Procedure for Reinforced-tread of the carcass to properly seat against the flange.
Tires. Qualification of a high-speed tire with (d) The tube is then confined to a smaller a given ply rating and reinforced tread will an space and wrinkling (pinching) of the tube retomatically qualify a lesser ply rating reinforced sults. Complete deflation followed by inflation tread tire of the same size and skid depth, pro- allows the tube to properly accommodate itself to the careass which should now seat it-elf tightly
1. The test conditions S, RD, S., Th against the flanges.
and T, are no less severe than those which are *333. TIRE SLIPPAGE. To reduce the possibility applicable to the lesser ply rating tire. of tire and tube failure due to slippage, and to
2. The ratio of the test loads, I, to In provide a means of detecting tire slippage, tires is not less than that applicable to the lesser ply should be marked and indexed with the wheel rating tire. Make any necessary adjustment in rim. Marking should be accomplished by paintthis ratio by increasing In. ing a mark 1 inch in width and 2 inches in length
(10) Optional Dynamometer Equipment. Dynamic tests may be conducted on any dynanometer test equipment which will provide the load, speed, time, and roll distance parameters of the tire.
c. Tubes. Punctured tubes may be repaired by the use of cemented or vulcanized patches.
(1) The procedure for making such repairs is substantially identical to that used in connection with repair of automobile tires:
(a) Keep the size of the patch to a minimum and avoid use of an excessive number of patches, particularly in one area, as the weight of the material may contribute to excessive wheel vibration due to the tube being out-of-balance.
(b) The use of vulcanized patches is recommended because they are considered more re liable.
(c) Reinstalled tires should be inflated, deacross the tire sidewall and wheel ri. The paint used should be of a permanent type and contrasting color, such as white, red, or orange.
Preflight inspection should include a check of slippage marks for alignment. If the slippage mark is not in alignment, the aircraft should not be operated until a detailed inspection is made, the reason deterined, and if necessary the condition corrected.
334. TIRE MAINTENANCE. A progiam of tire maintenance can minimize tire failures and increase tire service life. Overinflation wears the center of the tread excessively, and reduces a tire's resistance to bruising, strains the fires beads, reduces traction and skid resistance. Underinflation increases deflection and may cause breakdown of the tire sidewalls. The manufacturer's recommendations should be followed to obtain maximum tire service life.
flated, and again inflated to insure that the inner- 345.-349. RESERVED. * Por 332 Chap 8
AC 43.13-1A Page 151 1972 Section 2. LIFE PRESERVERS AND LIFERAFTS
344. GENERAL. Inflatable life preservers and liferafts are subject to general deterioration due to aging. Experience has indicated that such equipment may be in need of replacement at the end of 5 years due to porosity of the rubber-coated material. Wear of such equipment is accelerated when stowed on board aircraft because of vibration which causes chaffing of the rubberized fabric. This ultimately results in localized leakage. Leakage is also likely to occur where the fabric is folded because sharp corners are formed. When these corners are in contact with the carrying cases, or with adjacent parts of the rubberized fabric, they tend to wear through due to vibration.
345. INSPECTION PROCEDURE FOR LIFE PRE- SERVERS. Life preservers should be inspected at 8-month intervals for cuts, tears, or other damage to the rubberized material. Check the mouth valves and tubing for leakage, corrosion, and deterioration. Remove the carbon dioxide cylinder and check the discharge mechanism by operating the lever to ascertain that the pin operates freely. Check the gaskets and valve cores of the cylinder container and the pull cord for deterioration. If no defects are found, inflate the preserver with air to a 2- pound pressure and allow to stand for 12 hours. If the preserver still has adequate rigidity at the end of that time, deflate and fit with CO, cylinders having weights not less than that indicated on them by the manufacturer.
All cylinders made in accordance with joint Army/Navy Specification MIL-C-00601D are so stamped and have a minimum permissible weight stamped on them. The use of such CO, cylinders is recommended. These cylinders have the 5/82-inch end disc sealed by an electric welding process, which is intended to provide a superior seal compared to the older type, which have a similar disc surrounded by a thin rubber seal. Inasmuch as the rubber is subject to deterioration, its ability to maintain pressure will possibly be affected. Leaky electrically welded seals will probably be discovered upon final inspection at the manufacturer's plant. If such a cylinder is up to weight at the end of 3 months in all probability it will remain so until used; whereas, the old type with the rubber seal is apt to lose its pressure with age. Having fitted the preserver with an adequately charged cylinder, mark the preserver to indicate the date of inspection and pack into its container, It is recommended that the aforementioned procedure be repeated every 12- month period, utilizing the CO, cartridge for inflation. Carbon dioxide permeates the rubberized fabric at a faster rate than air and will indicate if the porosity of the material is exces-
346. REPAIR OF LIFE PRESERVERS. Leaks may be disclosed by immersion in soapy water. Repair leaks by the use of patches in accordance with the recommendations of the manufacturer.
Clean corroded metal parts and replace missing or weakened lanyards. Life preserves which do not retain sufficient rigidity after the 12-hour period, because of general deterioration and porosity of the fabric, are beyond economical repair and should be replaced.
347. INSPECTION PROCEDURE FOR LIFERAFTS.
Liferafts should be inspected at 8-month intervals for cuts, tears, or other damage to the rubberized material. If the raft is found to be in good condition, remove the CO, bottle(s) and inflate the raft with air to a pressure of 2 pounds. The air should be introduced at the fitting normally connected to the CO, bottle(s).
After at least 1 hour to allow for the air within the raft to adjust itself to the ambient temperature, check pressure and adjust, if necessary, to 2 pounds and allow the raft to stand for 24 hours. If, after 24 hours, the pressure is Chap 8 Par 344
Pago 152 less than 1 pound, examine the raft for leakage by using soapy water. In order to eliminate pressure variations due to temperature differences at the time the initial and final reading are taken, test the raft in a room where the temperature is fairly constant. If the pressure drop is satisfactory, the raft should be considered as being in an airworthy condition and returned to service after being fitted with correctly charged CO, bottles as determined by weighing them. Rafts more than 5 years old are likely to be unairworthy due to deterioration. It is suggested that the rafts be marked to indicate the date of inspection and that soapstone be used when folding them preparatory to insertion into the carrying case. Take care to see that all of the raft's required equipment is on board and properly stowed. If the raft lanyard, used to prevent the raft from floating away from the airplane, is in need of replacement, use a lanyard not less than 20 feet long and having a breaking strength of about 75 pounds. It is recommended that the aforementioned procedure be repeated every 18-month period utilizing the CO, bottle(s) for inflation. If a single bottle is used for inflating Par 347 AC 43.13-1A 1972 both compartments, it should be noted whether the inflation is proceeding equally to both compartments. Occasionally the formation of carbon-dioxide snow" may occur in one passage of the distribution manifold and divert a larger volume of gas to one compartment, which may burst if the mattress valve is not open to relieve the pressure. If the pressure is satisfactory, return the raft to service in accordance with the procedure outlined.
348. REPAIR OF LIFERAFTS. When leaks due to tears, abrasion, or punctures are found, make repairs in accordance with the recommendations of the manufacturer. Recement partially torn away supporting patches on the tube to restore the raft to its airworthy condition. Replace mildewed or weak lanyards, particularly those by which the CO, bottle is operated. This applies also to the line used to attach the raft to the airplane. Check all metal parts for corrosion, and clean or repair if found to be defective. If leaky mattress valves have been found, they must be replaced.
349.-359. RESERVED.
Chap 8
AC 43.13-1A Page 153 1972 Section 3. MISCELLANEOUS EQUIPMENT
360. PARACHUTES. With reasonable care, parachutes normally last at least 5 years. They should not be carelessly tossed about, left in airplanes so that they may become wet, or left in open places where they may be tampered with. They should not be placed where they may fall on oily floors or be subject to acid fumes from adjacent battery chargers. When repacking is scheduled, a careful inspection of the parachute should 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 Part 65 of the Federal Aviation Regulations, or by an appropriately rated parachute loft certificated in accordance with Part 149 of the FAR.
361. SAFETY BELTS, The Civil Air Regulations require that when safety belts are to be replaced in aircraft manufactured after July 1, 1951, such belts must conform to standards established by the Federal Aviation Administration. These standards are contained in Technical Standard Order TSO-C22. Safety belts eligible for installation in aircraft may be identified by the marking TSO-C22 on the belt or by a military designation number since military belts comply with the strength requirements of the TSO. Airworthy type-certificated safety belta currently in aircraft may be removed for cleaning and reinstalled. However, when a type-certificated safety belt is found unairworthy, replacement with a TSO-C22 or a new milltary belt is preferred.
a. The webbing of safety belts, even when mildew-proofed, is subject to deterioration due to constant use, cleaning, and the effects of aging. The clamping action of the serrations of the commonly used buckle also causes a reduction in strength of the webbing and fraying occurs after long periods of usage. Praying 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. Difference of opinion as to the airworthiness of a belt can be settled by testing a questlonable belt to demonstrate that it will support the required load. Airworthy one-person type-certificated belts should be able to withstand a tensile load of 525 pounds, and TSO belts withstand the rated tensile load indicated on the belt label. Most one-person TSO belta are rated for 1,500 pounds, For two-person belts, double the loads. Since type-certificated belts will not afford the crash protection provided by a TSO or military belt, such type-certificated belts are not to be repaired nor should their buckles or end fittings be reused on safety belts. If replacement oi webbing or hardware of TSO or military belt is attempted, use parts of identical design and material. Make the stitch pattern identical to the original and the number of stitches per inch equal to the number used in the original belt.
There is no objection to having a greater total length of stitching, provided one line of stitches is not placed over another line. Space lines of stitching at least 8/16-inch apart. Keep a record, preferably in the logbook, stating the extent to which the belt was repaired and the date. Retain the original identification marking on the belt, conforming either to that required by TSO-C22 to a deviation from this marking, or to the military designation. Operators of a fleet of airplanes should follow the above suggestions, but keeping a record of renovations in a logbook is impractical, since the belts are never associated with any one particular aircraft for any length of time. Therefore, in addition to retaining the original identification label and attaching it to the renovated belt, use some additional simple marking to indicate Chap • Par 360
that the belt has been renovated and show the date of renovation. The use of letter "R" followed by the date would be acceptable. This marking could be in the form of an indelible ink stamping or cloth label stitched to the webbing.
362. FLARES. Parachute flares are made of materials which are subject to decomposition upon aging. Humidity affects the small igniting charge and also the materials of the candle (illuminant). Hence, the percentage of misfires in old flares is likely to be quite high. To assure inspect the fore installat on foeperiode entire system, starting at the release mechanism in the cockpit and ending at the flare. Only a qualified person should attempt such inspection, since inadvertent discharge of such pyrotechnics may cause serious damage. Past experience has indicated that it is advisable to return all electrically or pistol-operated flares to the manufacturer for reconditioning within a maximum period of 8 years, and that for mechanically operated flares, a maximum period of 4 years is recommended.
363. OXYGEN SYSTEMS.
a. General. 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.
(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.
(2) Alreraft Liquid Oxygen Systems, Thus far it has not been a practice to use liquid oxygen in Par 361 AC 43.13-1A 1972 civil aircraft due to its complexity. This however, may change at any time as technological advances are made.
(3) Portable Oxygen Systems. The three basic types of portable oxygen systems are: demand, pressure demand, and continuous flow. The component parte 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 it is essential 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.
Nore: Check portable equipment including its security provisions frequently, as it is more susceptible to personnel abuse than a permanently installed system.
b. Inspection. Handa, 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 apontaneous combustion, explosions, and/or fire.
(1) Oxygen Tanks and Cylinders. Inspect the entire exterior surface of the cylinder for indication of abuse, dents, bulges, and strap chating.
(a) Examine the neck of cylinder for cracks, distortion, or damaged threads.
(b) Check the cylinder to determine if the markings are legible.
(c) Check date of last hydrostatic test. If the periodic retest date is past, do not return the cylinder to service until the test has been accomplished.
NorE: This test period is established by the Department of Transportation in the Code of Federal Regulations, Title 48, Chapter 1, Paragraph 178.84.
(d) Inspect the cylinder mounting bracket, bracket hold-down bolts and cylinder holding straps for cracks and deformation, cleanliness, and security of attachment.
(e) In the immediate area where the cylinder is stored or secured, check for evi- Chap 8
AC 43.13-1A 1972 dence of any types of interference, chafing, deformation, or deterioration.
(2) Lines and Fittings.
(a) Inspect oxygen lines for chafing, corrosion, flat spots and irregularities, i.e., sharp bends, kinks, and inadequate security.
(b) Check fittings for corrosion around the threaded area where lines are joined together. Pressurize the system and check for leaks. (Ref. c(2) (b) 4.)
CAUTION In pressurizing the system, actuate the valve slowly to avoid surging which could rupture the line.
(3) Regulators, Valves, and Gauges.
(a) Examine all parts for cracks, nicks, damaged threads or other apparent damage.
(b) Actuate regulator controis and valve to check for ease of operation.
(c) 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.
(4) Masks and Hoses.
(a) Check the oxygen mask for fabric cracks and rough face seals. If the mask is a fullface model, inspect glass or plastic for cleanness and state of repair.
(b) When appropriate, with due regard to hygienic considerations, the sealing qualities of an oxygen mask may be tested by placing thumb over connection at end of mask tube and inhaling very lightly. Remove thumb from diaconnect after each continuous inhalation. If there is no leakage, mask will adhere tightly to face during inhalation and definite resistance to inhalation will be noticeable.
(c) Flex the mask hose gently over its entirety and check for evidence of deterioration or dirt.
(d) Examine the mask and hose storage compartment of cleanliness and general condition.
(e) If the mask and hose storage compartment is provided with a cover or release mechanism, check its operation.
c. Maintenance.
(1) Oxygen Tanks, Cylinders, and Hold Down Brackets.
Chap 8 Page 155
(a) Remove from service any cylinders that show signs of abuse, dents, bulges, cracks, distortion, damaged threads, or defects which might render the cylinder unsafe. Typical examples of oxygen cylinder damage are shown in figure 8.7.
DENT
AVIATORS BREATHING OXYGEN THREAD DAMAGE CRACKS FIGURE 8.7.--Oxygen cylinder damage.
(b) When replacing an oxygen cylinder, be certain that the replacement cylinder is of the same size and weight as the one removed.
Nore: Cylinders having greater weight or size will require strengthened cylinder mounting brackets, and a reevaluation to determine that the larger or heavier cylinder will not interfere with adjacent systems, components, or structural members, and that the strength of attaching structure is adequate.
(c) Replace or repair any cylinder mounting brackets that show sign of wear. Visible cracks may be welded in accordance with Chapter 2, Section 2 of this Advisory Circular.
Replace cylinder straps or clamps that show wear or abuse. For typical mounting bracket crack and failure, see figure 8.8.
poked racket it
(b) 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.
1. The high-pressure lines which are located between the oxygen bottle, outside oxygen service filler, and the regulator are normally fabricated from stainless steel or thickwall, seamless copper alloy tubing. The fittings on high-pressure lines are normally silver sol- Par 363
Page 156 AC 43.13-1A 1972
CHECK FOR LOOSE RIVET
CHECK HOLDING CLAMPS
FOR IRREGULARITIES
CHECK FOR CRACKS
IN COVER PLATE
CHECK FOR CRACKS FIGURE 8.8. Cylinder brackets and clamps.
NOTE: Use silver alloys free of cadmium when silver soldering. The use of silver solder which contains cadmium will emit a poisonous gas when heated to a molten state. This gas is extremely hazardous to health if inhaled.
2. The low-pressure lines extend from the pressure regulator to each passenger and crew oxygen outlet. These lines are fabricated from seamless aluminum alloy, copper, or flexible hose. Normally, flare- or flange-type connections are used. (Ref. Chapter 10, Section 1, para. 398b of this Advisory Circular.)
CAUTION Do not allow ofl, grease, fammable solvent, or other combuatibles such as lint or dust to come in contact with threads or any parts that will be exposed to pressurized oxygen.
3. 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.
4. When oxygen is being lost from a system through leakage, a sequence of steps may be necessary to locate the opening. Leakage 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.
CAUTION Do not attempt to tighten any connections while the system is charged.
(3) 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.
(4) Masks and Hoses.
(a) 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.
(b) Maintenance Practice and Cleaning.
1. Clean and disinfect mask assemblies after use, as appropriate.
NOTE: Use care to avoid damaging microphone assembly while cleaning and sterilizing.
2. Wash mask with a mild soap solution and rinse it with clear water.
Par 363 Chap 8
AC 43.13-1A 1972
3. 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.
4. Replace the hose if it shows evidence of deterioration.
5. Hoses may be cleaned in the same manner as the mask.
6. 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.
d. Functional Testing After Repair. Following repair, and before inspection plates, cover plates, or upholstering are replaced, test the entire system.
(1) Open cylinder valve slowly and observe the pressure gauge on a high-pressure system.
A pressure of approximately 1,800 p.s.i. (at 70° F.) should be indicated on the gauge. (Cylinder pressure will vary considerably with radical temperature changes.)
(a) Check 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 (if appropriate, clean mask according to Par. c(4)
(b)) to see whether there is a flow of oxygen.
(b) Check the complete system for leaks in accordance with the procedure outlined in c(2) (b) 4.
(e) If leaks are found, close the cylinder valve; open an outlet to reduce the pressure in the system to zero.
(2) A pressure drop check of the system may be made as follows:
(a) Open the cylinder valve and pressurize the system. Observe the pressure gauge (a pressure of approximately 1,800 p.s.i. at 70° F.
should be indicated). For the light weight ICC 8HT 1850 cylinders, pressurize the system to approximately 1,850 p.s.i. at 70° F.
(b) Close the cylinder valve and wait approximately 5 minutes for temperatures to stabilize.
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(c) Record the pressure gauge reading and temperature and after 1 hour, record the pressure gauge reading and temperature again.
(d) A maximum pressure drop of 100
p.s.i. is permissible.
NorE: Conduct the above tests in an area where changes of temperature will be less than 10° F. In the event that a change in temperature greater than approximately 10° F. occurs during the 1-hour period, suitable corrections would be required, or reconduct the test under conditions of unvarying temperatures.
e. 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 requirement.
These cylinders carry an ICC or DOT SAA 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 15 years or 4,380 pressurizations, whichever occurs first. These cylinders carry an ICC or DOT 8HT 1850 classification.
CAUTION Use only aviation breathing oxygen when having the oxygen bottle charged. MIL-O-27210C specifies that the moisture content of aviation breathing oxygen must not exceed 0.005 milligrams of water vapor per liter of gas at a temperature of 70° F.
and a pressure of 760 millimeters of mercury.
(1) 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. Never attempt to charge a low-pressure cylinder directly from a high-pressure manifold system or cylinder.
la) Inspection. Do not attempt to charge oxygen cylinders if any of the following discrepancies exist:
1. Contaminated fittings on the manifold, cylinder, or outside filler valve. It in doubt, wipe with stabilized trichloroethylene; however, do not permit solvent to enter any internal parts. Let air dry.
2. Cylinder out of hydrostatic test date. DOT regulations require ICC or DOT SAA designation cylinders to be hydrostatic tested to 5/8 their working pressure, every 5 years. Cylinders bearing designation ICC or Far 363
DOT 8HT must be hydrostatic tested to 5/8 their working pressure every 3 years, and retired from service 15 years or 4,380 filling cycles after date of manufacture, whichever occurs first.
3. Cylinder is completely empty. Do not charge, as the cylinder must be removed, inspected, and cleaned.
(b) Charging.
1. Connect cylinder valve outlet or out~ side filler valve to manifold.
2. Slowly open valve of cylinder to be charged and observe pressure on gauge of manifold system.
3. Slowly open valve of cylinder on manifold system having the lowest pressure and allow pressure to equalize.
4. Close cylinder valve on manifold system and slowly open valve of cylinder having next highest pressure. Continue this procedure until the cylinder has been charged in accordance with e(1) (d), Table of Filling Pressures.
(c) Top-off.
After the cylinder has been filled in accordance with the filling table (shown under e(1)
(a)) :
1. Close all valves on manifold system.
2. Close valve on filled cylinder and remove the cylinder from the manifold.
3. Using leak detector, test for leakage around cylinder valve threaded connections. (If leakage is present, discharge oxygen and return cylinder to facility for repair.)
4. Let cylinder stabilize for period of at least 1 hour, and then recheck pressure.
5. Make any necessary adjustments in pressure.
(d) Table of Filling Pressures, Initial ami Preazure Filling
• F. (D.s.1.)
1,650 10 1,700 20 1,725 80 1,775 40 1,826 Par 363 AC 43.13-1A 1972 Initial Filling (°F., remi Preasure (D.s.t.)
50 1,875 60 1,925 70 1,975 80 2,000 90 2,050 100 2,100 110 2,150 120 2,200 180 2,250 Initial Temperature--Refers to ambient temperature in filling room.
Filling Pressure-Refers to the pressure to which aircraft cylinders should be filled. This table gives approximations only, and assumes a rise in temperature of approximately 25° F.
due to heat of compression. This table also assumes the aircraft cylinders will be filled as quickly as possible and that they will only be cooled by ambient air; no water bath or other Example: If ambient temperature is 70° F.
fill aircraft cylinders to approximately 1,975
p.s.i.-as close to this pressure as the gauge may be read. Upon cooling, cylinders should have approximately 1,850 p.s.i. pressure.
12) 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 p.s.i. to a line pressure of 450 p.s.i.g. (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.
If a leak is detected, paragraph c(2) (b) 4 should be referred to for corrective action.
364.-374. RESERVED.
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