PIPER COMANCHE SERVICE MANt"AL I. Before opening any valves, check the pressure remaining in the airplane's oxygen cylinder i" st ill pa nlv cha rged. note the pressure indicated on the cylinder gauge. Then open and close each \ alve on th, ca ... cadc storage ... ~ ... tern and determine which cylinder has the lowest pressure. When found. if this cylinder has a pressure lower than the oxygen cylinder in the airplane. do not attempt using it forfilling. Lse the storage cylinder that has a pres!>urc higher than the airplane's cylinder but lower than the others. "'l Open the valve on only the one storage cylinder with the lowest pressure.
When the pre-sure indicated on the airplane's oxygen gauge and charging gauge has become equal. close the valve of the ... torage cylinder. then go In the storage cylinder with the next higher pressure and repeat the procedure. J. If. after using the last storage cylinder. the airplane's oxygen system is still not fully charged. a full storage cylinder should be put in place of a cylinder with the lowest pressure and used in the same manner. 4. A good deal of oxygen will remain in the large cylinders used in the cascade system after filling only one of the c~ linders, but such remaining oxygen will be at a pressure something less t han the 1l pound "I.
which i"l not sufficient pressure to completely refill another aircraft cylinder. although it will refill .. evcral smaller cylinder ... 5. It is not economical, even on a three or four-cylinder cascade system. to begin recharging w ith oxygen at b ... than .'\00 psi pressure in the 300 cubic foot bank of cylinders. So. use JOO cubic foot cylinder ... dow n In approximately JOO psi. then return for refilling. In two-cylinder systems. use to approximately 600 pvi, then return for filling. C'. When the pressure gauge on the recharge unit or in the airplane reaches 1800 psi. close the pressure regulator valve on the recharge unit. Disconnect the filler hose from the filler valve.
replace the protective cap on the filler valve and close the access cover. Check cylinder pressure against chart after cylinder temperature 2-59. Inspection and Overhaul Time Limits. It is recommended that inspection and overhaul be conducted b~ an FA.-\ Approved Station of the manufacturer. Scott Aviation. The following checks and chart gi. ... tabilize .... recommended inspection and overhaul time for the various parts of the oxygen system. a. ThC' oxygen c~ tinder can be identified by the ICC or DOT identification stamped on the cylinder. The standard wciuht cvlinder lice or DOT :lAA 1800) must be hvdrostatic tested at the end of each 5 vear period.
The tight\~eigh't cylinder (ICC or DOT :lHT 1850) must be tested every 3 years. The month and vear of the la ... t test is stamped on the cylinder beneath the lec or DOT identification. h. The outlets should be checked for leakage both in the non-use condition. and for leakage around an inserted connector. c. The high pressure gauge may be checked for accuracy by comparing its indicated pressure with that of a uauue of known accuracv. d. ~I nspection of the regulator may be effected by introducing into an outlet a mask connector to which is attached a 100 psi gauge. With one other outlet flowing through a plugged in mask. the indicated regulator output pn:" ... urc ...
hall he not less than 45 psig at sea level with 200 psig supply cylinder pressure. It should be noted that the permissible leakage through the I 16 diameter vent hole in the side of the upper regulator hou ... ing i ... 10 I;C min. maximum. when the regulator is turned on. There shall be no external leakage any where on the regulator when il is turned off. All fittings shall be leak free. ADDED: 4/3/78 lC14 HA:'\DLlNG A~D SER\'ICT\G