35 Oxygen

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TTP

B1-L3

ATA 35

Beech 90 Series

B2-L2

Oxygen

35 OXYGEN 
-00 General 
-10 Crew 
-20 Passenger 
-30 Portable

Beech 90 Series is normally pressurized, the passengers and crew do not need supplemental oxygen. A high-pressure gaseous oxygen system is provided as a back up system in case of cabin depressurization or unpressurized flight.
 The aircraft is equipped with a single pressurized cylinder to provide oxygen to the crew and passengers. 
Oxygen is supplied to both the crew and the passengers through a single manifold system.
The crew masks are a diluter-demand type while the passenger masks are the constant-flow style.

The oxygen cylinder and regulator behind the aft pressure bulkhead provide oxygen for the crew and passengers. The cylinder is serviced through a fill valve in the oxygen service panel on the right side of the aft fuselage.The cylinder valve has fittings for high-pressure and low-pressure lines for oxygen service and delivery. The high-pressure lines include the cylinder recharge line, the pressure gauge line, and the over pressure relief dump.

       Two pressure gauges are in the aircraft, one in the copilot outboard subpanel for in-flight use and one in the oxygen service panel for checking oxygen pressure during the filling procedure.
       The cylinder regulator is a constant-flow type that supplies low-pressure oxygen at 70 ± 10 psi through tubing to the crew and passenger oxygen outlets. The oxygen system is activated with an overhead push-pull control. This provides oxygen pressure to the cockpit outlets and the cabin outlet manifolds.
To use the oxygen, remove the oxygen masks from storage and plug the min to the outlets. The oxygen cylinder pressure gauge is on the copilot outboard sub-panel. It receives indication from a direct line that runs along the right side of the fuselage 

OXYGEN SYSTEM SERVICING

When filling the oxygen system, use only the specified oxygen (15, Chart 2,12-00-00). Do not use oxygen intended for medical or industrial purposes, such as welding. Such oxygen may contain excess moisture that could freeze in the valves and lines of the oxygen system. Avoid making sparks and keep all burning cigarettes or fire away from the vicinity of the aircraft. Make sure that the oxygen shutoff valve in the cockpit is in the closed position on LJ-1 through LJ-4 and LJ-6 through LJ-10. On LJ-5 and LJ-11 through LJ-489, make sure that the oxygen system control on the upper left subpanel is pushed fully in. On LJ-490 and subsequent, and on LW-1 and sub-sequent,  the shutoff valve and regulator are actuated by a push-pull type control overhead between the pilot and copilot seats. Inspect the filler connection for cleanliness before attaching it to the filler valve. Make sure that hands, tools, and clothing are clean, particularly of grease or oil, for these contaminants ignite upon contact with pure oxygen under pressure. As a further precaution against fire, open and close all oxygen valves slowly during filling.

The pressure indicator and filler valve are accessed through an access door on the right side of the fuselage immediately forward of FS 319.To recharge the oxygen system, remove the protective cap from the filler valve and the hose from an oxygen recharging cart to the filler valve.

 

To prevent overheating, fill the oxygen system slowly by adjusting the recharging rate with the pressure regulating valve on the cart. Fill the oxygen cylinder to a pressure of  1,800±50 psi at a temperature of 21°C (70°F). This pressure maybe increased an additional 3.5 psi for each degree of increase in temperature. Similarly, for each degree of drop in temperature, reduce the pressure of the cylinder by 3.5 psi.When the oxygen system is properly charged, disconnect the filler hose from the filler valve and replace the protective cap on the filler valve. Anytime a fitting is disconnected for any purpose, wrap the thread so the fitting with Teflon® tape before reconnecting the fitting to the system.


OXYGEN CYLINDERS


Oxygen cylinders are available in different sizes; the standard 22-cubic-foot cylinder and the optional 49,66,or 76-cubic-foot cylinders. Current production aircraft are equipped with composite cylinders, but aircraft were also equipped with standard steel (3A or 3AA rating) and light weight steel (3HT rating) cylinders. The cylinders have a regulator that provides a constant flow of 50 liters per minute (at a pressure of 70±10 psi). A vented shutoff valve attached to the regulator is actuated by the push-pull control overhead between the pilots.


PASSENGER OXYGEN MASKS


The masks provide a constant flow of 3.7 LPM at a pressure of 70 ± 10 psi at altitudes of 20,000 to 30,000 feet. A flow indicator (green for proper pressure or red for low pressure) is in the oxygen tubing to the mask. The passengers’ masks store in the seat back pockets, except in the couch, where they are under the seats. The cabin oxygen outlets are in covered cavities in the forward and aft ends of the cabin headliner. The mask tubing is plugged into a fitting in the overhead manifold by pushing the mask orifice firmly in and turning it clockwise approximately one-quarter turn. To disconnect the mask, reverse the motion.


CREW OXYGEN Diluter-Demand Masks

A quick-donning diluter-demand mask is furnished for the crew. The mask hangs on a quick-release hanger behind and outboard of the pilot head. A manual rotary valve on the oxygen mask can be positioned to NORMAL, 100%, or EMERGENCY. With NORMAL selected, the regulator mixes the supplied oxygen with cabin air. As the cabin altitude increases, less cabin air is taken in and more oxygen is supplied.With 100% selected only oxygen is supplied and the pilot breathes 100% oxygen. With EMERGENCY selected, oxygen under a mild positive pressure is supplied to the mask. Any leakage around the mask-to-face seal is oxygen leaking out and nonoxious fumes are inhaled. These masks can be donned immediately with one hand and oxygen is furnished only on inhalation. The PULL ON SYS READY control must be pulled out to provide oxygen. The mask is equipped with a microphone. The microphone cord and oxygen tube are plugged in a tall times.





PTP 

Beech 90 Series

B1

LOC

FOT

SGH

R/I


B2


FOT

SGH



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