These instructions are general in nature and do not represent  any aircraft procedure. Always check the correct manual  before servicing any propeller system. Examine the propeller  to make sure that it is positioned on the start locks and using  the proper control, then charge the cylinder with dry air or  nitrogen. The air charge valve is located on the cylinder as  indicated in  Figure 7-41 . Nitrogen is the preferred charging  medium. The correct charge pressure is identified by  checking the correct table shown. The temperature is used  to find the correct pressure to charge the hub air pressure. One example of the lubrication requirements and procedures  is detailed here for illustration purposes only. Lubrication  intervals are important to adhere to because of corrosion  implications. The propeller must be lubricated at intervals  not to exceed 100 hours or at 12 calendar months, whichever  occurs first. If annual operation is significantly less than  100 hours, calendar lubrication intervals should be reduced  to 6 months. If the aircraft is operated or stored under  adverse atmospheric conditions, such as high humidity, salt  air, calendar lubrication intervals should be reduced to 6  months. Hartzell recommends that new or newly overhauled  propellers be lubricated after the first 1 or 2 hours of operation  because centrifugal loads pack and redistribute grease,  which may result in a propeller imbalance. Redistribution  of grease may also result in voids in the blade bearing area  where moisture can collect. Remove the lubrication fitting  from the cylinder-side hub half installed in the engine-side  hub half.  [Figure 7-42]  Pump 1 fluid ounce (30 milliliters  (ml)) grease into the fitting located nearest the leading edge  of the blade on a tractor installation, or nearest the trailing  edge on a pusher installation, until grease emerges from the  hole where the fitting was removed, whichever occurs first. Hydromatic propellers operated with engine oil and some  sealed propellers do not require lubrication. Electric propellers  require oils and greases for hub lubricants and pitch change  drive mechanisms. Proper propeller lubrication procedures,  with oil and grease specifications, are usually published in the  manufacturer’s instructions. Experience indicates that water  sometimes gets into the propeller blade bearing assembly  on some models of propellers. For this reason, the propeller  manufacturer’s greasing schedule must be followed to ensure  proper lubrication of moving parts and protection from  corrosion. Observe overhaul periods because most defects  in propellers are not external, but unseen internal corrosion.  Dissimilar metals in the prop and hub create an environment  ripe for corrosion, and the only way to properly inspect many  of these areas is through a teardown. Extensive corrosion can  dramatically reduce the strength of the blades or hub. Even  seemingly minor corrosion may cause a blade or hub to fail  an inspection. Because of the safety implications (blade loss),  this is clearly an area in which close monitoring is needed. NOTE: 1 fluid ounce (30 ml) is approximately six pumps with  a hand-operated grease gun. Reinstall the removed lubrication  fittings. Tighten the fittings until snug. Make sure that the  ball of each lubrication fitting is properly seated. Reinstall  a lubrication fitting cap on each lubrication fitting. Perform  grease replacement through attached pressure fittings (zerks)  in accordance with the manufacturer’s instructions. Figure 7-41.  Servicing air charge in propeller.  7-28 Air charge valve Air charge temperature/ pressure chart Propeller Lubrication Charging the Propeller Air Dome