the temperature of the electrolyte must be taken into consideration

The most common heating system in light general aviation aircraft is where outside air is heated by passing it through a shroud or covering on the exhaust system before venting the heated air to the cabin. The system must be inspected for exhaust leaks. A leak could let exhaust gasses, including carbon monoxide gas, into the cockpit, incapacitating the pilot and passengers.

Pilots need to be alert to the signs of carbon monoxide poisoning. Tightness across the forehead, headache, tingling in the fingertips, fingernails possibly turning a bluish tint, a feeling of nausea, a ringing in the ears, and not being able to concentrate are all signs of carbon monoxide poisoning.

Because of the risk of carbon monoxide in a closed cockpit and the fact it is not readily detectable, pilots, if they so desire, can purchase and use one of the carbon monoxide detectors sold at most fixed base operators.

Exercise extreme care when making the hydrometer test of a lead-acid cell. Handle the electrolyte carefully because sulfuric acid will burn clothing and skin. If the acid does contact the skin, wash the area thoroughly with water and then apply bicarbonate of soda.

Each cell containing the plates are filled with an electrolyte composed of sulphuric acid and distilled water with a specific gravity of 1.270 at 60 °F. This solution contains positive hydrogen ions and negative sulfate (SO4) ions that are free to combine with other ions and form a new chemical compound.

When the cell is discharged, electrons leave the negative plate and flow to the positive plates where they cause the lead dioxide (PbO2) to break down into negative oxygen ions and positive lead ions.

The negative oxygen ions join with positive hydrogen ions from the sulfuric acid and form water (H2O). The negative sulfate ions join with the lead ions in both plates and form lead sulfate (PbSO4). After the discharge, the specific gravity changes to about 1.150.

All metals and alloys are electrically active and have a specific electrical potential in a given chemical environment. The constituents in an alloy also have specific electrical potentials which are generally different from each other. Exposure of the alloy surface to a conductive, corrosive medium causes the more active metal to become anodic and the less active metal to become cathodic, thereby establishing conditions for corrosion.

These are called local cells. The greater the different in electrical potential between the two metals, the greater will be the severity of a corrosive attack, if the proper conditions are allowed to develop.

There is a fire risk in taking a cold aircraft with full fuel tanks into a warmer hangar. As the cold fuel in the tanks becomes warmer, it will expand and possibly overflow onto the hangar floor causing a potential fire hazard.

Care should be taken when servicing a cold aircraft in a hangar because if the increased fire risk. Plus, any fuel will flow over the wing possibly removing any wax or other surface protection you may applied for the winter.

When a battery is tested using a hydrometer, the temperature of the electrolyte must be taken into consideration. The specific gravity readings on the hydrometer will vary from the actual specific gravity as the temperature changes. No correction is necessary when the temperature is between 70 °F and 90 °F, since the variation is not great enough to consider.

When temperatures are greater than 90 °F or less than 70 °F, it is necessary to apply a correction factor. Some hydrometers are equipped with a correction scale inside the tube. With other hydrometers, it is necessary to refer to a chart provided by the manufacturer. In both cases, the corrections should be added to, or subtracted from the reading shown on the hydrometer.

To facilitate installation and removal of the battery in some aircraft, a quick disconnect assembly is used to connect the power leads to the battery. This assembly attaches the battery leads in the aircraft to a receptacle mounted on the side of the battery. [Figure 10-185] The receptacle covers the battery terminal posts and prevents accidental shorting during the installation and removal of the battery.

A storage battery may be charged by passing direct current through the battery in a direction opposite to that of the discharge current. Because of the internal resistance (IR) in the battery, the voltage of the external charging source must be greater than the open circuit voltage. For example, the open circuit voltage of a fully charged 12 cell, lead-acid battery is approximately 26.4 volts (12 x 2.2 volts), but approximately 28 volts are required to charge it.

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