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Unfamiliar Systems
Interestingly there are at least fourteen distinct systems that are required knowledge for the pilot. Usually lost in the morass of the others because it comes into play only twice per flight is the restraint system. Have you ever considered the safety harness system consisting of seat belt and shoulder harness as a distinct system. A system requiring operational specifics related to FARs, instructional usage, limitations and emergencies. The first emergency I ever felt and declared was when a thin student let the seatbelt end hang out the door so it could flap and snap against the underside of the aircraft.

The FARs require that the pilot brief all passengers about the use of seat belts and notifies them when the belts are required and how to release them. This requirement is irrespective of the prior qualifications of the passenger. Seatbelts briefings in the FARs are required only for takeoff; notification about the seatbelts is required for takeoffs, landings and all surface movement. In a single engine aircraft only one person can preside as a required crewmember. This required crewmember must keep his seat belt and shoulder harness fastened while on his duty station. The shoulder harness is not required where it may interfere with piloting duties.

Passengers are not required to use seatbelts or shoulder harness while en route. Only in the FARs would the requirement that passengers be required to be briefed as to the use of belts and harness, without any requirement that they be worn. Dumb and dumber.

The vacuum system is one of the most reliable and limited use systems used on aircraft. Usually, it only serves to operate the attitude indicator and heading indicator. Early on it consisted only of a venturi 'horn' on the side of an aircraft to provide in motion vacuum. Now, replaced by a engine driven vacuum pump the 'horn' is usually a curiosity.

Instructional aid:
The simplest demonstration of venturi action coming from accelerated air and lower pressure can be done with two sheets of paper. Suspend each sheet from one end between the thumb and forefinger of both hands. Hold the sheets about two inches apart so that you can blow between the sheets. Blow and observe that the sheets close together. You have created a venturi and made it work as such. Put a few drops of gasoline on the back of your hand and then wave the hand about. Notice the cooling effect. With these two experiments you have most of the essentials for carburetor icing. Lacking are only the evaporative powers of the fuel and the presence of moisture. Try it.

One specific about the pump is that it will run for about 600 hours once it survives the first couple of hours. It is usually replaced upon failure and not as a precautionary measure. Most are dry but some are wet (oil) and tend to fail gradually so that it may be so subtle as to escape notice. When this occurs in IFR conditions bad things can happen like fatal accidents.

Be able to diagram the pitot-static system, which involves two separate holes in the exterior of the aircraft. The pitot tube is a measure of air pressure caused by the aircraft's relative wind. This tube goes to the airspeed indicator to create indicated airspeed. The static air hole goes to the altimeter case and the vertical speed indicator.

The aircraft environmental system is made up of two separate systems. Cabin heat comes from air that is contained in a muff welded around the engine exhaust pipes. This is a relatively simple method of benefiting from excess engine heat. However, should an internal crack develop in the exhaust pipe inside the muff, carbon monoxide will become a part of your cabin heat.

Interestingly, even without any leakage of exhaust gases it is possible for a tightly sealed cockpit to trigger your carbon monoxide detectors due to the lack of cockpit ventilation. I recently had such an event with only two people in the cockpit. It would be wise to ventilate aircraft cockpits at all times.

A part of every aircraft checkout should include the full information of the heating system and any associated dangers. Cabin vents are located in several difference places and with varied modes of operation. Some vents are best not used in rain for obvious reasons. The restrictions related to opening windows and doors is a part of this system.

I have rarely entered an unfamiliar aircraft that I have not experienced some peculiarity of avionics system be it switch, knob or other operation. Recently sat next to a Cutlass where the pilot spent at least ten minutes trying to figure out the radios before shutting down. The presence or absence of a radio master makes a difference in operational procedures. Radio switches are the most vulnerable to defective operation. The first item to suspect when you have a problem is yourself.  Check your headset cables, then any frequency setting, then the audio panel settings and then the volume. Test your settings with the ATIS. The failure of the avionics is not life threatening even in IFR Use a standby handheld or just proceed to nearest airport using NORDO procedures.

The electrical system consists of multiple sub-systems in which each has a number of switches. The starting system consists of the battery, a master switch, a starter solenoid, the starter with attached Bendix spring and the key switch with start, both, left and right selections. The lighting system consists of interior, exterior, landing, navigational, strobes, indicator, and warning lights. All of these sub-systems have their own switches, operational criteria and useful significance. The pilot is expected to know the use, operation, significance and applicable FARs for every light.

The electrical system is usually involved with varied capability in the aircraft trim, flaps, anti-ice, environmental operation. Each sub-system is fused or with circuit breakers. The pilot must know the process required to maintain electrical operations and how to replace fuses and reset breakers. Just as important is the pilot's willingness to leave an existing situation for more qualified personnel.

The landing gear system involves the gear box attachment as well as the shock system, wheels, bearings, brakes and tires. The pilot must be sensitive to the operational limits of the gear. Side loads are damaging. Heaving braking ruins tires and wears out brakes. Wheels can be broken by hard landings. Improper inflation is the most common reason for an aircraft being operated in an 'unairworthy' condition. A pilot is expected to know about the gear and its peculiarities.

While the brakes are part of the landing gear, the operation of the brake is an independent hydraulic system similar to that used in automobiles but with smaller and lighter components. A pilot is expected to know how the hydraulic fluid is different from other fluids in the aircraft. Being able to check brake operation and fluid levels is, or can be, part of the preflight. Brakes are a relatively frequent responsible component of aircraft accidents. Aircraft braking is best done in light smooth applications rather than pumping. Heavy braking will over heat the pads and reduce effectiveness. Turning while braking will put damaging side loads on the wheels and gear boxes.

The fuel system consists of the tank(s), tank caps, plumbing, selector and cut-off valves, quantity indicators, pressure system and distribution method to the cylinders. Fuel octane is a prime operational requirement determined by the engine manufacturer. The pilot is expected to be able to compute and predict fuel consumption for the aircraft in terms of weight, capacity, quantity, and time. The fuel is metered through a mixture control in conjunction with a throttle. The throttle functions by changing engine power much as in an automobile but the effects on the aircraft performance are often contradictory. The mixture us a fuel weight adjustment based upon the weight of air available to the engine through the carburetor. Efficient aircraft operation depends upon the pilot's knowledge of and use of the fuel system. Excess fuel can be used as a coolant.

Oil is used as part of the engine lubrication and cooling requirements. The pilot must make sure to use the correct weight and type of oil to best protect the engine. Only special oil systems work inverted. Oil quantities are registered on the dipstick, which must never be overly tight. Expansion of the oil filler tube can cause the cap to stick so tightly that the tube will unscrew instead of the cap. Only finger tight is best.

The aircraft propulsion system includes the engine, its auxiliary components and the propeller. The type of engine and its definition in terms of letters and numbers used by the manufacturer are required pilot knowledge. The propeller is a special system on its own with its own maintenance ADs independent of the engine and aircraft. The care and feeding of the engine and its accessories is required knowledge of the pilot. Knowing the length, pitch, and any special characteristics of the propeller range in importance from the nice to know to the need to know.

The flight control system consists of two levels. Primary will be rudder, ailerons and elevators. Secondary will be flaps and trim. The pilot is expected to know how each of these affects flight independently and in conjunction with the other controls. Some aircraft have specific modifications that are on the wings or other surfaces. If your aircraft has any modifications, you are expected to know what they are for and how they accomplish their intended purpose.

Differential Pressure Check
The purpose of the differential pressure check of a cylinder is to determine its relative health. As in medicine, the test alone proves little, it is the interpretation that determines if a problem exists. The engine is brought up to operating temperature before the test begins. The complete picture requires analysis of the oil filter, oil consumption rates, and oil analysis.

The process begins with removal of the top sparkplug. The piston is brought to top-dead-center by turning the propeller (magnetos are off). The regulator is positioned into the sparkplug hole and compressed air is allowed to enter until it reads 80 pounds. The propeller is held to prevent any movement.

The mechanic is waiting to see how much of the initial air pressure can be retained in the combustion chamber. If the pressure stops dropping at 70 the figure 70/80 is usually written on the cylinder. If the pressure drops to 60 concerns arise. Where the air escapes tells if the problem is rings, valves or cylinder wear. This compression check will unveil a cracked cylinder or head. False problems can be caused by ring alignment or contamination.

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