When hydraulic oil changes temperature, the volume of the oil also changes. This volume change from a temperature reduction will create a vacuum in the oil chamber of the original Cessna uncompensated shimmy dampener. This vacuum will cause the oil to vaporize giving the oil a foamy expanded mixture that is compressible. The shimmy  dampener action is then drastically degraded. An increase in temperature will increase the oil volume causing a drastic pressurization of the dampener oil chamber. This pressure will force small quantities of oil past the dampener shaft seals. The decrease in oil will then aggravate any temperature reduction with increased chamber vacuum and related oil vaporization. This process explains why continuous servicing of the original shimmy dampener is required.

The temperature compensation system works by having a small chamber of oil that is spring pressurized through a very small passage into the main dampening restrictive orifice of the shimmy dampener. The spring loaded oil chamber can adjust for oil volume changes as temperature changes. A similar system is built into your car shock absorbers. The temperature compensated hydraulic system requires very little service over extended periods of time and assures stable shimmy dampening action.

It is certified to meet AMS3320G, which is the same industry standard specification to which other fiberglass reinforced silicone baffle seal material is certified, however it is not an STC or FAA-PMA product. It is ultimately the installing mechanics responsibility to determine whether the material is appropriate to repair the baffle seals on a specific aircraft.

McFarlane does have FAA approved die cut baffle seal kits for the re-start Cessna 172 aircraft; please see P/N BSC-KT-1. We developed this first because our patented material solves the firewall crack and other baffle seal related problems on these airplanes. McFarlane will develop more FAA approved baffle seal kits as engineering time permits.

The Kickback Protection System or KPS® for the NL and NL/EC family of starters is through a field-replaceable shear pin. When energizing the starter, if the pinion engages the flywheel and the starter motor spins (or at least sounds like it is spinning), but the starter’s pinion gear does not rotate you should replace the shear pin.

Fluctuating fuel pressure can be the result of the following:

1. A worn fuel pressure gauge
2. A worn or broken O-ring on the inlet side fuel fitting
3. An obstruction in the induction system (air intake)
4. A clogged or dirty fuel strainer
5. Foreign material inside the fuel body (such as fuel cell sealant, thread sealant, or a drill shaving)

1. Check your hoses to make certain that they are not collapsed or kinked.
2. Replace the system filter(s). A dirty or clogged filter will cause the pump to work significantly harder than normal and could cause premature failure.
3. Make sure that you have the correct pump installed on your aircraft.
4. Make sure that no oil contamination is entering the pump.

In some cases, engine kickback will fracture starter drive gears. Kickback is related to engine set up and can be anything from incorrect timing to problems with the fuel system. If kickback is noticed as a common occurrence on the airplane, diagnose and repair the problem or the replaced starter drive may fracture again. Many of Sky-tec's current starters offer kickback protection.

The most common indication of external fuel valve leaks is the smell of avgas in the cabin. Most valves are located under the cabin floor. Fuel stain on the valve and drain plug or drain valve or on the belly of the aircraft can also indicate external leakage. External leaks are generally around the actuation valve stem. Internal leaks are detected when the fuel is turned off and fuel continues to drip during fuel system maintenance. Inner port leakage will allow fuel from one tank to leak into another fuel tank. This type leak is difficult to detect. Fuel transfer from one tank to another with the fuel valve selected to one tank only will indicate inner-port leakage. An extended period of time is needed to detect fuel transfer from one tank to another. Generally if internal leakage is detected when servicing the fuel system, it is likely there is also inner-port leakage. 

Pressurized aircraft magnetos are usually found in turbocharged engines. Air is diverted from the turbocharging system and sent through a line to a fitting installed in the aircraft magneto. The aircraft magneto is also fitted with an opening at the bottom of the housing to allow a small air leak. This opening insures a constant flow of air through the aircraft magneto to avoid the internal air from becoming ionized.

The trim wheels on the Cessna 180, early 182 and 185 aircraft have a spring loaded trim wheel stop catch assembly that engages with a molded in ratchet on one side of the trim wheel. This system is designed to prevent unwanted trim wheel movement caused by air pressure on the horizontal stabilizer. If these stop catch assemblies are worn out, the trim wheel is free to rotate. McFarlane has replacement stop catch assemblies.

All batteries have a life span, even if left in the box and never used. Time is a factor even if properly cared for, eventually, all batteries die. An EarthX battery is rated for up to 6 years if properly maintained, which means it is not left in a discharged state (below 13.28V); used in a properly functioning charging system; used with a proper charger; not shorted; and proper temperature ratings have been followed. All batteries will self discharge and depending on the amp hour of the battery, and its temperature it is stored in, the level of discharge and amount of time are variable. Always keep your lithium battery above 13.28V for longest life.

We understand the fear of a fire in an aircraft is real and justified. We also understand people fear that a lithium battery will spontaneously self-combust with no warning and reason and catch everything near it on fire too.  We want to address this fear. The EarthX batteries are LFP chemistry, or lithium iron phosphate, the most abuse tolerant and requires a lot of energy to force them into thermal runaway. The term thermal runaway can mean different things and for a LFP battery, it does not mean a 3-foot-tall explosion of flames, it means it will produce a lot of smoke for about 10 minutes.  (It should be noted the type of chemistry that does cause a large fire ball is the most used cell in the world, a Lithium Cobalt cell. This is found in your cell phone, your tablet, your laptop, etc.  On a commercial flight, if you are traveling on a 737 with 204 person capacity, it would be typical to have around 300 of these batteries in the cabin with you as a reference point).

To cause a thermal runaway with the EarthX battery, many things in your aircraft, and you as a pilot, would have failed. First, your regulator would have to fail. Then your over voltage protection on your aircraft would have to fail. Then you as a pilot would have to fail and not turn your charging system off (alternator off) as you see the voltage and amps climb, destroying all your electronics on your panel and popping fuses everywhere in the process. If you did nothing but continued to fly, and if the batteries protection failed too or you exceeded the protection limits (over 100V), it takes about 7 minutes of this type of runaway energy to cause a thermal runaway with the battery. The FAA TSO certified approved battery, the ETX900-TSO,and the ETX900-VNT, are in a fireproof containment system (internally) and is a sealed battery that is vented overboard, so even in this catastrophic state, the smoke is pushed overboard and it is not a battery safety issue and it does not cause anything near it to heat or catch on fire either.  

As far as the fear of spontaneous self-combustion, the battery must be part of a catalyst situation for it to go into thermal runaway. It will not simply “combust” with no reactor.  The batteries have short circuit protection and a battery management system to prevent the use of the battery if it detects a fault. The Hundred series for aircraft also has a fault monitoring that would alert you if something was outside of normal with an LED light that will illuminate.  

There are many components all connected to keep the nose gear in line. If one component is worn or out of tolerance it can cause shimmy problem. Reference Dave McFarlane’s article: Can You Stop Nose Gear Shimmy instructions and suggestions.

Overlooked items also include the rod ends, shimmy dampener mounting and attachment, shimmy dampener, and steering collar. The steering collar is where the steering rod tubes connect and the upper torque link is attached to, along with the shimmy dampener on most aircraft. If the steering collar has play vertically and laterally and is allowed to tilt; that will cause excessive wear and force on the torque links, steering, and strut components. There are three different thicknesses of shims to help get the collar in place.

Ensure that the shimmy dampener is working properly with no dead spots in dampening action. The cylinder could be worn on the inside or on a piston that warrants replacement of components. All of the nose strut components are tied to each other and any movement is transmitted through to the tire and back through the dampening system, which if remedied will continue to be more pronounced.

All AeroShell oils are compatible and can be mixed with each other. Many single grade customers try AeroShell Oil W 15W-50 during the colder part of the year, then convert to using it year round. Others, however, choose to alternate between single grade and multigrade depending on the time of year. Either system works well because AeroShell oils are entirely compatible and can be interchanged as desired. 

In addition, if you need to replace a cylinder on a mid-time engine, you can switch from AeroShell Oil W single grade or AeroShell Oil W 15W-50 to a straight AeroShell mineral oil for one or two changes to break in the new cylinder. Then you can switch back to the ashless dispersant oil after the rings are properly seated. 

If you have a mid-time engine that has been run exclusively on a straight mineral oil and wish to try an ashless dispersant oil, use caution. The introduction of an ashless dispersant oil into your engine could loosen up some of the carbon deposits. So check your oil screens and filters often to ensure against oil starvation and/or oil screen collapse.

A good rule of thumb for changing piston engine oil is to change it every four months. Of course for every rule, there are at least two exceptions.

Exception #1: If you're able to fly frequently with proper oil temperature, you should adjust the four-month rule accordingly.  Change out your oil after 50 hours if you've flown the hours in less than four months.  If your engine doesn’t have an oil filter, change it after 25 hours. Always remember: the four-month rule is the most critical.

Exception #2: In recent years, the annual flight hours of many private planes have decreased.

And where there’s an idle plane, there’s rust.  When an airplane engine sits too long (especially in humid climates or if there is excess moisture in the oil because the oil temperature is too low), rust will form on many of the parts such as cams, lifters and cylinders. Then, once the plane has been started, the iron oxide will run through the entire engine oil system. 

While some of the larger pieces will filter out, many of the smaller pieces will remain in the oil and can act as grit on critical wear surfaces. If you don't plan on flying your aircraft for four months or more, be sure to use a storage or preservative oil to protect your engine.

The Cessna steering system is an engineering masterpiece that is simple in function while allowing good directional control throughout the transition from flight to ground or ground to flight, even in crosswind conditions. A key part of this system is the steering rods. The steering rods are a spring loaded device that applies spring pressure to pull on one side of the nose gear when it is activated and yet have a specified amount of free play in the opposite direction until a solid push is required for positive steering.

The following are some common symptoms of worn out or failed steering rods:

1. Weak steering (You can push on the rudder but not much happens and you have to use a lot of brake to steer. Often the weakness is one direction only.) The early Cessna steering rod springs were designed such that if the rudder pedal was pushed hard in one direction while the nose gear was pointed all the way the other direction and had some resistance to moving such as soft ground or snow, the spring could be compressed to an extent that it would be permanently shortened leaving it weak. McFarlane has redesigned the spring so this cannot happen.
2. More or less than 1.2 inches of free play movement or inconsistent free play of the steering rod shaft is present. The spring is retained by a washer that was stop swaged into the steering rod housing. During an overload, such as extra hard pedal force applied with the nose wheel pointed all the way in the opposite direction and restricted or undetected damage from a previous hard landing, the spring retaining washer can be deformed and forced past the swaged stop. This will result in inconsistent free play and erratic function of the steering rod shaft as the washer passes past its designed swaged stop in both directions. The rudder rigging in flight might also be inconsistent. This is a dangerous situation that results in inconsistent steering and the steering rod must be replaced. McFarlane has redesigned the washer and shaft machining to prevent the washer stop failure.
3. Rust and corrosion can make the steering rods unreliable. The steering rods get water and contaminates from the runway that the nose tire throws at them. The fit of the shaft into the bushing that is swaged into the housing is not a precision fit. This can allow internal contamination, moisture, and salt that will rust the springs and steel housing interior, leaving the components weak and subject to failure. Red rust streaking on the shaft exit area or bubbling of the exterior paint indicate corrosion failure. The McFarlane steering rods are made from 304 stainless steel and have a special corrosion preventative and lubricating coating on the springs to fight against corrosion and wear.
4. Wear of the shaft and bushing is caused by steering movement and aerodynamic pulse vibrations created by the rotating propeller. This wear can be detected as looseness of the shaft in the end bushing. Some wear is acceptable.

Curtis Superior and SAF-AIR valves are designed for installation in a standard NPT port for NPT threaded valves or an AND-10050 style port for UNF threaded valves. Use a thread sealant or Teflon tape on pipe threaded valves. Never allow any thread sealant on the first thread . This will prevent contamination of the fuel system. Refer to aircraft manufacturer's torque specifications for the aircraft in which it is being used.

Replace the rubber seals as per the aircraft manufacturer’s recommendations or every ten years when no guidance is given. McFarlane stocks replacement seals and seal kits for both Curtis Superior and SAF-AIR valves. The new Curtis valves use a O-ring type seal instead of the flat seal that was previously used. 

SAF-AIR valves are designed to be disassembled and the O-rings replaced. Over time, if the valve should start to leak, check to make sure the drain valve is tight. If drain valve is found to be tight, then check the O-rings. All O-rings used are buna "n", MS29513 Style, MIL-P-5315. SAF-AIR O-ring seal kits are available for most of their valves. Add a "K" or "-K" suffix to the valve part number.

Never have a hose attached in flight to the oil drain valve. Engine vibration and the additional attached mass can cause premature seal and valve wear which could result in valve failure and a loss of engine oil.

Since inception in 2009, EarthX has designed their lithium batteries with a micro-processor-controlled battery management system (BMS) to provide safety and performance features for your battery.  EarthX is not new to providing lithium iron phosphate batteries. Over the past 13 years, has become the most trusted and used lithium battery in the experimental aircraft market and by working closely with OEM’s and engine manufacturers a like, this BMS has been developed to be one of the most reliable in the industry. EarthX is not only the exclusive provider for the Indy Race Cars, but EarthX is also the first company in the world and in history to have an FAA TSO certified aircraft battery as a testament to the safety and quality of the batteries.  

Features of the BMS protection:

• Cell balancing
• Low voltage protection
• High voltage protection
• Excessive Cranking Protection (Heat)
• Short circuit protection
• In the Hundred series, an alert LED fault light to communicate an issue on battery itself or can be remotely monitored with a 12V LED
• In the Hundred series, the BMS board is redundant so there is no single point failure

Battery design safety features:

• Proprietary battery case design with recessed terminals to protect from short circuiting
• Clam shell design with terminals down the center so polarity (installation) is never an issue
• Flame retardant plastic housing
• The state of the art ceramic cell separators to reduce the risk of thermal runaway by 400% over standard lithium cell separators.

Performance design features:

• The widest operating temperature range available
• A rated cells that must meet stringent testing requirements
• True industry standards testing specifications

Preheating your engine makes a world of difference. This procedure heats the oil so it’s thin enough to flow through the engine and properly lubricate all critical wear surfaces.  Preheating also heats the metal parts in the engine. That’s important because aluminum crankcases have a higher coefficient of thermal expansion than iron crankshafts. 

This means as your engine cools down, the clearance is reduced.  And as a result, you may not have sufficient oil film thickness for proper hydrodynamic lubrication at very cold temperatures. In other words, the wear rate is going up. 

One final note of caution on heaters: Do not plug in a heater and leave it on for extended periods of time. If you have moisture in your oil, the heater will increase vaporization, which will condense on the cool, nonheated engine parts and increase rusting.

Airplane air/oil separators are also worthy of discussion. Separators are designed to remove the oil from the blow-by gas and return it to the crankcase. This reduces oil consumption and keeps the belly of the airplane clean. Properly installed, separators work well. 

However, if the system is installed with parts in a cool area under the engine cowling, it can condense all of the water evaporated from the oil and return it to the crankcase. 

If you have a separator, make sure it’s properly installed with the exit tube in a low pressure area which will evacuate the water vapor and not force it back into the crankcase. While preheating and the proper air/oil separator are essential to long engine life, they are no more essential than the oil you use. AeroShell® Oil W 15W-50 offers unsurpassed anticorrosion and antiwear protection for all kinds.

Oil analyses can help you discover engine problems before they turn into major failures. But the analysis information gained is only as good as the sampling procedure. Also, a single test is not enough to reveal trends and significant changes and can only tell you if there is already a serious problem like a scuffed piston. Take oil samples properly. For best results, take the sample about midway through the draining of hot oil from your sump. 

A sample pulled off at the beginning or end of the oil change may appear dirtier than it really is. Sample the oil the same way every time. An improperly taken sample can lead to some seriously inaccurate conclusions about engine malfunctions. Rely on a series of consistent tests over time. You’re looking for significant changes or trends over time, not absolute values.

People want to label the results of a single test as good or bad, but the system doesn’t usually work that way. Say you’re buying a used aircraft. Don’t rely on just one very good result of just one report – it could have come from a 5- or 10-hour sample. Relatively constant numbers from the last six oil changes are a far better indicator that the engine is in good condition. Your record of regular oil changes and analyses is also helpful when selling an aircraft. 

Be consistent. If you change your oil at 50 hours, and then at 25 hours the next time, the first sample may show twice the wear metals. (Expect higher wear metals during break-in or following some maintenance procedures such as a cylinder replacement.) Finally, always remember that oil analysis should be part of a good maintenance programme, not a replacement for one.