Like everything else in aircraft maintenance, it depends. 

The truth is something can be FAA approved and still not recognized or authorized by the aircraft’s OEM. Often, owners and maintainers will use alternate means of compliance to achieve airworthiness. These solutions include, but are not limited to, a parts manufacturer’s approval (PMA), designated engineering representative (DER) repairs, and STCs.

• READ MORE: Cirrus Service Advisory Throws Fuel on G100UL Maintenance Debate

GAMI applied, and the FAA awarded STC approval for G100UL. Its unleaded gasoline is an alternative to 100LL avgas. An STC, although legal, still raises questions for some. 

What Is an STC?

The FAA issues an STC to approve a significant change or modification to an airframe, engine, or propeller operating with a current type certificate.

The FAA defines it as follows: “A supplemental type certificate (STC) is a type certificate (TC) issued when an applicant has received FAA approval to modify an aeronautical product from its original design. The STC, which incorporates by reference the related TC, approves not only the modification but also how that modification affects the original design.”

For complex design modifications, the Aircraft Certification Office may ask that you follow the Original Design Approval Process.

When Is an STC needed?

One needs an STC to make a major change to the airplane, such as installing new technology, changing the engine, or updating the interior. One must ensure that these changes meet safety standards.

An STC is required in these instances:

• Avionics upgrades, such as adding updated navigation or communication systems
• Engine conversions, such as switching to a different engine for better performance or efficiency
• Interior refurbishments, such as modifying seating arrangements or adding new features

When an applicant embarks on the STC path, they must adhere to strict criteria outlined in the FAA’s Application to Issuance process. The 17-step process ensures only the best viable solutions obtain STC approval. Ultimately, the FAA states that an STC will be issued only if:

• Pertinent technical data have been examined and found satisfactory
• All necessary tests and compliance inspections have been completed
• Alteration has been found to conform with the technical data

Great, but what does that mean?

It means that someone decided to alter the OEM design, thereby changing how the aircraft performs, introducing a new technology, or changing its mission. STCs come in all shapes and sizes, and most fly undetected under the radar.

However, in the case of G100UL, this issue is front-row center of the headlines. Why? Because in the aviation aftermarket, change is scary.

Importance of an STC

Longtime readers  will know that we stick to the book at Maintaining Your Airplane. You will note I did not mention the OEM.

Although essential, there are other means of airworthiness compliance. It all starts with documentation: logbooks, flight records, and FAA forms. The STC documents the alterations made to the aircraft, which is essential for safety and compliance.

The STC accomplishes three main objectives:

• Standardization: Ensures that modifications meet FAA safety standards
• Airworthiness: Keeps your aircraft legally safe to operate
• Documentation: Provides a formal record of the approved alterations

Be wary of individuals who perform any work but fail to document it. Paperwork is the easiest part of maintenance—you don’t even have to get dirty. Some mechanics may fight me on that, but my concern is, if they skimp on that, what other shortcuts will they take?

STCs in the Field

There is a misconception that only third-party entities develop STCs for the aftermarket. This is not true. Times change and often aircraft are modified to adapt to that change.

For example, many Boeing 747 jumbo jets have been retired from passenger flying, but some have a new mission in cargo. Boeing has an STC to convert passenger 747 airliners into cargo carriers.

Would it surprise you that Boeing and its affiliates/partners have 159 STCs recorded in the FAA STC database? Airplane manufacturers sometimes need to update their type-certificated aircraft, and in some instances, the STC route is the most efficient.

Of course, most of the STCs available in the aftermarket are from third parties. 

Duncan Aviation is the world’s largest privately owned business jet service provider. It also has a well-stocked STC library, which is searchable on its portal. The website went live in 2019, and within the first three weeks, the company had 20 STC requests for quotes.

One solution currently making STC headlines is Starlink.

In March, AeroMech announced the issuance of an STC for Starlink on King Air 200/300 Series aircraft. It did not stop there, and Wednesday announced an STC for Citation 560XL Series aircraft.

As STCs are aircraft-specific, each model adding Starlink requires a new STC.

The post What to Know About Supplemental Type Certificates appeared first on FLYING Magazine.

The issue of what is legal (in FAA terms) and approved (by manufacturers) puts maintainers in a sticky situation. On one hand, the FAA issues a supplemental type certificate (STC) allowing for products to deploy on aircraft, but the engine and/or aircraft manufacturer may not approve or recognize the STC as something permitted for use under the terms of their warranty. 

Whether an aircraft owner or operator chooses to use the alternate fuel or not is a matter of choice. The fuel has been approved by the FAA and is perfectly legal to use in the SR series aircraft. The dilemma for the maintainer arises upon returning a Cirrus aircraft to service even for something as routine as an oil change. 

• READ MORE: Identifying Corrosion in All Its Forms

Consider this scenario. The pilot opted to refuel with G100UL or the aircraft arrived with G100UL in the tank. This alternate fuel is a drop-in replacement, so 100UL could have been added to 100LL already in the tank. Granted the maintenance action in this case did not involve fuel, but the maintainer is signing for the entire aircraft to be returned to service. If they sign the repair IAW OEM guidelines, this includes Service Advisories (including one that prohibits the use of G100UL fuel). Consequently if the aircraft is carrying G100UL, then this could be an issue because the aircraft is not being returned to service IAW this Cirrus SB.

Of course, as with any guideline, the issue of signing for an aircraft is subject to interpretation. I know mechanics that will only work on aircraft they have personal history with and do not want to return to service an inherited unrecognized maintenance action.

In the advisory (SA24-14) “Transition to Unleaded Fuel and Use of Non-Cirrus Approved Fuel in SR Series Aircraft” released June 18, Cirrus said it was committed to the industry’s transition to unleaded fuels, which is underscored by its collaboration with stakeholders such as the Aircraft Owners and Pilots Association (AOPA), General Aviation Manufacturers Association (GAMA), FAA, and Eliminate Aviation Gasoline Lead Emissions (EAGLE) industry initiative.

Aircraft and engine manufacturer’s are extremely risk averse. They historically do not recognize alternate methods of airworthiness, and this includes STCs, parts manufacturer approval (PMA) parts, and designated engineering representative (DER) repairs.

There is a commercial element to this since any aftermarket PMA part procured from a third party is a revenue lost for the OEM. It appears the reason for the SB in this specific case is Cirrus’ concern about the breakdown of a fuel tank sealant that was seen in an isolated (one) aircraft known to have been fueled with G100UL.

The company will need to vet this against other aircraft in the fleet to ascertain if the perceived breakdown is an isolated outlier related to the drop-in fuel, or if the dislodged fuel tank sealant was a manufacturing defect unrelated to the use of G100UL. 

• READ MORE: 5 Attributes of a Top-Notch Maintenance Provider

“While some aspects of the initial Cirrus testing of the GAMI G100UL fuel are encouraging, other areas, including materials compatibility, remain inconclusive,” the advisory said. “At this time, Cirrus does not approve the use of GAMI G100UL fuel in Cirrus SR Series airplanes. Per Continental and Lycoming, only approved fuels may be used for an engine to be covered by warranty.” 

According to the FAA, G100UL is safe to use, hence the STC approval. This took years of testing to clear the milestones. In fact GAMI uses the fuel in its company SR22..

According to GAMI, the fuel has undergone substantial testing and displayed no issues on other aircraft. The company also disputes Cirrus’ claim that using G100UL voids the warranties on engines supplied by Lycoming and Continental, however, the engine manufacturers have confirmed its use could affect warranty claims, according to AVweb. 

Tim Roehl, president of GAMI, indicated that his team is drafting a formal response to Cirrus Service Advisory SA24-14 to be posted on its website. Roehl also said that the sealant Cirrus references is not the polysulfide sealant more commonly used in the industry but a polythioether sealant. Roehl stated that G100UL has been in service since 2010 on one wing of the company’s Cirrus SR22, using the same polythioether sealant Cirrus uses, with zero incidents.

The FAA does not comment on specific OEM warranty policies but the agency has reiterated that GAMI’s G100UL does have the STC approval. This is not uncommon as the FAA routinely approves alternate solutions without the buy-in from OEMs. The burden is on the third-party solution provider to prove airworthiness—i.e. STC holder, PMA manufacturer, or designated engineering representative for DER repairs.

What This Means for Maintainers

This fuel issue places aircraft maintenance professionals in a bit of a quandary. On one side, you have the FAA approval for G100UL, but at least one aircraft manufacturer, Cirrus, and one engine manufacturer, say they are not approved via service advisories.

The FAA typically steers clear of airframe/powerplant OEM issues until they become an airworthiness directive (AD). To assist in clearing any confusion, the agency issues periodic documents to help owner/operator/maintainer stay abreast of the situation. One such publication is the FAASTeam service bulletins.

When asked if service bulletins are mandatory, the FAA says: It depends. 

Here is a quick agency ruling: “If you are operating your aircraft under 14 CFR part 91, a service bulletin is advisory, and compliance is not mandatory unless it is included in an Airworthiness Directive.”

Another resource is FAA Advisory Circular AC 20-114, which addresses manufacturers’ service documents: “Service documents should be neither treated nor represented as the official FAA approval documents, unless either a letter of design approval from the FAA or a record that compliance has been determined by an FAA designee is on file for recommended actions indicated as FAA-approved in service documents.”

That said, service documents are beneficial and transmit a wealth of knowledge. When returning aircraft to service, it is critical to list if the action is in accordance with OEM information or another alternate form of maintenance. This comes into play when installing PMA parts, or an STC like G100UL.

The post Cirrus Service Advisory Throws Fuel on G100UL Maintenance Debate appeared first on FLYING Magazine.

As aircraft progressed, so did the enemy. Corrosion identification, prevention, and treatment is an ongoing battle.

• READ MORE: An Introduction to Aircraft Inspections

According to an EAA Sport Aviation article that makes a clear distinction about corrosion on wooden aircraft: “Lest you think corrosion is something that only happens to metal, wood can also develop a sort of organic rust. Known as dry rot, this fungus is caused by too much moisture content and can render wood unusable.” 

Corrosion will look slightly different in wooden ribs, spars, and longerons.

When it comes to inspecting structural wood, late vintage aircraft restorer Ron Alexander, who wrote about managing, flying, and maintaining aircraft for Experimental Aircraft Association’s (EAA) Vintage Aircraft Association, said there is a lengthy list of items to check.

According to Alexander, some of the things to look for include:

• Signs of mildew, which occurs due to excessive humidity and heat and potentially leads to dry rot

• Loosening of nails, which may be evidence of adverse movement of the spar
• Moist or wet wood
• Erosion of varnish or finish that could lead to the growth of fungus within wood fibers
• Any observable stains, which are accompanied by rot

What Is Corrosion?

Corrosion presents altogether differently in metal aircraft. But what exactly is it? 

According to the FAA Advisory Circular AC No: 43-4B, corrosion is the “electrochemical deterioration of a metal because of its chemical reaction with a surrounding environment.” That’s a fancy way of saying rust.

• READ MORE: How to Care for Your Lycoming Camshaft

Corrosion is a natural process that affects metal through chemical or electrochemical reactions, transforming it into compounds like oxides, hydroxides, or sulfates. Unlike erosion, which damages materials through mechanical action, corrosion occurs as metals seek to revert to their natural state, the FAA said.

For corrosion to take place, four specific conditions must be met:

1. Presence of an anode or a metal that will corrode
2. Presence of a cathode, a dissimilar conductive material that has less tendency to corrode
3. Presence of an electrolyte, a conductive liquid
4. Metal-to-metal contact or a fastener that usually makes electrical contact between the anode and cathode

Elimination of any one of these conditions will stop corrosion. 

More Than an Airframe Problem

Corrosion is the silent killer of aircraft, and if left undetected, it could wreak havoc on your equipment and operation.

When most of us think about corrosion, it is typically in a highly exposed environment that is unprotected from the elements, like wheel wells. However, corrosion can occur anywhere on the aircraft, including, but not limited to, propellers, avionics, and engine parts.

The FAA outlines methods, techniques, and practices acceptable for inspecting, preventing, controlling, and repairing corrosion on avionics systems and equipment in its advisory circular AC 43-206.

“Studies have shown that 20 percent of avionics equipment failures are a direct result of corrosion,” the FAA said. “Even minute amounts of corrosion can cause intermittent malfunctions or complete equipment failures.”

Another critical area of concern for corrosion is propellers. According to legacy prop maker Hartzell Propeller, the different versions of propeller corrosion include uniform surface corrosion, pitting corrosion, intergranular corrosion, and stress corrosion/cracking.

“Keep in mind that the forms of corrosion vary with the type of metal involved, the age of the aircraft, atmospheric conditions, and the length of time that the aircraft is exposed to corrosion,” the company said.

The post Identifying Corrosion in All Its Forms appeared first on FLYING Magazine.

Diving deeper into the world of aviation spark plugs, we will pull back the cowling and affix our inspection mirror to discuss the types commonly used in different aircraft models, insights into their maintenance, and recommendations for their replacement. 

Understanding the Basics

At their core, spark plugs are devices that deliver electric current from an ignition system to the combustion chamber of an engine, igniting the compressed fuel/air mixture by an electric spark. Properly functioning spark plugs are essential for smooth engine operation and optimal performance.

Types of Aviation Spark Plugs

“The two major types of electrodes in today’s spark plugs include the dual nickel alloy massive electrode and the single Iridium fine-wire electrode,” saidAlan Woods, sales manager for piston and power at Champion Aerospace in Liberty, South Carolina. “The nickel alloy electrode design allows for a long-lasting spark plug [300 to 500 hours] at an affordable price. The Iridium fine-wire electrode design offers TBO life [2,000 hours plus] but at a higher cost due to the high cost of Iridium [$4,000 per ounce].”

Massive Electrode Spark Plugs

Massive electrode spark plugs are the most commonly used type in general aviation. They feature large electrodes designed for durability and extended use.

• READ MORE: Intro to Aviation Spark Plugs

Massive electrode plugs are critical features in terms of durability. They can withstand significant wear and tear, making them ideal for aircraft that undergo frequent and long flights. Massive electrode plugs are also cost-effective. They are generally more affordable than their counterparts, the fine-wire spark plugs. Another attribute is their ease of maintenance. Due to their stout construction, massive electrode plugs are easier to clean and maintain.

There are a few downsides to massive electrode plugs. Over time, massive electrode spark plugs can suffer from performance issues due to electrode wear and increased gap size, leading to less efficient combustion. They are also heavier as the larger electrodes add to the weight, which can be a minor concern in aircraft performance calculations.

Fine-Wire Spark Plugs

Fine-wire spark plugs are designed with thinner electrodes, often made of precious metals such as platinum or Iridium, to provide superior performance and longevity.

The fine-wire plug offers improved ignition over massive electrodes, giving the fine-wire electrodes a more concentrated spark and leading to better combustion and engine performance. They also last longer because they are constructed using durable materials, such as platinum and Iridium, reducing the frequency of replacements. Fine-wire plugs are also lighter than massive electrode plugs, contributing to overall aircraft efficiency.

• READ MORE: Breaking Down Sudden Stoppage Inspections

These enhanced attributes come with a cost. Aircraft fine-wire spark plugs are substantially more expensive than massive electrode spark plugs. They also require careful handling during maintenance to avoid damaging the fine electrodes.

Choosing the Right Spark Plug 

The choice between massive electrode and fine-wire spark plugs often depends on the specific requirements of your aircraft and your flying activity. Massive electrode spark plugs might be more suitable if you fly frequently and cover long distances due to their durability and cost-effectiveness. Fine-wire spark plugs could be the better choice if you prioritize engine performance and are willing to invest in premium parts due to their enhanced ignition efficiency and longevity.

Fine-wire plugs provide a more efficient burn rate and last longer at a much higher purchase price, according to Vince Bechtel, director of aftermarket sales at Tempest Aero Group, which entered the aviation spark plug market in 2010 by acquiring the Autolite brand. A relatively small niche market, the company represents about 10 to 15 percent of the aviation aftermarket. Turbocharged aircraft flying at higher altitudes favor fine-wire plugs, according to Bechtel.

• READ MORE: Servicing Cessna 172 Stuck Exhaust Valves

Maintenance and Replacement Recommendations

Proper maintenance and timely replacement of spark plugs are crucial to avoid engine misfires and ensure smooth operation. Some tips:

●      Regular inspections: Conduct routine inspections every 100 hours of flight time or as your aircraft’s manufacturer recommends. Check for signs of wear, fouling, or damage. Common issues include carbon buildup, oil fouling, and electrode erosion.

●      Cleaning: Use an approved spark plug cleaner to remove carbon deposits and debris. Be cautious with fine-wire spark plugs to avoid damaging the delicate electrodes.

●      Gap checking: Ensure the spark plug gap meets the manufacturer’s specifications. A correct gap is crucial for optimal spark plug performance. Adjust the gap if necessary using appropriate tools.

●      Replacement: Replace spark plugs at the manufacturer’s recommended intervals or if significant wear or damage is observed during inspections. Always use spark plugs that meet the specifications of your aircraft’s engine model.

“Honestly, the biggest issue I see is over-cleaning,” Bechtel said. “Individuals and shops tend to clean plugs until they look brand new out of the packaging. The only thing this does is wear out your electrodes and insulator faster, preventing you from getting the full life out of a set of plugs.”

Troubleshooting Common Spark Plug Issues

Even with regular maintenance, spark plug issues can occur. Some common problems and their potential causes include:

Engine Misfire

• Caused by worn electrodes, incorrect gap, or fouled plugs.
• Solution: Inspect, clean, or replace the spark plugs as needed.

Hard Starting

• Often due to spark plug fouling or improper gap.
• Solution: Check and clean the spark plugs and correct the gap.

Poor Engine Performance

• Can result from degraded spark plugs or incorrect heat range.
• Solution: Verify that you are using the correct type and heat range of spark plugs for your engine.

The introduction of fired-in suppressor seal technology, or FISS, is a recent advancement in aircraft engine spark plugs.

“This technology eliminates the high-voltage silicon resistor, which is prone to resistance value increases over time,” Woods said. “The FISS technology incorporates fired-in conducting and suppressor glasses that establish the resistance value of the spark plug. This means that the end user has a stable resistance value over the entire life of the spark plug. With the introduction of electronic ignition, spark plug designs will evolve with wider gaps to handle the increased energy being produced.”

Understanding the various types of aviation spark plugs and their benefits and limitations can help you make informed decisions about aircraft maintenance. Whether you choose massive electrode spark plugs for their durability and cost-effectiveness or fine-wire spark plugs for their superior performance and longevity, regular maintenance and timely replacements are critical to engine operation. 

Please consult your aircraft’s technical publications and an A&P mechanic to ensure your spark plugs are in an airworthy condition.

The post Keeping Current With Aviation Spark Plugs appeared first on FLYING Magazine.

As many of you know, I owned and operated an aircraft engine shop for more than a decade and consistently handled sudden stoppage inspection cases. The jobs were so common that we even had T-shirts printed with the phrase, “Things get hot when the big fan stops.” Sometimes, humor can help take some of the sting away. Like the late Jimmy Buffet sang, “…if we couldn’t laugh, we would all go insane.” Aircraft ownership and maintenance will do that to you. This is why we all gather here to swap stories, support each other, and maybe learn a little something along the way.

Disclaimer: Today, we are discussing air-cooled reciprocating engines. The criteria are different based on engine type.

Defining a Propeller Strike

As with many things in aviation, the definition of propeller strike is hotly debated. The same is true of what maintenance evolution is applicable after determining if a prop strike occurred. More on that later. First, let’s determine what a propeller strike is.

The FAA sets the bar high by including a sudden stoppage question in the FAA-S-8081-28A Aviation Mechanic Powerplant Practical Test Standards. Part C on engine inspection, drawing on the references from 14 CFR Part 43; AC 43.13-1B and FAA-H-8083-32, states the objective is to determine that the applicant can demonstrate “knowledge of an inspection required after a potentially damaging event, including but not limited to any of the following: sudden stoppage, over speed, or over temperature.” Even among A&Ps, there is a wide disparity in interpreting the definition, with subsequent actions also in question.

Some A&Ps are jacks-of-all-trades, while others are highly specialized. Based on experience, I recommend dealing with specialists regarding critical components such as avionics, powerplants, and propellers.

• READ MORE: 5 Attributes of a Top-Notch Maintenance Provider

What constitutes a propeller strike? Let’s check with the experts and see what the OEMs say.

According to Service Bulletin SB96-11B, Continental Aerospace Technologies defines a propeller strike as: “(1) any incident, whether or not the engine is operating, that requires repair to the propeller other than minor dressing of the blades as set forth in Part I, B of this Service Bulletin or (2) any incident while the engine is operating in which the propeller makes contact with any object that results in a loss of engine rpm.”

Our friends in Lycoming County, Pennsylvania, in their Service Bulletin No. 533C, define a prop strike as:

• Any incident, whether or not the engine is operating, where repair of the propeller is necessary.

• Any incident during engine operation where the propeller has an impact on a solid object. This incident includes propeller strikes against the ground. Although the propeller can continue to turn, damage to the engine can occur, possibly with progression to engine failure.

• Sudden rpm drop on impact to water, tall grass, or similar yielding medium where propeller damage does not usually occur.

How It Happens

During my engine shop days, I can say with certainty that no two sudden stoppage inspections were alike. Scratch that. We did have one client who cranked his Cessna’s engine with the nosewheel tow bar still attached to the aircraft not once, but twice. True story: The first incident occurred, and the owner dutifully called the shop for an estimate. We bid the job, won the business, and carried out the maintenance action to get the good doctor (he was an oncologist) airborne once again. Or so we thought.

Twas less than a fortnight before he rang the shop again. After installing the engine, the mechanic reconnected the baffling, linkage, and appropriate hoses, instructing the owner to crank it up—yes, with the towbar once again still attached. At least the parts bill of materials (BOM) was easy to create. In fairness, his ground support person should have alerted him that the tow bar was in place. As with most aircraft incidents, it was a breakdown of systems, communication, and practices mixed with bad luck.

• READ MORE: Servicing Cessna 172 Stuck Exhaust Valves

We also saw plenty of the traditional ways propeller strikes occur. Taildraggers are in danger of ground looping. Tricycle gear aircraft brake too hard and dip the nose or hit a depression on a grass field and catch the propeller. Once, a client called to say they approached their aircraft to do a walk-around and found shattered glass from a blue taxi light lens in the cowling during the preflight inspection. There was nothing in the logbook about this. I had one customer taxi into a hangar door and another into a second aircraft.

One of the pricier inspections we accomplished was a Piper Navajo that landed gear up. Upon tearing down the engine, we found special H5 Lycoming connecting rods. There was no way to know this during the estimate phase, and we had to tell the client that his bill had just gone up. All of this is to say propeller strikes are more common than one might think.

There is one other hazard that causes prop strike concerns for pilots—wildlife. Most everyone knows the story of Captain Sully and the “Miracle on the Hudson.” Did you also know that according to the FAA Wildlife Strike Database, about 272,000 wildlife strikes with civil aircraft were reported in the U.S. between 1990 and 2022? That is a lot of damaged aircraft.

The encounters are only sometimes birds. Some pilots report striking white-tailed deer and even elk in the northern states. The FAA launched the Wildlife Hazard Mitigation program to help counteract the effects of wildlife on airports. On the program website, the FAA states that “during the past century, wildlife-aircraft strikes have resulted in the loss of hundreds of lives worldwide, as well as billions of dollars in aircraft damage.”

Incident Confirmed—Now What?

As certified aircraft mechanics, the FAA mandates we operate with the highest degree of safety conscience, and demand the same of those we work with. An excerpt from the Mechanic’s Creed states, in part, that “I shall never knowingly subject others to risks which I would not be willing to assume for myself, or for those dear to me.” In layman’s terms, we often ask ourselves, would you fly behind it? Once you qualify the occurrence as a propeller strike, what happens next? There are three distinct camps in this regard. So as not to sound inflammatory and stir emotions, let’s designate them as teams A, B, and C.

Strictly for identification purposes, let’s say Team A equals “all good, keep flying,” Team B “better do the minimum,” and Team C “conscientious.” This division stems from misconceptions about what to do after a propeller strike. The major engine manufacturers, Lycoming and Continental, are clear on the action needed in their respective service bulletins. For Lycoming applications, some have attempted to circumvent this by their interpretation of AD 2004-10-14. Team B will point to the statement: “Remove the existing gear retaining bolt and lockplate from service, and install a new bolt and lockplate, in accordance with steps 6 and 7 of Lycoming MSB No. 475C.” It believes this is the bare minimum needed. It argues that an Airworthiness Directive (AD) takes precedence over a service bulletin. However, this AD references SB475, not SB533C. Are you confused yet?

• READ MORE: Testing the Hardware After a USM Retrofit

Like every other aircraft maintenance evolution, the bottom line is comfort. Are you comfortable accomplishing the bare minimum and avoiding the messiness and expense of an engine teardown? Just know that we have found cracked crankshafts before when doing the magnetic particle inspection. When asked about potential damage on its website in an article entitled “Prop Strike: What’s Next?” Hartzell Propeller said, “Even if there’s no visible damage to the propeller, there may be hidden internal damage to the propeller, governor, crankshaft, and other components that can cause engine failure later in the engine’s life, if not immediately.” That sounds definitive to me.

A chance to perform maintenance, like that following a prop strike, is also an opportunity to find other issues. Some argue that mechanics cannot unsee issues, which will increase the repair cost. Dare I say there is no such thing as too much maintenance? I recall an instance when a Beechcraft Baron B58 operator suffered a propeller strike and contracted us to perform the inspection. The engine was a Continental IO-550-C model configured with a front-drive alternator. During disassembly, our technician noted the lock tabs of the face gear hardware were not bent, locking the bolt in place. Subsequently, this caused a crack in the crankshaft ring gear mounting flange. It scrapped the crankshaft. This customer operated a fleet of Barons, and we sent word to them to inspect the remaining aircraft.

This issue is just one example of many we found through engine maintenance. Another common squawk involves camshafts going bad. Typically caused by corrosion, the camshaft will begin to wear abnormally and spall the lifter. While the charges for the parts to repair these discrepancies fall outside the scope of maintenance for the sudden stoppage inspection, the labor is covered and, therefore, essentially free. A real bargain. Another key point I highlight to my clients: Do you want to find out about that issue in the shop or at altitude?

Tap into Knowledge

The aircraft reciprocating engine business is a tight-knit group of folks quick to help each other out. That’s what I love about this industry. This is especially important since, while most information is easily accessible, there are some things that are either not readily available or just industry tips one picks up through the years.

For example, did you know that your dry air vacuum pumps require replacement after a propeller strike? Consult Tempest Service Letter SL-008, with an opening statement that reads: “When a Tempest engine-driven air pump is subjected to sudden engine stoppage (for example, propeller strike during a gear up landing), the rotor and vanes of the pump may sustain damage. This damage may not be evident by rotating the pump or by visual examination.” What about Rapco? Same story. Refer to Service Letter RASL-003, which states: “When a Rapco Inc. pneumatic pump has been subjected or is suspected of having been subjected to sudden engine stoppage or propeller strike event, it is mandatory to replace the affected pneumatic pump before further flight, in accordance with the procedure outlined below.”

What about magnetos? Champion Slick Service Letter L-1363 states that “magnetos must be overhauled after a lightning strike on the aircraft, a sudden engine stoppage, prop strike, or immersion.” Are you picking up on the pattern yet?

Here is a fun fact: Lycoming has a surprise for the newer model engines. Earlier, we mentioned Lycoming Service Bulletin No. 533C. Reading through the SB, you will see “NOTICE: Roller tappets, counterweight rollers, and bushings must be replaced.” You read that correctly: Replacing roller tappets during a sudden stoppage inspection is mandatory.

How is someone supposed to keep all of this straight? You’re not. Aviation is a team sport. Do your homework and trust the professionals. Most engine shops are willing to go the extra mile to help you. Ensure you work with one with high standards. The rules are constantly changing. In years gone by, Lycoming allowed certain repairs for a bent propeller flange on engine crankshafts. With the publication of Service Bulletin No. 201F, this is no longer the case. The SB reads, in part: “Lycoming Engines no longer allows bent crankshaft flanges to be ground or repaired to restore maximum run-out. As per Service Bulletin 533B, if the crankshaft is bent, it must be replaced.” A good shop will help you decipher this.

Hidden Problems

I wanted a firsthand account of the “to tear down or not tear down, that is the question” debate, so I checked in with JD Kuti from Pinnacle Aircraft Engines in Silverhill, Alabama. When asked if his team ever found issues during teardown after a propeller strike, Kuti responded with a resounding: Absolutely!

Here are the common issues discovered:

• Crankshaft flange bent

• Crankshaft cracked at flange or slinger ring

• Crankcase cracked

• Gear teeth cracks

This feature first appeared in the April 2024/Issue 947 of FLYING’s print edition.

The post Breaking Down Sudden Stoppage Inspections appeared first on FLYING Magazine.

Taylor built the world’s first aircraft engine from a scratch-paper drawing tacked up to his work bench. He had no formal training and made do with what he had to work with. I am still amazed to this day by what Taylor pulled off.

• READ MORE: The First Aircraft Mechanic

Aircraft mechanics often quietly apply our trade behind the scenes, ensuring the world stays connected via air travel. Each of us has a story to tell.

In thinking of the next generation who will work on airplanes, what story would you tell to inspire them? 

Born Into the Business

Some of us cannot help it; we were born into this life. I didn’t choose the jet life; the jet life chose me. My dad worked for the Beechcraft distributor Hangar One in the 1970s. Once, he took me on a business trip with him through middle Georgia, and I took a ride in a taildragger. My life has not been the same since.

This week, I met Suresh Narayanan, owner and CEO of Jets MRO in Dallas. Narayanan is doing what he can to solve the high turnover in aircraft maintenance by offering company-paid benefits, enhanced work culture, and path to partial ownership. He also has no sales representatives and expects his mechanics to communicate with the customer. 

What drove this CEO to appreciate his mechanics in this manner? His father was a Concorde mechanic for British Airways, and he grew up on a steady diet of airplane stories, which he still recalls fondly.

In March, I spent the day at Airbase Georgia, the local Commemorative Air Force (CAF) squadron. The theme was “Rosie the Riveter” in honor of its Stearman project. I witnessed parents walking with their sons and daughters, checking out the swag at the PX tent, taking photos with reenactors, and getting up close and personal with warbirds Some even had custom dog tags made.

One of the best parts was seeing folks, young and old, stand and stare when the Douglas SBD-5 Dauntless taxied up the grinder, its big, powerful engine pounding out a symphony of 1,200 hp before shutting down. I don’t care who you are, a warbird will freeze time for just a minute while you soak it in.

How many aviators or maintainers crossed over that day? What is their story? Only time can tell.

Answering the Call

Paul Hendrickson was just a small child when his father, Joe Paul, left for World War II. What happened in the war changed him forever. I recently had a conversation with Hendrickson just as he was about to wade into his local trout stream at Valley Forge, Pennsylvania. Hendrickson recently published a book about his father’s experience during the Iwo Jima campaign called Fighting the Night. He told me the story of a sharecropper’s kid who learned to work on tractors in western Kentucky during the 1930s. One day, a Ford Trimotor flew over the farm, and the boy was hooked.

All those hours working on tractors and Ford Model T’s paid off. Paul Hendrickson recalls his father learning of his new job in the military.

“He had boot camp ahead of him, but the Air Corps Technical School had already promised him a place in its airplane mechanics class,” Hendrickson said.

Tech school began in the fall of 1937 at Chanute Field in Rantoul, Illinois. The elder Hendrickson’s WWII story began as a mechanic but ended with flying night missions in a P-61 Black Widow. Afterward, Joe Paul Hendrickson earned his A&E mechanic license, the precursor to the A&P.

The old Chanute Field became Chanute Air Force Base before closing in 1993. An estimated 2 million students trained there. Each was either a farm boy or a city kid, but they answered the call and had to live their own story. 

Coming Full Circle

Sometimes a story begins with a simple idea. Stacey Rudser, president and scholarship chair of the Association for Women in Aviation Maintenance (AWAM), had such an idea when she enrolled and became the first female to graduate from the Aviation Institute of Maintenance (AIM) in Orlando, Florida, earning her A&P in 2009. You may have seen Rudser’s pink boots sticking out of an avionics bay at some point.

Rudser offered her thoughts on what AMT Day means to her.

“On this AMT Day, AWAM celebrates all the women working to keep our skies safe,” she said. “We are a small but mighty part of this very special industry and are encouraged to see how many women are entering the ranks of schools and transitioning to the military. Thank you to all the mentors, advocates, and allies as we continue to show that aviation maintenance is a vibrant and viable career for all.”

How did Rudser’s maintenance story begin? In 2013, she earned a 767 maintenance training scholarship for UPS through AWAM. Life has a way of coming full circle, and Rudser went from that honor 13 years ago to personally touching the lives of 26 young women through scholarship awards this year.

Now, that is how you pay it forward.

The post AMT Day Offers Opportunity to Inspire Next Generation appeared first on FLYING Magazine.

He fired up the aircraft, only to find the Continental O-300-D engine started running rough. That was as far as it went. Mission aborted. The aircraft never left the ground.

Aircraft Troubleshooting

Cessna 172 owner Corey Sampson reached out to me to discuss the engine running rough and the dark side of maintaining an aircraft: unscheduled maintenance.

The first step in the troubleshooting chain was to remove and replace (R&R) the spark plugs, as they were coming due soon. That didn’t help. The next step was to run the engine while idle, using a hand-held laser thermometer, and take the temperature of each cylinder one at a time. 

• READ MORE: Cessna 172 Maintenance Planning

One by one, the temperature readout for each cylinder measured 150 to 160 degrees Fahrenheit. The number 4 cylinder was 95 F. Cylinder number 5 was 159 F, and number 6 was back to around 95 F. 

Sampson could now perform preventative maintenance by wearing his owner/operator hat. Once troubleshooting leads beyond preventative maintenance, it is time to turn around the hat to the A&P side and begin unscheduled maintenance. 

Unscheduled Aircraft Maintenance

There is a trick to relieving pressure off the valves to remove the rocker arm while keeping enough resistance to hold them in place to pop off the rotocoil, keepers (valve locks), and springs. It was time for the rope trick.

Checking in with JD Kuti, president of Pinnacle Aircraft Engines in Silverhill, Alabama, I asked him to break down the procedure for me:

• Feed rope into the spark plug hole.
• Spin the prop until the rope holds the valve in place.
• Use the spring compressor tool to remove the keepers and valve springs.

I watched a mechanic on the internet try to pry off the valve keepers with a pocket knife. That looked like a good way to get cut to me. Back in my engine shop days, we just popped a magnet against the valve locks, and voilà, you set them free.

• READ MORE: The Daily Life of a Repair Station

Kuti mentioned a trick he has used in the past while servicing valve guides: “If you need to drop the valve into the cylinder, tie a piece of floss to the valve through the port. If I’m cleaning a guide, I normally push the valve into the cylinder and pull it out of the bottom spark plug hole to clean the valve stem too.” 

Kuti said he does not deploy the rope trick any longer, opting to pressurize the cylinder with air while the piston is at the bottom dead center (BDC).

Reamer Action Time

Sampson removed the spark plugs and fed the rope into place. Driving out the rocker shaft with a brass drift, he removed keepers and springs. It was then time to drop the valve. Taking the brass drift, he gently tapped the exhaust valve into the cylinder head. 

Special reamers like these are just the ticket to clean up the valve guides. Slowly slipping the reamer into the number 6 exhaust guide, the tool moved smoothly for approximately one-half inch, then began to drag. The reaming process is not difficult, but it is imperative to keep the tool aligned so as not to damage the valve guide.

Where Kuti held the valve with a thin line, Sampson used mechanical fingers in the top spark plug hole to maneuver the exhaust valve back into place. With a flashlight in the bottom spark plug hole; the valve was visible and could be manipulated toward the guide. 

Once in place, a magnet was inserted into the exhaust guide, contacting the tip of the valve stem, and the valve was slowly pulled back into place. Next, the valve springs and keepers were replaced, topped off with a rotocoil or upper retainer, depending on your setup.

• READ MORE: Testing the Hardware After a USM Retrofit

In aircraft maintenance, the line between preventative and unscheduled maintenance can often blur. While he had the time and the tooling available, Sampson opted to apply the reamer to all of the remaining cylinders’ exhaust valve guides as a precaution.

What causes exhaust valves to stick? 

“Heat is the primary cause of valve sticking,” according to AVweb. “High temperatures in the exhaust valve guide oxidize oil and form carbon deposits on the valve guide, and these deposits can cause the valve to stick. The most frequent reason for elevated valve temperatures is valve leakage.”

The post Servicing Cessna 172 Stuck Exhaust Valves appeared first on FLYING Magazine.

Working on airplanes is like the Wild West sometimes. You have the good, the bad, and the ugly. Here are the top five attributes that should indicate your mechanic or shop is operating in the green:

Certifications

In the 1989 movie Parenthood, Keanu Reeves’ character states you need a license to buy a dog, drive a car, and even catch a fish. Guess what else you need a license for? If you said work on an airplane, you would be wrong. 

You need a license to return an airplane to service. Are individuals certified airframe and powerplant (A&P) mechanics? If you are inquiring about a maintenance repair and overhaul (MRO), are they CFR Part 145 certified? 

Stick with certified mechanics and shops. Just because someone’s cousin has a sick Chevelle and could change your Mooney’s oil doesn’t mean you should let them.

Tools and Equipment

Tools and shop equipment are the mechanisms by which we aircraft mechanics ply our trade. Are the  tools calibrated? Like a surgeon’s scalpel, we rely on the precision of our measuring instruments, the integrity of the torque wrench, and the sweet sound of the one-quarter-inch SK ratchet clicking through its turn. 

Airplanes are notorious for tight turn radius, and the SK version was second to none. For top-notchers, it is all about performance, not the show.

Technical Publications

Just like a pop quiz, if an inspector casually inquires about the airspeed velocity of an unladen swallow, the proper thing to do is puff up one’s chest and spout the answer in a good voice, right?

Wrong.

I have mentioned my ex-partner from the engine shop and his propensity to drop some knowledge on anyone who crossed his path—especially the FAA. It finally got to the point where I coached my crew to answer, regardless of the question, with this phrase: “Whatever the latest revision of the manual states.” 

I once had a primary maintenance inspector (PMI) advise me to stamp any printed material “FOR REFERENCE ONLY” in big red letters. His rationale was that the manual could have changed while we walked from the office to the shop.

I know this seems a bit like overkill, but there is truth in the sacred texts. It amazes me the number of mechanics I encounter who call the parts dealer with no clue as to the part number of their line replaceable unit (LRU). Ensure the facility you use is up to date and has the content library for your make and model.

Safety

Have you ever tried to pull over and check under the hood at 9,000 feet? That’s tough to do. Of course, no one is perfect, and accidents happen, but at what severity and frequency? 

Do a little homework on the shop or mechanic you are considering. Have they been cited by the FAA for naughty behavior? Remember, it’s all fun and games until someone gets their name in the newspaper.

Culture

The previous points are fairly straightforward. Is the entity certified? With a little due diligence, one can ascertain if the tooling is in order, technical publications accessible, and everyone has a clean record. 

What you truly need to understand is the culture. Specifically, are the employees empowered to speak up if something is wrong? In the case of a sole proprietor, is he or she the type of person to come clean and be honest with you?

We had a standing rule at my 145 engine shop. If you drop a tool in an engine and you raise your hand in confession, nothing bad will happen to you. It might be a long weekend, and no one is going fishing on Saturday, but zero disciplinary action would come down on you. What would happen is called a safety stand-down, Everyone stops what they are doing, and we go after the tool/part/foreign object debris. 

Have you ever heard the phrase “trust your instincts?” Well, it applies in this case as well. The best piece of advice I will give you—and I cannot stress this enough—is to spend some time on-site. Visit the shop several times if you can. Go unannounced and see how the staff react. I once knew a shop where, upon first sight of a dark late model Ford, the employees would scatter to the wind—all of them. For the record, I do not recommend that shop to my clients.

You will notice I didn’t mention how long it has been in business. Experience matters, but only competent experience. There are some working in the industry that are doing it wrong and have been for years. Stick with the professionals. 

The post 5 Attributes of a Top-Notch Maintenance Provider appeared first on FLYING Magazine.

Recently, we cheered on Stephen Mercer as Gardner Lowe Aviation Services in Peachtree City, Georgia, put the finishing touches on his family’s 1982 Piper PA-32R-301T Saratoga. Now, it is time for the pull-offs from that job to find a new life in Corey Sampson’s Cessna 172. We have been tracking this story from the beginning with Sampson’s decision to incorporate used-serviceable material (USM) in his retrofit. 

• Part 1: Cessna 172 Skyhawk Avionics

It is one thing to pull out the Garmin catalog and order up everything new and quite another to retrofit using USM. One must decide what to keep and what to jettison. The situation is not always cut and dried. What if you install all this stuff, and it doesn’t work? 

Thankfully, Sampson is an A&P and can do much of his own work. 

Avionics Equipment Installation

Planning for a major maintenance event comes down to one key element: attention to detail. I have seen more than one maintenance evolution derailed by the smallest detail. I once found myself stalled on a job—a major engine overhaul—for one bolt. Guess what? The airplane needs all of the parts to fly, not just some of them. 

I caught up with Sampson recently to follow up on the installation. He said that although routing was challenging, he didn’t hit any real snags along the way. 

Sampson mapped out his maintenance, and FLYING was there during the initial phases of this evolution. He ensured a clean, comfortable space in which to accomplish his work. The environment is everything in aircraft maintenance. Why do you think line maintenance aircraft mechanics receive a premium? Other factors to consider are tooling and technical data. Sampson had each of these lined up before removing a single component.

Sampson said the downtime for his 172 during maintenance was five weeks for the removal and installation, and one week for pitot-static recertification. He also removed the automatic direction finder (ADF), as it is now obsolete, and therefore, he could save some weight. 

Fitment and Operational Check

Once Sampson finished everything, it was time for Oasis Aviation Avionics & Maintenance to do the pitot-static and transponder check. The company also built up the harness and mapped everything to assist him during installation.

• Part 2: Cessna 172 Skyhawk Avionics

Once Sampson installed everything, it was time to button her up and functionally test the new hardware. To keep from running the engine in the hangar, he procured an external power supply from Aircraft Spruce & Specialty. 

“These portable power supplies are an excellent way to power your avionics on the ground while you train or practice in the cockpit,” the company says. “Especially helpful in learning how to operate glass cockpit avionics and panel mount GPS units.”

They are also furnished with Cessna-style, three-pin plug configuration and manufactured in the U.S.

Next, Sampson programmed and calibrated the two Garmin G5 Electronic Flight Instruments. Once that was complete, it was time to test fly the airplane around the pattern in Peachtree City. After the pitot-static check, he flew to New Orleans with his co-conspirator, Elijah Lisyany, for breakfast.

Continued Airworthiness Action

According to the FAA, “continued airworthiness requires that safety concerns within the existing fleet be addressed, and the knowledge gained applied for the benefit of future fleets as well.” 

The International Civil Aviation Organization (ICAO) breaks it down even further, stating that continued airworthiness “means all of the processes ensuring that, at any time in its operating life, the aircraft complies with the airworthiness requirements in force and is in a condition for safe operation.”

• READ MORE: Getting the Most from Your Prepurchase Inspection

That means Sampson now has to shift his maintenance plan to accommodate his new equipment.

Earlier in the project, Sampson opted for a Garmin GNS 430. Once installed, Corey adjusted the contrast, and viola, it worked beautifully. 

In January, Garmin issued Service Advisory (SA) 23018 Rev B—does it affect the continued airworthiness of Sampson’s Cessna 172? 

It depends. 

First of all, service advisory alerts are just that—advice. The only thing mandatory under FAR Part 91 is an airworthiness directive (AD). 

The SA clearly states that “display repairs for the WAAS and Non-WAAS GPS 400, GNC 420, and GNS 430 are no longer available and have been discontinued.” It does not say the units have been discontinued. 

Additionally, if feasible, someone could create an alternate repair either by DER or 145 process specification. There is more than one way to stay compliant. And, of course, Sampson could replace the unit with another USM GNS 430 or upgrade to Avidyne IFD 440.

The post Testing the Hardware After a USM Retrofit appeared first on FLYING Magazine.

Last October, we met Stephen Mercer, who had recently acquired a 1982 Piper PA-32R-301T Saratoga, which he was upgrading with safety features. I am proud to report that our Saratoga came through with flying colors. You see, the fine folks at Gardner Lowe Aviation Services in Peachtree City, Georgia, took extra special care of this airplane and presented Mercer with the finished product in time to fly off to some Saint Patrick’s Day shenanigans. 

• READ MORE: Piper Saratoga Avionics Install: Part 1

Not to worry, the Saratoga pull-off parts went to a good home. As you recall, we joined Corey Sampson on his quest to economically remake his Cessna 172, and what is one man’s core is another’s used serviceable material (USM). 

Items removed from the Saratoga included:

• Garmin GMA 340 audio panel
• Garmin GNS 530W GPS
• Garmin GNS 430 GPS
• Garmin GTX 330 transponder 
• JPI 700 engine monitor 
• Garmin GI 106A VOR/ILS/GPS indicator

Sampson functionally tested and installed these units. The parts are now up and flying in his Cessna 172. 

Dual Garmin G3X with a Side of ADI GI275

Mercer is on a mission. His father-in-law is learning to fly. Their family also needs a recreational aircraft with a lift and range suitable for their needs. Why not accomplish both with one airplane? The family settled on an early 1980s Saratoga and plotted the next course of action.

A new panel was the first order of business. Mercer said the team could have saved money with Aspen Avionics but received recommendations for Garmin. After a careful review of the different platforms, it chose two each of the 10-inch Garmin G3x G3X Touch for certificated aircraft. Although a little pricier than others, it fits the Mercer family mantra: “You cannot put a price on safety.” Additionally, they also added a standby Garmin GI 275 attitude indicator (AI/ADI) as a backup.

• READ MORE: The Aviation of Things

I recently met with Mercer at Gardner Lowe to ask some questions about the selection process when speccing out this job:

FLYING Magazine (FM): Why do this upgrade now?

Stephen Mercer (SM): The family decided it was necessary to upgrade the avionics panel for safety purposes.

FM: I agree with the safety-first mantra. How did this maintenance action make your Saratoga safer?

SM: You are familiar with the redundancy as it applies to aviation?

FM: Yes, redundancy is a system designed with duplicate components. Therefore, if one fails, you have another as a backup.

SM: Correct. With (my father-in-law) still learning, I did not want to cross the cockpit to utilize the panel. The dual instruments ensure that I can concentrate on the task at hand. I also like to keep my eyes on the  traffic pattern, not staring down at an iPad. Also, keeping the autopilot on all the time reduces the stall threat.

• READ MORE: The Daily Life of a Repair Station

As part of the maintenance process, Mercer’s team removed analog gauges and the vacuum pump. When I asked him if there was anything else he was excited about, he said, “Yes, enhanced engine monitoring.”

Annual Inspection Time

As anyone will tell you, aircraft maintenance takes time. If you think about it, any project can be full of surprises, even for the best of us. When I go to my local Ace Hardware to get hinges for my wife’s kitchen cabinet project, I buy extra. You never know. When she asks how long it’s going to take, I am evasive about the time. I learned that lesson a long time ago.

Mercer knew this going in. While his Saratoga was down for the avionics panel upgrade, he decided to have the annual inspection accomplished as well. Lane Mitchell of Mitchell Aviation Services was only happy to oblige. Based there at Gardner Lowe Aviation, Mitchell handles most of the airframe- and powerplant-related actions for aircraft in the hangar.

Seizing the opportunity to conduct the annual while the team installed the new avionics panel saved Mercer time and resources down the road. Because Gardner Lowe partners with Mitchell Aviation, the coordination is built in. Too often, owner-operators will try to parcel out the work to the lowest bidder. This can cause confusion, delays, and ultimately costs more.

Trust is a huge component of aircraft maintenance. There are no shortcuts, but there are ways to save. Trying to buy parts off the internet and have your A&P install them is not one. If something goes wrong, who is going to stand good for it? Certainly not eBay.

The post There’s No Price on Safety appeared first on FLYING Magazine.