Winter Airtanker Maintenance is Very Important

Direct link to Bridger Aerospace on Facebook, posted on October 5th.

As I continue to write this blog and try to focus on all that is involved in flying airtankers and helicopters on wildfires, I know how important winter maintenance is to keeping airtankers and helicopters in safe flying condition. Maintenance is important for all aircraft and maintenance schedules should be adhered to. The importance of following aircraft maintenance schedules was driven home to me when I went on scenic rides several years ago. I hope that you can see the October 5th Facebook post from Bridger Aerospace that I embedded. If you cannot I hope that you can find Bridger Aerospace on Facebook and look for their October 5th post.

Aircraft Maintenace is Important

Direct link to May 24th post on Facebook by Coulson Aviation

Maintenance of aircraft -- firefighting aircraft, commercial aircraft and general aviation aircraft -- is very important to be sure that aircraft are safe to fly. Operators of aircraft including Coulson follow a maintenance schedule for their aircraft, some maintenance is more routine and other maintenance involves inspecting the whole aircraft. Aircraft parts may be replaced as needed in order to keep the aircraft safe to fly. I applaud the Aviation Maintenance Technicians who maintain aircraft for Coulson and other aircraft operators.

Winter Maintenance of Firefighting Aircraft is Important

Direct link to July 2025 video from Airborne Firefighters on YouTube

I was looking around for something related to aerial firefighting to share with you today, when I came across the above video from Airborne Firefighters dated July 12, 2025. This video provides a behind the scene look at CAL FIRE's winter maintenance. While specific to the winter maintenance ofCAL FIRE's aircraft, this video gave me a glimpse into what might happen in the winter maintenance of any firefighting aircraft. I learned something and perhaps some of you will also learn something as well. Enjoy!

As an aviation enthusiast I know the importance of regular maintenance of any type of aircraft to keep the aircraft, pilots, and any passengers safe. In addition, if an aircraft crashes their is always the risk of damage to infrastructure on the ground, including buildings as well as injuries or death of people on the ground. From time to time I have shared about aircraft maintenance and inspections.

2024 Wildfire Season: Air Tanker Maintenace Continues

As April began, Coulson Aviation and Neptune Aviation and continued spring maintenance of their air tankers as the following embedded (posts with photos) from their Facebook page show. I expect that other air tanker and helicopter operators who fly wildfires are also conducting spring maintenance that are not mentioned here.

Neptune Aviation Services

Coulson Aviation

2024 Wildfire Season: Air Tanker Spring maintenance

When I was first learning about general aviation 13 years ago, and going on scenic rides, one of my key takeways was the importance of regular maintenance of aircraft. As I recall, the maintenance of the small planes that I was familiar was guided and mandated by FAA requirements with different maintenance and inspections being done at regular intervals  (hours flown) and signed of by an Airframe and PowerTrain Mechanic. More complicated and thorough inspections and maintenance were called for at longer intervals. But things like oil changes and the like were done at shorted intervals. But I am not writing about maintenance of general aviation airplanes and if I were, I would have to brush up on the requirements.

I am writing about spring maintenance done by contractors on contract with the US Forest Service, or at least two contractors, Coulson and Neptune. I am not privy to what is done in a spring maintenance, nor am I privy to the more routine maintenance that is done through the period when the tanker is on contract. Also, I am not ignoring helicopters on contract with various agencies that fly fires but I have no information on maintenance by helicopter contractors. I am certain that the contractors maintain their helicopters and may also engage in spring maintenance.

I did recently note on Facebook, two companies with US Forest Service Contracts making a post about spring maintenance. What is important is that spring maintenance occurs and while I don't know specific maintenance and inspection procedures, I want to share these two posts about taking time for winter/spring maintenance before individual tankers go on contract.

Coulson Aviation

Neptune Aviation

Aircraft Working Wildfires: Off Season Maintenance

When aircraft working wildfires such as airtankers, helicopters, and lead planes, etc. are either finished for the season or are between contracts (see for example my October 16th post on Coulson T-132 having maintenance before going to Australia), major maintenance takes place. To the best of my knowledge, the time table (usually hours flown) and what types of maintenance tasks take place at different times is set forth in the United States by FAA requirements and perhaps also stated in the contracts, some items will be specific to the aircraft model. While I do not know what happens during what I am referring to as major aircraft maintenance, I know that there is a pretty comprehensive list covering all the systems on an aircraft that have to inspected, replaced, etc. during major maintenance. 

Some aircraft maintenance happens more often, what I will call for these purposes routine maintenance. I do not know the nature of routine maintenance of aircraft working wildfires, but from what I know of small aircraft, minor maintenance includes but not limited to oil, filters are performed more often and in the world of aircraft working wildfires may be done at night but I am not quite certain. And of course, if an aircraft as an issue that arose requiring maintenance, that aircraft will be pulled off the line until the issue is addressed by the maintenance crews.

I must acknowledge that I am not an expert or otherwise in the know about the specifics of aircraft maintenance That being said I want to speak to the importance of the maintenance of all aircraft including aircraft used to fight wildfires to keep the aircraft safe/ During the off season, so to speak, the contractors supplying aircraft for working wildfires are not sitting around twiddling their thumbs, they are busy performing maintenance of their aircraft.

The Facebook post that I am embedding below is from AeroFlite Aerial Firefighting who maintains a fleet of CL-415 amphibious aircraft, and Avro RJ85 AT and Dash 400 AT aircraft. You will see some photos of their winter maintenance of their CL-415 aircraft receiving maintenance.

Aircraft engaging in aerial firefighting: maintenance, winter and otherwise

 I know that regular maintenance of aircraft is important, including but not limited to aircraft engaged in aerial wildland firefighting. Maintenance in the United States and in other countries does not happen on a haphazard schedule but is on a schedule partly dependent on how many take-offs and landings (one  take-off and landing is called a cycle) the aircraft has flown. However, I believe that there is more to the frequency of maintenance than just cycles flown. As I am not airframe and powertrain mechanic nor do I work for a company flying aircraft on wildland fires so I am not in a position to speak knowledgeable about the specifics of aircraft maintenance. But I can say that I know enough to know how important it is that the maintenance be performed on schedule, rigorously and thoroughly. 

In June 2021, Coulson's Australia Division shared a short video on their Facebook page describing winter maintenance of their aircraft based in Australia. While a different country, they do provide an overview of the maintenance performed during the Australian winter. I shared this video (under two minutes) on my blog in June 2021

While wildfire season is almost year round in some parts of the western United States, most but not all aircraft flying fires are on some kind of contract with the federal or a state government agency. This means that they are off contract for a part of the years and it is during this time when maintenance requiring a longer time to perform is done. Earlier this year, March 4, 2022 to be exact, Aerial Fire had a nice article on Neptune Aviation Servces' Winter Maintenance Assures Year-Round Readiness, this article may be found on this page from Aerial Fire. It is a very good article (with pictures), I appreciated the article and am a little more knowledgeable about maintaining an airtanker. Clifford Lynn, Neptune's Director of Maintenance. I encourage you to take a few moments to read this article. According to Mr. Lynn:

Neptune’s maintenance team designed the FAA-approved airframe inspection program (AIP), which builds upon BAE Systems’ OEM maintenance protocol for the aircraft as a commercial jet.

As he described it, every year, each aircraft gets an A Check, a C phase check, and a D phase check.  Every two years the C check is completed and every four years the D check is completed.  These C and D phase checks include a corrosion control and structural inspection program.  The airframe, retardant tanks, and the engines are what the winter maintenance primarily targets.

“We schedule our winter maintenance, so anything due in the next 12 months, 400 hours, and/or 600 cycles is complied with during the heavy (C and D) check,” said Lynn.  “To date, the nine air tankers are averaging 300 cycles per year.  Some line replaceable units (LRU) are not changed during the checks if they have significant time on them remaining.”

Lynn added that for most life-limited components such as the landing gear, oxygen, and fire bottles, Neptune follows the OEM maintenance protocol.

Because of the stressful environment in which the aircraft fly, some components have to be inspected at more frequent intervals, he noted.  “Also, we have some additional tank-related inspections.” (obtained on November 7, 2022 from https://aerialfiremag.com/2022/03/04/neptune-aviation-services-winter-maintenance-assures-year-round-readiness/

I am sure that other aircraft companies perform appropriate maintenance on all their aircraft including but not limited to aircraft flying fires in some capacity. Thanks to all who flew fires this year helping the crews on the ground put out the wildfires.

About winter airtanker maintenance from, Coulson's Australia Division

 I know enough about aviation to know how important regular scheduled aircraft maintenance is. Airtankers and Helicopters are no exception. Wether it be scheduled maintenance that pulls the aircraft out of service for a day or two or longer maintenance that is done during the off season these maintenance procedures and the timing there of are usually mandated by the governing aviation association. If something goes wrong during the season, this is noted and the aircraft is taken out of service until it is fixed. I am not intending, nor am I qualified to write in any detail about aircraft maintenance. 

It is winter in the southern hemisphere and time for winter aircraft maintenance. I did enjoy this video from the NSW Rural Fire Service in Australia about the winter maintenance that Coulson is performing on their aircraft. While this video is about airtankers flying in Australia, I believe that the basic principals are the same as those done in the United States.

The video is a couple of minutes long with captions. Enjoy.

A very brief introduction to winter maintenance

Regular maintenance is important to any aircraft operation whether it be the owner of small plane, a tour operation, charter operation, airline. military, rescue or aerial firefighting. 

Aircraft used in aerial firefighting may only be active for the period when they are paid by the contracting agency to be available for aerial firefighting duties. Sometimes these aircraft are only used part of the year. At other times, and depending on the business the operator is in and the type of aircraft they fly, the contractor will be flying their aircraft through out the year.

As many of you know, when an aircraft hasn't been flown in awhile, it doesn't come out of the hanger ready to fly, maintenance is performed. Many operators have what is sometimes known as a winter maintenance period when maintenance that requires a lot of time is performed by their maintenance staff. Of course, aircraft are maintained year round, not just in the winter or off season. Maintenance checks are preformed through out the year. I am in the process of putting together some articles focusing on winter maintenance. I am not quite sure when these articles will be ready, could be at least a couple of weeks, if not longer.

In the meantime here is an article that peaked my interest in winter maintenance, a press release from the American Helicopter Services and Aerial Firefighting Association that may be found here. You will learn a little about winter maintenance performed by Columbia Helicopters and Neptune Aviation in what has turned out to be an earlier fire season out west.

Part 8 of 9: Cessna Annual 172P - finishing up the annual

Final installment in this series on May 18, my reflections

Part 6 of 9: Cessna Annual 172P - magneto services

Blogger had an outage on May 12 and I have (temporarily) lost the posts that I made on Wed. May 11 including "part 6 of 9: Cessna Annual 172P - magneto services." I am reposting this now, out of order. Thanks for your patience.

I will write about the magneto service here, and will continue discussing magnetos when I write about the engine and propeller service in part 7 of 9. The  three photos below show the magneto service.

I watched Brent do the magneto service over the course of about 30 to 60 minutes (I think). I enjoyed watching him work. Unfortunately, I spent most of the time listening, and did not take a lot of notes. Sometimes it is better to just watch and listen. so, I regret that I don’t have more to say about this service. Perhaps I’ll have an opportunity to watch him do another magneto inspection in the future.

However, while Brent was talking, I did make some notes about what the magneto does. Single-engine planes such as the Cessna 172P have two magnetos. Simply, they are self contained ignition systems. One of the items on the pre-takeoff check is checking that both magnetos are operating on their own. If one of the magnetos doesn't work, you are grounded. While you only need one magneto for flight, you always want to go up with two working magnetos. You do not want to take off with only one working magneto and risk having that one working magneto fail in flight. It may not be a good outcome.

Part 7 of 9: Cessna Annual 172P - magnetos (cont), propeller, and engine services

I was taking some notes as Brent showed me around the engine of this 172P. The Lycoming engine of this 172P is a horizontally opposed engine. One magneto is wired to the bottom left side and the top right side of the engine. The other magneto is wired to the top left and the bottom right side of the engine. In the photo below, you see a close up of this wiring on one side of the Lycoming engine.

For those of you who are interested, a magneto works by means of a rotating magnet. A charge is created a that eventually travels through the distributer cap to a wiring harness to the spark plug on the engine.

The bottom spark plugs are disconnected during the inspection so the propeller can be safely turned. While you can start a Cessna 172P by turning a key inside the cockpit, you can also start the plane by turning the propeller by hand (known as hand propping). So, disconnecting the bottom spark plugs is a safety measure. There is no risk that the 172P will start accidentally. See the two pictures below.

The engine service includes but is not limited to servicing the alternator belt, inspecting the engine controls, and inspecting the engine.

After the propeller is inspected it is polished. In the photo below you see John polishing the propeller.

Next up on Monday, May 16: Finishing up the annual.

Part 5 of 9: Cessna Annual 172P - Inspection

There are many inspection portals in aircraft, including the Cessna 172P, where the Airframe and Powerplant Mechanic with Inspection Authorization can inspect what is “underneath”. Mostly various wires and cables. In this series of photos, you will several such portals, finishing up with a couple of shots of Brent performing this phase of the annual inspection.

Next up: magneto service

Part 4 of 9: Cessna Annual 172P - Battery Service

Unlike the battery in my car, I learned that the battery in the Cessna 172P is not a sealed unit. That is the battery in the Cessna 172 can be opened up to add distilled water. In the photo below, the battery is being charged. Distilled water has already been added to the battery, if necessary, prior to being charged.

Part 3 of 8: Cessna Annual 172P - Emergency Locator Transmitter Service

I watched the service of the Emergency Locator Transmitter (ELT). I learned that the batteries are replaced after 1 hour of cumulative use or after 50% of their service life is expired. The ELT is designed to activate and transmit a signal after being subject to forces generated in a crash. I understand that the ELT is in different locations in different airplanes.

Next up: battery service

Part 2 of 8: Cessna Annual 172P - landing gear, wheels, and brake service

My first afternoon at State Line I watched Brent’s apprentice, John, work on the landing gear and brakes. John works under the direction of Brent. Brent is a Airframe and Powerplant Mechanic with Inspection Authorization and is the one who “signs off” on the annual inspection. John cleans the landing gear with mineral spirits in the first two photos. The wheel bearing is cleaned with mineral spirits in a parts cleaning machine in the third photo.

In the first photo below you see the new brake pad (L) and the old brake pad (R). The brake calipers are shown in the next three photos.

Landing gear wheel back in place.

Next up: emergency locator transmitter service

Part 1 of 8: Introduction to Annual Service of Cessna 172P

Late last December I spent two half-days and one full day at State Line Aviation on the field of Alexandria Airport (N85) watching one of N85's Cessna 172P trainers, (I refer to her as “Red”), get her annual maintenance. I had a great time and I learned a lot. As I watched the inspection and had the opportunity to ask Brent or his apprentice questions, I took notes on what I saw and heard. Over the next few articles, I am going to take you on a photo tour of my time watching the annual along with some commentary about what I learned. This is not meant to be a chronicle of an annual maintenance from beginning to end. Rather, I suppose you can say that I am touching on certain highlights of this annual. This is the first of eight articles that I will post over the next 2 to 3 weeks.

I want to start with the aviation mechanic's creed that is posted on the wall of the State Line Aviation. Please take a moment to read it. When I was talking to the owner, Brent, we got talking about what makes aviation mechanic's tick. He took me out and showed me the creed. I stood there, spending a few minutes reading the creed and letting the words soak in. As I watched Brent and his apprentice, John, work on Red over the course of the next couple of days, I saw the creed in action.

See the image below for a copy of the 100 hour/annual inspection checklist. In the case of the 172P, this is her annual inspection.

This is Red with her engine cover taken off, this a side view of the engine compartment. Having done a couple of pre-flight inspections that included checking the oil and checking one of the belts, it was something special to get my first glimpse at what is under the hood (or cowling). What is under the hood and the propeller (out of the picture) provides the thrust. Thrust along with the lift provided by the wings are two of the four forces of flight that act on an aircraft in flight. The other two forces of flight are drag and weight. Drag works in opposition to thrust and weight (gravity) works in opposition to lift.

Remembering the days when my car had a carburetor, I wanted a photo of Red’s carburetor.

One of the things on the done in the annual is changing the oil filter, note the date on the filter. That is the date the new filter was installed. The number 3998.4 is, according to Brent, the tach time (akin to an odometer in an automobile) found on the bottom of the tachometer. The tachometer records the revolutions per minute (RPM) of the engine crankshaft. In the 172P, the propeller is attached to the engine crankshaft, so the tachometer records both engine and propeller RPM. Tach time is the total number of hours that the engine has run.

Next up: landing gear, wheels, and brake service

Aircraft tire pressure and hydroplaning

A couple of weeks ago, a friend of mine sent me an article on the importance of properly inflated aircraft tires, it may be found here. This got me thinking about the importance of properly inflated aircraft tires. While the article that my friend sent me talks about improperly inflated tires as a cause of the crash of a Lear Jet and a commercial airline in the Middle East, it is important for all aircraft, from my Cessna trainer to Lear Jets to airtankers to Jumbo jets, to have properly inflated tires. I am going to talk a little about what I am learning about the importance of properly inflated tires on single-engine aircraft such as the Cessna 172 that I take scenic rides in.

I have recently been working on pre-flight inspections of an aircraft with the pilots that take me on scenic rides. The tires are one of a number of items on our pre-flight checklist. So, I told him about the article that my friend sent me. He told me that he thought that the proper tire pressure on the Cessna 172P was about 30 pounds per square inch (psi). He went on to remind me that we had talked about the relationship between tire pressure and hydroplaning and aircraft speed in ground school.

Automobiles can hyrdoplane, as can aircraft. Not a situation you want to be in either vehicle. When you hydroplane, for example on a wet runway, your tire loses contact with the ground and you lose control of the aircraft.

Take a moment and go here and watch a two minute video on NASA's work on hyrdoplaning. You will see a formula in the video:

9 * (the square root of the tire pressure) = the speed in knots at which you will begin to hydroplane.

According to the above formula, a tire with pressure of 30 psi will start to hydroplane at about 49 kts.

I learned a quick and dirty version of this formula in ground school:

(tire pressure &#247 by 6) * 9 equals the speed that aircraft will start hydroplaning.

Using the quick and dirty formula, the tire will start hydroplaning at 45 kts. I like that the number is a little lower than the 49 kts in the NASA video because you have a target safe landing speed that is a little lower. Perhaps providing a safety margin? But it is an easy formula for to remember, and you can do the calculation in your head (or on the pad of paper on your knee board).

The key here is that the lower the tire pressure, the lower is the speed that the aircraft will start hydroplaning. Using the quick and dirty formula, the number comes out to be 42 knots. If you land at 45 knots with tires at 28 psi on a wet runway you will hydroplane.

I don't know about you, but that short conversation with the pilot made an impression on me. I"ll leave it to the folk at NASA to do their tests and research on hydroplaning aircraft tires.

Note - apologies for not using proper mathematical notation for the square root symbol. If I can figure out how to include a square root symbol in html code that will show up here, I'll revise the article later.

Aircraft maintenance logs

My point in writing this short article about aircraft maintenance logs is to not to go into any kind of detail of on keeping the FAA required aircraft maintenance logs. Rather it is to write about something that I had never given much thought to -- aircraft maintenance logs -- until about one year ago.

At some point after I'd been writing about the world of aerial wildland firefighting for several months I had a vague awareness that detailed maintenance logs were kept for all (or most) aircraft. Then I went to ground school last winter and to learn various FAA regulations, including but not limited to the regulations for who can do what type of maintenance on an aircraft, who (airframe and power plant mechanics or airframe and power plant mechanics with inspection authorization) can do what type of inspection, and that maintenance and inspections are logged in the appropriate maintenance log(s).  Keeping maintenance logs for a given aircraft is not an option, it is required under FAA regulations. Furthermore, the logbook(s) are transferred when the airplane is sold.

It is not just one or two maintenance log books, but multiple logbooks. There is an airframe maintenance logbook. And there is one logbook each for each engine and propeller. So, the (single-engine) Cessna trainer that I go flying in has three logbooks. A tanker with four engines with four propellers (such as a P-3) will have four engine logbooks and four propeller logbooks.

FAA regulations specify certain preventive maintenance that can be performed by the pilot/owner. After the pilot completes the preventive maintenance item, s/he notes the repair in the appropriate logbook and then signs and dates the logbook. Likewise, maintenance completed by an airframe and power plant (A&P )mechanic  is logged in the appropriate log book and then signed and dated by the A&P mechanic. Inspections are also logged in the appropriate logbook by the A&P mechanic (with inspection authorization as appropriate) completing the inspections.

The FAA does not require that the maintenance logs be kept in the airplane. It is a legal document that must be available to the FAA, NTSB and other agencies within a specified time period when requested. It is not a good thing for the logbooks to be lost and/or destroyed. For these reasons the maintenance logbooks are usually kept in a safe place away from the airplane.

For those of you who never knew about maintenance logs until you read this article, perhaps the next time you see an aircraft, no matter how small (a Cessna trainer) or how large (a jet operated by an airline), you will know that there are multiple maintenance logs for that aircraft.

Progressive Inspections (2 of 2) -- A brief look at what happens in progressives

What might happen in a progressive inspection program? I don't have access to any current progressive inspection program documents, but thanks to discussions with friends who are airframe and power plant mechanics who have worked on progressive inspections, I have an idea of how progressives work.

In a typical FAA approved progressive program, the progressive is based on three or four operations that recycle after a certain number of hours. So lets say there is an approved progressive program , e.g. for a hypothetical single-engine fixed wing aircraft, has four operations occurring at 50 hour intervals, recycling after 200 hours (of flight time). Further, the progressive inspections must be completed within a twelve month period.

Lets say that the last twelve month period started on January 31, 2010 and the aircraft has only flown 140 hours to date with progressive inspection operations one and two already completed. Operations three and four must be completed by January 31, 2011.

There will be a list of specific items that have to be inspected in each operation. Each operation is likely to focus on detailed inspections of one or two components with routine inspections of the other components. For example operation # 1 may  have detailed inspection items for the landing gear and wings with routine inspection items for the rest of the aircraft (cabin, fuselage, engine, propeller, and empennage).

In my discussion of progressive inspections, I would be remiss if I did not mention that the FAA regulations mention that life-limited parts have to be replaced before the end of their life. I suspect, that life-limited parts will be replaced during progressive inspections. I also suspect that the replacement of life-limited parts is an important component of maintenance and inspection programs in the tanker business, whether they be progressive inspections or some other type of FAA approved inspection program.

As I have learned more about how progressive inspections work, I appreciate that the world of aircraft maintenance and inspections, including but not limited to progressives) is often complicated. A progressive inspection program in the tanker business is going to be much more involved and a lot more time consuming than a progressive for a fixed-wing single engine aircraft with non-retractable landing gear. Nothing is simple in the tanker business.

This ends my two-part series on progressive inspections. Perhaps I'll revisit progressives again in later articles. For now, I am moving on. In my next article, I'll write a little about maintenance and inspection logs.