The Corrosive Death of a Cessna 210 Engine

Annual Inspection Time

​Every aircraft owner knows the drill: it's annual inspection time, a mix of routine yet hopeful checks to ensure our planes are in tip-top shape. Our Cessna 210, a reliable performer, entered this inspection with us feeling confident. After all, we'd been diligent with maintenance, and the engine was running as smooth as ever.

However, things didn’t quite go as planned. One cylinder came up a bit shy on the compression test. Turning to Continental’s SB03-3 bulletin for guidance, we flew it for another hour, hoping for a pressure change that didn’t materialize.  So, it was time to remove and inspect the cylinder. With hindsight being 20/20, perhaps a ring wash should have been tried as well.
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The real curveball came after the cylinder was removed. Hidden from routine view, our mechanic identified a subtle flaw on one of the cam lobes. This small gouge, while easy to overlook, did have a depth significant enough to snag a metal pick. Those versed in aircraft maintenance might recognize this as a warning threshold, per the indicators in Service Information Directive SID05-1. An email exchange later, Continental verified that the cam needed to be replaced. Thus began our unexpected journey into a deeper teardown.

Damaged Camshaft

Unsettling to Downright Frustrating

​We entrusted our engine to SkyBoss Aviation, a reputable aircraft engine overhaul service facility just outside of Tulsa, OK. Bill Wagner, the seasoned expert over at SkyBoss, took on the task of disassembling our engine. But not long after, he rang us with news that got our attention.

Firstly, Bill described the engine's interior akin to a swamp at some point in its lifetime. Internal corrosion was everywhere, rendering many components unfit for service. A complete engine overhaul was the only way forward.

"That Crankcase is a Swamp" - SkyBoss Aviation

But then came the kicker. The crankshaft bearings were out of stock. And if that wasn’t enough, approval paperwork for a bearing manufacturing change had yet to be approved by the FAA, effectively putting an indefinite hold on their availability.
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What we initially hoped would be a few months' delay extended far longer than we ever anticipated, clocking in at a frustrating year-plus of waiting and a staggering invoice of $40,603.

Battling the Silent Killer: Engine Corrosion

​The extent of our engine's corrosion was shocking. With part after part deemed irreparable, we grappled with not only the mounting expenses but also significant downtime. Furthermore, over a year’s worth of adventures in the 210 were lost.  Not to mention the currency and proficiency of an owner-pilot that relied exclusively on this particular aircraft.

This ordeal made us hyper-aware of engine corrosion, prompting us to introduce engine dehydrators across our fleet of five personal and corporately owned aircraft. 

We tested several market-available engine dehumidifiers but found ourselves questioning their efficacy.
​It was disconcerting to often even see water collected in the tube meant to aerate the engine – a clear indication that something wasn't right!

With the drive to understand the situation better, we repurposed small dataloggers (manufactured by us for a different venture) to fit snugly into spark plug holes and crankcase vents. After installing the dehydrators, these sensors began to record the humidity levels inside of our engines and confirmed the dehydration devices' ineffectiveness.

One of the Sparkplug Loggers Used for Rotax 912 Testing

For example, our month-long logging exercise for the Long-EZ engine yielded revealing results. The dehydrator initially seemed promising, maintaining a dry environment for about a day. But soon after, the internal humidity levels surged, often breaching the 40% and 50% thresholds. Clearly, this solution wasn't cutting it. And other dehydration methods required constant user intervention which made them impractical. It was off to the drawing board to find a more effective, reliable solution to this problem.

Birth of the DryBot - The Ultimate Guardian Against Engine Corrosion

Our search for a solution finally hit a wall. We felt that the market simply didn’t offer a system that was maintenance free and effective in keeping the internal engine humidity below the crucial corrosion-inducing level of 40%. We, and the rest of the aviation industry, needed a reliable solution.

Harnessing our passion for aviation and our team of in-house engineers, we set out to design the solution the aviation world was missing: the DryBot. Envisioned as the gold standard of engine dehydrators, DryBot would promise not just reliability, but also minimal upkeep. Its unique self-monitoring features would ensure it's always operating correctly, giving aircraft owners that much-needed peace of mind.
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In essence, with DryBot, we didn’t just aim to solve our own corrosion problems; we wanted to offer the broader aviation community a trustworthy guardian against the silent but menacing threat of engine corrosion and avoidable early overhauls.

Inside the DryBot: A Deep Dive into its Innovative Design

The DryBot, our answer to the aviation industry's engine corrosion challenge, is a culmination of extensive research, rigorous testing, and our own frustrating experiences with other systems. Let's unpack what makes DryBot different:


1 - Reliable Dehydration 
Our search for the perfect dry air source took us through various technologies, from refrigeration systems to desiccant media. Ultimately, desiccant beds emerged as the most dependable method, consistently delivering the dry air needed to prevent engine corrosion.

2 - Truly Maintenance-Free
Desiccant-based dehydrators do come with a catch: over time, the desiccant gets loaded with water and needs either replacement or regeneration. Our solution? A specially designed airflow circuit, complete with an integrated regeneration heater and alternate valve actuated airflow path used to expel water. This approach regenerates the desiccant as and when required, eliminating the need for manual intervention.

3 - Smart Self-Monitoring
If there's one thing we've learned, it's the importance of reliability. With many systems, you're left wondering if they're doing their job.  Is the air dry?  Is the air flowing? This isn’t a problem with the DryBot. The DryBot is equipped with a suite of internal sensors that continuously monitor airflow and humidity output. And for a quick status check? A straightforward Green/Red light system flags if everything's running smoothly or if, say, there's a kinked hose blocking flow.
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4 - Ultimate Trustworthiness
​At its core, DryBot's mission is simple: keep the air dry and keep it flowing. But we didn't stop there. We incorporated an inline particle filter, ensuring that not only is the air dry, but it's also clean. Furthermore, safety is paramount, so we added a mechanical thermal thermostat to serve as a backup for controlling heater temperatures. Paired with our heater power measurement circuitry, these sensors work to detect and flag any heater faults.

DryBot, the Automated Engine Dehydrator

Validating the DryBot: Real-World Data 

Our journey with the DryBot wasn't just about engineering a solution, but also ensuring that it was truly effective. That assurance lies in the real-world data our humidity dataloggers captured.

In the initial phase, without the DryBot, the data displayed the engine's internal humidity levels mimicking ambient levels but slightly lagging due to the thermal mass of the engine and engine air leakage.
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Once the DryBot was initiated on day 2, the change was almost immediate. Within minutes, the internal humidity plummeted to 0%. Detecting a rise in output humidity, the DryBot automatically triggered a regeneration cycle of the desiccant bed roughly once per day. While regenerating, the DryBot  heats the desiccant bed and purges its moisture, releasing the absorbed water through a discreet opening at its base. Our data vividly illustrates this process: during these purging episodes, the internal humidity saw only a modest uptick, thereby keeping the internal engine humidity between 0% and 20% RH. This is well below the 40% threshold where steel exhibits substantial rates of corrosion.

In Conclusion:

​The journey of developing and validating the DryBot has been a testament to the importance of innovation in aviation maintenance. It's not just about a piece of technology, but the peace of mind it brings to aircraft owners, knowing their engines are safeguarded. In an industry where precision and reliability are paramount, the DryBot stands as a genuine contribution to preserving the longevity and safety of our aircraft.

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