On 14-May-25, my Airflow Systems 2007X oil cooler failed in flight with only 75.9 hours on the cooler. In just a few minutes of flight, it ejected almost 60% of the engine's oil, leaving me about 2.25 quarts in the sump at shutdown. Thankfully the failure happened just as I was about to enter the downwind for landing at my home drome. Below shows where the Airflow Systems 2007X cooler failed, just above the red line.
That seam opened up right at the intake side of the oil cooler. The oil sprayed against the firewall and the airflow carried the oil out the right exhaust exit of the cowl, coating the belly of the aircraft with oil, as shown below. You can see how the oil almost entirely favored collecting on the right side of the airfame. And yes, it was a mess to clean up the airframe. Everything under the cowl was remarkably entirely free of oil save for a little splash on the firewall behind the cooler where the spray departed the failed 2007X cooler. In fact, it was difficult for me to find the location of the failure until I pulled the cooler out of the plane and pressurized it.
The incident in flight manifested as a drop of several PSI of OilP and a momentary increase in prop RPM to 2710. Both of which my GRT EFIS caught and annunciated by voice.
Below shows the OilP in flight. The x-axis is minutes since engine start. The red arrow indicates when the OilP became unstable, most certainly indicating when the Airflow Systems 2007X oil cooler failed. OilP goes to zero on the graph since the engine was shutdown with the EFIS still on.
Why do I have the 2007X rather than the stock 2006X? I fly behind an IO-390-EXP119. Read here to learn why high summer OilT led me to install a larger cooler.
Turns out that the 2006X has a service bulletin (link here on their website and link here on Vans' website). Airflow Systems' document states that a specific swath of serial numbers had a potential manufacturing defect that could lead to a leak from the vanes or core area of the cooler. Whereas Vans' document also reiterates the need to use a "double wrench" method to tighten fittings on the cooler. Curiously, Airflow Systems didn't issue a service bulletin for their other models. I point that out since Airflow Systems uses the stacked "drawn cup" oil cooler design. I'd be interested to learn why the issue they identified was limited to the 2006X.
There are several reports of the 2006X failing on RV-14s (example here). In fact, Van's has an online form seeking to collect that information. In my case, I did use the double wrench method and the intake hose was constrained by Adel clamps to the engine mount where the outflow hose was constrained by wire ties. My prop was not balanced during the time the failed 2007X oil cooler was installed.
Below, I show Figure 2 from plans page 49-13 that illustrates how the oil intake hose is routed into the cooler (traced with a red line). You can see that it enters the cooler with a 90 degree fitting and is generally unconstrained over a significant length. This may be a source of unwanted vibration being transmitted into the cooler. I wonder why they didn't bring that hose in directly by going behind the engine mount. Maybe it was to reduce the parts count for the airframe (relative to tail dragger vs. nose dragger) or to allow the hose to have enough slack to accommodate movement of the engine during startup and shutdown.
For what became my failed Airflow Systems 2007X cooler, I took a similar route and constrained the hose to the engine mount with a pair of Adels (the latter of which is circled). Perhaps the hose routing caused some torquing of the fitting and transmitted unwanted vibration into the cooler. The fittings were clocked slightly differently than for the stock 2006X since the failed 2007X is slightly longer so the hoses are slightly too long.
I reached out to Airflow Systems to have a conversation to help me understand why this happened, whether it was my fault (hey, whatever skills I have, it isn't in aircraft development), a kit design issue (e.g., hose routing problem) or a manufacturing issue. Suffice it is to say, my interaction with the Airflow Systems rep on 21-May-25 was very disappointing. Those details aside, they did said they'd try to get me an RMA to return it to the manufacturer (which is in PA, not CA where the company is located) for analysis. Despite some follow-ups on my part, I'm simply told that they are "working on it" and thus I haven't received an RMA (as of 1-Aug-25). This indicates to me that they aren't serious about understanding why one of their products failed. I was also told that my cooler is "way outside of warranty" (having purchased it ~18 months before and installed it just short of a year ago) and despite that, they would sell me a cooler "at cost". Replacing the cooler with the same model (even at no cost) was not a satisfactory remedy to me since the root cause of the failure remained unknown. Getting the cooler back to the manufacturer for analysis was important to me.
My oil cooler details:
- Manufacturer: Airflow Systems
- Model: 2007X
- Serial number: E22-15691-09
- Purchased: 7-Dec-23
- Installed: 29-May-24
- Failure:
- Hours of flight: 75.9
- Date: 17-May-25
The inadequate customer service found me having little confidence in Airflow Systems. At that point, I sought to find other alternatives.
It's worth reading this great Kitplanes article explaining how oil coolers are made.
Airflow Systems uses what seems to be the more fragile, less expensive
and stackable "drawn cup" design whereas Aero-Classics has models using
the more stout and more expensive "bar and plate" design in many of the PMA'd coolers.
I reached out to Aero Classics. I had a refreshingly helpful conversation with them and was put in touch with one of their engineers. This catalyzed a wonderful dialog about their oil coolers' performance and what might be a good alternative for me (including a discussion with heat rejection vs. airflow plots). I came away from the interaction impressed with their drive, knowledge and willingness to help. They even provided me a 3D CAD model of the cooler (below) we selected, so that I could verify my tray and duct design for the new setup! It was indeed a night-and-day difference when compared with the uninspiring interaction with Airflow Systems.
Following that conversation, we together thought that the HE 8001652 model (the "HE" indicates high efficiency) would be a good alternative for me.
It's a 13-row "bar and plate" design, as shown below. In mid June 2025 at Aircraft Spruce, the 2007X costs $973 whereas the 8001652 costs $1,295, so almost exactly 1/3rd more. Even though the 8001652 has two fewer rows than the failed 2007X, the dimensions of the rows and fin densities are different than that of the failed 2007X, so comparing the coolers on the basis of the number of rows is inadequate. Additionally, the engineer felt that the 8001652 has a better sealing interface that would mitigate air leakage around the core. I will defer to their expertise since whatever expertise I may purport to have (surely, dubious claims on my part), it isn't that.
Quick calculations showing the cross-sectional areas and core volumes of the 2006X, failed 2007X and the proposed 8001652 are below. Whilst the cross-sectional area of the 8001652 is about 10% greater than that of the failed 2007X, the volume of the core is actually 2.3% less since the core width is 3.2" rather than 3.62"
Yet, it turns out that this cooler was horribly inadequate. You can read about the installation of this cooler in my airframe and the cooler that I ultimately chose to replace my failed 2007X.
