First Word: April 2013

OXYFLY Revisited

Another purpose of this magazine is to encourage product improvement. If we give a bad review to a product and the manufacturer subsequently makes it better, we’ll review it again. If it is better, we’ll say so, loud and clear. If not, we’ll say that as well.


It’s also important to recognize that a bad review may be the result of a bias, a one-off problem with a particular unit or just a bad day all around. Because of that, I followed the practice of this magazine and sent the Durr Technik representative an outline of the shortcomings I was going to report and asked if his company wanted to comment or rebut my opinions.

Durr Technik did reply, thoughtfully and in detail. As a result, this column is going to be a little longer than usual this month so that I can put in as much of the Durr Technik response itself as space will allow—it was too long to run in our Letters section and still run other reader letters.

I’m also reiterating my support for the oxygen concentrator concept because it provides oxygen so long as the device is getting electricity and I’ve had problems getting oxygen bottles refilled. I think it’s also important to have an effectively unlimited supply of oxygen because of what I learned when researching the pulse oximeter article last month—pilots are at risk of cognitive impairment at much lower altitudes than previously believed. That may explain some of the oddball decisions pilots have made before stuffing airplanes into the ground. If a pilot isn’t concerned about the quantity of oxygen on board and the cost of replacing it, he or she will be more likely to use it at lower altitudes, increasing the level of safety.

Durr Tecknik’s response referenced the unit that was provided for our review and said it “is an early, working prototype that we use for trade show/bench demonstrations and occasional test flights. As such, its wiring harnesses and cable arrangements are not up to the standards of the production unit. We sent this example for two reasons; one is because this is what we had on such short notice, and second because we understood that you wanted to test the performance and the user experience with the unit, both of which are identical to the production model.”

“As we clarified it during our earlier conversations, the OXYFLY models are offered as mobile devices and not FAA certified. We’d like you to know that both versions were designed to follow FAA regulations, while the OXYFLY Light was to be offered as a permanently installed aircraft accessory. Our engineering [department] has been continuously making adjustments and revisions to the specifications in order to prepare the product for the RTCA DO-160G test procedures. Those changes, however, do not affect the performance and functionality, but are geared towards compliancy.”

I was critical of the failure to use aircraft quality wiring. Durr Technik said, “Accepted. Indeed, this is one of the areas in which we have had to make improvements, our engineering is working on it.”

I was critical of wire bundling and chafing. Durr Technik’s response, “Accepted. This is especially apparent on the prototype we presented to you. The current production models show much improvement to the acceptable level.”

I criticized the electrical connectors as not being aviation quality. Durr Technik’s response, “Partially accepted. The power cord and the locking connectors we used in the system are military grade and generally used in transportation/aviation products in Europe, however, they are not FAA certified.”

I said the cooling fan appeared to be a computer cooling fan, not up to aircraft standards.  Durr Technik said, “Partially accepted. The fan is a heavy-duty industrial type, even though the look is deceiving. It has been used in many transportation-related applications, in fact it’s tested for EMC, vibration, shock, environmental, salt and fog endurance, however, it does not carry an FAA certification, even though it might be fully compliant.”

I was concerned that something loose in the aircraft could come into contact with the hot compressor during flight. Durr Technik disagreed, “Disputed. The OXYFLY Light was especially designed to be a permanent accessory on the plane, with a dedicated location where foreign objects cannot come into contact with the hot surfaces. In situations where the open frame model is not appropriate, the fully enclosed, standard OXYFLY is recommended.

I noted that the soft shock mount of the compressor would allow it to impact the casing in turbulence. Durr Technik agreed in part, “Partially accepted. Optimizing the vibration absorption is a complex challenge with two major scopes: vibration transfer to external and internal parts, with the latter one aiming to prolong the life of the compressor. With the tight space allocated, it is challenging, but our engineering staff has already made improvements in this area on the production units, so the movement of the compressor is less pronounced.”

Durr Technik is not a novice in the air compression business. It has been manufacturing air compressors, compressor systems and customized air systems for 32 years. It supplies compressors and complete systems to the railway/transportation and telecommunication industry, medical and laboratory instrument manufacturers and nitrogen generator manufacturers.

It takes some degree of courage to expand a business into making products for aviation. It’s highly regulated and the financial penalties for making a mistake can be significant. Based on what Durr Technik has said, it appears to me that it is determined to do the OXYFLY series right and it will be making improvements. I’m looking forward to reviewing the OXYFLY again in six months or a year. I keep thinking that, while expensive, when someone refurbishes a six-place single or twin, replacing the factory oxygen system with an OXYFLY might be the way to go to get the most out of the airplane without having to mess with oxygen bottles.

—Rick Durden