Letters: September 2014

Your article about the Lightspeed PFX ANR headset in the August 2014 issue of Aviation Consumer could not have arrived at a more opportune time and was spot on in its evaluation.

I had just purchased the Zulu PFX a few days earlier and while I think it is the quietest and most comfortable headset on the market, some of the same bizarre effects that you noticed—low-pitched fluttering and ANR performance issues when moving the head—were present in mine as well. I have serial number 189.
I did reach out to Lightspeed and they thought it may have been a fitting issue. The company immediately sent out new earseals and a larger headpiece cushion. I changed both of these and noticed that the ill effects lessened considerably.

However, something I discovered is that if you activate Bluetooth while the headset is on, the automatic headset shutdown feature is disabled. When I inquired to Lightspeed about this issue, they indicated that the CPU still hears noise and keeps the headset on. This is extremely frustrating because when you go to use your headset the next time, the batteries will likely be spent. I’m hoping that a firmware update is in the works to correct this.
Andrew Elwood
Essex, Connecticut

We’ve gotten mixed reviews from new PFX owners, including one that had two new sets fail out of the box. As we report in the PFX follow-up on page 23 of this issue, swapping the headband pad to the taller one cured the ANR problems we experienced during the evaluation. As for the other issues, Lightspeed said it’s working on several improvements for a future firmware upgrade.

Inlet air filters
To add more information to your recent air filter comparison article (August 2014 Aviation Consumer), I compared the Brackett air filter to the Donaldson air filter on my Beech P-35 Bonanza, equipped with a Continental IO-470N. The data was recorded using a JPI EDM 800 and a Horizon digital tach. Each test was at full throttle and the tests were performed on the same day to make the conditions between tests as similar as I could. Pressure altitude was 9500 feet and the temperature was 66 degrees.

With the Brackett installed, I recorded fuel flow at 13.4 GPH, manifold pressure was 20.6 inches and the measured RPM was 2450. With the Donaldson, manifold pressure increased to 20.7 inches and I gained 2 MPH in both indicated and true airspeed.

I have the engine oil analyzed each time I change the oil and the oil filter after 45 to 50 hours of use. I saw no difference in the silicon readings between the air filters, so I presume the Donaldson and Brackett air filters do an equal job of filtering the engine air.

While there was a slight increase in performance with the Donaldson over the Brackett air filter, I found the Brackett element was much easier than the Donaldson air filter to remove, clean and reinstall. Also, the Brackett foam element is less costly than the Donaldson air filter assembly.

After using the Donaldson filter for 472 hours, I switched back to the Brackett. For me, the very slight increase in performance of the Donaldson filter did not justify the extra time in maintenance or cost over the Brackett.

Rick Grossmann
Overland Park, Kansas

Excellent air filter comparison in your August issue. You guys did all you could possibly do without getting into expensive lab testing, but in my opinion (as an experienced A&P with an IA certificate) that doesn’t matter much. What does matter is that the filter is serviced on a regular basis. To me, it’s less about questionable performance gains and more about maintaining air flow to the engine.

Stan Sutton, Jr.
via email

Cabin coolers
Nice article on portable cabin coolers in your August issue, but you missed an important factor. I bought an Arctic Air Cooler about six years ago. The perceived benefit provided by any of these coolers is greatly affected by the dewpoint. An 85-degree cabin with a 75-degree dewpoint will be significantly more unpleasant compared with the dewpoint at say 60 degrees.

Sure the cooler cools, but it also dehumidifies the cabin air. I found my cooler most effective when running it from the time the cabin door closes until just after liftoff and then again just after touchdown until the cabin door opens.

Ted Stanley
via email