Letters: July 2012

DA42 VI Specs

I think you have a typo in your article on the Diamond DA42 VI in the May 2012 issue in describing the performance of the current DA42 NG. In one part of the article, you said that the NG model at 8.3 gallons per side (about 90 percent power) could only do 167 knots. It was capable of speeds as high as 184 knots at 14,000 feet­—the highest altitude 90 percent power was available from the Austros in the NG.

Also, I would like to point out that the DA42 NG familiarization guide (highlighting the differences between the Thielert- and Austro-powered DA42s) shows cruise performance at power settings as high as 92 percent. But in two places in the guide, they show bold red hash marks at 75 percent power, similar to gas engines, a continuous recommended maximum cruise power setting.

I believe that the poor longevity of the original Thielert engines was due to similar operational issues. The original DA42 1.7 Thielert engines had a recommended max cruise power setting in the POH of 70 percent, but most owners regularly flew them at 90 percent because the airplane was so slow.

Gregory Wroclawski


Via e-mail

You’re right about the apparent performance disparity, but it’s not a typo. Our data comes from an observed flight trial, not the POH claimed speed.

Having said that, we rarely have time to repeat flight trials to get best-case data and/or to follow up when the POH claim doesn’t match real-world claims. We’ll concede we should do a better job of that and will try to in the future.

Engine Moisture

Back in 2006, you ran an article on engine dehydrators in Aviation Consumer. I recall this article quite clearly because from its conclusions, I purchased a set of ACI Black Max dehydrators for my Cessna 310. I’ve been using them ever since.

I’m trying to learn if it is best for me to disconnect my dehydrators when I preheat my engines or if I should leave them running. The answer will come from measuring the humidity and dewpoint in the engines with one configured with the dehydrator running while preheating, and the other without the dehydrator running while preheating. In addition, I’d like to run several other tests to measure the effectiveness of preheating and its implications for humidity inside my engines.

What I’m wondering is how you placed your data loggers down the oil filler tube on your test airplane. What did you use to lower these into the crankcase and how did you retrieve them? Would you please tell me which model data logger you used, how you controlled it down into the crankcase, and how you were able to retrieve it? Also, how did you get the data loggers into the cylinders?

Ken Sutton


Via e-mail

As noted in the article, we used Lascar EL-USB-2 dataloggers, one of which we inserted in the oil filler tube, attached with a strong cord. It’s too big to fit all the way down the filler tube, so we constructed a foam gasket to seal out any ambient humidity.

As for the cylinders, we built small chambers of plastic pipe to house the dataloggers, then screwed these into the sparkplug holes. These probably don’t yield exact readings for the cylinders, but it’s as close as we could get.

Battery Chargers

I just read your articles on battery chargers in the October 2011 issue of Aviation Consumer and came across a charger while I was looking for the one you recommended. I am in no sense a battery geek or an electronic buff, but I cannot find a significant difference in the charging specs of your recommended battery minder and this one.

This is by no means an attempt to find a better aviation charger, but just a find one at a lower price. With technology changing, something will always pop up. Could you please check the specs? This one can charge 12- and 24-volt batteries.

Rudolph Steencamp


Via e-mail

The model in question is a NOCO Genius G7200. See the specs at www.atbatt.com. We’re not familiar with this charger, but have asked them to send a sample. It looks good on paper, but has the capability to reach 15.5 to 17 volts in boost mode.

That would definitely damage a 12-volt aviation AGM battery. Furthermore, the VDC BatteryMINDer, which we’ve picked as our Gear of the Year best battery charger, is approved by both Concorde and Gill, while the NOCO is not.