Metal on Metal
This question is in regard to your September 2012 issue article “Installing the Firewall.” I am building a Glasair. There are penetrations through the firewall for a number of hydraulic-type fittings (brake lines, gear and fuel). I like your recommendation of using steel fittings through the firewall because of the high melting temperature. However, my hydraulic and fuel lines are aluminum. Is there a corrosion concern in fastening the two dissimilar metals together?
Dave Prizio responds: In all cases where dissimilar metals are in contact, it is a good idea to be concerned. However, I haven’t seen the use of steel fittings and aluminum lines to be a problem as long as they are used in a dry environment. If you store your plane in a coastal location where salt air could be a problem, it might make sense to use aluminum fittings. In that case, if I had to trade better firewall protection for preventing brake failure due to corroded lines, I would protect the brakes first and then compromise on the firewall.
It was great to finally see a comprehensive article on electronic ignition systems for aircraft [“Electronic Ignitions, Part 2,” October 2012]. Well done.
The article also reflects some of the skepticism toward electronic ignitions that I see in aviation, while there is great enthusiasm for all-electronic engine controls in all other motor sports.
Concerns from some engine builders who are “wary of EI because they have seen the ignition timing too far out of useful parameters” should be addressed.
The ignition advance curve on most, if not all, electronic ignition systems are fully adjustable! With the Plasma CDI, the optimum timing can be adjusted using a linear potentiometer to within 0.1°! So if the electronic ignition’s timing is “out of safe parameter,” then it is the installer, i.e. engine shop, who configured the EI that way.
There is also this myth that mags make more horsepower than EI. So here are some aircraft for your readers to consider: The fastest Lancair IV uses Dual Plasma III. The fastest stock Glasair III uses one Plasma CDI. The fastest stock Legacy uses Dual Plasma III. This is just to name a few.
Light Speed Engineering, LLC
Much of Paul Dye’s writing is interesting and informative. However, I feel that “Planning Your First Flight,” [October 2012] is a great disservice to anyone using the information to plan an E/AB first flight. Performing a first flight from such a marginal runway/runway environment as Polly Ranch demonstrates poor judgment.
In most areas of the country, E/AB first flights from much better runways are prohibited solely because they are surrounded by heavily populated areas.
I would submit that I can conduct a first flight with virtually no support people or equipment. No chase plane, no fire truck, no communication—just myself and a well-prepared aircraft. That flight will be far safer than Mr. Dye’s because it will be from an 8000-foot runway with large clear areas at both ends.
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