Letters: 09/03

New Engines
I agree 100-percent with your conclusions in the July article about Bombardiers engines. One data point for you: Rotax builds the 998 cc 60-degree V-twin engine used in all the larger Aprilia motorcycles. (Whats this? An Italian bike with an Austrian engine?)

Its a great little engine, powerful and flexible and so far extremely reliable. Itll do 110 HP at the rear wheel in totally stock form and 120 to 125 HP with a freer-flowing pipe and a slight remap. But…they are notoriously thirsty! A similar-displacement Ducati can pound out 40 to 48 MPG all day long, but the Aprilia Tuono I have only once touched 40 MPG; more often its 35.

Just for your interest, the coolant temp did swing a bit on my Rotax 912-powered Pulsar kit airplane. But I think thats partly because it was a clean airframe and slightly overcooled to start with. Plus, in that installation, there were no baffles around the cylinder barrels, just some simple baffling to slope the air in between the nose cowl and the first cylinders and some block-off plates around the radiator to force air through it.

-Marc Cook
Via e-mail


You know, Continental built up a liquid-cooled engine with both air and water cooling for the Voyager. They chose not to pursue the small displacement version, which would have been super for homebuilts. The large displacement units that RAM retrofitted have quietly disappeared. I wonder why?

Id really like a liquid-cooled engine for our Glasair. It would help in the Phoenix summers and I wouldnt be as concerned about rapidly cooling the cylinders on descent. A V-design without valve train problems would really be nice. Hope Bombardier succeeds.

-Mike Palmer
Phoenix, Arizona


I cant believe this. When I read about the Katana and the Rotax version, I thought I would learn more about the AD on the 912. There was no mention ofAD 2002-21-16. It is apparently based onRotax SB 912-036 R1 andSB 914-022 R1.

A mechanic at Thunderbird Aviation at KFCM had told me about it a couple of months ago. He said that they have to go through about five hours of work every 50 hours when they do an oil change. (At $60 an hour for labor, that is an additional $6 an hour in operating cost.)

Anything that possibly gets air into the oil line requires this procedure. Someone turning the engine backward two full revolutions would also require it. He alsosaid that water leaks were the biggest problem they have with it. Apparently, the oil that they are using in it costs $12 a quart. Didnt sound like any engine that I would want to own! I also asked the owner of a Zenith 601 and he didnt seem too concerned. He did get an SB from Rotax but he just made sure that he watched the oil pressure pretty closely for the first hour or so after he did an oil change. I have never looked up the specifics but would suggest that you do so and cover it in the next issue.

-Harv Havir
Edina, Minnesota

The AD requires venting of the lubrication system and inspection of the valve train on all engines… on which the lubrication system has been opened, and any engine on which the propeller has been rotated one full turn in the reverse direction.

It was prompted by reports of in-flight failures which resulted in forced landings due to valve train damage caused by inadequate venting of the lubrication system.


I enjoyed reading the article on turbocharging in your August issue because of my accumulated experience flying turbocharged aircraft and because of my recent frustrations with the maintenance of turbocharged engines.

Over the last 15 years, I have owned and flown a P-Baron, a Cessna 421 and now that I am an empty-nester, a 1998 Mooney Bravo. Many of my trips are flown from my home in Iowa to both coasts, so cruising above the weather and terrain has added significantly to the utility of my airplanes.

I flew two engines to TBO without any major problems in the P-Baron and had some minor cylinder problems in the C421, which were easily repaired. But in the Mooney, cylinder problems and, recently, turbocharger problems have occurred that are resulting in significant down time and expense.

Has Aviation Consumer ever done a comparison of the down time, maintenance costs, and parts availability of the various models of turbocharged airplanes? Id guess that there would be some interesting findings that would help those of us who own turbocharged airplanes.

Right now, Im having trouble finding a new or overhauled turbocharger for my Mooney and I am not alone. My mechanics have three Bravos waiting for turbochargers. The problem, Ive been told, is that Garrett sold their turbocharger business to a company called Kelly Aerospace, which will not start manufacturing parts for turbochargers until the end of August.

That essentially puts Mooney out of the business of manufacturing turbocharged airplanes and Lycoming out of the turbocharged engine business until this problem is solved. Mooney is unwilling, of course, to give up the turbochargers that they do have.

So, my airplane is grounded while I wait for a part that might be ready in another six weeks and Im sure that I wont be one of the first on the list to receive a new or overhauled turbocharger, once Kelley Aerospace has started production.

So, from my own anecdotal experience, Id guess that the Mooney Bravo would not fare so we’ll in a maintenance and reliability study, but it would be more helpful to those of us who own turbocharged aircraft to be able to look at some accumulated data on the subject in order to make informed decisions.

And you could add parts availability and excessive down time to your list of negatives in your article this month about turbochargers. I suppose you could say that I would have covered a lot of ground in a non-turbocharged airplane in that amount of time!

-Dirk Brom
Des Moines, Iowa

We havent done any specific surveys on turbocharger reliability, maintenance and down time. Its certainly a worthy subject.

We contacted Kelly Aerospace which confirmed that there are manufacturing delays for the turbochargers it builds. Kelly tells us the delays have been due to delivery problems from Honeywell/Garrett, which retains the tooling for the cast turbine wheels. Kelly hoped to resolve the problem by the end of August, 2003.


Although I found your article on the CNX80 in your June issue very informative, you need to bring up the issue of interface to external indicators. I have been informed that as long as your HSI/Sandel/VOR-ILS nav head center of the instrument is within 13 inches of the CDI switch on the CNX80, your aircraft does not need that very expensive ACU UPSAT sells. Is this true?

And I still believe all but the S-TEC 55 model (and maybe it as well) requires the ST901 for GPSS steering? Is this also true? Also, do you know if UPSAT will develop its own Mode-S transponder?

-Marc Wiese
Via e-mail

UPSAT tells us its not sure if it will develop a Mode-S transponder. Its waiting for the ADS-B market to settle out before deciding. In our report on the CNX80 in the June issue of Aviation Consumer, we reported that the CNX80 requires no external annunicators. Since then, the FAA has said TSO-146 boxes will require annunication for CDI status. This consists of a small light panel, not a switching network, the ACU.

As far as we know, the S-TEC autopilot does require the ST901, but only for roll steering.


In our July article on fire extinguishers, we reported that Halon is limited to aviation only use. Actually, that limitation applies only to Halon 1211/1301 blends, not Halon 1301 alone.

H3R, a leading supplier of Halon extinguishers, recommends that bottles be recharged after incremental use due to potential leakage.