The best engine for the job?

By Bob Stephens

For many builders the Rotax 912 will be the perfect engine for their Zodiac. Using this engine has the added advantage that it has been used in a number of aircraft already flying in the UK so that getting a permit to fly should not be a major problem. There are those however who may wish to consider a different power plant for their aircraft. I am one of those people who would like to look at other options before I make a final decision on the type of engine to drive my Zodiac.

As the main means of power to keep an aircraft in the air, I feel that the power plant is the major component of the aircraft: I would guess that most people would agree with me. For this reason I was quite interested to read an article a while back in Pilot magazine describing the Mid West AE 100R Wankel Rotary Engine as used in an ARV 2: some of you may have seen the article. I was immediately struck by the plus points of the engine: it was a similar weight to the Rotax; fewer moving parts; but greater bhp. To me this looked as though it had plenty of potential as an alternative to the Rotax, however a bit research was still required. For instance were the AE 100R’s dimensions considerably different to the Rotax’s? What type of mounting would be required? Where was the C of G? How did the performance compare with the Rotax?

To answer my questions I contacted Ken Huntley at Mid West Engines, Staverton. I was soon provided with a spec sheet and a drawing of the engine. The following are the specifications compared to the Rotax 912:

My immediate thoughts were for a similar size engine one got an increase in max power: useful for take offs and getting out of sticky situations. However how did the consumption compare with the Rotax? From Alec Benders article his HDS cruises at 125 mph at 5000 rpm and 3 gph. If this is the case then does the extra power warrant the increase in fuel consumption? If the fuel consumption is nearly twice that of the Rotax then I don’t think so. I’d be interested to hear what anyone else thinks.

I am still looking at which power plant to use. I gather that some people are considering a Subaru conversion - does anyone have any details? Does anyone have details for the Mazda Rotary engine? Anyone thought about the Rotax 914? I’d like to produce a table of as many types of engine as possible to allow members to consider the various options, so if you have any specifications to hand please send them to me.