RMI's MicroMonitor Is Many Instruments In One

By Patrick Navin

Whenever I see a great product, one made in America that can hold its own with anything made in Japan, I just have to stand on the table and shout about it to everyone.

Rocky Mountain Instrument (RMI), manufacturer of the MicroMonitor, is the same company which makes the MicroEncoder I installed in my plane three years ago. Both these instruments are a superb addition to any cockpit, and I have derived enormous utility from them.

The most important aspect of this product, other than the fact that it is very sexy, and other pilots say "cool" when they see it, is the fact that it increases safety more than anything else I have on board, including my radios. I want to emphasize, however, like any other very sophisticated instrument, the MicroMonitor is not simple to install or to learn to use.

I was installing a CD-ROM as well as a sound card on my PC at the same time the MicroMonitor was going into my plane. These systems arc analogous inasmuch as they are both expensive, require lots of time and effort, but enhance the usability of the overall experience beyond expectations. While it takes many hours to install, and if you have an A&P do it, can cost as much as the unit itself, it is eminently worthwhile.

Human Factors

Ergonomically, the great debate has always been about which is better, digital or analog. The Micro Monitor is digital, "steam gauges" are analog. Digital is inherently more precise, since the numbers are by definition binary it is either one thing or another. This type of data presentation is good when the circumstances call for a precise number, including holding an altitude, or engine RPM. Analog instruments, however, show relationships more readily you can see about how much the needle is beyond a certain point, if it has a trend, and what its rate of change is. These relationships are essentially qualitative.

A potential problem here is that your mind might have to convert certain data from one format to another to interpret it properly. On a clock, 30 minutes past the hour is mentally processed differently than "l have to leave in about a half hour." In moments of stress, the speed of processing and the resultant interpretations can be of great importance. Many studies have compared altimeters displays because of the number of accidents caused by pilots who misread their altimeters. For more on the subject, you can read Human Factors in Engineering and Design, by Sanders and McCormick.

In terms of accuracy, the electronic instrument is undoubtedly more accurate than the mechanical. It would also seem that electronic circuitry would be less susceptible to the harsh elements in rendering its information. And considering you can now take this electronic data and plug it straight into a computer for further massaging makes this product all the more attractive.

Many accidents have been caused even by experienced pilots misreading the old steam gauges. Digital representation allows a pilot to more quickly assimilate the precise data.

It is, needless to say, easier to put the MicroMonitor into a kit-built plane, since you are beginning from scratch. Perhaps that is why so many RV planes and KitFoxes, including the KitFox company demo plane, have one or both of the RMI instruments on board. Experimental builders don't need to worry about STCs, Form 337s, or TSOs, so that is a big help.

It seems ironic to me that an uncertified plane, such as the Lancair, can fly IFR in Class 1 airspace using these systems, yet I can't put one in my certificated Cessna 172 without the FAA's blessing (and paperwork). After all, what is most important, paperwork or safety?

The MicroMonitor is really a number of instruments in one. The most critical is the fuel totalizer, which shows gallons remaining, time to empty, and consumption (fuel flow, i.e. gallons per hour actually being used). There are also readings for EGT (engine gas temperature); CHT (cylinder head temperature); oil temperature; oil pressure; tachometer; voltmeter; fuel pressure; OAT (outside air temperature); manifold pressure; and a slew of alarms and timers.

If purchased separately, these instruments and components would cost upwards of $2,000; and purchased separately is the key. The MicroMonitor integrates all of them into one system, with a single, simple display. In my mind, that alone is worth a great deal, given that it reduces the complexity of installation, learning, and use.


The base product in kit form costs $969. The price fully assembled is $1,269. Add to that the cost of the various sensors, and you can figure on something around $300 more. Purchased separately, you could spend $1,500 for just three instruments: carb temp gauge, fuel flow meter, and digital tach. The MicroMonitor has much more. and it integrates them all into one simple system.

Fuel Totalizer

This is the most important feature to me it tells me how long it is before I have to glide down to Interstate 80 for a dead-stick landing. Running out of fuel is the number one cause of engine failures, claiming about one plane per week, according to Bruce Landsberg of AOPA.

The way the system works is by installing an impeller and transducer in the fuel line. To my absolute amazement, the FAA has no problem with this; they don't require a TSO'd unit.

The transducer/impeller is made by Floscan, the same people that make it for the other companies in the business; including. I was told, Shadin. The impeller is like a little water wheel that spins as the fuel flows by. It measures the passing fuel and sends a number to the MicroMonitor in the cockpit. You, the pilot, tell the MicroMonitor how much fuel you yourself have put in the tanks. What is measured is the gas that goes to the engine via the fuel line NOT what is or was in the tanks, or is blowing out over the wings.

We found the smaller transducer did not allow enough fuel to pass down the fuel line. so we opted for the larger bore transducer We especially recommend it for gravity-fed planes, such as a Cessna.

The totalizer also shows you how much fuel and time are remaining. You can set alarms to tell you to wake up at a certain point, gallons or minutes, remaining. I use the gallons per-hour function (consumption), along with the other engine instruments. such as the EGT and CHT to lean the engine. I can get much more precision and thus better fuel economy. It makes the old analog gauges in my Cessna seem quaint by comparison. Of course, they still show me some degree of relative consumption in each tank. Buying this precise digital reference saves me from having to land to refuel by telling me how comfortably I can make my destination, with how much fuel to spare.

Digital Tach

The next most important component would be the digital tachometer. When I do a mag check, I can see exactly how much my RPMs have dropped; same with the carb heat check. This offers precision, and hence, safer operations at least that is the goal.

This reduces my workload as well. There is no parallax view with digital. I don't have to lean this way and that to see what number some needle is touching. I still do look at the analog tach, but not nearly as much. As with all the other important functions, you can put an alarm on your tach with the MicroMonitor, to indicate levels, such as red-line. The alarm causes beeping and flashing to wake you up.


Ben Franklin said time is the stuff life is made of. Pretty appropriate when you consider what the built-in clocks and timers can do for you. You can set the clock for the actual flight time for the last segment; you can set a timer to tell you when to switch fuel tanks; and there is a Hobbs meter for total engine time. You also have count-down and count-up timers to tell you how many minutes until whatever. And you can associate alarms with all this.

There are separate clocks for Greenwich Mean Time (GMT), as well as Local Mean Time (LMT). A jaded friend of mine pooh-poohs these things, saying he can do it all in his head. I respond by saying that I suppose I could balance my checkbook without a calculator. but why would I want to? Truth is, I can't even balance my checkbook with a computer. So I need all the help I can get in the cockpit. And when you're blazing thorough five or six time zones in the old Skyhawk and ATIS is called out in GMT having someone or something doing the counting for you is a big assist.

Heat, Please

Carburetor icing also claims a lot of those planes that don't have fuel injection, causing such a significant number of crashes that it justifies a separate instrument. With the MicroMonitor, you can set a temperature, preferably somewhere above 32 degrees Fahrenheit, and have an alarm associated with it. That way, no carb heat need be turned on unless it is necessary. As a result, I always have full, undiverted power.

Be Alarmed

You can set alarms to tell you if the RPMs, the MAP, the CHT, the EGT, or oil temp are too high. Conversely, you can set the alarms to tell you if the oil pressure, fuel remaining, fuel pressure, carte heat, or amps, are all too low. And just like those boys flying the big iron, you can throw one switch and disable the entire lot of them with the proven, associated results. I'm told it's one of the first things the NTSB looks for: "...the report said the pilots turned off the warning devices to indicate the nose of the plane was pointed earthward... "

There are three spare alarms you can set for your own special needs, such as low oxygen, door open, canopy unlocked, or vacuum problems.

Pilot Opinions

"I think the Rocky Mountain Instrument's MicroMonitors are being put in by builders because they come in kit form and people are looking to save money by building them," says Don Pearsall of KitFox Builders, a group that builds KitFoxes under contract for customers. "Also, they have a good amount of info, and look good in a panel."

Fred Bascom is an RV-4 builder in Glenarm, Ill. He's got nearly 90 percent of plane completed, so he's halfway done. He tells me he didn't speak to anyone before he laid out $2,000 for both RMI products. He bought based on looks. "This is not a hobbyist product," he says. You couldn't buy an instrument that looks more beautiful".

Bascom is a Heathkit builder from way back. so it only took him one long day to build the instrument. He says support was instantaneous no hesitancy with a response.

Jim Siebel from Rockford, Ill., tells me he has bought three MicroEncoders and one MicroMonitor. He owns a machining company in Rockford and said the machining on the RMI products is amazing.

Siebel is building a Glastar and an Ariga. He also flies a C-182, in which he ran the products for awhile as a test platform. Jim loves the fact that all the bells and whistles are in one box, because of his limited panel space. Plus,"everything is cheaper in one system".

Siebel says he had never seen the MicroMonitor run before he bought it, but felt "if it is as good as the MicroEncoder, then it had to be a superb product."

At Oshkosh, I spoke with Van, the designer of the RV-4 and the owner of Van's Aircraft. He said he had no specific idea why so many RV builders chose to use Rocky Mountain Instrument equipment in their panels. He thought prime considerations were that it is a good value in terms of what you get for your money and use of available panel space. He said his company did nothing to encourage builders to use these particular products. It just has worked out that way, with builders speaking with other builders about what worked well in their own aircraft.


The MicroMonitor is a complete engine computer. It takes an engine, such as my Continental 0-300 designed some 50 years ago, and gives it a cutting edge, high-tech quality. Proven durability, along with space age, digital electronics. provides the best of both worlds.

Rather than replace or overhaul the old analog instruments in our Cessnas, my approach is to leave them as they are and install a digital set to complement the old stuff. Having the MicroMonitor along with a MicroEncoder, all in the cockpit in one concise place, gives your instrument scan a new dimension.

Finally. RMI builds all their stuff right here, in Wyoming, U.S.A. If Ja pan had a general aviation market, you can bet RMI would be shipping MicroMonitors over there.

For more information write: MicroMonitor, Rocky Mountain instrument. P.O. Box 683, Thermopolis, WY 82443; or call (307) 864-9300.

Web flyers can receive additional information through e-mail at info@rkymtn.com or can view the company's home page at http://www.rkymtn.com.


NOTE: The above unedited article (except for format) appeared in the September, 1996 issue of In Flight USA.