When the temperature dips into the low 20s, everyone we know seems to agree that preheating an engine before starting is a good idea. From that point forward, however, opinions diverge. How much preheat is enough? How long should you run it? Is an electric system better than a propane blower? There are no pat answers. There are a dozen ways to heat an engine from makeshift propane-fired torches to
100-watt lightbulbs in the cowl flaps. All of them work, but some clearly work better than others.
Ignoring homebrew solutions, the preheat products divide themselves into two broad categories: devices you mount permanently on the airplane and those you carry around or store in the hangar for use when needed. In this article, well examine aircraft-mounted systems all of them electric. In a future article, well look at portable systems, both electric and propane.
Although a handful of players ply the installed preheat market, the field is dominated by two major companies Tanis Aircraft Services and Reiff Preheat Systems, both of whom have introduced incrementally new products since we last examined this topic six years ago.
As a scratchpad reference, we found that a typical installed electric preheat system costs about $500 to $600, plus another $1000 for an engine blanket, a remote-control switch of some sort and more yet if you want to preheat the cabin, too.
The Big Two
Both Tanis Aircraft Services and Reiff Preheat Systems, take a comprehensive approach to heating an engine, but they go at it from different directions, literally. Both companies sell products that heat the oil and the cylinders with separate elements. They also offer ancillary preheat products to make preheating easier, more efficient and owner friendly.
Tanis was started in 1973 by Peter Tanis, a north country inventor and pilot who was considered the preheat industry guru for years. After Tanis died in 2000, the company was owned by Gary Schmidt, who perished in an aircraft accident in 2004. Tanis is now owned by Bob Kruger and Linda Cole, who were in charge of manufacturing almost from the companys inception. Tanis has an excellent Website and a catalog of myriad preheating and support products.
Tanis believes that heat needs to be put where its needed on an engine, which is the sump, cylinders and case, respectively. Tanis big idea is warming the cylinder heads with small plug-like elements that screw into CHT temperature holes. They also sell ingenious 42- or 50-watt bolts that replace one of the intake collar bolts. Tanis system also have sump heat capability, consisting of cloth- and silicone-covered elements that come in sizes ranging from 50 watts to 120 watts, in different configurations. If the customer has engine analyzer probes already plugged into the CHT ports, he can opt for either a replacement washer-type CHT sensor to use with the analyzer or a combination CHT sensor/heater probe. Normal heating, according to Tanis, is considered to be three- to five-hour event, using a cowl blanket to limit heat loss. Customers choose the system they feel they need in either a Standard or a Super configuration. The standard heats an engine in ambient temperatures as cold as -30 degrees F, while the Super promises to perform at -65 degrees F. What this means is that on cold days when any sane pilot would deign to fly say 20 degrees F the Standard will warm the engine in three or four hours and the Super in one to two hours.
Tanis has a full catalog with extension cords, custom cowl blankets, remote on/off boxes, interior heaters (two styles) and battery warming kits. They offer a crankcase ventilator and are soon to announce a new crankcase dehumidifier.
Reiff (rhymes with “life”) is the new kid on the block, if 20 years of experience can be considered new. Bob Reiff parlayed a masters degree project into a business, starting with a portable, self-contained propane blower powered by a car or truck battery. Over the years, Reiff has added hot pad technology and it introduced the HotBand product in 1996.
Reiffs HotBands are high-quality stainless steel hose clamps with heating elements bonded to them. They install around the cylinder base, between the deck and the first cooling fin. Theyre easy to set up, so easy in fact that both owners and cavemen could do it. Reiff developed the bands in response to the popularity of engine analyzers during the 1990s. The company wanted a product that would be
unintrusive and that wouldnt conflict with CHT ports.
In 2001, Reiff changed their sump heater design to a new metal element type. Having a dissimilar product may or may not be a marketing plus, but Reiff contends that their elements are reusable, more durable and more tolerant of installation errors than older silicone-style pads.
As does Tanis, Reiff offers ancillary products, such as custom-fit engine blankets, which we have previously rated highly. But Reiff parts company with Tanis on the need for a blanket: They think its generally not necessary, especially if the airplane is hangared. For convenience, Reiff offers remote and timer/thermostat based on/off modules and for cabin heat and battery charging, they simply suggest some inexpensive products and where to buy them.
While Reiff allows a la carte selection of just a pad, just the HotBands or both, Tanis markets only complete systems. We tried systems with both cylinder heat and sump heat.
Tanis recommends that its systems be installed by an A&P and their warranty reflects this. Reiff endorses owner installation, if the owner so chooses. Installing either system isnt particularly difficult, but the Tanis products requires ingenuity in routing and securing the leads to CHT, EGT and mag leads, for which Tanis provides a generous supply of aircraft-quality wire ties. The Tanis system we chose used bolts that replaced one of the bolts holding the intake pipe collar, although they sent the CHT-mounted probes and washer type CHT sensors to accommodate our analyzers.
The Tanis cylinder elements are simple to install. Just remove one of the intake bolts, install a new lock washer and torque to spec. This is an ingenious solution to the CHT probe problem. An hour later, the installation was complete, although the wiring takes a lot of fussiness with tiewraps. Both of these systems add unavoidable wire clutter to the engine compartment.
The Reiff HotBands required about six minutes each to install, by simply plugging into the supplied harness and securing with Adel clamps to the case bolts. In the Tiger we installed the Rieff system on, the oil filler neck is behind the baffling, so Reiff says you can drill a hole through the baffling for the power lead. Or you can run the lead forward and access the plug from the front of the engine. In most engines, the power plug is accessible through the oil door.Sump pads are by far the most difficult installation task for either system. Tanis requires a clean surface, using MEK, lacquer thinner and finally alcohol to clean the surface. RTV silicone is applied to the pad and all bubbles are forced out with a squeegee. The pad is then clamped into place using tape, foam blocks or whatever works.
Reiff provides JB Weld epoxy to hold their metal heat pads in place. This is strong stuff and cures well, but in a 25-degree hangar, it’s no fun to use. Although we cleaned the paint carefully, we had problems with the JB weld, partially because Reiff’s instructions weren’t all that clear. It warns not to use heat to cure the stuff, but a few sentences later, it says it’s OK to turn on the pad after two hours. The heat reference is actually for a different epoxy type, which we didn’t have. We’ll take the hit for messing this up, but the instructions need clarification, so points to Tanis here.
To test the two systems, we waited until mid-January, when a howling winter storm dumped a couple of inches of ice and snow followed by temperatures in the teens in western Missouri, our test site. Testing was done in two unheated hangars on a Grumman Tiger with a Lycoming four-cylinder O-360 and on an American Yankee, with a four-cylinder Lycoming O-320. Both aircraft have multi-probe engine analyzers installed and both aircraft had older silicone pad heater elements installed, which were not used for the initial test. However, we did perform a test using a sump heating alone.
Taniss Bob Kruger loaned us a fitted cowl cover from his AA-1C Lynx, a perfect fit for the Yankee. Both companies agreed that in a closed building, without wind and precipitation, any insulating medium, such as a thick blanket or sleeping bag, would be adequate for warming, with variables being the design and wattage of the heating units and time allowed for heating. We tested the systems both with and without the insulated blanket.
Our test equipment consisted of Onset Data Loggers, which are programmable devices that record temperature from K-type thermocouple wires. We attached temperature probes to the first inboard fin of a cylinder, between the two outboard fins of the same cylinder, at the top centerline of the case at a bolt head and at the end of the dipstick, to sample the oil temperature. These sample points were selected to gain a general sense of how warm the engine was after four hours of heating.
The true measure of a preheating system, in our view, is not the engines actual temperature, but how much the system raises it above the ambient. Any system capable of a 30- to 40-degree rise above ambient will be suitable for most owners in the lower 48 states.
The accompanying graphs give the actual test data, but well bottom line it here in so many words. If you want to buy only a sump pad and heat the oil alone, it will given enough time and an engine blanket heat the entire engine to an acceptable starting temperature.
In very cold weather, thats likely to be six hours or more. In crazy cold weather say well below zero we dont think it will be adequate. If you choose not to heat the engine continuously with only a sump heater and want to plug in and fly as soon as possible, youll need to add cylinder heaters.
As you would expect from the geography of the engine, the Reiff system warms the cylinder base and the case quickly, while the Tanis system gets the cylinder heads nice and toasty in short order. Overall, we found that the Tanis Standard system heats the entire engine slightly faster than the Reiff system and it gets it warmer. However, our test of the Tanis system was on a slightly warmer day. But either system is more than adequate, in our view.
To see if the higher wattage systems were better than the standard systems, we tested the Reiff TurboXP system, which has 100-watt bands and two 100-watt sump heaters, as opposed to the 50-watt bands and single 100-watt pad on the sump. No surprises: More power means more and faster heat and we can assume that the Tanis Super system performs similarly, although we didnt test it. Again, for use in the lower 48 states, we think the standard systems are adequate. If youre in a big hurry, either heat continuously or spend extra for the higher wattage systems.
If youre an adherent to the heat-the-oil-only-and-the-engine-will-follow theory, our tests prove the theory sort of. The pad-only tests were done with an EZ-Heat pad from E-Z Heat, Inc. Yes, the heat migrates from the sump to the cylinders and yes, in all but the coldest temperatures, the engine will be warm enough to start. But the process will take longer and we think youll need an engine blanket.
On a pure performance basis, the Tanis systems are the clear winners. They heat a bit faster and yield noticeably higher temperatures. However, they also cost more than the Reiff system. For example, a 250-watt setup for a four-cylinder Lycoming in a Cessna 172 sells for $420 and would probably require another $150 to install and sign off, for a total of $570.
A 300-watt Standard system from Reiff sells for $385 and is easily owner installable. Reiffs four-cylinder TurboXP system, whose performance exceeds the Tanis Standard system, sells for about the same prices as the Tanis $585. So on a dollar-for-heat basis, the two companies are nearly neck-and-neck.
But because Reiff offers a lower-priced option that gets the job done, we think its Standard system is the best value choice for most owners. With Tanis, youll pay about 30 percent more and enjoy slightly better performance. But heat is heat and both systems yield an engine warm enough to start. For the extra money, Tanis does it a little faster.
Warranties are always a consideration. Reiff offers two years on materials and workmanship, whether professionally installed or not. The Tanis warranty is three years, if installed by an A&P and correctly logged. Both companies will either exchange or repair the defective parts.
Tanis systems are FAA/PMAd, even though this is not a requirement, except for the intake replacement bolts, which not all of the systems use. The FAA, by the way, considers preheating systems minor alterations and appliances that arent used in flight, thus they generally escape the paperwork hassle. (Your local FSDO may have different ideas, however. If so, dont blame us.)
Tanis offers a fuller line of heaters than Reiff and has dozens of different kits for different airframes. They also have more support and ancillary preheat/flight prep materials and tools. On the other hand, Reiffs four basic kits cover the waterfront of models and types. If you own an airplane, Reiff can probably preheat it.
We found both companies to be friendly and cooperative to deal with. In short, they know what theyre doing and thats always refreshing. You wont go wrong with either one.
Jim Cavanagh is a freelance writer and aircraft owner. He lives in Kingsville, Missouri.