"Long Engine Life Starts With Reiff"
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These are the questions we get the most, with straight answers. If you have a question that is not listed here, please call and ask.
Can the preheater be left on continuously, i.e. will it cause corrosion?
Can I use your cylinder heater system with my non-Reiff oil sump heater?
Why did you develop the HotStrip, is there something wrong with silicone pads?
What about the other brand's claim that heating the head is best?
Do the cylinder band heaters interfere with cylinder cooling?
Do cylinder heaters cause the oil to drain off the cylinders?
Do you have any discounts for XYZ members, for buying 2 or more systems, etc.?
What's the difference between your system and [the other brand]?
How many AMPS is my system? (What size extension cord do I need?)
That depends on which system you get, how you use it, and how you define "warm".
The table in FAQ#2 below gives heating time data for several of our systems. More watts = faster heating.
How you use it affects heating time. Sealing and insulating the engine compartment to hold the heat inside will make a big difference. Testing showed that using a cover resulted in a 52% greater temperature rise (go to Articles and see "In Search of Optimal Preheating"). Use foam cowl plugs in the air inlets, and throw a blanket over the cowling. A moving blanket or bed quilt works well, or get a custom made cover. Being in a hangar vs. outside in the wind also affects heating time.
As for how to define "warm", FAQ#20 discusses this. The engine manufacturers say 20F is warm enough to start the engine. Many folks want to treat their engine more conservatively than that, just as they change the oil more often than the book says. In our view the closer to operating temperature your engine is when you start it, the happier it will be because the bearing clearances, piston & ring fit, and oil temp & viscosity are where they are designed to be. The cylinders are lubed by splash oil. Cold oil is like molasses and doesn't splash very well. It also doesn't pump very well through all the tight little spaces it has to go to lube your engine.
"It is generally accepted that a cold startup is considered to be anything below 60 F. However, an engine at rest is always cold relative to its normal operating temperatures; therefore, the oil is also thick relative to its designed operating viscosity." Harold Tucker, Director of Technical Information and Training, ConocoPhillips Commercial Lubricants. Aircraft Maintenance Technology magazine, Sept 2008
The answer to that depends on factors such as the climate where you live and at your intended destinations, is the airplane hangared, and how much time can you allow for preheating.
We provide performance and other data on the various systems we offer to enable the customer to decide which is best for him or her.
But here is our advice on selecting a system:
1) More wattage gets you faster heating and higher engine temperatures.
2) More heat is better, but any heat is better than none.
3) There is no such thing as too much heat... none of our systems will heat the engine or oil to anywhere near the temperature it's at while it's running.
4) If in doubt go up in wattage, not down. Wattage is like horsepower... no one ever complains about having too much.
5) In mild winter climates a HotStrip oil heater alone may provide all the heat you need. If the plane is hangared with cowl plugs and a blanket over the cowl and the heater is plugged in overnight, it will raise the oil about 80oF above ambient and the top end about 35o. This means if it's 20oF in your hangar your oil will be around 100 and the cylinders about 55. Getting a system with cylinder heaters (the Standard or XP System) is a good idea if any of the following are true:
- If you park the aircraft outside in the wind
- If you will fly to a cold climate destination
- If you want faster preheats (see heating time comments below)
- If you want to leave the preheater on continuously (see next question below)
6) In cold climates a multipoint system is strongly recommended. Which one we recommend (Standard or XP) is largely a function of how you plan to use it. If the plane is hangared and you can plug it in several hours or overnight, the Standard System is all most people need. Plugged in overnight it will heat the engine and oil about 80oF above ambient, about half that in 2-3 hours. That means even at -30oF you will have about a 50o engine, which is warm enough to start. But that assumes you have the plane in a hangar, with cowl plugs and a blanket over the cowl, and plug it in overnight. If your conditions are more extreme (tied down outside in the wind) or if fast heating is important, then we recommend the higher wattage XP System. Our sales run about 50% Standard and 50% XP.
It is important to pay attention to the heating time data in selecting a system that will be appropriate for the way you intend to use it. If you are the type of user who intends to plug it in for only an hour or two before starting you will need more wattage than the user who intends to plug it in overnight. Our testing has shown that maximum temperature rise occurs after about 12 hrs of heating, and about half the maximum rise occurs in the first 2-3 hours. Despite the effort we have made to provide complete info on performance and heating times, it is not always well understood by customers and occasionally someone will call and ask why his engine still feels cold a half-hour or an hour after plugging in the preheat system. Note from the Heating Time table below that our highest wattage system (XP System) raises the cylinder temp from 20 to 41oF in the first hour. That's a 21o increase, but if you put your hand on a 41o cylinder it will feel cold. If you wait 12 hrs, the same cylinder will be about 150F and you will likely burn your hand.
Also be aware that a "quickie" heat will not allow time for the heat to soak uniformly throughout the engine like overnight heating will. It takes time to heat 350+ pounds of metal. With a 1-2 hour preheat it's mainly just the oil and cylinders being heated, because that's where the heating elements are.
One last caution, don't use your aircraft's oil temp gauge or electronic monitor to determine how fast the preheater is heating the oil. The oil temp sensor is not in the oil, it's on the back of the engine. It is not measuring the oil temp unless the engine is running and oil is flowing to the sensor. When we develop heating time data we place a thermocouple in the oil, inside the sump.
HEATING TIME Actual temps on our Cherokee 235 with Lyc 0-540. Aircraft was in our unheated hanger, the air inlets were plugged with foam rubber cowl plugs, the cowling was covered with a blanket which laid over the top and hung about halfway down the sides, and the sump had 9 qts of oil. The temperatures were obtained by a calibrated digital thermometer with a remote probe inserted between the top two fins on the center left cylinder, and a second probe dropped down the oil filler tube with the tip suspended at the 4.5 qt level.
HotStrip System 200w on oil sump
Standard System 50w/cyl, 100w on oil
XP System
100w/cyl, 200w on oil
ELAPSED HOURS CYLINDERS oF OIL oF CYLINDERS oF OIL oF CYLINDERS oF OIL oF 0 20 20 20 20 20 20 1 26 66 35 52 41 66 2 33 80 46 63 60 84 3 37 87 57 73 77 100 5 46 96 74 87 105 123 12 60 104 103 110 147 156
We encouraged Aviation Consumer for years to conduct a study on this issue. Here it is...
PREHEAT AND CORROSION: NO SMOKING GUN
Aviation Consumer, March 2007, pg. 23
We can't print the article due to their copyright, but you can buy a copy off their web site. Here are a few excerpts:
They instrumented a Continental 520 on a Bonanza that was equipped with our Standard System. The preheat system was plugged in and they recorded internal crankcase temperature and %RH (relative humidity) data over a 7 day span. During that period ambient temps ranged from teens to 30F.
Results... The internal RH started at 60%RH at ambient temperature. After about 12 hrs of heating it stabilized at about 120F and 15%RH and it held pretty constant for 7 days.
Conclusion... "These findings don't support the view that preheaters cause corrosion."
"Clearly, a preheater seems to dry the engine out, not cause it to behave like a terrarium."
"While our experiment is far from definitive and doesn't consider all possible ambient conditions, it does seem to show that far from causing corrosion, an always-on preheater actually appears to benefit the engine."
Also see this article...
"Always-on PreHeating: No longer a sin?" by Henry Fiorentini
Despite the above two test reports, we feel it is not prudent to assume that you can never get corrosion in an engine if the preheater is left on continuously. There are other variables involved. Probably the main risk factor is inactivity. Engines that sit a lot can get rusty, whether they have preheaters on them or not. If your aircraft will be inactive more than 30 days, you should read these:
Lycoming Service Letter No. L180B
Engine Preservation for Active and Stored AircraftContinental Service Information Letter No. SIL99-1
Engine Preservation for Active and Stored Aircraft
The risk of corrosion may also depend on the type of preheater you have...
If you are using an oil sump heater alone, we recommend NOT leaving it on continuously unless the aircraft is flown frequently, and neither do the engine manufacturers. Any oil heater used alone will raise your oil temp more than it raises the top end. For example, ours raises the oil about 80oF over ambient, and the top end around 35. Since there is usually a lot of moisture inside your crankcase, we're afraid the oil heater will fill the case with warm moist air and condense water on the cooler top end parts.
With oil and cylinder heaters installed condensation may be less likely to occur because the entire engine is heated more uniformly. However, we recommend NOT leaving it on continuously unless the aircraft is flown frequently, or unless you have some good reason for needing the aircraft "ready to go" all the time.
If you do want to run your preheater continuously, you can probably reduce the risk of condensation by:
Sealing and insulating the engine compartment with a good cover. This traps the warm air in the engine compartment which helps everything in the engine compartment to be warmed more uniformly. The key is to have uniform temperatures. Without a temperature differential there can be no condensation.
Removing or loosening the dipstick or oil cap may also help to reduce internal moisture by ventilating the crankcase. As the moist air in the crankcase is heated by the engine heater it will rise and escape out the dipstick tube, and dryer ambient makeup air will enter through the oil breather line. We always loosen our dipstick after shutting down, even in summer.
You can also minimize crankcase moisture by reducing the amount of water that accumulates in the oil during engine operation. Some things you can do to help are:
Make sure that the oil temperature rises to 180o F during engine operation. If the oil temp runs colder than that, as many do in the winter, water may accumulate in the oil rather than evaporating and being expelled out the oil breather. Cold oil temps can usually be cured by blocking off a portion of the oil cooler.
Check the oil temp gauge to make sure it is accurate. This is easy to do by removing the sensor and submersing it in hot oil or water along with a thermometer (don't forget to ground it or it won't work). If your oil temp gauge's markings are not accurate, mark the correct numbers on it with a felt tip pen, especially the 180o point.
Change the oil frequently, especially in winter. Corrosion causing water and acids will build up in the oil over time, and replacing with clean, fresh oil is cheap protection. The maximum oil change interval set by the manufacturers is based both on hours of operation and elapsed calendar time, typically 50 hrs or 4 months, whichever occurs first. Remember that this is just the "maximum" - more frequent changes are better.
Here's what Continental and Shell Oil have to say on this issue:
The manual for the Continental IO-550 says "WARNING: Do not leave engine mounted pre-heater systems on for more than 24 hours prior to flight. Continuous operation of engine-mounted pre-heater systems may result in aggressive corrosive attack to the engine internally."
Shell Oil staff research engineer Ben Visser says in an Aeroshell ad on the benefits of preheating : "One final note of caution: Do not plug in a heater and leave it on for extended periods of time. If you have moisture in your oil, the heater will increase the vaporization of the moisture, which will condense on the cool, nonheated engine parts and increase rusting."
Notice neither Continental nor Shell make any distinction as to the type of engine heater used (multi-point vs. oil heater only), or whether an engine cover is used or not. As stated above, I think logic tells us that these are important considerations. Mr. Visser seems to acknowledge this in a later article in Cessna Owner magazine, July 1998: "Oil pan engine preheaters - these are fine if used before flight, but do not leave the units plugged in. These units will gradually evaporate moisture from the oil, but the rest of the engine is still cold, so you end up with a humidifier cabinet that will rust the bearings and other engine components."
The bottom line is, you should evaluate all the above information and weigh the risk of corrosion against whatever benefit you may get from leaving it plugged in. We believe that the best, least risky way to use your preheat system is to run it overnight before a flight. If it's inconvenient going to the airport to plug it in the night before, consider using a remote control.
Yes.
Why is your price so low?
Sometimes those who notice that our primary competitor charges nearly TWICE what we do for a comparable wattage multi-point system, assume ours must be lower quality.
Actually our quality is second to none - don't be misled by our lower prices. Our systems are built rugged using top quality materials to withstand the temperature extremes and tough operating environment in your engine compartment. For example, wiring is Teflon insulated to tolerate long term exposure to high heat and abrasion. Then the wiring is covered with fiberglass reinforced silicone sleeving. We use high quality AMP connectors with nickel plated terminals for corrosion resistance.
The reason for the large price difference isn't because we make them "cheaper", it's because we make them smarter.
For example:
- Our systems are carefully engineered for production efficiency as well as durability, performance, and fit. With all the different types and combinations of heating elements and thermocouples they need to address the CHT interference problem, our competitor used to list exactly 143 different standard systems to fit all the Lycomings and Continentals. We need 4 systems to fit the same engines. By 2010 they finally followed our example and simplified their line-up greatly, and they now list "only" 19 systems. But they still have 85 different models of silicone pad oil sump heating elements, we have 2 oil heater elements to fit all the engines. Which product line do you think can be produced more efficiently, with fewer people, and therefore at lower cost? The customer benefits from our lower cost, without sacrificing quality.
- Low overhead costs. Besides needing fewer production employees, we also limit advertising to 2 or 3 key publications and let word of mouth do the rest. The internet also makes expensive print advertising less important.
- Most of our sales are direct to the aircraft owner, whereas they sell through dealers who get up to 40% profit, plus other incentives (such as free Snap-On tools), for talking you into buying their expensive system. This dealer profit and freebies are obviously built into their price and passed on to the aircraft owner.
We understand the opinion that a lower priced product must be inferior to one that costs more. It is a common one held by the general population. Fortunately for us our customers are not the general population. Most aircraft owners are perceptive enough to realize it is not always true, but if you are someone who always equates price with quality, then we understand you may be happier buying a competitor's system at up to twice the price.
Why is your price so high?
Usually those who ask this are comparing our price with automotive engine heaters. There are several reasons why this is not a vaild comparison.
- Economy of scale... The automotive market is much larger than the general aviation market, so costs can be spread over many more units. In 2009 there were 12,000,000 new autos sold, and 965 piston aircraft. A typical new 4 seat piston aircraft costs at least 10 times what a typical new car costs. Isn't it reasonable to expect the same of aircraft parts?
- Liability insurance cost... auto parts vs. aircraft parts. Need we say more?
- Automotive products do not have the burden of getting and maintaining FAA approval.
The comparison you should be making is not Reiff vs. an automotive product, but Reiff vs. our competitors in the general aviation market.
There is only one other company besides us that produces multi-point engine preheat systems for aircraft. The other company's systems cost about TWICE as much as ours, with about half the warranty, and after the warranty expires their parts cost up to 5 times more than ours.
Several companies sell oil sump heaters. Ours costs about the same as theirs, but we give you a lot more for the price. They use silicone pad heaters, but ours is an aluminum unit that is much more durable. And our 5 year warranty beats them all. See FAQ #6.
Our HotPad silicone pad heater is a good product, but good isn't good enough for us. We are passionate in our pursuit of excellence and are constantly striving to improve our products. The HotStrip (introduced 10/1/01) is just one result of our continual product improvement process.
Silicone pad heaters are sold by several companies and widely used for heating aircraft engines. As is true with any product, they have advantages and disadvantages. We made a strategic decision to come up with a better solution that retains the benefits of the pad heaters but eliminates the disadvantages. The primary disadvantage is that they easily overheat if not bonded to a heat sink, i.e. any part of the pad which is poorly bonded will overheat and cause premature failure. This is an inherent characteristic of ALL silicone pad heaters, not just ours. They work great when correctly installed. The installation procedure is not difficult, but it must be done right. If not done right, lifespan can be compromised. This doesn't happen often, but we consider ANY problems to be unacceptable, even if they are caused by improper installation and not a product defect. It is obviously in our customers' best interest, and therefore in ours, to eliminate installation related failures. So we decided to develop a new heater that is easier to install well, and will survive poor installations better.
Most pad heater installation errors result when surface preparation is inadequate, the optimal temperature is not maintained for curing the adhesive, insufficient curing time is allowed, air pockets under the pad are not removed, or part of the pad comes loose during curing.
The HotStrip solves these problems.
Being aluminum, the HotStrip is easier to hold firmly against the oil sump during curing of the adhesive than a floppy silicone pad is. You won't get a corner coming loose.
Being aluminum, it has a much higher temperature limit than any silicone pad has (900oF vs. 350oF). The silicone pad and the HotStrip both operate at about the same temperature bonded to the sump, but the silicone pad is operating much closer to its temperature limit than the HotStrip is. The HotStrip is not being pushed as hard. That means the life expectancy is longer.
In free air (not bonded to a heat sink) a silicone pad will quickly exceed its 350o limit, but the HotStrip remains several hundred degrees under its limit. This tells us that a poorly bonded HotStrip will not overheat like a silicone pad will.
The bottom line is, compared to any silicone pad the HotStrip is easier to install well and will tolerate poor installations better, because it is considerably more durable and operates farther below its temperature limit. For these reasons it should outlast any silicone pad heater, and effectively makes them obsolete.
Our heaters have proven to be so bullet proof that we do not exclude warranty coverage for failures due to improper installation as other brands do.
Two advantages of silicone pads are they are thin and lightweight. The aluminum HotStrip retains these benefits, being only 1/8" thick and 1 ounce. It is also lighter and less bulky than one competitor's thick metal plate heater.
Another advantage of pad heaters is flexibility, so they are still the best choice for applications where the heater cannot be installed on a flat surface. The only engines where this is the case are the small Continentals with oval oil tanks. Consequently, we will not discontinue the HotPad for those engines...at least not until we come up with a better solution for those applications as well. However, we have stopped producing HotPads for engines that are able to use the HotStrip System because we don't want to sell a product that we now consider to be second best.
No. FAA classifies engine heaters as minor alterations, so an STC or Form 337 is not needed, provided the product has PMA approval, which we have. Some preheaters on the market do not have a PMA. In those cases a Form 337 field approval is necessary. Since we have a PMA, only an engine logbook entry is required to document installation.
For more on this see FAA Approval .
There are two reasons to use a thermostat. One is to turn on the preheat system if the ambient temperature falls below a certain level. Our system does not include such a thermostat but they are available from various sources.
The other reason is to prevent overheating while the engine heater is operating. Our cylinder heaters do not have a thermostat control, but some of the oil heaters do. While the engine is running the cylinder normally runs about 300-350oF. Our cylinder heater heats it about 70-90o over ambient, so there is no danger of overheating anything and, therefore, no need for a thermostat.
Our oil heaters are sized to raise the temperature of the oil up to 100o above ambient, and a thermostat on some systems further limits the oil to about 190o actual. This means in normal winter use the thermostat never cycles - it just stays closed (on). This design approach gives you the benefit of a thermostat controlled maximum oil temperature, without the disadvantage of limited thermostat life due to constantly cycling on and off.
One brand does not use a thermostat and criticizes them because they have a finite life expectancy (100,000 cycles for ours) and when they fail they can fail closed (although this is rare - they almost always fail open) and allow the heater to run continuously and overheat the oil. This is a valid concern with some other brands of oil heaters. It is not a concern with ours because our thermostat does not cycle, and because our oil heaters are sized so that they will not overheat the oil even if the thermostat fails closed and the heater runs continuously. In fact, we had to demonstrate this to the FAA to get PMA approval.
The other brand's approach with their multi-point system is to use a low wattage oil heater with no thermostat, which heats the oil 30-50o above ambient. We feel this is not enough heat in cold weather. More heat thins the oil for better circulation and lubrication on start-up and reduces your engine warm up time. A higher wattage oil heater will also give much faster preheating. We believe more heat is better, as long as the oil temp remains at a safe level.
Another thing to be aware of with the other brand's approach to oil heating is that on many engines they use a submersible probe heater in an oil drain hole. We considered using this type but decided against it. Even though it's only 50 watts, the watt density (watts per square inch) is very high due to the small surface area of the heating element. We are concerned about the possibility of the surface temperature exceeding 300o, which would overheat and damage the oil. Our 4" x 1.5" element has more wattage but much lower watt density, so gives more gentle heating of the oil without risk of scorching.
All of our systems are built rugged to withstand extreme hot and cold environments. We use Teflon insulated wiring and silicone coated fiberglass sleeving for high heat resistance and long life. Our heaters have proven to be extremely reliable. In fact, we are so confident in them that we increased the warranty to FIVE YEARS, which is unmatched by any competitor.
Our HotBand cylinder heaters have been on the market since 8/1/96. With about 100,000 units now in the field, they have proven to be extremely durable and trouble free.
The aluminum HotStrip oil sump heater has been on the market since Oct 2001, and prior to that we spent 2 years testing it. Based on the excellent reliability to date with over 30,000 units shipped, we believe it will outlast any other oil sump heater on the market. Due to its metal construction it is much more durable than the flexible silicone pad heaters our competitors use.
Aviation Consumer, March 2001, pg. 18
"[Other brand] loses us in claiming that the top of the cylinder is more critical to heat than the rest of the cylinder."
"As for heating the top of the cylinder being better, we just don't buy that."
"As for bands versus cylinder head plugs, our view is that [other brand] overstates the case in saying it's best to heat the head."
If it really is best to put the heater on the head rather than the cylinder we would. That was one of the options we considered when we developed our cylinder heat system in 1995, and there is nothing preventing us from doing it that way that since their patent expired in 1993. We didn't do it that way because our objective was not to copy the other system, but to design a better one. We accomplished that... and obtained two patents of our own.
The fact is, there is no advantage in putting the heater on the head rather than the cylinder unless there is a valid reason why is necessary to heat the head faster than the rest of the cylinder. There isn't. Like Aviation Consumer, we "just don't buy" the claim that it is more important to heat the head than the rest of the cylinder.
The fact is, our band heaters around the cylinders do heat the heads. Obviously heat from our band heaters conducts both out toward the cylinder head and in toward the crankcase. Our testing of our system and the other brand showed that the cylinder temperature measured at the top end of the cylinder mid-way between their element and ours was the same with both systems. Not surprising since both are 50 watt heaters. They did a test too, but they skewed the results in their favor by measuring the temp about 1 inch away from their heating element.
Here are some infrared images sent to us by a customer. It is pretty clear that the band heater heats the entire cylinder and cylinder head just fine...
"30F outside but after about 8 hours with a sleeping bag on the cowl I had a 100F-130F engine ready to go on an O-320 Citabria and fairly uniform temps...even warming the prop."
For an unbiased evaluation, see Aviation Consumer's tests of both systems.
Another thing to be aware of is that until recently, the other brand's standard system did not include ANY heating element on the cylinder that the factory CHT is installed on. For 30 plus years they had been saying that it is not necessary to heat that cylinder because heat from the other 3 or 5 cylinders will conduct to the unheated one, so it doesn't make sense for them to also claim that our band heater around every cylinder provides inadequate heating of the heads.
The following 2 quotes are from their web site:
Concerning our cylinder band heater, they say:
"It isn't very effective in heating the cylinder due to the heat path to the head. It uses the cylinder barrel, which has cooling fins, as a path for heat conduction."
However, concerning their cylinder head heaters and leaving one cylinder unheated, they say:
"There is some heat transfer from one cylinder head to another by conduction through the crankshaft, rods and pistons. It is possible to heat five cylinder heads on a six cylinder engine and to have the sixth cylinder warmed by conduction."
So, if we got this right, our 50 watt band heater around the base of the cylinder will not conduct sufficient heat to the head (a distance of 3.5") but their 50 watt heater on the ADJACENT cylinder WILL???
That's a very interesting claim, considering that their "acceptable" heat path to adjacent cylinders goes past the same fins that ours does - except instead of just going 3.5" from the cylinder base to the head it goes from head to cylinder to piston to connecting rod to crank shaft (and 2 rod bearings along the way), down 7 inches of crankshaft, and then all the way back up the same route to the unheated cylinder head.
The fact is, if you seal and insulate the engine compartment and allow enough time, their unheated cylinder will be heated by the other heating elements via conduction and convection. However, it is wrong to claim that our band heater on the cylinder won't heat the head by the same processes.
If putting the heater in the head is not "best", does that mean putting it on the cylinder is? We don't feel it makes any difference where the heating element is located as far as heating effectiveness is concerned, and consequently we do not claim that advantage. Other brands shouldn't either. But there are some definite advantages of the band type cylinder heater over the probe type cylinder head heater, such as 1) no conflicts with your CHT's, 2) non-intrusive installation, 3) lower watt density, i.e. spreads the heat over a larger area.
No.
The band heater is a 3/8" wide stainless steel hose clamp placed around the cylinder, and it will dissipate heat just as well as the cylinder itself.
During the development stage we discussed the idea for this cylinder heater with Rick Moffet, Lycoming's VP of Engineering. We specifically discussed the cooling issue, and he had no concerns about cooling. He said the lower end of the cylinder where the band is installed does not generate heat like the top end where the combustion occurs. In addition, he said the cylinder is cooled primarily by splash oil, the air cooling is only secondary. The bottom end of the cylinder where our band heater is installed runs relatively cool because it gets a large amount of splash oil, and it is not dependent on airflow on the exterior surface. In fact, he said the band heater is a better idea than a probe or bolt heater because it spreads the heat over a larger area around the cylinder. A concentrated heat source puts more thermal stress on the metal.
Continental Motors installs our system on their factory remans. Evidently they have no concern about the issue either. Same with Cirrus, Mooney, and several other aircraft manufacturers who install our systems as factory installed options.
The band heater is FAA-PMA approved, which included the prerequisite design approval by their engineering office. They were aware of Mr. Moffet's opinion and agreed with it. If they had any concerns about the bands interfering with cooling they would not have awarded the PMA approval. After approval, if there were any reports of cylinder problems caused by the bands, they could revoke the approval. There aren't any such reports. After 25 years on the market, 100,000 units shipped, and millions of flight hours there are no reports of any cylinder problems.
Occasionally we get this question from someone who fears that heating the cylinders is bad because it may allow the oil in the cylinders to run off, so the cylinders may be "dry" when the engine is started. This is not a concern, because:
- Our cylinder heaters raise the cylinder temperature about 80o above ambient, like a warm summer day. So oil runoff is no more of a concern when preheating than it is when your aircraft is sitting on a hot ramp in summer.
- The cylinders are lubricated by splash oil. With warm preheated oil there is good splash lubrication immediately on engine startup.
- The risk of engine damage from not adequately preheating is well documented, and concern about that should far outweigh any concern about "oil runoff".
There are pros & cons.
Propane fired forced air heaters produce high BTU's. Heat transfers quickly to the cylinders via the cooling fins, so if all you want is to warm your cylinders quickly this is the way to go. Warm cylinders are all you need if your only goal is to get the engine started. However, if your goal is to both get the engine started AND to avoid damage and wear to the engine from cold starting, then the entire engine and the oil needs to be uniformly heated. To do this you need to preheat long enough to allow the heat to conduct throughout the entire engine. You may do this with a propane heater, but the typical 15-20 minute blast of hot air will not do it. Some propane heaters are portable and can be powered from a battery, so you can take it with you when you travel and it can be used in remote locations. However, they weigh 15 lbs or more (plus the LP tank) and take up baggage space. Some flights are not allowed to carry propane.
An electric system like ours is engine mounted and weighs only 1-2 lbs. All you need to operate it is an extension cord, so it is much more convenient to use than a propane or other combustion heater. For operation in remote locations you can use one of the inexpensive generators which are small and light enough to be carried in the airplane, and the generator may be used for other purposes as well, like campsite power. In remote sites you can also power an electric preheat system from a car, truck, or tractor using a DC/AC voltage inverter (available from electrical supply stores).
Safety is another consideration. With any combustion type heater there is a flame, so leaving the heater unattended under or beside your airplane is risky business.
If you would like to have your aircraft ready to go when you get to your hanger, an engine mounted electric system is the way to go.
Overall, we think an electric system is the best way to go for most aircraft owners. We used to make a portable propane heater, but the demand for electric systems is much greater for all the above reasons. That's why we discontinued the portable propane heater and now concentrate on electric systems.
