These heater work exactly as advertised. A simple thermometer left in the engine cowl will tell you what the temperature is. It may take from 8-12 hours to heat a cold soaked engine but once heated it will cycle on/off as needed. The customers who left the low rating obviously did not read the POH supplied with the heater

Twin Hornet 22, 24 VOLT. Unit is very small and makes virtually no heat. Very ineffective in a aircraft cabin. can not imagine inside a cold cowling.

Im normally pretty reluctant to give out five star reviews. It means the product has to be pretty well perfect or its just not worth 5 stars. I purchased the Twin Hornet - 22 with standard electrical plug in to pre-heat my engine in conjunction with an oil pan heater and properly fitted, high quality engine tent. I was skeptical of the device at first, I tried it out at home it put out a pleasant feeling of heat but nothing special. When I tried it in the plane for the first time it was minus 40 Deg C. I gave it 10 minutes to warm up to see how how it would blow and it was barely lukewarm. I figured there would be no way it would be warm enough to start the next day. I came back after 8 hours and I utterly wrong. As soon as I stuck my hand inside the engine compartment it felt almost room temperature. The engine parts all felt slightly cool to the touch but nothing I would be concerned of. I used my temperature gun and the coldest part I measured was 10 Deg C. The engine turned over happily and oil pressure shot up immediately (oil pressure more than likely due to the sump heater). Its of a very high build quality. I feel I could smack it around over the years and it wouldnt crack as its not made of regular plastic and you can feel that. The cord is heavy weight and actually remains flexible at cold temperatures. I wish I could say the same for my sump heater cord. I do actually believe this device is going to last as long as the airplane will, and its comforting to know that it has two of everything and is intrinsically safe. I can leave it plugged in and not worry about it burning my investment to the ground. Ive had sump heaters that spontaneously ignite on the second use. Id still use it in conjunction with a sump heater to get the oil warm and heat the lower part of the engine. However I highly recommended this product. If it can get my engine from minus 40 Deg C up to 10 Deg C, it works.

Use your head when deciding how many watts you are going to use, and what type of insulating cowl cover you are going to combine with the heater and you will not be disappointed. If you are going to use this outside, you will need a top quality custom cowl cover made for the job. I don’t see how the heater itself could be any higher quality. It is EXACTLY as advertised on the website!

Works as advertised and would highly recommend it. I have a Mooney 231 I just throw a blanket over the cowling, close the cowl flaps and plug the air-intakes and turn it on. Start up is no issue and temperatures are up and good to go.

I used this heater in my Bonanza V-35 when I had to leave it parked outside in below freezing temps at a remote Kentucky airport. After overnight heating, the engine was at 70 degrees and started with no problems. I will always use this heater to pre-heat my engine when it is cold. Great product!

After extensive research and phone conversations with manufacturer I purchased 2 Hornets for my Piper Aztec N533KC in December 2016. This plane has carborated engines. Since these heating units are explosion proof and have redundancy in heaters and fans, I feel it is the safest highest quality portable aircraft heater on the market today. While using these heaters I have not had any problem starting my mid time engines. When first turning the master switch on, the engine monators show 6 even cylinder head and engine oil temperature readings. I would purchase again if the need arises.

Does.not adequately heat under the cowl even with blanket and cowl plugs. Has been in use 3 days and still not shut off. I dont believe the temperature ever reached near 70 in the engine compartment.

Does not put out enough heat to do any good. I had it running inside the cowling of my Tomahawk for 6+ hours with two blankets on top, and I could not tell any difference. Engine still ice cold. (OAT 20F.)

Exceptional product and customer support. I had several conversations with the tech support engineers to choose the right product for my airplane. They are responsive, helpful and very dedicated to a quality experience. The heater is incredibly helpful and reliable. I highly recommend everyone use them.