dragonflyerthom
Platinum Member
- Joined
- May 24, 2006
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- 4,742
- Location
- Arkadelphia, AR
- Aircraft
- RAF 2000 GTX SE
- Total Flight Time
- 183FW 132Gyro
Tim O has made a statement that the converted automotive engines are just a step above the MAC as far as dependability on aircraft applications. Now I understand that these engines need to have a redrive and also need to run at higher ERPM in order to create the horse power needed to run the prop. He also said that if you get past the 40 hour mark then you should have a good one. I now have 42 hours plus the 20 hour run in on mine.
Does anyone have or have you heard any horror stories about these engines? What has been your experience with these engines? You can include any experience with this engine in a car. I know I have heard many about the MAC. This should be interesting since there are a lot of Soob engines on aircraft and gyros.
Does anyone have or have you heard any horror stories about these engines? What has been your experience with these engines? You can include any experience with this engine in a car. I know I have heard many about the MAC. This should be interesting since there are a lot of Soob engines on aircraft and gyros.
BARNSTORMER 2 said:Ok, Here is my first shot...
We have 4 kinds of engines to choose from:
1. Certified Aircraft Engines
2. Un-Certified Aircraft Engines
3. Non-Certified Aircraft Engines
4. Auto engines converted for aircraft use
5. (?) Other engines converted for aircraft use.
1. Certified Aircraft Engines are the most reliable engines you can install in a gyro PERIOD. Also, (unless you get lucky) are the most expen$ive engines you can install in a gyro.
Pros: Designed for aircraft use. Many do not use a redive. There is a network that tracks the parts used in these engines and if anyone anywhere finds abnormal wear or problems it gets quickly reported to you (Airworthyness Directives). This also means that you get a COMPLETE history of all service and repairs ever done on your engine and by whom.
Nearly all of these engines have core designs that have been in use since the 1940's and have seen every kind of service imaginable and had the resulting bugs worked out long ago.
Typically operate at a low RPM compared to converted engines. These engines retain their value even when they have many hours on them. These engines also tend to have VERY long life spans. Typically, aircraft engines run several THOUSAND hours between overhauls and it is not uncommon to find a cylinder with 4000, 6000, or 8000 hours on it after being rebuilt several times and engines with the same kind of hours that have been in service since the 1940s.
Many but not all aircraft engines (such as Continentals, Lycomings and replicas) are direct drive and air-cooled which reduce complexity and help lighten the engine.
Most all of these engines have redundant magnetos (don’t require a working battery to run) and ignition systems.
Cons: $$$ Price. Aircraft Engines range in price from about $5k-$20k for the kinds of engines you would typically put into a gyroplane. Also, unless you are an A&P mechanic you will have to have an A&P mechanic work on your engine or at least approve and sign off on your work.
2. Un-Certified Aircraft Engines These aircraft engines used to be certified but now for some reason have had the certification plate removed. These provide all of the features listed above for the certified aircraft engines except they have no paperwork to go with them.
Pro: Typically much less expensive then a certified engine and very likely a dependable engine.
Con: The con is why was it de-certified? If the reason was so it could be used in an Experimental aircraft and the owner wanted to do his own maintenance then you are likely in good shape. However, you should have these engines carefully inspected for Airworthiness Directives before putting them into service.
3. Non-Certified Aircraft Engines These engines are designed and built to be aircraft engines but the manufacturer sells them for use in non-aircraft applications or for use in Experimental and other non-certified aircraft.
These engines are sometimes identical to the certified engines but just without the FAA paperwork. Rotax is a popular manufacturer of this type of engine.
Also, sometimes Lycomings and Continental engines are used in generator or other applications and the engines are retired with plenty of service life left and sold for surplus (Cheap).
PRO: Often cheaper then certified engines and less likely to have a problem then an un-certified engine. Available in a wide range of weight/horsepower configurations if you are willing to fly a 2-stroke engine.
CON: Typically not significantly less expensive then certified engines for the 4-Stroke models. Many models do not have redundant magnetos and ignition systems. Many 2-stroke models have low TBO (Time between Overhall).
4. Auto engines converted for aircraft use. These are typically used (but sometimes new) engines that have been pulled out of a low-mileage car and converted for use in an experimental aircraft. Some engines are converted by hobbyists others are professionally rebuilt and modified for use in aircraft.
Pro: Used auto engines are extremely inexpensive compared to purpose built aircraft engines. Parts are typically widely available and inexpensive.
Many auto engines such as Subaru, VW, Covair and Mazda engines are able to run under the stress of an aircraft application for more than a thousand hours.
Auto engines are so cheap you can often replace the entire engine core for less then the cost of a cylinder rebuild on a certified aircraft engine. If a conversion package runs well for about 40 hours or so it is likely to be a long lived dependable engine.
Some engines such as Subaru EA-81/82 and EJ-22/25 engines are so popular with experimental aircraft builders that there is widespread help and support to assist you in converting and maintaining these engines.
Cons: Auto engines are not purpose built for aircraft applications and are designed for a lower RPM lifestyle. These engines are the least reliable of the engine choices with the possible exception of aircraft drone engines.
Auto engines professionally rebuilt for aircraft use often cost almost as much or more then a non-certified aircraft engine.
Because these engines are running for many hours at or near their operational limits a small problem can quickly become a catastrophic one.
Most converted auto engines require a substantial redrive to reduce the prop speed down from the engines RPM. Redrives and cooling systems add additional weight, complexity, points of failure and cost ( $1500-$4000) to the application.
Auto engine conversions typically have a very low TBO compared to 4-stroke aircraft engines. Auto engines run such high RPMs, especially in draggy applications like gyroplanes, that they often develop problems so quickly that an oil analysis may not catch premature bearing or ring wear before it fails.
5. (?) Other engines converted for aircraft use. These engines would be sourced from snowmobiles, motorcycles, generators, military aircraft drones or other non-auto, non-standard aircraft applications.
Pro: Often the cheapest engine you can get and some are very similar engines to those implemented as aircraft or auto engines. Some drone engines (such as mac’s) can be professionally rebuilt and offer an amazing horsepower to weight ratio.
Con: The least reliable engine unless you have it professionally rebuilt and often takes a significant amount of work and research to convert to aircraft use.
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