Conversion - T2 Limbach

Rev - Jan 02, 2018

 By Jan Zumwalt (EAA #66327)


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ICHER, ZUVERLAESSIGS SPORTLICH, and spar-sam, translates from German into English "safe, reliable, sporting, and economical". This not only describes the engines built by Herr Peter Limbach (EAA 75951) in his motorenbau, or engine plant, near Bonn, West Germany, but it seems to be the motto of his whole operation. Limback Motor has such remarkable workmanship, the German government has certificated 11 variants of his VW engines for use in aircraft!


Peter Limbach (1913-1987) was born in the same building he setup his factory in. He said in 1974 his family dates back a thousand years and used to be robber barons in this area. He got into the VW engine business by doing VW engine rebuilding. At first Volkswagen didn’t appreciate his competition, but later he was able to establish a good working relationship with them. He rebuilt more than 25,000 VW engines and pretty well knows everything that can go wrong: which parts suppliers build less expensive yet reliable spares, and what basic design weaknesses must be corrected. Now, if you want to eat and engine building! rebuilding is your business, you’ve got to find a new outlet. Peter has admitted he had no knowledge of the airplane business in 1969 when he started, but learned quickly.


Without the kind assistance of Volkswagen, it would be impossible for the Limbach engines to exist. The cost of development and manufacture of a new engine from scratch which meets the FAA requirements either in Germany or the U. S. is prohibitive for the small-time operator. Volkswagen provides a short block “kit” from the industrial engine line, one hundred units at a time. By buying a minimum of one hundred, Peter gets a discount. The “kit” includes the housing or block, crankshaft, camshaft, heads with valves installed, connecting rods, and assorted bearings and hardware. This is a bulk shipment and not from the spare parts department. In return Peter must guarantee that none of these components or assemblies will ever be put in a car. The cooperation with Volkswagen is sufficient to permit Peter to specify which parts he wants in the “kit” and a combination of parts from several engine models will be supplied if he specifies them.

Once the short blocks are at the Limbach factory, they are completely checked for airworthiness by a qualified inspector on Peter’s staff or himself. Since 1969 he has not only learned a lot about aircraft needs, but he has obtained the aircraft engine inspector license from the LBA, which is the German equivalent of the FAA. When the modification process begins. Peter prefers mounting all accessories on the flywheel end of the engine and has designed a mounting plate for this purpose. He believes better cooling can be achieved this way and the engine looks more streamlined. He machines a taper for the propeller hub. installs a thrust bearing, and magnafluxes the crankshaft.

Volkswagen Alliance

Volkswagen had previously magnafluxed the shaft prior to shipment and in the future Peter hopes to get approval from the EBA and the FAA for Volkswagen to accomplish all the required inspections on the parts they supply before shipment, thus saving him this expense. The accessory case receives several components from several manufacturers around Europe and in the U. S. The magneto for the single ignition engines is a Slick No. 4030 with the shielded harness. If he is making a double ignition engine, then he uses a Bendix D2000 magneto and high temperature harness which has one drive for two siamesed magnetos. Depending on the installation required or power output desired, Zenith 28RXZ, two Stromberg- Zenith 150CD, or, on the big engine, two Stromberg- Zenith 175CD carburetors are used.

Fig-1: Motor gliders such as the Sportavia RF3, RF4, and RF5
(often used in airshows) are possibly the most popular Limbach users.



Use of an American aircraft carburetor under the engine could eliminate the need for a fuel pump, but, again, the cost would be excessive, and as Peter says, when you are asking for ten at a time, they won’t even talk about a discount”. So, an APG 17.09.OO1A fuel pump is adopted. The starter is usually placed on the accessory pack and is a Fiat 76- 0.5AP (12Vi130 Amp) unit chosen for reliability and light weight. If he mounts a starter gear behind the propeller hub, then a .4HP Bosch Aircraft unit is installed. The alternator is either a Ducati Type 610-12 VoItJl5O Watt or a Ducellier Type 7522-12 Vo1t122 Amp and, again, either driven from the accessory panel or by a belt at the fan pulley end. As they are German engines, Bosch Aircraft spark plugs are used.

Unlike Continental, Lycoming, Franklin, etc., Peter must engineer his engines to work in aircraft already flying or on the drawing board. The manufacturer shows him a drawing and says, space is for the engine”, and then it’s up to Peter to rebuild a VW to fit. As a result, Peter has a large number of different models licensed for installation.

There is a code system like that used by German auto manufacturers to designate car models which is used to describe each of the eight engines presently licensed. Since Sport Avia, a general aviation manufacturer of powered gliders and sport aircraft, initially encouraged his efforts and assisted him in development of an engine for their RF5-powered glider, the first letter designation is S. The second is L for Limbach. The numbers following generally indicate displacement; the next letter is either E for em, meaning one, or D for double, signifying single or double ignition. The next letter is the alphabetical series of the line and, finally, if it has a Roman numeral I, it is designed to accept a variable pitch propeller.

Example: The SL2400 EBI is the 2368 cc single ignition engine which is the second development of this series and can handle a variable pitch prop. The series includes to date:

Model Take Off Power Continuous Power
SL 1700 E and El 68HP@3600RPM 61HP at 3200RPM
SL 1700 EA and EAI 60HP@3550RPM 56HP at 3300RPM
SL1700 EB and EBI 72HP@3600RPM 66HP at 3200RPM
SL1700 EC and ECI 68HP@3600RPM 61HP at 3200RPM
SL 17000 D 65HP@3600RPM 60HP at 3200RPM
SL19000 D and DI 74HP@3600RPM 65HP at 3200RPM
SL2400 EB and EBI 85HP@3000RPM 85HP at 3000RPM
Fig-2: Limbach models


  Continental A65-BF Franklin 2A-110    Limbach SL-2400-EB
Displacment 171ci (2800cc) 118ci (1935cc) 144ci (2368cc)
HP 65@2300 60@3000 85@3000
Weight 167lb 130lb 188lb
Compression 6.3:1 10.5:1 8:1
Fig-3: Comparison with Continental & Franklin
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