Year 2000

The Walter 601 turboprop engine has earned a distinguished reputation for reliability and durability.

The Walter factory in the Czech Republic attributes much of the credit for this accomplishment to their auto-start and electronic limiter system, which is installed on commercial and airline versions of the engine.

Aerocomp, Inc. offers the limiter as a recommended $6500 option on Walter 601 turboprop firewall-forward packages. Our prototype Walter-powered Comp Air 7 factory demonstrator, Comp Air 8, and two turboprop Comp Air 10 aircraft were not fitted with this system. The owner of the prototype Comp Air 8 has since elected to retrofit the limiter to his airplane, and is now using it regularly.

As our experience with these engines has increased (7 Walter-powered aircraft now flying successfully, and over 20 others under construction), Aerocomp Inc. has gained confidence in the value of the Walter limiter system.

Starting a Walter turboprop engine is not difficult. There are actually fewer steps involved in starting the Walter
turboprop engine than most piston aircraft engines. A competent pilot should have no difficulty lighting the engine successfully.

Unfortunately, if the pilot is distracted during the starting sequence, and fails to detect a "hot start" (over-temperature condition), the alloys used in the engine could be permanently weakened

by excessive heat, leading to engine failure. The most likely scenario for a "hot start" would be an in-flight restart attempt following inadvertent fuel starvation (typically resulting from fuel tank mismanagement). Other times when a "hot start" may be more likely would be during engine starts on an already warm engine (i.e. second or third engine start in a short period of time).

If the limiter system senses an impending over-temperature condition, it will shut down the engine safely before any damage occurs. This added protection significantly increases the value of a Walter turboprop.

Some externally visible electronic components
of the Walter Autostart/Limiter system

This is where the value of the limiter system becomes apparent. The commercial operators using Walter engines for scheduled and passenger-carrying flights equip their engines with the auto-start and electronic
limiter system, because the system automatically assists the pilot in monitoring critical engine parameters during start-up. The limiter system monitors Inter-Turbine Temperature (ITT) during start, and automatically meters fuel to the engine appropriately, preventing an over-temperature condition from occurring. We've found that maximum starting temperatures are usually about 100 deg. F. cooler during computer-assisted autostarts, because the limiter system controls the fuel supply to the engine more
precisely than can be achieved manually.

With the autostart system, once pre-start checks have been completed, the pilot merely needs to switch on the autostart system and advance the fuel lever. He can then focus his attention on monitoring relevant engine gauges.

In summary, we have demonstrated that the Walter 601 engine can be operated safely without the autostart limiter system. After doing so,
however, we have grown more
convinced of the value of the limiter system, and we now recommend it as a means of protecting the engine from serious damage during startup. The limiter system is excellent insurance, and contributes significantly to the outstanding reliability of the Walter 601 turboprop engine.

"The limiter system is excellent insurance,
and contributes significantly to the outstanding
reliability of the Walter 601 turboprop engine."