There is, it seems, a fair amount of misinformation, and misunderstanding, regarding the EMERGENCY POWER LEVER AND CESSNA 208 TRAINING. In fact, this is so much so that it appears the best way to approach this topic is to start at the very beginning and discuss what the EPL is, when it should be used, and how to use it.
“I think the first thing that everyone needs to understand,” Dale Wolcott, President of TURBINE TRAINING in Manhattan, Kansas, “is that the discussion of the EPL in regard to King Air 90, King Air 200 training, and King Air 300training is a completely moot issue.”
The reason this is true is because the EPL only has two applications - - the Caravan 208 and the Pilatus PC-12. Both of these are equipped with the Pratt & Whitney Canada PT6A engine. As it’s name indicates, it is to be used only in extreme circumstances, which would indicate that it will not be used very often.
“The thing is,” Jason Wolcott, Vice President of TURBINE TRAINING, “in the rare instances that you do need to use it, you need to know how to use it properly.”
To understand the need for, and use of, the EPL you need to understand the difference between a piston and turbine engine regarding fuel flow. In the piston engine you have a throttle, which controls fuel flow through a carburetor. A turbine engine, on the other hand, utilizes a Fuel Control Unit (FCU). When you determine that you want more or less fuel, the FCU decides whether the engine can handle the change you want. The FCU makes sure you never have an over rich or over lean mixture. In essence, it decides “how soon” you can have the change that you want.
Now, in the rare instance that the FCU fails for any reason (a very rare, but also very fatal occurrence), no matter what you do the engine automatically “fails” to a default point - - usually 48-52%, which is considered “low idle.”
“What you need to understand,” Dale explained, “is that, typically, forty eight to fifty two percent is not enough power to keep the plane in the air. You have to further understand,” he continued, “this may not be a big deal in a two engine plane, but when you have only one engine this a pretty significant issue.”
So, if and when the FCU fails, the pilot takes on the role of being the FCU! With the use of the EPL the pilot controls the fuel flow. This is where proper training becomes vitally essential. The FCU controls the engine exceedingly well, making sure that it doesn’t over-heat. As a result, if the EPL is not used properly the engine can actually flameout - too much fuel too quickly can cause the engine to quit. Proper training will allow a pilot to know how to regulate the fuel flow by reading instrumentation and proceeding properly.