YouTube - ACIDENTE EMB120 OVER SPEED (dados caixa preta)

This one is played in training over and over and over so you get the point.

 

That sounds like a real CVR?

 

yeah, it is. animation based on actual FDR data.

 

That's horrible. Where was this do you know? That was the one thing that always scared me about that airplane. I remember the first time I read the flight manual with the big red and white stripes on the page that described the prop overspeed and the words "controlled flight may become impossible". The only other time I saw that was on the 737-200 with the rudder hardover. Another scary phenomenon.

 

The accident occurred in Brazil just a few years back. It's been a while so I can't remember all the details. I believe just the two pilots were onboard. The accident was pilot error, though. The pilots were doing 260 knots with the props at MAX (100% Np). They were basically using the props as speed brakes which is a big "no no" in the Brasilia (at least we taught that at Skywest). The limitation on the condition levers at MAX was 200 KIAS. I forget the specifics, but this high speed placed a massive amount of stress on the PCU's. As the airspeed decreased, the load changed on the prop and caused it to go into BETA. This caused the overspeed. An overspeed in the Brasilia is recoverable, but you have to correct very quickly. The trick is to get slowed with flaps and use the manual feather and the electric feather switch to drive the prop towards feather. When I worked at Skywest, this was a memory item. Hopefully, I got the details of the accident cause correct. Maybe somebody else could correct me if I'm wrong.

 

What he said. It was a double over speed condition. The over speed protection worked on number 1 but not number 2. At the end there you can see them over torquing number one as well. 125% or so.

 

Sounds pretty good to me.

 

Scary stuff and sad for those guys. I remember the Saab (been 12 years so a little shady) had several protections for this. The final one basically induced a flameout on the engine which then allowed the prop to feather since it used counterweights not oil pressure to feather. Interesting design.

 

Ya... the Brasilia has something similar, too. It cuts off the fuel flow above a certain RPM. There's a point, though, where the only way to reduce RPM and feather the prop is reduce airspeed quickly without stalling.

 

They call that "fuel topping" in the ATR.