Dash 8 Beta question

[legaleagle]

I was on a Dash 8 from GSO to DCA last night, and I thought I would ask a question as a passenger with a commercial rating (albeit low time). We had the gear down, flaps were out, and we were turning right base on the River Visual/ rwy 19. All of a sudden, I heard a sound that would normally be associated with beta range, and the plane literally almost lurched as we slowed down and the pilots stuck with it for another 15 seconds or so, while still at about 2000 or so. I have seen other threads that have suggested that while it can slow you down, if you are fast, going into beta can be dangerous if you lose an engine, particularly when slow on final. But, I wasn't as concerned about safety, I was just curious if a lot of the 121 ops allow that? It seems that most 91 and 135 manuals that I have seen don't specifically exclude it, but being that 121 seems to be the ultimate attempt at regular, predictable operations, I was surprised that going into beta or reverse is allowed in flight. Excuse my naivety.

 

[Bluto]

Let me start by saying that I don't fly a Dash. On the Brasilia, which I believe has the same engines as the short Dash's, what you experienced would probably be someone going abruptly to Max on the condition levers (like going prop full forward/max RPM) The abrupt increase in drag from the flat prop blades can make you decelerate pretty rapidly. Most commercial aircraft have limits that keep you from using beta thrust inflight.

 

[legaleagle]

Oh yeah! I forgot about the props to max....Jesus, I have my head stuck up my ass. Thanks Bluto.

 

[Dash8]

in the dash you don't have to put it at 1200 to get that effect,
just pulling the power levers back to the stops turns those blades into giant barn doors out there, causing plenty of slowdown and a fair amount of noise depending on the airspeed
dash is a sweet plane, she'll do lots of stuff you ask of her

 

[CitationLover]

our beech passengers get the same feeling as we have to slow down due to the dashes in front of us.

it sounds like it is the props "flattening" with a reduced power setting. probably the were dumped high. or another explanation would be bringing the props forward as part of a before landing checklist. in the beech if we shove the props forward, you will be pressed into your harness.

 

[Dash8]

our beech passengers get the same feeling as we have to slow down due to the dashes in front of us.

mmmm, yup, gotta love paid by the hour, block or better

 

[tenfore]

From someone that knows - this is what I was told.

Using the beta range during flight is extremely dangerous and it is extremely unlikely that this is what occurred. In addition to a protection gate the beta range is slightly spring loaded below Flight Idle. What happens when you select the beta range is the propeller stops being driven by the engine and starts being driven by air pressure. This may sound gentle, but it is anything but that. Even the slightest amount of neutral pitch (doesn't even need to be negative) will spin those props to 1400+ RPM and fry every turbine blade in the engine.

 

[FN FAL]

Even the slightest amount of neutral pitch (doesn't even need to be negative) will spin those props to 1400+ RPM and fry every turbine blade in the engine.

Said kinko the clown, this doesn't...