Dash 8 Question

[328dude]

Probebly a stupid question so allow myself to be educated on the intricate workings of the Dash. Sitting behind you guys so often in PIT and PHL, what's the deal with the spoilers deploying when you take the runway. What's that for and do you actually do this on purpose or is in some sort of micro switch in the power levers doing this. Just curious.

 

[chperplt]

I've wondered that myself...

Now a question for you. Do you guys not use full flaps for landing? (40 I think) I've flown in the 328 quite a few times, and have never seen them go to full.

 

[328dude]

We don't at PSA. Increments are 12, 20, and 32. Are airplane is placarded that 32 is for emergency use only. We also don't have any numbers for it so we land with flaps 20. Im not sure of the reasoning behind it. I'll check on it for ya though.
I have flown on the jet version though and they use 32.

 

[Booker]

Sitting behind you guys so often in PIT and PHL, what's the deal with the spoilers deploying when you take the runway.

IIRC, the -100s had ground spoilers installed. Their operation is controlled by a "Flight/Taxi" switch. When in the "Taxi" position, the spoilers are stowed. When in the "Flight" position, the spoilers are extended when the PLs are at flight idle and there's WOW. Hence, when taking the runway for takeoff and the switch is placed in the "Flight" position, the spoilers deploy. Why not leave it in "Taxi" for the takeoff? Again, IIRC, the switch springs to Flight if either PL is advanced above idle.

 

[F4U]

328dude,

That is not a stupid question at all, in fact the procedure we used has changed twice now. So you will see some who do it the current way and others who do it the other way.

There are 6 spoilers on top of the DASH 8. Our company has deactived the two most-inboard spoilers which deploy on the ground only. So with us you will only see 4 spoliers stick up (two on each side).

The two inboard and two outboard roll spoilers serve a couple of funtions. In flight below 140 kts all 4 operate to assist in banking the aircraft. Above 140 kts then the two outboard spoilers are deactivated by the Air Data Computer.

On landing the roll spoilers assume a ground spoiler function.

The roll spoilers ground mode function employs seperate lift-dump valves within the spoiler actuators which when actuated, bypass the servo control valves to supply unmodulated extension pressure for ground mode deployment.

The lift-dump solenoid valves are energiezed at touchdown via power lever limit switches, proximity switch electronics unit (PSEU)(which receives weight-on-wheels inputs from both main gear and nose gear AND the Spoilers Flight / Taxi Switch.

For ground mode deployment to take place the power levers have to be at flight idle; weight on all three wheels, and the flight / taxi switch in the flight position.

A two position flight/taxi switch is located on the Captain's front panel. After landing the flight taxi switch is moved to taxi which overides the ground mode (disabling the ground spoilers). The switch is magnetically latched when in the taxi position. On the ground the roll spoilers remain retracted when the gust lock is engaged.

Just prior to takeoff the flight/taxi switch is moved to flight which also activates the ground mode function of the roll spoilers. Since the aircraft is on the ground and the power levers are at or near idle they pop up. Once the power levers are advanced then a microswitch disables the ground mode function and they become roll spoilers again. If the captain forgets to place the flight / taxi switch to the flight position, then the microswitch on the power levers will move the switch from taxi to flight druing the takeoff roll. Our old procedure said to just leave the switch in the taxi position and check that it moves to flight while advancing the power levers. Our new procedure has us physically moving it to flight when we move onto the runway. Different companies handle it differently so that is why sometimes you will see them and sometimes you wont.

I hope this answers your question.

 

[rightrudder]

328 flaps

at Air Wiskey, we use flaps 32 for landings in our aircraft, but usually on shorter fields and high density altitude. It's the pilot's call.

 

[328dude]

Smoking Man:


Dunna Dunt, Dunna Dunt.

Enjoying your days off are we? LOL


Talk to ya later.