Dash 8. How to limit descent speeds.

[Agrajag]

I love my FlyJSim Dash 8 but one thing I still haven't figured out is how to restrict my speed when descending. I'll get an instruction to descend from 16,000 to 5,000 and to stay under 250 knots. The issue often is that by the time I get the instruction, I need to do a >5 degree nose down and suddenly I'm over 300 knots.

 

Using flaps doesn't really work as they retract the instant you go over 200 knots. 

 

What am I missing? Currently my answer is to pull the throttles all the way back and, often, into reverse. FlyJSim says they should never go below 35% during flight. Given that reality I have NO idea how to keep the speed down.

[eMko]

First try to slow down to 250kts, then set the target altitude on autopilot and start descent with speed hold. But I doubt that with 35% thrust you can do 5° descent and stay on 250kts, physics is against you.

 

In the manual there are 3 procedures how to do a descent (all of them works), but AFAIK none is this rapid.

[U2 Fan]

Could you not use your speedbrakes?

[Agrajag]

eMko, which manual? The Dash doesn't have that. Do you mean the X-Plane manual? I do have a VS and IAS button on the AP but the issue there is that the Dash's AP will only allow one control at a time to be engaged. As soon as I touch ALT or ALT SEL for the descent, those would turn off.

 

U2, there are no speed brakes on the Dash, at least none that are mentioned anywhere in the manual or that I've seen any control for.

Edited March 10, 2014 by Agrajag

[eMko]

I mean the FJS-Dash_8_Q400_Manual.pdf which is in aircraft folder\Manuals .

 

For the autopilot, first try to set the target altitude, then begin the descent with IAS button, it should work.

 

Of course may be that I misunderstood your question and we both speak about different models. I mean the one from FlyJSim.

[Nicola_M]

Actually WHICH Dash-8 are you flying?  The FJS payware one does come with a manual, but I think there is an old freeware Dash 8 on the org too which probably hasn't got a manual.

 

If you're using the FJS one, it most certainly does have a manual in with the downloaded acf.

[eMko]

Could you not use your speedbrakes?

 

There are not any on the model. (And if I am wrong and FlyJSim Dash-8 has a speed-brake, then the speed-brake lever is at some kinky place when one would not expect it. Please tell me where it is :-) .)

[Nicola_M]

U2, there are no speed brakes on the Dash, at least none that are mentioned anywhere in the manual or that I've seen any control for.

 

They're called Spoilers on the Dash, and they're automatic.  Switch on the panel directly in front of the pilot, just Flight and Idle.  In flight they're inactive, in Idle they're active on the runway.

For slowing down, you just need to plan ahead.  Reduce throttle until you reach the target speed, and then nose down a couple of degrees until you reach target alt. 

That's what I do.

[SwissCyul]

When you are cruising and you want to descent, you first slow down to about 230 knots. Then you start your descent. Never go beyond -3000 vertical speed!!!!! The real Q400 would not survive a -5000 descent!!!!! While descending leave throttles in flight idle and Prop lever in minimum. Never activate reverse while flying!!! You will end up stalling. And the speed brakes are only ground spoilers. They don't extend in flight, because you would never need them. And on landing they are not to slow down, just to keep the aircraft from going in the air again.

 

Hope that helps,

 

SwissCyul 

[Agrajag]

I own the FJS Dash 8 and have for some time. I have the manual here, and open, and don't see it really discussing how to pull this off. It says this:

 

IAS MODE (momentary action) Click to engage. Activates vertical commands to hold indicated airspeed. Will engage first to your current speed IAS then use NOSE DN/NOSE UP trim wheel to change airspeed. Airspeed being held is indicated on the PFD.

 

2. VS MODE (momentary action) Click to engage. Activates vertical commands to hold vertical speed. Will engage to your current vertical speed then use the NOSE DN/NOSE UP trim wheel to change vertical speed. Vertical speed being held is indicated on the PFD.

 

Again, the problem is, it's disengaging as soon as I set an altitude and the manual points out that only one button can be active per axis (one for vertical, one for horizontal). I suspect I might just have the order wrong as I can certainly set an altitude before take-off, then set an IAS and and then ALT SEL. That works when I then engage the AP after take-off. 

[SwissCyul]

You set your altitude with the altitude knob. Then you press ALT SEL to indicate the plane you want to go there. To climb or descent you can either use Vertical speed or IAS. For VS you click the VS button and then turn the wheel in the middle to set your VS you want. When you have reached your wanted altitude and have ALT SEL switched on VS will turn off and your plane will level off. For IAS it's the same. Select ALT SEL and then press IAS. With the wheel in the middle you can change the speed you want. Then to control the pitch, you simply reduce or increase power. When you have reached your wanted altitude IAS will turn off and your plane will level off. 

This all is of course only possible when the AP is turned on  

[Agrajag]

Hmm... Okay. I just got VS working wonderfully for that, but of course without any speed limitations. I now see where you got your numbers from. 5% descent is way below -3000 so no issues there. I thought I tried IAS for this but clearly didn't. I'll go try that shortly.

[SwissCyul]

Alright

I hope you will find your way through

[eMko]

And there is another point in IAS hold:

 

when you select altitude (ALT SEL), accelerate/decelerate to target speed, press IAS hold button, then you may need to adjust throttles, since Q400 does not have autothrottle. Reduce throttle for descend, add for climb.

 

This point is not always obvious...

[SwissCyul]

Oh, yeah forgot to mention that