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Bombardier Q400's

Posted: Sat Nov 12, 2011 5:42 pm
by AA7771stClass
Took my first flight on Horizon out of SEA the other day and was surprised on both descents how early the landing gear came down - I was curious if this is in lieu of speed brakes of some sort on this aircraft or is just a pilot discretion use to slow it down?

As a side note, I enjoyed both trips. Better than the ATR by a long shot in my personal opinion...

RE: Bombardier Q400's

Posted: Mon Nov 14, 2011 10:44 pm
by jeffreyklm
As the EASA Air Worthiness document ( http://easa.europa.eu/certification/..._Bombardier_DHC--8-05-11022011.pdf ) says in page 11.

Quoting EASA (Source):
VLE (Landing gear extended) = 172 KTS

As this speed is only 45 KTS above the VFE (Flaps extended) and so the average landing speed of 127 KTS, I can only guess it's not to slow the aircraft down, slowing down to those speeds is usually controlled by the Throttle.

I think the gear gets down so early because the pilots get instructed to lower the speed to below the VLE speed, which is the moment they should lower the gear.

Which airports have you flown to? If the airport was busy it might be a reason to slow down to fit in a filled pattern.

Regards.
Jeffrey.

RE: Bombardier Q400's

Posted: Mon Nov 14, 2011 11:42 pm
by sf260
Are you sure about that? From the document you are linking to:
VLE=215kts (and VLO=200kts)
VFE 5º=200kts
VFE 10º=181kts
VFE 15º=172kts
VFE 35º=158kts

All these speeds are IAS, so lowering the gear can certainly be used to slow down every now and then. When on descend, throttling back may not be effective enough to slow down (rapidly enough), so I can imagine they also lower the gear early sometimes...

Maybe an airline pilot can shed some light on this, what are the reasons for -earlier than normal- extension of the gear, other than to slow down?

[Edited 2011-11-14 15:44:27]

RE: Bombardier Q400's

Posted: Tue Nov 15, 2011 7:27 am
by jeffreyklm
Perhaps it is yes.

But just a Quick point out; I don't think it's coincidence that gear VFE15 and VLE are both 172 KIAS.
I believe it was just a part of the checklist when they have been instructed to reduce speed to a certain velocity when they had flaps 15, were in the pattern and instructed to slow down.

I know it's a different conclusion than my previous post but I've been thinking about it for some time.

Jeffrey.

RE: Bombardier Q400's

Posted: Tue Nov 15, 2011 1:06 pm
by Fabo
While the current trend is to keed the gear up as long as practicable, with airliners routinely lowering gear at about 4-5 navy miles out the runway due to noise concerns (originally, the idea was to have the airplane in landing configuration as soon as you begin final descend), it might be, that this particular type is pretty much unable to slow down & go down at the same time, leading to a situation that would require gear down before the point of final descent (also known as FAF, if you wish to look at approach charts for that particular airport) - that said, I do not know Dash 8 as to confirm or deny that.

Jeffrey, your cited speed of 172KIAS is valid for 100 through 300 versions, as correctly pointed out, for 400 it is 200KIAS Vlo and 215 Vle, which allows for sooner extension (useful in cases where you came in hot&high, lading gear makes for an excellent slow down device)

One more thing that crossed mi mind, once again, I do not know about Dash8, but with some propeller aircraft (although typically, that would be direct drive turboprops, that DHC-8 is not, to my knowledge), you might be limited to some forward thrust while in air, that would make it that bit more difficult to slow down.

RE: Bombardier Q400's

Posted: Tue Nov 15, 2011 5:21 pm
by Flighty
Quoting Fabo (Reply 4):
it might be, that this particular type is pretty much unable to slow down & go down at the same time, leading to a situation that would require gear down before the point of final descent (also known as FAF, if you wish to look at approach charts for that particular airport) - that said, I do not know Dash 8 as to confirm or deny that.

Would it be any concern about Q400 gear performance in particular? (That's been raised...)

RE: Bombardier Q400's

Posted: Wed Nov 16, 2011 4:08 am
by AA7771stClass
I flew from Sea/Tac to Pasco (KPSC) and back. There wasn't any other traffic around Pasco at all; returning back to SEA was obviously busier.

RE: Bombardier Q400's

Posted: Wed Nov 16, 2011 2:14 pm
by lit727DL
I'm actually in near PSC now and will be here for a while longer befor returning to LIT. I've had the oportunity to fly the Q400 to SEA several times and the gear does seem to come down early but I have no clue why. Love flying on the Q400 but this is the only route where I have done so, don't have anything else to compare it to.

RE: Bombardier Q400's

Posted: Thu Nov 17, 2011 2:54 am
by GRZ-AIR
A little bird once told me that the Q400 doesn't have speed brakes, and contrary to its smaller sisters (Q300 . . .) the props are aerodynamically very efficient. Whilst you could easily slow down a Q300 by idling the throttle, the Q400 will not really slow down doing the same while descending. You could, off course, always put the props to max rpm, but on the Q400 it is SOP (except for low vis etc..) to land with reduced RPM, so you don't really do that. What's left to give you a good rate of descent and to help you slow down is the drag from the extended gear with its long struts. It is actually a nicer procedure than e.g. undershooting the glidepath, leveling off (pulling pitch up) to bleed off speed and then ducking down again with the glideslope. By using the latter "technique", paired with a gear extension, some pilots have managed to keep the speed up to around 240kts until 5 miles before the runway, and still perform a stabilised approach by 500ft AGL.


regards, GRZ-AIR

RE: Bombardier Q400's

Posted: Thu Nov 17, 2011 7:44 pm
by DashTrash
The 300s don't slow down as fast as you claim. At lighters weights, they slow easier, but I've watched many newhires get their lunch eaten by heavy -300s. When the props are at 900RPM (cruise) they are damn near feathered and don't produce much drag. Push them up to MAX, and they turn into parachutes at idle.

For the older series standard is gear before flaps. Vlo and Vfe5/15 are the same speed in the 100s/200s, and close enough in the 300s. Sounds like it's the same for the 400s.

RE: Bombardier Q400's

Posted: Thu Nov 24, 2011 6:30 pm
by GRZ-AIR
Well, in a Dash, what you see below, you can land on. Can't do that in an Airbus or a Boeing  .

rgds G

RE: Bombardier Q400's

Posted: Thu Nov 24, 2011 8:43 pm
by alasizon
As someone who flies the QX Q400s quite often, I can say it all depends on the airport. Also, for airports like LWS, PSC, PUW, EAT and others where the final approach (or final turn into the ILS if available) is quite short and/or since the Q400 is moving so slow, it can afford these turns, the gear is sometimes lowered earlier in order to provide the pilots time to account for the approach and be aware more of the approach and not have to worry about the gear being down at a certain point.

RE: Bombardier Q400's

Posted: Fri Nov 25, 2011 8:20 am
by GRZ-AIR
Quoting Alasizon (Reply 11):
since the Q400 is moving so slow, it can afford these turns, the gear is sometimes lowered earlier in order to provide the pilots time to account for the approach and be aware more of the approach and not have to worry about the gear being down at a certain point.

Uhm...not really. You don't lower the gear early out "to not worry about it anymore at a later point". What do you mean by "it can afford these turns".

Being radar vectored a q400 flies the same speed as do all other planes. The q400 is not moving slower than other traffic during radar vectors. The speed range will be from 250 to 180.

You lower the gear in order to be stabilized at around 500-1000ft AGL. So no matter how long or short your final approach is, the gear comes down at the same point.

The question here was why you would lower the gear further out. You do that to have more drag to increase your descent rate or reduce speed.

RE: Bombardier Q400's

Posted: Sat Nov 26, 2011 4:23 am
by alasizon
Quoting GRZ-AIR (Reply 12):
You don't lower the gear early out "to not worry about it anymore at a later point"

Correct. I wasn't clear in my first post. I was referring often to airports where you are around 800-1500 AGL and still have a turn to line up with the runway (LWS is a perfect example).

Also, with first hand experience, I can also say that the reduce speed method is often the reason. I know I've had approaches where the gear was used to slow the aircraft down (along with the flaps).