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Q400 secrets?

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Q400 secrets?

Old 19th Dec 2011, 21:56
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Join Date: Nov 2004
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Q400 secrets?

Hello again, having been on the Q for a year now, im starting to feel somewhat comfortable with its behaviour and therefore looking for the finer points in regard to operating the aircraft that seem to be glanced over or completely ignored.

Any pointers?

I would ask that we refrain from delving into the FMS as that is just a disaster,(feel like it would be better off without it!)


Thanks!
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Old 21st Dec 2011, 02:58
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You probably know already, but the tail really swings around a lot during power changes and can cause the pax in the rear end a great deal of discomfort if you are ham-fisted with the throttles. It's been a long time, but I seem to remember making slow power reductions in stages alternating with little shots of rudder trim (e.g. from cruise to idle power pull the throttle slowly back about 1/3 of the way while slowly adding rudder, stop, trim the pressure off, pull back the next 1/3 of the way, stop, trim a little more, etc until all the way to idle, or 30% torque, or whatever the target approach power setting may be). The same technique also helped immeasurably in the sim for maintaining heading and track while doing single-engine nonprecision approaches with stepdowns. Just start the power changes during intermediate leveloffs and descents early enough that you can move the throttles gently without blowing your altitudes and speeds.

Just mentally connect your throttle hand to the appropriate foot. They move at the same time at the same rate, with the autopilot on OR off, and of course much more pronouncedly while single-engine. Some guys would leave their feet on the floor with the autopilot on, pull the power back at cruise without touching the pedals, then use trim only to re-center the "trapezoid" as the airplane fishtailed, which you can't feel as much from the front. If you value your customers' comfort keep your feet on the pedals anytime the throttles move.

This of course applies to any large turboprop (or any prop plane period, really) including the DHC-8 100, 200, and 300. But it was my personal experience that the Q400 was much worse in that regard due to it's fuselage length and high power.
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Old 21st Dec 2011, 11:05
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Do either of you astute gentlemen know why the yaw damper allows so much yaw when changing power?

(I know all about the causes of yaw; my question refers to the yaw damper function.)

Hope it's not a silly question!
O8
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Old 23rd Dec 2011, 08:26
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It's been a long time, but if I remember correctly the yaw damper is limited to something in the ballpark of 2~4 degrees of authority either side (my old FCOM is buried in a storage shed at the moment). All it really gives you is lateral stability in turbulence and prevention of lateral PIO. It will not coordinate a turn, it will not bias the rudder in any way during an engine-out, and it will not counteract torque-induced yaw during power changes. It doesn't have enough authority to do anything but stabilize. Thus you should be taught in initial training to keep controlling the rudder with your feet and trim even with the autopilot on. It damps out your own inputs to some degree in normal ops. In the older models the YD was off for takeoff, preventing it from countering YOUR input in the event of an engine failure, and resulting in Vmcg / Vmca problems. In the 400 it was on. I honestly do not know the reason for the difference, whether it was a difference in the system itself or a procedural one (we took the -100 into a couple of very short runways where every drop of performance mattered). Others may be able to give better info on that, either technical knowledge or through comparison of different companies' procedures.

Flew with the YD MEL'd a few times on the old Dash, and the airplane can get into a very dutch-roll-ish kind of fishtailing if you are too heavy with your feet. Makes heavy, gusty crosswinds very difficult if not unsafe.
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Old 24th Dec 2011, 07:13
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Hikoushi is completely right in what he says about abrupt power changes not countered by rudder inputs (be it via trim or via the pedals) - nothing to be added here.

Another little point maybe, as winter is coming up here. Be extra careful when reaching the parking position on a slippery surface; do not allow any ground equipment or personnel near the aircraft until the engines are feathered. You will taxi into the parking stand with both props about at Disk and running at ca. 660rpm; feathering them will take the blade angles from approx. 0 all the way to full feather, passing the normal thrust-producing area and reducing the prop speed to its normal 220rpm in Start/Feather along the way. There is plenty of energy stored in a spinning propeller, so feathering it will give the aircraft a final push, often causing it to lurch more than 1 meter forward on a slippery surface (with the parking brake set!) - and this is a potential killer when ground crew is close by. Often, ground crew is completely unaware of this; I have stopped counting the times I had to have the GPU or the chocks removed again before shutting the engines. Also, for the same reasons, by all means feather both props at the same time under those circumstances - You would not want an asymmetric slide on a narrow parking stand.

One more thing that applies to all aircraft, but has more visible effect on the DH8 due to its lower speeds compared to jets: the proper choice of cruising flight levels can make the difference between an on-time arrival and serious delay. In case of strong headwind at FL250, consider a cruise at FL180 or 190 - this will both result in higher TAS and lower headwind in most cases. Of course, the higher fuel flow in these levels needs to be minded then, although its impact is somewhat reduced by the higher GS.

Also - on the ground, by all means avoid going into the lavatory when alone in the aircraft. Failure to observe this rule has caused many a colleague to be trapped in the loo - if the cockpit door opens approx. 1/3, it blocks the sht house door - you can open it only a few cm any more and there is no way to get out without someone else helping You. Only DH could have come up with 5 doors within 1 m of fuselage length...

Last edited by Tu.114; 24th Dec 2011 at 14:23.
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Old 24th Dec 2011, 13:51
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The Q400 is my favourite among many aircraft.

However, it is also one of the most difficult ones (along with the CRJ200). The performance is immense, and you have to fly the aircraft, or it will fly you.

Once you get to know the Q400 it is a very nice aircraft to fly. The engines are superb and you never have to worry about performance, whether you are on one or two engines.

Cheers

SE210
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Old 24th Dec 2011, 14:13
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Join Date: Sep 2000
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The Q400 is my favourite among many aircraft.
Jesus Christ man! You must have flown a lot of crap then.

Once you get to know the Q400 it is a very nice aircraft to fly. The engines are superb and you never have to worry about performance, whether you are on one or two engines.
If You are lucky and don't get AOG it's nice and stable to hand fly, I'll give you that. Loads of performance yes, until you have to use that stupid icing switch. Whenever we went into LCY in wet or icing conditions we had to leave pax behind.
It's the biggest pile of shit ever designed and I can't wait to get to fly something else.

Last edited by wince; 24th Dec 2011 at 17:50.
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Old 24th Dec 2011, 14:27
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Nice and stable to hand fly - true, but I find one will need muscles of steel when trying this for longer time and/or in bumpy weather... that steamliner steering wheel-sized yoke is such dimensioned for a reason.
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Old 26th Dec 2011, 07:32
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I remember that V1 Cuts without autofeather, and engine failures during a go-around were very "physical" maneuvers in the sim in the Q400. Makes the DC-9 feel light on the controls by comparison!
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