Dash 8 single engine approach.

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smashmouth
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Dash 8 single engine approach.

Post by smashmouth »

Talking to a buddy just training on the Dash 8. Tells me that the autopilot can not be coupled on a single engine approach. WTF? Isn't that when the workload/stress would be little higher? Is that a certification thing like a lack of auto rudder trim? Or maybe is the manufacturer afraid of American Lawyers.

Would this limitation include using the HDG mode on a Non Precision approach and fly it old school?

Anyone?

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Re: Dash 8 single engine approach.

Post by aileron »

Certification, so they say, was rushed (e.g. no ground inhibit of nuisance warnings/cautions) for the Q400. There is no "Third Axis" control by the autopilot and as such the autopilot cannot "fine-tune" the approach mode with single engine ops.

There is no limitation to using the flight director, if that is what you meant with your last paragraph, but it must be hand flown... so you don't have to go "old school" (raw data) with ILS approach mode (and no you don't have to revert to "stone age" Non Precision).
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Re: Dash 8 single engine approach.

Post by Canoehead »

The -100 and -300 (301/311) are not certified to fly any type of single engine approach coupled to the autopilot.

Not sure about the 200 or other -300's (314/316 series etc...)
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Re: Dash 8 single engine approach.

Post by Cat Driver »

Am I missing something here?

Why would two pilots choose to let the auto pilot fly a single engine approach in any twin engine turbo prop airplane?
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Re: Dash 8 single engine approach.

Post by ei ei owe »

Cat Driver wrote:Am I missing something here?

Why would two pilots choose to let the auto pilot fly a single engine approach in any twin engine turbo prop airplane?
For the same reasons that 2 pilots would let the auto pilot fly 2 engine approaches. What's the big deal?

If the Dash can't/not allowed to do it, so be it.
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Re: Dash 8 single engine approach.

Post by Cat Driver »

I guess I'm just old school.

There actually was a time when pilots thought nothing of hand flying any approach, but maybe our airplanes were easier to fly then.

I have never flown a Dash so for all I know about it it might take three pilots to fly it on one engine.
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Re: Dash 8 single engine approach.

Post by smashmouth »

Does the Dash 8 have any limitation to climb/descend Single Engine with the autopilot engaged? How about changing direction? I highly doubt it, so what is the difference in descending in VS mode and HDG mode on a non precision approach? You are just using the flight director as you would in any other phase of flight.

If the limitation is written as " the autopilot cannot be coupled for a S/E approach" I guess the limitation is in the definition of "coupled". A coupled approach would be one with a navaid supplying azimuth data...ILS or VOR, and selecting the corresponding selection on the panel. Am I wrong? Or is coupled meant to indicate that the autopilot is engaged? If the autopilot is just following commands from the flight director set by the pilot, is that also "coupled"?

Just asking, don't hate.



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Re: Dash 8 single engine approach.

Post by HuD 91gt »

Cat, because humans make mistakes. I don't care how skilled you are at flying an airplane, a good autopilot will out fly a pilot 9 times out of 10. Especially under stress. That old school mentality could get you into trouble one day. For someone who always praises safety, it's a comment I had to bite on. I know your looking for an argument.
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Re: Dash 8 single engine approach.

Post by Cat Driver »

No I am not looking for an argument, I probably should not have made the comment in the first place..

I am well aware of the reliability and accuracy of modern auto pilots I just sometimes lapse into an era long gone.

For what it is worth the last landing I did in an airplane the day before I retired was an autoland as we were very tired after two long delays caused first on departure from Amsterdam by a mechanical delay then a drunk passenger problem in Bodrum Turkey...so of course I understand modern auto pilots.

Now I will drop out of this self made error in commenting without first thinking it through properly. :mrgreen:
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Re: Dash 8 single engine approach.

Post by vanishing point »

Our SOP states the a/p shall not be used for a single-engine approach. You can use the flight director in LOC/GS mode all you want but no coupled a/p.

Another interesting item; the a/p is not to be used on a BC approach in NAV mode either. We can use the a/p on a BC app in HDG and VS or IAS mode.

You'll have to talk to DeHavilland about these items.
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Re: Dash 8 single engine approach.

Post by Jack Klumpus »

I believe this matter will be changing in the future. The S/E approach to be flown using auto-pilot to a tad later in the approach.
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Re: Dash 8 single engine approach.

Post by teacher »

Set 40% +/- a bit on the torque and it'll fly an ILS really well. Like the guy on infommercial says, "set it and forget it" within reason of course :wink: . The more you play with the torque the more the rudder needs trimming.
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Re: Dash 8 single engine approach.

Post by Bank Angle »

vanishing point wrote:Another interesting item; the a/p is not to be used on a BC approach in NAV mode either. We can use the a/p on a BC app in HDG and VS or IAS mode.
Of course you can't use the autopilot on a BC in NAV mode. The autopilot does not recognize the configuration of you HSI, meaning the fact that you set it up backwards to give you the correct left and right deviation, and hence will steer the wrong way for a deviating LOC needle! Been there, tried that (after a long tiring night)...
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Re: Dash 8 single engine approach.

Post by fish4life »

but you can set the auto pilot to back course mode...
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Re: Dash 8 single engine approach.

Post by oldtimer »

I read something a couple of years ago whereby Horizon/Alaska Airlines got FAA approval to conduct CAT 11 coupled approaches single engine in the Q400. For one thing, that allowed No ALternate IFR. Just a comment from my poor memory.
With the King Air 200, an unapproved and forbidden procedure that worked reasonable well was a coupled ILS (CAT 2 runway) to 50 ft, power levers to idle and hit go-around on the flight director. I tried it once under perfect conditions and it worked. But the thumb was on the big red disconnect button. The chief pilot sent a memo to all pilots that it was a forbidden procedure but pilots will be pilots. I never had the necessity to attempt a couples approach single engine. I always handbombed all single engine training flights but never to ILS mins. Always became "visual" at circle to land mins.
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Re: Dash 8 single engine approach.

Post by Raybanman »

The limitation a stated in the afm is a SE coupled approach. You may still use the autopilot while in HDG mode. Coupled approach means an approach where the autopilot is coupled via the NAV, VOR/LOC, AUX or APP mode. HDG mode is not coupled to the approach mode and will not mask trim changes. The autopilot cannot be set to any kind of BC mode. It does not reverse sense. Try it one day if you don't believe me. It will Intercept with a wrong way turn.
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Re: Dash 8 single engine approach.

Post by Cat Driver »

The more you play with the torque the more the rudder needs trimming.
I don't quite follow this statement, do you mean as you change torque differentially you " trim " rudder with your feet or do you actually use the rudder trim?

As I said I never flew a Dash 8 and these things are really arousing my curiosity.


I always handbombed all single engine training flights but never to ILS mins. Always became "visual" at circle to land mins.
I had a very tense trip many years ago in a DC3 with one feathered and was forced to do the approach in zero, zero in ice fog.....thankfully I had been trained well in my past and was able to safely land it. And it did have an autopilot but we did not have it engaged.
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Re: Dash 8 single engine approach.

Post by teacher »

Cat Driver wrote:I don't quite follow this statement, do you mean as you change torque differentially you " trim " rudder with your feet or do you actually use the rudder trim?
Well, yes. If you power up the good engine will the aircraft not yaw towards the dead one? I found on the dash (and stated in our AOM) that if you bring the power back to 40% (or so) torque and trim the rudder properly (for straight flight) you can fly an ILS with minimal power adjustments and therefore none to little yaw from being single engine. It becomes hard to get stable if you keep increasing and decreasing power on your remaining engine does it not?
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Re: Dash 8 single engine approach.

Post by Cat Driver »

It is basic aerodynamic principals that if you change thrust on only one engine in a normally configured twin with the engines on the wings it will produce a yawing movement, which you need to compensate for if you want to eliminate the undesired yaw....it can be done with rudder input using your feet or by rudder trim.....if you are constantly adjusting torque on only one engine the adjustments will be in direct relation to the amount of torque change and its percentage of thrust change.....

....so back to my ignorance of how one does it in a Dash 8, do you let the auto pilot take care of it or do you do it yourself by moving the appropriate flight control/'s?
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Dash 8 single engine approach.

Post by Dhc6to8 »

All Dash 8 aircraft can be flown single engine on approach (regardless of minimums) with the autopilot on... however, all models and sub variants of the Dash 8 are not certified for this application of the autopilot. The reason Horizon is allowed to fly coupled single engine is because both pilot stations are equipped with HGS, so the Cat II approach can be monitored by both pilots- if, they are hand flying the approach then Cat IIIA minimum is still allowed because of the installed HGS. Single engine approach in all variants of the Dash 8 are hand flown once passed the FaF or 1000 feet AGL above the OM crossing altitude, whichever comes first. In reality, I have flown a close to 0/0 approach once single engine into YVR using the autopilot until the Rad Alt called 20 feet... no problem, touchdown footprint within the touchdown zone... the only real danger doing this is that with the manual reduction of the torque setting the aircraft will oscillate in pitch to a point where a potential tail strike may develop if the main gear oleos are compressed at touchdown and the right alpha angle is reached. However, all variants of the Dash 8 aircraft require trimming with each and every single power change; the Q400 even more so. The flow to move the hand from the throttles to the trim switch becomes automatic upon the first flight or two. High alpha flight magnifies this tendency on the Q400. It is recommended to train autopilot-on coupled single engine approaches on all variants. I know of one episode where a junior new hire First Officer flew an approach to 50 feet AGL single engine successfully with the autopilot coupled due to a complete incapacitation of the Captain.
A good rule of thumb while flying around single engine on any variant of the Dash 8 with the autopilot engaged is to trim manually with the feet, especially on approach.
Bombardier could have really cleaned things up by completing the full certification of the autopilot system on all variants of the Dash 8 family including increasing the certified speed limits of the Q400 by certifying the windshield for higher speeds... but then again, Bombardier always "nickels and dimes" their customers to death with every option and expanded certification limits that come...
Good aircraft otherwise and an important "step" for young pilots to learn how to handle a rather complex and demanding machine....
I really hope that the Q400X will see the light of day sometime soon... de-rated engines, extended fuselage, strengthened main wing box, plus beefed up gear.... now, that would be a hotrod...
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Re: Dash 8 single engine approach.

Post by Raybanman »

Sorry Dhc6to8, not all variants are certified for SE coupled (AFCS modes: V/L, AUX, MLS, APP) autopilot approaches. You may be able to pay for a supplement for it, but as standard, the -100 and -200 are not. I wouldn't be able to tell you, for sure about supplements because it seems you can pay for whatever you want if you can prove it works. I've never flown a -300 or -400 so those may be much fancier than I'm used to. You can leave the Autopilot on until you capture the approach, but it has to be off before it captures. FD can stay on and you hand fly. For a non precision approach, (back course included) you just fly with heading bug and V/S or IAS with autopilot on if you want. Again, all I know about is the -100 and -200.
....so back to my ignorance of how one does it in a Dash 8, do you let the auto pilot take care of it or do you do it yourself by moving the appropriate flight control/'s?
Cat, the Dash autopilot has no yaw control channel so you step on the good engine just like all the other airplanes in the world. Then you trim with rudder trim. There is a lot of rudder trimming that goes on in the Dash (-100 anyway), pretty much anytime you change the power even with two stoves going. Most everyone I flew with on the Dash 8 hand flew whenever we felt like. It flies great :)

Cheers,
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Re: Dash 8 single engine approach.

Post by Dhc6to8 »

Hi Raybanman, I stated in my post:
all models and sub variants of the Dash 8 are not certified for this application of the autopilot.
That includes the 100 (which you are flying).
In reality, you can leave the autopilot on during approach (on all variants) even though it is not certified for this. However, you must manually trim the rudder by hand and then maintain the yaw using your feet. I worked for Bombardier during the initial certification of the Q400, and I have flown every model of the Dash 8 family that has been produced. Next time you are in the simulator, try it out. The biggest secret is that it works, but since it is not certified most operators tell their pilots to always disconect the autopilot prior to approach mode capture ( I am talking about ILS/non precision front course approaches). Coupled FMS approaches are even possible single engine, these can be great for non precision appraches because you basically turn the approach into a continuous decent ILS with minimums rather than a step down approach with MDA. Cool stuff and makes non precision approaches a breeze...
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Re: Dash 8 single engine approach.

Post by Raybanman »

Sorry, missed that part. I know it works, was just trying to help clear up the origonal poster's question. I no longer fly the dash, so my knowledge is probably somewhat dated anyway!

Cherrs,
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Re: Dash 8 single engine approach.

Post by justwork »

From what I have heard Bombardier will be making a change to the AFM and allow the autopilot to fly a single engine approach until 1000 AGL, then it's hand flown using the FD. It is really a non event, as long as you get the aircraft configured early, and don't mess with the power on the approach. Like someone said, set it and forget it.
Cat Driver wrote:It is basic aerodynamic principals that if you change thrust on only one engine in a normally configured twin with the engines on the wings it will produce a yawing movement, which you need to compensate for if you want to eliminate the undesired yaw....it can be done with rudder input using your feet or by rudder trim.....if you are constantly adjusting torque on only one engine the adjustments will be in direct relation to the amount of torque change and its percentage of thrust change.....

....so back to my ignorance of how one does it in a Dash 8, do you let the auto pilot take care of it or do you do it yourself by moving the appropriate flight control/'s?
Cat, the Dash 8 is a unique twin engine turbo prop. Lots of power and the engines are relatively far from the vertical axis, so any change in torque will cause substantial yaw when flying single engine. Unlike a jet, it only takes a movement of about 1/4" on the power levers, when low level, to achieve large torque changes. It takes practice to dial this in. Cat, like any plane, you apply force on the control surface and then trim it out. A dash 8 in all stages of flight, autopilot engaged, takes fine tuning on the rudder trim any time there is a power change or change in airspeed, for all the autopilot knows there isn't a rudder on the airplane.

As long as you've got the airplane configured early you wont have to make large power changes, as long as you're not making large power changes a single engine approach in a Q400 with the FD is a non event. I would bet that more people would screw it up if they allowed the autopilot to fly it to 200 feet.
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Re: Dash 8 single engine approach.

Post by North of You »

[/quote]

I had a very tense trip many years ago in a DC3 with one feathered and was forced to do the approach in zero, zero in ice fog.....thankfully I had been trained well in my past and was able to safely land it. And it did have an autopilot but we did not have it engaged.[/quote]

Sounds like you busted minimums on that approach, or is there a Cat 3 certified DC3 out there I haven’t heard about? Or is there a let in your SOPs that allow you to descend below minimums in the event of an emergency? EDITED - PERSONAL ATTACK
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