SF340 Flight Director & T/O

[ImbracableCrunk]

Does anyone use the flight director on takeoff?

Just wondering if any other flight/training departments have a different opinion from mine (XJ).

Dear fools who can't figure this out:
No - ExpressJet does not operate SAABS.

 

[ERfly]

When I flew the SAAB (Colgan), the FD was not on for takeoff. I think 400 feet was the lowest you could turn it on.

 

[tindriver72]

Same at Shuttle America, that is when they had them. Why would you want it on anyway?

 

[AutoBus]

Same at Shuttle America, that is when they had them. Why would you want it on anyway?

Hit the G/A button before takeoff and get a solid 10 nose up pitch reference, then you are pretty much perfectly setup for a v1 cut, or any engine failure in the initial part of the climb. there may be some speed variation at first but you will most likely end up somewhere around v2.

 

[Mesabi Miner]

I agree with the statement, "Why would you want it on anyway?" Aren't we capable of pitching up to 10-15 degrees, holding V2+10 dare I say, "Raw Data?" I even feel guilty using the flight director during a hand-flown ILS. XJ's FOM says we have to though. What's next? Just press the takeoff button and watch? But then, management would have to deduct a 19% paycut from the autopilot...

MM

 

[ImbracableCrunk]

I'm a raw data guy myself, as much as possible. That said, some planes I've flown, Citation comes to mind, the F/D is on for departure. I'm sure it's on for many.

I understand we should all be raw-data-autopilot-deferred-aileron+pitch-disconnects-pulled aces. I just wonder why people do or don't use it on the SAAB.

 

[livin'thesim]

If my memory serves me correctly, the Saab AFM states that

Use of the Flight Director information in Go-Around mode is prohibited for takeoff. To me, that implies that using it in VS or IAS mode would be acceptable, at least according to Saab. Whether or not your company agrees is another matter.

That said, there is no good reason for using VS in my opinion because in the event of an engine failure, the FD might have been selected to a rate of climb greater than the aircraft can maintain on one engine.

You could use IAS, but the problem there is that there is no way to preselect an airspeed, unless you have one of the fancy CAT II installations with the programmable speed bug on the left ASI.

That leaves CLB mode, wich does not allow you to set a specific airspeed either.

Some instructors teach the pilots to hit the pitch sync button at V2 to preselect the FD in IAS mode. This is a problem, though, since not all pilots are going to egt it just right, leading to unacceptable variability in results from crew to crew.

Second, if the pilots is late hitting pitch sync, they have selected a much higher IAS that V2. In a critical performance situation, this can lead to level flight or a descent. I've watched more than one crew drive it right into the ground following bad FD information.

My opinion based on a couple years in the sim is that it is better for pilots to just use their raw data skills to get the airplane past flap retraction altitude, then get the PNF to set up the FD correctly when time permits. I have no first hand knowledge to back this up, but it seems to me that the Saab FD is not the same quality as let's say an Airbus or modern Bizjet FD. It's just not quite ready for prime-time. Automation is a tool, not a goal in itself.

 

[Butters]

Hit the G/A button before takeoff and get a solid 10 nose up pitch reference, then you are pretty much perfectly setup for a v1 cut, or any engine failure in the initial part of the climb. there may be some speed variation at first but you will most likely end up somewhere around v2.

Nope. G/A mode is 6.5 degrees up, not 10. Flying 6.5 for a V1 cut would really screw the pooch.

There is no reason to have the FD on during the takeoff roll. You can select it on as soon as you lift off (remember, FD is not AP - no restriction after takeoff other than the G/A restriction ON takeoff).

If you can't takeoff and pitch to 10 degrees until a couple hundred feet off the ground, even in 600 RVR, maybe you shouldn't be flying a Saab in the first place. No offense to anyone, but there is no FD use for takeoff because it really isn't necessary.

(ImbracableCrunk, no slam on you. Just my opinion of the FD. I'm not implying you aren't capable of flying without it! )

 

[ImbracableCrunk]

One more option - PITCH mode. Instructors at XJ are quick to say just pitch up to 10 degrees (8, 9, whatever). What's wrong with Pitch/Heading? Vert Sync at 10 degrees.

Maybe this is why the buttons are GA buttons, not TOGA buttons. Why not then outright say, Use of Flight Director is NOT Permitted on Takeoff?

My guess is there is an oversight somewhere (eg. What is the Max Amps on the gens?) like Livin' said. Maybe this only works with a CatII setup, but it didn't get written in.

 

[Positive Rate]

Hey i thought when you hit the GA button....it goes to the default pitch...but after that you can Vert Sync it? Say a Single engine GA.....or is that what ImbracableCrunk is sayin?

 

[ImbracableCrunk]

Yeah, Positive, you got it right. Pitch is the reversionary mode of GA after you hit the sync. It starts at 6.5 like Butters was saying, but it will capture whatever pitch you sync at, for instance, 10 degrees on a V1 cut.

Maybe useful, maybe not. If it works on some planes, why not on the SAAB?

 

[FN FAL]

What's wrong with pitching up for takeoff attitude and using the CWS button to drop off the command bars at your desired attitude?

I use the FD in the C-208 for take off and it was XJ sim training that showed me to do that as well.

Sure beats the hell out of getting distracted and drifting off into the glide slope antenna on departure.

 

[Alchemy]

Expressjet doesn't have Saabs? But I thought anything smaller than a 737 with a globe on the tail had to be pwned by Expressjet.

 

[livin'thesim]

Reversionary modes.

SF340 trivia. If you hit the G/A button, then push vert sync, you get PTCH mode. What happens if you turn the AP on at the point?
Answer in next post.

 

[livin'thesim]

At AP engagement, FD will revert to VS mode. You can't engage the AP in PTCH mode in any Saab I've flown.

As an aside, I've seen crews flopping all over the place trying to get the FD to command the correct target performance. Fer cryin' out loud, take her to 1000 ft on the big fat ADI they give you. It isn't that hard.

Re: Generators, 600A transient, 400A Cont, if I remember right.

 

[Butters]

Expressjet doesn't have Saabs? But I thought anything smaller than a 737 with a globe on the tail had to be pwned by Expressjet.

Nope. Colgan flies Saabs for Continental as "Continental Connection."

 

[ImbracableCrunk]

As an aside, I've seen crews flopping all over the place trying to get the FD to command the correct target performance. Fer cryin' out loud, take her to 1000 ft on the big fat ADI they give you. It isn't that hard.

It also isn't that hard to pitch 10 degrees up and punch a button if you're trained to do that instead, I should think. I've seen people flop around on heading and pitch just fine without the aid of a flight director.

I think many training departments do things the way they've always been done because that's how they've always done it yada yada yada. Mmmm Dash.

My point is this: Do other operators do things differently than we do it, and does it work better?

For example: Do other operators have the PNF kick on the Y/D after gear retraction? Why or why not?

Re: Generators, 600A transient, 400A Cont, if I remember right.

Yep - but find the 400A Cont. in an XJ Limitation. Last time I looked, XJ thought that 600 transient for 5 mins was the only limit (apparently 599A for days on end is just fine).