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Collins FMS-3000 - always use APPR mode ?

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Collins FMS-3000 - always use APPR mode ?

Old 08-08-2019, 03:21 PM
  #31  
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Originally Posted by P180 Jockey View Post
Hey, guys and gals- New here, but I do have a question on this:

I agree that the proper procedure is the procedure recommended by the manufacturer. However, in a non-precision approach, using Nav/VNAV to the MDA creates a couple other workload issues:

1) You're gonna have the MDA altitude set in the window and will need to start twisting for the MA altitude at the highest workload phase of the flight (though I agree this is not a huge issue if you "just fly the airplane" on the miss and conduct a SNAP checklist).

2) In A/P mode, the plane is gonna level and stall if you don't have your head out of your butt at MDA, in any case.

So, whether you're flying in Appr/VNAV, Nav/VNAV or Nav/Pitch (dive and drive), you're gonna have to know the MDA and when you're approaching it. That done, it just seems to me, there's two alternatives:

NAV Mode:
Go missed, power up, clean up, SNAP

APPR/VNAV Mode:
Go missed, power up, clean up, SNAP (with the "A" part already set for you, greater precision on the Approach Profile and a single Manual of Arms from Approach to Approach)

What am I missing here? Input welcome.
The simple answer is, if you are shooting an approach to an MDA using VNAV, the aircraft is supposed to level at MDA. Usually this happens a mile or two from the end of the runway. There is no hurry to start a climb in this situation, although if you have no visual and it levels you will most likely be beyond position to land quickly. However, no turns are to be made before the MAP so you have some time.

Level at the MDA, set the missed altitude then hit the GA and start a climb straight ahead to the MAP then SNAP.
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Old 08-08-2019, 05:12 PM
  #32  
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Originally Posted by P180 Jockey View Post
Hey, guys and gals- New here, but I do have a question on this:

I agree that the proper procedure is the procedure recommended by the manufacturer. However, in a non-precision approach, using Nav/VNAV to the MDA creates a couple other workload issues:

1) You're gonna have the MDA altitude set in the window and will need to start twisting for the MA altitude at the highest workload phase of the flight (though I agree this is not a huge issue if you "just fly the airplane" on the miss and conduct a SNAP checklist).

2) In A/P mode, the plane is gonna level and stall if you don't have your head out of your butt at MDA, in any case.

So, whether you're flying in Appr/VNAV, Nav/VNAV or Nav/Pitch (dive and drive), you're gonna have to know the MDA and when you're approaching it. That done, it just seems to me, there's two alternatives:

NAV Mode:
Go missed, power up, clean up, SNAP

APPR/VNAV Mode:
Go missed, power up, clean up, SNAP (with the "A" part already set for you, greater precision on the Approach Profile and a single Manual of Arms from Approach to Approach)

What am I missing here? Input welcome.
The last bullet: how do you think that technique is going to work while on the final approach segment, a stiff tail wind, and then the need to start maneuvering for the landing runway? (circle approach)
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Old 08-09-2019, 04:38 AM
  #33  
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greater precision on the Approach Profile
Does it?

Can you provide a reference for it?
According to Flight Safety, it does for a VOR or GPS approach. You can check with them. I just did.


how do you think that technique is going to work while on the final approach segment, a stiff tail wind, and then the need to start maneuvering for the landing runway? (circle approach)
I submit the exact same sequence might be used; only difference is the MDA/DA will be at the published Circle to Land altitude, which is designed to allow for maneuver to the Landing Runway. VNAV will get you there; Dive and Drive requires you to assure you'll arrive in time to Drive.

My only point here is that a consistent sequence, across approach types, seems to me to be a desirable thing. Whether it's an ILS or a GPS you are required to reconfigure at DA/MDA. If you don't on an ILS, you're going to auger in; if you don't on a GPS or VOR, you're going to stall...and auger in.

So, knowing that you MUST take action at (or approaching MDA), why not fly the (more stabilized) VNAV toward the MDA, initiating the GA decision when applicable? Just like an ILS. Same procedures. Same sequence.

I realize we're talking King Air's here and I'm interloping with discussion of the P180. But I can tell you, the P180 does NOT provide very much forward visibility in the "Drive" portion of a Dive and Drive approach. Here's a great article on why that type of sequence is no longer in favor: From Non-Precision to Precision-Like Approaches


I don't find it curious that Beech might have a different manual of arms on this issue than does Piaggio. Perhaps the P180 is not as well suited to a Dive and Drive approach configuration. Perhaps it simply demonstrates that the experts differ in opinion also. That would mean nobody is wrong. ;-)
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Old 08-09-2019, 05:05 AM
  #34  
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Originally Posted by P180 Jockey View Post
According to Flight Safety, it does for a VOR or GPS approach. You can check with them. I just did.




I submit the exact same sequence might be used; only difference is the MDA/DA will be at the published Circle to Land altitude, which is designed to allow for maneuver to the Landing Runway. VNAV will get you there; Dive and Drive requires you to assure you'll arrive in time to Drive.

My only point here is that a consistent sequence, across approach types, seems to me to be a desirable thing. Whether it's an ILS or a GPS you are required to reconfigure at DA/MDA. If you don't on an ILS, you're going to auger in; if you don't on a GPS or VOR, you're going to stall...and auger in.

So, knowing that you MUST take action at (or approaching MDA), why not fly the (more stabilized) VNAV toward the MDA, initiating the GA decision when applicable? Just like an ILS. Same procedures. Same sequence.

I realize we're talking King Air's here and I'm interloping with discussion of the P180. But I can tell you, the P180 does NOT provide very much forward visibility in the "Drive" portion of a Dive and Drive approach. Here's a great article on why that type of sequence is no longer in favor: From Non-Precision to Precision-Like Approaches


I don't find it curious that Beech might have a different manual of arms on this issue than does Piaggio. Perhaps the P180 is not as well suited to a Dive and Drive approach configuration. Perhaps it simply demonstrates that the experts differ in opinion also. That would mean nobody is wrong. ;-)
Then there is the question is MDA MINIMUM descent altitude or is that just an advisory thing only? Would you stake a type ride on selecting APPR to the MDA?

The airports that I frequent for evals/training all have at least one RNAV (GPS) approaches. I can fly most of these approaches blindfolded. I experiment with the LNAV MDA, LP minima. Pretty much 100% of the time I can acquire the runway environment sooner and be in a better position to land using NAV and VS (1000 fpm max) versus NAV/VNAV. I prefer that my new guys I teach/evaluate use the full automation (VNAV). Guys, that I give PIC rides to will have at least one approach limited to VS. I really throw them for a loop when I dim the FMS brightness full down and tell them to execute me an ILS raw data ;-)

Last edited by Gundriver64; 08-09-2019 at 05:30 AM.
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Old 08-10-2019, 09:39 AM
  #35  
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Then there is the question is MDA MINIMUM descent altitude or is that just an advisory thing only?
I never suggested such a thing. The MDA is a hard minimum; no more excuse to punch thru it or "dip" beneath it than an ILS DA. The only question is the manner by which we get there and what we do when we arrive. To that, I suggest there is no single right answer: evidently Beech does it one way and Piaggio does it another.

Would you stake a type ride on selecting APPR to the MDA?
Pretty certain I would, because i've seen me do it!
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