Coupled Approach Altitude Bug

[Flying_Goat]

Had a lot of great responses on my last post. Here’s another for the crowd….

How’s everyone managing altitude bug on coupled precision and non-precision approaches? It’s my understanding and (limited) experience that once GS/GP is captured, AP will prioritize that over selected altitude. So what are your preferences with the alt bug at this point?

Bugging DA/MDA as a reference? Bugging initial straight ahead climb-out alt for missed? Full missed procedure altitude (assuming a climbing turn after initial climb out)?

 

[midlifeflyer]

Final missed approach climb altitude.

That’s SOP on approaches with vertical guidance. You might even see it as the recommended procedure in your AFMS. On approaches without vertical guidance, there have been recommendations to enter the MDA, but I personally never saw why.

I don’t see a reason for using the initial missed altitude or any climb altitude you are not going to level off for.

 

[MauleSkinner]

On approaches without vertical guidance, there have been recommendations to enter the MDA, but I personally never saw why.

Depends on equipment, maybe. Or the level of automation you want to be comfortable with. In my world we set the altitude “bug” to allow the automation to level you off at the MDA.

 

[RussR]

For anything with a DA, or vertical guidance and a DDA, or when using MDA as a DA, the bug gets set to the missed approach altitude. That's SOP.

For anything with an actual MDA where you plan to level off, then the big is necessarily set to that MDA.

 

[Flying_Goat]

That’s SOP on approaches with vertical guidance. You might even see it as the recommended procedure in your AFMS.

Not necessarily true in all cases. GFC 500 AFMS says to set missed approach altitude for ILS. For LPV it’s not super clear.

For non-precision approaches it has you setting alt to next step down level. However, if you are coupled to advisory glide path then it’s not necessary and you can bug it to something else.

In my world we set the altitude “bug” to allow the automation to level you off at the MDA.

If I’m not mistaken, if you are coupled to GS/GP the AP will level off wherever you are if you press ALT thus making bugging MDA unnecessary except as a visual reference.

I know there black and white instances, but there are some grey areas that seem to be dealer’s choice.

 

[midlifeflyer]

For anything with an actual MDA where you plan to level off, then the big is necessarily set to that MDA.

I know that's been a recommendation forever but I never saw a good reason (let alone a "necessity") for it in any system where you set an target altitude. If I break out I'm going to land so I don't care. If I go missed I'm going to climb so I want my target altitude ready to go. If for some reason it's the <1% of the time I need to level off at the altitude I've been vocally counting down to for the last 5 minutes or so, that's one button.
@MauleSkinner?

If I'm not mistaken, if you are coupled to GS/GP the AP will level off wherever you are if you press ALT thus making bugging MDA unnecessary except as a visual reference.

Exactly.

 

[Dixiebluesky]

There is no real right or wrong way with some of this stuff although most people will think their way is the best. Once you get a good grasp on the procedures you will come up with a way that works for you personally in that plane with that equipment. A way of setting things up that you find easily repeatable and allows you to stay within the parameters of the procedure.

It is like how the book says "in a configuration to land" by the FAF or something like that for the checkride. I see a lot of instructors teach to have everything set up like you would land in the next 50 ft while still 5 miles out. Unless your POH specifically says you need full flaps to land why would you do that? Simply having the gear dropped and 10 deg of flaps with a little more speed is much more reasonable. If you break out simply adjust power and add flaps to preferred speeds. If you have to go missed the airplane is configured in a way that requires the least amount of changes while maintaining the best handling for the missed procedure.

 

[MauleSkinner]

If I’m not mistaken, if you are coupled to GS/GP the AP will level off wherever you are if you press ALT thus making bugging MDA unnecessary except as a visual reference.

I know there black and white instances, but there are some grey areas that seem to be dealer’s choice.

I know that's been a recommendation forever but I never saw a good reason (let alone a "necessity") for it in any system where you set an target altitude. If I break out I'm going to land so I don't care. If I go missed I'm going to climb so I want my target altitude ready to go. If for some reason it's the <1% of the time I need to level off at the altitude I've been vocally counting down to for the last 5 minutes or so, that's one button.
@MauleSkinner?

Like I said, depends on the level of automation you want to be comfortable with. Overall, I agree with @RussR. Set up the automation to do what it’s designed to do.

Also, I assume the ALT button works the same across most platforms too in that it captures the altitude you’re at when you select it. If you’ve got a descent rate going, it’s going to go through that altitude and recover, and so you’ll either need to press it early and then manipulate the automation to get to MDA, or manipulate the automation to level off before you press ALT. Either way, more work in my mind.

 

[dmspilot]

My carrier sets missed approach altitude for all approaches, including nonprecision.

 

[midlifeflyer]

Also, I assume the ALT button works the same across most platforms too in that it captures the altitude you’re at when you select it. If you’ve got a descent rate going, it’s going to go through that altitude and recover, and so you’ll either need to press it early and then manipulate the automation to get to MDA, or manipulate the automation to level off before you press ALT. Either way, more work in my mind.

One of the exceptions @RussR mentioned was treating an MDA as a DA, which also involves adding a buffer to the MDA.

Not to mention that this is what you do with an AP that doesn’t have preselected altitude capability.

 

[Clip4]

Final missed approach climb altitude.

That’s SOP on approaches with vertical guidance. You might even see it as the recommended procedure in your AFMS. On approaches without vertical guidance, there have been recommendations to enter the MDA, but I personally never saw why.

I don’t see a reason for using the initial missed altitude or any climb altitude you are not going to level off for.

I am always reluctant to make always type statements. We never see a reason until presented with a situation where there is a reason, but I have never experienced a situation where I would want the initial altitude set yet.

 

[MauleSkinner]

One of the exceptions @RussR mentioned was treating an MDA as a DA,

True, and the automation would be used appropriate to a DA.

which also involves adding a buffer to the MDA.

I think adding a buffer is a DDA. The MDA as a DA operators that I see don’t add a buffer.

Not to mention that this is what you do with an AP that doesn’t have preselected altitude capability.

If you’re going to default to the lowest level of automation you may see, that would be “none.”

Generally speaking, I prefer to fly the airplane I’m in.

 

[RussR]

One of the exceptions @RussR mentioned was treating an MDA as a DA, which also involves adding a buffer to the MDA.

Not quite. Opspec C073 (I think) authorizes an MDA to be treated as a DA, without additives, if certain conditions are met. Of course, you have to be authorized to use that Opspec in the first place.

 

[RussR]

I know that's been a recommendation forever but I never saw a good reason (let alone a "necessity") for it in any system where you set an target altitude. If I break out I'm going to land so I don't care. If I go missed I'm going to climb so I want my target altitude ready to go. If for some reason it's the <1% of the time I need to level off at the altitude I've been vocally counting down to for the last 5 minutes or so, that's one button.

To be fair, I did say "where you plan to level off". If you plan to use the autopilot to level off (at any altitude), the altitude bug needs to be set for that altitude.

In my experience, just tapping ALT causes the problems discussed by @MauleSkinner .

 

[MauleSkinner]

To be fair, I did say "where you plan to level off". If you plan to use the autopilot to level off (at any altitude), the altitude bug needs to be set for that altitude.

That’s a good way of putting it. This really is a confusing issue for a lot of people, and you can explain it until you’re blue in the face and some people won’t get it. But starting off with, “what do you do when you get to MDA that’s different from what you do when you get to a DA?” and “how do you tell the automation to level you off at a desired altitude?” might be a way to get through.

 

[4RNB]

Had a lot of great responses on my last post. Here’s another for the crowd….

How’s everyone managing altitude bug on coupled precision and non-precision approaches? It’s my understanding and (limited) experience that once GS/GP is captured, AP will prioritize that over selected altitude. So what are your preferences with the alt bug at this point?

Bugging DA/MDA as a reference? Bugging initial straight ahead climb-out alt for missed? Full missed procedure altitude (assuming a climbing turn after initial climb out)?

It depends.

 

[midlifeflyer]

True, and the automation would be used appropriate to a DA.

I think adding a buffer is a DDA. The MDA as a DA operators that I see don’t add a buffer.

If you’re going to default to the lowest level of automation you may see, that would be “none.”

Generally speaking, I prefer to fly the airplane I’m in.

I see it as a difference in technique, nothing more. I just don’t see a good reason for placing the missed hold altitude in the box for an approach with a DA and the MDA in the box when it’s not. That’s literally all I said, I still don’t. I like consistency in operation unless I see a good reason to do it another way.

Horrors, I still don’t use VTF, even if I’m using a GTN. And, yes, I still sometimes get someone saying that’s not “appropriate” use of a GTN since it retains fixes along the extended FAC. I still “default to the lowest level of automation” for that too.

If you prefer to do it differently for whatever rationale, that’s ok with me. Just don’t treat your technique as some sort of gospel of the advanced or an assumption that I dint know the difference between a DA and an MDA.

 

[Tarheelpilot]

Didn’t know we could discuss politics on this board.

I generally followed the basic principle of put my next level altitude in the box.

 

[MauleSkinner]

Just don’t treat your technique as some sort of gospel of the advanced or an assumption that I dint know the difference between a DA and an MDA.

I have no plans to do so.

 

[John Collins]

I set MDA+50 into the altitude pre-select when I plan to circle because I use it during the circle. I set the MDA into the G500TXi minimums.

 

[flyingcheesehead]

How’s everyone managing altitude bug on coupled precision and non-precision approaches? It’s my understanding and (limited) experience that once GS/GP is captured, AP will prioritize that over selected altitude. So what are your preferences with the alt bug at this point?

Bugging DA/MDA as a reference? Bugging initial straight ahead climb-out alt for missed? Full missed procedure altitude (assuming a climbing turn after initial climb out)?

Depends on what equipment I'm flying and whether or not someone else gets to tell me what to do (135).

If it's just me, in a plane with a separate Minimums bug, I'll set the altitude bug to the missed approach altitude after reaching *and capturing* my last level altitude on the approach. Normally this is either where I'm vectored onto the approach or the intermediate segment altitude for ILS/RNAV, or the lowest level-off for non-precision approaches.

If I don't have a separate Minimums bug (G5, for example) I'll put the altitude bug at minimums as a reminder.

At work, we can set Baro mins but that doesn't come with its own bug, so you still use the regular bug, but it gives the regular altitude bug a new "step" between 1000s of feet.

I like what @MauleSkinner said: Fly the plane you're in.

 

[Martin Pauly]

GFC 500 AFMS says to set missed approach altitude for ILS. For LPV it’s not super clear.

What is different when you fly an LPV? After GS (ILS) or GP (LPV) intercept, I set my altitude bug to the missed approach altitude. Is there a potential trap with an LPV that I am not aware of?
My equipment is Garmin GTN and GFC, and Aspen PFD.

Thanks,
Martin

 

[MauleSkinner]

What is different when you fly an LPV? After GS (ILS) or GP (LPV) intercept, I set my altitude bug to the missed approach altitude. Is there a potential trap with an LPV that I am not aware of?
My equipment is Garmin GTN and GFC, and Aspen PFD.

Thanks,
Martin

I would use that setup for anything with a DA…an ILS or an RNAV approach to either LPV or LNAV/VNAV minimums.

 

[flyingcheesehead]

Not necessarily true in all cases. GFC 500 AFMS says to set missed approach altitude for ILS. For LPV it’s not super clear.

Huh? I'm looking at the one for the M20R, and for a vertically guided GPS approach it says to set missed approach altitude after GP capture, similar to ILS.

Likewise, for all non-precision approaches (LOC, LOC BC, VOR, GPS LP/LNAV) it says to set the missed approach altitude "when in ALT mode at the MDA."

In reality, I don't fly approaches that aren't vertically guided any more, so I set the missed altitude prior to the FAF and set my Minimums bug as a reminder for where those are.