G1000 and holds

[olasek]

The arrow-like symbol in the profile view with 3.00 degrees and the TCH.

yeah, returning to my previous question what's the exact definition of VDA?

 

[Alexb2000]

http://aeronav.faa.gov/d-tpp/1501/09852r18.pdf

The arrow-like symbol in the profile view with 3.00 degrees and the TCH. It that is not there you will have LP, not LP+V.

Obviously, an LP approach already has obstacle penetrations in the visual segment and glide-slope qualification area (or an inadequate survey). If it didn't it would be an LPV approach. Flight inspections makes the call on whether an LP or LNAV IAP will have a VDA. They assess the extent of the close-in obstacles. If they decide that trees, etc, close in are of sufficient hazard they nix the VDA so the pilot can fly into the trees without federal help.

It seems that the LP approaches don't offer that much more, maybe 20'. Is the only real advantage that they can be put in places where there are more obstacles because the protected area is angular?

 

[aterpster]

yeah, returning to my previous question what's the exact definition of VDA?

Well, yeah, it means Vertical Descent Angle.

From the AIM: (helping you since you apparently don't read this stuff)

(c)​

Nonprecision Approach (NPA). An instrument​

approach based on a navigation system​

which provides course deviation information, but no​

glidepath deviation information. For example, VOR,​

NDB and LNAV. As noted in subparagraph i, Vertical​

Descent Angle (VDA) on Nonprecision Approaches,​

some approach procedures may provide a Vertical​

Descent Angle as an aid in flying a stabilized​

approach, without requiring its use in order to fly the​

procedure. This does not make the approach an APV​

procedure, since it must still be flown to an MDA and​

has not been evaluated with a glidepath.

 

[aterpster]

It seems that the LP approaches don't offer that much more, maybe 20'. Is the only real advantage that they can be put in places where there are more obstacles because the protected area is angular?

It's an FAA WAAS program thing.

 

[TangoWhiskey]

If they decide that trees, etc, close in are of sufficient hazard they nix the VDA so the pilot can fly into the trees without federal help.

Funniest true post this year! Bravo!

 

[olasek]

some approach procedures may provide a Vertical
Descent Angle as an aid in flying a stabilized approach

So I reckon this is the same exact angle that is used by G1000 (or equivalent box) to enable +V when it shows during a nonprecision approaches.

 

[aterpster]

So I reckon this is the same exact angle that is used by G1000 (or equivalent box) to enable +V when it shows during a nonprecision approaches.

Yes, the VDA is on the FAA source document and is what Jeppesen and Garmin use for the final approach segment advisory vertical path (+V in Garmin-speak).

Using Eureka, Nevada as an example, on the right side of the source form under Additional Flight Data the VDA is stated as:

"SAYOT to RW 18: 3.00/45"

This source document can be seen at:

http://aeronav.faa.gov/acifp/ndbr/2010121525548901001-05U-NDBR/02A_NV_EUREKA_RG18_05U.pdf

 

[olasek]

I complement you for being able to dig out all this 'behind the scenes' FAA tech stuff.

 

[aterpster]

I complement you for being able to dig out all this 'behind the scenes' FAA tech stuff.

I work with it all the time.

 

[Dr. O]

"the OBS mode, it's still a lot of constant knob twisting, setting the clock or watching DME, etc. Boring busy work"

uuuuh yeah. It's called instrument flight, not sipping cappuccino flight.
I strongly suspect that some folks today do not have the basic skills to navigate in IMC with a DG and AH, a clock, and a chart/plate.
I like my moving map color GPS. But I do not bet my life on it without having an exit strategy based on some form of steam gauges - and using them once in a while.

 

[Alexb2000]

"the OBS mode, it's still a lot of constant knob twisting, setting the clock or watching DME, etc. Boring busy work"

uuuuh yeah. It's called instrument flight, not sipping cappuccino flight.
I strongly suspect that some folks today do not have the basic skills to navigate in IMC with a DG and AH, a clock, and a chart/plate.
I like my moving map color GPS. But I do not bet my life on it without having an exit strategy based on some form of steam gauges - and using them once in a while.

So is your contention that, I should be excited to fly a hold, or that I'm incompetent or is it both?

Pilots should be able to use the instrumentation in their aircraft to fly any instrument procedure out there with confidence.

 

[pfking]

yeah, returning to my previous question what's the exact definition of VDA?

There's more in AIM 5-4-5k:

k. Vertical Descent Angle (VDA) on Nonprecision Approaches. FAA policy is to publish VDAs on all nonprecision approaches. Published along with VDA is the threshold crossing height (TCH) that was used to compute the angle. The descent angle may be computed from either the final approach fix (FAF), or a stepdown fix, to the runway threshold at the published TCH. A stepdown fix is only used as the start point when an angle computed from the FAF would place the aircraft below the stepdown fix altitude. The descent angle and TCH information are charted on the profile view of the instrument approach chart following the fix the angle was based on. The optimum descent angle is 3.00 degrees; and whenever possible the approach will be designed using this angle.

1. The VDA provides the pilot with information not previously available on nonprecision approaches. It provides a means for the pilot to establish a stabilized descent from the FAF or stepdown fix to the MDA. Stabilized descent is a key factor in the reduction of controlled flight into terrain (CFIT) incidents. However, pilots should be aware that the published angle is for information only - it is strictly advisory in nature. There is no implicit additional obstacle protection below the MDA. Pilots must still respect the published minimum descent altitude (MDA) unless the visual cues stated 14 CFR Section 91.175 are present and they can visually acquire and avoid obstacles once below the MDA. The presence of a VDA does not guarantee obstacle protection in the visual segment and does not change any of the requirements for flying a nonprecision approach.

2. Additional protection for the visual segment below the MDA is provided if a VDP is published and descent below the MDA is started at or after the VDP. Protection is also provided if a Visual Glide Slope Indicator (VGSI); e.g., VASI or PAPI, is installed and the aircraft remains on the VGSI glide path angle from the MDA. In either case, a chart note will indicate if the VDP or VGSI are not coincident with the VDA. On RNAV approach charts, a small shaded arrowhead shaped symbol (see the legend of the U.S. Terminal Procedures books, page H1) from the end of the VDA to the runway indicates that the 34:1 visual surface is clear.

3. Pilots may use the published angle and estimated/actual groundspeed to find a target rate of descent from the rate of descent table published in the back of the U.S. Terminal Procedures Publication. This rate of descent can be flown with the Vertical Velocity Indicator (VVI) in order to use the VDA as an aid to flying a stabilized descent. No special equipment is required.

4. Since one of the reasons for publishing a circling only instrument landing procedure is that the descent rate required exceeds the maximum allowed for a straight in approach, circling only procedures may have VDAs which are considerably steeper than the standard 3 degree angle on final. In this case, the VDA provides the crew with information about the descent rate required to land straight in from the FAF or step down fix to the threshold. This is not intended to imply that landing straight ahead is recommended, or even possible, since the descent rate may exceed the capabilities of many aircraft. The pilot must determine how to best maneuver the aircraft within the circling obstacle clearance area in order to land.

5. In rare cases the LNAV minima may have a lower HAT than minima with a glide path due to the location of the obstacles. This should be a clear indication to the pilot that obstacles exist below the MDA which the pilot must see in order to ensure adequate clearance. In those cases, the glide path may be treated as a VDA and used to descend to the LNAV MDA as long as all the rules for a nonprecision approach are applied at the MDA. However, the pilot must keep in mind the information in this paragraph and in paragraph 5-4-5l.​

 

[olasek]

Good stuff, and what exactly is the meaning of say 'TCH 45' right below the VDA angle??


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[pfking]

Good stuff, and what exactly is the meaning of say 'TCH 45' right below the VDA angle??

It was actually defined in the second sentence of AIM 5-4-5k quoted above.

Here's a picture if that will help.

 

[aterpster]

Good stuff, and what exactly is the meaning of say 'TCH 45' right below the VDA angle??


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Using the Eureka, NV LP Rwy 18 again as an example, the FAA and Jeppesen have a different charting method for the VDA:

 

[olasek]

Thanks a lot.


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