LPV - LNAV/VNAV - LNAV MDA

[ChristianGodin]

A few questions for the pros.

I am kind of mixt up with LNAV LNAV/VNAV and LPV

1) How can I see directly on my 430 if it is WAAS?

2) if my 430 is WASS, am I allowed to do a LPV?

3) LNAV VS LNAV/VNAV: How do I see the difference on my 430. For both approch I get a glide slop on the 430?

Thank You

[danb35]

1. When your 430 powers up, it should indicate on the startup screen whether it is a 430 or a 430W. The latter is WAAS; the former isn't. If you're getting glide path indication on any GPS approaches, it's a 430W; the 430 (the non-WAAS model) doesn't give glide path indications on GPS approaches.

2. If your 430 is WAAS, the approach you're shooting has published LPV minima, and the signal integrity is good enough (the latter two of which will be indicated by your 430W annunciating "LPV" in the lower-left corner of the screen as you pass the FAF), you can shoot an approach to LPV minima.

3. As with the last question, the minima you can use are indicated on the 430's screen in the lower-left corner once you pass the FAF. Under no circumstances may you descend below the MDA until you have the runway environment in sight, no matter what the glideslope needle tells you.

[Cruiser]

1. What Dan said.

2. Yes, Localizer Performance with Vertical guidance (LPV) approach. Fly to LPV minimums. Normally the display in the lower left corner of the screen will have a green colored background and indicate the LPV approach being flown. A yellow background indicates that the approach is safe to continue but a downgrade to LNAV may occur.

Sixty seconds prior to reaching the FAF, the unit will check the required Horizontal Alarm Limit (HAL) and Vertical Alarm Limit (VAL) to ensure the GPS position integrity is within limits to complete the LPV precision approach. In the event the HAL or VAL limits are exceeded, the approach will be downgraded to a non-precision approach indicated by “LNAV ” on the moving map, a message that the approach is downgraded (“Approach downgraded - Use LNAV minima”), and the glideslope indicator will be flagged. You may continue the approach using LNAV non-precision minimums if there are LNAV minimums for this approach. In the rare event the GPS integrity cannot meet the non-precision HAL limits, the unit will send a message to the pilot to abort the approach (“Abort Approach - Loss of Navigation”). The unit will revert to terminal limits to support navigation to the missed approach when the message is acknowledged.

3. Flight mode annunciations are provided in the lower left corner of the display indicating the current mode of flight.

When within 45° of the final approach course and the FAF is the TO waypoint, the 400W-series unit switches from terminal mode to “approach” mode. CDI scaling is tightened from 1.0 NM full scale deflection to either 0.3 NM or 2° full scale deflection whichever is less at the FAF. The change occurs over 2 NM and is completed by the FAF. The Flight mode annunciation changes from TERM to the type of approach being flown i.e. LPV, etc.

LNAV approach does not provide verical guidance . LNAV+V does include ADVISORY vertical guidance but the GS does not include step down minimums.

[ChristianGodin]

Thank You

Is a LNAV/VNAV a precision or a non precision approch?

[danb35]

Only an LPV can be a precision approach (and not even all of them are).

[Jeff_S]

I believe even LPV is not considered an "official" precision approach, unless those rules have changed from what I learned during my IFR training.

[M20F]

I believe even LPV is not considered an "official" precision approach, unless those rules have changed from what I learned during my IFR training.

There were only ever 2 reasons where precision versus non-precision mattered. The first was the instrument PTS which has since been amended to allow LPV to be used as a precision approach for the practical. The second is for alternate purposes (600-2 versus 800-2) and for that purpose only ILS/PAR are considered precision.

So in effect other then requirements for alternate there is no difference betweeen precision/non-precision.

Keep in mind that an ILS has very specific requirements (lights, runway markings, etc.) that do not have to exist for an LPV. In order for a LPV to get to 200-1 it needs to have those things but 300-2 LPV approach for example might have no markings or poor lighting. Ensure you review each specific LPV to know exactly what your getting because it isn't uniform like an ILS is.