LNAV/VNAV minimums setting

[ableone]

The ATA POI is not the only one and he is not necessarily incorrect.

If you are flying an RNAV approach you may have an MDA or a DA. If you have Baro V-nav capability (LNAV/VNAV on the plate) you may have a DH. If so you can descend below DH on the missed. If, however, you are using just LNAV minimums or the LNAV/VNAV has an MDA you can not descend below MDA.

(If an airline ever installs WAAS then they will be able to use LNAV/VNAV minimums without the temp and baro restrictions and will also be able to use the LPV minimums.)

At USAirways if you are flying an RNAV approach with an MDA something called a DDA or Derived Decision Altitude is used. This is MDA+50ft. This ensures that the aircraft does not descend below MDA on the missed.

On the bus the MA altitude is selected and the autopilot will indeed disconnect at whatever altitude is inputed into the DH prompt.

(The plates airlines use may depict DH for LNAV/VNAV minimums but you may have to treat it as an MDA depending upon your ops specs. The LNAV/VNAV DH was designed for WAAS GPS equipped aircraft but most airlines meet the LNAV/VNAV equipment requirements through their FMS systems [Baro V Nav] and are not necessarily legal for the DH)

 

[wahoo250]

Unfortunately our ops specs dont have a defined procedure, but the QRH does and its TDZE. Had to dig for it but its there. Ive flown at a few different companies 91 and one 121 company and everyone does it differently. i dont really see a difference between airport elevation and 0000. Either way if you dont touch anything your flying into the ground. The only benefit to TDZE I see is on a missed in say Denver you dont have to twist your wrist as much dialing in a missed approach altitude when executing a missed approach...

 

[Dogwood]

If you set missed aproach altitude and arm vnav, you will never get the airplane to decend to the DH...at least in the GV. I think you guys have the updated software that allows you to set a dh and still set a missed approach altitude...like an ILS. I was told it was an FAR to set DH. I didnt think it was and have been trying to find it... Im guessing the parameters that you are speaking of are the FMS going to aproach mode once near the FAF...thanks for the replies

This question will vary by aircraft and airline. We refer to the VNAV approaches as RNAVs, and we fly them just like an ILS. Load it in the box, clean it up, get vectors, and push the APP button when cleared. When it indicates FINAL APP, meaning it's ready to capture the database driven glidepath, we then set the Missed App Altitude.

 

[Pilot Knob]

Nav and Prof to the LNAV or LNAV/VNAV minimums, whichever is lower. They are set in BARO rounded up to the nearest 10 feet(1895=1900, FMS precludes anything other than 10's) Runway in sight,disconnect autopilot and set vert speed to 800 ft./min. descent and preset M.A. altitude. Missed is made as soon as "Hold" is shown in the FMA and runway is not in sight. LPV's are not authorized. All of this assumes the approach is in the database. No building your own using the fixes and altitudes.

 

[mach none]

My God!! Even w/ a fresh cup of coffee that gave me a head ache. I feel for all of you ATA guys. That POI should be shot.

At Alaska: On a published part of the appch, at or past IAF, LNAV/VNAV Path, Dial the dirt and watch the magic.

That Easy - Even a Cave Man Could Do It!!!

Baja.

A cave man or someone from the -200 in ANC.