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Guest wtsapchy

VOR Approach

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Guest wtsapchy

Hi all,I would like to know how real 747 pilots fly their VOR approach down to touchdown. What autopilot mode do they use ? Do they program all the waypoints and the altitude restriction in FMC and use autopilot LNAV and VNAV, or VS mode ? If so, what altitude is set in alt window ? Is there any tutorial on how real 747 pilots fly VOR approach ?Hope someone can help !!!DanielVHHH

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Guest tmetzinger

It will vary depending on the airline, but in general, all non-precision approaches except localizers are flown in LNAV, and the pilot is responsible for monitoring the raw data for any discrepancies. Vertical path could be flown in VNAV or VS.Best Wishes,

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Approaches are now considered to be either ILS or non ILS. VOR, NDB, RNAV and GPS approaches fall into the later category and are all flown using the same basic procedure. In our airline we can use either LNAV or HDG SEL and V/S or VNAV.If the later is used then the waypoints associated with the approach cannot be modified (except for speed) and extra points cannot be added. This is so the 'on approach mode' VNAV submode (not annunciated anywhere) functions correctly. Essentially this allows the MCP speed window to be opened and the aircraft speed controlled directly, via the speed window on the MCP, with VNAV PTH still showing and following the APP VNAV profile. Normally (prior to approach) if you are descending in VNAV PTH and open the speed window on the MCP panel then the pitch mode will revert to VNAV SPD and the FMC calculated path no longer flown. This aspect is not modelled correctly in the PMDG sim as it stays in VNAV PTH regardless.Anyway back to the approach.Get yourself established on the inbd app course and select LNAV. You should be at or near procedure commencement altitude prior to the approach descent point (IAF). When either VNAV ALT or VNAV PTH is annunciated wind down the MCP alt to DA (add 50 ft to MDA) or the mearest 100 ft below. Normally we would have the monitoring pilot select the VOR raw data on his ND and also select it on the secondary EICAS screen for the PF to look at as well as any other supp pilots (use the switch in front of the captain that says INBD CRT to lower EICAS (or something like it). Watch the VNAV slope indicator on your ND and ensure the aircraft descends on the path at the right point. If in VNAV ALT you will need to press VNAV again at the descent point. Ensure it changes to VNAV PTH. When you are more than 300 ft below Missed App alt then reset the MCP alt to the MAP alt. This prevents a possible premature alt capture if you were to reset it too early. The setting of the Decision Altitude instead of an Minimum Descent Altitude (by adding 50 ft to it) allows you to treat minmas as you would for an ILS. The 50 ft buffer allows for the sink when you go around at DA. At DA disconnect the AP and ensure that the AT's are disengaged prior to touch down.The aircraft flys VNAV approaches well. Keep it simple by flying full drag approaches or at least keeping it dirty as it will help the AP maintain speed on the approach.If you are flying in V/S then prior to descent select V/S zero. Wind down the MCP alt to either the next limiting altitude (if any) or down the DA (MDA plus 50 ft) or the nearest 100 ft below. If setting an intermediate alt reset it before it captures the altiude (Use the green arc to assist with descent monitoring).If at any time LNAV does not look to be tracking correctly then be prepared to overide using HDG SEL. Just a note of caution. Make sure all the waypoints cycle correctly. It is possible (say thru radar vectoring and using HDG SEL) that a waypoint may not have sequenced correctly and may subsequently be behind the aircraft. When you select LNAV you will wonder why the A/C is doing a split arse turn back from where you came! Always make sure the active waypoint is in front.Each airline will have it's own variations as to how to fly non precison approaches, this is just our way.Hope this helps.CheersSteve


Cheers

Steve Hall

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My two cents, although I'm not 747 rated, I doubt seriously that VOR approaches are flown with VNAV guidance. The only approaches that are designated by the FAA for VNAV are precision approaches (ILS) and some (but not all) RNAV (GPS) or (RNV) approaches. Take a look at the bottom of the chart where the minima are published. If the approach is approved for VNAV it will provide minimum for it. For example, RNAV (GPS) Y approaches only provide minima for LPV, but RNAV (GPS) Z approaches provide minima for both. VOR approaches are flow with reference only to the VOR unless it is an overlay approach in which case it will be designated VOR GPS. There's a difference between what you can do and what is intended by the folks who design the approaches, and only sticking to the intent are you assured adequate terrain and obstruction clearance.


Dan Downs KCRP

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Guest tmetzinger

>My two cents, although I'm not 747 rated, I doubt seriously>that VOR approaches are flown with VNAV guidance. The only>approaches that are designated by the FAA for VNAV are>precision approaches (ILS) and some (but not all) RNAV (GPS)>or (RNV) approaches. Take a look at the bottom of the chart>where the minima are published. If the approach is approved>for VNAV it will provide minimum for it. For example, RNAV>(GPS) Y approaches only provide minima for LPV, but RNAV (GPS)>Z approaches provide minima for both. VOR approaches are flow>with reference only to the VOR unless it is an overlay>approach in which case it will be designated VOR GPS. There's>a difference between what you can do and what is intended by>the folks who design the approaches, and only sticking to the>intent are you assured adequate terrain and obstruction>clearance.>>Sorry, Dan, you're wrong on this. While the non-precision approaches like VOR/NDB/LOC/BC don't provide any continuous glide path, it's quite simple to program the stepdown altitudes and MDA into the procedure, and many operators do indeed fly them in LNAV/VNAV. They are required to monitor the raw data, however.

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Thanks, Tim, I've learned something. However, my comments on minima are still true, but the surprise is that real world FMC navigation for VOR (for example) approaches actually includes the vertical profile that the pilot is able to use. I assumed incorrectly that these would only be available for overlay approaches. Do the real world vertical profiles stop descent at minima, and the pilot then completes the approach visually? I really would be surprised if vertical guidance was provided down to the runway.


Dan Downs KCRP

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Guest ColdBear

Dan,With all respect....are you, of any kind, involved with professional aviation?(I am useing Jeppesen IFR terminal charts)On the approach charts the respective minimums are shown. like for a CAT I ILS the DH(Hight)is 200feet. for a VOR/DME approach the MDA(H) is shown as fx 390(384) as shown here on the chart for ROST, NORWAY(ENRS).If no visual contact is made on a non-precision approach a go-around must be made. however the FMS doesn't know about DA/MDA so it's profile will end at the runway, it's up to the pilots to look out at or before DA/MDA.Doing a non-precision approach the decision point can either be a DME distance or a timed fix. this will also be shown on the bottum of the chart.RVR and met vis will also be shown just below the vertical profile, along with the respective minima's, if CL, ALS or TDZ is U/S higher minima's will also be shown.hope this help a little.Martin

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Guest tmetzinger

>Thanks, Tim, I've learned something. However, my comments on>minima are still true, but the surprise is that real world FMC>navigation for VOR (for example) approaches actually includes>the vertical profile that the pilot is able to use. I assumed>incorrectly that these would only be available for overlay>approaches. Do the real world vertical profiles stop descent>at minima, and the pilot then completes the approach visually?>I really would be surprised if vertical guidance was provided>down to the runway.Vertical guidance is provided down to the runway, and if the pilot has the appropriate visual references and the Ops spec allow it one can leave the autopilot engaged until the minimum operating altitude. One can leave the flight director engaged all the way down.This is BARO VNAV, not WAAS-enabled guidance, so there are limits depending on the equipment on it's use.

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