Can VNAV land you properly ?

[JSACKS 0]

Just want to thank folks for jumping in here with notes and advice. This is a lively thread and I am learning all the time.Jonathan

[Guest Moviedirector20]

Theoretically you dont need the FMC for an autoland. Just intercept the Loc, put in app mode. Engage the secend AP (CMD B, however you need to have the ILS freq in both navs!!) and flare should appear. At 50 RA it will flare and put in reverse thrust, brakes, and speed brake.

[jon b 2,047]

I can`t speak for the 737NG,but on the 744 you`ll only get the flare mode to arm from Approach mode ie LOC green Glideslope green.Vnav normally has altitude coding down to 50ft above threshold height so leaving the AP in and flying a VNAV profile the aircraft won`t land,but level off above the runway.As someone mention LNAV/VNAV approaches are the way of the future,they will allow precision approaches in bad weather to places that at the moment only have NDB or VOR appraches,like in the carribeanAt virgin the training dept are engaged in the trial of these sorts of approaches at the moment,their implimentation is still some way off thoughregardsJon

[JSACKS 0]

I just landed again at KSFO after reprogramming the descent in the NG -800 from a flight from KSEA and I was approached in LNAV+VNAV pretty close to perfectly from the last waypoint at 1700 AGL. The only thing was that the speed did not reduce from my programmed IAS 155 in the FMC at that point down to the FMC indicated approach Vref+margin speed of 139. But all else worked perfectly and the VNAV tracking matched the glideslope almost perfectly. Watching the vertical descent indicator and checking with the FMC, I was off by 50 to 90 vertical feet (probably due to my own slightly inaccurate programming of the final waypoint at FF28L) but the gap decreased as I got closer to the ground. The PFD indicated very close to GS and LOC while the KSFO VASI of 28L indicated 1 white and 3 red from 500 AGL down. My speed over the fence was IAS 153 with flaps 25. In classic FS fashion, Ultimate Traffic generated a departing aircraft on 28L at the same moment as my approach and I took manual control to leapfrog over a UAL Airbus and land illegally and dangerously 6000 feet farther down the runway; but it was a great landing and I had enough room to brake to taxi speed safely by the end of the runway.This satisfies my amateur FS brain totally. It's all I really wanted to know: can VNAV in essence fly me all the way down to the destination runway? Answer: pretty much yes, but as various folks here have advised, I need to take control at a reasonable altitude (like DH at the latest) because there is no actual autoland in this mode. It's good to know that this is a workable alternative to an ILS approach.Well, I can call it a day on this issue now. Thanks again to everybody for posting and providing information, views, and advice.Jonathan

[Guest tmetzinger]

>Tim,>>The other day I took the PMDG 737NG - 600 into Belfast UK Int>A/port and did a full Cat III autoland all the way down to the>runway in App mode with Vnav and Lnav engaged all the way.>From what you say in your last sentence this is not realistic>- or did I misundestand? Are you saying that while the a/craft>can do it, procedurally it is wrong?>>Regards>>IainWhile the sim can perform an autoland (tracking an ILS in dual-channel) is possible with any ILS, in real life, there are a limited number of runways where this is possible.All sorts of things are required to get an airport certified for CAT II and III operations, and one of the chief requirements is having enough flat space around the airplane so that the radar altimeter (which is what triggers the flare) isn't confused by changing terrain. So, unless the approach you are flying has CAT III on the chart, then technically you aren't authorized to autoland on it.

[Guest glenb]

Jonathan,Good to hear it worked for you at KSFO 28L. UT :-) I have had the same thing so many times that if I use Ultimate Traffic I will set the traffic in fs9 to zero somewhere on the approach to avoid that problem.If you are up to it try KLAS RNAV (GPS) RWY 25R. I have tried that one so many times with no success. At FEXEN the FAF it will not descend (or descend very slow) to where I take over and use V/S or some other means of controlling the descent. Like I said it works at KPHX but not KLAS and I can find no reason in the SIDSTAR files to explain that.RNAV is the future but I wonder how hard it will be to get the experienced (older) pilots to use it instead of ILS?We are having fun now!

[kmanning 12]

While the sim can perform an autoland (tracking an ILS in dual-channel) is possible with any ILS, in real life, there are a limited number of runways where this is possible.All sorts of things are required to get an airport certified for CAT II and III operations, and one of the chief requirements is having enough flat space around the airplane so that the radar altimeter (which is what triggers the flare) isn't confused by changing terrain. So, unless the approach you are flying has CAT III on the chart, then technically you aren't authorized to autoland on it.Tim,You're absolutely correct on the Catagory III system. Ken.

[teropa 4]

Not entirely true. Autolands are allowed on CAT II and CAT III runways. For example Finnair policy is to fly a CATII approach to 50ft RA and then either make an autoland or disconnect and fly the landing manually.Under normal circumstances, you can make a perfectly good autoland on even CATI ILSes, but that is not allowed because the signal quality cannot be ensured on CATI facilities (no separate holding points safely away from the beam etc. etc.).Tero

[Guest tmetzinger]

>Not entirely true. Autolands are allowed on CAT II and CAT>III runways. For example Finnair policy is to fly a CATII>approach to 50ft RA and then either make an autoland or>disconnect and fly the landing manually.>>Under normal circumstances, you can make a perfectly good>autoland on even CATI ILSes, but that is not allowed because>the signal quality cannot be ensured on CATI facilities (no>separate holding points safely away from the beam etc. etc.).>>TeroThanks for the correction! Procedures obviously vary amongst operators and nations.For those of you who always land by hand, remember that the CREW is also certified for CAT II and III operations, and have to log a certain number of autolandings to maintain that certification. So let the airplane do the work now and then.