It’s not necessary to arm VOR/LOC before arming APP. It’s just that sometimes we do meet the criteria for VOR/LOC arming but not yet for APP arming. This is about how off you are from the glideslope and how far you are from the airfield. If you meet the criteria for APP you can arm it without arming VOR/LOC first.
Of course part of the criteria is having a positive indication of that glideslope signal and that it’s not a false one (especially when capturing it from above) and an identified localizer. I’d say with good descent planning I go straight to APP on 80% of the cases. Only when we’re cleared for the approach very far from the airfield or when capturing the glideslope from above I’d use VOR/LOC for a bit longer before arming APP.
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Agreed for the most part, except I probably wouldn’t even bother with vor/loc, I’d just join in LNAV and maybe VNAV if I was far enough out to worry about having a steady signal. Lateral track will be a lot steadier in LNAV anyway; as long as in Approach by the FAF, all good.
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I have another question, kinda regarding the app mode.
I was inbound full VNAV&LNAV mode towards Kelowna (awesome approach btw) got a stable glidepath using vnav and app, at what point should you take over and hand fly it? Is there a certain point or just whenever you feel comfortable? Autoland isn’t possible without ILS right?
Thank you
-Bram
As I understand, for rnav approaches you cannot do autoland. But you can keep the AP on till you reach approach minima (which is usually a barometric altitude) which can be determined from the approach plate. If the visibility is good, you can take it out of AP whenever you prefer.
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Thank you for the detailed reply!
Now I can again improve more towards professional / realistic flying the 737.
-Bram
I usually turn off AP and AT 1000ft above ground when visibility is good.
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Nope, no autoland off an RNAV approach, but autoland is hardly ever used from an ILS either, not unless visibility is so low that it’s required.
In reality, the lowest you can have the autopilot engaged on an RNAV approach is minimums. But there’s no reason to wait until then to disengage it either. There seems to be a feeling in the sim world that airliners are not hand flown, and this is simply not true. The automation is a great workload management tool, but you can handfly an entire approach unless there’s a workload based reason not to, no matter the weather conditions. Handflying is encouraged in the industry these days; after too many years of over-reliance on automation, pilots were getting rusty at basic aircraft handling.
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People should watch these guys. They do most of their landings in A319 and A320 manually.
Approach and Departure Videos - YouTube
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Thanks for al the info! Appreciate it, I want to get as close to reality as possible flying the PMDG.
-Bram
P.s.
just did my first full LNAV&VNAV flight towards Kelowna, really nice approach!
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Yep, this CYLW 34 approach is absolutely stunning.
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I’ve tried to hand fly a full approach, find that from a single (sim) pilot standpoint the workload is just too high and I quickly get behind the aircraft. Still working on it though…
Nicely presented videos, like the multiple windows open so you have much better awareness of what’s happening in the cockpit. Just wish someone did something similar for the 737!
I have to beg to differ.
PMDG simulate the aircraft, and IAN is part of that aircraft so it should absolutely be part of the simulation.
In the real world on the 787 if I have to fly an RNAV approach that meets the criteria for an IAN I would always use it. In fact it’s SOP to use it. It’s much simpler, keeps things more standard (which after a 13+hr flight is never a bad thing), allows the autopilot and flight directors to remain engaged to minimum disconnect height and touchdown respectively and removes the faff of having to wait to set the missed approach altitude on the MCP. In effect, procedurally it is exactly the same as an ILS. Additionally there are airports I’ve flown into where the RNAV minima are lower than the ILS believe it or not, so it’s a slam dunk to use it if the weather is iffy.
If you are getting an IAN in the PMDG when you don’t want one then that means you’ve not set the aircraft up correctly.
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Can you be a little more specific about what this might be? I sometimes get an IAN when I think that I am set up for an ILS. What might I be doing wrong?
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You need to make sure you have both ILS frequencies set on the nav radios and both inbound courses set up on the MCP. Unlike the 787, the FMC on the 737 has no influence on how you fly an ILS, other than it draws a pink string on the map. In the 737 it’s spit and sawdust and just like it is in a light aircraft. Tune the frequency, set the course and fly it.
The reason you’re getting IAN indications is because, I’m guessing, you haven’t set the actual ILS up correctly. In lieu of an ILS signal the auto flight system is doing what it’s supposed to and falling back to the next level of approach, in this case an IAN approach based on what’s loaded into the FMC.
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Well I did check at the time to see if I had the ILS freq set properly in the radios so I am pretty sure that the ils was set. I will try it again. Perhaps that ILS is inop for some reason.
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Easy to forget setting the ILS inbound course on both the pilot and copilot side, as both need to be set as posted above. This can be done enroute, during cruise when workload is light, before descent (can also be done on the ground before departure on very short flights in many cases). Good flying!
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In EASA there’s a limitation called the MUH (Minimum use height). I think the FAA does not have it. That’s the minimum height at which the autopilot can remain engaged engaged during single channel operations (No autoland). In my airline on the 737-800 the MUH is 158ft (140ft AAL on the 737-700). This means the single A/P needs to be disengaged at 158ft or higher.
Additionally we have a rule not to practice hand-fly when above FL200 so technically you could fly manually all the way from FL200 to touchdown (Sometimes I do when reasonable and outside of busy airspace).
On a normal day where you don’t feel like handflying the approach and whenever it’s not reasonable to increase the workload by not using automation I’d say we normally disconnect the autopilot after the landing checklist is completed and the airplane is in final configuration at around 2-3nm from touchdown. Sometimes a bit earlier.
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Thank you very much for your detailed explanation! I’m writing all this stuff down.
At the moment underway to Copenhagen (Kastrup) I’ll practice it straight away.
-Bram
IAN is not a part of the large majority of 737s; it is an option that only some operators use. These tend to be the operators who are trying the hardest to shortcut training profiles; IAN (if you only need to fly the simplest of RNAV procedures) allows the elimination of one or two approach profiles to train.
However, it does not allow for curving or offset approach procedures, the minimums are typically higher (and never lower) than an RNP .10 procedure to same runway… And the autopilot can remain engaged to approach minima (or lower) on any type of approach flown, in my world. I understand it may be different elsewhere.
For perspective, I fly for the 737 operator that invented RNP (AR) procedures 20-something years ago, so we are quite entrenched in that world. I can see how it might be different for an operator that rarely flies RNAV procedures.
Point is, if it’s included in the PMDG, it should be a configurable option, not something that’s just always on… Since the majority of 737s don’t have it installed in the first place.
Practically speaking, unless it’s important to have one less approach profile to train, there is no practical benefit to using IAN. It never gets you lower, it doesn’t reduce workload (there’s nothing simpler than LNAV/VNAV all the way down), and it drastically limits the types of RNAV procedures that can be flown.
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