Question for Jomni, PanzersEast or other Flight Simmers

[jomni]

Which part of FMC usage do you need help on?

[Yskonyn]

Finally logged a flight in the PMDG 737.  Man, that is a tough airplane to figure out.  It's all about the autopilot and computer system.  I handflew it into a landing at Nashville Intl no problem; the thing handles like a dream, but man alive does that FMC baffle me!

Definitely going to need to spend some time with a tutorial or two.

Lol! Exactly how I felt then I transferred from the Fokker 50 to the 737NG in real life.
I knew what I wanted to let the place do, just not how. :) Resulted in me clicking off the A/P and doing it myself oftentimes at first. :P
Funny you have the same experience.

[jomni]

I'm reading the 777 manual. The 777 avionics is actually easier to learn and has many automated functions. But harder to hand fly because it is bigger, heavier, and engines less responsive to throttle input. 

[Yskonyn]

Actually, the bigger aircraft are much easier to fly than the smaller ones. At least in real life.
The only thing you need to be able to do more in the bigger aircraft is 'staying ahead of the aircraft' with your mind. It requires a more proactive approach, but if you manage that the actual technicalities of handling the jet is easier and more forgiving.

[jomni]

First flight in my shiny new PMDG 777 ended with a crash.  No,  not the plane.  FSX crashed on me while taxiing to gate after landing.  Never had the chance to shut off the engines.  :)   Must be the known virtual memory error in FSX but it is the first time it happened to me.  Gotta tweak some stuff.

[Toonces]

Which part of FMC usage do you need help on?

Well, in the tutorial they walk you through doing a SID through airways into a STAR for arrival. 

What I was trying to do last night is simply fly GPS-direct from KATL to KBNA.  As you know, when flying using FSX ATC they're going to give you vectors for the whole smack; usually runway heading then an intercept to direct course, and then vectors to an ILS at the destination. 

I couldn't figure out how to get the FMC to understand the flight plan.  For example, I couldn't get the autothrottle to set cruise speed independent of the autopilot speed bug.  Once I got onto vectors I tried flying it like the lear using autopilot bugs for HDG, SPD, ALT but the VSI bug is confusing- it keeps changing from my preset with each alt change.

On the ILS I got glideslope but no working course needle.

And so on.

I'm positive it's user-error; the autopilot just seems to be so good and automated that getting it to do straightforward stuff is confusing.

[jomni]

Welcome to the world of airliners. Looks like you still have a General Aviation mentality :).

Anyway, for some of your questions:

Changing altitude modes in the 737
1) VNAV - climb based on speed and altitude targets in your FMC flight plan. This takes into consideration distance, weight, fuel, cruise alt, cost index, restrictions, SID/STAR. If you don't key in all the factors in your FMC then you will have problems.  FSX ATC does not see your FMC plan, they can only see what is loaded in the FSX flight planner.  This is a fully automated flight with minimal pilot input. No need for ATC if planned properly.

2) FL Change.  - climb to target altitude by using an angle that maintains the current speed indicated in your control panel.

3) V/S -  user inputted vertical speed.  this is what is normally used when following ATC instructions. This is probably what you want to do

Not sure in there's a target pitch option. I seldom use this option.

To use your own cruise speed make sure that the Speed hold button  is off. But most of the time airline pilots just set their desired speed using the bug anyway. The plane will then do whatever it can to maintain that speed (throttle movement, pitch).

[Yskonyn]

1) VNAV - climb based on speed and altitude targets in your FMC flight plan. This takes into consideration distance, weight, fuel, cruise alt, cost index, restrictions, SID/STAR. If you don't key in all the factors in your FMC then you will have problems.  FSX ATC does not see your FMC plan, they can only see what is loaded in the FSX flight planner.  This is a fully automated flight with minimal pilot input. No need for ATC if planned properly.

During climb, VNAV will try to get as efficiently as possible to your cruise level while taking into account all thats said above.
Usually this results in it being a glorified LVLCHG mode where altitude and speed restrictions are abided by due to the FMC input.

For descent VNAV tries to calculate a path from down to cruising level where it can maintain thrust idle until you start configurating for landing.
It does this while keeping all data in mind like alt restrictions, cost index (and hence desired descent speed), etc.

2) FL Change.  - climb to target altitude by using an angle that maintains the current speed indicated in your control panel.

Not entirely correct; LVLCHG uses max N1 for the given climb thrust mode and alters its angle to the climb speed you set in the MCP.

For descent it reduces thrust to idle and alters angle to maintain speed set on MCP.

3) V/S -  user inputted vertical speed.  this is what is normally used when following ATC instructions. This is probably what you want to do

Not sure in there's a target pitch option. I seldom use this option.

To use your own cruise speed make sure that the Speed hold button  is off. But most of the time airline pilots just set their desired speed using the bug anyway. The plane will then do whatever it can to maintain that speed (throttle movement, pitch).

Now you are using GA tactics, jomni. :)
V/S is not the mainly used mode. For climb its LVLCHG or VNAV, for descent it's the same, although LVLCHG mainly if ATC want you to go down quickly.
Normally you would want to keep it in VNAV for max economy. But you will have to configure the FMC properly.

V/S is used mainly in a couple of situations;

In climb when you approach crossing traffic you reduce to 1000ft/min to avoid TCAS alerts. Same in descent.

Or when ATC want you to descent early, but you want to stay as high as you can as long as possible. Again 1000ft/min is Boeing std.

Then when you're flying visually you often use V/S as well in the last parts of the flight.

There is no real pitch hold mode.

[jomni]

My problem with LVLCHG going down is I fear I will miss the target altitude at a certain way point because the speed is wrong.  V/S is easier to manage but it may be a wild ride. :)

What's the trick for LVLCHG on the way down? I know is should keep the throttles idle, set speed, and the autopilot will adjust pitch (and descend).  But at what speed? Follow FMC VMAs plan?

[jomni]

So many typos and I can't edit them well in my Mobile Phone.

[Yskonyn]

My problem with LVLCHG going down is I fear I will miss the target altitude at a certain way point because the speed is wrong.  V/S is easier to manage but it may be a wild ride. :)

That's called descent planning :) If you want to abide by a certain decscent speed you will need to know when to start descent to reach the various altitude restrictions.
This is what VNAV can do for you if you have entered everything in the FMC. It will calculate a path at idle trust while keeping the altitude restrictions and desired descent speed in mind.

V/S gives you more manual control, but you will loose certain safety 'features'; V/S will adjust pitch to keep the set V/S. Once it had thrust set to idle, but still needs more pitch down to gain the desired V/S it will ignore speed with the danger of going into overspeed.
In a climb you risk a stall if you don't pay attention, because once thrust has been set to Max N1, but it needs more pitch to gain the desired V/S it will let airspeed drop.

That's why it's not advised to use it as a main form of descent or climb mode.

Still, as with all modes, the target altitude window is always kept in mind. So if you get clearance to descent to 8.000ft from ATC, you select LVL CHG but leave 10.000ft in the MCP, the aircraft will level off at 10.000ft, regardless of mode used for descent.
Contrary, if you are worried you'll make the alt restriction, but want to manually control your descent, start early in LVL CHG but keep the MCP set at the next higher altitude limit. You might burn some extra fuel because you're longer at lower altitude, but it's safer than V/S.

If you have entered all data into the FMC, you can use the Vertical Mode Annuniator as a guidance for your descent planning.

What's the trick for LVLCHG on the way down? I know is should keep the throttles idle, set speed, and the autopilot will adjust pitch (and descend).  But at what speed? Follow FMC VMAs plan?

Like above; the VMA is a good guidance to see where you are in relation to its calculated path IF you have entered all data correctly. But remember that this VMA is a calculated path and might contain errors. In the real aircraft VNAV can be a bit finnicky to use, but that's a long story.

Descent speed is usually something the company wants. Cost Index results in a descent speed. (look in the FMC).
In LVL CHG you select that speed in the MCP and it will keep it.
ATC or local rules can of course demand other speeds than those that are desired by the company. You will have to either manually enter those into the FMC (many SIDs and STARs have correct speed limits in the FMC database, but not all, so verify!) or you will need to manually set those in the MCP and then fly in either LVL CHG or V/S mode. Updating each altitude limitation in the MCP as you pass the next waypoint. This will result in a stepped down descent rather than a continuous one.

Another option is to use the 'Speed Intervention' button (on the MCP, but not on every type of 737NG) if you fly in VNAV. This will open up the MCP speed window so you can select a speed like in LVL CHG to override the calculated FMC speed. This will fuck up your VMA though, because all of a sudden speed changes and it need to recalculate.

A general handy rule of thumb to use is the M's (meters) button on the CDS. You will now get M readout above your altitude indicator.
Your altitude in M's / 100 gives you your roughly needed trackmiles to get down.
You might need to configure PMDG to give you the M option.

Hope I am making sense. :D

[Toonces]

Welcome to the world of airliners. Looks like you still have a General Aviation mentality :).

Anyway, for some of your questions:

FSX ATC does not see your FMC plan, they can only see what is loaded in the FSX flight planner.  This is a fully automated flight with minimal pilot input. No need for ATC if planned properly.

Right, I got that.  I want to use the FMC and ATC. 

What I'm probably going to need to do is load a flight plan in FSX, and then also enter that same flight plan into the FMC and hope the sinc up; or else make changes to the FMC as assigned by ATC when I get my clearance.

I don't want to fly either/or.  That defeats the whole purpose of having this uber-real airliner to fly.

[Toonces]

You know what is interesting, and I may have said this before, is that I'm a former P-3 pilot.

In the P-3, we don't do anything via autopilot.  The best we can hope for is (or was) a working altitude hold.  That was it.  The only P-3 I was ever in with a working 3-axis autopilot was the pax version P-3A ("Valkyrie") that was homeported at Keflavik.  Every other P-3 I flew, we NEVER flew with more than alt hold because if you put all 3 axes on it would likely overheat the autopilot and you'd have no autopilot at all.

That wouldn't seem like a big deal except you can't trim a P-3 for level flight.  Period.  No matter how perfectly you trim the plane it will never hold its attitude.  It's even in NATOPS that it will slowly porpoise around a given attitude even in perfect trim.  So if you killed your alt hold (or if you never had it, about 10% of the time) those 9 hour reposition flights just plain sucked.  Bad.

As far flight management, there was no such thing.  Like I said, you had alt hold and that's it.  The rest was pure pilotage.  We got GPS integrated into the cockpit while I was there.  Before that, if you had a handheld GPS we'd use that to "verify" our intertials, but you couldn't navigate via it by instruction. 

The P-3 was very hands on to fly.  It was pure hand flying.  We had the capability for ILS but Navy fields use "PAR approach": http://en.wikipedia.org/wiki/Precision_approach_radar
where a controller gives you verbal vectors on heading and glideslope; very much a verbal ILS.  I personally preferred the ILS at civilian/Air Force fields, but some guys preferred the PAR.  So even on a good day you would hand fly it to localizer and then get talked in.  It worked, but you had to get a feel for the controller and your particular plane's idiosyncrasies; if it was on heading, how it yawed, etc.  There was a lot of technique involved.  And each controller had a style, so you had to juggle all of this stuff and average it out into a control input.

I only had one real time where we were no-shit outside of mins and had to try to get a plane on deck below mins.  We were flying into Misawa, Japan one night and they just had full on zero-zero fog onstation.  We were coming in late at night and weather was clear and a million above about 200' and then zero-zero below.  I was at controls and my plane commander was in the right seat.  We decided to do an approach, can't remember what it's called now, where I'd fly the approach and when the runway was acquired by the right seat he'd take control for landing so I wouldn't have to transition from instruments to visual.  My head was in the cockpit the whole time and at MA if he didn't have the runway we'd waveoff and go around.

My first approach was, unfortunately, my best.  I nutted the PAR and hit our 200' mins and we got the runway lights in sight.  Unfortunately, what we had was one set of lights to our right, one down our middle, and nothing to our left.  So real quick we're saying "Does Misawa have centerline lights?!!!" while we're still descending onto maybe runway, maybe grass.  At about 50' (this all happened in about 5 seconds) we call waveoff!  and bam we're back up. 

It turns out Misawa doesn't have centerline lights, so our left gear was in the grass.

We shot about 5 more approaches, but I just couldn't nut it like that first one.  Each subsequent approach was just a little high, or fast, or whatever, but I couldn't hit mins on speed and alt at the right spot, and we never got such good visual to even try to get down.  You'd get this glow of lights, but not enough to put it down.  We ended up diverting to Atsugi and then the plane broke down and we were stuck there for a week!

Anyway, my point is just how different all of this autopilot stuff is to me.  I'm quite a competent pilot, but I want to do it the correct airliner way, and that means mastering the FMC.  In many ways I think this is harder than manually flying the plane as you really need to understand the plane's systems in more depth than you might otherwise know them.  I'm struggling, but I enjoy the challenge.  I don't want to take the easy way out and just "fly" the plane, as tempting as that is!

[jomni]

Nice story.  You can nail that landing with modern avionics.

Airliners are so particular with fuel efficiency that proper (computer aided) planning is needed.
Then you need a fancy autopilot to fly the plan.

Sadly, It's all about managing the computers these days. Which is a different kind of flying.  Piloting skills are still needed when there are system failures and emergencies.  Maybe next in planes will be unmanned.

[Yskonyn]

Great story Toonces. I can relate to that in a lesser sense; I have flown the Fokker 50 where we only had V/S, atltitude hold and an APP mode. No autothrottle.
The autopilot didnt work a lot of the time either.
It was mainly hand flown.

When I went to fly the 737 I felt exactly the same as you just described! :) Often just getting rid of the Autopilot and do it myself because I knew what I wanted to do, just not how to quickly control the A/P to do so.

One thing I am very glad for is the fact I did fly in a much more hands-on environment before. It's there that you learn to fly.
No to piss on others, but you often see a completely different mindset of pilots who know only glass cockpit style flying.
Gives even more food for thought about that MPL license that goes around, where students are trained for a specific type from day one of flight academy. The course is almost all simulator based...
They do not fly their hours in GA to get a license. They do not get their wings in the military. Just computer based training and afterwards they fly across the ocean with 400 people on board...