To:Ryan Maziarz-PMDG

 

What a great job you and your editors did on tutorial#1!

 

i have a few problems understanding the following though;

 

"In the event you wanted to do a normal CAT I-style ILS approach where you don't autoland, you would just tune one radio to the ILS frequency. When you engage both autopilots in this case, you'll see SINGLE CH annunciated on the PFD in amber, letting you know that you do not have dual autopilot redundancy and can't perform an autoland. In this case you'd disconnect the AP at the decision height and land manually. "

 

1.This is counter-intuitive, can you explain why tuning both nav 1s to the same frequency yields "Single CH"?

 

2. Why we would set MCP altitudes counter to the legs settings in the FMC? I understand that the MCP over-rides what ever is set in the FMC.

 

....we seem to be doing a lot of needless altitude intervenes, when to my simple-minded understanding, we should not need ANY MCP settings, other than reminders. The FMC route-legs settings for speed/heights should/do include any speed or height restrictions, do they not?

 

So, in this tutorial, why, do we need to set auto-throttle speed, and altitude in the MCP??

 

Still a Tube noob... But studying...

 

regards to all,

 

chas

 

Thanks,and have a wonderful day!

 

Just this side of heaven is a place called Rainbow Bridge.

 

When an animal dies that has been especially close to someone here, that pet goes to Rainbow Bridge.

 

http://www.petloss.com/rainbowbridge.htm

 

 

Chas (iPD)

 

Please visit www.katrinasangels.org

 

 

This is counter-intuitive, can you help me explain this and also why we would set MCP altitudes counter to the legs settings in the FMC....we seem to be doing. Lot of needless altitude intervenes, when to my simple-minded understanding, we should not need ANY MCP settings, because the FMC route(legs) speed/height

 

...and here is where I cringe a little, but until someone explains this all to you in greater detail, it may be confusing.

 

Okay.

 

There are two things at play here: the FMS and the MCP.

 

The FMS (flight management system), comprised of some FMCs (flight management computers), and controlled by your CDUs (control display unit - what you type on to input the route, etc.) is what you use to guide your entire flight.  It is there for the number crunching to assist you in accomplishing you in doing your job.  It is not there for you to feed it data and become a slave to it (like many assume - not just you alone).

 

The MCP is the keeper of the aircraft, second only to you.  You are at the top of the food chain because you could fly the aircraft the whole entire time.  In order to give yourself a break, though, you normally put the aircraft under the control of the autopilot (AP).  When following LNAV and/or VNAV, the MCP is utilizing the data from the FMC to guide itself.  Absent that, you could control the whole flight via heading select, VOR/LOC, FL CH, V/S and ALT HOLD if you'd like, but that would be more work.

 

I know you may already know this, but I'm trying to paint a picture here of separation of power and hierarchy.  The FMC is actually at the bottom of the food chain, despite its power.  It has immense power to help me out in many ways, but it only knows as much as is contained in the database.

 

It does not know what the controller just told you.

It does not know what the destination weather is unless you tell it (DES FORECAST page).

It does not know what the wind is in the future unless you tell it (RTE DATA pages).

It does not know what the terrain looks like in between you and a point ahead of you (it will fly you into a mountain unless you give it an altitude restriction to otherwise keep you above it).

 

...and I could go on.

 

The box is there to make life easier, but you can't rely on it assuming it knows everything.  Setting altitude restrictions on the MCP essentially tells the system "you can take care of the altitude until this point, at which you must stop."  Why?  Many reasons, such as ATC only clearing you to that altitude, there being mountains you must remain above, and others.

 

Always remember, you're still up there controlling the plane and not just a computer: humans still know more than the automation.  Just because the FMS calculates the optimum altitudes along the descent does not mean that those altitudes are appropriate - they're simply efficient - and efficiency goes out the window when you hit a mountain, or another aircraft.

 

 

 

 

Additionally, the tutorial was showing you other AP modes to broaden everyone's knowledge.  LNAV and VNAV are not always appropriate to use.

Holy crap!!!!!

 

I am completely blown away by the immediacy of your response and it's depth!

 

I would've responded sooner, but I do not have a BMC, being assigned a new school school route I needed to be physically taken to and shown where my waypoints were!

 

More later after I have digested your teknikal tome...us Appalachian boys are a lil'slow sum times..., but I wanted to respond ASAP

 

Thanks again.

 

Chas

 

 

When you engage both autopilots in this case, you'll see SINGLE CH annunciated on the PFD in amber, letting you know that you do not have dual autopilot redundancy and can't perform an autoland. In this case you'd disconnect the AP at the decision height and land manually. "

1.This is counter-intuitive, can you explain why tuning both nav 1s to the same frequency yields "Single CH"?

 

Because you have both APs on, but only single channel is operating.

 

In the quote it is a bit confusing, as SINGLE CH is a normal annunciation in case of autoland - until the second AP is taken online, when it becomes LAND, LAND2 or LAND3 (depending on aircraft, equipment, current malfunctions etc.). If you have no LAND annunciation by the time you hit some 1000ft AAL, you should expect an autopilot disconnect as the aircraft is unable to engage the other channel(s) for whatever reasons.

Thanks Fabo!

 

My question is: could we have taken off, and auto landed in the PMDG NGX tutorial #1,without any MCP intervention in either altitude or speed?

 

OK I give you take-off for climb speed and alt, but once we have achieved the 400/50 foot engage points for Vnav and LNav, do we really need either ALT Hold or MCP speed?

 

Of course this assumes that ALL the speed and altitude restrictions were programmed into the CDU, for climb,cruise, descent,approach and auto-landing IF;

 

1. BOTH autopilots are engaged, AND;

2. Both NAV 1 ILS frequencies(PIC & FO) set to match, for autolanding.

 

After a little research, and I seem to have had an epiphany! Attributed to the following insights.

 

As Kyle Rodgers (scandanavian13), aptly pointed out, the hierarchy of control in the cockpit is,

 

YOU->

MCP->

CDU

 

...and yes, Virginia... and Chas...you could probably do what I described above...BUT,!!

 

There is the REAL world, and that is where changes in speed and altitude can and apparently DO OCCUR...

 

....WITH EVERY FLIGHT...you have to listen to and obey the dictates of common sense when encountering adversity or

 

.... A. T. C. !!!

 

 

...DUH, CHAS!!!

 

...read on...

 

 

In the short time i took for the research into the question of why intervention?, I have now created a new home page on my ipad called, "Speed & Altitude MCP vs CDU" , and stuck it in my flight study folder.

 

It refers to this excellent explanation of altitude and speed intervention, a portion of which is quoted below from http://www.flaps2approach.com/journal/2013/2/20/speed-altitude-intervention-sd-intv-alt-intv-v-nav-how-to-us.html

 

"VNAV, MCP & FMA

 

An often misunderstood facet of the MCP is that the illuminated lights indicate whether a function/mode is turned on or off. This is not entirely correct. Illuminated lights indicate modes that can be switched off. Active modes that cannot be switched off, extinguish their light on the MCP. A pilot (virtual or otherwise) would be foolhardy to rely solely on this method to determine the operational status of a mode or function and cross referencing with the FMA and CDU is considered wise.

 

The Flight Mode Annunciator (FMA) seen above the Primary Flight Display (PFD) displays various alerts and status messages and it’s prudent to cross reference between the FMA, MCP and CDU to determine what exactly is happening at any given time. When a function is about to be executed, the FMA will draw a green rectangle around the function.

 

If in doubt, always disengage V-NAV and then reengage after studying your predicament.

Speed Intervention (SD INTV) & Altitude Intervention (ALT INTV) – Why?

 

The flight deck can be an extreme work environment, especially during the high-task descent approach phase of the flight; speed and altitude intervention were designed to allow pilots to easily and quickly change either the speed or altitude of their aircraft without re-programming the CDU or disengaging VNAV. The intervention buttons are strategically located on the MCP and when engaged (pressed) allow you to quickly change either speed or altitude level on "the fly". To engage these buttons they must be depressed for one to two seconds.

 

Scenario

 

You are flying at FL280 (28,000’) at 300 kias (.54 Mach). The CDU has a flight plan engaged (Company Route) and the CDU LEGS page specifies speed and altitude constraints. VNAV, LNAV and CMD (A or B) is engaged. The speed window located on the MCP should be blank (one indication that VNAV is engaged) and the V-NAV, L-NAV and CMD A or B indication buttons will be illuminated.

 

LNAV will be controlling the lateral navigation of the aircraft while VNAV will be controlling the altitude of the aircraft relative to the altitude and speed constraints that have been set in the CDU.

 

You have been asked by ATC to decrease your speed to 280 kias and lower your altitude to FL260."

 

And from "Cockpit Companion" by BIll Bulfer below, this very cool and soberingly inclusive chart ....what REALLY happens when you press the Alt Hold or Intervene.

 

...so I appear to be on the road to answering my own question...with thanks to all mentioned above...life is grand with such sterling and responsive blokes out there!

 

Chas

Just because it's become pretty much mandatory in topics like this: http://youtu.be/h3kREPMzMLk

Great addition Thomas!

 

 

My question is: could we have taken off, and auto landed in the PMDG NGX tutorial #1,without any MCP intervention in either altitude or speed?

 

In theory, yes.