novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

Explain The Various Autopilot Modes Of Operation

Sun Feb 17, 2013 11:27 pm

Abstract:

"Based on a B737-300 autopilot system, the autopilot modes of operation are normally the following:

1. Heading
2. Lateral navigation (LNAV)
3.VOR/LOC
4.Altitude hold
5.Vertical speed
6.Level change
7. Vertical navigation
8.ILS/approach"

What would be the difference between heading mode and lateral navigation mode?
Also i would like to know what the difference between these two modes; Level change, Vertical navigation?

Thanks
 
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Starlionblue
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RE: Explain The Various Autopilot Modes Of Operation

Sun Feb 17, 2013 11:46 pm

While there are no doubt nuances, as I understand it the differences you are asking about have to do if the autopilot is getting its input directly on the autopilot panel ("go here") or following a profile from the flight management computer. The equivalent on a simpler aircraft would be if the autopilot is following the heading bug or getting an input from a GPS.

Quoting Novice (Thread starter):
What would be the difference between heading mode and lateral navigation mode?

Heading mode follows a heading, for example 270 degrees. Lateral navigation follows a lateral navigation profile from the FMC, for example a route with waypoints.

Quoting Novice (Thread starter):
Also i would like to know what the difference between these two modes; Level change, Vertical navigation?

Level change is used to change between two altitudes. Vertical navigation follows a vertical navigation profile from the FMC, for example a step climb.
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Horstroad
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RE: Explain The Various Autopilot Modes Of Operation

Sun Feb 17, 2013 11:50 pm

1 follows a certain heading for example 340°
2 follows the route you entered in your FMS
3 follows the signal to or from a VOR/LOC, frequency might be entered manually or given by the FMS
4 holds the altitude while you have lateral control
5 holds vertical speed until you intercept the selected altitude
6 climbs/descends to the selected altitude while holding the selected speed. sets thrust to maximum in selected mode and adjusts pitch
7 VNAV follows the vertical component of the route entered in the FMS (climb/descend sequences)
8 follows glide slope and localizer to the runway and auto lands if available



might not be 100% correct... I'm just a hobby pilot... but it might give a basic overview

[Edited 2013-02-17 15:51:03]
 
novice
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Joined: Tue Aug 07, 2012 2:55 pm

RE: Explain The Various Autopilot Modes Of Operation

Mon Feb 18, 2013 12:26 am

Thanks for the answers guys   
 
Fabo
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RE: Explain The Various Autopilot Modes Of Operation

Mon Feb 18, 2013 2:44 pm

Quoting horstroad (Reply 2):
sets thrust to maximum in selected mode and adjusts pitch

Or minimum. You know, when you want to descend  
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3rdGen
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RE: Explain The Various Autopilot Modes Of Operation

Mon Feb 18, 2013 3:14 pm

On Airbus it is called managed or selected i.e. Managed by the FMC (Boeings LNAV Mode) or Selected (HDG Mode) by the pilots.
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Mir
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RE: Explain The Various Autopilot Modes Of Operation

Mon Feb 18, 2013 5:29 pm

Quoting horstroad (Reply 2):
6 climbs/descends to the selected altitude while holding the selected speed. sets thrust to maximum in selected mode and adjusts pitch

Only if you have autothrottles. If you don't have autothrottles, FLC mode will just work with whatever thrust the airplane is putting out. Which creates some humorous situations when people try to control the speed with the throttles while in FLC mode, and then wonder why the airplane isn't climbing.

-Mir
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Pihero
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RE: Explain The Various Autopilot Modes Of Operation

Mon Feb 18, 2013 7:57 pm

A quick course non Airbii :
Two axises : Lateral and Vertical
One autothrust.
Two ways of selection : either "managed" or " selected"

Soooo...

LATERAL
1/ Managed
- Nav ; App Nav ( that's approach nav )
- LOC
- RWY
- RWY TRK
- GA TRK ( go-around track , the prajectory for a missed approach )
- ROLL OUT ( Guidance on the runway at the end of an autoland )

2/ Selected
- HDG / TRK

VERTICAL
- SRS (Speed reference system, workis with a set thrust, normally TOGA )
- Climb / Descent ( equivalent to B's VNAV) where we follow a climb or a descent profile as computed by the guidance system.
- ALT and ALT CRZ ( the latter confirms we'ra foillowing the computed and stored level.
- G/S, pendant tto LOC
- FInal ; Final APP
- Flare

SPEED
- Managed function of FMGS program...
- Selected

For manual selections :

LATERAL
- HDG / TRK

VERTICAL
- Open CLB
- Openj DES ( both CLB and DES are the equivalent of B's LVL CHG )
- VS / FPA

SPEED
- FCU reference.

Hope that helps
Contrail designer
 
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glen
Posts: 273
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RE: Explain The Various Autopilot Modes Of Operation

Tue Feb 19, 2013 5:34 am

Quoting Pihero (Reply 7):

I was already preparing a post to give an overview of the Airbus systems and I am sure it would not have been so complete.
On the other hand Pihero also misses one (important) autoflight mode:
At 400ft AAL the autoflight changes from G/S and LOC into LAND mode.

The LAND mode, together with the FLARE mode already mentioned by Pihero, is a so called common mode, as it includes lateral and vertical guidance.
"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
 
Pihero
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RE: Explain The Various Autopilot Modes Of Operation

Tue Feb 19, 2013 9:55 am

Quoting glen (Reply 8):
The LAND mode, together with the FLARE mode already mentioned by Pihero, is a so called common mode, as it includes lateral and vertical guidance.

You're correct, of course
I also omitted, this time voluntarily, all the armed modes - a.k.a the * modes - in order not to confuse.
Contrail designer

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