Hi guys,

 

I have been practicing the aerosoft a320 a lot lately. I have a question about the autopilot not following the altitude constraints in the mcdu?

 

If my first constraint is let's say 4000 ft should I choose 4000 with the altitude knob en press it? My next wat point is 6000 altitude constraint but I have still 4000 dialed in. The plane does not automatically go to 6000 ft although the flightplan says so. Should I dial in 35000 ft for example in the fms and let the plane decide to climb at each waypoint untill the constraints are over?

I'm a bit confused. I thought the plane just followed the exact flightplan with its constraints but apparently it doesn't...

 

Thanks for any help??

 

Cheers

Jozeff

A good rule of thumb when dealing with FMS altitude constraints is that the vertical mode is limited to the Altitude you have preselected on the FCU (AP panel). 

in Short: the plane will not fly higher than FCU altitude during climbs and it will not fly lower than FCU altitude during a descent. 

Most pilots use the altitude window on the mode control panel as a 'guard', i.e. they will dial in the altitude they have either been cleared to by ATC, or the next altitude on their flight plan if following own navigation. They do this because most autopilot MCPs will not let the aeroplane go past the number set in the altitude window regardless of what other autopilot modes you are using, so it acts as a good visual reminder of what altitude you are currently cleared to, and it can override the VNAV modes.

This is a useful safety feature in case ATC have not actually cleared you to an altitude on your flight plan. If you watch most crews working an airliner, you will see that almost all of them go straight to the MCP and dial in the number ATC have cleared them to the moment they hear it, and before they do anything else.

Also of interest...

Be careful with the MCP on an A320, it has a lot of weird modes including FPA (flight path angle), which has in the past been confused with descent rate, most famously in the Air Inter Flight 148 crash in 1992. The crew thought they had set the FPA mode to 33, to give them a 3.3 degree descent angle for their approach into Strasbourg, but they had inadvertently left it in Vertical Speed Mode, which gave them a descent rate of 3,300 feet per minute and resulted in them flying into the side of a mountain in the Vosges in poor weather and darkness whilst they were circling to land.

The MCP controls were redesigned a little bit visually following this accident, and pilots were told to stop exceeding 250 knots below 10,000 feet (they did that a lot back in those days in France in order to compete with the 200 mph TGV trains which were having an effect on airline ticket sales), Air Inter's A320s were also not fitted with a ground proximity warning system specifically because it would go off all the time when their pilots were exceeding 250 knots below 10,000 feet. Air inter were ordered to fit them after this accident, but in fact they realised this was a stupid omission and did so before they were actually ordered to.

This was one of the (several) accidents at the time which were mainly attributed to pilots not being used to the various autopilot modes the then-new Airbus A320 had, leading to it gaining the nickname of the 'scarebus' and the phrase, 'if it ain't Boeing, I ain't going'. Funny how times change eh? Now people don't want to get on the Boeing 737.

If you are puzzled by the intricacies of the A320 and want to get seriously into it, I can recommend this book. Or this cheaper PDF version. It'll explain everything about the Airbus in an entertaining and informative way.

Wow! Thanks a lot chock and sas!

Very helpful and informative. I can't believe you guys respondef so quickly.

 

Good stuff!

 

 

Cheers

Jozeff

Hi Jozeff,

Just to extend the discussion a little bit further, what the guys above said about the FCU is spot on.

 

On the MCDU side of the Airbus, essentially your first expected cruise altitude is usually input into Init A of the flight computer e.g. FL350 but as mentioned the aircraft will still honor the hard limit set on the FCU

In the MCDU on the Flight Plan page  you will see magenta altitudes or Flight Levels called out if there is a procedural altitude/FL restriction in place during the climb. Assuming the FCU is set appropriately these altitude/FL restrictions will be honored automatically by the aircraft.

 

I am also flying the "Bus" on an around-the-world tour in P3Dv5.1 and am enjoying it immensely.

I will also give cudos to Aerosoft that I am amazed (positively) how powerful the MCDU functionality is. I have finally managed to figure out how to make the RNAV approaches work and am currently "experimenting" with VOR approaches as a I visit different airports around the world.

 

6 hours ago, jozeff said:

Hi guys,

 

I have been practicing the aerosoft a320 a lot lately. I have a question about the autopilot not following the altitude constraints in the mcdu?

 

If my first constraint is let's say 4000 ft should I choose 4000 with the altitude knob en press it? My next wat point is 6000 altitude constraint but I have still 4000 dialed in. The plane does not automatically go to 6000 ft although the flightplan says so. Should I dial in 35000 ft for example in the fms and let the plane decide to climb at each waypoint untill the constraints are over?

I'm a bit confused. I thought the plane just followed the exact flightplan with its constraints but apparently it doesn't...

 

Thanks for any help??

 

Cheers

Jozeff

Have their A330 Pro.

 

Update it? set to show experimental then update again?

 

Try dialing in altitude then right click on it.

 

Also had to edit the aircraft.cfg to modify/fix the autopilot/autothrottle FLC issue on it. Beta might've fixed it but haven't checked yet!

 

If your interested to try it out on the A320 just ask how i did it.

Edited January 19, 20215 yr by 40track
Edited.

Most airlines I know of would fly the climb with altitude constraints in managed mode; meaning the aircraft will fly what you have programmed into the FMS.

Let's assume you are cleared to FL 120 but there are altitude contraints of 5000, 7000 etc. you dial in 12000 and push the altitude knob. The ac will start to climb

and respect the constraints automatically. This is what the FSLabs Bus and the real aircraft do. I do not have the Aerosoft Bus but I assume she would do the same

as this is a pretty basic function.  Dialing in constraints as they come and pulling is called selected mode, I don't know of any Airbus pilot who would do that.

Have fun with the Bus, it's a great aircraft.

Peter

 

Edited January 20, 20215 yr by Petermuc3