Radar Contact & Flight Plans :: A question of realism

[B1FS 0]

Hello everyone.

 

I've not posted much on this site, so please do excuse my ignorance if this is not the right place to ask this question.

 

I have been using Radar Contact V4.3 with PMDG Ngx for a few days now. I use flight plans made in vRoute (exported to pln files), which are uploaded on Radar contact.

 

My question is one of realism, in terms of the radar controller's instructions. 

 

Usually, I get cleared to fly planned route as filed, and climb to say 5000 ft after take off. In my FMC on the PMDG, I have waypoints with speed and altitude targets, as you know, and I usually use the LNAV/VNAV mode with autopilot.

 

However, sometimes, the controller will tell me to expedite my climb quite early (for example, my next waypoint altitude target maybe 300ft but he will ask me to climb immediately). I usually then switch ALT HLD and VS to achieve this, but it does throw my planned flight completely off course, I then have to change the target altitudes at the various waypoints ahead.

During descent, the same thing happens, they ask me to descend well before the TD point, and always expedite the descent. 

 

To all of you who fly for real, is this how it happens in real life? I had thought that SID/STARS have these targets for a reason (weather, wind, traffic etc). Is it ok to bust these constraints based on the ATC's instructions?

 

Also, I have another question. In heavy weather (crosswinds), the aircraft sometimes maintains a heading different from the intended heading to compensate for the crosswind. But the Radar Contact ATC immediately tell me I am offcourse, and ask me to turn in the opposite direction (which at 0.8 Mach is rather long and laborious). I sometimes correct with HDG SEL manually, but it does detract from the smooth flow of the game!

Am I doing something wrong here?

Please do help! I'm flying ENGM-EKCH today :-)

[ronzie 21]

In your FMC there are hard coded altitudes and those that adjust dynamically based on your status and performance.

 

Note that on published SIDs and STARs many waypoint altitudes have the notation to "expect" to cross at an altitude. ATC controllers have the final say so just use your MCP to adjust and the rest of your non-fixed altitudes will adjust. Use V/S if necessary and watch the trend arcs on the NAV display.

 

For descents the FMC altitudes predicted will be off to meet the fixed crossing restriction at 40 nm out from destination. The FMC predicts altitudes from your current location to airport surface. RC predicts your TOD based on meeting the crossing restriction at 11,000 or 12,000 feet (or FLs) at 40 nm out.

 

In your NGX for descents preflight put a range ring fix around your destination. Use the FIX page entering the ICAO code and for the distance/bearing enter /40 and EXE. Use /30 to place another to assist in determining the traffic pattern speed limits. Again, use the descent arcs making sure they terminate before the range ring for altitude restrictions at 40 nm out.

 

CDAs are not supported by RC. Their use in the U.S. is very limited.

 

Somewhere there is another thread regarding this in the V5 thread.

[B1FS 0]

In your FMC there are hard coded altitudes and those that adjust dynamically based on your status and performance.

 

Note that on published SIDs and STARs many waypoint altitudes have the notation to "expect" to cross at an altitude. ATC controllers have the final say so just use your MCP to adjust and the rest of your non-fixed altitudes will adjust. Use V/S if necessary and watch the trend arcs on the NAV display.

 

For descents the FMC altitudes predicted will be off to meet the fixed crossing restriction at 40 nm out from destination. The FMC predicts altitudes from your current location to airport surface. RC predicts your TOD based on meeting the crossing restriction at 11,000 or 12,000 feet (or FLs) at 40 nm out.

 

In your NGX for descents preflight put a range ring fix around your destination. Use the FIX page entering the ICAO code and for the distance/bearing enter /40 and EXE. Use /30 to place another to assist in determining the traffic pattern speed limits. Again, use the descent arcs making sure they terminate before the range ring for altitude restrictions at 40 nm out.

 

CDAs are not supported by RC. Their use in the U.S. is very limited.

 

Somewhere there is another thread regarding this in the V5 thread.

 

Hello Ronzie,

 

Thank you for the detailed reply! Seems like some of that went over my head, and I really need to get to learning a lot more about these things. I have a few more questions for you.

 

When the controllers expedite a climb to say FL230 from FL150 and your next waypoint on the FMC has an altitude of say FL160, and say another waypoint some distance away has an altitude of FL230, do we set our V/S so that the trend arc coincides with latter waypoint (if this is possible), or do we just climb as quickly as we can?

 

I understand your points regarding the 40nm restrictions in altitude while descending to an airport, as that once clearance is obtained to the lowest altitude possible before entering the approach pattern, this altitude must be achieved before the 40nm radius around the airport as set in the FMC using the FIX command right?

 

Please excuse my English. It's not my native language. 

And thank you so much for your help. 

[ronzie 21]

You are bound to follow ATC's instructions unless you perceive a dangerous error and then request intervention. If your aircraft can not comply request a change from ATC. If expedite is not requested you can do a cruise climb but you have to start on command with at least about 200 feet per minute. Any slow down in V/S or reversal will get an immediate correction from ATC.

 

Unless you are getting ready to cross a nearby waypoint, hold off acknowledging RC's command until your climb (or other action) starts to hold off nasgging by RC's impatient controller's. Do ack, though, before crossing a waypoint or RC will not see you cross it.

 

Once again, ATC is the boss, not your FMC. The FMC altitudes will adjust as necessary unless you placed a restriction in it in which case you take control away from it to comply with ATC instructions.

 

Very often you may find ATC issuing another climb or descent before reaching the target altitude in order to give you an expeditious continuous climb or descent.

 

The FMC is an assisting device, not a substitute for ATC. Learn how to make the FMC and your aircraft comply with ATC commands.

 

As an example on a climb or descent, if in VNAV mode, your climb or descent wil not go beyond the limit you place using the MCP ALT setting which places a limit on what your aircraft will do even if a higher or lower altitude is in the FMC display. Say your FMC indicates a higher altitude than ATC commands. Just have the ATC issued altitude set in the ALT indicator and raise it when ATC clears it.