Sign in to follow this  
jgoggi

Big useless turn during descent

Recommended Posts

Hello,on nearly all flights I make with RC4.01, when I am descending to say 10000 ft and I am at say 12000 ft, I get instructed to pick up a heading about 90 degrees from the one I am flying, and to resume my navigation when reaching those 10000 ft.It usually happens that when I have almost reached 10000 ft the turn has just initiated, so no use that I continue deviating 90 or more degrees away.Is there a way to avoid that annoying turn? Or at least to have it happen not everytime but once in a while?Thanks,James

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

it's not a big useless turn. you didn't meet your crossing restriction, you're not allowed into approach airspace until you do, so you are vectored 90 degrees left or right of course until you are at the assigned crossing restrictionjd

Share this post


Link to post
Share on other sites

JD, you mean that when I get that instruction I should have already reached 10000 ft? Sorry for misunderstanding, I thought that was a turn assigned in order to get spaced with traffic ahead, that's why I thought it was strange that I got it almost every flight. It was my fault that maybe did not reach the assigned altitude.

Share this post


Link to post
Share on other sites

do a quick scan of the manual for crossing restrictions. it will be all explained :-)jd

Share this post


Link to post
Share on other sites

In the real world crossing restrictions are used to seperate traffic vertically as well as the expected horizontal seperation not just from the destination traffic but other airports in the vicinity.You can see such cases in both DPs and STARS. If you wish to look at a few plates from the US go to www.flightaware.com. Click on Resources. Use as samples these airports in one of the most congested areas of the US known as the Northeast Corridor. These are KEWR, KJFK, and KLGA - Newark, New Jersey (Just WNW of NYC),; Southern area of NYC; Eastern area of NYC - all in very close proximity. You can select some STARS or all of their plates in one .pdf.While RC does not look at specific altitudes for each plate (altitude restrictions are not in FS9 flightplans) it follows a general stepping down in the enroute to approach area typical of most STARS. As an example vertical seperation is used to keep arrivals lower than departures at the same airport where they are being vectored outbound toward the paths of inbound traffic.If you look at a STAR or DP you will often see altitude restrictions in the form of at, at or above, or at or below further seperated by generic aircraft performance types (turbo-prop or jets). Look for statements like jets must cross at xxxxx at a maximum speed of xxx.While RC can not have a database with each procedure in the world, it does a good job of generalization including also the vertical seperation of arrival/departure jurisdiction from enroute jurisdiction airspace.If you wish to see of mix of traffic in these areas choose the live tracking feature of flightaware for these airports. By color it will seperate arrival/departure aircraft from aircraft enroute of going/leaving different airports and give the flightnumber or tail number, aircraft type, altitude, and ground speed of each target.You will quickly get an idea of why crossing restrictions are needed.I have some Jeppesen or other source chart reproductions that came with the Spanish Airport collections of payware scenery from Aerosoft. For major areas a terminal radar chart is provided that shows mapped the max/min altitudes of the different radar zones and probably how they are divided amount controllers. In the US for class B airports some have those on a TCA chart overlaying a VFR map showing the maximum/minimum controlled altitude airspace. You might find those scanned into files on the AVSIM libraries by Matt Fox. Try Flightsim.com as well for those. I purchased one for my local area in Minneapolis.I just wanted to give you a background of why these crossing restrictions exist and why RC simulates them as best it can.

Share this post


Link to post
Share on other sites

JD,This one interests me as I sometimes get this message from ATC even though I'm within only a few hundred feet of the assigned altitude as I enter approach airspace.Have you got a tolerance to say that if the aircraft is CLOSE but not yet level you will turn a blind eye to the failure to comply?Or would I get treated this way in the real world even if I were just shy of levelling out? :-)Also, given that the instruction says to "start down now, I need you level in 30 miles or less", is the calculation of the crossing restriction based on a point 30 miles ahead of me on my flight path, or is it based on a fixed distance from the arrival airport?If it is the latter then I can enter the altitude as a crossing restriction in my trusty FMC and make your day easier!Chrs

Share this post


Link to post
Share on other sites

the altitude deviation on the options page is what i use to determine if you are close enough or not.the 30 miles or less, is given about 70 miles from the airport, as the crow flies. that means you should be at the crossing restriction altitude when you are 40 miles dme from the airportjd

Share this post


Link to post
Share on other sites

>Also, given that the instruction says to "start down now, I>need you level in 30 miles or less", is the calculation of the>crossing restriction based on a point 30 miles ahead of me on>my flight path, or is it based on a fixed distance from the>arrival airport?>>If it is the latter then I can enter the altitude as a>crossing restriction in my trusty FMC and make your day>easier!As standard practice, I create a waypoint that is ~45 miles from destination and set an altitude of 11000 (most of the US), 15000 around KDEN or MMMX for that waypoint. In this way, my TOD calculation is based on that point. This allows me to plan to be down and also to slow down before entering approach airspace.-michael

Share this post


Link to post
Share on other sites

Another little tip that probably is already well known, and also dependent on the particular FMCs capability, is to enter the arrival airport as a fix and then set a 40 mile range circle from it. Gives a good visual clue at where to expect to be at around 11000ft.

Share this post


Link to post
Share on other sites

yes, good tip, I always use it with the PMDG 744 and I also put a 60 miles ring to know where approximately start getting the arrival ATIS.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this