Regulation for large course changes for aircraft on final

[Byrna]

Hello,

I wanted to know what kind of limitations are placed by flight regulations on how much of a turn (in degrees) a commercial jet can be asked to do by ATC on its final approach to an airport. By commercial jet, I'm talking anything 737/A320 class or larger.

In other words, what are the rules, if any, for course changes for a commercial jet which is, say 30NM, 20NM and 10NM from touchdown? The reason I'm asking is to see how realistic the ATC is in Microsoft's Flight Simulator 2004 which I use. I don't use the ATC anymore for IFR flights for I find it asks me to make odd course changes. But since I'm not a real-life pilot, it's hard to know if this is realistic or not.

Example: is it normal for ATC to ask an airplane 10NM from touchdown to make any major turn (e.g. a turn of, say 30 degrees or more)? or is it more likely that at that distance, the plane is basically set on its final runway heading and concentrates on keeping that heading until touchdown?

Thanks for any input.


John

[reynoldsno1]

Talking generally - depends on the type of approach being flown - ILS/MLS approaches (called precision approaches) are normally aligned with the runway, but can be offset up to 5 deg. Non-precision approaches (VOR/NDB) can be offset by up to 15 deg for Cat C/D aircraft (B737 and larger). An aircraft established on a published IFR approach procedure should not be asked to alter heading by ATC, unless there is a safety of flight issue.

[Irish Steve]

is it normal for ATC to ask an airplane 10NM from touchdown to make any major turn (e.g. a turn of, say 30 degrees or more)?

Very regular, for all sizes of aircraft up to and including 747's.

It will be most often that the closing course to a localiser will be "offset" by up to 30 degrees, and the aircraft will be expected to establish on final approach course when intercepting. That can occur as late as 4 miles, though that is expecting more of the crew. At 10 miles, you could easlily get up to 90 degrees of change, depending on the approach routing. If you were flying a procedure approach, then there could be a complete reversal of almost 180 degrees at somewhere around 8 to 12 miles, occasionally closer to the airport. That's not a problem to do in commercial aircraft.

A "standard" hold before approach due to congestions is a 4 minute "racetrack" around a fixed beacon point. 1 minute on heading, reversal of 180 degrees over a minute, 1 minute on reciprocal, 1 minute change back again through 180.

If you're having problems with this, what speed are you trying to do it at?

Most approach speed work will be done at less than 250 Kts, and close in, more like 200-210 Kts, depending on type, smaller aircraft, it can be considerably slower.

Hope that helps