View Full Version : Why do my big jets turn sharply away from runway during ILS approaches?

01-02-2002, 07:23 PM
I am confused , when I do an ILS approach in the Cessna's or other small aircraft, I have no problem, but in the 737 and 777, all seems to go well going into the approach, but the jet does not descend from about 2000ft on the glideslope with 'AP' engaged and all of a sudden about 2 mile from the runway will pull sharply left out of the approach changing course???

Am I missing something, I have just recently figured out how to successfully land the 'HEAVY'S' but this is just blowing my mind.



01-02-2002, 07:32 PM
Did you activate the APR light on your autopilot and switch to VOR on the GPS-VOR toggle switch?

01-02-2002, 07:35 PM
The APR light on the AP yes, but when you say the 'VOR' switch, you mean the GPS/NAV switch to 'NAV' mode? not sure if I did switch it over, I know in the 737 I had it on GPS mode, is that a problem?


01-02-2002, 07:39 PM
Yes it is a problem because ILS is a feature of Nav 1, (and 2 in some very high-tech aircraft). You are locked onto the airport as if it is a VOR with out a glide slope, and you also enter the "cone of confusion" where the needle goes wild becasue even a small correction to corse takes dramatic effect at that distance to the airport. Try switching it to NAV.



01-02-2002, 07:40 PM
Thanks buddy.

01-02-2002, 07:48 PM
When I first started flying the "Heavys" I had the same experience. I was sooo confused why my aircraft flew off course and smashed into the ground. When I discovered the NAV_GPS toggle, was set to GPS, I saw my problem...