Glideslope capture from above
Join Date: Dec 2001
Location: down-route
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Need to be very careful.
The false G/S is there lurking at 6° and 1.5°.
The false G/S is there lurking at 6° and 1.5°.
We fly Avro RJ100 into LCY where the glideslope is 5.5 degrees - most of our a/c being modified to carry-out steep approaches up to 6 degrees. The modification incorporates a 'STEEP APPROACH' button which when pressed (before the approach is commenced) de-sensitises the Mode 1 (Excessive Descent Rate) GPWS envelope. Despite the a/c being able to fly a steep approach we can still expect a "SINK RATE" followed by a "WHOOP WHOOP PULL UP" warning if the crew forget to press the steep approach button.
The GPWS will still protect your a/c from the excessive descent rate - should you fail to notice you're not on a 3 degree approach. If you're on a 6 degree glideslope (either false or approved steep approach) you have a hell of a battle slowing the a/c down (full airbrake is required on the BAe146/Avro RJ and final approach speed achieved before descending with the steep glideslope). The DME versus height/altitude/rad alt looks quite surreal and then there's the picture out of the window!
Do you "need to be very careful" about the false glideslope lurking at 6 degrees? The GPWS will protect you, but it will be embarrassing at the subsequent investigation following a very unstable approach(having missed all the signs) and then the inevitable "WHOOP WHOOP PULL UP" Go-Around.
