ILS/DME Approach
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
All very interesting, IGh, however, one is not going to be assured about inaccurate glidepath signals without fault monitoring in the aircraft and on the ground.
DME readouts on approach, while assisting to some extent, are not, IMO, the ultimate solution.
Likewise for the localizer signal.
A better solution was the MLS, but that seems to have slipped into oblivion.
DME readouts on approach, while assisting to some extent, are not, IMO, the ultimate solution.
Likewise for the localizer signal.
A better solution was the MLS, but that seems to have slipped into oblivion.
Joined: Nov 2006
Posts: 896
Likes: 2
From: SoCalif
Igh: "Alitalia DC-9 / 14Nov90 DC-9-32 I-ATJA , ILS- CFIT; … flew about 900' too low on approach to Zurich … into a hill about 9.6 km from the city's airport at night. Fatal=40 passengers + six crew. … false Glide Slope indication with no Flag … "
That accident was a combination of Alitalia's complex ILS cockpit configuration, which left just one ILS receiver usable on that approach, and a KNR-6030 VOR/ILS receiver that had a history of intermittent false indications with no monitor channel to catch errors.
A DC-8 cargo captured a false localizer beam at Cold Harbor in Alaska in the mid-1970s, and hit a mountain in the dark.
GB
That accident was a combination of Alitalia's complex ILS cockpit configuration, which left just one ILS receiver usable on that approach, and a KNR-6030 VOR/ILS receiver that had a history of intermittent false indications with no monitor channel to catch errors.
A DC-8 cargo captured a false localizer beam at Cold Harbor in Alaska in the mid-1970s, and hit a mountain in the dark.
GB
Joined: May 2005
Posts: 1,198
Likes: 32
From: France
One important lesson I picked up from the ANZ incident is that it is important to check DME against altitude (not the other way round).
In other words you should say,
"We're now passing 1800ft, what should the DME be reading?"; instead of,
"We're now at 6DME, what should the altimeter be reading?"
The reason is that if you are inadvertently low, it may be dangerous to wait until a certain DME check point before verifying the altimeter reading.
For example: "We're now at 6DME, the altimeter should indicate 1800ft. Hey! It indicates only 1500ft! Why is that?.. -- >::Sound of impact::<
Far better to say, "We're now at 1800ft, the DME should indicate 6DME. Hey! It indicates 7DME! We must be too low! ::Sound of engine power increasing::
What does your company teach?
In other words you should say,
"We're now passing 1800ft, what should the DME be reading?"; instead of,
"We're now at 6DME, what should the altimeter be reading?"
The reason is that if you are inadvertently low, it may be dangerous to wait until a certain DME check point before verifying the altimeter reading.
For example: "We're now at 6DME, the altimeter should indicate 1800ft. Hey! It indicates only 1500ft! Why is that?.. -- >::Sound of impact::<
Far better to say, "We're now at 1800ft, the DME should indicate 6DME. Hey! It indicates 7DME! We must be too low! ::Sound of engine power increasing::
What does your company teach?
Joined: Dec 1998
Posts: 4,282
Likes: 6
From: Escapee from Ultima Thule
'DME' to Altitude or 'Altitude to DME' I think is much of a muchness, although I'm willing to be convinced otherwise. In the scenario given above for the favoured technique the final event could equally have been <crunch!> instead 'Sounds of engine power increasing' (or even a 'Sounds of engine power increasing...<crunch!>'.
Joined: Nov 2006
Posts: 896
Likes: 2
From: SoCalif
Further to my post above, IIRC, they had tuned the number 2 VOR/ILS receiver to VOR on field, to get DME distance, and had followed a dead GS needle. GPWS gave no warning, of course, since it was receiving the same 0 GS deviation.
GB
GB
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
IGh - yes. Subject to any range/altitude minima and descent rates, once ESTABLISHED on the localiser, it would be ok. Of course, assuming eventual G/S capture
. Good job too, or I might have 'missed' a few times in AMS
. Good job too, or I might have 'missed' a few times in AMS
