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-   -   ILS/DME Approach (https://www.pprune.org/tech-log/375667-ils-dme-approach.html)

411A 11th June 2009 07:59


Does that mean TSO129c at the minimum?

Yup, and installed and approved for IFR terminal/approach procedures.

JAR 11th June 2009 09:31

From an ILS/DME Jeppesen app chart
 
1ILS:
Acft unable to receive DME
advise ATC. Radar ranges will
be provided at 7 NM outbound
and 4 NM inbound.

411A 11th June 2009 15:02

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.

BOAC 11th June 2009 15:20

Bring back the marker beacon (and the NDB - as long as I don't have to fly an approach on it...................................)

Graybeard 11th June 2009 16:48

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

eckhard 11th June 2009 19:23

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?

Tinstaafl 11th June 2009 20:26

'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!>'.

Graybeard 11th June 2009 20:38

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

BOAC 11th June 2009 20:41

Always worked on GS intercept point. If below published 'platform', you work out a new one. DME ranges v Heights are not always published on charts.

BOAC 12th June 2009 13:03

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:}


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