Potential ILS gotcha

[Jonzarno]

I came across this video on the COPA forum, well worth watching!

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[Pace]

Jonzarno

Hence why its important to trust nothing and confirm all.
Always check spot points on the charts to confirm that the altitude you should be at corresponds with the altitude you are at on the glideslope or not on the glideslope as the case maybe

Pace

[007helicopter]

One point Reminded me I have become sloppy and NOT identing ILS's frequency's that I am familiar with. Slap on the wrist and will correct this.

[Shaggy Sheep Driver]

A good lesson in CRM. Of the 6 holes in the cheese that had to line up to lead to an accident, only the last, hole no.6, was prevented from aligning by an on-the-ball crew.

They had very little time to decide to distrust what is normally the most trustworthy approach aid in non-visual conditions - an apparently correctly indicating ILS display.

Well done them!

[Jetblu]

Interesting. I think we have all been guilty at some stage of not fully identifying ident ILS frequency at airfields we are accustomed to.

It would also be interesting to know how many times this particular crew had been into that particular field. I suspect a sixth sense creeping in before the fifth hole of the cheese lined up, working on the assumption that the crew had been in before.

[Shaggy Sheep Driver]

They didn't fail to check the frequency - the frequency and indeed the morse ident were fine. What was missing was part of the glideslope signal and they had no way of knowing that.

If you think checking the frequency will prevent what nearly happened to this crew, watch the video again.

[Jetblu]

Shaggy. I did not mention the wrong frequency being selected. If you think I said that, check again. I said " not fully identifying IDENT on frequency.
I was particularly concurring with 007 Helicopter.

I am well aware what happened, how it happened and why. :ok:

[India Four Two]

Jetblu,

Checking the ident wouldn't have helped either. That was being transmitted on the LOC signal.

As SSD said, the crew had no way of knowing that the GS was unserviceable. The GS transmitter was left in a test mode which meant that only one part of the GS signal was being transmitted, which meant that an ON GLIDESLOPE would always be received by an aircraft, regardless of its location! :eek:

A further hole in the swiss cheese, was that due to construction, the tower was not able to monitor the ILS integrity.

So the moral here is to treat an ILS as unserviceable if it is NOTAMed NOT MONITORED.

From a design point of view, I am staggered that the equipment continues to transmit an ident, if the GS is not in normal operational mode.

Kudos to Air New Zealand for producing this video. I can't imagine corporate lawyers allowing that these days.

[Pace]

Yes but second time round they treated the approach as a localiser only approach and this is my point if you treat the glideslope almost like a localiser approach i.e. check various altitude points against the charts then you can confirm that the two match up.

Pace

[john_tullamarine]

Kudos to Air New Zealand for producing this video.

I was working for ANZ at the time and, while not involved at all with the investigation, I had discussions with one of the investigators whom I knew from a training course some years prior.

I was quite impressed by the mature and sensible attitude adopted in the investigation ..

I suspect that the event was a wake up call for anyone who took the time to read up on the incident. Reinforces the old adage that one should take in all the cues and information available to avoid stuff ups in flight.

[ChickenHouse]

If their crew management training is as good as their spelling skills ... never heard of Jepperson charts ...

[Pace]

Just to make another point a correct ident does not in all cases mean the ILS is reliable.

We always make it standard practice to usually confirm the Glideslope intercept DME point if available against the altimeter so for instance if you are at a platform of 2500 feet and the glideslope intercept is at (just using a round figure) 6 DME on a chart! Then its easy to check one against the other. You then know your altimeter is set at the right figure and that the glide is correct.
Make a further check at around 1500 feet or nearest again against a chart depicted point and you know you are on the right glide. Don't just blindly fly a glide without backing it up an this appears to be the case with this crew until late in the descent so not really such good airmanship by the crew!

Pace

[Big Pistons Forever]

Another scenario is an instrument failure. This happened to me once when I was teaching IFR

The scenario:

ILS no DME with a NDB at the FAF. DH 400 feet, FAF ctossing alt ( gp check)
1400. We were on vectors at 2500 feet and told cleared for the approach, not below 2000 until loc intercept and to expect to join at or slightly above the glide slope.

I knew we were in close so I told the student he had better expedite to 2000, but he was slow to react and we were at around 2200 when we intercepted the localizer with the glide slope almost full down. He then started an aggressive descent. Very quickly we were approaching 1400 with no sign of beacon passage. I then took control and levelled at 1400. The glide slope needle remained full down even when we passed the FAF so I imediately started climbing and followed the missed approach procedure.

On return to our base the system was tested and an internal failure of the instrument was confirmed. At no time did the instrument display a flag.

This scenario developed very rapidly and the student realized when I took over we were maybe one minute from flying into the ground due to the high descent rate he had established. He said all he was thinking of was chasing the gs needle. The glide path check point can literally be your last chance to save your life.

The final lesson was if you experience an abnormality during the approach, do not try to troubleshoot it, go around.

Ignore the bollocks taught in flight schools about switching to a non precision approach if the gs fails :ugh:

[FullWings]

if you treat the glideslope almost like a localiser approach i.e. check various altitude points against the charts then you can confirm that the two match up.
If there was anything to take away from the video, it was that. Checking at the FAF at platform altitude with a fault as described will not reveal anything. Even at the marker, you might be unlucky and be at the correct altitude but on a steeper glideslope that will intersect the terrain short of the runway.

An RNAV-to-ILS approach is just as vulnerable as it would all check out until after you’d been coupled to the glideslope for a while. The RoD, power and pitch could be close enough to normal not to stand out, especially with changing wind or turbulence.

[AerocatS2A]

There is one Australian port I fly into that has a habit of NOTAMing the ILS as off for works at night but when you go in there you find no mention of it on the ATIS and if you tune and ident it you find that it appears to be working. I always make a point of confirming with approach what the actual status is if there is any ambiguity and I also make a point of letting the guys I fly with know about the Air NZ incident. Just because it has a valid ident and no flags does not mean it is a working ILS.

The other lesson I take from it is to conduct your glide slope checks at an altitude, not a distance. So if the marker check height is at 1300' then when you get to 1300' check your distance or check that the marker is sounding as expected. If you wait for the marker to sound and then check altitude you might find you've already lost terrain clearance if you were in a premature descent like those guys were. Ideally do a few glide slope checks, it's not like there's much else to do on an ILS once checklists etc are taken care of.

Edit: sometimes approach says they're just about to turn it off, other times they say it's been decided to leave it on for the night. Assume nothing.