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-   -   Iran Accident (https://www.pprune.org/rumours-news/605571-iran-accident.html)

old,not bold 22nd Feb 2018 11:43


Exactly so; the NDB is the bit on the ground and the ADF is the bit in the aircraft.
2 parts of the same system; the ADF will point to the NDB. And that's it, at least for us KISS adherents.

As I understand the remark about a "back-bearing", an ADF will not show exactly that. What the pilot must do is subtract 180 (using a calculator if necessary) and fly the reciprocal, not forgetting to adjust for drift, so that the bearing to the NDB remains constant as he flies away from it. Or something like that. It's been a long time...... as I recall it, some mental agility is needed when you are doing this in IMC as part of an NDB approach/cloudbreak, what with everything else to think about.

wiggy 22nd Feb 2018 11:51

Not that we do this (much) anymore but I'm a bit confused about reference to calculators and the like. Has the old RMI skill of "pulling the tail" to fly outbound from a VOR/NDB on a fixed radial simply died a death?

The Fat Controller 22nd Feb 2018 11:59

NDBs don't have radials !

Flying a TRACK away from an NDB is not an easy task, especially when there is a serious crosswind.

aterpster 22nd Feb 2018 13:46


Originally Posted by Machinbird (Post 10061054)
Everyone is discussing the interesting approach, but it is not clear to me that the aircraft even reached the Yasouj NDB to commence the approach.

Those are some serious Mountains north of Yasouj, and tall mountains, strong winds can create extreme problems in maintaining altitude.

So far, information on the route of the flight has been pretty sketchy. :confused:

So far there are two possibilities based on that sketchy info:

1. the flight got off course along the airway and began descent prematurely (for whatever reason), or

2. The approach had been flown and a missed approach was in progress, albeit off course.

The recorders hold the answer because there surely is no ATC radar once in that valley or canyon.

ironbutt57 22nd Feb 2018 14:04

Flying a TRACK away from an NDB is not an easy task, especially when there is a serious crosswind.

"pull the tail"

wiggy 22nd Feb 2018 14:07


NDBs don't have radials !

Flying a TRACK away from an NDB is not an easy task, especially when there is a serious crosswind.
OK, OK, my bad, excuse the nomenclature, but I suspect/I hope you understood what method I was driving at with that post....there is a basic RMI technique that covers both VOR radial and NDB outbound course tracking and there's no real need to deploy calculators and do loads of pre-flight planning to do so.

Take a procedure which has an outbound track from an NDB..you can achieve and hold the required TRACK from your NDB by "flying the tail" or "dragging/pulling the tail" of the ADF needle so that the tail lies against the RMI compass rose on the outbound track demanded by the procedure (FWIW for any errors I was taught to use double that error as the steering correction) . Yes I know you need to take drift into account, but TBH having done this stuff in the past for NDB, VOR and TACAN procedures, and well before the days of GPS and overlays I personally wouldn't say following a track or radial outbound from a beacon was in the rocket science level of difficulty, it is (or at least it used to be) standard procedural IF "pilot stuff". I'd also agree it can be demanding on a bad weather day and very unforgiving of gross errors if there are terrain issues..


Call me old fashioned but I do agree to a certain extent with Arctic Circle's comment.

twochai 22nd Feb 2018 14:19


So far there are two possibilities based on that sketchy info:

1. the flight got off course along the airway and began descent prematurely (for whatever reason), or

2. The approach had been flown and a missed approach was in progress, albeit off course.
There is a third possibility: LOC - Loss of Control in severe icing.

Plumb Bob 22nd Feb 2018 15:01

Well, yes, and not a particularly super combination of aircraft type and environment.
Of course that has been addressed in the past, but, [speculation mode] think of car tires that become brittle with the passing of time if not flexed (massaged) and remaining stationary for years on end – how well can deicing boots withstand deterioration by the weather during a very long period unprotected without any use? That combination of external influences just could be a new factor here. [speculation mode off]

aterpster 22nd Feb 2018 16:00


Originally Posted by twochai (Post 10061585)
There is a third possibility: LOC - Loss of Control in severe icing.

That's why I included "for whatever reason" in my option #1. Severe icing and being quite off-course are usually independent events.

Timmy Tomkins 22nd Feb 2018 17:38

My post #31 asked this question; does anyone know the extent of radar cover in the area?


Was there radar cover in the area or where they expected to let down using own nav? That could explain the end result if the aircraft only had basic kit.

Teddy Robinson 22nd Feb 2018 20:53

with all due respect, radar cover in an area with those MSA's is an oxymoron

Airbubba 22nd Feb 2018 21:28

A report that the Aseman ATR 72 fleet has been grounded:


Iran Civil Aviation Organization (CAO.IRI) has ordered Iran Aseman Airlines to ground its ATR 72 fleet until further notice, following the crash on February 18.

RatherBeFlying 22nd Feb 2018 23:28

The investigators, once they have the FDR data, will likely want to repeat the approach and miss in VMC with one of the grounded airframes with a similar ADF installation to see where the 310 back bearing takes them.

Even better would be in similar winds aloft. The FDR data should be sufficient to derive this.

aterpster 23rd Feb 2018 13:36

You're assuming they made the approach. We don't know that.

AAKEE 23rd Feb 2018 14:49

Timings/reported distance and probable time for crash and position assumes it wasnt possible to make it to the IAF and back to position for crash.

RatherBeFlying 23rd Feb 2018 16:39

Did they make the approach?
 
The crash position seems to have some imprecise alignment with the missed approach segment which has raised my suspicions on the quality of the missed approach course guidance.

If they had not begun the approach, there's a whole bunch of other questions. I look forward to further information.

twochai 24th Feb 2018 01:03

Iran suspends operations with ATR 72-200 and -500
 
https://news.aviation-safety.net/201...atal-accident/

Timmy Tomkins 24th Feb 2018 08:59


Originally Posted by Teddy Robinson (Post 10062045)
with all due respect, radar cover in an area with those MSA's is an oxymoron

That's a rather patronising response to a sensible question. Old a/c, probably no GPS, and as others have said, we don't know that they were on or missing an approach.

They could have needed urgent decent (fleet grounded now so, icing/other failure?) and radar confirmation of position would have been very useful.

The terrain varies in height and MSA is based on the highest in the sector so being steered around the worst if descent unavoidable would have been invaluable - I speak from personal experience; so Oxymoron No definitely not

mcdhu 24th Feb 2018 09:11

Also potentially relevant are altimeter temperature and wind error which, if not applied correctly could eat up a large proportion of the increment added to the highest ground.

Extreme cold and high winds, which were both reported, can have a a significant effect.

We wait to see

Double Back 24th Feb 2018 09:58

ADF and a fixed card was a great tool for training ab initio pilots, it sure weeded out those who could not multi-task and paint a picture in their brains of the position relative to the ADF bcn or RWY. I did my share during training with intercepts from all kind of directions, entering holding patterns.. Using the RMI made life a lot better.

In actual airline flying, in 30 Years of airline flying, almost all of it on heavy jets, I might have flown 3 actual NDB approaches in not so good WX.
During the 17 Years as capt I started my non-precision crew briefing stating we had an emergency coming up :) That got everybody's attention.
Flying any non precision in a heavy jet is outright dangerous, enough terrible accidents have proven that. Just one wrong frequency and You got completely lost.


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