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SAR S-92 Missing Ireland

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SAR S-92 Missing Ireland

Old 16th Apr 2017, 16:54
  #1081 (permalink)  
 
Join Date: May 2002
Location: Wanaka, NZ
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Originally Posted by [email protected] View Post
So, one question is - even if Blackrock had been in the database, would the EGPWS have alerted with the gear down at a speed of less than 80kts?.
From the manual:

"When the landing gear lowers, Mode 4B becomes active and the boundary decreases to 100 ft when
above 120 Kts (100 Kts on fixed gear aircraft). As airspeed decreases below 120 Kts, the warning boundary
decreases to 10 ft at 80 Kts. The voice message is “TOO LOW TERRAIN”."


I don't know how the boundary changes given the LOW ALT mode was engaged, I can't see anything on that other than "significantly reduces mode 4 boundaries".

Last edited by gulliBell; 16th Apr 2017 at 17:10.
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Old 16th Apr 2017, 16:56
  #1082 (permalink)  
 
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Originally Posted by MagentaL View Post
The gear was extended during the descent and 3 greens confirmed locked down.
OK, that is definitive then.
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Old 16th Apr 2017, 17:01
  #1083 (permalink)  
 
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Gear down

Re gear down see section 5.5 last bullet point, AAIU report,
Gear was down and three green lights
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Old 16th Apr 2017, 17:28
  #1084 (permalink)  
 
Join Date: Apr 2017
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Hi. My apologies, I am just an interested civilian so I'll be brief.
IAA ICAO charts use a red circle as the symbol for a lighthouse.The "Approach Blacksod South" route guide being used had two of these red circles. One at BLKMO marked 282. One at BLKSD marked 43. According to Irish Lights those heights given are the heights of the lights on the lighthouses in those two locations.
So the map provided seems to provide the information that BLKMO is a lighthouse at 282 feet ASL.
I think it was unfortunate that the hazard warnings were also in red circles, albeit slightly larger, and even more so that BLKMO was #1. That left open the possibility of misinterpretation that it was a starting point, not an indicator to refer to the written text.
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Old 16th Apr 2017, 17:41
  #1085 (permalink)  
 
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Originally Posted by gulliBell View Post
OK, that is definitive then.
Also from the report:
footnote on page 13, but more importantly section 6.3 "Wreckage found on the sea bed" on page 27
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Old 16th Apr 2017, 17:44
  #1086 (permalink)  
 
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Originally Posted by gulliBell View Post
I don't know how the boundary changes given the LOW ALT mode was engaged, I can't see anything on that other than "significantly reduces mode 4 boundaries".
With LOW ALT, all TERRAIN warnings are inhibited, you get only GEAR warnings below 60kts, and the upper height boundary is reduced from 150ft to 100ft (for mode 4A - it's already 100ft for 4B).

Last edited by GKaplan; 16th Apr 2017 at 21:57.
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Old 16th Apr 2017, 17:49
  #1087 (permalink)  
 
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I think there is some confusion here. Mode 4 and all its sub modes are vertical modes only, based on rad alt, not look forward based on the database.
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Old 16th Apr 2017, 17:57
  #1088 (permalink)  
 
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Originally Posted by ukv1145 View Post
I think there is some confusion here. Mode 4 and all its sub modes are vertical modes only, based on rad alt, not look forward based on the database.
Agree.
All modes 1 to 6 are 'non-database' modes, all of which use the RADALT height as their primary input.
They are all defined automatically by the a/c configuration and require no pilot input.

The look ahead mode (using the database) is not numbered, hence the confusion I guess
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Old 16th Apr 2017, 18:32
  #1089 (permalink)  
 
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Originally Posted by [email protected] View Post
So, one question is - even if Blackrock had been in the database, would the EGPWS have alerted with the gear down at a speed of less than 80kts?

The interim report seems to indicate the look forward boundary is only 10' at 80 kts and only 100' at 120 kts with the gear down. At 120 kts the aircraft is travelling at more than 180 ft/sec and even at 75 kts it is doing over 110 ft/sec.
Are these boundaries reasonable for a helicopter at low level?

Perhaps the SOP for putting the gear down so early needs to be revisited.
If it had been in the database the short answer is yes.

"The system uses measured and predicted flight path data together with database information to look ahead for threats. The look-ahead area is based on ground track and flight path angle, corrected for any turns. It uses a 6 climb out angle so it is assuming a rate of climb to clear the obstacle or terrain of ten times the groundspeed (for example, 1000 feet/min at 100 knots groundspeed).
The system should give at least 30 seconds warning of any threat (that is, just over one mile at 120 knots).
Detection of a threat will generate a yellow threat caution area on the display, accompanied by a yellow TERRAIN or OBSTACLE caption on the ADI and a "Caution, terrain" (or "Caution, obstacle") aural warning. This aural warning is repeated twice, continuously at 7-second intervals, if the threat persists.
If the aircraft closes to within 20 seconds of potential collision, the display threat area and ADI captions change to red and the aural warning changes to a continuous "Warning, terrain" or "Warning, obstacle"."


---

What can be discussed I guess is the Mode 2 "excessive terrain closure rate" (just to repeat, a 'non-database' mode )

"This mode is designed to warn of excessive closure rates to terrain, primarily in the cruise. It uses RADALT height and rate to determine closure rate, but it also takes account of landing gear position, ILS information and airspeed. There are two submodes, 2A for the cruise and 2B for approach and landing.
Both submodes are inhibited if terrain data is of high integrity, in LOW ALT and in autorotation.
Otherwise, the modes are active below 300 feet AGL on takeoff and below 1200 feet AGL in the cruise

There are two boundaries, defined by RADALT height and closure rate. The inner boundary goes from 1600 feet/min at 30 feet to 1920 feet/min at 400 feet then up to 650 feet at 3120 feet/min. The upper ROD limit is 10000 feet/min. This boundary assumes a speed of 90 knots. As airspeed increases beyond 90 knots, the boundary expands from the 650 feet point to 1250 feet at 6000 feet/min, the upper height limit.
If the boundary is penetrated either horizontally or from above, an aural "Terrain, terrain" warning is generated together with the yellow TERRAIN caption on the ADI. If the flight path continues to penetrate the boundary, one second later a "Pull up" warning is generated together with the red PULL UP caption on the ADI. The warning will continue until the boundary is vacated.

Mode 2A is operational when the landing gear is up and height is above 30 feet.
Mode 2B provides a desensitised envelope for approach and landing. It is enabled with the landing gear down, if an ILS approach is in progress and the aircraft is within two dots of glide slope centre, and during the first 60 seconds after takeoff. The alert boundary is from 100 to 300 feet AGL; penetration of the boundary generates a single "Terrain" aural warning, repeated continuously, with associated TERRAIN caption on the ADI."


Just to be clear, when referring to vertical speeds the boundaries are defined by the RADALT rate of change (ie 'does the needle move fast?') rather than the actual aircraft vertical speed
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Old 16th Apr 2017, 19:23
  #1090 (permalink)  
 
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Originally Posted by Rivet View Post
Could someone kindly tell me what the MSA is in the area of the approach they used.
If you center the 25 miles on Blacksod, it seems the determining height is on Achill, so probably 3100 if the criteria is 1000 above. They came across at 4000.

If a real IFR approach were to be centered around Blackrock as an IAF, the design standard would be for a crossing height of 1400 feet with that designated as the initial approach phase. 500 feet for the next waypoint BKSDA.

Last edited by cncpc; 16th Apr 2017 at 19:43.
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Old 16th Apr 2017, 19:33
  #1091 (permalink)  
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Just for info, here's a map of all locations involved. The ship ws 30 km closer to Blackrock than Dublin.

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Old 16th Apr 2017, 19:47
  #1092 (permalink)  
 
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GKplan and others - I am basing my questions on the facts included in the interim report which many people seem not to have bothered to read before they post here.

If the IAAB have got their facts wrong then discuss the GPWS boundaries but I suspect it is unlikely that they have.

Rivet - I expect there is a permission in their AOC to operate IMC below MSA over water.
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Old 16th Apr 2017, 19:48
  #1093 (permalink)  
 
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A couple of Qs if I may,
The crew were employed by CHC on contract to the ICG is that correct?
If so were the crew trained on the S92 by the CHC training team that operate oil and gas on the N Sea or was their training bespoke to SAR and SAR in Ireland in particular?
We're their SOPs the same as oil and gas with additions/ dispensations for SAR?
Thanks in advance.
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Old 16th Apr 2017, 20:31
  #1094 (permalink)  
 
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Originally Posted by gulliBell View Post
OK, that is definitive then.
Have you actually read the report?

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Old 16th Apr 2017, 21:23
  #1095 (permalink)  
 
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Originally Posted by [email protected] View Post
Rivet - I expect there is a permission in their AOC to operate IMC below MSA over water.
It's in uncontrolled airspace, so yes, you have to have some means of making an approach.

So let's say they have such a permission, which I don't doubt, what happens when they come over land in the water?

I know what you are saying, but the method of achieving that safely seems dubious or uncertain.

In Canada, operators who work in uncontrolled airspace have to construct "company routes' and have a company route manual, or a part in their ops manual. A route has to incorporate terrain clearance standards that are published, and it has to be approved before the regulator. If I remember, I think a company can do that on its own.

A company can't design its own approach, or it can but it has to be approved by an approved approach design firm. Didn't used to be that way but it is now. And then the approach has to be published in the Restricted Canada Air Pilot. Long time, not overnight.

The alternative is a cloud breaking procedure, which I'm thinking is a descent to MSA.

Sort of what went on here, but perhaps lacking regulatory approval and a requirement to comply with some standard.
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Old 16th Apr 2017, 21:32
  #1096 (permalink)  
 
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Originally Posted by [email protected] View Post
GKplan and others - I am basing my questions on the facts included in the interim report which many people seem not to have bothered to read before they post here.

If the IAAB have got their facts wrong then discuss the GPWS boundaries but I suspect it is unlikely that they have.

Rivet - I expect there is a permission in their AOC to operate IMC below MSA over water.
Agree Crab that some appear not to have read the report. Just trying to clarify that the note 15 in the report refers to mode 4b which is entirely predicated on rad alt and is a height boundary not a forward boundary. This is a basic GPWS mode that does not look forward, only down. The only relevance of airspeed is as a switch to change the height at which a warning will sound and also the actual warning sounded.
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Old 16th Apr 2017, 21:35
  #1097 (permalink)  
 
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Originally Posted by [email protected] View Post
GKplan and others - I am basing my questions on the facts included in the interim report which many people seem not to have bothered to read before they post here.

If the IAAB have got their facts wrong then discuss the GPWS boundaries but I suspect it is unlikely that they have.
And I based my answers (copy and paste) on CHC Ireland's manual.
Should be fairly close...


Originally Posted by [email protected] View Post
So, one question is - even if Blackrock had been in the database, would the EGPWS have alerted with the gear down at a speed of less than 80kts?

The interim report seems to indicate the look forward boundary is only 10' at 80 kts and only 100' at 120 kts with the gear down. At 120 kts the aircraft is travelling at more than 180 ft/sec and even at 75 kts it is doing over 110 ft/sec.
Are these boundaries reasonable for a helicopter at low level?

Perhaps the SOP for putting the gear down so early needs to be revisited.
Actually in that case the AAIB isn't very clear, but I guess a footnote is not the most appropriate place to start copying a manual

This would have been a bit clearer: Mode 4B is active between 10 and 100 feet RADALT height with the gear down and speed above 80 knots. The upper boundary varies linearly from 10 feet at 80 knots to 100 feet at 120 knots or greater.

So (as ukv1145 rightly said), it is a height boundary not a forward one.

A confusion (as said before by others) exists in some minds between mode4 and 'look ahead'.

There is no relation between the look ahead (database) mode and the position of the gear. (and that answers your first question Crab. It is a yes, regardless of gear or speed. The remark about lowering the gear too early is not relevant).

Not selecting LOW ALT on the other hand might have given a mode 2 warning (not sure it would have been sufficient however, given the steepness of the island slope/cliff).

Last edited by GKaplan; 16th Apr 2017 at 22:03.
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Old 16th Apr 2017, 22:37
  #1098 (permalink)  
 
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GKaplan and ukv1145 - OK, I get the subtleties now with the modes and the LOW ALT selection - so we are saying that the mode 2 would have alerted if Blackrock had been in the database and the LOW ALT mode had not been selected?
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Old 17th Apr 2017, 00:00
  #1099 (permalink)  
 
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Originally Posted by [email protected] View Post
GKaplan and ukv1145 - OK, I get the subtleties now with the modes and the LOW ALT selection - so we are saying that the mode 2 would have alerted if Blackrock had been in the database and the LOW ALT mode had not been selected?
No, not quite. All of the numbered modes are legacy modes, designed before the eventuality of the terrain database and the enhanced 'look forward mode', so it would not have made any difference to mode 2 if Blackrock was in the database. Mode 2 MAY have triggered a warning if it had not been inhibited (boundaries reduced) by the Low Alt switch but this would depend on the nature of the terrain overflown, it will not give sufficient warning to very steeply rising terrain such as a cliff (which I imagine to be the case with Blackrock) as it is still only using the rad alt to look down and the warning will be given based on the rate of change of that rad alt signal.

Last edited by ukv1145; 17th Apr 2017 at 00:14.
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Old 17th Apr 2017, 00:03
  #1100 (permalink)  
 
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When operating offhore or at the coastline correct radar tuning is essential. Incorrect gain or tilt can make surface targets or islands invincible. Moving map and GWPS depend on correct data base and GPS position. A operational radar correctly tuned is the best insurance to confirm a flight path free of obstacles. Combination of Radar, FLIR, Moving Map, GPWS will give a good situation awareness. A SAR operator will normally describe a standard MFD set up for low level navigation.
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