I'm not obsessed at all. It is a VFR arrival departure procedure from helipad to helipad Sadly, not updated for the modern age other than changing the WP names and designed for non-nvd night letdowns where a big flashing light on a rock would be a good way of confirming your position. |
Blackrock Sling vs Mayo. 80feet vs 300?
Remote contributing factor?
Could the crew have confused the height of Slingo Blacrock Lighthouse ( 80feet) and Mayo by asosiation. Not likely, but you never know. |
Originally Posted by XA290
(Post 9742103)
Coastal radar navigation from the last millennium
25 Years ago, GPS was in its infancy as far as helicopters were concerned. Indeed, DECCA was still the primary navigation tool employed by helicopters involved in Oil and Gas and SAR both in the U.K. and Ireland. DECCA had moved on from the MK 19 roller map to the RNav1 and later the RNav2 computers but they were point-to-point navigation systems. There were no moving maps in helicopters in the 1990s. There was also no electronic nav kit in the back of civilian SAR S61s. Coastal Navigation and let-down procedures for SAR using a point-to-point RNav2 computer was fraught with danger. Particularly when using DECCA as it was prone to atmospheric interference on that dark and stormy night when you would be quite possibly using it in anger. For this reason, your position had to be confirmed against a separate source and this was the radar. Putting a waypoint on a piece of rock or a headland confirmed your position. If the waypoint appeared under an appropriate shaped radar return that cross referenced with the paper map you were holding you were where the DECCA RNav thought you were and let-down could proceed safely. Back in 1995 the SAR contract was operated by Irish Helicopters and they had a waypoint on Black Rock as an IP for a let-down to Black Sod. It was called something different then to the one CHC use now but it was on the rock for the reasons I give above. It was to confirm your position in an S61 using a generally good but possibly unreliable DECCA nav system and a good distance out from Black Sod to allow height loss after over flying the rock. It seems that a legacy from a past generation using past generation kit was left in use and the seeds of this tragedy were sown in the early 1990s. I hope this may shed some light on how this came about from a historical perspective and why there was a waypoint on Black Rock and not mid channel. |
Blackrock Island
1 Attachment(s)
Cobbled this together from the Report
Attachment 2093 |
Originally Posted by gulliBell
(Post 9742123)
I think what you are saying is they are one and the same.
Just as said by ukv1145 : "To be slightly pedantic, ALL aural alerts on the S92 except 'AIRSPEED, AIRSPEED' come from the EGPWS box (note: not triggered by - the recordings reside within the EGPWS processor and can be triggered externally as well as internally) So if you lose the EGPWS you lose all system aural warnings." |
Originally Posted by P3 Bellows
(Post 9742175)
..Was it a generic EGPWS manual or the S92A flight manual that you grabbed? .
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The Irish AAIU prelim report is well written. The section on EGPWS is revealing for what it doesn't say. Honeywell seem at pains to point out the database is supplied by someone else, but on their website claim it is proprietary to themselves. The AAIU obviously isn't happy and says it it still trying to fully understand this issue. More to come I think.
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Originally Posted by dervish
(Post 9742250)
..Honeywell seem at pains to point out the database is supplied by someone else, but on their website claim it is proprietary to themselves.
"The terrain database is the heart of the EGPWS. The database includes information regarding terrain, airports and obstacles such as towers, buildings and antennas, that are 100 ft or taller. It is important to know that wires are not a part of the database at this time. The system compares aircraft position and motion against the terrain and obstacle database to provide its cautions and warnings. EPWS also provides non-database related warnings. It does so using a term known as geometric altitude, which is derived from radar altitude, a GPS altitude, barometric pressure and aircraft motion calculations" |
I would offer a bait - STABILISED APPROACH to MDA/H & MAPT
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What does the Manual say about User supplied data for inclusion in Updates?
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Database approval
This EASA info gives the two scenarios for data base approval.
"There are two types of Letters of Acceptance Type 1 LOA Letter of acceptance granted where a Navigation Database supplier complies with EUROCAE ED-76 / RTCA DO-200A documents with no identified compatibility with an aircraft system. A Type 1 LOA confirms that the processes for producing navigation data comply with these Conditions and the documented Data Quality Requirements. A Type 1 LOA may not release navigation databases directly to end users. Type 2 LOA Letter of acceptance granted where a Navigation Database supplier complies with EUROCAE ED-76 / RTCA DO-200A documents and provides data compatible with specified avionics system(s). A Type 2 LOA confirms that the processes for producing navigation data comply with these Conditions and the documented Data Quality Requirements for the avionics systems specified. The Data Quality Requirements must be provided by or agreed with the specified equipment design organisation in accordance with a formal arrangement. A Type 2 LOA may release navigation databases directly to end users. Such releases may also include data packing tools, where the use of such tools has been demonstrated to be ED-76/DO-200A compliant. A Type 2 LOA holder may interface directly with data originators (such as State AIP providers and operators), or may use data supplied by a Type 1 LOA in which case interfaces with data originators may not be necessary." https://www.easa.europa.eu/navigation-database-suppliers-letters-acceptance |
Originally Posted by SASless
(Post 9742267)
What does the Manual say about User supplied data for inclusion in Updates?
But I do recall contacting the terrain and obstacle database provider (about 5 years ago), and asked how to get the data for the area I was operating in updated because it was woefully inadequate. As I recall, the process had to be directed via the local CAA, and it quickly became apparent to me that nothing was going to happen any time soon. So I didn't bother pursuing it. |
So....we know Blackrock was not correctly represented in the current database....and there is no effective procedure to correct known deficiencies?
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Originally Posted by SASless
(Post 9742285)
So....we know Blackrock was not correctly represented in the current database....and there is no effective procedure to correct known deficiencies?
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Originally Posted by gulliBell
(Post 9742142)
I just grabbed the EGPWS manual from our technical library...it helps when trying to understand something like this to have the book to refer to. Here is what it says:
Mode 6 provides audio call-outs for descent below predefined altitudes and minimums. Mode 4B : When the landing gear is lowered, Mode 4B becomes active and the boundary decreases to 100ft when above 120 kts. As airspeed decreases below 120 kts the warning boundary decreases to 10 ft at 80 kts. The landing gear was down at the time of the accident. |
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. |
Originally Posted by agirl
(Post 9742297)
..The landing gear was down at the time of the accident.
The report says low altitude switch was engaged. This is what the manual says about that: "A LOW ALT switch allows for helicopter operations that require low altitude flight. Use this function for flight at low altitude in VFR conditions. Engaging this function: ƒƒ Inhibits Mode 1 ƒƒ Significantly reduces Mode 2 warning boundaries ƒƒ Significantly reduces Mode 4 warning boundaries ƒƒ Enables Mode 6 “Altitude-Altitude” call-out ƒƒ Reduces Terrain Advisory look ahead distance Low Altitude operation is defined as operation below 500 ft AGL, in a high-density metropolitan environment with high-rise buildings, below 1,250 ft AGL when the GPS is not operational or is providing poor accuracy, or airport maneuvering where airspeeds exceed 50 Kts" |
Could someone kindly tell me what the MSA is in the area of the approach they used.
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Since the aircraft had suffered 10 seconds of substantial impacts and considerable damage at the time of that call, our minds should be open to the idea that automated calls in that period do not reflect the true status before impact.
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Originally Posted by gulliBell
(Post 9742383)
In mode 4B, if the landing gear was down at the time of the accident, below 120kts, the aural warning at time stamp 2.03.09.026 on the CVR should have been "TOO LOW TERRAIN". The aural warning actually recorded at that time was 'TOO LOW GEAR", which means the gear was up. If the gear was up then the system couldn't have been in mode 4B. That's my understanding of reading the manual.
The report says low altitude switch was engaged. This is what the manual says about that: "A LOW ALT switch allows for helicopter operations that require low altitude flight. Use this function for flight at low altitude in VFR conditions. Engaging this function: ƒƒ Inhibits Mode 1 ƒƒ Significantly reduces Mode 2 warning boundaries ƒƒ Significantly reduces Mode 4 warning boundaries ƒƒ Enables Mode 6 “Altitude-Altitude” call-out ƒƒ Reduces Terrain Advisory look ahead distance Low Altitude operation is defined as operation below 500 ft AGL, in a high-density metropolitan environment with high-rise buildings, below 1,250 ft AGL when the GPS is not operational or is providing poor accuracy, or airport maneuvering where airspeeds exceed 50 Kts" |
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