|
Originally Posted by Triskelle
(Post 9711969)
Looking at the LKP on the larger scale map of post #115, it appears to be on the N side of Blackrock. Also the pic in post #140 shows the helipad to be on the N side of the lighthouse - which would be consistent with the turn NW then turn ESE to approach the helipad. The weather reports from the nearest stations suggest that conditions around Blackrock would have been a cloud base around 200-300 ft with visibility reduced in RA/DZ and a SW'ly wind around 20kt. As a meteorologist, a stable SW'ly airstream of that strength passing over an obstacle such as Blackrock would have produced a severe downdraft on the N side of the rock (like a 'hydraulic jump' airflow) - in such situations I've known of 10 metre yachts to be flattened or even dis-masted. So if they were below the 300ft summit of the rock (perhaps with the intention of climbing to approach the helipad IFR in cloud) the downdraught conditions below the cloud base on the N side of Blackrock could well have been very difficult even for a S92.
The downdraft off the mountain is an interesting theory, I seem to remember from my (Many years ago) college weather classes, that the disturbance can be higher than the object itself as well. Even if they had the lack of visibility under control, dealing with that kind of sudden and local turbulence could easily add additional workload. That looks to be like a formidable island from the sea perspective, but you add a mystery about the air. |
Final groundspeed and Track?
1 Attachment(s)
Has the final speed approaching blackrock been clairified as 90kts?On marinetraffic
the final transmission from Rescue 116 gives a heading of 098 degrees and a groundspeed of only 9kts See attached image which also shows the exact final position in relation to Blackrock island. At Blacksod while approaching from the west one would need to letdown 50m before the lighthouse.Attempting the same at blackrock would quickly lead to danger as when heading on the same track one would encounter steep terrain before the lighthouse.If there were clouds as reported at 300ft this would be challenging.The AIS data does suggest controlled flight until the final position shown. Attachment 1938 |
Triskelle raises an interesting point.....just what magnitude of downdraft could be experienced at Blackrock with a 20 Knot Southwesterly Wind blowing?
How high above Blackrock could that down flow of air be encountered? If the Aircraft was on some sort of FMS SAR mode tracking inbound towards Blacksod.....could the aircraft have lost height as it was tracking overhead Blackrock and the crew not have time to counter the ROD produced by the down draft? Yes.....I know.....just "what iffing it" a bit in following up on his comment. I know from experience a 45 Knot Wind over an offshore platform can produce some really sporty turbulence on the down wind side......20 Knots seemed to be just some bumps and wiggles. |
20 kts rotoring over a descending helicopter at little or no airspeed would cause problems. However it would do very little to a large helicopter at cruise speed.
Oneperev, what you are describing is Mountain Waves. |
I wouldn't even be concerned about the machine possibly getting in the lee of a rock in a 20 kt wind. If that helicopter cannot handle those conditions, then they have one precious little puppy on their hands, that shouldn't be used in anything but clear blue days. Now i don't think is the case, but that is where this convo is heading.
And when the knives come out for me, actually yes i do fly, and have just recently come off a job operating fully loaded, in the lee of a 2000' hill, in 32 kt gusting 65, along with smoke mixed in, and we were required to do relatively precise drops on fires to save houses. There were a number of helicopters doing it, from 120's, 350, 355, BK and UH1's all on the fire, and they all handled it, and I'm sure that a 92 would be able to handle those conditions as well. |
Look at the shape of Blackrock and the fact it is isolated - the wind will blow around it with only a small amount of turbulence at the top - an approach even 15 degrees out of wind would avoid that turbulence and any downdraughting would be absolutely minimal.
|
I don't really agree with the downdraft theory. The island is only 400 metres long at its longest part and only max 82 metres high, so minimal scope for a downdraft. That final AIS fix, showing it on the westerly point of the island at 9 knots (but we don't know at what altitude), and where the search is happening 60 metres to the east of the island (so both points about 500 metres apart), with reports of debris on the island, don't suggest a downdraft issue. At that speed and with the distance between the two points so far it just doesn't add up for me. And it doesn't explain why they said they were on their final approach to BlackSOD, 10 NM to the east.
|
Originally Posted by minimaman
(Post 9712097)
Has the final speed approaching blackrock been clairified as 90kts?On marinetraffic
the final transmission from Rescue 116 gives a heading of 098 degrees and a groundspeed of only 9kts See attached image which also shows the exact final position in relation to Blackrock island. At Blacksod while approaching from the west one would need to letdown 50m before the lighthouse.Attempting the same at blackrock would quickly lead to danger as when heading on the same track one would encounter steep terrain before the lighthouse.If there were clouds as reported at 300ft this would be challenging.The AIS data does suggest controlled flight until the final position shown. Attachment 1938 |
Originally Posted by 212man
(Post 9712237)
I can't see your image on my phone, but the image I posted previously clearly shows 098 at 90 kts.
http://www.pprune.org/rotorheads/592162-sar-s-92-missing-ireland-6.html#post9708155 |
That last position would appear to be about that of the water entry so the heading and speed may well be correct - as to whether it was controlled entry or not we will find out later.
|
Originally Posted by [email protected]
(Post 9712331)
That last position would appear to be about that of the water entry so the heading and speed may well be correct - as to whether it was controlled entry or not we will find out later.
The commander of the LE Eithne Irish Naval vessel was on radio this morning. Tomorrow will give them a window for diving. Listen to him here |
OK, well that is even more confusing.
|
1 Attachment(s)
When you look at the last position with the projected path turned on, its almost in line with the helipad on the Open Street Map overlay. Which makes no sense... |
Originally Posted by Ber Nooly
(Post 9712251)
Yes, your image shows it at 90 knots but a little further west of the island than minimaman's one.
http://www.pprune.org/rotorheads/592162-sar-s-92-missing-ireland-6.html#post9708155 |
It still appears from the AIS data that the heli approached blackrock from the west tracking east with a track of 098 degrees as previously shown.It may have clipped the lighthouse outbuildings or something above the westerly cliff,at this point with severe loss of controlability from a compromised aircraft theoretically the heli could have ended up ditching anywhere around the islands perimeter?however the westerly side would have been the more obvious choice given the laws of physics.i guess all will be known when the fdr and cvr are retrieved the whole thing is very sad especially when these great pros saved so many people themselves.
|
Any idea how deep the water is in the search area?
|
Originally Posted by gulliBell
(Post 9712551)
Any idea how deep the water is in the search area?
|
Has anyone listened to live atc for the hours after R116 went missing? At around 0250am R118 and R115 start searching the BlackSOD bay area. If only they had have known R116's last known position on AIS they could have started searching there instead of the wrong area and possibly have found the captain in the water sooner. I'm still listening to it at present. Does anyone know where they found the captain in the water? Was it close to BlackROCK?
http://archive-server.liveatc.net/einn/EINN2-Mar-14-2017-0230Z.mp3 |
Originally Posted by gulliBell
(Post 9712551)
Any idea how deep the water is in the search area?
|
1 Attachment(s)
Originally Posted by gulliBell
(Post 9712551)
Any idea how deep the water is in the search area?
http://www.pprune.org/attachment.php...1&d=1490021446 |
| All times are GMT. The time now is 12:34. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.