SAR offshore letdown procedure
 

Hello!
Can anyone explain the procedure for a radar letdown in IMC in an offshore/coastal area used by SAR aircraft?


Regards,
LZ4.

Start above SALT, clear the area you want to descend into using radar to detect obstructions/ships/cliffs etc, descend into cleared area using FCS/FPC/autopilot/SAR modes as required, close to target until visual or at minimum radar range.

Simples:ok:

LZ4, I think the procedure is the same as on shore.

They start off by saying they want to stay friends....

Thanks for the info Crab.


How much separation would be maintained to obstacles/cliffs etc. during the letdown to the cleared area. How much sea room would be required for instance in a coastal area?

Is it possible for the approaches to the cleared area to be made out of wind in the Sea King?

Regards,
LZ4.

The RAF SARF generally work to 1/4 mile minimums on radar. As for the out of wind bit, the pilot can fly the attitude part of the letdown manually, thereby negating the kit limitations, but it is VERY advisable to be into wind just prior to achieving the hover. Training ideal is into wind with 50 kts on the clock if still IMC.:ok:

Intrigued to understand why you want to know this LZ4?:)

In terms of sea room, the trans down point from 200' is usually 1.25 nm downwind of the target point.

If you make a modified approach ie start the TD from downwind or crosswind and fly the turn manually to end up into wind then that distance can be reduced - it depends on the local geography, the direction of the wind and what obstacles there are; we do not overfly radar contacts in IMC below 1000 ft.

There is a whole other debate about what sort of radar you need to do this safely in all conditions but I won't start that again:)

Pretty sure the boys n girls at Garda Cósta na hÉireann could help. Have you asked them?

To be on the safe side with an offshore wind, we usually advise to let down a little further away from shore (2nm at the bottom of the letdown), especially if there are cliffs or higher ground on or near the coastline. This is for two reasons, to allow yourself more space in case of an engine failure on the letdown. Secondly if the wind is up, to keep the aircraft away for turbulence in the lee of any high ground. At he base of the letdown you can always move in at 20kts reducing speed as you get closer to land. Theoretical minimum range for the Sea King radar is 78 yds but 150 yds is usually more realistic.

Hope this helps.

What sort is that, then?:E:oh:

InTgreen & 2ndclasscitzen many thanks for the info!

Tallsar,
I'd heard of various SAR aircraft using the procedure and just had an interest about how it was carried out.

Pasptoo,
No, I haven't talked to them about it, was thinking some of them might be on here.Actually it would be interesting to hear another perspective on the procedure as well. The procedure used by CHC, for the Irish Coast Guard S-61 or HM Coastguard S-92.


Crab,
Thanks for the explanation and yes, that 330 versus 120 debate!


Regards,
LZ4.

Now that I've heard the RAF Sea King procedure I'd be interested if anyone could explain the procedure for a radar letdown in IMC in an offshore/coastal area used by civilian SAR aircraft such as the S-61 or S-92?

How much separation would be maintained to obstacles/cliffs etc. during the letdown to the cleared area. How much sea room would be required for instance in a coastal area?
Is it possible for the approaches to the cleared area to be made out of wind?

Would like to hear it from a different perspective, using 120 degree radar.


Regards,
LZ4.

...or it's just not possible...360 deg radar = 3 times as good as 120 deg radar, just like everything else about mil SAR:E

It had been a very long night. It was about midnight. We had already carried out a full 2 hour sortie in the SAR Wessex from Chivenor, looking for the source of a mysterious 'red flare' seen by several people from the North Devon coastline.

The coastguards had given us a large block of water to search, about 2 to 3 miles off shore. I was carefully following the Navs instuctions from the left hand seat as he monitored the search pattern using our ancient Decca machine dials and an almost incomprehensible map.

It was pitch black and at 500ft with no radalt hold or autopilot fitted, I was fully occupied with my instrument scan. The only person looking out was the third man of the crew, the winchman, sitting in the open doorway scanning with a pair of hand held NVG's. (The SAR Wessex was not fitted for NVG's and only the rear crew could use them to aid in searches)

Just as I announced we had only sufficient fuel for another 30 minutes of searching (and hoping we had probably been the victim of yet another 'FAWGI'
('false alarm with good intent') the winchman's incredulous voice called out on the intercomm; "Target sighted!"

"Two o clock, 1/4 of a mile, approximately, man in single seat dingy, waving"

What happened then was, on reflection, the crews first night 'drum winching circuit', conducted by the winchman on NVG's, the pilot on instuments and the Nav on adrenaline.

We found ourselves at a 30 ft hover (manual) with the casualty in the 2 o'clock at 10 units, (about 50 ft away).

Now in the Wessex, as the Nav has to climb vertically down into the cabin to take his position as winchop, the SOP was for this to be carried out (safely) at 500ft. The Nav sat with a set of dual controls in front of him. The 500ft was in case the Nav slipped on the rubber covered steps as he lifted his seat and gingerly extricated himself down into the cabin area. (Especially difficult if the Nav was slightly 'portly' around the tummy area.)

Our Nav tonight had the nickname 'Bear'.

He was not a slight man.


What to do? If we went up and around to 'safely' move the Nav at 500ft we would never get back to to this almost ideal position for picking up the casualty.

I made my decision and the crew agreed. The Nav unbuckled himself, stood up and pulled the seat up behind him. He took one step down the damp rubber waterproof indentations.

He then slipped down the rest of the steps until he came to rest, his movement arrested by the co-pilots cyclic firmly jammed between the inside of his lifejacket and his shapely body!

Shall I continue?

(Years later, I discovered Seaking night letdowns were like a breathe of fresh air!)

Please!

;)

SAR Let Down
 

Civilian SAR aircraft have the ability to change direction whilst in flight. This enables them to fly a shortened circuit over the let down area to check for surface contacts and arrange the approach direction accordingly.

Mark on top (MOT) or Trans down to hover (TDH) will take you into the hover at the appropriate position.

The military guys would like you to think that it's a 'black art' that needs Navigators and 360 deg radars. It's mainly common sense...

Pip pip!

Sarowl - you must have gone to the same SAR school as the SARH winners - you know, the ones who didn't carry out a safety case analysis of the radar requirements for safe let downs in all conditions but still won the contract!

Crab, can you just your bitching and sniping for 2 minutes.
None of the radars either Sea King or civsar/oil and gas are fully certified for what they are used for. The offshore safety case has been developed over many years and many letdowns. The CAA recently produced a paper about so the safety case is done elsewhere.

Having a different radar just means a different technique that's all. Doesn't mean less capable. If you want to get snotty about poor kit you should ground all of the mk3s for only having a simplex afcs.

Ttfn

SAR Radar
 

Also in civilian SAR the radar and FLIR picture is available to the PNF. Radar forward and FLIR pointing aft gives full 360 deg cover in the hover. In a Sea King, whilst winching, the radar/FLIR is unmanned leaving the Pilots in the dark. The Sea King has a blind arc straight in front - the worst place for it.

Cheers

Is that a special top of the range FLIR that can see through fog then? :rolleyes: Are you really on SAR, SARowl?