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-   -   If you're scud-running, don't follow rising terrain. (https://www.pprune.org/rotorheads/648359-if-youre-scud-running-dont-follow-rising-terrain.html)

[email protected] 19th Aug 2022 06:52


Combat Rules applied....not peace time Rules.
Or SAR rules for lifesaving - any other type of helicopter operation shouldn't be flying in anything like this sort of weather, certainly not with fare-paying passengers on board.

the coyote 20th Aug 2022 03:25


Originally Posted by [email protected] (Post 11281145)
Or SAR rules for lifesaving - any other type of helicopter operation shouldn't be flying in anything like this sort of weather, certainly not with fare-paying passengers on board.

Surely even SAR/EMS in the UK must abide by some kind of defined VMC minima?

luckyrat 20th Aug 2022 05:57


Originally Posted by the coyote (Post 11281714)
Surely even SAR/EMS in the UK must abide by some kind of defined VMC minima?

In my old military days VMC was simply “clear of cloud and in sight of the surface “
Afterwards flying military helicopter support as a civilian, we originally had limitations of a minimum 100 foot cloud base above a ridge line, and at least 1000m visibility.
I returned to base on more than one occasion because I felt we didn’t have safe weather conditions.
All ways better to discuss the weather back in the crew room, than in a big snotty heap on the side of a hill!

[email protected] 20th Aug 2022 08:57

I can only comment on what we did on UK Mil SAR - I don't know what limits are in the Bristow Ops manual - but as luckyrat says, if you could see the surface you were legal and on SAR didn't actually have to be clear of cloud. It had to be justified though - normally lifesaving.

HEMS will have higher minima but again, those will be in their ops manual.

I have operated in mountainous terrain day and night in crap weather and it isn't a place to be if you don't know what you are doing and don't have a really good reason to be there.

The pilot in the video didn't really have a clue and should have found a different route - at least he survived to learn the lesson, plenty don't.

Cornish Jack 20th Aug 2022 09:46

The 'play-it-by-ear' limits we used on S&R were tempered by experiences gained/endured by our fellow operators. The Thorney 4-in-a-day callouts which were conducted throughout on Decca and eye-balls-on-stalks lookout, or the Leconfield tragedy of the Whirlwind attempting to climb out of a 'valley trap' and entering a Cb, leaving in pieces at 12000'. While you can train the techniques for S&R, each situation is different and is dealt with individually.

jimf671 20th Aug 2022 23:11


Originally Posted by [email protected] (Post 11281808)
I can only comment on what we did on UK Mil SAR - I don't know what limits are in the Bristow Ops manual - but as luckyrat says, if you could see the surface you were legal and on SAR didn't actually have to be clear of cloud. It had to be justified though - normally lifesaving.

HEMS will have higher minima but again, those will be in their ops manual.

I have operated in mountainous terrain day and night in crap weather and it isn't a place to be if you don't know what you are doing and don't have a really good reason to be there.

The pilot in the video didn't really have a clue and should have found a different route - at least he survived to learn the lesson, plenty don't.


ORS4 Nos 1070 & 1081 apply for UK SAR. These are exemptions and not specific so, yes, the actual limits, and associated mitigations, will be in the contractor's Ops Manual.

SASless 20th Aug 2022 23:38

Memory serves me that in the mid-70's the BHL Ops Manual said "Day- Clear of Cloud"....and maybe 500M Vis but that was what was printed on the parchment.....Reality was a bit different.

Trundling out to the Ekofisk from Teeside one morning with a very senior Bristow Pilot.....I asked for any advice he could offer as I was brand new to the North Sea.

His one admonition was never lose sight of the surface be it dirt or water.

I reminded him that we had not seen either for almost two hours and his reply was ....."Monsieur Sasless.....do as I say do....not as I do!".

He was a joy to fly with and more fun to share a Pint with.

One of his other tricks of the trade was to use ATT Mode on the 212, Force Trim ON....and set the datum for Five Degrees Nose Up during the Hover Check prior to takeoff.....and fly against the Stick Trim so that the aircraft would always want to pitch up....not down.

Were it Scud Running we were doing or just IMC in uncontrolled airspace at low altitude....the difference is more legal than real I am thinking.

Mogwi 21st Aug 2022 16:52

[QUOTE= Whirlwind attempting to climb out of a 'valley trap' and entering a Cb, leaving in pieces at 12000'.[/QUOTE]

Yes, heard him on the way down. WRAF girl in the back for a jolly, as I recall. Very sad.

Mog

Mogwi 21st Aug 2022 17:01

I also remember someone hover-taxiing in cloud up Black Mountain in Norn Iron, to resupply a rebro, when he was caught by a sudden gust of wind and knocked the tailwheel off the Walter. I was asked to find the geographic location for the incident report which read something like “ Blah blah operational risk, blah blah, no forecast of gusty conditions etc”. Unfortunately the grid ref given for the mountain strike was a place called Windy Gap!

How I did larf! :)

Mog


[email protected] 21st Aug 2022 21:36


hover-taxiing in cloud up Black Mountain in Norn Iron,
not entirely an unusual event - fair few got the t-shirt for that one:ok: and plenty of others.

Cornish Jack 22nd Aug 2022 09:49


Originally Posted by Mogwi (Post 11282548)
Yes, heard him on the way down. WRAF girl in the back for a jolly, as I recall. Very sad.

Mog

Deep sympathy for what, I suspect, must run very deep !
I was on the 'other' Sqdn and, even at that remove, and after 60 ish years, the name of the Captain is an instant recall ... Canadian exchange officer, Capt B****r, and those with you - RIP

helispotter 22nd Aug 2022 11:00

The Whirlwind crash being recalled in discussions appears to be described at: aviation-safety . net / wikibase / 157258 (remove spaces for actual link).

helispotter 22nd Aug 2022 11:21

Seems like the helicopter may already have been descending as it approached ridge but hard to tell using only the perspective seen from the video. The collision with the trees occurred very soon after crossing the ridge. So 'feels' more like loss of control due to sudden change in wind conditions than pilot suffering from a loss of visual references? On YouTube, I noticed comment by 'Reese Fortune' suspecting occurrence of retreating blade stall. Not being a pilot, I hadn't been aware this could occur in practice even though I understand the concept. But given the relative movement of trees below, it seems the helicopter made a fairly rapid turn to port after passing the ridge. Direction of rotation of rotor on AS350 is clockwise from above, hence retreating blades would be on starboard side. So wouldn't such a blade stall have cause helicopter to roll / yaw to starboard if it wasn't due to pilot control inputs?

The BBC article quotes Dimitri Flores as saying: "I'm very disappointed with the authorities. They flew over here with helicopters several times, helicopters which cost us millions, but which they couldn't land here...". Was he wanting a pile of mangled helicopters to join the one he had just been on?


[email protected] 22nd Aug 2022 11:27

Helispotter - correct regarding which way a 350 would roll with RBS.

212man 22nd Aug 2022 13:36


On YouTube, I noticed comment by 'Reese Fortune' suspecting occurrence of retreating blade stall. Not being a pilot, I hadn't been aware this could occur in practice even though I understand the concept. But given the relative movement of trees below, it seems the helicopter made a fairly rapid turn to port after passing the ridge.
At least he didn't say it was VRS! I haven't seen his comments but have no understanding of why he might think RBS would be an issue at such a low speed - it is a problem that occurs at high speed and disc loading. The logical conclusion from the video is that he attempted - too late- to make a sharp left turn to exit the conditions, and lost control due to lack of visual references (and skill!)

Ascend Charlie 22nd Aug 2022 21:26

Remember that in the AS350, a sharp control movement can defeat the hydraulics and make the cyclic lock up momentarily. The aircraft can roll rapidly under such conditions.

luckyrat 22nd Aug 2022 22:43


Originally Posted by [email protected] (Post 11282683)
not entirely an unusual event - fair few got the t-shirt for that one:ok: and plenty of others.

Been there various times in that green and rainy land between 1976-1986, got the T shirt and replacement underwear a few times!
However in the civil aviation world the only real pressure to complete the task in unsafe conditions is self imposed.
As professional Aviator’s we feel obligated to finish what we are asked to do. Unfortunately pressure from many external sources can lead to disaster!
Be that management, peer pressure, or the actual person behind you in the helicopter.
Strength of character is at time’s worth more than actual flying skill!
Remember your life is no less important than any other, if you survive the flight hopefully your crew and passengers will…..

albatross 23rd Aug 2022 01:35


Originally Posted by Ascend Charlie (Post 11283298)
Remember that in the AS350, a sharp control movement can defeat the hydraulics and make the cyclic lock up momentarily. The aircraft can roll rapidly under such conditions.

I disagree slightly.
In my experience for what it is worth.

High G will do it. Rapid control movement, not so much.
The controls do not “Freeze” or “Lock Up” you feel feedback but the controls are still fully effective albeit with additional force required.
In the 350D the flight manual states that, if encountered, you have reached the G limit of the airframe.
On the 355, due to the dual hydraulic system, this is indicated by the illumination of the “Limit” light on the caution panel.
In both cases you have reached the “G limit” of the helicopter so are doing something you shouldn’t. Decreasing power, angle of bank or back pressure on the cyclic [ or combination thereof ] will solve the problem.
We used to demonstrate this during training.
As to rapid roll…turning the hydraulics off using the push switch on the collective will lead to an exiting pitch up and rapid right roll especially ar higher speeds.
We also demonstrated this very carefully at slower speeds.
Training was done after a full briefing on the system, symptoms to expect and proper actions for recovery, .rebriefed in the air and done carefully. Not something you would “surprise” somebody with.

An actual hydraulic failure with empty accumulators would lead to the same result of a rapid climbing roll which will get your undivided attention. We had a lot of hydraulic problems when the 350 came on the market. Immediate Actions included: “HORN….. OFF so you can think!”
I have never flown a B.
Flying a 350 with no hydraulic is good exercise..especially for extended periods of time. The Sky Gods usually dictate landing on a small pad in a confined area just for their continued amusement.

[email protected] 23rd Aug 2022 07:51

Albatross - agreed, it needs the high aerodynamic back forces on the retreating side of the disc to overpower the hydraulics on a 350 - it's no different to jackstall on a Gazelle.

High g loading is pretty much impossible at low speeds (unless you are crashing:))

I used to to demonstrate the limit light on the 365 as you describe for the 355 - again high g loading required so usually in a steep turn.

JohnDixson 23rd Aug 2022 11:11

Crab, I’ve always been curious as to why Eurocopter/Airbus didn’t either provide larger servo piston area or higher pressure pumps to eliminate the jack stall possibilities stemming from high control load maneuvers? I.e., accept the higher vibratory control loads, include them in the fatigue calculations usage spectrum, and accept a probably small reduction in component replacement time?


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