View Full Version : For Wessex fans
Airtesting G-WSEX yesterday post starboard ECU change.
https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/848x1131/image0000001_6a8ebe9fa1faa32a57b16c3bc3ed5fc7d8db90c4.jpg
https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/848x1131/image0000021_468a9f9b44900f85a0cc1d33472990908260ad36.jpg
PassTheMarmalade
6th Oct 2023, 09:48
That explains the visit to Westlands - had several of us running to the windows like school kids. I assumed it was crew training, so thanks for clarifying. Good photos :ok:
NutLoose
6th Oct 2023, 10:23
That fence looks like an accident waiting to happen.
That fence looks like an accident waiting to happen. When you are located at an Equestrian centre, you have to stop the nags wandering around the HLS:)
helispotter
6th Oct 2023, 21:57
When you are located at an Equestrian centre, you have to stop the nags wandering around the HLS:)
I has same first reaction as NutLoose. Could fence be located further away from actual HLS? Horses will in any case stay away during takeoff unless they are helicopter enthusiasts too!
maxtork
7th Oct 2023, 02:20
Boy does that bring back memories. Glad to see there is still some flying out there.
Maxtork - to my knowledge it is the only one flying anywhere in the world.
Helispotter - unfortunately it is a recent addition because of the limited space available between the stables and the hangar and there are a lot of equestrian events held there for children as well as adults. Most horse owners/riders have no idea about helicopters and safety zones or downwash.
It's not a strong enough fence to affect the aircraft even if you did catch a wheel or skid in it.
The owner would like to move elsewhere I understand.
helithree
7th Oct 2023, 11:59
That rope can perfectly start a dynamic rollover
That rope can perfectly start a dynamic rollover Nope.
Firstly you need the wheels in contact with the ground to get dynamic rollover and secondly the attachments are deliberately weak so that any contact would just rip the ropes off the poles and/or the poles out of the ground.
The fence is cosmetic to demarcate the area where pedestrians and animals shouldn't go.
I've experienced dynamic rollover in an R22 and severe ground resonance in a Wessex and that fence would not have contributed to either incident in any way.
Maxtork - to my knowledge it is the only one flying anywhere in the world.
It may be the only Wessex, but there are plenty of S-58's flying on this side of the pond.
helisdw
7th Oct 2023, 19:18
Nope.
Firstly you need the wheels in contact with the ground to get dynamic rollover and secondly the attachments are deliberately weak so that any contact would just rip the ropes off the poles and/or the poles out of the ground.
The fence is cosmetic to demarcate the area where pedestrians and animals shouldn't go.
I've experienced dynamic rollover in an R22 and severe ground resonance in a Wessex and that fence would not have contributed to either incident in any way.
Are there not two types of ‘dynamic’ rollover?
(1) ‘static-dynamic’ rollover occurs when lifting off / setting down and a skid or wheel pivots against the ground resulting in a critical angle being reached beyond which recovery is impossible and a crash ensues;
(2) ‘dynamic-dynamic’ rollover occurs when airborne and a skid or wheel pivots against an object (e.g. fuel drum, tree stump, fence, etc.) leading to the same critical angle being reached and a similar outcome.
I suspect it was the latter to which helithree was referring - if the rope is as frangible as suggested then it may be less of a dynamic rollover hazard and more of a concern to the tail rotor.
helisdw - I think the situation (2) you refer to is just called a crash and is caused by poor flying.
Dynamic rollover is just dynamic rollover - static rollover is just something falling over.
Gordy - yes it is the only Wessex.:ok:
oldbeefer
8th Oct 2023, 10:36
That's a real treat to see!
(1) ‘static-dynamic’ rollover occurs when lifting off / setting down and a skid or wheel pivots against the ground resulting in a critical angle being reached beyond which recovery is impossible and a crash ensues;
(2) ‘dynamic-dynamic’ rollover occurs when airborne and a skid or wheel pivots against an object (e.g. fuel drum, tree stump, fence, etc.) leading to the same critical angle being reached and a similar outcomeWent down to the flight line one day to find a H-34 lying on its side, had gotten the shakes and fell on its side when doing the mag check so the story went, they had gotten a very bad rough runner. Static or dynamic? ;)
Tickle
9th Oct 2023, 02:14
Great to see! Wessex videos have been quite rare (now I know why!) so I hope there might be a startup video finally hitting YouTube sometime soon!
Tickle - yes, we have been talking about doing exactly that.
Megan - sounds much more like ground resonance - that can easily lead to a rollover but it's not dynamic rollover in the normal sense.
I've had a Wessex padding so badly it was alternately lifting each main wheel off the ground until I shut it down (very quickly) and that was just uneven tyre pressures.
One rolled over and thrashed itself to bits at RAF Shawbury in the very early 90s (poss late 80s) - ground resonance again.
Dynamic rollover is normally as a result of one wheel or skid (the one that would be the uphill one in the hover) sticking during the takeoff and the combined
lateral thrust from the MR plus the horizontal thrust from the TR roll the aircraft that way and adding collective just makes it worse. By this stage application of opposite lateral cyclic is usually insufficient to halt or even slow the rate of rotation.
helisdw
9th Oct 2023, 06:39
Went down to the flight line one day to find a H-34 lying on its side, had gotten the shakes and fell on its side when doing the mag check so the story went, they had gotten a very bad rough runner. Static or dynamic? ;)
Sounds like a very dynamic case of ground resonance! :) I’d suggest that this is a completely different phenomenon, despite being mentioned (and possibly conflated) in a previous post.
My reason for commenting was the assertion that dynamic rollover requires “wheels in contact with the ground” - this is not in keeping with what I was taught and it is evident to me that there is an aerodynamic condition (critical angle beyond which MR thrust leads to inevitable loss of control) which can occur whether there aircraft is in the act of landing / taking off or is fully airborne.
The importance of this point is that by having an awareness that the aircraft can exceed its limits of control whilst airborne should modify the behaviour of the pilot - do not accept any drift when close to the ground and hover taxi purposefully and with care. Of course this seems self evident but there’s plenty of public video footage to the contrary.
Each individual is free to call anything they want whatever they want and I’m always happy to agree to disagree - I’m not here to win internet arguments but hopefully add something to the discussion that might be of benefit to others.
helisdw - I'd be interested to see which documents refer to the condition you describe - you can find reams of stuff on the dynamic rollover I am talking about. Where did you learn it and from whom?
helisdw
9th Oct 2023, 08:31
Here’s a couple of documents that make mention of it occurring whilst airborne / hovering / drifting - one is European and the other American:
https://www.easa.europa.eu/en/downloads/22663/en
https://core.ac.uk/download/pdf/36727638.pdf
This generally occurs when a helicopter is taking off, landing or hovering with one skid/ wheel in contact with the surface. The helicopter may begin to roll about the point of contact with the surface (pivot point). The pivot point could be for example a skid/wheel, stuck or restrained to ground, ice, soft asphalt or mud. It could also be a skid/wheel contacting a fixed object/ground whilst hovering sideways or during slope operations. That is the only mention of it in the first document and, whilst I agree about contact with the ground, I disagree about the fixed object - that is flying into something other than the ground and having an accident.
The second very good article doesn't mention it at all, it is a perfect treatise on dynamic rollover and explains the difference between static and dynamic rollover far better than the EHEST document.
And bear in mind that the EHEST document isn't a training manual it is to help operators to implement their SMS.
The main difference is that in dynamic rollover, adding collective makes things worse (unless you are lucky enough to break ground contact) - but if you drift sideways into a fence or wall or similar obstacle, adding collective will put you above it and remove the problem.
I'm not saying you can't end up in a smoking heap by drifting into something - plenty have done it - but it isn't what is referred to as dynamic rollover as illustrated by the US article.
helisdw
9th Oct 2023, 20:25
Second article, Pg 1. of 3., Para 4 and 5:
“A potential problem develops, however, when the helicopter comes in contact with the ground (a lateral drift for example) and a new pivot point is established”
“Well, just imagine hovering in a brownout or whiteout situation and attempting to land. In the process, due to loss of visual cues, you establish a lateral drift and contact the ground with one wheel or skid.”
I concede the author uses the word “ground” whilst I previously suggested another type of inanimate object - but the principle is identical in that the aircraft is airborne / moving and contacts something that then sets up a pivoting moment.
Your assertion that using collective to rectify colliding sideways with an obstacle elegantly illustrates the point I was originally trying to make - if a rolling moment has been initiated, then adding pitch will likely tip you over due to main rotor thrust. If you chose to not call this dynamic rollover then you are obviously well within your rights; but the fact is that others take an opposing view as they have recognised that the aerodynamics, exacerbating factors and outcome are all identical.
As mentioned previously, this is not about winning an argument - rather it is to try and share some knowledge. It was imparted to me by some highly experienced Canadian instructors (some of who are sadly no longer with us) and I’m am merely passing it on.
We will have to agree to disagree, the whole concept of dynamic rollover is that contact with the ground, whether or take off or landing with drift, where the aircraft is no longer free to move about its C of G but instead around the new pivot point created by the contact between wheel/skid and the ground.
The collision with an obstacle scenario is different, as well as being far less common than the landing/take off scenarios - you have created a temporary pivot point about which the aircraft could start to roll but because you are actually flying and have high collective position already, applying opposite cyclic will have a strong effect because you are modifying the direction of a lot of MR thrust. Additionally, and the reason I mentioned collective helping not hindering, is again because you are flying and a small collective input will gain height to clear the obstacle - that isn't the case with dynamic rollover where the further application of collective exacerbates the situation and accelerates you towards the stuck skid.
In the landing/take off scenarios, the collective is lower, the MR thrust is less and your lateral cyclic has less effect.
Remember also that the classic dynamic rollover happens when the wheel/skid on the advancing side of the disc is the one that sticks on the ground - mostly because the TR thrust is acting in the same direction as the aircraft is trying to drift in - further limiting the effectiveness of your lateral cyclic.
The idea of a 'limiting roll angle' when you are clear of the ground is an erroneous one, when you tilt the disc sideways you reduce the amount of vertical MR thrust but that is easily compensated for by application of more collective. Whereas dynamic rollover can occur with very low levels of roll angle - your 'collision' scenario implies much larger roll angles which, unless you are moving very fast sideways when you hit the object, are not going to be experienced.
In short, I, and most textbooks I can find, regard dynamic rollover as requiring ground contact which is made worse by application of collective - your 'collision' scenario doesn't meet either criteria. Yours is tripping over an obstacle - you would be better comparing a drifting helicopter attached to an underslung load that was too heavy to lift - that is closer to traditional DR but it can happen when moving in any direction, you just run out of cyclic authority.
We went into dynamic rollover in great depth in the Sea King world after two pilots on their Sea King course rolled one over carrying out an ASE out take off - it was unusual at the time because it was on a flat runway instead of a slope. Boscombe Down were tasked to reproduce the accident and successfully rolled theirs over too, leading to the understanding that the aircraft was far more prone to DR than previously thought and exacerbating factors like ASE out, wind from the left (lateral flapback reducing cyclic margins), nose down (increasing the height of the TR thrust) and high C of G (low fuel state) just brought you closer unless you used the correct technique for take off (I mentioned it in an earlier post). It explained a lot of wobbly take offs, especially on rolling decks aboard ship.
megan
10th Oct 2023, 03:47
sounds much more like ground resonance - that can easily lead to a rollover but it's not dynamic rollover in the normal senseThings would have been extremely dynamic in the cockpit Crab, hence the smiley when posing the question. :ok:
helispotter
10th Oct 2023, 06:01
...Boscombe Down were tasked to reproduce the accident and successfully rolled theirs over too, leading to the understanding that the aircraft was far more prone to DR than previously thought...
Are we talking about a simulator here? Or a real Sea King? Surely they didn't total a second Sea King to understand what went wrong in the first case??
Oh, and might be time to change the thread title to "Dynamic Rollover"!... But there probably already is such a thread.
Anyway crab, what ever you do, don't total that last flying Wessex, whether by dynamic rollover, collision with a post, ground resonance or any other way!
Megan - sorry, I missed the smiley:ok:
Helispotter - yes, they did actually total a real Sea King, as I understand it, the US exchange officer who took their briefing for the sortie did a risk assessment and didn't like the outcome - they did it anyway!
I will be trying very hard not to damage the Wessex - it has no ASE due to lack of spares but it's still great fun to fly.
helispotter
10th Oct 2023, 12:13
I guess if they "were tasked to reproduce the accident" they had remarkable success and should be commended for their diligence! :bored:
The discussion also reminded me of a dynamic rollover case reported in Aviation Safety Digest 126 back in 1985, see page 18 of: https://www.atsb.gov.au/sites/default/files/media/5774822/asd_126_spr_85.pdf
The unfortunate pilot of the media JetRanger (VH-CEC) got caught up on the slightly raised side of a concrete refuelling pad which is seen in a photo of the accident scene. Article says the pilot was bringing the 206B to the hover and attempted to correct with cyclic but the helicopter rolled over.
Helispotter - yes, it highlights the problems of aircraft with teetering (or near teetering) heads, they have very little control power (how much leverage the rotor head can exert on the fuselage) so any tendency to DR is even more difficult to fight with opposite lateral cyclic. 206 and R22 are classics in that sense.
ShyTorque
11th Oct 2023, 08:30
Anyone remember the JetRanger that was filmed trying to tow a speedboat? It stayed airborne about four seconds before it rolled over and ditched with a flourish.
Link:
https://youtu.be/29LSg4i6bO8?si=HrBqA9E0TDEdhUh9
Here’s another one:
https://youtu.be/84RScbcF1XI?si=9H_F5WyFEMF8_v92
coley chaos
18th Oct 2023, 16:58
Ive been to one of the hanger tours and met you and the team. Brew and pizza were yummy. The Wessex and collection there are so worthy of note. Not just because of the cabs, but all that is done to keep them airworthy. The tour is in my view, brilliant at getting up and close to machines that I watched as a boy sat on the stone wall by the threshold at HMS Osprey. That Wessex brings out the child in me every time. Bravo to all at HH.