Donut effect on the EH 101
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Donut effect on the EH 101
I have never heard of this before.
Has somebody an explanation why only the EH 101 should have this "feature". How does it work?
LINK
Has somebody an explanation why only the EH 101 should have this "feature". How does it work?
Life-Saving Features: No More Brown-Outs
And the Royal Air Force pilots operating the EH101 in Iraq discovered a life-saving feature of its main rotor blade which even its developers hadn’t counted on. They found a solution to a pilot’s worst nightmare when flying in the desert—“brown out”—which is a dense cloud of swirling sand and dust, virtually blinding pilots as they’re trying to land. To counteract this, the EH101’s ‘winged-tip’ rotor blades create what its pilots call the “donut effect” – a circular window of clear air inside the dust storm that allows them to see the ground as they come in to land.
And the Royal Air Force pilots operating the EH101 in Iraq discovered a life-saving feature of its main rotor blade which even its developers hadn’t counted on. They found a solution to a pilot’s worst nightmare when flying in the desert—“brown out”—which is a dense cloud of swirling sand and dust, virtually blinding pilots as they’re trying to land. To counteract this, the EH101’s ‘winged-tip’ rotor blades create what its pilots call the “donut effect” – a circular window of clear air inside the dust storm that allows them to see the ground as they come in to land.
Donut Effect
Quite incredible. It was apparently one of those lucky unplanned discoveries. I saw it on the documentry on the heli on the Discovery Channel one night. The down draught blows all the dust out and away from the landing spot under the heli allowing the pilot to see where he's going. Viewed from above it looks like a donut or the eye of a cyclone... Wish I had some thing like that now and again...
The Mighty Donut Rules!
Nick was busy wandering about looking for the Krispy Kremes and coffee pot.
Perhaps the Chinook has a "Honey Bun" effect being a tandem rotor design.
Perhaps the Chinook has a "Honey Bun" effect being a tandem rotor design.
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That effect exists on all helos, it can be plainly seen when looking from above. I have hovered an S76 for hours in complete whiteout while looking through clear air at plywood panels placed within 6 feet of the cockpit, in the lower windshield and chin, and have used small stones and features in Black Hawks in dust. The issue that might be different in the 101 is that the "clear" area is a bit farther ahead of the pilot's windows.
In many kinds of wind conditions the dust flows outward ahead of the machine, then upward with the roll cloud, then it blows downwind toward the helo into the center "hole" from above. This then feeds dirty air that obscures the pilot's view. I contend that this effect is not nirvana, it is a case where in low wind there is a bit more usability. I would bet dust landings are still horrible, and this is where the problem lies for all helos.
In many kinds of wind conditions the dust flows outward ahead of the machine, then upward with the roll cloud, then it blows downwind toward the helo into the center "hole" from above. This then feeds dirty air that obscures the pilot's view. I contend that this effect is not nirvana, it is a case where in low wind there is a bit more usability. I would bet dust landings are still horrible, and this is where the problem lies for all helos.
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The BERP blades fitted generate far more lift at the tips. This coupled with the considerable down wash (high mass helicopter) means that recirculation occurs further away from the fuselage.
There is still a huge amount of recirculating dust and to say there is no brownout is not really true. Rather the effect is a 'bubble' of relatively clear air close to th aircraft.
That is my view - having said that, Westlands themselves did not have a real answer to the effect whn this question was asked of tem recently!
There is still a huge amount of recirculating dust and to say there is no brownout is not really true. Rather the effect is a 'bubble' of relatively clear air close to th aircraft.
That is my view - having said that, Westlands themselves did not have a real answer to the effect whn this question was asked of tem recently!
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Heliboy,
I dont believe the idea that the berp blades contribute to this by having less lift inboard - otherwise those crewmen being winched up would have no downwash, and the dents on their helmets suggest otherwise.
Add this wonderful concept of dustless helos to the long list of BERP myths!
BERP Myths:
1) The BERP blades are the best lifters known to man.
2) The BERP blades are great at high speed, making stall much less in an EH101
3) The BERP blades are so advanced, nobody comes close
4) The BERP blades would increase the lift of any helicopter lucky enough to have them
5) The BERP blades move air in strange ways so that dust runs and hides.
Give me a break! There is only one true BERP statement:
The BERP blades are the only blades to ever employ a PR agent
I dont believe the idea that the berp blades contribute to this by having less lift inboard - otherwise those crewmen being winched up would have no downwash, and the dents on their helmets suggest otherwise.
Add this wonderful concept of dustless helos to the long list of BERP myths!
BERP Myths:
1) The BERP blades are the best lifters known to man.
2) The BERP blades are great at high speed, making stall much less in an EH101
3) The BERP blades are so advanced, nobody comes close
4) The BERP blades would increase the lift of any helicopter lucky enough to have them
5) The BERP blades move air in strange ways so that dust runs and hides.
Give me a break! There is only one true BERP statement:
The BERP blades are the only blades to ever employ a PR agent
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here we go again.....
the only defence the blades need is this...
400.25 kmh / 215 kts in level flight
world absolute speed record since 1986
it's just an ex Sikorsky man getting jealous again
DM
400.25 kmh / 215 kts in level flight
world absolute speed record since 1986
it's just an ex Sikorsky man getting jealous again
DM
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dangermouse,
we go thru this each time! The record is a marvelous achievement - I have a signed print of it in my office!
The BERP blade is 1984 technology, a poor blade by 92/225/carson 61 standards, and those who think otherwise are simply wishing for the stars.
If you think the BERP blade is an answer to blade stall, I will send you the atrocious EH101 blade stall chart, which shows that it is about 10 knots slower than a modern helicopter at the same blade loading, showing that the blade is a dog.
That marvelous record was set with raw power and raw blade chord, and raw courage.
we go thru this each time! The record is a marvelous achievement - I have a signed print of it in my office!
The BERP blade is 1984 technology, a poor blade by 92/225/carson 61 standards, and those who think otherwise are simply wishing for the stars.
If you think the BERP blade is an answer to blade stall, I will send you the atrocious EH101 blade stall chart, which shows that it is about 10 knots slower than a modern helicopter at the same blade loading, showing that the blade is a dog.
That marvelous record was set with raw power and raw blade chord, and raw courage.
Last edited by NickLappos; 9th Mar 2007 at 14:01.
Sorry Nick but the Lynx world record,set up 20 years ago now, was not down to "raw power" or "raw courage "as anyone who was present at the time or has flown with Gem engines would know.Although they squeezed a bit of extra power out by water methanol injection it was still an awful lot less power than other contenders have generated,like the "Hi Speed" Dauphin with newer blade Technology or the Boeing 360 ditto,neither of which got even close.
However old the berp blade may be it was streets ahead of its time and the proof is in its performance since....and look out...they're working on Son of Berp.
That should cause a big hiccup !!!
However old the berp blade may be it was streets ahead of its time and the proof is in its performance since....and look out...they're working on Son of Berp.
That should cause a big hiccup !!!
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"Although they squeezed a bit of extra power out by water methanol injection it was still an awful lot less power than other contenders have generated,like the "Hi Speed" Dauphin with newer blade Technology or the Boeing 360 ditto,neither of which got even close."
Interesting fact though, the Dauphin holds the 3km course speed record at only 15 knots slower than the Lynx record.
Also, the Gems in G-LYNX were Gem 60s, which were not only bigger than the Gem 2s in the standard AH1, but were cleared to operate at max contingency power (OEI) for the run, plus the water injection. Thats a jump from 750shp from each burner on a stock AH1 at MCP to 1577shp each on the hot Gem 60s. More power than adding 2 more engines.
The Dauphin record was set with the Arriels pushing 820shp each. The lynx had almost twice the power. Dauphins aren't THAT much lighter than a stripped out, slicked up lynx, are they?
-Mike
P.S. in response to the original thread, I've only lost sight of the ground a handful of times looking straight down from the back seat of a UH-60, and dust has gotten pretty soupy before. Give it a few seconds and you'll start seeing the ground up front too. One of the dust landing techniques the Army teaches these days is to hover down slowly from a decent altitude -- works great on loose dust that goes away, but in use we can do the same thing on a confined LZ, as we get a cone of relatively clear air straight down the center.
Interesting fact though, the Dauphin holds the 3km course speed record at only 15 knots slower than the Lynx record.
Also, the Gems in G-LYNX were Gem 60s, which were not only bigger than the Gem 2s in the standard AH1, but were cleared to operate at max contingency power (OEI) for the run, plus the water injection. Thats a jump from 750shp from each burner on a stock AH1 at MCP to 1577shp each on the hot Gem 60s. More power than adding 2 more engines.
The Dauphin record was set with the Arriels pushing 820shp each. The lynx had almost twice the power. Dauphins aren't THAT much lighter than a stripped out, slicked up lynx, are they?
-Mike
P.S. in response to the original thread, I've only lost sight of the ground a handful of times looking straight down from the back seat of a UH-60, and dust has gotten pretty soupy before. Give it a few seconds and you'll start seeing the ground up front too. One of the dust landing techniques the Army teaches these days is to hover down slowly from a decent altitude -- works great on loose dust that goes away, but in use we can do the same thing on a confined LZ, as we get a cone of relatively clear air straight down the center.
Last edited by TwinHueyMan; 9th Mar 2007 at 18:55.
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I thought it might be interesting to compare EH101 BERP tips against 92 anhedral tips:
Last one from
http://www.b-domke.de/AviationImages...AgustaWestland
Not intending to fan the flames, but aerodynamics has undergone a serious revolution in the past 20 years. A more recent blade will inevitably benefit from the latest 3D CFD flow visualisation techniques. That said, i can't wait to see son of BERP.
Mart
Last one from
http://www.b-domke.de/AviationImages...AgustaWestland
Not intending to fan the flames, but aerodynamics has undergone a serious revolution in the past 20 years. A more recent blade will inevitably benefit from the latest 3D CFD flow visualisation techniques. That said, i can't wait to see son of BERP.
Mart
Last edited by Graviman; 10th Mar 2007 at 14:15. Reason: EH101 picture now shows BERP tip in context.
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taking up your offer
First I agree with Nick, we always go through this discussion, each believing the other is wrong (after all everyone is entitled to their wrong opinion).
Nick, you kindly offered to show me the EH101 stall envelope to justify your views, as this may answer some questions I will take up your offer and hope to see you 'evidence' shortly. But at the same time can you supply a comparison for a 'modern' helicopter (S92?) to show how far behind we poor europeans are? BTW the Lynx CMRB has the same as the normal blade chord except for the tip so 'raw blade chord' doesnt make sense.
no doubt further discussions will ensue
DM
ps twinhueyman; although the Dauphin as the 3km record, by definition the Lynx could have ALL the speed records, thats what 'absolute' means
Nick, you kindly offered to show me the EH101 stall envelope to justify your views, as this may answer some questions I will take up your offer and hope to see you 'evidence' shortly. But at the same time can you supply a comparison for a 'modern' helicopter (S92?) to show how far behind we poor europeans are? BTW the Lynx CMRB has the same as the normal blade chord except for the tip so 'raw blade chord' doesnt make sense.
no doubt further discussions will ensue
DM
ps twinhueyman; although the Dauphin as the 3km record, by definition the Lynx could have ALL the speed records, thats what 'absolute' means
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dangermouse (I like the way his friend says Banana Man!),
The fact is that the EH-101 would gain over 2000 lbs of hover performance if it had the blades off the S92 (or the EC 225 or the Carson blades), even if all were held to the same blade chord. (I don't think it is a "poor Europeans" issue, unless you guys have finally tossed out the French!)
I will dig up the EH-101 blade stall chart, it is an eye opener!
The point I like to make is that the blade has a PR agent (brilliant thing!) and so I have been asked more than once "Why doesn't the S-92 just use BERP blades?" to which I respond, "Because we want to actually carry some payload, and so can't afford the performance loss." This "donut" theory is drawn from the same pool of PR thought!
The fact is that the EH-101 would gain over 2000 lbs of hover performance if it had the blades off the S92 (or the EC 225 or the Carson blades), even if all were held to the same blade chord. (I don't think it is a "poor Europeans" issue, unless you guys have finally tossed out the French!)
I will dig up the EH-101 blade stall chart, it is an eye opener!
The point I like to make is that the blade has a PR agent (brilliant thing!) and so I have been asked more than once "Why doesn't the S-92 just use BERP blades?" to which I respond, "Because we want to actually carry some payload, and so can't afford the performance loss." This "donut" theory is drawn from the same pool of PR thought!
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It seems AW continues to BERP...
(from an AW press release dated 27 Sept 2006)
... I think every blade should use a PR man
Nimby
(from an AW press release dated 27 Sept 2006)
The first flight of a high performance variant of the AgustaWestland EH101 fitted with new technology British Experimental Rotor Programme (BERP) IV main rotor blades, more powerful CT7-8E engines and a new integrated cockpit display system took place at AgustaWestland’s Yeovil facility yesterday. Following an initial flight in the morning the aircraft performed a second flight later in the day operating at speeds up to 135 knots and performing a range of manoeuvres with all results as predicted.
Speaking after the successful initial flights Alan Johnston, AgustaWestland’s Managing Director of Military Programmes said “This event brings together the technology that will give the next variants of the EH101 even greater mission performance. The additional capability these improvements will bring, especially increased payload in demanding hot and high environments, will be of great benefit to our customers who are experiencing ever increasing operational demands.”
The BERP IV Technology Demonstration Programme (TDP), which is jointly funded by the UK Ministry of Defence and AgustaWestland, was launched with seven key objectives comprising reduced first cost, reduced life cycle costs, reduced rotor vibration at high and low speeds, improved hover and forward flight performance, improved damage tolerance, increased erosion resistance and reduced signatures. The TDP is delivering the technology for the next generation of advanced composite rotor blades which will deliver significant improvements in whole life costs and operational capability of future helicopters including variants of the EH101.
Speaking after the successful initial flights Alan Johnston, AgustaWestland’s Managing Director of Military Programmes said “This event brings together the technology that will give the next variants of the EH101 even greater mission performance. The additional capability these improvements will bring, especially increased payload in demanding hot and high environments, will be of great benefit to our customers who are experiencing ever increasing operational demands.”
The BERP IV Technology Demonstration Programme (TDP), which is jointly funded by the UK Ministry of Defence and AgustaWestland, was launched with seven key objectives comprising reduced first cost, reduced life cycle costs, reduced rotor vibration at high and low speeds, improved hover and forward flight performance, improved damage tolerance, increased erosion resistance and reduced signatures. The TDP is delivering the technology for the next generation of advanced composite rotor blades which will deliver significant improvements in whole life costs and operational capability of future helicopters including variants of the EH101.
Nimby
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The lowdown from Lysander Road...
OK, Bunford Lane - but it doesn't sound as good.
Interesting Nimby. Any tech details, or is the design still doing lots of whirl-tower time?
Mart
Interesting Nimby. Any tech details, or is the design still doing lots of whirl-tower time?
Mart
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For Graviman, yes the BERP and SK tips look similar, but its not just about the tip and the BERP "bit" applies to the whole blade too with the tip being the obvious change over a conventional aerofoil section. Nick may be able to shed some light over how the SiK blade section and twist varies across the blade diameter.
Nick, Like Dangermouse (here the similarity ends!) I too would be very interested to see how the BERP blade stall lines change with altitude and compare that with S92.
Do you think that the BERP blade stall line will be a problem for the Merlin crews when flying? Its just that I thought that retreating blade stall was pretty serious and that if it was common on the 101 it would have emerged by now.
It appears that the S92 has evolved a tip very similar in appearance to the 101? I think its right that the 92 is somewhat noisier than the 101 due to high mach tip effects but that is in the rumour world unless anyone can comment. Cant wait to see what son of BERP looks like.
Nick, Like Dangermouse (here the similarity ends!) I too would be very interested to see how the BERP blade stall lines change with altitude and compare that with S92.
Do you think that the BERP blade stall line will be a problem for the Merlin crews when flying? Its just that I thought that retreating blade stall was pretty serious and that if it was common on the 101 it would have emerged by now.
It appears that the S92 has evolved a tip very similar in appearance to the 101? I think its right that the 92 is somewhat noisier than the 101 due to high mach tip effects but that is in the rumour world unless anyone can comment. Cant wait to see what son of BERP looks like.
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I agree with nicklappos on this one. I have included a link to youtube with a video showing the "Donut" if you will. In the SAR world in Canada we refer not to the "Donut" but rather the Turbulent Flow Zone (TFZ), the area of intense airflow from the MRBs. Penetrating this with a person on the winch/hoist can be somewhat challenging.
If the wind is calm in the hover, then height of hover over the ground can make a big "donut", however, as wind increases, the "donut" moves downwind and can be quite challenging to keep someonw in it when hovering.
Merlin Hovering
If the wind is calm in the hover, then height of hover over the ground can make a big "donut", however, as wind increases, the "donut" moves downwind and can be quite challenging to keep someonw in it when hovering.
Merlin Hovering