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To All, this thread has taken a twist for sure. As an old fart having flown helos for 41+ years in many aircraft and job/pilot functions, I have to ask, "When a limitation is exceeded (not to argue does it hurt/damage anything or not), does it get written up/logged"? Do we as individual pilots decide when to write up a limitation, especially those that we intentionally exceed for training/teaching purposes? Does maintenance know that certain limitations have been routinely exceeded as a matter of CFI decisions for training? Maybe ONLY once or twice on most training flights since new? Does the Airframe manufacturer/engine manufacturer state how many times you can repeatedly do these? Do they say never to log these, no problem? Remember, "How far for how long"!

 

As an pilot with good operating practices and a safe outlook & approach to every flight, I can not accept some of the casual mentality expressed here about limitation exceedences. New pilots, I challenge you to never accept this mentality.

 

As far as the HV Index/curve info mentioned by numerous posters here, I find it surprising that so many posters do not understand how the HV Diagram is developed, when it applies, how to use it and fly safely and how many pilots do not know about the aerodynamic transitions that the aircraft goes thru when transitioning from powered flight to autorotative flight. There were many good comments about ops in & around the HV Index.

 

In closing, I want to state that I normally read a lot of post here and evaluate how pilots operate by their posts and comments. I think about new and inexperienced pilots reading these to gain info and knowledge from these post. Those of you that have flown with me know I am sincere in my pilot efforts and teaching processes. Please, all of you fly safe and develop a safe mentality towards daily flight ops. Best to you all, Mike

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JDhelicopter pilot asked you:

 

 

and you replied:

 

 

 

Who is changing things to promote an argument? I already said that this is a discussion, not an argument and I think up until now that it has promoted some good opinions on both sides.

 

 

Yes, engine failure is less likely than a wire strike on a shallow approach, but which is more likely on a vertical approach, engine failure, or VRS, or LTE, and you could still hit a wire or something else since you cannot see directly below you. That's my point. Sticking to it. If you disagree, so be it.

 

Exceeding power limitations: There are limitations for a reason and that is what I'm saying, that is all. I agree that they are exceeded in training and other times but I believe it should be avoided. We disagree and I'm ok with that.

 

To answer you last question, I don't know exactly what ROD you will get into VRS in an R22 at it's lightest operation weight, I have heard 300-500, I always teach a 30kt-300fpm check and avoid 300 fpm when below ETL. This might be a little conservative but for training I believe it is warranted. Would you say that density altitude would affect the ROD number? I have never heard exact figures or seen a chart to this effect, maybe you could enlighten me.

 

 

It all comes down the the mission being flown. I fly in the wire environment where off airport landings are the norm. Sometimes at night with NVG's. It can be easy to miss a wire or other obstruction. This is ONE reason for the steep and slow approach into our spot. Again, it is much more likely to hit a wire or a tree or something like that, than it is to have an engine failure. If in my recon I discover that I can safely make a normal approach then I will take that option. It doesn't happen offten though.

 

That doesn't mean I don't think about what I will do should an engine failure happen. Always have a way out and a place to go as you set up your approach.

 

The 30knt/300' rule is a good rule of thumb in which I also used when I was a CFI. It gives the student a buffer zone.

 

Where I work the maximum ROD is 200'/min. If we go over that at anytime in the approach then we need to make a change or go around. This makes for a very slow and controled approach into where we are landing and also keeps us out the danger area of VRS. The airspeed limit isn't really a factor. We will be below ETL anyway which makes the 200' ROD rule pretty important.

 

The exact ROD needed to get into VRS will vary from aircraft to aircraft. It's been my expierance that it's normaly more than 300'/min. However, it's then you may start to see the early signs your are getting into VRS. You are truly in VRS when your VSI takes a plunge and controls are mushy along with possible yaw variations. I would show my students the onset so they can reconize the early symtoms and recover. Then I would show them later on when they had a better understanding, true VRS in which there were times the VSI would be well above 1,500 ROD.

 

Another reason for the slow and controled approach is to prevent excessive power changes in the later stages of the approach. This too can get you in trouble .

 

I will just say I don't agree with the casual exceedance of aircraft limitations even if it's just for training. Even if there is no inspection required. We'll just agree to disagree on that.

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Regarding wire strikes. I am currently in the beginning phases of collecting data and information for a FAAST (FAA Safety Team) sponsored Wire Strike seminar specifically geared for helicopter pilots. I'd appreciate any pilots with wire strike experience, (doesn't have to be hitting a wire, near misses are also provide valuable information) to contact me, either via email or PM.

 

 

I attended a wire strike course given by the FAA a couple years ago at Santa Monica,. It was specifically geared to helicopters (which is unusual). Pretty basic stuff but good reminders.

 

I investigated a wire strike last year by one of our local PD ships. He was lucky that the wire hit was very small, and contacted the wire cutter head on, neatly slicing the wire in half.

 

I just wish the FAA mandated more lights on towers to help you at night.

 

Goldy

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Forgive me if this has been covered in this string, i have skipped some stuff due to the ranting! :-)

 

It was asked in the Robbie course why there are no wire cutters on or available from Robinson for the the ships they sell, the answer was:

 

Wire strike stats!

 

Wire strikes are the number one cause of heli accidents, with weather being second.

 

over a 5 year period Robbi did a study of wire strikes;

 

In over 85% the ceiling was greater than 1000' (weather was no factor)

 

In over 66% pilots were experienced with over 2500 hours (one might expect that most would be low time pilots, but low timers probably wouldn't be flying in areas that would bring on such accidents)

 

Over 40% of the pilots KNEW the wires were there!

 

There was another study that showed that the helo had to have a pretty good max weight to provide enough inertia to cut the wire, even on a direct 90 degree angle most wires take a lot of force to cut. Some of the larger wires/cables are 5/8" steel!

 

The fact that the Robbies are not heavy enough and the cutters add weight lead to the discontinuation of the cutters. (back in the day it was an option)

 

Ways to avoid wires:

 

"ALL POLES HAVE WIRES!!" when you see one, or a line of poles, always fly OVER THE POLE! (keep in mind that alot of poles have wires on top that are smaller and harder to see, but these wires can be the steel one's thus much harder to break) Also, the steel cables on top are smaller and harder to see, but they are lighter and tighter, so they tend to not sag in the middle between the poles as do the heavier lower wires..

 

"ALL RIVERS HAVE WIRES OR CABLES!!" these can be power lines, telephone cables, or old trolly car cables that have not been used for years!

 

"WIRES OXIDISE, MAKING THEM HARDER TO SEE"

 

"ALL VALLEYS HAVE WIRES OR CABLES" see rivers above!

 

Conduct high and low reconnaissance every time, even if you have been there before! "remember, 40% knew that the wires were there!"

Maintain at least 500' agl at all times.

 

 

aloha,

 

dp

 

ps if you guys have not been to the factory course.. it's the best $500 i have spent in my training! what a deal, and you get 1.2hrs in the 44, my instructor had over 6000 hours of Robbie time alone!

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That's kinda hard to do when you're trying to actually, you know, land, isn't it? :P

 

 

I am sure he meant in cruise flight or unless needed.

 

RMP brought up a lot of good points. Like Goldy I went to a wire strike seminar but it was put on by ALEA. Great stuff!

 

Don't go looking for the wires perse. It is easier to see the poles. As RMP said, all poles have wires and that is a great rule of thumb.

 

If you need help to see which way the wires are running from a pole. Look for the wire supports at the top. The wires will run at a 90 degree angle. This will then help you find the wire. This trick works well with the high tension lines.

 

There can also be a single small strand of wire crossing the road between buildings or poles rather just running along the side of the roads. These are hard to see, even more so at night. This is why we do a nice slow steep approach. It gives the pilot time to see and hopefuly avoid a wire or obstruction. If we were to do a normal approach then more than likely we wouldn't have enough time to avoid them.

 

Add NVG's to the mix. Horizontal lines are hard for the NVG's to pick up. Lines such as wires and horizontal parts of high tension power towers. This is why we look for the tower. At night you will see the tower well before the lines. Even with the search light lighting it up you most likely won't see the power lines until 200-300 feet agl. At that level with a search light you'll be able to see the power lines quite well and then continue on with the approach. You still have to take it slow on the way in because as I said there could always be a single strand going across your LZ.

 

LZ's in EMS are prepared by the emergency responders on scene. Most are trained but you can't count on that. Never, ever, assume anything! There is a great report listed on an EMS site in which I will try to find. In short, there was an EMS helicopter coming in to land. All of a sudden the crew told the pilot to stop. The pilot did so and a wire was identified that had not been when the LZ was set up. This could have turned into a big thing. However, since the pilot took his time going in and everyone was looking outside things turned out well. If I find the story I will post it.

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Landing at an airport or a standard practice LZ is one thing, but if you go into an unprepared LZ, and especially at night, you had better be making a very slow, very steep approach. I know without a doubt that the fire department who set up the LZ did their best to find all the wires, but I won't bet my life on that. They can make mistakes, especially with adrenaline running and pressure to get the LZ ready for an accident victim. Wires are everywhere, and they will kill you if you hit them. Engine failures are seldom fatal, even from inside the dead man's curve, but wire strikes often are. I worry most about what is most likely to hurt me most, and engine failure is near the bottom of my list of worries. I consider it, but not exclusively. There is no way in hell I'm going to make an approach to a scene at any airspeed which will register on the indicator, nor at an angle that I can see through the windshield. I look at the landing area through the chin bubble.

 

At an airport, though, I make an entirely different approach and departure. There, engine failure is the more likely thing that might hurt me, so I fly accordingly. You have to consider the situation on every approach and takeoff, and not just do the same thing every time. Every approach is different, every flight is different, and I try to learn something on every one. I also do my best to stay alive on every one. So far, I've been successful at that.

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...... Can you tell me the ROD that you will begin to encounter VRS in an R22 when at its lightest operation weight?

 

 

I'll take a stab at the million dollar question. Actually most pilots understand very little about VRS.

 

Most believe the 300fpm crap in the rotorcraft handbook. Fact is, it is not even close. Most accidents that people think are SWP are simply the pilot running out of power.

 

As stated before, SWP is a function of downwash velocity. As such, diskloading greatly effects a ships propensity to get into swp. A high disk loaded ship like a 500 is much harder to get into SWP then a 22. Even still a 22 will not enter VRS until you are sinking pretty fast.....how fast?

 

Using momentum theory well calculate the downwash of a r22. I'll assume sea level and gross wt. (because min wt will differ from ship to ship)

 

downwash velocity = square root (Disk loading / 2x air density)

 

First diskloading. area of 497 gross wt of 1370.....gives DL of 2.76 lb/sq ft

 

Density of air at sea level is .002378

 

So now it is just plugging in the numbers.

 

Once done you get 24fps. But we need FPM so multiply by 60 and get a downwash velocity of 1445fpm.

 

Now you begin to enter VRS at .5 the downwash velocity. This is considered "light turbulence". You really dont begine to get into it untill about .66 downwash which begins "severe turbulence and thrust variation".

 

So.....plug in the numbers.... You will begin to experience light buffeting at 722fpm and fully enter at 953fpm. Not exactly what the FAA tells you I know.....but it is what it is.

 

Now vortex ring is not a black hole. You can fall through it. After about 1.0 times downwash velocity you begin to come out and are totally clear at 1.25 time the downwash velocity. At which point you will begin to enter an autorotative state.

 

 

So......Did I get a check plus? :D :D Any door prizes? :P Yes believe it or not....I fly too ;)

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JTravis-yes, you the man.

 

Now all of this assumes a forward airspeed of zero, correct?

 

RockyMtn- Dennis, which instructor did you fly with ??

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I'll take a stab at the million dollar question. Actually most pilots understand very little about VRS.

 

Most believe the 300fpm crap in the rotorcraft handbook. Fact is, it is not even close. Most accidents that people think are SWP are simply the pilot running out of power.

 

As stated before, SWP is a function of downwash velocity. As such, diskloading greatly effects a ships propensity to get into swp. A high disk loaded ship like a 500 is much harder to get into SWP then a 22. Even still a 22 will not enter VRS until you are sinking pretty fast.....how fast?

 

Using momentum theory well calculate the downwash of a r22. I'll assume sea level and gross wt. (because min wt will differ from ship to ship)

 

downwash velocity = square root (Disk loading / 2x air density)

 

First diskloading. area of 497 gross wt of 1370.....gives DL of 2.76 lb/sq ft

 

Density of air at sea level is .002378

 

So now it is just plugging in the numbers.

 

Once done you get 24fps. But we need FPM so multiply by 60 and get a downwash velocity of 1445fpm.

 

Now you begin to enter VRS at .5 the downwash velocity. This is considered "light turbulence". You really dont begine to get into it untill about .66 downwash which begins "severe turbulence and thrust variation".

 

So.....plug in the numbers.... You will begin to experience light buffeting at 722fpm and fully enter at 953fpm. Not exactly what the FAA tells you I know.....but it is what it is.

 

Now vortex ring is not a black hole. You can fall through it. After about 1.0 times downwash velocity you begin to come out and are totally clear at 1.25 time the downwash velocity. At which point you will begin to enter an autorotative state.

 

 

So......Did I get a check plus? :D :D Any door prizes? :P Yes believe it or not....I fly too ;)

 

Huh, ive always though its been relatively easy to get into if you fly like a dumby. If your numbers are right, youd have to be TRYING to get into VRS. Thats good to know, but i think i wont test that theory out hahaha. 953 fpm is a super steap decent, thats like a jetranger in autorotation :P .

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Now all of this assumes a forward airspeed of zero, correct?

 

 

Funny you bring that up....that is another fallacy many have. Actually it takes a small amount of forward speed to enter VRS. About 6kts in the 22. It is also a function of downwash velocity. Downwash velocity called (Vi). The range of forward speed where it is the worst is about (Vi/101.4) or for the 22.....about 14kts. Any slower, and the effects reduce, and any faster they reduce as well. Of course, you can't read any of this on an ASI as they dont read much below 30.

 

Here is a GREAT link. The charts explaining all this are embedded in the article. It is written for larger ships with greater Diskloading so hence the higher rates of descent.

 

vrs link

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Funny you bring that up

 

The range of forward speed where it is the worst is about (Vi/101.4) or for the 22.....about 14kts.

vrs link

 

Maybe there was a good reason I brought it up? Just lucky I guess.

 

Interesting that 14 knots is the magic number in a 22, where do you gain ETL in a 22? About 15-18 knots if memory serves me....so keep it just ahead of ETL, and bad things are less likely to happen to you.

 

Great formulas....geez. Bachelors Degree in aeronautics with a minor in Helicopter Theory? Even Frank would be proud.

 

Goldy

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Joe,

 

If you read those two statements, they are vastly different.

 

1. Letting a student exceed MAP limits so they can correct them.

This means I am OK with letting them exceed MAP limits when it is of no danger so I can then make them aware of the transgressions and they can correct it themselves. In this way, they understand where the limit is, what it is in place for, and how to it can be avoided. This is what I promote.

 

 

2. Being OK with a student exceeding MAP limits.

This is saying I am ok with a student exceeding a MAP period. No, I am not. I make sure that they correct the condition. Again, you are changing my words to further your argument.

 

And I could hit a wire in a slow vertical approach. However, I would be descending so slow, I would be able to back off and fly around the wire. A 200 fpm ROD is 1 knot. That is slower then you or I walk. Do you think that you are more likely to be able to avoid something at 1 knot, or 25 knots? Slow and steep is safer than shallow with speed. This is in the statistics. Obstacles kill far more people than engine failures.

 

 

VRS in an R22 at min operating weight. Lets assume a 870lb EW, a 135 Pilot, and 20 pounds of fuel. At 1025 pounds and at sea level, the minimum ROD at which an R22 will encounter VRS is 549fpm. On the attached graph that is around .44 Vi. This is the outer ring with light turb and thrust variation. If you to have a ROD in excess of 1561fpm to no longer encounter VRS and you will be in a partial autorotative state. Anything greater than about 12 knots will prevent you from encountering VRS.

 

At gross weigh, the minimum is 635fpm to encounter VRS. Again, that is .44Vi. At zero airspeed, it will be around 953fpm. About 14 knots is all you need to be clear of any VRS.

 

Anything with a heavier disc loading will require a higher ROD to encounter VRS. So, a vertical descent, even in an R22, is much safer then a shallow approach with speed. You are well clear of VRS even at light weight in a 100 or 200 fpm ROD.

 

And yes, DA does contribue to VRS. The higher your DA, the higher the ROD needed to encounter VRS.

 

JTravis,

 

I think you are following the Vi/101.4 up the descent angle lines. Those airspeed lines are vertical. So at Vi/101.4, you are at a speed in which you can no longer encounter VRS.

post-2109-1225050144_thumb.jpg

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....

JTravis,

 

I think you are following the Vi/101.4 up the descent angle lines.

 

 

Gotcha on that on. I was following it up the approach angle. You are correct. With that in mind....above about 12-14kts, you are well clear of it. Bad zone 0-12 with about 6kts being the worst.

 

I am in agreement with you on the vertical descent. One thing to keep in mind though..... Most pilots would make a approach, even a vertical one, into the wind. So a zero ground speed approach will give you some AS depending on wind. In light wind conditions, it might just put you in that perfect 6kt zone ideal for SWP.

 

I have always found that just a small amount of forward speed makes for a much easier approach, especially from the visual cues your eyes recieve. I am sure all the CFI's can relate to green students trying to set down from a 4 foot hover, and they drift backwards. The visual cues from a perfectly straight down approach are much more difficult to process. Obviously not impossible, but a factor of several times harder in my opinion.

 

Good conversation by the way!

 

I was one of the guys that believed a lot of the books untill I had the pleasure of hearing Nick Lappos speak at a safety seminar. He motivated me to learn a little more about why the things I like to fly, behave the way they do. It was very enlightening. These are truly crazy beasts we fly and I am amazed someone figured it out in the first place!

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Shithot, a 206 comes down faster than that in autorotation, closer to 1500fpm. Whether 900+ is a steep descent depends on the airspeed. At low airpspeeds, it is, and is dangerous.

 

Jtravis, it's not necessarily forward airspeed you need. Rearward airspeed will work just as well, as in making an approach with a tailwind. In fact, I believe you're in greater danger of VRS with a tailwind than a headwind, because controllability is lower, and you're also in greater danger of LTE, which has killed lots of people. The main rotor has no idea where the wind is from, but the tail rotor does.

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I think it's very interesting that the topic has almost remained completely focused on aircraft performance and not discussed as a human factors issue.

 

I have strongly advocated the Flying in the wire environment course with Bob Feerst at HeliExpo....why not understand the system first so the helo doesn't have to be torqued? Will it eliminate all wire threats? NO! But, if you know what yer looking for with an edjumacated mind, you'll end up relying less on max performance to save some bacon from being smoked.

 

Hmmmm, let's see: fly smarter or fly harder?

 

as always...

 

-WATCH FOR THE WIRES-

 

 

Forgive me if this has been covered in this string, i have skipped some stuff due to the ranting! :-)

 

It was asked in the Robbie course why there are no wire cutters on or available from Robinson for the the ships they sell, the answer was:

 

Wire strike stats!

 

Wire strikes are the number one cause of heli accidents, with weather being second.

 

over a 5 year period Robbi did a study of wire strikes;

 

In over 85% the ceiling was greater than 1000' (w

eather was no factor)

 

In over 66% pilots were experienced with over 2500 hours (one might expect that most would be low time pilots, but low timers probably wouldn't be flying in areas that would bring on such accidents)

 

Over 40% of the pilots KNEW the wires were there!

 

There was another study that showed that the helo had to have a pretty good max weight to provide enough inertia to cut the wire, even on a direct 90 degree angle most wires take a lot of force to cut. Some of the larger wires/cables are 5/8" steel!

The fact that the Robbies are not heavy enough and the cutters add weight lead to the discontinuation of the cutters. (back in the day it was an option)

 

Ways to avoid wires:

 

"ALL POLES HAVE WIRES!!" when you see one, or a line of poles, always fly OVER THE POLE! (keep in mind that alot of poles have wires on top that are smaller and harder to see, but these wires can be the steel one's thus much harder to break) Also, the steel cables on top are smaller and harder to see, but they are lighter and tighter, so they tend to not sag in the middle between the poles as do the heavier lower wires..

 

"ALL RIVERS HAVE WIRES OR CABLES!!" these can be power lines, telephone cables, or old trolly car cables that have not been used for years!

 

"WIRES OXIDISE, MAKING THEM HARDER TO SEE"

 

"ALL VALLEYS HAVE WIRES OR CABLES" see rivers above!

 

Conduct high and low reconnaissance every time, even if you have been there before! "remember, 40% knew that the wires were there!"

Maintain at least 500' agl at all times.

 

 

aloha,

 

dp

 

ps if you guys have not been to the factory course.. it's the best $500 i have spent in my training! what a deal, and you get 1.2hrs in the 44, my instructor had over 6000 hours of Robbie time alone!

 

 

 

I agree with bith of you, except for one thing.

Bob's Feersts "Flying In the Wire enviroment" course is a wonderful tool to educate new to 20,000 hour pilots alike as to how to operate safely in the wire enviroment. I've personally been through it 3 times and learned something new each time.

 

 

Rocky Mtn Hi, those are some great tips. Only one thing I disagree on.

 

"There was another study that showed that the helo had to have a pretty good max weight to provide enough inertia to cut the wire, even on a direct 90 degree angle most wires take a lot of force to cut. Some of the larger wires/cables are 5/8" steel! "

 

Powerlines have taken down C130's. Most Transmission lines (the ones most often hit by helecopters) are ACSR (aluminium clad steel reinfdorced, about 2.5 inches in diamater alumnium with a steel core. The smaller conductors (distribution lines) that are only about 30-50 feet AGL are about 3/8-1 inch alumnium or copper. these can break if hit, but USUALY break at the pole, and if you hit it with the rotor mast it will wrap it up in seconds. I know of a BO-105, an R44, and a UH1 brought down in this manner.

The top wire or wires on all transmission or sub-transmission (anything over 40' tall) are ground wires/static, and are almost always steel. I've seen 3/8 steel wire cut a 369 in half clear through, leaving just one conclusion. If you survive a wire strike without a wire cutter you are lucky as hell, and no level of skill nor no size or weight of aircraft had anything to do with it.

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I am glad you said that GP was always my thought as well, + 6ins hi or low and you have wire in rotors or hooked in skids anyhow, we work on towers (radio not power) & the guy wires on the smaller ones are at least 15mm. steel multi strand, leaves me cold just thinking

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I did not mean to imply wire cutters are the answer. They'll save you but about 10%-20% of the time (basicly only on distribution wires). Worth having on IMO but hardly a solution to the problem. its good ADM that will keep you alive, not gizmos.

Edited by dave7373
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Something to think about. The latest accident in IL that hit the guy wire was pretty high. NTSB states impact was 50 below the top of the 734 foot tower.

 

So the pilot was proably at or close to 700' agl depending on what errors the altimeter had. There are towers higher than that but a quick look shows that tower to be the highest in the area.

 

Does anyone know if there is a way to check NOTAM's for the day of the accident? There is one out now for that very tower. However, the NTSB states the power cable for the light was severed. I was looking to see if that light was OTS on the day of the incident.

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