What if the power grid fails?

[tdog 0]

I know this is not topic for this thread, so perhaps a PM back or just a quick note back... But can you cite your sources for the claim that it takes more energy to make one PV solar panel than it produces over it's lifetime? This is news to me.

{geek talk}
Assuming the cost of production (including energy), plus profit, is built into the cost of the panel - what you are suggesting just does not work out on paper. For size reference, we are talking about a 10KW array for the 1st install (because that is the max size we can get a rebate on) - with another 10KW added each year until the roof is full and we are making about 100KW at peak daylight. The individual PV panels are BP 160 watt units with a 20 year warranty and a 30 year useful life with an expected 7 megawatt/hour power delivery per panel over the 30 year lifetime - or 434 megawatt/hour per every 10KW array.

{/geek out}

[Eule 0]

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I know this is not topic for this thread, so perhaps a PM back or just a quick note back...

I agree that we're getting pretty far afield from wind tunnels. On the other hand, if I send you a PM, nobody else has a chance to see if I'm bullshitting you or not. :)

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But can you cite your sources for the claim that it takes more energy to make one PV solar panel than it produces over it's lifetime? This is news to me.

The short answer is: does the solar cell factory run on solar cells? The long answer is that saying "it doesn't return the energy it takes to produce it" is a simplification of "it returns more energy than it took to produce it, but not enough more energy to pay for the other costs." You might read this, particularly the section titled "Photovoltaics" on page 6 and 7.

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For size reference, we are talking about a 10KW array for the 1st install (because that is the max size we can get a rebate on) - with another 10KW added each year until the roof is full and we are making about 100KW at peak daylight. The individual PV panels are BP 160 watt units with a 20 year warranty and a 30 year useful life with an expected 7 megawatt/hour power delivery per panel over the 30 year lifetime - or 434 megawatt/hour per every 10KW array.

Those numbers pretty much agree with (and may have come from) PVWATTS version 1. These are the BP 3160 panels, right? They guarantee 152 watts per panel, so that's 66 panels for the full 10 kW - about 891 square feet and 2180 pounds, or about 2.45 lb/ft^2 extra load on the roof - something like two to four inches of snow. You must have a pretty big roof if you have about 9000 square feet for the entire 100 kW array.

Looking around the Web, the BP 3160 panels seem to run around $700-$750 (2006 dollars) in small quantity, depending on who you buy them from. The national average residential price of electricity in 2005 was 8.4 cents per kilowatt hour (2000 dollars). To convert the price of a panel into 2005 dollars, I used the calculator linked from here, to get $677-$725 in 2005 dollars. Then I can use the same inflation data as the national average data to figure that the panel would cost about $604-$646 in 2000 dollars. So, if you just took the money you were going to spend on one panel and handed it to the power company, you could buy somewhere between 7.1 and 7.7 megawatt hours of electricity.

The above quick calculation assumes that the installation labor, any maintenance labor, and the inverters and control gear are free and never break. It also assumes that if you have to finance this, you can do it at zero percent interest. If any of those assumptions aren't true, then you could buy even more electricity from the power company. It also assumes that you will always use all of the PV electricity locally and never sell any back to the power company - if that's not true then the PV gains somewhat.

There are some bigger issues that don't yet always come into the equation for retail consumers, like emissions. It could be that Xcel is taking "pollution credits" for your PV installation and sharing some of the love via the rebate. Mostly though you have to be willing to pay more for "cleaner" energy. I'm not saying that paying more is a bad thing, just that it is something that you should be aware of.

Eule

PLF does not stand for Please Land on Face.

[RackJR 0]

I disagree. Knowing the systems as I do, neither the e-stop, or pulling the stick back to zero simulate a power outage. Having been an instructor and a flyer during power failures in tunnels I can say when the power stops, so does flight. Immediately.***


somehow the laws of physics must cease to exist in a tunnel that loses power, right?
Derek (hooknswoop) pointed out that it takes more energy to stop the fans by pulling the stick down than an e stop or power outage, because the brakes require energy to work. if the power goes out, the fan blades don't stop turning immediately (the physics of motion). i was flying in our tunnel (SVCO) when the vibration sensor shut off the fans. i was standing on the wall about 1/2 way up, immediately felt the power go down, flew to the door and exited. Derek flies to the top, after the stick has been pulled to zero, and flies back down, AND THAT'S WITH THE BRAKES WORKING. a power outage might be a problem for someone hanging on to the turn vanes at the top. maybe. but what are the odds of the power going out while someone is hanging on to the top? what number of people can do that (hang on to the turn vanes) in the first place? Derek is right. for 99.9% of tunnel fliers, a power outage at SVCO would be a non issue, just an interesting story to tell your friends.

Say what you mean. Do what you say.

[Paulipod 0]

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AND THAT'S WITH THE BRAKES WORKING

I would be greatly surprised if the solution there has Brakes! As far as I understand (and I look at this technology alot) The solution at all of the R12's from Skyventure are powered by VFD units direct to the Flak-Woods fans.

The Flak-Woods fans are simple direct motor supply - no brakes in there. You could argue that running the motor on less power acts like an electronic brake if the power change was quick... but non-the less that is not a braking system.

It is plain simple wishfull thinking that a power outage would not be noticable - and if you think otherwise I can say with a degree of certainty that you havent experienced one.

Bottom line is - it takes around 300KW to 500KW of power to move wind fast enough to sustain flying in an R12 when there is 0KW you cant fly (quickly) and the amount of intertia/potential in the non-powered fans is not even worth mentioning.

Bodyflight Bedford
www.bodyflight.co.uk

[diablopilot 2]

There is not enough inertia in the fan blades to maintain the suction needed for flight speeds, nor is the flight medium (air) viscous enough to maintain an inertial flow.

The "pull-back" of the stick causes the power to the motors to be reduced gradually, not all at once like in a power failure.

In the SVCO tunnel, a flight test of the e-stop (which also reduces the power gradually, albeit faster than the "pull-back) from an approximate 105 mph airspeed I was able to maintain flying altitude on my belly for about 2 seconds by aggressively de-arching once the e-stop had been activated.

To simulate a power out situation worst case scenario, you could open the RAT doors fully, then while someone is flying have all 4 VFD's shut off simultaneously.

As to the safety issue of a power failure, the risk is minimal. The majority of activity in the tunnel is belly to earth flight in the 2 to 6 foot range. In a power failure most flyers are not going to react quickly enough to do anything other than fall to the net. Even a six foot fall onto the net will probably not cause a significant injury. I've had a 4 way fall to the net in a power outage from 4 feet and no one was injured.

The danger and potential major injuries are far more likely to occur at higher flying speeds, higher flying altitudes, and during transitions. Someone doing a back flip or sitflying over 10 feet during an outage is very likely to be hurt.

edit: spelling

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You're not as good as you think you are. Seriously.

[Hooknswoop 19]

The brakes are the resistors within the VFD's. They act to to slow the motors faster.

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The "pull-back" of the stick causes the power to the motors to be reduced gradually, not all at once like in a power failure.

The tunnel slows down much faster when the throttle is pulled to stop than when using the e-stop. There is a small delay between pulling the throttle to stop and the VFD's taking the motors to stop, but we have the response time set to the slowest setting and the delay between the throttle hitting stop and the VFD's commanding the fans to stop is about 1 to 1.5 seconds.

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To simulate a power out situation worst case scenario, you could open the RAT doors fully, then while someone is flying have all 4 VFD's shut off simultaneously.

The only time the louver doors would be open 100% is for testing or removal of debris after maintenance.

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The danger and potential major injuries are far more likely to occur at higher flying speeds, higher flying altitudes, and during transitions. Someone doing a back flip or sitflying over 10 feet during an outage is very likely to be hurt.

Simply not true at SVCO. I have experienced a power outage (doing backloops) and witnessed shut-downs. The wind speed slows gradually. Air has weight and momentum. The fans have weight and momentum. The air cannot simply stop.

The sky is not falling.

Derek

[RackJR 0]

we've had the discussion going today. Shane (working at SVCO for the next month but normally works in perris) commented that he himself was flying in the perris tunnel when the power went out, and flew to the door and exited. i was personally flying during an emergency shutdown, flew to the door (from 1/2 up the tunnel) and exited. JP's comment that the e-stop takes less time than pulling the stick to zero simply demonstrates that he doens't know as much as he'd like you to think. it takes almost twice as long to e-stop the wind as it does to pull the stick back to zero.
i didn't say the power outtage would go unnoticed. i said it would be a non event for most flyers, meaning that they would not be hurt, simply set down on the net, and be able to laugh about it later.
i cannot comment on another tunnel, as i don't have personal experience. you probably shouldn't either. if you want to find out, come try it. but speaking from someone who has tried it, i can say it would be a non event for 99.9% of tunnel fliers.

Say what you mean. Do what you say.

[RackJR 0]

oh yeah. and i was in the eloy tunnel while they were fixing the braking system, because it had stopped working and it was taking way too long to bring the wind down. Larry was in there with someone i didn't recognize, working in what i took to be their VFD room. i don't know exactly how the braking works, but i know it's there. and not just in our tunnel. throwing out numbers, watts, volts, whatever sounds very technical, and that's great. but the brakes are there and they work. i'm not sure exactly how the microwave works either, but you wouldn't try to tell me that it doesn't heat up my food, would you?

Say what you mean. Do what you say.

[Paulipod 0]

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but the brakes are there and they work. i'm not sure exactly how the microwave works either, but you wouldn't try to tell me that it doesn't heat up my food, would you?

Ok... just because the fans can be reduced in speed (electronically - by the VFD) doesnt mean it has a braking system in the mechanical sense of the words. As has been said the VFD can reduce speed through resistance.

I dont care what any of you say about inertia of wind and the fan blades... bluntly - I think you are all wrong if you think that a spinning fan with no power and moving wind in a circuit have any possibility to sustain flight.

Given the size and weight of our drive system - the winding down time - the amount of moving air - I think we would notice some benefit if this were the case and our power went off!

I have been flying in a couple of tunnels and been dropped 6ft with a change in outside wind direction or pressure loss through doors etc.... let alone having no power on! lol

And - to be a little bolder... I will happily put my money where my mouth is if any of you are confident enough for a wager

Bodyflight Bedford
www.bodyflight.co.uk

[Hooknswoop 19]

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I dont care what any of you say

I can tell........

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Given the size and weight of our drive system

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I have been flying in a couple of tunnels

I do not claim to know what happens in other tunnels if the power fails. I do know what happens at SVCO. Have you flown at SVCO? Have you been flying when the power failed? The nice thing is that faiures of the power or the the tunnel system at SVCO are extremely rare.

Again, if I can jump in, fly to the turn vanes, come back down, and back out the door, all after the throttle has been reduced to zero, with the VFD braking system working, then a power outage will result in the airspeed slowing down even slower than when the VFD braking system is working, then power failures are a non issue at SVCO.

The only reason I even posted to this thread is because I didn't want flyers at SVCO mislead into believing that their safety is at risk in th event of a power failure.

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And - to be a little bolder... I will happily put my money where my mouth is if any of you are confident enough for a wager

I would not bet against you about what would happen at any other tunnel in a power failure, since I have neither witnessed, nor experienced one in any other tunnel. Why would you?

I know exactly how many seconds it takes the airspeed to reach 30mph from topped out, taking the throttle to zero and when hitting the e-stop at SVCO. Do you?

The sky is not falling.

Derek

[diablopilot 2]

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Again, if I can jump in, fly to the turn vanes, come back down, and back out the door, all after the throttle has been reduced to zero, with the VFD braking system working, then a power outage will result in the airspeed slowing down even slower than when the VFD braking system is working, then power failures are a non issue at SVCO.

I believe there is some confusion when the words brake, or braking are being used here.

There is no mechanincal braking system on any of the current SV tunnels.

The "braking" system is electronic in nature, and serve to slow the fan/motor by reducing the power provided to it gradually. It is in that respect that an "e-stop" or "throttle chop" as signifcantly different in outcome than a power outage.

Try the VFD shutoff and see how it performs. Better yet, kill the power to the VFD's themselves. In a worst case scenario (RATs open, 100mph, 6 foot belly fly) it will be near impossible to maintain altitude for more than 1 to 2 seconds, and that's with you knowing it's coming.

What does Rusty say?

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You're not as good as you think you are. Seriously.

[Paulipod 0]

Hey Derek... a little off to mis-quote sections of my text by ommision!

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I dont care what any of you say I can tell........

If I was to do the same from your post I could quote... I'll have a try at the same maybe...

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I do know what happens

... hmmm I can tell? - not nice huh.

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That aside - my point is that alot of input is made into this kind of discussion with no real experience of the situations. I doubt that nearly all posters in this topic have ever actually experienced a real power outage. Press E or turning down the power is not the same.

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Again, if I can jump in, fly to the turn vanes, come back down, and back out the door, all after the throttle has been reduced to zero, with the VFD braking system working, then a power outage will result in the airspeed slowing down even slower than when the VFD braking system is working, then power failures are a non issue at SVCO.

This is where I see the discrepancy. Both the throttle and e-stop are simple control inputs to the VFD. The VFD then responds in a controlled way with gradual speed change. A power outage to the VFD is totally different... and something I would be surprised if hardly anyone has seen an most faclities.

I do not need to have flown in SVCO to know or understand this.... but if it matters SVCO / New Hampshire / Airkix / Orlando / Perris / AZ all use the same control + Drive + VFD technology which I have experienced first hand and at other non-SV tunnels

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I would not bet against you about what would happen at any other tunnel in a power failure, since I have neither witnessed, nor experienced one in any other tunnel. Why would you?

Mostly just wanted to emphasise the point that this is something that I am very sure about... I think a few of the posts previously are based more on guesswork rather than experience or science.


My purpose here is not one of trying to piss you off - say that one tunnel is better than another - say that any tunnel is not safe.... just merely stay with the physics facts of the situation that all facilties are faced with!

Bodyflight Bedford
www.bodyflight.co.uk

[RackJR 0]

"braking" means to me a reduction in the speed of something through an outside means. for instance if you let off the throttle of the car, and don't step on the brake, it will take longer for the car to come to rest than if you do step on the brake. something in the wind tunnel system slows the fans more quickly than they would stop on their own if no outside force were applied. if that's not a brake "in mechanical terms", and the only way you'll accept that braking is happening is if we have a pedal on the floor that we step on after throttling back, maybe you need to get outside of the box a little bit more.

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As has been said the VFD can reduce speed through resistance. ***


that's a brake dude. drum/disc brakes reduce the speed of a vehicle through resistance.

And - to be a little bolder... I will happily put my money where my mouth is if any of you are confident enough for a wager

if you'd like to do that, i'm sure we can accommodate you. since both Derek and i have been in this tunnel during flight, when the fans were immediately taken to zero, and survived with no damage at all, i don't think it's right for anyone to suggest that someone will be hurt by a power outtage. and, as stated in a similar post, a skyventure Perris employee told me today that his experience was nearly identical to mine, i.e. no physical damage when the power grid actually went out. since you don't seem to be swayed by testimony from first-hand experience, it seems the only way you will believe it is to come try it. see you then. however, i do think that barring you having that experience personally, your commentary should be limited to what you have experienced personally. or, if perhaps another person would help sway you, maybe run it by Katie Woods the next time you speak to her. she's been at our tunnel a lot recently, and has certainly seen Derek pop to the top after the power has been brought down, then easily fly down and exit the door safely.

cheers.

Say what you mean. Do what you say.

[Paulipod 0]

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when the fans were immediately taken to zero, and survived with no damage at all

How exactly were the fans taken to zero? - By removing input power to the VFD? If not... this is not a power outage.

Bodyflight Bedford
www.bodyflight.co.uk

[RackJR 0]

ok, so i've listed 3 different instructors, in 3 different situations, within my posts. 1, a pullback of the throttle at SVCO, a slight hesitation, then Derek jumping in, flying to the top, and safely flying back down (happens daily). 2. a vibration sensor trip that immediately shut down the system (happened twice). i was flying one of those, felt the drop, flew to the door and safely exited. 3. a SVPerris employee, flying in the tunnel, when the grid went out. he felt the drop, flew to the door, and exited safely. not sure what else to list, or what other situation you are speaking of.

since we're still on it. if you aknowledge that the VFD's "brake" the system, however they do it (i'm not interested in hearing more about what defines a brake), are the fans simultaneously being powered as well? what i mean is, since you are suggesting that a power outtage is significantly different from an e-stop or throttling back (even though the experience of an instructor says different), why is that? would it make sense, in any way, to continue to power the fans as you apply the brakes? would it not follow logically, that if the brake is electronic, and a power failure would do the same thing to the fans as throttling back, except that the lack of power would disable the "brake", that the slow down time for both the fans and the wind speed would be longer?

Say what you mean. Do what you say.

[Paulipod 0]

Estop / Throttle / Vibration trip / etc etc are all system controlled removal events which result in a controlled reduction of power through the VFD. So not the same as a power outage.

The VFD for want of a simpler explanation is a big electrical resistor. It simply changes the power up or down that goes to an electric motor. Now - when you set a slower speed power setting on a fixed winding motor then the motor will spin at that speed.

In thoery therefore if you change the speed of the motor to one that is slower than the wind... you could say that the fans are 'braking' the wind flow... but understand clearly this is not a braking system - and the fans cannot be stopped by the VFD.

There is not a brake that is applied - nor the choice of if it is on when the power is removed.

So in a power outage the fans will simply turn until their momentum is lost. This momentum is neglibable.

Bodyflight Bedford
www.bodyflight.co.uk

[RackJR 0]

ok i'll give up after this. you seem to conveniently neglect commenting on the fact that someone has been flying during a power grid failure in Perris and flew to the door and safely exited.

nothing in your technical explanation says anything different than what i've been saying. under power, the wind slows faster than with a loss of power. i guess i'm at a loss. i feel like you have not listed any reason why the wind would stop faster under a power outtage, and accept that with power, the wind is slowed by the fan blades more than if there was no power. if a lawnmower is suddenly shut off, no power whatsoever, and you stick your hand into the moving blade, will it not still cut you? if the fan blades continue to turn because of the momentum they possess, are they not still pulling wind? you claim it's negligible. ok, but my experience, and the experience of others who i trust, tells me otherwise. i think i'm going to stick with that.


in my experience, and the experience of other skyventure instructors, there is no reason to believe that a loss of power would be dangerous to 99.9% of tunnel fliers. we could come up with only one, hanging on to the top, and even then felt that with the skill level necessary to be able to hang on to the top, you would probably also possess the skill to slow your descent.

Say what you mean. Do what you say.

[Hooknswoop 19]

Can you explain why it takes more than double the amount of time for the wind to reach 30 mph from 90% using the e-stop than it does using the throtle?

Derek

[Paulipod 0]

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you seem to conveniently neglect commenting on the fact that someone has been flying during a power grid failure in Perris and flew to the door and safely exited.

I doubt this was a power loss from input to the VFDs. More likely a system closedown or similar.

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under power, the wind slows faster than with a loss of power. i guess i'm at a loss. i feel like you have not listed any reason why the wind would stop faster under a power outtage

When changing speeds over 100mph this may be chosen to happen quickly for responsiveness in control.
But what I am saying is that the wind speed will fall quicker in a power loss than when chosen to decrease through the VFD.

All the time the wind is being pushed the motors require an input of 300+KW to provide enough speed to fly. With no KW in the windspeed will drop below 100mph very quickly... and less than 50mph is much like falling.

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but my experience, and the experience of others who i trust, tells me otherwise. i think i'm going to stick with that.

Formulate your beliefs from whichever source you like! I dont expect to be on your list of respected knowledge sources from a few posts on here... Am simply providing you the truth as I know it.

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there is no reason to believe that a loss of power would be dangerous to 99.9% of tunnel fliers.

Most people arent at high risk in a power outage - they will just fall faster than is comfortable. As I said before.... this isnt a pissing contest, I am not saying that facilities are more dangerous or that ours is better etc

Bodyflight Bedford
www.bodyflight.co.uk

[Paulipod 0]

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Can you explain why it takes more than double the amount of time for the wind to reach 30 mph from 90% using the e-stop than it does using the throtle?

Both are system inputs and controlled events. As I didnt write the control software this is speculative but I would guess that in an event where you are unsure of the system safety (ie an emergency stop) you want to simply reduce the power to the motors in a calm way.... using the throttle you would be happy to set speeds to the motor at any power level within safe flying range.

So in short - software parameters that make sense.

Bodyflight Bedford
www.bodyflight.co.uk

[RackJR 0]

have you personally experienced any of the 3 scenarios i listed? when Shane says the power was cut to the Perris tunnel, what does that mean to you?

Say what you mean. Do what you say.

[Paulipod 0]

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have you personally experienced any of the 3 scenarios i listed?

Not sure why that makes much difference - as in these situations I am not saying that flying is an issue. I have personally experienced the first two of your scenarios. Although not a vibration alert - but a fault that wasnt explained to us at the time, but did end us laying on the net wondering why the wind was switched off.

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when Shane says the power was cut to the Perris tunnel, what does that mean to you?

Youd be better placed to ask Shane! - as we have established already 'losing power' can mean a whole lot of things

Bodyflight Bedford
www.bodyflight.co.uk

[Hooknswoop 19]

Then can you explain why the Kw indication goes to zero in about 1.5 seconds using the throttle and immediately using the e-stop? To clarify, the power consumption goes to zero faster using the e-stop, but it takes more than double the time for the wind to reach 30-mph.

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So in short - software parameters that make sense.

that doesn't make sense to me at all. I would think that you would want to have the wind stop as fast as possible in an emergency situation, not have the software bring the wind speed down very slowly when the e-stop is pressed. If you needed the wind to slow down slowly, you could simply use the throttle. "Emergency Stop" and reducing power to the motors in a 'calm' way doesn't make a bit of sense to me.

Again, there is a graphical display of the throttle setting and power setting that shows a very small delay in throttle reponse or dampening.

We had a computer hardware issue a month or so ago (simple fix). The issue resulted in the tunnel shutting down with people flying several times. Not a software controlled shutdown either. Complete and immediate shutdown, the same as a power outage would be. It was a non-event.

My last word on the subject:

If you are flying in SVCO and the power fails, unless you are hanging off the turn vanes, you will be fine, settling to the net and looking at the controller, trying to ask why he/she cut the wind on you. And if you are on the turn vanes (45-feet up), you'll more than likely be fine also. How do I know this?, I have seen it happen. I am not speculating on how a tunnel works that I have never been to and have never flown in. I am talking from personal experience.

Derek

[RackJR 0]

i did ask shane. i posted his response. it was, that the power was cut to the entire tunnel. the grid went out in the area. how does that not cover your "losing power to the VFD's"?
as to the experience of a thing, usually that helps to clarify what parts of a theory are correct. is bedford of the same design as SVCO? if i remember correctly, it's not. so again, i'll suggest that your experience would allow you to comment on what happens in your tunnel. i have, at no time, attempted to refute what your experience was at bedford. i simply don't know, as i have never experienced it personally. i'll take is as good luck that i read this post, however. if i do travel to bedford, at least i'll know that a power loss (or shutdown) there will be different than what i have experienced here in colorado.

Say what you mean. Do what you say.

[Paulipod 0]

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I am not speculating on how a tunnel works that I have never been to and have never flown in. I am talking from personal experience.

Nor am I (assuming you can accept that all of the SV tunnels are much the same when it comes to controller/VFD and fan)

I think we'll have to agree that we disagree

Bodyflight Bedford
www.bodyflight.co.uk