phxpilot
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What If You Had A Giant Fan?

Tue Jul 01, 2008 7:28 pm

In an effort to mimic the epic conveyor belt topic, what if the airport placed a giant fan at the end of the runway? Of course the fan would need to be about 300 feet in diameter in order to cover the largest wingspans, plus a little extra. It must also be capable of producing ~160 knots by the time the airflow got to the airplane. Aircraft performance is all about relative wind so theoretically, even if the airplane was stationary, with enough relative wind it should be able to fly.  biggrin 

Feel free to discuss amongst yourselves.  box 
 
KELPkid
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 7:31 pm

What would happen once you flew outside the fan's airflow? Talk about wind shear...  Wow!
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bond007
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 7:41 pm



Quoting KELPkid (Reply 1):
What would happen once you flew outside the fan's airflow? Talk about wind shear...

Well, it's simple. You attach the fan, via a long piece of 'something' to the front of the airplane. That way, when the airplane lifts off the ground, so does the fan ... but wait ... when the plane moves forward, so does the fan .... I've got it  Smile

...hmmmm ... now the fan's moving, so the relative airflow is .......


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
cdekoe
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 7:52 pm

Sooo... does the fan in your example blow... or suck?  Yeah sure
We can't solve problems by using the same kind of thinking we used when we created them.
 
WPIAeroGuy
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 7:56 pm

You would have a giant air-blender and nice splattering of birds, bugs, and remnants of those poor souls who attempted a go-around.
-WPIAeroGuy
 
bond007
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 7:59 pm



Quoting WPIAeroGuy (Reply 4):
remnants of those poor souls who attempted a go-around.

... or attempted to land opposite direction!


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
GST
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 8:01 pm

Lets ssee...maybye, if we take the fan, make it smaller, and attatch it to the front of the plane?
 
Soku39
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 8:03 pm

300' diameter fan? Well something like this would happen when you got to 310' AGL. Stall, Crash, Done.

I like GST's idea much better.
The Ohio Player
 
Mastropiero
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 8:06 pm

I´d say "it" would hit the fan pretty quickly.....
 
David L
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 8:26 pm



Quoting KELPkid (Reply 1):
What would happen once you flew outside the fan's airflow? Talk about wind shear...

That would depend on how steep the speed gradient was between the "core" air and the surrounding air. If the gradient was shallow enough for the aircraft to accelerate to flying speed as it left the core airflow, it would be OK. However, wouldn't that defeat the purpose of the fan, since the aircraft would have to accelerate from zero to flying speed at some point, anyway?

Quoting GST (Reply 6):
Lets ssee...maybye, if we take the fan, make it smaller, and attatch it to the front of the plane?

That's just ludicrous. It'll never happen.
 
KELPkid
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 8:53 pm



Quoting Bond007 (Reply 2):
Well, it's simple. You attach the fan, via a long piece of 'something' to the front of the airplane. That way, when the airplane lifts off the ground, so does the fan ... but wait ... when the plane moves forward, so does the fan .... I've got it

As I recall, since shortly after Orville and Wilbur and Glen Curtis, that's how we've been flying  Smile (well, except for guys like Dick Rutan, who, in the name of not doing things the conventional way, still insist on the same prop, erm, fan, placement as the Wright Brothers used...)  Wink

I recall that my instructors Cessna 172-180 (172 with a Great Planes 180 HP engine conversion, using the climb prop) and Horton STOL craft kit could almost be hung on the prop...you could hold it with zero indicated airspeed and stall horn bleating like a tortured sheep and the engine at full throttle. You could keep it there until the oil and cylinder head temeratures started to climb rather high... Big grin
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bond007
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 9:15 pm



Quoting KELPkid (Reply 10):
Quoting Bond007 (Reply 2):
Well, it's simple. You attach the fan, via a long piece of 'something' to the front of the airplane. That way, when the airplane lifts off the ground, so does the fan ... but wait ... when the plane moves forward, so does the fan .... I've got it

As I recall, since shortly after Orville and Wilbur and Glen Curtis, that's how we've been flying

LOL .... very good, so we have  Smile


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
dw747400
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 10:16 pm



Quoting KELPkid (Reply 10):
I recall that my instructors Cessna 172-180 (172 with a Great Planes 180 HP engine conversion, using the climb prop) and Horton STOL craft kit could almost be hung on the prop...

Never could get a C172-180 to hang on the prop (but we have a cruise prop, maybe that makes enough of a difference), but try it in a C172-210 (aka T-41C)--easily sit with the airspeed on 30 knots, 20+ degrees nose up, and hold level flight.
CFI--Certfied Freakin Idiot
 
GST
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 10:35 pm



Quoting Dw747400 (Reply 12):
easily sit with the airspeed on 30 knots, 20+ degrees nose up, and hold level flight.

But your airspeed wont really be 30kts though will it? Your pitot wont be pointing at the airflow, and so the ram air pressure will be waaay down. God knows what the static port will be reading if you dont have a pitot static tube...
 
wingscrubber
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RE: What If You Had A Giant Fan?

Tue Jul 01, 2008 10:49 pm

What if you only fly on very windy days!!!??*%*%&$@!! Big grin That's kinda like having a big fan...
http://www.youtube.com/watch?v=7_dgrBevUOw

Or what about a big fan like this??
http://www.youtube.com/watch?v=51yVbEb_bLo
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HAWK21M
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 9:00 am

Im thinking.......High RVR on the Runway on days of fog due to the fan  Smile
regds
MEL
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vzlet
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 12:19 pm



Quoting Phxpilot (Thread starter):
Aircraft performance is all about relative wind so theoretically, even if the airplane was stationary, with enough relative wind it should be able to fly.

For safety, efficiency, and consistency of results, the giant fan would have to be enclosed, perhaps in some sort of a tunnel...
"That's so stupid! If they're so secret, why are they out where everyone can see them?" - my kid
 
flyf15
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 2:22 pm



Quoting Phxpilot (Thread starter):
In an effort to mimic the epic conveyor belt topic, what if the airport placed a giant fan at the end of the runway? Of course the fan would need to be about 300 feet in diameter in order to cover the largest wingspans, plus a little extra. It must also be capable of producing ~160 knots by the time the airflow got to the airplane. Aircraft performance is all about relative wind so theoretically, even if the airplane was stationary, with enough relative wind it should be able to fly. biggrin

Feel free to discuss amongst yourselves. box

If you can have a fan blow 160kt air at a plane, as long as that is above the normal rotation speed, you could sit there facing into the fan with the parking brake set, rev of the engines, pull back, and you would take off vertically.


I've seen this happen (on a smaller scale). We had a Helio Courier based at an airport near my house a while back. With winds of 30-40kts down the runway, he could park at the end of the runway, run the engine up, and take off vertically and then continue to climb vertically until deciding to make a turn. Even though ground speed was zero, his true airspeed was 30-40kts, enough for a plane like the Courier to fly apparently. Pretty cool to watch.
 
baroque
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 3:02 pm

It might be easier to have the plane roll down a steep hill. Mind if the wind changed you might have to move the hill - which might not be so easy.  Wink
 
GST
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 3:08 pm



Quoting Baroque (Reply 18):
Mind if the wind changed you might have to move the hill - which might not be so easy. Wink

not so...just build a round hill so from the top you can roll the plane in any direction.
 
WPIAeroGuy
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 4:02 pm

I posted a while ago about sloped runways. Two parallel runways with opposite slopes. The far end of the "landing" runway would be above the height oft he taxiways allowing planes to roll to their gates, and the take off runway would start lower than the heigh of the taxiways and be sloped down. Energy that would normally be lost to braking would simply be used landing uphill, and then the plane could roll to the gate. After pushback, the plane could roll downhill to the runway. It would get rid of expensive tugs and wasting fuel taxiing, and less brake wear during landing could offset the increased break and tire wear of turning on slopes.
-WPIAeroGuy
 
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nighthawk
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 4:57 pm

How about shrinking the fan down, reversing it and strapping it to the wings so that it pushes the plane forward instead?

... oh wait...
 
KELPkid
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 5:05 pm



Quoting Nighthawk (Reply 21):
How about shrinking the fan down, reversing it and strapping it to the wings so that it pushes the plane forward instead?

... oh wait...

Wouldn't that be kind of a sucky idea?  eyebrow 

Quoting Cdekoe (Reply 3):
Sooo... does the fan in your example blow... or suck?

Depends on which side of the fan upon which you stand  silly 
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WESTERN737800
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 7:10 pm

Somone should try setting up a big fan. It could be another Airport movie in the making.
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KELPkid
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 8:01 pm

In a more practical matter, I would hope you could shut the fan off while the aircraft was taxied onto/off of the runway, as I'd hate to taxi a Cessna onto the active while fighting a 150 knot crosswind. Heck, I'd hope the speed was variable, as a 150 knot headwind would be getting up near Vne in the 172  Wink
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bond007
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 8:30 pm



Quoting KELPkid (Reply 24):
In a more practical matter, I would hope you could shut the fan off while the aircraft was taxied onto/off of the runway, as I'd hate to taxi a Cessna onto the active while fighting a 150 knot crosswind. Heck, I'd hope the speed was variable,

Well it's obvious ... 3 clicks, 5 clicks, or 7 clicks for the PCF.

As always, rule of thumb, click again on final so it doesn't time-out... that might be bad.


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
GST
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RE: What If You Had A Giant Fan?

Wed Jul 02, 2008 9:28 pm



Quoting WPIAeroGuy (Reply 20):

You dont need 2 in opposite slopes, just look at CVF. Take off downhill, land uphill.
 
baroque
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 4:47 am



Quoting WPIAeroGuy (Reply 20):
I posted a while ago about sloped runways. Two parallel runways with opposite slopes.

The old runway at the Porgera gold mine in PNG had such a steep slope that taxying up was at a fairly high throttle setting. I have a photographs somewhere, it must have been about 1 in 12 ish. Takeoff downhill happened quite suddenly and straight over a very deep valley.

They moved to a nearly level runway, but I don't think they had any problems with the steep one.

The biggest problem was the time they accidentally resurfaced one of the nearby roads with some of the high grade ore with visible gold instead of the usual overburden. It certainly showed how to get a road excavated in double quick time.
 
phxpilot
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 5:40 am

I'm glad I started this topic 'cause I love the replies. You guys are WAY too funny!  rotfl 
 
MissedApproach
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 1:01 pm

Well, it's not nearly as slick as a conveyor belt or giant fan, but what about circular runways?

http://www.time.com/time/magazine/ar...171,842350,00.html?promoid=googlep
http://technology.newscientist.com/c...circular-runways-for-airports.html

Strange that no one seems to have tried this out, maybe at a smaller regional airport.
Can you hear me now?
 
GST
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 4:39 pm

 
KELPkid
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 6:10 pm



Quoting MissedApproach (Reply 29):
Strange that no one seems to have tried this out, maybe at a smaller regional airport.

Actually, if you research the term "aerodrome", I think you'll find that it refers to a grassy, more or less circular takeoff and landing area (that disappeared as we figured out runways were just a better way of doing things  Wink ).
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bond007
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 7:11 pm



Quoting MissedApproach (Reply 29):
Well, it's not nearly as slick as a conveyor belt or giant fan, but what about circular runways?

The thought of missed approaches, go-arounds, and aborted take-offs is quite frightening, especially with 6 aircraft using the 'circle' at the same time  Smile



Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
KELPkid
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 7:25 pm



Quoting Bond007 (Reply 32):
The thought of missed approaches, go-arounds, and aborted take-offs is quite frightening, especially with 6 aircraft using the 'circle' at the same time



Jimbo

Just make 6 circles  idea 

But then how do you designate them?  Wink

Wonder what you'd do for an instument approach, a big NDB in the middle of the circle Big grin ?
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
bond007
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 7:36 pm



Quoting KELPkid (Reply 33):
Wonder what you'd do for an instument approach

Circle to land!

Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
Mir
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 7:42 pm



Quoting GST (Reply 6):
Lets ssee...maybye, if we take the fan, make it smaller, and attatch it to the front of the plane?

Sounds good. But why stop at just one? Why not have two fans, one for each wing? Or even two per wing if the airplane needed a lot of lift to get off the ground?

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
KELPkid
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 8:09 pm



Quoting Mir (Reply 35):
Sounds good. But why stop at just one? Why not have two fans, one for each wing? Or even two per wing if the airplane needed a lot of lift to get off the ground?

-Mir

Why would you ever want to do that? Just imagine what would happen if one fan failed and the other kept going, you'd have to specially train each and every pilot to deal with just that scenario. I don't think you could let just normal pilots fly a multi-fanned plane. Not to mention all the problems associated with assymetry when one fan quits...(I hear pilots can get awfully hot and start sweating when that happens!). Next thing you know, the airlines will only want to hire pilots with only lots and lots of multi-fanned time, but the lawyers will sue the makes of multi-fanned planes because they are a little trickier to fly than the single-fanned kind, making the multi-fanned ones exhorbitantly expensive to fly around  Smile

Should you design it so the fans rotate in the same direction, or in opposite directions?  eyebrow 
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
flexo
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 8:48 pm



Quoting KELPkid (Reply 36):
Why would you ever want to do that? Just imagine what would happen if one fan failed and the other kept going

I would have to vote "4 fans 4 all aircraft" here!
 
GST
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RE: What If You Had A Giant Fan?

Thu Jul 03, 2008 10:38 pm

Or you could put one fan on the front, and another on the back!

You could even put a small aquafan on the bottom and make plane's long tube thing waterproof, then you will have the option of landing, or "watering" for a swim to break up the monotony of a long flight.
 
jetlife2
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RE: What If You Had A Giant Fan?

Mon Jul 07, 2008 4:32 pm



Quoting GST (Reply 38):
Should you design it so the fans rotate in the same direction, or in opposite directions?

Ours aren't 300', but they're pretty big. They both go the same way.
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