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What If You Had A Giant Fan?  
User currently offlinePhxpilot From United States of America, joined Jul 2005, 80 posts, RR: 2
Posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3572 times:

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 

39 replies: All unread, showing first 25:
 
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 1, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3574 times:

What would happen once you flew outside the fan's airflow? Talk about wind shear...  Wow!


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBond007 From United States of America, joined Mar 2005, 5454 posts, RR: 8
Reply 2, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3563 times:



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!
User currently offlineCdekoe From United States of America, joined Nov 2006, 57 posts, RR: 0
Reply 3, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3552 times:

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.
User currently offlineWPIAeroGuy From United States of America, joined Aug 2007, 240 posts, RR: 0
Reply 4, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3545 times:

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
User currently offlineBond007 From United States of America, joined Mar 2005, 5454 posts, RR: 8
Reply 5, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3543 times:



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!
User currently offlineGST From United Kingdom, joined Jun 2008, 938 posts, RR: 0
Reply 6, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3541 times:

Lets ssee...maybye, if we take the fan, make it smaller, and attatch it to the front of the plane?

User currently offlineSoku39 From United States of America, joined Nov 2000, 1797 posts, RR: 9
Reply 7, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3534 times:

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
User currently offlineMastropiero From Spain, joined Dec 2005, 125 posts, RR: 0
Reply 8, posted (6 years 5 months 3 weeks 3 days 18 hours ago) and read 3532 times:

I´d say "it" would hit the fan pretty quickly.....

User currently offlineDavid L From United Kingdom, joined May 1999, 9545 posts, RR: 42
Reply 9, posted (6 years 5 months 3 weeks 3 days 17 hours ago) and read 3523 times:



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.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 10, posted (6 years 5 months 3 weeks 3 days 17 hours ago) and read 3507 times:



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



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBond007 From United States of America, joined Mar 2005, 5454 posts, RR: 8
Reply 11, posted (6 years 5 months 3 weeks 3 days 17 hours ago) and read 3483 times:



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!
User currently offlineDw747400 From United States of America, joined Aug 2001, 1265 posts, RR: 1
Reply 12, posted (6 years 5 months 3 weeks 3 days 16 hours ago) and read 3455 times:



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
User currently offlineGST From United Kingdom, joined Jun 2008, 938 posts, RR: 0
Reply 13, posted (6 years 5 months 3 weeks 3 days 15 hours ago) and read 3440 times:



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...


User currently offlineWingscrubber From UK - England, joined Sep 2001, 854 posts, RR: 0
Reply 14, posted (6 years 5 months 3 weeks 3 days 15 hours ago) and read 3433 times:

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



Resident TechOps Troll
User currently offlineHAWK21M From India, joined Jan 2001, 31712 posts, RR: 56
Reply 15, posted (6 years 5 months 3 weeks 3 days 5 hours ago) and read 3307 times:

Im thinking.......High RVR on the Runway on days of fog due to the fan  Smile
regds
MEL



Think of the brighter side!
User currently offlineVzlet From United States of America, joined Mar 2004, 839 posts, RR: 0
Reply 16, posted (6 years 5 months 3 weeks 3 days 2 hours ago) and read 3251 times:



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
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 17, posted (6 years 5 months 3 weeks 3 days ago) and read 3218 times:



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.


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 18, posted (6 years 5 months 3 weeks 2 days 23 hours ago) and read 3195 times:

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

User currently offlineGST From United Kingdom, joined Jun 2008, 938 posts, RR: 0
Reply 19, posted (6 years 5 months 3 weeks 2 days 23 hours ago) and read 3193 times:



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.


User currently offlineWPIAeroGuy From United States of America, joined Aug 2007, 240 posts, RR: 0
Reply 20, posted (6 years 5 months 3 weeks 2 days 22 hours ago) and read 3181 times:

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
User currently offlineNighthawk From UK - Scotland, joined Sep 2001, 5182 posts, RR: 33
Reply 21, posted (6 years 5 months 3 weeks 2 days 21 hours ago) and read 3159 times:

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

... oh wait...



That'll teach you
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 22, posted (6 years 5 months 3 weeks 2 days 21 hours ago) and read 3149 times:



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 



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineWESTERN737800 From United States of America, joined Feb 2008, 693 posts, RR: 2
Reply 23, posted (6 years 5 months 3 weeks 2 days 19 hours ago) and read 3109 times:

Somone should try setting up a big fan. It could be another Airport movie in the making.


Bring back Western Airlines!
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 24, posted (6 years 5 months 3 weeks 2 days 18 hours ago) and read 3080 times:

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


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
25 Bond007 : 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 migh
26 GST : You dont need 2 in opposite slopes, just look at CVF. Take off downhill, land uphill.
27 Baroque : 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 som
28 Phxpilot : I'm glad I started this topic 'cause I love the replies. You guys are WAY too funny!
29 Post contains links MissedApproach : 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.
30 Post contains links GST : like this? http://www.airliners.net/photo/-/-/0...'_&prev_id=0492691&next_id=1056153
31 KELPkid : 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
32 Bond007 : The thought of missed approaches, go-arounds, and aborted take-offs is quite frightening, especially with 6 aircraft using the 'circle' at the same t
33 KELPkid : Just make 6 circles But then how do you designate them? Wonder what you'd do for an instument approach, a big NDB in the middle of the circle ?
34 Bond007 : Circle to land! Jimbo
35 Mir : 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
36 KELPkid : 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
37 Flexo : I would have to vote "4 fans 4 all aircraft" here!
38 GST : 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 wate
39 Jetlife2 : Ours aren't 300', but they're pretty big. They both go the same way.
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