Phxpilot From United States, joined Jul 2005, 60 posts, RR: 2 Posted (3 months 6 days 20 hours ago) and read 1701 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.
Bond007 From United States, joined Mar 2005, 4275 posts, RR: 6 Reply 2, posted (3 months 6 days 20 hours ago) and read 1692 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
...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!
David L From United Kingdom, joined May 1999, 7192 posts, RR: 28 Reply 9, posted (3 months 6 days 19 hours ago) and read 1652 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?
KELPkid From United States, joined Nov 2005, 3417 posts, RR: 3 Reply 10, posted (3 months 6 days 18 hours ago) and read 1636 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 (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...)
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...
Rulebooks and regulations are made from paper...and they do a poor job at preventing metal from contacting rock-Ernest G
Bond007 From United States, joined Mar 2005, 4275 posts, RR: 6 Reply 11, posted (3 months 6 days 18 hours ago) and read 1612 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
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 From United States, joined Aug 2001, 842 posts, RR: 1 Reply 12, posted (3 months 6 days 17 hours ago) and read 1584 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.
GST From United Kingdom, joined Jun 2008, 185 posts, RR: 0 Reply 13, posted (3 months 6 days 17 hours ago) and read 1569 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...
Gliding is to power flying as seduction is to rape.
Vzlet From United States, joined Mar 2004, 724 posts, RR: 0 Reply 16, posted (3 months 6 days 3 hours ago) and read 1380 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
Flyf15 From United States, joined May 1999, 6008 posts, RR: 15 Reply 17, posted (3 months 6 days 1 hour ago) and read 1347 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.
FLYING RULES: 1) KEEP IT UNDER CONTROL, 2) DON'T HIT ANYTHING
WPIAeroGuy From United States, joined Aug 2007, 153 posts, RR: 0 Reply 20, posted (3 months 5 days 23 hours ago) and read 1310 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.
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