What stops vertical flight?  
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What stops vertical flight? - 12/22/2003 9:51:19 PM   
MHawker



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Joined: 3/1/2002
From: San Diego, CA, USA
Status: offline 		I was pondering today...rather than working. What is it that stops a plane from climbing vertically? I know a lack of power, but why does it happen? Is it thin air plus lack of oxygen?

Thanks and Happy Holidays.

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Anyone know any good blonde jokes? I'll start- "There was this blonde customer service rep..... "
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RE: What stops vertical flight? - 12/22/2003 10:27:38 PM   
mAvRiCk


 

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From: East Longmeadow, MA, USA
Status: offline 		Hmmm..I never thought about that, but it has a great deal to do with thin air I believe. Out in Colorado they need bigger engines and they have thinner air so this is most liek;y the problem.

NICE THOUGHT...

Happy Holidays to you also

Dan

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RE: What stops vertical flight? - 12/22/2003 10:47:46 PM   
ZAGNUT



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From: tel-aviv, ISRAEL
Status: offline 		could it be...GRAVITY??

dave

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RE: What stops vertical flight? - 12/22/2003 10:52:58 PM   
MHawker



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Joined: 3/1/2002
From: San Diego, CA, USA
Status: offline 		But doesn't the pull of gravity get less the farther away you get?

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Anyone know any good blonde jokes? I'll start- "There was this blonde customer service rep..... "

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RE: What stops vertical flight? - 12/22/2003 10:56:51 PM   
mAvRiCk


 

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From: East Longmeadow, MA, USA
Status: offline 		Hey again, don't worry I always thought the same, but the prop can't push through that thin air like here in Connecticut, IMO. Maybe someone else can help us out. Interesting TOPIC.

Dan

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RE: What stops vertical flight? - 12/22/2003 11:11:16 PM   
Stick Jammer



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Status: offline 		Power to weight guys. Thin air or thick air, if you have more weight than thrust it can't continue to climb once the initial air speed is lost.

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RE: What stops vertical flight? - 12/23/2003 12:02:29 AM   
MHawker



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From: San Diego, CA, USA
Status: offline 		Sure, but the only reason the power makes a difference is that it overcomes the "unknown" of this equation.

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Anyone know any good blonde jokes? I'll start- "There was this blonde customer service rep..... "

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RE: What stops vertical flight? - 12/23/2003 12:24:56 AM   
mAvRiCk


 

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Status: offline 		TRUE, TRUE

I am soo positive that it has somethin to do with THIN and THICK air!!!

Later

Dan

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RE: What stops vertical flight? - 12/23/2003 12:54:55 AM   
destructiveTester


 

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From: london, UNITED KINGDOM
Status: offline 		thin air is indeed the problem - as altitude increases air thins out - oxygen levels drop, wings become less efficient, but then again drag reduces as well.

i suspect that with an IC engine reducing oxygen levels become the limiting factor before prop inefficiency really stops you going any higher.

space flight and high altitude flight seems to largely centre around engine design - so I guess that's the limiting factor really: thrust.

I'm sure the height differential between colorado and sea level is sufficient to note a difference in performance between aircraft - but here in the UK where the air is pretty thick, I see guys prop hanging on what sounds like 25% power. I don't understand it either

i guess its all that nitro in their competition fuel........

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RE: What stops vertical flight? - 12/23/2003 2:08:00 AM   
Tall Paul



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From: Palmdale, CA, USA
Status: offline 		IF the vertical travel is due to horizontal speed being converted to altitude, when the momentum of the plane runs out, the vertical travel quits.
If the vertical travel is due to thrust exceeding weight, then when atmospherid effects affect the power output, the vertical travel quits.
Models will seldom encounter #2, but will go out of sight when sufficiently overpowered... at which point it's academic, as altitude has to change a LOT to encounter the physical effects of the atmosphere.

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RE: What stops vertical flight? - 12/23/2003 4:45:14 AM   
acropilot_ty



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From: Dana point, CA, USA
Status: offline 		There are two reasons that an airplane will stop a vertical climb... one is power to weight ratio which everyone has been mentioning... As you go up in the atmosphere the air density gets less... the ratio of local density to the density at sea level is called sigma. At 5,000 (like Denver) sigma is .8617, that means that the engine will only make 86% power even at full throttle. At some altitude the power, or thrust, and weight will be exactly matched and the airplane will no longer climb vertical. This site has a standard atmosphere table http://www.pdas.com/e2.htm However, I think the way the question was asked had more to do with momentum, or entry speed, then it did with altitude... If your at low altitude and you pull your model to vertical and it stops climbing at some point low enough that it is still in sight it has nothing to do with thin air... the change in air density is so slight with just a few hundred feet of climb that it certainly is not what stops the climb... in this case the plane has a thrust to weight ratio that is less then 1. If you measure static thrust with a fishing scale and it is less that the weight of the aircraft then it will not be able to climb out of site. This doesn't mean you can't go vertical, it just means that you can't go vertical forever... eventually it'll slow down gradually and finally it'll stop... if your real good it'll back up doing torque rolls

Ty

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RE: What stops vertical flight? - 12/23/2003 4:42:05 PM   
MHawker



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From: San Diego, CA, USA
Status: offline 		Thanks for all of the answers. This has actually turned out to be much more thought provoking than I originally thought.

To clarify, I was concerned with strictly vertical flight and not the momentum carried into the climb. If I had a plane with, let's say a 1.5 power to weight (but the ratio is not important), it would accelerate vertically to a point and then stop. What causes it to "stop"? I know it's a lack of power, but why does it climb relatively easy from the ground up to that point?

For instance, I can take my Magic and hover it at, let's say, 1/2 throttle. Then when I go full throttle, it will accelerate vertically out of the hover to a point where it can't go any higher. So, something between the hover point and the end point has affected it's ability to produce thrust. What is it that affects it's ability to produce thrust?

Is it that the initial torque of the motor starts a climb and creates momentum? Then, that momentum finally is used up?

I knew I should have paid attention in Physics class!

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Anyone know any good blonde jokes? I'll start- "There was this blonde customer service rep..... "

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RE: What stops vertical flight? - 12/23/2003 5:03:56 PM   
Montague



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Status: offline 		Sounds to me like you're having non-aerodynaic issues.

If you have a plane that can hold a steady hover, then climb out of it, it would easily be able to climb right out of sight. If it can't then something else is going on.

My first thought was pilot error. When I climb really high, it becomes really hard to tell exactly where the nose is pointed. Any gust of wind or whatever will knock it out of vertical, and it's nearly impossible to get back in alighment when the plane's just a dot.

Beyond that, I'd say it's a problem with your engine. It might be slowly going lean and slowly loosing power due to overheating or just lack of fuel, and that's causing just enough drop in RPM to cause the climb to stop.


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RE: What stops vertical flight? - 12/23/2003 5:46:21 PM   
Frankenthumb



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From: San Diego, CA,
Status: offline 		Mike,

I'd say it's due to pilot error. I've seen you fly your Magic, and it's a better flyer than you are!

Seriously, I don't think that it stops climbing, it just looks like it does. Think about it this way: as it climbs higher (and farther away from you) your angle of perspective changes more slowly, and therefore it looks like it's slowing down. Much the same way that when you go to a NASCAR (I know you don't like NASCAR, just go with me here) race and the cars whip by right in front of you your head moves really fast to follow them. But after they have passed you, you hardly need to move your head at all to follow them.

It's inconceivable to me that in the 100 or so feet that you are climbing through there is enough of an air density change to have any effect at all on the performance of your engine. If there was, then traveling from sea level to Denver (a 5000' delta) would probably be deadly.

Does that make ANY sense, or am I losing it?

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RE: What stops vertical flight? - 12/23/2003 5:56:51 PM   
Boss248



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Joined: 12/4/2003
From: River City, TX, USA
Status: offline 		I understand and agree with the aerodynamic principles but the fundamental law of the universe which is GRAVITY, cannot be ignored. If the gravity was 1/2 what it is now then our feet would not hurt as much as they do after standing for a long time

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RE: What stops vertical flight? - 12/23/2003 7:02:40 PM   
David Cutler



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From: Los Angeles, CA, USA
Status: offline 		The roof.

-DC

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