Helicopters can't fly

[magster65]

Why, when they're flying forward at 150+ mph, don't they flip over? The rotor swinging forward creates all that lift then while it's going back doesn't.

 

[QC]

Re: Helicopters can't fly

I am sure someone else who really knows (as opposed to making it up ) will post, but there is a device in the blade linkage that adjusts the angle of attack of the blades as they rotate. This adjustment causes the slight lack of lift in the front that causes a copter to go forward I think. This same adjustment is probably what increases the angle of attack on the retreating blades to compensate for the speed differential between the blades going forward and those heading aft? Is this answer close to your confusion area Mags?

 

[neumanns]

Re: Helicopters can't fly

I didn't know roters went backwards...I thought they went forwards all the time in a circle creating lift all the way around........Ya know in a circle....As in continus<br /><br />It's all in angle of attack

 

[QC]

Re: Helicopters can't fly

Yeah, but the speed of the air over the blades is different if the blades are on the side that are turning toward the direction of travel as opposed to the blades thart are traveling away from the direction of travel. If the forward speed is 150 mph there is a difference of that air speed over those blades at some point (perpindicular to the direction of travel). This issue also occurs with airplnes when turning. The lift on the wing on the "outside" of the turn increases while the lift on the other wing decreases . . .

 

[clanton]

Re: Helicopters can't fly

I think the pitch changes also, as the rotor blades turn.

 

[QC]

Re: Helicopters can't fly

Originally posted by clanton:<br /> I think the pitch changes also, as the rotor blades turn.

Yup, that would alternately be called "angle of attack" . . .

 

[Limited-Time]

Re: Helicopters can't fly

I am by no means an expert, but here’s how I understand it. Quietcat is on the right path. But unlike an air plane that has a fixed wing. A copter employs a variable pitch wing, (the rotor) the pitch changes as the blades revolve. Lift is only created in a portion of the blades (rotors) rotation.

 

[JB]

Re: Helicopters can't fly

Bottom line? Helicopters don't fly.<br /><br />It is the rotors that fly. The rest is just cargo.

 

[Dave Abrahamson]

Re: Helicopters can't fly

The angle of attack(or pitch) of the blades do change depending on their position during flight. As they rotate the pitch lessens on the advancing blade(s). There is a plate called a swash plate that controls the pitch and angle of the whole disc. The bottom half of the plate doesn't move but the to half rotates with the rotor. it is connected to the cyclic(the stick you fly with) and the collective(a handle down by the pilots side.)The collective control raises the entire swash plate assembly as a unit. This has the effect of changing the pitch of both blades simultaneously. That's your up and down.<br />The cyclic control pushes one side of the swash plate assembly upward or downward. This has the effect of changing the pitch of the blades unevenly depending on where they are in the rotation. The result of the cyclic control is that the rotor's wings have a greater angle of attack (and therefore more lift) on one side of the helicopter and a lesser angle of attack (and less lift) on the opposite side. The unbalanced lift causes the helicopter to tip and move laterally. The pedals control the tail rotor(unless it's a NOTAR)and the dictate where the nose is pointing.<br />Confused even more now?<br /><br />Dave

 

[ufm82]

Re: Helicopters can't fly

Helicopters use a swash plate to change the pitch of the blades as they rotate. When they are retreating they are at a higher AOA. When they are advancing, they flatten a bit. This keeps the overall lift equal from each quadrant of the rotation. The pitch ratio between the blades is kept constant by the swash plate. Adjusting where pitch is different results in motion- forwards, backwards or sideways. It's all in that unique thing that sits at the base of the rotor head. <br /><br /> This revolving mass also causes a very high rotational force that is counteracted by the tail rotor. This is also controlled by a swash plate that controls the pitch of the tail rotor. This in turn controls the yaw of the craft. A copter in hover has zero momentum but can "pivot" on its axis by inputs to the tail rotor. Tail rotor failures result in the crashes you've seen on TV where aircraft spiral out of the sky. <br /><br />UFM82

 

[Drowned Rat]

Re: Helicopters can't fly

Here is a video of what a blade does in flight. Scary when you think about it. The narration is in German so turn your sound down, Ouch! Click on the "So here it is" text to see the video.<br /><br /> www.rapp.org/archives/2004/12/rotor/+helicopter+blade+video&hl=en]web page[/URL]

 

[Barbee Q]

Re: Helicopters can't fly

Me Myself and Irene Movie, shows a great example of a Helicoptor.. Lift and Thrust.. <br />They don't fly they whoop,whoop,whoop..

 

[Drowned Rat]

Re: Helicopters can't fly

That was a GREAT scene in that movie BD!

 

[magster65]

Re: Helicopters can't fly

Originally posted by neumanns:<br /> I didn't know roters went backwards...I thought they went forwards all the time in a circle creating lift all the way around........Ya know in a circle....As in continus<br /><br />It's all in angle of attack

Yeah, my way of thinking was if you added a high speed forward velocity to the equation that changed things because the wind comes across the edge of the rotor, not the face like a propeller. So is that the limiting factor for a helicopters top speed (how much flex a rotor can withstand)?<br /><br />Interesting video. I'll never get in a helicopter now

 

[one more cast]

Re: Helicopters can't fly

This pilot can't fly either...or should I say he cant land. http://www.gofish.com/videoplayer.html?gfid=17-7744

 

[Wimperdink]

Re: Helicopters can't fly

gyroscopic forces let it hang on the llfting side. ?

 

[Dave Abrahamson]

Re: Helicopters can't fly

Originally posted by One More Cast:<br /> This pilot can't fly either...or should I say he cant land. http://www.gofish.com/videoplayer.html?gfid=17-7744

Not real, but pretty funny nonetheless <br /><br />Now these are a different story; <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/helicopter.mpeg <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/helicrash.avi <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/Helicopter Crash.mpeg <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/helicoptere_05.asf <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/helicopteraccident.wmv <br /><br /> http://www.alexisparkinn.com/photogallery/Videos/Heli_refueling_accident.mpeg <br /><br />The last one isn't really an accident...just shows how tough they can be.

 

[DJ]

Re: Helicopters can't fly

JB Wrote:<br /><br />

Bottom line? Helicopters don't fly.<br /><br />It is the rotors that fly. The rest is just cargo.<br />

Precisely!

 

[rodbolt]

Re: Helicopters can't fly

while they cannot fly, my uncle used them to beat the air into submission for many years in the USCG.

 

[stan_deezy]

Re: Helicopters can't fly

Having been in three helo's that have met the ground at high speed unexpectedly I fully agree: helicopters can't fly