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Search: Posts Made By: helisphere
Showing results 1 to 35 of 40
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Forum: Rotorheads
18th Feb 2011, 21:46
Replies: 69
Views: 11,203
Posted By helisphere

Ok, I think the confusing part is static pressure...

Ok, I think the confusing part is static pressure and total pressure. I've read some different things and it doesn't seem real black and white.

If we look at Bernoulli's p + q = p0

And p0 is...
Forum: Rotorheads
13th Feb 2011, 13:11
Replies: 14
Views: 10,540
Posted By helisphere

Hmmm... nice photo, the first thing that jumps...

Hmmm... nice photo, the first thing that jumps out at me is there are no doublers in the highest (bending and tension) stress location where there are also stress concentrations due to the bolt holes.
Forum: Rotorheads
13th Feb 2011, 12:54
Replies: 5
Views: 1,390
Posted By helisphere

Ok here it is: ...

Ok here it is:

http://www.pprune.org/rotorheads/224249-why-does-nose-pitch-forward-when-you-lower-collective.html
Forum: Rotorheads
13th Feb 2011, 12:51
Replies: 5
Views: 1,390
Posted By helisphere

Hmmm... seems like I remember a fairly long...

Hmmm... seems like I remember a fairly long thread on this very subject some time ago.

Anyone have the link? I'll look...
Forum: Rotorheads
13th Feb 2011, 12:47
Replies: 69
Views: 11,203
Posted By helisphere

Graviman, maybe you could give a more detailed...

Graviman, maybe you could give a more detailed description of static, dynamic and total pressure and how they change with ground effect and without...
Forum: Rotorheads
13th Feb 2011, 12:34
Replies: 5
Views: 1,925
Posted By helisphere

I'm asking this because I was test flying an...

I'm asking this because I was test flying an experimental helicopter last year and we had some tracking issues due to blade mismatch, and even in a no wind hover there was a pronounced vertical vibe...
Forum: Rotorheads
13th Feb 2011, 11:31
Replies: 16
Views: 1,953
Posted By helisphere

Well I have about 1000 hours in the 205++ and the...

Well I have about 1000 hours in the 205++ and the 210 all on fires. However I don't have any time in a lama, but I do have about 700 hours or so in the Astar with some longline.

I don't know if I...
Forum: Rotorheads
13th Feb 2011, 10:31
Replies: 21
Views: 4,334
Posted By helisphere

Don't forget that above 40 kts the top of the...

Don't forget that above 40 kts the top of the green on torque is the new red line(didn't make this mistake but saw someone who did). Don't forget to remove the tailrotor guard ( yes, I did this one,...
Forum: Rotorheads
8th Feb 2011, 03:35
Replies: 392
Views: 87,101
Posted By helisphere

Nick, I have a question for you. When you are...

Nick, I have a question for you. When you are taking data with an instrumented aircraft specifically on VRS, does the aircraft have angle of attack or vertical airspeed (besides VSI/ASI)...
Forum: Rotorheads
8th Feb 2011, 02:27
Replies: 392
Views: 87,101
Posted By helisphere

Well the spreadsheet certainly makes you think......

Well the spreadsheet certainly makes you think... I wouldn't have thought to make it if I wasn't reading through this thread.

A little background, I've got about 4000 hours and about 700 longline...
Forum: Rotorheads
8th Feb 2011, 01:29
Replies: 392
Views: 87,101
Posted By helisphere

Nick, I'll agree with you that the situations I...

Nick, I'll agree with you that the situations I am suggesting are not likely to be able to sustain VRS but I think they can create the condition for a short time which probably isn't going to hurt...
Forum: Rotorheads
7th Feb 2011, 07:49
Replies: 392
Views: 87,101
Posted By helisphere

I know I kind of threw those numbers together but...

I know I kind of threw those numbers together but here is a spreadsheet I made that lets you change all the parameters and see a plot on a VRS chart.

The white blocks are for user input and...
Forum: Rotorheads
5th Feb 2011, 21:08
Replies: 5
Views: 1,925
Posted By helisphere

First of all two bladed rotor systems are pretty...

First of all two bladed rotor systems are pretty much always underslung so that the teetering hinge is on the CG of the rotor so that this will not happen. However I do understand that this varies...
Forum: Rotorheads
5th Feb 2011, 20:57
Replies: 392
Views: 87,101
Posted By helisphere

Also, it looks like Nick's example of the R22 for...

Also, it looks like Nick's example of the R22 for vertical and horizontal velocities assumes a level rotor disc which of course is not always the case.

So here is a scenario: I'll use a disc load...
Forum: Rotorheads
5th Feb 2011, 11:33
Replies: 392
Views: 87,101
Posted By helisphere

Nick might just get his wish the way this is...

Nick might just get his wish the way this is going though it seems to be wandering a little bit off topic.

I have to substantiate what Lama Bear and RVDT have said about longline and mountain...
Forum: Rotorheads
5th Feb 2011, 09:22
Replies: 5
Views: 1,925
Posted By helisphere

Out of Track Vibration

When a helicopter is out of track it typically produces a vertical vibration. Can anyone explain this in detail? It seems to me that it would produce a more horizontal vibe similar to an out of...
Forum: Rotorheads
4th Feb 2011, 06:41
Replies: 58
Views: 9,712
Posted By helisphere

When Sikorsky first developed the XH-59 the...

When Sikorsky first developed the XH-59 the engineers thought that because of the high control moment generated by the extremely stiff rotors they should reduce the amount of cyclic control available...
Forum: Rotorheads
3rd Feb 2011, 21:08
Replies: 58
Views: 9,712
Posted By helisphere

Ok I was just curious. You can always change it...

Ok I was just curious. You can always change it if you need more. I just wonder how much will be needed for a real machine considering CG range, slope landing capability and amount of rotor...
Forum: Rotorheads
3rd Feb 2011, 01:11
Replies: 1,224
Views: 765,749
Posted By helisphere

check the announcement at the top of the...

check the announcement at the top of the rotorheads thread
Forum: Rotorheads
2nd Feb 2011, 22:08
Replies: 58
Views: 9,712
Posted By helisphere

Ok I thought you might have just misworded that. ...

Ok I thought you might have just misworded that. So how many degrees does it tilt? Or what did you really mean to say?
Forum: Rotorheads
2nd Feb 2011, 19:56
Replies: 1,224
Views: 765,749
Posted By helisphere

bnzez1qi-YU

bnzez1qi-YU
Forum: Rotorheads
2nd Feb 2011, 19:46
Replies: 58
Views: 9,712
Posted By helisphere

Maybe I am misunderstanding you, but if the...

Maybe I am misunderstanding you, but if the gimbal tilts 3 degrees, it's 3 degrees no matter how close or far from the pivot point. Obviously the distance of movement is larger the farther from the...
Forum: Rotorheads
2nd Feb 2011, 18:49
Replies: 5,672
Views: 4,597,480
Posted By helisphere

http://i80.photobucket.com/albums/j200/string11/Ea...

http://i80.photobucket.com/albums/j200/string11/Eagle.jpg

http://i80.photobucket.com/albums/j200/string11/DSC_0059.jpg

http://i80.photobucket.com/albums/j200/string11/0970.jpg
...
Forum: Rotorheads
2nd Feb 2011, 05:06
Replies: 16
Views: 3,570
Posted By helisphere

I exchanged a few emails with "Tommy" back in...

I exchanged a few emails with "Tommy" back in 1998 and if I remember correctly he said that he tried the loops with different entry airspeeds. That may be why one of the ones in the video ends up...
Forum: Rotorheads
30th Dec 2010, 11:41
Replies: 28
Views: 14,237
Posted By helisphere

I did find this in Wayne Johnson's book,...

I did find this in Wayne Johnson's book, Helicopter Theory:



Interesting that it says large negative delta3 does have adverse effects on flapping stability. That would explain why Bell uses a...
Forum: Rotorheads
28th Dec 2010, 19:17
Replies: 925
Views: 349,848
Posted By helisphere

Don't forget that an integral part of the Lynx's...

Don't forget that an integral part of the Lynx's ability to set that speed record with out any fixed lifting surfaces were the BERP rotor blades, not just the jet thrust.

Ascend Charlie, yes you...
Forum: Rotorheads
28th Dec 2010, 18:50
Replies: 28
Views: 14,237
Posted By helisphere

Here are some pics I took a couple years ago ...

Here are some pics I took a couple years ago

407 Tail Rotor pictures - Photobucket (http://s80.photobucket.com/albums/j200/string11/407%20Tail%20Rotor/)
...
Forum: Rotorheads
23rd Dec 2010, 03:57
Replies: 28
Views: 14,237
Posted By helisphere

Yes he did, that guy was absolutely determined. ...

Yes he did, that guy was absolutely determined. I gave up arguing with him 9 years ago! I don't think my delta hinge question quite has the power to pull that off :) But maybe a good ole snail...
Forum: Rotorheads
22nd Dec 2010, 05:15
Replies: 28
Views: 14,237
Posted By helisphere

Yes you know, I was at the RHC safety course in...

Yes you know, I was at the RHC safety course in june of 2007 and I was planning to ask this very question but wouldn't you know it, Frank, who was almost always present and teaching at the courses,...
Forum: Rotorheads
21st Dec 2010, 03:05
Replies: 223
Views: 77,020
Posted By helisphere

Blakmax Thanks for all the info, yes, I finally...

Blakmax
Thanks for all the info, yes, I finally read the paper.

So I wanted to clarify a couple things and just make sure I have this right.

1. We are basically talking about adhesion and...
Forum: Rotorheads
21st Dec 2010, 01:24
Replies: 28
Views: 14,237
Posted By helisphere

Well thats ok, I'm not sure my logic is...

Well thats ok, I'm not sure my logic is completely correct but what I meant by resonant was that the natural flapping and rotational frequencies were equal, 1:1, and that the delta 3 altered the...
Forum: Rotorheads
20th Dec 2010, 05:21
Replies: 223
Views: 77,020
Posted By helisphere

So when an aircraft goes down from a...

So when an aircraft goes down from a delamination/debonding blade, can this be difficult to tell whether the delamination was actually the cause? I just wonder about some of these accidents that are...
Forum: Rotorheads
20th Dec 2010, 00:41
Replies: 10
Views: 6,236
Posted By helisphere

I can see the point of not wanting to routinely...

I can see the point of not wanting to routinely drop loads but I don't see any serious danger if proper equipment is being used and I certainly don't see the potential for low g as some are...
Forum: Rotorheads
19th Dec 2010, 23:21
Replies: 35
Views: 5,940
Posted By helisphere

I think it prudent to add that any pilot using...

I think it prudent to add that any pilot using these techniques should consider the type of rotor system on the particular aircraft they are flying. For example a standard semi-rigid rotor like most...
Forum: Rotorheads
19th Dec 2010, 22:35
Replies: 28
Views: 14,237
Posted By helisphere

I understand that the delta hinge acts like a...

I understand that the delta hinge acts like a flapping spring by creating an aerodynamic force on the blade proportional to the flapping angle thereby altering the flapping frequency away from the...
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