Static and Grass Pollen
Joined: Apr 2000
Aviation Qualifications: ATP+Mil
Posts: 10,959
Likes: 1,814
From: EGDC
Tam is that you? How is the business going?
Nick Lappos will certainly not be happy with your use of the phrase 'building a ground cushion' as it is one of the urban myths he has debunked on these very pages.
The phrase cellular absorption implies the grass cells absorb the energy from the moving downwash - this would slow the air and produce a higher pressure under the disc - according to the CFS teaching this would work to improve the ground cushion.
Personally I think that long grass gives the beginnings of recirculation but that's as technical as I get on it too.
Nick Lappos will certainly not be happy with your use of the phrase 'building a ground cushion' as it is one of the urban myths he has debunked on these very pages.
The phrase cellular absorption implies the grass cells absorb the energy from the moving downwash - this would slow the air and produce a higher pressure under the disc - according to the CFS teaching this would work to improve the ground cushion.
Personally I think that long grass gives the beginnings of recirculation but that's as technical as I get on it too.
Joined: Jun 2002
Posts: 326
Likes: 2
From: Florida/Sandbox/UK
Yep its me matey, doing fine thanks.
"Building a ground cushion" - I can't think of an easier way to graphically describe something that increases or decreases based on hover height.
As I said, I don't know the origin of the term "cellular absorption" however, I would say that I do not consider it applicable only to long grass. I guess it's a more succinct term than "lack of ground cushion due to surface over which you hover".
I wouldn't like to argue the toss but recirculation says to me more power required due to accelerated air coming back through the disk for a second time, third time etc. I do not see this as the case in cellular absorption, I see only that the lack of a ground cushion means the requirement for OGE power.
I like the simpler explanations nowadays, short words, pictures where possible.
"Building a ground cushion" - I can't think of an easier way to graphically describe something that increases or decreases based on hover height.
As I said, I don't know the origin of the term "cellular absorption" however, I would say that I do not consider it applicable only to long grass. I guess it's a more succinct term than "lack of ground cushion due to surface over which you hover".
I wouldn't like to argue the toss but recirculation says to me more power required due to accelerated air coming back through the disk for a second time, third time etc. I do not see this as the case in cellular absorption, I see only that the lack of a ground cushion means the requirement for OGE power.
I like the simpler explanations nowadays, short words, pictures where possible.
Joined: Oct 2005
Posts: 61
Likes: 0
From: New Zealand
Pollen will deffinatly effect lift produced.
I have been in 300 where blades have got coated in a layer of pollen and she has been using a bit of power to hover.
By simply cleaning them and with out changing the weight I have gone back out and used 1 to 2 inches less.
Long grass will effect your cushion but it will not suddenly make it dissapear after hovering in the same place for 20 minutes. If you look at the pollen on the leading edge when it builds up it has about the same dimentions as a good hoar frost.
Anything rough on your leading edge will effect lift thereby increasing the power needed.
I have been in 300 where blades have got coated in a layer of pollen and she has been using a bit of power to hover.
By simply cleaning them and with out changing the weight I have gone back out and used 1 to 2 inches less.
Long grass will effect your cushion but it will not suddenly make it dissapear after hovering in the same place for 20 minutes. If you look at the pollen on the leading edge when it builds up it has about the same dimentions as a good hoar frost.
Anything rough on your leading edge will effect lift thereby increasing the power needed.
