The inflow is small, because the space between the ceiling and the disc is small, air will want to fill this low presure area (above the disc)from the side, giving translational lift, in turn, reduced power.

Ding Dong

Given nil wind, and the helicopter stationary at the ceiling, where is this "translational lift" coming from?

noblades

"Less angle of attack, therefore less power required": Surely it is a greater angle of attack and reduced induced flow vector and drag due to the presence of the ceiling surface?

TT

Reduced induced flow=reduced induced drag=reduced power requirement. Same as an IGE hover. Only instead of below the rotor, you have a surface above the rotor limiting the tip path vortices as well as limiting induced flow. I would also have to say that there is some translational flow going on helping to reduce the power requirements. My two cents or euros or pfennigs or won or yen or francs; all depending on what part of the world you hail from. MAC

My son bought one of these helos in California and tools around his apartment with it. I asked him to try the ceiling-effect maneuver and report his experience. He said that there was no apparent ceiling-effect at all, even under close scrutiny. His was a small, coaxial helo with two side props for thrust/yaw control. I will get a model number from him.

In the interest of truly scientific prattling around, can we get a report from each of the pprune model flyers as to who has tried the close to ceiling power check, what type of helo, what ceiling proximity and what were the power observations?

theory B
 

My little Bell 47 lookalike is big enough to chip spikes off the artexed ceiling, increasing the mass thrown downwards.

Additionally, small black pieces of rotor disk are part of a dynamic weight reduction exercise, increasing power to weight ratio ...

... off to re-decorate before 'er indoors finds out ...

Okay,

Let me perhaps throw in the first set of figures.

The model is a small schweizer 300, 5" rotor blade with small sperate electric motors controlling main and tail rotors. I have no idea what speeds the rotors are spooling around at but the observations are as follows.

The little craft flys round my living room describing approximately an 8 foot circular track with a fixed rpm setting. Depending how accurately I can make the thing fly it climbs maybe 6 to 8" per orbit. It can do this from nearly ground level. However at approximately 8 to 12" from the ceiling the climb becomes far more pronounced with no unaltered power setting. It literally starts to accelerate toward the ceiling.

A reduction in the power (rpm) setting (unquantifiable... sorry) seems to have no effect in retarding this increasing rate of climb in the orbit. Unless I apply a very large reduction in rpm the craft eventually starts to brush the rotor hub against the ceiling. After maybe a full circle or two like this with the rotors eventually crashing against the ceiling I reduce sufficient rpm that the craft falls away from the ceiling but is unrecoverable and seems in my limited knowledge to be in vortex ring state i.e. even if full rpm is then applied the craft falls to the ground unable to regain lift.

Unfortunately Mrs R1 is away for the evening otherwise I'd have her video it and see if I couldn't post it some where for you to view. I can't fly and video closely enough at the same time. I'll try and get some footage in the next day or two.

R1Tamer

My 'research'
 

As a former unmanned VTOL professional pilot, I decided to brush off the old 'skills' and get some video.
Not much in the way of instrumentation. But here is what I found. The single rotor air-hog, I think the same thing as a picco-z, does not seem to show a lot of ICE:
http://i198.photobucket.com/albums/a...h_DSCN0721.jpg
The dual rotor Saber Strike, which has no flybar and puts the rotor verrry close to the ceiling, exhibits extreme ICE:
http://i198.photobucket.com/albums/a...h_DSCN0723.jpg
I certify that no 6-year olds were injured in the filming of this scientific experiment.
-- IFMU

IFMU, any likelyhood then that tail rotor upsets ICE?

Other thought: Inflow could be affected by ceiling to set up conditions for VRS, same way as being close to a wall does. The Saber Strike has one rotor operating away from ceiling, so VRS does not affect ICE. Air-hog rotor gets into VRS so ceiling effect is reduced.

Help!
 

After one too many 'carrier' landings mine has developed a severe lack of tail rotor power. I've installed the spare but it's still not producing enough thrust and the slightest touch on the throttle sends the thing spinning away under the sofa. My four year old is getting mighty pissed off at being sent under to retrieve it (muttered comments about Victorian chimney sweeps and Childline).
Anyone any ideas to solve this? May be something to do with the trim control but I have no idea how it works.
Long winter shifts on standby way too far north beckon and I need a solution!
Yours in desperation,
Trolleys
ps Solutions other than 'Buy a new one!'. I'm saving for a proper toy!

Mart,

I don't think so. There is a little flybar rotor, maybe 40% of the diameter is the main rotor, which stands the main rotor away from the ceiling. This flybar rotor isn't doing squat for producing lift, the tip speeds are way too low I think. The saber strike has no flybar, I think it uses magic for stabilization. Or maybe there is a cat with buttered toast strapped on its back, suitably miniaturized, inside. With no flybar the blades can get nice n close to the ceiling.

Ours do that sometimes. Hover it and use the trim until it stops spinning. Be patient, it takes a while. Also, I'm sure you have pulled the t/r off and removed the cat hair/ect.

-- IFMU

IFMU, just reread your scientific experiment post. I get it, so ICE only works when hovering very close to ceiling.

This makes sense, since inflow is ingested from all directions while downwash goes... well... down. This means that IGE easilly affects hover power, while ICE has a very weak affect. Same reason tail rotors are usually pushers instead of pullers (since vert stab counters tail rotor). Trouble is ingesting turbulent air makes for a noisier tail rotor - i suspect ICE makes a lot more rotor noise than IGE too.

I couldn't hear any more tail rotor noise. The main rotor was a lot noiser as it was trying to plane down the ceiling.

-- IFMU

Electric trim
 

Hey Trolley there are electric trim buttons located under the TR control. You press the buttons down to establish 'balance' then fly the actual control lever. A lot like a real H300/MD500.;)

just wondering if there is any effect if, when in "ice", you get it near a wall aswell..... :rolleyes::ugh:

simfly, although a rotor downwash goes straight down the inflow comes from all directions. Ever seen a bell mouth inlet? Same thing. If you put a wall nearby the inflow starts to pull the downwash back upwards, until eventually recirculation happens. The odd result is that lift can be lost near a wall, so i imagine ICE would also be reduced.

Ok, now I'm lost. What joke?

-- IFMU

IFMU,

By "plane" i thought you meant as in knocking off all the little ceiling features - i wrote a serious response, then realised you might be commenting about how close you needed to get for ICE. Doh! :\

Main rotor will be noisier, since it is ingesting air that has flowed across the ceiling. The ceiling features will cause small scale turbulence, so that the rotor is not running in clean air. Normally the boundary layer seperation begins to occur at the rear of the airfoil (adverse pressure gradient for flow direction), but this ingested turbulents trips it sooner. The noise is the result of the small random changes in the downwash velocity becoming very small pressure variations (flow is only approximately incompressible).

Pusher tail rotors will make more noise as they pass into the vert stab shadow, because they are seeing sudden changes in flow. Coaxials and pusher props have the same problems. Coaxial because the lower blades are seeing sudden AOA changes and pushers because they are ingesting the turbulent layer from the fuselage.

Just wondering....does the texture of the ceiling have any effect on ICE?!!!:}

for the attention of mr lappos,

my own bad science observations with the Picoo Z, as pictured at the start of this thread, ICE was very noticeable and quite strong if I look at this in terms of throttle travel as a percentage from full off to full on.

1.the rotors do not turn at all on mine until about 20% travel at which they turn rapidly
2. it takes about 70% travel to get it to the ceiling
3. ICE kicks in and it bumps against ceiling, throttle needs to be reduced to about 50% to get it to break the ICE, at which point it descends rapidly

what does this prove ? with this helo ICE seems stronger than ground effect to me.

I would presume a textured ceiling would reduce ICE, but I dunno mine isnt :(

however you look at it, it is a design miracle, you can even see it sits right skid low in the hover (clockwise rotor)

regards

CF

That is exactly what I meant. There is no more aero noise from the rotor, which are nearly silent anyway. Primary noise from them little buggers is motors/gears. When planing down the ceiling features, you can't hear the motors/gears anymore as they are masked by whacking the ceiling.

-- IFMU