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Pages: 1 2


TF/ETL - FlyGuy - 07-14-2015

Howdy Gang,
 
I have been working with my 285 and loving it, but I noticed there is a profound difference from my training in a 300 cbi and my 285. When training I am instructed to move the cyclic forward and let the aircraft build speed. You look around and maybe adjust the position in your seat and wait for climb speed. There is a very, very slight vibration (getting through transverse flow and effective transitional lift), you see the airspeed build, the aircraft gets to climb speed, ease back on the stick, and off you go.
 
In my 285 I ease the cyclic forward and very shortly feel a vibration that seems to last longer than I would like. I end up backing off and bringing the heli back to a hover. I contacted a few fellow pilots about this issue. One told me that the first time he went through TF/ELT he thought he would have to change his underwear. Another stated “it scared the living hell out of me but over time I don’t even notice it anymore”.
 
I understand that part of the issue is the fact the Mosquito is very light vs. the 300cbi.
The slight vibration with the 300 seems to last a fraction of a second, the vibration on the Mosi seem to last too long. I know part of the reason is when the vibration starts I hesitate to push through it because I have never felt a vibration like that before. Mind you Dwight test flew my heli after I finished it and it flies fine, it’s me.
 
This issue was never mentioned on the forum before. I, and probably other would like to hear stories from you more experienced pilots about your first time going through TF/ELT. I think this will be very educational, fun and helpful to novice Mosquito pilots. I know your stories will be Great!
 
Michael


RE: TF/ETL - mosquito - 07-15-2015

Michael,

  First, you may need to tune your rotor a bit.  There will always be some vibration but properly tuned and balanced, and with a correct 1 deg nose down airframe balance, your vibes should not be excessive.
  A two blade, semi rigid rotor will always create more vibration than a 3 bladed, fully articulated rotor like the Hughes.  3 blades are much smoother than two since you aren't feeling the drag and Hooke's joint effects of two blades fully in line and then fully abreast of the direction of travel.  With 3 blades the projected area variation is much smaller.  Also, a 3 bladed rotor uses the smoother, but much more complicated fully articulated rotor head that absorbs lead lag movement of the blades through shock absorbers.  So that also smooths things out.
 As you become more comfortable with the Mosquito you'll find that you spend very little time in the transitional stage.  Rather than slowly sneak up on transition and then deal with the "blowback" effect when it hits along with the vibration, you simply roll the nose over a little and pull some collective to climb out.  You'll actually feel no transition at all.


RE: TF/ETL - mauri - 07-15-2015

michael,
I started flying with the mosquito, I had the same problem. this strong vibration worried me and I could not accelerate because my first thought was the fact that I had made some mistakes during the assembly. my experience flying on helicopters was on 300 and as you say it is almost nonexistent.
then with congli that I had in the forum and reassurance, I managed to pass this stage. now that I have 100 hours on the mosquito I can tell you that in reality this is not a problem, just know. I can say that the mosquito is a major project well done, perhaps the engine could be improved to make it exceptional.
----------
michael,
quando ho iniziato a volare con il mosquito, ho avuto lo stesso problema. questa forte vibrazione mi preoccupava e non riuscivo ad accellerare perchè il mio primo pensiero era al fatto che avessi commesso qualche errore nella fase di assemblaggio. la mia esperienza di volo su elicotteri era sul 300 e come dici tu è quasi inesistente.
poi con i congli che ho avuto nel forum e rassicurazione, sono riuscito a passare questa fase. ora che ho 100 ore sul mosquito posso dire che in realtà questo non è un problema, basta conoscerlo. posso dire che il mosquito è un grande progetto ben riuscito, forse il motore potrebbe essere migliorato per renderlo eccezzionale.


RE: TF/ETL - cablecar - 07-16-2015

Michael: I waited for more experienced voices to chime in before voicing my experience. I've had exactly the opposite experience to yours. It could well be dumb luck, but I experienced very little vibration going thru ELT.

I balanced the blades & set Lead/Lag twice with a laser before engine run-in.  Both blades had -0.9 deg pitch. There was some house-shake at 3-4,000 rpm, but above 4,000, the ship was rock steady. I have not tracked the blades yet, but hovers were sweet. Last flight I braved some forward flights on the taxiway to 40 mph and ELT was like, "yep, there's ELT" and it was gone in 2 seconds! Haven't gone to altitudes yet but will be home in a week. Can't wait to fly some more! Might get the house-shakes again at cruise airspeed but bless my luck so far - may Never want to fly that fast.

Good luck with your flying!


RE: TF/ETL - FlyGuy - 07-16-2015

(07-16-2015, 04:40 AM)cablecar Wrote: Michael: I waited for more experienced voices to chime in before voicing my experience. I've had exactly the opposite experience to yours. It could well be dumb luck, but I experienced very little vibration going thru ELT.

I balanced the blades & set Lead/Lag twice with a laser before engine run-in.  Both blades had -0.9 deg pitch. There was some house-shake at 3-4,000 rpm, but above 4,000, the ship was rock steady. I have not tracked the blades yet, but hovers were sweet. Last flight I braved some forward flights on the taxiway to 40 mph and ELT was like, "yep, there's ELT" and it was gone in 2 seconds! Haven't gone to altitudes yet but will be home in a week. Can't wait to fly some more! Might get the house-shakes again at cruise airspeed but bless my luck so far - may Never want to fly that fast.

Good luck with your flying!

Andy,

My blades are at -1.0 deg.pitch full down collective. While running up the engine I get the same house-shake between 3-4,000 and it is totally smooth after that. Hovering is very smooth. I have moved to forward flight but get no register on the airspeed. My pitot tube is +1.0 deg. from the level of the main head sprocket as I was instructed. I may try to push a little harder but I hesitate to climb without knowing my speed. I don't want to get into a situation to have to auto and not know my speed. I am taking baby steps and don't want to rush.

I am just curious to here about the experience of others going through this threshold. I think I will feel better once I see the airspeed register. 

Thanks for your input.

Michael


RE: TF/ETL - doug bryant - 07-16-2015

Does your airspeed work?


RE: TF/ETL - FlyGuy - 07-17-2015

(07-16-2015, 06:52 PM)doug bryant Wrote: Does your airspeed work?

Yes it does. It is pretty much because I have not reached transverse flow effect or effective transitional lift.


RE: TF/ETL - doug bryant - 07-17-2015

(07-17-2015, 12:28 AM)FlyGuy Wrote:
(07-16-2015, 06:52 PM)doug bryant Wrote: Does your airspeed work?

Yes it does. It is pretty much because I have not reached transverse flow effect or effective transitional lift.

There should be an indication by that speed.


RE: TF/ETL - FlyGuy - 07-17-2015

Doug,

I spoke to Mark Thompson for about 40 minutes today. He stated once I pass through TF and ETL then I would get airspeed registration. He is sending me an article that I will post for him. He too is having problems getting back on the forum. 

Michael


RE: TF/ETL - doug bryant - 07-17-2015

(07-17-2015, 05:03 AM)FlyGuy Wrote: Doug,

I spoke to Mark Thompson for about 40 minutes today. He stated once I pass through TF and ETL then I would get airspeed registration. He is sending me an article that I will post for him. He too is having problems getting back on the forum. 

Michael

Would be good to know that it comes alive though with some moving air (fan or something).