EC135 tail rotor authority
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EC135 tail rotor authority
I had a conversation with a lighthouse bo105 pilot last week and he queried of me whether I had a view regarding the effectiveness of the tail rotor on the proposed EC135 replacements. It was mentioned that in certain lighthouse locations tail authority is critical, and to have plenty of it. I was unable to answer the question, and just said I had'nt heard it was a problem. Any EC135 drivers able to comment or inform me? We are talking about situations offshore where the wind is considerable and likely to shift in moments. Any comments would be gratefully received.
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When I flew the EC-135 in 1995, part way through the flight, the safety pilot brought me back to reality when he said something along the lines of 'not bad tail rotor control for a fenestron'. Up to that point I had not even thought about it as a fenstron - I don't think there's a problem with tail rotor authority in this machine. You'll probably not even notice it's not a tail rotor in the pure sense of the word.
I've been flying it for the last year and i have never got close to loosing TR authority. However you have to be careful with sidewind during hovering. Fenestron is somewhat less sensitive to wind gusting due to higher airflow velocity but the fenestron takes a lot of tail surface. 135 just does't like the crosswind from the right. Keeping the wind on your left solves the problem.
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i have about 1300 hours on 135s, never noticed any lack of tail rotor authority. ECD issued a pilot circular following an enquiry about LTE in fenestron helis, they maintained that if you have what you perceive to be loss of tail rotor effectiveness that full pedal input (to stop) will rectify the situation. Other than that im not sure what the b0-105 driver was referring to. Then again im no test pilot, seems like a question for those guys 'pushing the envelope'!!
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Obviously, it depends on what you are doing and where you are doing it, but in 7 or 8 years of EC135 flying in various roles, I have always found there was a reserve of TR authority. Lots of out of wind OGE hover and similar that would challenge some other types.
I suppose that the body of the fenestron might possibly cause an obstruction to flow in some situations, but I have never noticed anything.
I suppose that the body of the fenestron might possibly cause an obstruction to flow in some situations, but I have never noticed anything.
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The bo105 driver specifically mentioned the kinds of abrupt changes and strength in wind encountered offshore, (lighthouse releif/supply) and noted that on occasions in the bo105 he had down the years encountered gusts the bo105 coped with well. He had never flown a 135 but was simply wondering (or worrying) as to whether it would compare. He mentioned that the area of the fenestron fan seemed small compared with the relatively small tail rotors of the bo105.
Never having flown it either I wondered too as it is going to replace the bo105's.
I note the comments from guys who have flown it, but has your flying been in the sort of conditions encountered offshore?
Never having flown it either I wondered too as it is going to replace the bo105's.
I note the comments from guys who have flown it, but has your flying been in the sort of conditions encountered offshore?
Sounds like we're back to the Fenestron Stall arguments about the Gazelle
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Tail Rotor effectiveness
I have always found wind conditions offshore to be pretty steady (direction wise)regardless of strength as compared to urban or in locations where mechanical turbulence is a risk. Offshore, even in winds up to 55kts control is not a problem (assuming you are landing into wind) Biggest problem is passengers not getting blown off the pad!!
Fenestroms, like notars will always be 'mushy' compared to standard designs. As with any helicopter it only gets interesting when you try to hold it against the wind. (never a good idea in many ways) If for some reason you are obliged to just abide by the RFM and avoid the problem quarters where airframe/ M/R downwash can make life interesting, Test pilots have gone to a lot of effort so you dont need to.
Fenestroms, like notars will always be 'mushy' compared to standard designs. As with any helicopter it only gets interesting when you try to hold it against the wind. (never a good idea in many ways) If for some reason you are obliged to just abide by the RFM and avoid the problem quarters where airframe/ M/R downwash can make life interesting, Test pilots have gone to a lot of effort so you dont need to.
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Ive generally found the 135 to have good handling qualities all round,in high oge hover , out of wind , lighthouses , mountains ( not all at the same time ). As per the manual if you do have a problem apply a bootload of pedal and maintain till the spinning around stops.
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Sounds like we're back to the Fenestron Stall arguments about the Gazelle
...or there again ???
Never had a problem with Tail Rotor Authority of EC 135 T1 or T2 in the 6 years I have been flying it. It would be interesting to hear from the ECD test pilots that have flown some of the more interesting profiles though.
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Having flown a number of fans, Eurocopter and not, it is my belief that there is no such thing as "fenestron stall" as a phenomenon unique to fans. The fan on the older Gazelles was too small and had too little thrust. It didn't stall, it just didn't have enough poop in some situations. It was fixed by changing it to add more max thrust.
The Comanche and S76 Fantail demonstrator could fly at 80 knots sideward, and point independent of the direction of travel up to well over 100 knots. No fenestron stall there. Or better yet, "it flew pretty well, for a fenestron".
I would bet the comments of the experienced 135 drivers below ("flew for 8 years and never touched the pedal stops") tell the story, build a tail with enough thrust, and you will have no problems.
The Comanche and S76 Fantail demonstrator could fly at 80 knots sideward, and point independent of the direction of travel up to well over 100 knots. No fenestron stall there. Or better yet, "it flew pretty well, for a fenestron".
I would bet the comments of the experienced 135 drivers below ("flew for 8 years and never touched the pedal stops") tell the story, build a tail with enough thrust, and you will have no problems.
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Thank you for all iof the responses above. I am reading it that concerns about the 135 fenestron are largely just something that afflicts the inexperienced such as myself. many thanks!
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Blenderpilot, your input is interesting. Could you tell us of your experience of this happening, what altitude and weight? How did it manifest itself and how did you recover?
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BP said: If you are going to have problems with TR authority it will be at the higher altitudes with high weight, it will happen.
EB said: Blenderpilot, your input is interesting. Could you tell us of your experience of this happening, what altitude and weight? How did it manifest itself and how did you recover?
Just when I thought I had it all pushed into a nice pile in the corner……. I’m out here in the high desert of New Mexico USA flying an Astar B3. A machine I consider having a pretty powerful tail rotor. Then one night……..
One of our pilots was coming out of the scene a few percent under gross, maybe 6500’ MSL and 50-60F, a slight breeze of a headwind as registered on the ground, hand full of collective, low airspeed and takes a right turn home. At about 200’ AGL and 90 degrees into the turn, they proceed to spin a couple times against full right pedal before he gets it sorted out. I can only imagine what it would have looked like without NVGs.
More forceful left crosswind at altitude? Bad choice of turn direction? Not enough airspeed? Probably a little of all of them.
I’m in agreement with Blender. If you’re not careful, sooner or later she comes home.
EB said: Blenderpilot, your input is interesting. Could you tell us of your experience of this happening, what altitude and weight? How did it manifest itself and how did you recover?
Just when I thought I had it all pushed into a nice pile in the corner……. I’m out here in the high desert of New Mexico USA flying an Astar B3. A machine I consider having a pretty powerful tail rotor. Then one night……..
One of our pilots was coming out of the scene a few percent under gross, maybe 6500’ MSL and 50-60F, a slight breeze of a headwind as registered on the ground, hand full of collective, low airspeed and takes a right turn home. At about 200’ AGL and 90 degrees into the turn, they proceed to spin a couple times against full right pedal before he gets it sorted out. I can only imagine what it would have looked like without NVGs.
More forceful left crosswind at altitude? Bad choice of turn direction? Not enough airspeed? Probably a little of all of them.
I’m in agreement with Blender. If you’re not careful, sooner or later she comes home.
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Did the pilot report this? NASA's ASRS is an ideal place to let this get known.
And if we don't report stuff like this, nothing will ever be known about it, and nothing will ever get done about it (and the something that might get done about it could be as simple as training and awareness....)
Did the pilot report this? NASA's ASRS is an ideal place to let this get known.
And if we don't report stuff like this, nothing will ever be known about it, and nothing will ever get done about it (and the something that might get done about it could be as simple as training and awareness....)