C17LM Posted October 3, 2007 Posted October 3, 2007 I have searched the forum and couldn't find much on this topic. My question is: What are the pros and cons of the fenestron vs. Traditional Tail Rotor Systems? Just curious and trying to learn as much as possible. Thanks in advance! Quote
apiaguy Posted October 3, 2007 Posted October 3, 2007 Fenestron pros:More efficient than traditional t/rnot sticking out there ready to chop someone Fenestron cons:more complexmore expensive I'll get out Ray Prouty's aerodynamics book and try and add some more but those are the basics. Quote
kodoz Posted October 3, 2007 Posted October 3, 2007 Fenestron pros:More efficient than traditional t/rnot sticking out there ready to chop someone Fenestron cons:more complexmore expensive I'll get out Ray Prouty's aerodynamics book and try and add some more but those are the basics. Doesn't the fenestron increase stability in flight (the housing acts as a vertical stabilizer), but in a crosswind landing requires more power and control inputs to maintain stability? Quote
apiaguy Posted October 3, 2007 Posted October 3, 2007 Doesn't the fenestron increase stability in flight (the housing acts as a vertical stabilizer), but in a crosswind landing requires more power and control inputs to maintain stability? Well, yes, that would be true of some of the existing fenestron designs that have a large vertical tail associated with it. You could design one that did not have as much of a problem with it.... just depends on your overall mission profile of the aircraft... Quote
rmiller4292 Posted October 5, 2007 Posted October 5, 2007 Well, yes, that would be true of some of the existing fenestron designs that have a large vertical tail associated with it. You could design one that did not have as much of a problem with it.... just depends on your overall mission profile of the aircraft... The fenestron is also much quieter than traditional T/R systems, lots of authority too! Quote
apiaguy Posted October 5, 2007 Posted October 5, 2007 ok. From Prouty's helicopter aerodynamics: The fenestron pros: Performance benefit, the duct around the fan helps produce a low static pressure that adds to the force being generated by the fan.Fenestron can produce the same total thrust for the same power as a tail rotor 30% larger, also by making the exit of the fan a bit divergent helps to expand the wake and the fenestron has no supporting fin blockage.Because of this the fenestron can be up to 50% smaller than the tail rotor it is replacing (side note).... up to now Eurocopter has been using even smaller fans on the Gazelle and Dauphin designs.. Thus, they use more power which could be used by the main rotor. Safety as previously noted. Cons: To be effective the depth of the duct should be at least 20% of the fan diameter so it is difficult to streamline the thick fan for low drag in forward flight. It also means that the airpath into and out of the fan is tortous (curved and twisted), so its efficiency is penalized. This is why the fenestron is always integrated into a generously sized cambered vertical stabilizer that can take over the job of torque compensation in forward flight. Quote
500pilot Posted October 6, 2007 Posted October 6, 2007 Fly an EC-130. T/R authority sucks especially with a crosswind or tailwind. An Astar has much better authority even compared to the Dauphin. IT may look cool but when it comes to business I prefer the real deal. TOf the three Fennestrom sircraft I have flown and have decent time in ( EC-120, EC-130, Dauphin) I have found tthat the best T/R authority of the three is the EC-120 and that thing is very underpowered as it is that it doesnt have much else. Quote
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