View Full Version : Fenestron and LTE
tartare
3rd Mar 2011, 00:48
Guys - a question r/e LTE.
Understand that fenestrons have certain advantages over traditional tail rotors.
Is a machine with a fenestron more or less succeptable to conditions that cause loss of tail-rotor-effectiveness in a machine with a conventional tail rotor?
Ascend Charlie
3rd Mar 2011, 01:26
LTE = old B206 with small tail rotor.
Fenestrons have their own quirks, but LTE isn't one of them.
Vertical Freedom
3rd Mar 2011, 02:44
What quirks do the fenestrons have? :confused:
Savoia
3rd Mar 2011, 04:57
.
From what I understand:
Advantages
- Increased safety during grounds ops
- Increased protection from FOD
- Reduced t/r vibration
- Reduced t/r noise
Disadvantages
- Higher weight and drag of t/r section
- Higher construction cost
- Higher power requirement for given thrust
- The 'alleged' Fenestron (also Fenstron) stall
See also:
Fenestron stall - Fact or Myth? (http://www.pprune.org/rotorheads/20002-fenestron-stall-fact-myth.html)
http://www.aaib.gov.uk/cms_resources.cfm?file=/dft_avsafety_pdf_500862.pdf
S.
Advantages
- Increased safety during grounds ops
- Increased protection from FOD
- Reduced t/r vibration
- Reduced t/r noise
- Reduced power requirement in the cruise
- "Branding" for the manufacturer - even MD pay licence money for the NOTAR fan
Disadvantages
- Higher weight and drag of t/r section
- Higher construction cost
- Higher power requirement for given thrust
- The 'alleged' Fenestron (also Fenstron) stall
- Higher maintenance cost - Additional maintenance time required, i.e 10 blades,10 strap packs, 10 ......................
- It will not "scale"
- The blanketing effect of the vertical stabiliser can be annoying as you are trying to get that tracking shot as described but you soon learn to fly "around" it.
I think the biggest one is the safety issue on the ground.
The later versions are a little more refined and very powerful
Frenchrotorhead
3rd Mar 2011, 07:31
I speak with little experience, I have flown only the AS 350 and EC 120 to compare fenestron and conventional TR.
I had an instructor who agreed to let me try out VRS with both types (from 10.000 AGL), which seems very difficult to get in to when you are trying, by the way.
In late stages of VRS, while I kept pulling more power and rate of descent increased, the EC 120 showed LTE.
Fenestron masking in VRS means that the airflow does not go through the hole.
Phil
Kulwin Park
3rd Mar 2011, 11:24
What is VRS??
bolkow
3rd Mar 2011, 11:27
saw a programme on mythbusters that is somewhat related, creating a strap on flying pack using a fenestron fan. What was interesting was they discovered that the lift greatly increased the less tolerance there was between the tips of the blades and the sourrounding enclosure. The tolerance was mega fine in the end.
Bravo73
3rd Mar 2011, 12:01
What is VRS??
Vortex Ring State
Savoia
3rd Mar 2011, 12:14
.
Kulwin: Are you the same 'Park' who flew 205/212 with Rotorwork (which became HeviLift) ex-Mt.Hagen PNG circa 1988/9?
S.
darrenphughes
3rd Mar 2011, 20:46
Less Tail authority is another problem. We used to have EC130s for tours in NYC and while landing at W30th heliport with a strong tail wind in the AS350 was never an issue, the 130 had major problems with it. We don't have them any more partially due to that reason from what I'm told.
I guess the Vegas or Hawaii guys could chime in on that one cause they're still using them.
bolkow
4th Mar 2011, 08:08
I recall posting the same question about tail rotor authority some time back with regard to ec135's, Sean Coyle took up the topic and I can say that he was absolutely right, no issue at all and a huge improvement over the bolkow which itself is good.
darrenphughes
4th Mar 2011, 20:56
The 135's fenestron is bigger comparable to the size of the machine than the 130's.
Frenchrotorhead
6th Mar 2011, 20:24
EC 135
MR diam : 10.20m (4 blades)
TR diam : 1.00m (10 blades)
Max Gross : 2910 Kg
EC 130
MR diam : 10.69m (3 blades)
TR diam : 1,00m (10 blades)
Max gross : 2400 Kg
Sure, one has to take into account other factors like main blade chord, distance between fenestron and MR mast (leverage effect), probably the Rpm's of all those rotors, but do these machines actually have the same fenestron for a 500 Kg Max gross weight difference ?