EC135 tail rotor authority
Join Date: Oct 2003
Location: Albuquerque NM USA
Posts: 60
Likes: 0
Received 0 Likes
on
0 Posts
Shawn:
>Did the pilot report this? NASA's ASRS is an ideal place to let this get known.
There was an internal investigation. Incidents such as this are taken seriously by both the aviation and medical sides of PHI and the information is disseminated company-wide, but to my knowledge, that document hasn't been published yet. Beyond that, I don't know.
My take is it was a combination of factors. You will truly be amazed at the varying strength of the wind out here. A flight can be coming in from the west with a 30-40kt tailwind at 1000' AGL. Overfly the hospital and the sock is hanging limp. My personal favorite is typically 25 gusting 35-40 reported from the east at ABQ international and at the hospital 3 miles due north, light and variable.
>Did the pilot report this? NASA's ASRS is an ideal place to let this get known.
There was an internal investigation. Incidents such as this are taken seriously by both the aviation and medical sides of PHI and the information is disseminated company-wide, but to my knowledge, that document hasn't been published yet. Beyond that, I don't know.
My take is it was a combination of factors. You will truly be amazed at the varying strength of the wind out here. A flight can be coming in from the west with a 30-40kt tailwind at 1000' AGL. Overfly the hospital and the sock is hanging limp. My personal favorite is typically 25 gusting 35-40 reported from the east at ABQ international and at the hospital 3 miles due north, light and variable.
Join Date: Jun 2002
Location: Canada
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
In my experience, The EC 135 will hover 90 degrees out of wind up to 35Kts. with little problem. At 35-40 Kts., you wil sometimes reach full pedal with a proportionate reduction in control. At 40-45 kts., control may be lost and you need to quickly dive on speed to regain yaw control. Above 45 kts. it becomes almost impossible to retain control, especially if ther is any gusting.
This can be a bit hairy , so I would recommend plenty of height [ i.e. greater than 800'] if you need to do it. The a/c may yaw through ~130 degrees with you as a passenger
This can be a bit hairy , so I would recommend plenty of height [ i.e. greater than 800'] if you need to do it. The a/c may yaw through ~130 degrees with you as a passenger
Join Date: Dec 2007
Location: upyours
Posts: 294
Likes: 0
Received 0 Likes
on
0 Posts
Nick
I would have thought that not enough thrust to overcome relative airflow through the fan could easily be described as "fenestron stall"
It didn't stall, it just didn't have enough poop in some situations.
I`ve not flown an EC135,so my comments relate to approx. 30 other types that I have flown and tested.All have limitations for certification,military and civil,being either Vne,enginepower/rotor Tq, weight,CofG,SIDEWAYS flight,BACKWARDS,and RATE of YAW. They are usually determined when the amount of control used is within 5-10% of full control authority as determined/set by the manufacturers,to allow a little margin for error. If you use ,as has been said,full yaw,whilst hovering,possibly outside the sideways/x-wind limit,and the a/c about-faces,that is your problem,and you may not have 700ft to play,or pray with!
Not only that,operating consistently outside the limits will put up the amount of power reqd,by the t/r drive shaft ,and gearbox; it may well fail,maybe it will fail with someone else,who may well be flying within limits one day.
Not only that,operating consistently outside the limits will put up the amount of power reqd,by the t/r drive shaft ,and gearbox; it may well fail,maybe it will fail with someone else,who may well be flying within limits one day.
The theory behind 'Fenestron Stall' was that even in the hover, the vertical and heavily cambered area of the tail was producing useful anti-torque lift by virtue of the fact the air was accelerated over the fin on its way to the fenestron. Therefore the fenestron itself wasn't having to work as hard it might if that lift wasn't there. Now introduce a wind from the right (about 10 kts was the quoted figure) that disrupts that flow around the fin and suddenly the fenestron is behind the drag curve, not producing enough thrust to make up for the loss of the fin lift - the yaw to the left starts and what is required is an unusually large right pedal input to cancel the yaw and compensate for the loss of lift from the fin. Most pilots would be reluctant to make such a large yaw input initially and so the yaw rate increases - all the while the selected pitch of the fenestron is less than is actually required because the pilot is having to play catch-up.
The theory was debunked by Aerospatiale because they showed that full right pedal would always stop the yaw, even if it overtorqued the transmission!
Frankly I am surprised the French didn't claim it was designed in like the jackstall due to underpowered main jacks
The theory was debunked by Aerospatiale because they showed that full right pedal would always stop the yaw, even if it overtorqued the transmission!
Frankly I am surprised the French didn't claim it was designed in like the jackstall due to underpowered main jacks
Join Date: Jul 2005
Location: Stuck on 50:30 North
Age: 68
Posts: 42
Likes: 0
Received 0 Likes
on
0 Posts
Intresting thread this! So having flown Bolkows on lighthouse ops and currently flying the 135 I'm going to throw my 2'pennorth worth in.
Flying a 135 to lantern top lighthouses (which are mostly confined to the SW of the country) will be no problem. The wind, regardless of strenght, will be fairly consistant in direction and with 100'+ of open airspace around the tower, a go around is no big deal. The 135 has very good tail authority, copes well in a cross wind and, like others, I've never got near the stops.
HOWEVER, I do take issue with those that say "just put in a bootfull of pedal". At high AUW and low speed/hover, the 135's fenestron eats huge amounts of power. If at a high Tq setting you put in a bootful of left pedal you WILL overtorque (very rapidly). Most 135 pilots have had the Tq limit 'BONG', (or is that just me?). OK with consistant wind if you are aware of the possibility. The problem will come with rock station or headland lighthouses. Where the winds can vary by topography + /- 20+ knots and + or - 90+ degrees. The fin would react to the wind and corrective action could or most likely would, result in a Tq limit.
Sorry! Banging on a bit here. So, in a nutshell, and to answer the original question, the 135 would be a very capable replacement for the Bolkow for lighthouse ops. However, in certain conditions it could well be more limiting.
Does ANYBODY know how to fly this thing?
Flying a 135 to lantern top lighthouses (which are mostly confined to the SW of the country) will be no problem. The wind, regardless of strenght, will be fairly consistant in direction and with 100'+ of open airspace around the tower, a go around is no big deal. The 135 has very good tail authority, copes well in a cross wind and, like others, I've never got near the stops.
HOWEVER, I do take issue with those that say "just put in a bootfull of pedal". At high AUW and low speed/hover, the 135's fenestron eats huge amounts of power. If at a high Tq setting you put in a bootful of left pedal you WILL overtorque (very rapidly). Most 135 pilots have had the Tq limit 'BONG', (or is that just me?). OK with consistant wind if you are aware of the possibility. The problem will come with rock station or headland lighthouses. Where the winds can vary by topography + /- 20+ knots and + or - 90+ degrees. The fin would react to the wind and corrective action could or most likely would, result in a Tq limit.
Sorry! Banging on a bit here. So, in a nutshell, and to answer the original question, the 135 would be a very capable replacement for the Bolkow for lighthouse ops. However, in certain conditions it could well be more limiting.
Does ANYBODY know how to fly this thing?
Join Date: Oct 2007
Location: europe
Posts: 85
Likes: 0
Received 0 Likes
on
0 Posts
Previous comments of bootfulls of pedals are an obvious generalisation but are for the most part correct. The majority of the flying i do in the 135 is in OGE hovers at MAUW in windy/turbulent/gusty conditions, we often operate in crosswind hovers with plenty of spot turns etc and i have never experienced any condition where a 'bootfull' does not remedy the situation. If at MAUW, a bootfull may induce the bong (indicating you are in excess of 10 FLI, however you may pull a transient 10.5 FLI before maintenance inspection is required). Never have i reached the pedal stop either. As ECD published, pilots should be wary when operating close to the ground at low airspeed while turning right into the wind, however the pilot notice did say that if loss of tail rotor authrity is suspected to apply pedal to the stop and this will remedy the situation, if it means overtorqueing the machine in the process of saving the airframe, so be it. I think talk of fenestron ineffectiveness is giving some people unfamiliar with the machine a bad impression of it. My experience of the 135 has been very positive in comparison to other helis, if only they sorted out those damn ARIS pots (thats another thread!) other than that they are an example of excellent german engineering!!!!
Join Date: Sep 2000
Location: UK
Age: 47
Posts: 1,595
Likes: 0
Received 0 Likes
on
0 Posts
Just remembered have a word with Rotordompteur who posts on here he flies the 135 amongst the windturbines offshore Holland he should know about windy conditions and tail authority.
