Guimbal Cabri G2
What I can't understand is why them fenestron manufacturers, after witnessing early Gazelle issues, did not develop a mechanical cam-disk-correlator thingy that translates classical TR-type pedal travel into travel needed by a fenestron, to have exactly the same characteristics as the good ol' TR.
The S-300C pitch-throttle correlator definitely is not a linear thing, hence adapting TR pedal output into adequate fenestron control input can't be rocket science and would have greatly helped acceptance of the fenestron.
I've even see some airbus graphics of pedal travel over anti-torque trust, comparing TR with fenestron, so everyone should know how the translation ought be designed to make a fenestron feel indiscernible from a TR.
The S-300C pitch-throttle correlator definitely is not a linear thing, hence adapting TR pedal output into adequate fenestron control input can't be rocket science and would have greatly helped acceptance of the fenestron.
I've even see some airbus graphics of pedal travel over anti-torque trust, comparing TR with fenestron, so everyone should know how the translation ought be designed to make a fenestron feel indiscernible from a TR.
Crab has it spot on. Nothing wrong with the fenestron per say( only ever used on a 341/2) The issue is the student, until he learns to anticipate and you can only do that by reaction until the eye/hand / foot coordination kicks in and you can anticipate. This means the instructor really needs to be on the ball to ensure the student is " leading " with the pedal.
Lets be honest all helicopters have there foibles
R22 lots of
S300 not many
B206 slow to react tail rotor
MD 500 massive pedal movements and heavy controls
AS 350 , nose appears pressed against the windscreen
MD520 you think a fenstron is slow to react just wait and have a go with one of these girls
SA341 exciting doing spot turns in a very strong wind
Just to name a few
I think the article seems ok, just pointing out the obvious
Lets be honest all helicopters have there foibles
R22 lots of
S300 not many
B206 slow to react tail rotor
MD 500 massive pedal movements and heavy controls
AS 350 , nose appears pressed against the windscreen
MD520 you think a fenstron is slow to react just wait and have a go with one of these girls
SA341 exciting doing spot turns in a very strong wind
Just to name a few
I think the article seems ok, just pointing out the obvious
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I regularly fly the G2 and R44 back to back and never found this to be an issue. I agree the R44 has more TR authority with smaller inputs required compared to the G2. I was taught on the G2 so this maybe a contributing factor to why the switch between the two is a non event. It seems the incidents are with experienced Robbie instructors who have limited experience on the G2. If you have been trained correctly and are aware of the 'gotchas' on both variants of TR authority, the risk of an incident should be low.
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Fenestron Stall
Originally Posted by [email protected]
Actually I thought the article was very fair and the authour went to great lengths to make it equitable.
As a long-time user of fenestrons on Gazelle and AS 365 (instructing on both) there is definitely a different feel to one over a conventional TR but both work equally well - just requiring s subtly different technique.
It sounds like the GA (H) community are revisiting what was referred to as Fenestron Stall in the UK Military 30 years ago on the Gazelle - it was lack of sufficient right pedal then and it seems to be the same now on the Cabri.
Think of it like Nr control in auto - a small input made pre-emptively avoids a larger input required reactively - just a question of anticipation.
As a long-time user of fenestrons on Gazelle and AS 365 (instructing on both) there is definitely a different feel to one over a conventional TR but both work equally well - just requiring s subtly different technique.
It sounds like the GA (H) community are revisiting what was referred to as Fenestron Stall in the UK Military 30 years ago on the Gazelle - it was lack of sufficient right pedal then and it seems to be the same now on the Cabri.
Think of it like Nr control in auto - a small input made pre-emptively avoids a larger input required reactively - just a question of anticipation.
It was demonstrated by Aerospatiale at that time that it was always possible to stop a yaw rate. The Ministry of Defence issued the Advance Information Leaflet 1/93, quoted in an AAIB accident analysis (Westland Gazelle HT-Mk3 G-BXZE, AAIB Bulletin 1/2002) : "In light wind conditions, an extremely rapid build-up of yaw rate can follow a relatively small left pedal application during low speed flight or in the hover, particularly with the ASE disengaged. In this event, immediate and positive application of right pedal, up to the maximum, should be applied and maintained to arrest the rate of yaw. Recovery action may be ineffective if the pedals are returned only to the hover position, and the yaw rate may initially continue to increase before deceleration and an eventual steady hover is established. Furthermore, if the pedals are not returned as far as the original hover position, a steady hover will never be achieved and the aircraft will stabilise at a particular rate of yaw which may be very high. Pilots may misinterpret this as a loss of yaw control. Be warned that any delay in applying corrective action will require progressively larger right pedal inputs to achieve a steady state hover and may lead the pilot to believe that he has lost control. Yaw rates of up to 165° per second to the left can rapidly be arrested by applying full right pedal without any discernable loss of fenestron performance. In the hover and at low forward speeds, ensure that pedal turns to the left are always made slowly and smoothly."
Unanticipated yaw problems do not come from missing pedal, but from not using the available pedal.
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Between the Gazelle and the Cabri, around 4500 EC120, EC130, EC135, H145, AS365 and EC155 have been produced with a Fenestron and are flying well when the training has been made correctly.
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Between the Gazelle and the Cabri, around 4500 EC120, EC130, EC135, H145, AS365 and EC155 have been produced with a Fenestron and are flying well when the training has been made correctly.
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It’s like driving in different countries with left/right lane traffic. It feel weird only in the beginning. If you regularly switch between those worlds it becomes a non event.
That said, I admit to not having an explanation for the reported Fenestron authority failures.
I'm so disillusioned now.
I always thought that was a misquote and it was really, "If you can survive the R22, you can fly anything...". Although like I say, the vast majority of my hours are in the R22 and I really enjoyed it so I have nothing to grumble about or axe to grind in the slightest. The R22 just feels so dated now by comparison to the Cabri (no shock there, I know).
Unanticipated yaw problems do not come from missing pedal, but from not using the available pedal.
I was instructing on the Gazelle in those days and most of us thought the idea of a 'stall' was rubbish - and so we were proved right when Aerospatiale showed the video of their TP recovering from very high rates of left yaw by using maximum right pedal.
One of the reasons for the reluctance of pilots to use enough right pedal early enough was the torque spikes that occur from rapid right pedal inputs, easily enough to get the torquemeter red light flashing - this was very evident in the Aerospatiale video!
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Originally Posted by [email protected]
I'm pretty sure that is essentially what I posted.
I was instructing on the Gazelle in those days and most of us thought the idea of a 'stall' was rubbish - and so we were proved right when Aerospatiale showed the video of their TP recovering from very high rates of left yaw by using maximum right pedal.
One of the reasons for the reluctance of pilots to use enough right pedal early enough was the torque spikes that occur from rapid right pedal inputs, easily enough to get the torquemeter red light flashing - this was very evident in the Aerospatiale video!
I was instructing on the Gazelle in those days and most of us thought the idea of a 'stall' was rubbish - and so we were proved right when Aerospatiale showed the video of their TP recovering from very high rates of left yaw by using maximum right pedal.
One of the reasons for the reluctance of pilots to use enough right pedal early enough was the torque spikes that occur from rapid right pedal inputs, easily enough to get the torquemeter red light flashing - this was very evident in the Aerospatiale video!
Then it would need hydraulics
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Back to the subject. There is still nothing wrong with the fenestron. It‘s the guy on the pedals causing the problem (or the unexperienced instructor next to him).
