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Eurocopter crash off Queensland north coast

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Eurocopter crash off Queensland north coast

Old 23rd Jun 2021, 06:18
  #101 (permalink)  
 
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It had potential disaster written all over it, right from the beginning.
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Old 23rd Jun 2021, 12:09
  #102 (permalink)  
 
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Originally Posted by megan View Post
Things are not quite so simple. When you understand the issues facing the pilot you perhaps can understand. His departure from home base required maximum take off power, being so heavy, actually over permissible take off weight, the engine was min spec performance wise, the wind was from the right side, pushing in more right pedal requires more power for the tail rotor/fenestron, power being sent to the tail rotor/fenestron is power that's not available to the main rotor. Forgetting about any performance benefit from the wind he, more than likely, would have had his hands full trying to keep the engine within limits. Just my guess. The pilot commented that he was "busy", a sign that he was anxious/concerned/up tight/in full knowledge he was facing a difficult approach perhaps.
Good points.
Accepted.
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Old 24th Jun 2021, 07:49
  #103 (permalink)  
 
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He had a wind from the right which helps in a right power pedal aircraft. = stable so far

He planned to yaw left to align with the pontoon putting the wind further round. = reduction in right pedal to yaw left

When he attempted the go around, his yaw pedal position was very far behind where it needed to be and then he got weather-cocked to downwind and panicked. = needed enough right pedal to stop the original yaw and more to compensate for the handful of power pulled.

I don't know what Tq warning indications there are on the 120 but the Gazelle had a red flashing light that then went on steady.

In this respect I agree with Megan than concern about overTqing might have prevented him using full right pedal.

So instead of a mild overTq taking a couple of hours off the transmission - he crashed the aircraft instead!!!!!
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Old 24th Jun 2021, 09:56
  #104 (permalink)  
 
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I'm not familiar with this aircraft type. I just assumed it would have a digital engine control that wouldn't let you do anything too nasty to the engine and it would restrict power to a limit and then bleed off RRPM if you applied more collective.
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Old 24th Jun 2021, 10:48
  #105 (permalink)  
 
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Originally Posted by gulliBell View Post
I'm not familiar with this aircraft type. I just assumed it would have a digital engine control that wouldn't let you do anything too nasty to the engine and it would restrict power to a limit and then bleed off RRPM if you applied more collective.
No protections, it's got a nice big FLI display (Zero-Ten scale, 10 is T/O power limit, and a red triangle above for the transient limit).

The Tq limit below Vy (65kts) is 103%, but you are able to pull through that up to 110% for a transient of 5 seconds without penalty. A horn comes on after 1.5s in the transient range to let you know you are there, and nothing on the aircraft would stop you from pulling beyond in order to avoid an accident.
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Old 27th Jun 2021, 09:55
  #106 (permalink)  
 
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Originally Posted by [email protected] View Post

[...] He planned to yaw left to align with the pontoon putting the wind further round. = reduction in right pedal to yaw left

When he attempted the go around, his yaw pedal position was very far behind where it needed to be and then he got weather-cocked to downwind and panicked. = needed enough right pedal to stop the original yaw and more to compensate for the handful of power pulled.

I don't know what Tq warning indications there are on the 120 but the Gazelle had a red flashing light that then went on steady.

In this respect I agree with Megan than concern about overTqing might have prevented him using full right pedal.

So instead of a mild overTq taking a couple of hours off the transmission - he crashed the aircraft instead!!!!! [emphasis by Hot and Hi]

The below has relevance:

Originally Posted by Hot and Hi View Post

[...] new civilian pilots are first and foremost taught to not over control and to avoid harsh, rapid or abrupt control inputs. [...]

When this yaw problem develops (ie in the hover, or when transitioning from slow forward flight to hover) we are (in a H120, Gazelle or Guimbal anyway) already close to max power. Again, pilots primary fear is to avoid over torquing that engine by commanding much of that power sapping Fenestron in the back.

From the actual ATSB Transport Safety Report. Page 35:

Following the [mishap's] pilot’s check to line with the chief pilot on 13 March 2018, the chief pilot noted on the check form that the pilot needed to be gentle on the pedals [emphasis by Hot and Hi]. The chief pilot advised that all new EC120B pilots were coached the same way and the same comment could be found on many of the check ride records for those pilots.
Page 34:

(4) [...] If at this point [in OGE hover just before arriving overhead the pontoon - amended by Hot and Hi] the helicopter was at maximum take-off power, further application of right pedal would not be available (without exceeding engine limitations or ceasing the climb).

(5) The loss of airspeed experienced by a helicopter turning into a downwind position at low speed increases the power requirement[...]. If the use of right pedal was limited by the available power during the initial phase of the go-around, there would not be enough power for a recovery of the left yaw at this point without exceeding engine limitations.
Page 75

[...]there was a reduced power margin available to the pilot on the final approach to the pontoon. This was due to:
  • The aircraft was overweight [[b]actually, above MTOW - amended by Hot and Hi] on departure from Hamilton Island. Being overweight on departure meant that when the pilot reached the pontoon the helicopter was heavier than it should have been. Although it was below the maximum allowable weight when operating at the pontoon, it was close to this maximum allowable weight.
  • The helicopter’s engine power output was close to the lowest allowable limit for the helicopter type.
  • The pilot was required to use high power to make a slow final approach in order to disperse birds from the pontoon.

And finally Page 77, confirming what crab said:

  • The pilot reported keeping the power at or close to maximum take-off power during the go- around, and therefore they had limited power available to correct the yaw. As the helicopter kept yawing further left, it would have reached the point where applying sufficient right pedal to arrest the yaw and then yaw right would have meant exceeding engine limitations. Based on the available evidence, there were no indications an exceedance occurred after the go-around was initiated.
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Old 27th Jun 2021, 10:18
  #107 (permalink)  
 
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Question Stall of vertical stabiliser / tail fin?

Originally Posted by [email protected] View Post
He had a wind from the right which helps in a right power pedal aircraft. = stable so far
It is correct that in a CW rotating helicopter, wind from the right 'unloads' the anti-torque device. In other words, the wind pushes in the same direction as the tail rotor thrust vector. Stable so far, OK, but for how long?

When I did my type conversion on one of those French Fenestron-equipped helicopters, I was taught the that there is a specific problem with wind from the right, related to the stalling of the vertical fin:

  • A large portion of the anti-torque thrust of a Fenestron comes from the airfoil profile of the vertical stabiliser = at forward speed the tail fin creates lift supporting the Fenestron.
  • That tail fin stalls at a given given speed and Angle of Attack, like any other wing.
  • While wind from the right initially supports the Fenestron (ie, requiring less right pedal), the same wind from the right increases the AoA of the relative wind. The increased AoA makes the tail fin stall earlier (at higher ground speed).
  • The change of right pedal required (from pre-stall pedal position, to the position required post stall) is more dramatic in this scenario, as due to the right wind initially the right pedal required was lower compared to pointing straight into wind.

It was said that many pilots got caught out this way. The convex training put specific emphasis on sensitising new pilots for this specific "gotcha" scenario.
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Old 27th Jun 2021, 12:42
  #108 (permalink)  
 
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Probably most have seen this paper already, but for the few who may not have it has some relevance: ERF2019-0017.
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Old 27th Jun 2021, 23:40
  #109 (permalink)  
 
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We operate an EC120 amongst other types. When flying heavy you are in constant fear of an over torque. Takes you back to the robby days, of having to plan out every approach carefully beforehand to ensure you don't bump it over the red line. Everything (wind etc) needs to be stacked in your favour. In my experience it is a huge distraction. The problem is that the engine produces a lot more power than the transmission will handle, so there is always a hesitation to put in a boot load of right pedal as this is the quickest way to an over TQ. I reckon that was at least a consideration by the pilot here, if not a large part of the cause of the accident. This is NOT the case in the other fenestron equipped machine I fly regularly, the EC130 where you can happily use up all the pedal travel without pushing the FLI into the red.
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Old 27th Jun 2021, 23:59
  #110 (permalink)  
 
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Are we saying the EC-120 is poorly designed?
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Old 28th Jun 2021, 05:25
  #111 (permalink)  
 
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Originally Posted by SASless View Post
Are we saying the EC-120 is poorly designed?
I personally think the EC-120 is a delightful helicopter.
It does not have a large power margin like an AS350 B2/3 for example, or an easily ignored power limit like an R44 at sea level, for example.
Much like many helicopters (B47/B206/A109A/B222 for examples) it requires some thought, intelligent and appropriate techniques applied, especially when loaded near max gross weight.
Iíd rate itís performance as very similar to a B206III (But it wonít run out of TR authority, and it will record any exceedanceís)

Considering it is a much newer design, and the size of the boot - the performance is disappointing*, and leads to pilot induced problems. But you canít depart vertically in B222B at max gross weight either, even on a cool night. Well, I canít.

*Potentially designed this way, to prevent competition with other Airbus products.
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Old 28th Jun 2021, 06:07
  #112 (permalink)  
 
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Every helicopter with a vertical fin will experience changes in the lift it produces at various speeds and the Fenestron equipped aircraft just have bigger fins than most - as Hot and Hi says, to offload the Fenestron in forward flight.

I think it less likely to have been a factor in this accident since he was already in a low speed situation when the yaw started and the main effect of the vertical fin would have been felt as he yawed to give himself a downwind component - a tendency to weathercock towards complete downwind would have been the result, not a stall.
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Old 28th Jun 2021, 09:35
  #113 (permalink)  
 
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I think we are all in agreement that another pilot crashed another helicopter that had nothing wrong with it. The next example is just around the corner and will appear here soon enough for sure.
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Old 28th Jun 2021, 17:12
  #114 (permalink)  
 
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Originally Posted by Twist & Shout View Post
I personally think the EC-120 is a delightful helicopter.
It does not have a large power margin like an AS350 B2/3 for example, or an easily ignored power limit like an R44 at sea level, for example.
Much like many helicopters (B47/B206/A109A/B222 for examples) it requires some thought, intelligent and appropriate techniques applied, especially when loaded near max gross weight.
Iíd rate itís performance as very similar to a B206III (But it wonít run out of TR authority, and it will record any exceedanceís)

Considering it is a much newer design, and the size of the boot - the performance is disappointing*, and leads to pilot induced problems. But you canít depart vertically in B222B at max gross weight either, even on a cool night. Well, I canít.

*Potentially designed this way, to prevent competition with other Airbus products.
Close to or at MTOW you have to plan your flightpath with most helicopters very carefully.
I recall pleasure flights with the Bell 206 where the ground crew brought the fat father with the fat mother and the fat kids just after refuelling - forcing the doors shut....
When I was young and not bold enough to say - NO
Creeped away in the ground cushion (but that's another thread here on PPRuNe)
Only, that the EC120 is recording over limits - while other conventional helicopters doesn't - shouldn't prevent a pilot to over torque - if it is required to survive.
Its shameful - and shouldn't be done on e regular basis - but better than crashing ...
If the other helicopters could tell, how often they have been mistreated - you would have to listen to long stories...
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