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Helicopter down outside Leicester City Football Club

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Helicopter down outside Leicester City Football Club

Old 14th Nov 2018, 15:28
  #761 (permalink)  
 
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involuntarily input caused by either the startle factor
Who was actually flying it?
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Old 14th Nov 2018, 15:44
  #762 (permalink)  
 
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Fareastdriver

Given that the AAIB report refers to four passengers and one pilot, and states that the aircraft failed to respond to the pilot's pedal inputs, the answer is obvious.
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Old 14th Nov 2018, 16:44
  #763 (permalink)  
 
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Originally Posted by asdf1234 View Post
Interesting that after loss of TR authority, the aircraft continued to climb. Why would the pilot increase the power when he lost the TR?
I'd assumed that collective increase was part of the initiation of the next manoeuvre and was accompanied by a pedal input to anticipate the increase in torque. In this case only one happened and the aircraft climbed for a short time.
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Old 14th Nov 2018, 20:04
  #764 (permalink)  
 
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Originally Posted by dClbydalpha View Post
I'd assumed that collective increase was part of the initiation of the next manoeuvre and was accompanied by a pedal input to anticipate the increase in torque. In this case only one happened and the aircraft climbed for a short time.
The AAIB reports are always concise in their use of language and never leave room for ambiguity of interpretation. If the climb was as a result of the transition procedure they would either omit the climb event or positively correlate the climb to the transition procedure . They mention the climb subsequent to the TR loss of authority because it is an event of interest to them .

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Old 14th Nov 2018, 20:16
  #765 (permalink)  
 
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Indeed. They do not mention a "collective increase", they merely state that the climb paused and then continued. There is implication that the pause was coincident with pedal movements and associated (correct) yaw which then became yaw that did not reflect the pedal demand.

Head scratch moment - if the tail rotor demand reduces, the system sends more to the main rotor. Remember the collective/pedal interaction?
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Old 14th Nov 2018, 21:13
  #766 (permalink)  
 
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Originally Posted by Cows getting bigger View Post
Indeed. They do not mention a "collective increase", they merely state that the climb paused and then continued. There is implication that the pause was coincident with pedal movements and associated (correct) yaw which then became yaw that did not reflect the pedal demand.

Head scratch moment - if the tail rotor demand reduces, the system sends more to the main rotor. Remember the collective/pedal interaction?
They don't mention collective at all, but there must have been some at some point.

Rather than deduce the pilot was "startled" does it make more sense that the climb was due to a pre-planned manouevre? One which required the application of collective, but was aborted due to the lack of yaw control? How long would it take for him to realise he didn't have yaw control, does this amount to about 100ft?

What feedback would cause loss of tail rotor to send more to the main rotor? Are you thinking an automatic increase in collective pitch, or an ungoverened increase in Nr?
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Old 15th Nov 2018, 05:03
  #767 (permalink)  
 
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Originally Posted by dClbydalpha View Post
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What feedback would cause loss of tail rotor to send more to the main rotor? Are you thinking an automatic increase in collective pitch, or an ungoverened increase in Nr?
I feel this is dead herring!

If the TR Pitch reduces (reduction of effective thrust) drag reduces accordingly. This would momentarily cause the NR to increase as now power available exceeds power demand for Nr Nominal 100%. However, the FADECS would sort this out really quickly. In any case, a slight momentary increase in NR will not correspond to an immediate and somewhat sustained climb.

Other than that I cannot see any other correlation between the Yaw Channel (failed) and the collective moving involuntarily unless the mixing unit was somehow stuffed.
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Old 15th Nov 2018, 05:55
  #768 (permalink)  
 
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However, the FADECS would sort this out really quickly.
Or maybe not - appreciate that the FADEC has inputs from control positions i.e. collective and TR pitch, torque, and atmospheric data and that is mapped inside the ECU to a fuel flow required to achieve the net result.

Actual speed governing might not be a good as "normal" if you had a full left pedal input to the ECU with no resulting increase Q load from the TR would probably give you an unintended result.

NR is normally referenced to the current DA and speed is governed by pre-empting the relationship between CLP and TR pitch. Quite often with CLP and TR pitch inputs are attached to either end of an LVDT (Linear Variable Displacement Transducer) and this value via the map in the ECU will give you a fuel flow pretty close to that required without being reactive to a change in NR.

Current FADEC controlled engines are great. They are also great at masking the true characteristics of the main rotor. When the FADEC is removed from the loop (autorotation) many are surprised at how "lively" the main rotor is to RPM. control.

Loss of input data will normally give you a "DEGRADE" warning but more likely not in this case.
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Old 15th Nov 2018, 06:06
  #769 (permalink)  
 
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Who has tried this profile in the sim yet with a TR failure at the same point?

anyone get away without a red screen?
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Old 15th Nov 2018, 06:10
  #770 (permalink)  
 
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Surely the 'pause' in the climb is as a result of selecting an accelerative attitude at TDP.

Also, if you think you have a control problem at night at a critical stage of flight, I would suggest the natural reaction would be to get away from the ground while you sort it out.
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Old 15th Nov 2018, 06:17
  #771 (permalink)  
 
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Originally Posted by [email protected] View Post
Surely the 'pause' in the climb is as a result of selecting an accelerative attitude at TDP.

Also, if you think you have a control problem at night at a critical stage of flight, I would suggest the natural reaction would be to get away from the ground while you sort it out.
From the preliminary AAIB report:
"The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading. Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilotís left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate."

There seems to have been an increase of 110 feet RADALT after the TR event. However, as someone pointed out, the surface beneath the helicopter is not even so it could also be a Red Herring.
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Old 15th Nov 2018, 06:35
  #772 (permalink)  
 
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Originally Posted by DOUBLE BOGEY View Post
From the preliminary AAIB report:
"The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading. Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilotís left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate."

There seems to have been an increase of 110 feet RADALT after the TR event. However, as someone pointed out, the surface beneath the helicopter is not even so it could also be a Red Herring.
Could just be the drop off of the stadium
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Old 15th Nov 2018, 10:50
  #773 (permalink)  
 
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1837 Arrived at the helicopter, 1844 lifted off - 7 minutes for a walk around, climb in, pre-start checks, 2x engine start and lift off.

At the ground, Started up (power on probably to start the system recording) at 1934 and lifted off at 1937.

Seems to have been in a bit of a hurry?
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Old 15th Nov 2018, 11:24
  #774 (permalink)  
 
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Three minutes to start up and reach Take Off RPM.....not a rush job in modern Twins with FADEC's.

As the Pilot had flown the aircraft on several sectors that day already....there is no requirement for a full run-up systems checks.

If the radios and and nav systems had been pre-tuned and set up for the intended flight....it would just be a matter of turning them on.

To make a point about "time"....I once worked a job where we had to be airborne within two minutes of the Alert Klaxon sounding....and that included up to a fifty yard dash to the helicopter.

That is rushed.....sitting in the aircraft and strapped in and ready to hit the Battery Switch....three minutes is not.
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Old 15th Nov 2018, 11:41
  #775 (permalink)  
 
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From the preliminary AAIB report:
"The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading. Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilotís left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate."

There seems to have been an increase of 110 feet RADALT after the TR event. However, as someone pointed out, the surface beneath the helicopter is not even so it could also be a Red Herring.
the report highlights the 430 as being radio height but not the 320 so I wouldn't set too much store in the accuracy of the comparison - it may be they are both rad alt heights but maybe not - ADC perhaps?

Much like the footnote at the beginning that specifies the timings are approximate since they come from a variety of unverified sources. Trying to come to accurate conclusions based on potentially inaccurate information is folly.
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Old 15th Nov 2018, 12:25
  #776 (permalink)  
 
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Originally Posted by [email protected] View Post
Much like the footnote at the beginning that specifies the timings are approximate since they come from a variety of unverified sources. Trying to come to accurate conclusions based on potentially inaccurate information is folly.
Agreed. The most significant bit of information is the gear being raised at an unusual point in the profile.
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Old 15th Nov 2018, 13:06
  #777 (permalink)  
 
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Three minutes to start up and reach Take Off RPM.....not a rush job in modern Twins with FADEC's.

As the Pilot had flown the aircraft on several sectors that day already....there is no requirement for a full run-up systems checks.

If the radios and and nav systems had been pre-tuned and set up for the intended flight....it would just be a matter of turning them on.

To make a point about "time"....I once worked a job where we had to be airborne within two minutes of the Alert Klaxon sounding....and that included up to a fifty yard dash to the helicopter.

That is rushed.....sitting in the aircraft and strapped in and ready to hit the Battery Switch....three minutes is not.
But that was probably in the military. Many of us have done scramble type jobs. This was not, it was a passenger carrying flight into London Stansted. I will agree to disagree with you on the 3 minutes from start to airborne. But 7 minutes for an aircraft that had been shutdown and unattended for 3.5 hours seems quick to me.
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Old 15th Nov 2018, 16:54
  #778 (permalink)  
 
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Extract from report into AS355 TR Control Failure over Cardiff G-SAEW, Flown by an ex student of mine:

The helicopter had been hovering in the area for about 10 to 15 minutes, facing in a south-westerly direction, when it suddenly made an uncommanded yaw to the left through some 180 degrees. The pilot immediately applied full right yaw pedal to counter this yaw. However, although the helicopter stabilised for a moment, it then yawed more rapidly to the left. At this time he called out to the two observers on board to warn them of a problem with the helicopter. He partially lowered the collective lever in an attempt to regain control and applied some forward cyclic to gain forward motion and airspeed, but the helicopter then entered a steeply spiralling/yawing descent to the left. The pilot realised that he would not be able to recover full control of the helicopter and abandoned his attempt to fly out of the situation. He concentrated on keeping the helicopter as level as possible whilst looking out through the right side window for visual reference, since he found the forward view too confusing due to the rapid yawing motion. He adjusted collective to achieve what he judged to be the best combination of rate of descent against yaw, and when he caught sight of the surface in his peripheral vision he pulled the collective lever fully up to cushion the impact.
The helicopter came to rest embedded in the roof of a house, as shown in Figure 1, having broken through the rafters and settled in a right side low attitude. After the impact, the pilot was unable to reach the engine fuel controls on the overhead panel until he had unstrapped himself from his seat. However, when he was able to reach the speed select and emergency fuel shut off levers he could not move them due to impact induced distortion of the overhead panel. He was able to activate both fire extinguishers and to turn the battery switches OFF. The observer in the front left seat escaped through his door on the left side of the helicopter and the rear seat observer climbed past the pilot and exited through the same door; the pilot then followed. The three occupants, all of whom were wearing protective helmets, were uninjured and later used a ladder to climb down from the roof.


A considerable amount of skill and quick thinking with Lady Luck for the impact. That boy did well!
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Old 15th Nov 2018, 17:11
  #779 (permalink)  
 
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Insider....twas not a military gig....but involved guarding some very high value items.

What is magic about the aircraft being shut down and unattended for 3.5 hours?
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Old 15th Nov 2018, 18:33
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Originally Posted by SASless View Post
Insider....twas not a military gig....but involved guarding some very high value items.

What is magic about the aircraft being shut down and unattended for 3.5 hours?
SASless - no magic! I think the thread looked to be going in a "Left unattended/not properly pre-flighted" direction, due to some of the stated (but not confirmed) timings.

My previous post there by the way is void as its target post was removed.
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