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Bell 429 - undemanded yaw question

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Bell 429 - undemanded yaw question

Old 31st Jul 2018, 16:05
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Originally Posted by Bell_ringer
Dammit!
We fly on the other side of the road here, probably why everything is the other way round
That explains it!
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Old 1st Aug 2018, 14:22
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From the latest White Horse News freebie rag, which has just dropped through the letterbox.

". WILTSHIRE Air Ambulance’s helicopter is now able to resume flying operations. Following rigorous testing of the Bell 429 helicopter on the ground and in flight, it was released back to operational flying last month.
The helicopter had been out of service since the evening of 15th June following an incident on the charity’s helipad at its airbase at Semington, near Melksham.
The charity stated, “While the pilot was carrying out the prescribed daily engines’ power assurance checks, the helicopter suffered an event of uncommanded tail rotor input. During the procedure the helicopter performed two and a half, counter clockwise, uncommanded spins and came to its final stop following the prompt and appropriate actions of the pilot. No damage occurred to the aircraft, ground equipment or airbase. "


Air ambulance returns to the skies | White Horse News
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Old 2nd Aug 2018, 08:39
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If it's not one thing, it's another! This from the local police Faceache page - my bold

"Wiltshire Police
16 hrs ·
As part of the ongoing operation into the Amesbury poisoning, specialist teams will now undertake precautionary testing of the Wiltshire Air Ambulance station, emergency vehicles and kit worn by responders involved in the initial response to Charlie Rowley and Dawn Sturgess.The highly precautionary process, is designed to ensure that no onward contamination has taken place. The risk of this is assessed as low, however it is essential that no chances are taken and this is why the work is taking place.To ensure that the specialist sampling teams are able to complete their work unimpeded, the Air Ambulance base, located in Semington, will close temporarily from 5pm today (Weds 1 August 2018). During the course of the work, the Air Ambulance will also be subject of precautionary sampling and will be unable to fly. During the period that the helicopter is unable to fly, the charity’s paramedics and doctors will remain fully operational providing critical care in Wiltshire by using Rapid Response Cars. The cars have the same specialist medical equipment that is on-board the helicopter.

Last edited by Cpt_Pugwash; 2nd Aug 2018 at 08:41. Reason: Speelling
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Old 19th Aug 2018, 19:44
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Originally Posted by Dai Whirlybird
I hear that the WOG (wheels on ground switch) failed shortly after this airframe returned into service following the undemanded yaw incident - here's a question or two.....

Given that PAC (Power assurance check)s are done when light on the wheels, Is it feasible that the WOG micro-switch can cycle on and off in this configuration or is it isolated by software when conducting the PAC?

The WOG switch undoubtedly feeds it's status into the ADIU (Aircraft Data Interface unit) so is it possible that a cycling WOG switch or an intermittent fault with it could create confusion within the ADIU and generate spurious control inputs? What I don't know is whether the AFCS / AP configuration when conducting a PAC will permit or prevent this.
As a development but not necessarily an answer to my own question, I've just discovered this in the 429 Avionics manual. (8-2)

"The AP will perform a preflight self-test when the AP switch is turned ON

The preflight test requires the following:

• The TRIM switch is ON
• The helicopter is on the ground (weight-on-gear )
• Engine power is available and is set at low torque
• The other AP is not in the process of performing its self-test

During the preflight test, the AP verifies its ability to manipulate the actuators.

So there's a definite link between the WOG status and the AP testing the acuators.

As stated I do not know what state the AP was in at the time, but (to my mind and based on the foregoing) there definitely seems to be potential for a faulty WOG switch to impact on the AP self test of the actuators.

I guess, given the AAIB's lack of involvement that we'll never know.
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Old 19th Aug 2018, 20:00
  #45 (permalink)  
 
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Originally Posted by Dai Whirlybird
• The TRIM switch is ON
• The helicopter is on the ground (weight-on-gear )
• Engine power is available and is set at low torque
• The other AP is not in the process of performing its self-test

During the preflight test, the AP verifies its ability to manipulate the actuators.
That's quite a potential failure mode?
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Old 19th Aug 2018, 20:22
  #46 (permalink)  
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As stated I do not know what state the AP was in at the time, but (to my mind and based on the foregoing) there definitely seems to be potential for a faulty WOG switch to impact on the AP self test of the actuators.
only if the pilot was stupid enough to initiate the AP test in the middle of the PAC when light on the skids - unlikely!

I don't want to seem PC but the acronym WOG has a distinctly 70's racist undertone and could be replaced by another term.
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Old 19th Aug 2018, 20:34
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Originally Posted by [email protected]
only if the pilot was stupid enough to initiate the AP test in the middle of the PAC when light on the skids - unlikely!

I don't want to seem PC but the acronym WOG has a distinctly 70's racist undertone and could be replaced by another term.
Crab, I disagree if the AP was initiated correctly but a faulty WOG switch prevented the self test from initiating it could then erroneously signal weight on gear at the wrong time and the AP could then initiate the self test at the wrong moment, the self test involving communication with the actuators............

As for WOG being racist, don't be pathetic- it's all about context and we're talking about helicopters....For those who don't know it means WEIGHT ON GEAR as referenced throughout the FM....and that's not a radio frequency.............
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Old 19th Aug 2018, 20:36
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Very PC. You could always write wheels on ground in full everytime.

Most under 40s would not even notice. We older persons will truly die out.
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Old 19th Aug 2018, 21:13
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Originally Posted by [email protected]
only if the pilot was stupid enough to initiate the AP test in the middle of the PAC when light on the skids - unlikely!
I agree it is unlikely, but we're all fallible - which is why we need to learn from this and it's also why I'm disappointed that this incident hasn't been looked into by the AAIB. Leaving it's causal investigation to the operator and manufacturer with their respective operational interests could ultimately benefit no-one, indeed there is an obvious solution to this which I'm sure, given the chance, they'd both take as a mutual reputation saver and that is pilot error.

The thrust of my ramblings is that without independent oversight (AAIB) and due process, we (outsiders) will almost certainly never know what caused this aircraft to spin 2 1/2 times and end up 2-3 metres from the hangar door.

You appear to be quite protective of the pilot, I know them and their background and wonder if they are one of your ex SAR colleagues? Please try and keep an open mind, we all admire loyalty. but similarly we're all capable of mistakes regardless of whether you're a pilot, a design engineer or a manufacturer of components.
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Old 19th Aug 2018, 21:17
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Crab, I disagree if the AP was initiated correctly but a faulty WOG switch prevented the self test from initiating it could then erroneously signal weight on gear at the wrong time and the AP could then initiate the self test at the wrong moment, the self test involving communication with the actuators.
Don't how you think that would happen - if the faulty switch prevented the AP test from running then it would generate a fault code or warning that the self test wasn't complete. If the self test wouldn't initiate then the switch must have failed to an 'airborne' state - how would that now allow the selftest to initiate when the aircraft was light on the skids?
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Old 19th Aug 2018, 21:20
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We older persons will truly die out.
So shall the young ones at some point!
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Old 20th Aug 2018, 06:38
  #52 (permalink)  
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You appear to be quite protective of the pilot, I know them and their background and wonder if they are one of your ex SAR colleagues? Please try and keep an open mind, we all admire loyalty. but similarly we're all capable of mistakes regardless of whether you're a pilot, a design engineer or a manufacturer of components.
yes, I do know the pilot concerned but you seem keen to point the finger in the direction of pilot error and I'm not sure why. I think you should be commending the pilot involved for managing the situation well and avoiding a disaster bu keeping it upright and closing down the engines quickly.
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Old 20th Aug 2018, 07:26
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Originally Posted by [email protected]
yes, I do know the pilot concerned but you seem keen to point the finger in the direction of pilot error .
Absolutely quite the contrary - I am concerned that they will be scapegoated - if you read my posts, you will see that I'm considering the possible technical causes whilst keeping an open mind.
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Old 20th Aug 2018, 12:37
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Key point here....it matters not "who" was involved.

What matters is "why" the Aircraft spun around several times.....and there is no definitive explanation and no apparent interest by the CAA or AAIB in seeing some sort of explanation to the occurrence.

Why might that be I wonder?
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Old 12th May 2019, 18:48
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It looks like the AAIB did eventually get involved with Wiltshire Air Ambulance's 429 incident(s) and it has resulted in an EAD being issued a few days ago.

Clicky linky thing to the EAD.

Their 429 is still AOG and they're continuing to lease a 902.


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Old 12th May 2019, 23:46
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Is there going to be a statement from the WAA director of aviation!
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Old 15th May 2019, 10:20
  #57 (permalink)  
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Originally Posted by [email protected]
I don't want to seem PC but the acronym WOG has a distinctly 70's racist undertone and could be replaced by another term.
Still not as bad as the ICAO codes for Nigeria Airways and Nigerian Air Force which are NGA and NGR respectively - that's just wrong.
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Old 15th May 2019, 10:58
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Originally Posted by RMK
Still not as bad as the ICAO codes for Nigeria Airways and Nigerian Air Force which are NGA and NGR respectively - that's just wrong.
Nigeria Airways has been defunct for years
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