AS 350 down (9 April 2018)

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jimdavis
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Re: AS 350 down (9 April 2018)

Unread post by jimdavis » Mon Apr 16, 2018 10:49 pm

tanglefoot wrote:
jimdavis wrote:
tanglefoot wrote: Shhhh, don't tell everyone.
Come on Tangles - you know he wasn't referring to you. 8-[ :lol:
jim
Yes, I know that but he was probably referring to cage and that is even worse 8-[
:lol: :lol: :lol:

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Re: AS 350 down (9 April 2018)

Unread post by hugo_visser » Tue Apr 17, 2018 1:01 am

Looks as if some extra training is booked for me, just for the fun of it. I must be sick,cannot get enough training.

Hugo.
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Re: AS 350 down (9 April 2018)

Unread post by cage » Sun Jun 03, 2018 5:47 pm

Prelim report, would appear to have lost control during a sideways OGE hover.

http://www.caa.co.za/Accidents%20and%20 ... ZS-HHI.pdf
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Re: AS 350 down (9 April 2018)

Unread post by happyskipper » Sun Jun 03, 2018 5:58 pm

cage wrote:Prelim report, would appear to have lost control during a sideways OGE hover.

http://www.caa.co.za/Accidents%20and%20 ... ZS-HHI.pdf
Am I dreaming, Cage? A prelim report, a mere month and three and a half weeks after the accident?
And it is clear and concisely written?

This is a vast improvement to the trash we have seen in the recent past. Well done, CAA and the AIID division. =D>
:roll:
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Re: AS 350 down (9 April 2018)

Unread post by jimdavis » Sun Jun 03, 2018 7:04 pm

WOWEEEE!!!! Since I havd been in the forefront of those bitching about the appalling standard of accident reports, let me be amongst the first to congratulate all those concerned in putting out this really excellent pereliminary report. It is clear, insightful and very well written!

Well done indeed guys and girls. =D> =D> =D> =D> =D>

Now please keep it up [-o<

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Re: AS 350 down (9 April 2018)

Unread post by Tim » Sun Jun 03, 2018 7:24 pm

cage wrote:Prelim report, would appear to have lost control during a sideways OGE hover.

http://www.caa.co.za/Accidents%20and%20 ... ZS-HHI.pdf
From the preliminary report:
3.3 The pilot reported that he was circling anti-clockwise overhead the farmstead at a height of approximately 50 to 100 feet above ground level (AGL). This was a maneuver whereby the helicopter hovers in a circle around the nose as an axis. The pilot reported that he was flying sideways at approximately 30 knots when the helicopter began to yaw and spin uncontrollably in an anti-clockwise direction.
A cool little airshow manoevre. Takes a bit of skill, quick feet, a large margin of available excess power (torque) to meet the very quickly changing power demands from the anti-torque rotor. Gets more difficult the heavier you are - in other words if you think you just manage on your own, it will feel much more difficult with 4 pax.

Let’s wait for the final report to find out about prior experience of the mishap pilot, his/her AS350 type rating, etc. The preliminary report seems to suggest that the owner pilot for a first time flew with pax (4 of them) during the accident flight.
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Re: AS 350 down (9 April 2018)

Unread post by cage » Sun Jun 03, 2018 7:31 pm

Tim wrote: A cool little airshow manoevre. Takes a bit of skill, quick feet, a large margin of available excess power (torque) to meet the very quickly changing power demands from the anti-torque rotor. Gets more difficult the heavier you are - in other words if you think you just manage on your own, it will feel much more difficult with 4 pax.
It would be interesting to know the limits of that tail in sideways flight and what the wind conditions were.
Away from sea-level and loaded it could have been a bit of a handful, or is that footful?

edit: On the 407, for example, sideways flight/crosswind is limited to 35 kts.
350B3 FM states testing of 17kts for all conditions and tested to 30 kts at sea-level but doesn't seem to have a specific limit.
30kts sideways flight, throw in some wind and one could imagine you need to have some skill to not get behind the aircraft.
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Re: AS 350 down (9 April 2018)

Unread post by Arch » Sun Jun 03, 2018 10:53 pm

Squirrel has plenty of TR authority. He should have been turning clockwise using the power pedal, which would have used more power but given greater stability. Instead, he used the rotor torque to turn, reducing power requirement but sacrificing control
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Re: AS 350 down (9 April 2018)

Unread post by happyskipper » Sun Jun 03, 2018 11:10 pm

cage wrote:
Tim wrote: A cool little airshow manoevre. Takes a bit of skill, quick feet, a large margin of available excess power (torque) to meet the very quickly changing power demands from the anti-torque rotor. Gets more difficult the heavier you are - in other words if you think you just manage on your own, it will feel much more difficult with 4 pax.
It would be interesting to know the limits of that tail in sideways flight and what the wind conditions were.
Away from sea-level and loaded it could have been a bit of a handful, or is that footful?

edit: On the 407, for example, sideways flight/crosswind is limited to 35 kts.
350B3 FM states testing of 17kts for all conditions and tested to 30 kts at sea-level but doesn't seem to have a specific limit.
30kts sideways flight, throw in some wind and one could imagine you need to have some skill to not get behind the aircraft.
Cage - how do you read airspeed when traveling sideways in a helicopter? I don't have a clue whether they have pitot tubes or whatever, but am very interested in finding out.....
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Re: AS 350 down (9 April 2018)

Unread post by Bront » Mon Jun 04, 2018 3:35 am

Ok, although well written there is something wrong with the description of this accident.

Firstly it says that the pilot was circling around the farmstead.

Then it describes a peddle turn around the nose. A peddle turn around the nose can only be done in the hover. These are two very different manoeuvres. It cannot be both.

It then reports the pilot said he was going sideways at 30 kts. That doesn't make any sense for a peddle turn around the nose.

It also mentions that the wind was 20 to 25 kts.

I would like to suggest that what they are trying to say is that the pilot was circling around the farmstead at 30 kts.

To me this looks like a classic case of turning downwind, whilst low and slow. He would have had 50 to 55 kts indicated on the upwind leg, which requires very little power in a helicopter and minimum anti torque peddle, then as he turned downwind, the indicated airspeed would have dropped to 5 to 10 kts. This speed requires the most power and the most anti torque peddle. As he turned downwind, the airspeed would have dropped below translational lift (about 17 kts) and he would have started to sink. Flight below translational lift requires a lot of power in a helicopter. As he started to sink he would have raised collective (increasing lift and power) which would have required a corresponding peddle input, to counter the extra torque caused by the increase in power. In this situation the peddle input needs to be anticipated, or else a yaw will develop quite quickly. In this helicopter the yaw would have been anti clockwise and he would have needed to put in right peddle.

If he was going slightly slower, than he thought, then he could quite easily have had a tailwind and actually been trying to fly backwards. The helicopter would then have been trying to weather cock into wind, which would have required an even larger peddle input.

Once he lost control he was obviously descending (or he wouldn't have hit the ground) and would have wanted to pull even more power (collective) which would have required even more right peddle. If he had run out of peddle then he would not have been able to stop the spin without lowering collective, which is counter intuitive. Just like a stall in a fixed wing, you have to loose height to recover.

Just like in fixed wings, this low and slow circling over a fixed spot, in strong winds, has caused many accidents, particularly in low hour pilots. Unlike fixed wings though, there are quite a few helicopters pilots that have been high enough to do a few spins before saving it. A new pair of underpants and lesson learnt hopefully.

This is not necessarily a dangerous manoeuvre, unless you are too heavy to hover OGE (out of ground effect). It should be taught in your PPL but is usually done in fairly light winds. The secret is in anticipation, you need to start putting in peddle early, before any yaw starts. If it gets to the point where you have full peddle input and you are still rotating then you HAVE to lower the collective. This usually doesn't have to be much and if done correctly, results in a tiny loss of height.

Just my 2 cents worth.
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Re: AS 350 down (9 April 2018)

Unread post by Peregrine » Mon Jun 04, 2018 6:34 am

Agree in general with Bront. The report is well written, apart from some minor points. The major concern is the description of the manoeuvre, which is not clear. Mass and balance? Reference to FM limits?
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Re: AS 350 down (9 April 2018)

Unread post by jimdavis » Mon Jun 04, 2018 8:29 am

Bront - I think you have got it bottled on the downwind turn using ground references. A killer in fixed and rotary wing aircraft.

And I still think this is a brilliant preliminary report. They have still got time to sort the rat-<<moderated - language>> from the rice before getting the full report out.

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Re: AS 350 down (9 April 2018)

Unread post by cage » Mon Jun 04, 2018 9:02 am

Peregrine wrote:Agree in general with Bront. The report is well written, apart from some minor points. The major concern is the description of the manoeuvre, which is not clear. Mass and balance? Reference to FM limits?
There certainly is some ambiguity, but it is a rather specific description by the author.
I could certainly imagine it's something, someone with a new, powerful machine wanting to show the pax a bit of a "ride" may do. You certainly do see worse.
Guess I am finding it hard to believe someone could lose control of a squirrel like that.
It would really need to be taken outside the envelope and the rpm let to decay, for that we would need to understand the W&B and environment a bit better.
Hopefully this is something that is properly covered in the final report.
(any progress on your CAA initiative?)
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Re: AS 350 down (9 April 2018)

Unread post by hugo_visser » Mon Jun 04, 2018 9:28 am

Bont, you can go sideways and turn around the nose, I know it as a guppy and is done in our exercises on the helipad from one corner to the other corner, or along the runway and seen at some airshows while going in a circle.

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Re: AS 350 down (9 April 2018)

Unread post by cage » Mon Jun 04, 2018 9:35 am

I am fairly certain both Bront and Peregrine know what a guppy turn is.
What was being alleged is more of a wider, higher speed "round the hole" maneuver, probably better known locally as a Menno ;)

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