Trojan Gyro down near Parys 2017-11-21

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jimdavis
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by jimdavis » Wed Dec 06, 2017 9:48 am

V5 - LEO wrote:... my guess is start looking at pilot incapacitation, medical ?, maybe bird strike to head
I am beginning to think that way too, Leo.

Actually I would like to know a bit more about exactly what work they had done on the gyro, and what he was testing.

ek
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by V5 - LEO » Wed Dec 06, 2017 11:07 am

jimdavis wrote:
V5 - LEO wrote:... my guess is start looking at pilot incapacitation, medical ?, maybe bird strike to head
I am beginning to think that way too, Leo.

Actually I would like to know a bit more about exactly what work they had done on the gyro, and what he was testing.

ek
......yes that could help, maybe some of the toxins {if there were any present} taking a late or early effect????
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by apollo11 » Wed Dec 06, 2017 12:12 pm

How robust are the bearings in the rotor head? How robust is that teeter bolt? What are the enhances of the rotor head seizing (not related to this accident just general questions)
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by rotorman » Wed Dec 06, 2017 4:38 pm

Hi Jean.

I understand your reasoning re the blade based on the roll-overs that you have witnessed. Roll-over time rate is relatively slow wrt blade RPM period and rotation is around a fixed pivot point. Consequently two mangled blades normally result. I think that in this case the scenario was markedly different. If say the normal operating RPM for these longer blades were between 300 and 350, half a blade revolution will take between 90 and 100ms. Expenditure of the total rotor energy on impact is going to take place in much less time than 100ms. With all energy expended, it comes to rest. If the forward blade is just off the horisontal when the rear blade makes fairly ‘solid’ contact, the forward blade, rotating and very stiff due to centripetal force, will still be off the horizontal by the time all rotor energy, meaning that of both blades as they are mechanically connected, is expended. Same principles apply in the cases of a vehicle smashing into a concrete wall or a bullet fired into the sand – some parts of the system absorbs all the energy of the total system and leaves the other connected parts fairly intact. The position of the ‘undamaged looking’ blade wrt the wreckage supports the reasoning. I am not arguing that this was definitely the case, but it is physycally possible and I can find no other explanation for what is seen. Therefore the ‘Do not read too much..’.

The condition of the prop blades suggests the possibility of an engine out and I was thinking of a forced landing gone wrong for some reason or the other. But then again, Crazydoc’s post shows how quickly things can go south. Thanks for candidly sharing Crazydoc.

We will sadly and frustratingly probably never know exactly what happened, only that it should not have happened.

Rgds
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by Rotor kop » Wed Dec 06, 2017 5:03 pm

Just watching gyros take off looks so unatural. The angle between rotor disk and forward motion is huge. Dont know how that mast and rotor head can last. There are 1000's of them flying so it obviously works but not for me thanks.
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by jtresfon » Thu Dec 07, 2017 8:16 am

apollo11 wrote:Once this happens is it game over right there or can the pilot throttle back and pitch up very gently to recover?
If a retreating blade stall is severe enough that blade flap occurs in flight beyond the limits of the teeter stops, i.e. causing the gyro to roll left in the sky it is pretty much game over. Prevention is better than cure! This is the reason for the very clearly marked VNE limits.
apollo11 wrote:How robust are the bearings in the rotor head? How robust is that teeter bolt? What are the enhances of the rotor head seizing (not related to this accident just general questions)
The rotors on a (modern 2 seater) gyro rotate at a relatively low RPM, normally approx 350-450 RPM during flight. Thus the rotor head bearings are not working hard and the bearing temp tends to be only a degree or two above ambient temperature. The teeter bolt is very robust. Assume an LSA max all up weight of 600kg the most g-force you could pull is less than 3g giving a total weight on the teeter bolt of around 1.8 tons. Some of the gyros have teeter bolts rated to 25 tons. The chance of a rotor head seizing is small enough to be completely discounted (assuming of course that servicing and maintenance has been carried out to factor standards by an approved person). One of the longest flying modern gyros is the Magni and to the best of my knowledge they have not had a single incidence of a rotor head failure in all their years of operation.

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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by apollo11 » Thu Dec 07, 2017 8:59 am

Thank you for the clear and in depth explanation Jean, most interesting.
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by Adie » Thu Dec 07, 2017 2:05 pm

Something that is bothering me.

Looking at the ashes in the pictures again it seems as if the pilot got out of the Gyro at some stage.

A
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by jimdavis » Thu Dec 07, 2017 2:22 pm

Adie wrote:Something that is bothering me.

Looking at the ashes in the pictures again it seems as if the pilot got out of the Gyro at some stage.

A
Greetings Adie - and a big welcome to Avcom =D> =D> :D :D

An interesting first post. What makes you say that?

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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by Adie » Thu Dec 07, 2017 3:05 pm

jimdavis wrote:
Adie wrote:Something that is bothering me.
Looking at the ashes in the pictures again it seems as if the pilot got out of the Gyro at some stage.
A
Greetings Adie - and a big welcome to Avcom =D> =D> :D :D
An interesting first post. What makes you say that?
jim
1. The ashes around the cockpit is undisturbed. No struggle or removal disturbances.
2. I would expect some indication of the remains like helmet etc.

Thanks for the welcome Jim, I've been interested in aircraft for many years. Did fly gliders as Swellengrebel many years ago. Tried some radio controlled fixed wing and helie's.
A
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by jimdavis » Thu Dec 07, 2017 5:03 pm

Adie wrote: Thanks for the welcome Jim, I've been interested in aircraft for many years. Did fly gliders as Swellengrebel many years ago.
A
Perhaps we even met there - I did some tugging and gliding there in the mid 60s.

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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by jimdavis » Fri Dec 08, 2017 5:00 pm

I have been fast asleep. WWW?

Any chance there could have been thunderstorm activity around?

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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by John Boucher » Sat Dec 09, 2017 5:52 pm

Inclement weather could just put a different "spin" on this accident?
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Re: Trojan Gyro down near Parys 2017-11-21

Unread post by cage » Thu Dec 21, 2017 4:02 pm

According to the CAA incident report
According to reported information the pilot was conducting crop spraying software equipment testing . The farm workers witnessed that they saw veld fire in the area and looks like an aircraft burning along with the surrounding veld.
They have classified the operation type as crop spraying it would seem, most probably as it was necessary for testing to fly in a manner associated with agri work.
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Difference in HV curves between gyros and choppers

Unread post by Tim » Sun Dec 24, 2017 12:50 pm

Jack Welles wrote:
apollo11 wrote:However the helicopter shaded unsafe operation area is substantially larger than that of the gyro.
I don't know if it makes a difference, but coming short in a helo in the Dead Man's Curve isn't a "do or die" event: it can, of course, be catastrophic but the range of seriousness also extends to just a "hard" landing.

Not sure about the gyro? If one is in the shaded area and you go down is that always a very bad result?
All things being equal (weight, main rotor blade profiles, etc.) the height velocity (HV) curves shouldn’t be different.

Note however that in determining the HV curve for helicopters, an intervention delay time of 1 or 2 seconds is assumed (time between the engine stopping, and the pilot lowering the collective to enter auto-rotation). Whereby the gyro plane already is in auto-rotation when the engine stops.

This, by definition, would create a bigger HV avoid area for a helicopter than for a comparable gyro plane.

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