Sierra impacts ferris wheel

[Thruster87]

It's pretty hard to tell from a picture. It's likely that the rivets have not sheared but the panel has peeled off over the rivet heads. That panel would not be a structural member in the strictest sense (I would imagine) Just a cover.The relevant comment that the ferris wheel was a yielding structure that deformed more than the aircraft, thus reducing the damage to the plane, and the occupants, is significant. Nev

Totally agree Nev.I don't know if the top & side panels are stressed.There is a formula to work out the number of extra pop rivets or larger Dia that are needed compared to solids and work [sample testing] done by members on the Matronics site found a great deal of difference just using A4 pops [a lot stronger] rather then A3 and the way the heads peeled of or not.[the quality /consistency of the pops has a big bearing ] I believe they used Avex pops made in England . A very intersting read http://www.ch601.org/resources/riveted_joints_by_chris_heintz.htm cheers

 

 

[turboplanner]

People go thru uni and spend their lives just on strength of

 

Materials.

 

I'll see if I can find the test rig we have to comply with on truck cabs

 

 

[Ben Longden]

Anyway you look at this incident, you have got to say one thing; Gary Morgan has built one heck of a tough aircraft.

 

Me?

 

I will fly in anything he has built.

 

As for the rest of it, lets leave that to the RAA investigators and qualified engineers.

 

 

[Guernsey]

If you all are curious as to what sort of rivets and why they were used, rather than speculate why not just telephone Gary Morgan and ask him???

 

I've always found him to be most helpful.

 

I also totally agree with Ben Longden which is one of the reasons we bought one.

 

Alan Marriette.

 

 

[Thruster87]

Anyway you look at this incident, you have got to say one thing; Gary Morgan has built one heck of a tough aircraft.Me?

 

I will fly in anything he has built.

 

As for the rest of it, lets leave that to the RAA investigators and qualified engineers.

Most kit A/C structures are only static load tested [how many of them have actually been calcaulated by a Aeronautical Engineer]then it basically goes on flying hrs. It is only when there are accidents /incidences/etc that things may appear and highlight issues not foreseen during design.I don't know of any new aircraft design [commercial] that has not been modified later. Even Aeronautical Engineers designing new A/C cannot calculate all the different forces that come into play.I suppose one has to work it out for oneself what standards you are prepared to put up with.It will be interesting to see how deep these investigations will go as the accident appears not to be caused by a structural failure.The following is the RAA requirement for new kit A/C designs

Aircraft of Australian Design

 

. If the aircraft type is of Australian design, a

 

satisfactory history of operation of one prototype plus one identical copy for

 

periods of 200 and 100 hours will provide and acceptable basis for application

 

for approval of the kit for the aircraft type. The second aircraft may be factory

 

or privately built. However no more than two aircraft of the type may be built

 

by a factory following application for approval until approval of the kit has

 

been completed.

 

 

[turboplanner]

ATSB have stepped into this crash, so we don't haved to speculate, the Interim Report will be out in a few weeks and there will be a detailed report only.

 

You're probably right, since you were talking about incidental damage.

 

It's a bit of a leap to start looking at overall designs probably more suitable for a general thread

 

 

[turboplanner]

Thruster, just to settle your mind about the relationship between a space frame design and rivetted cover panels, here's an example of a Sprintcar crash at the Knoxville Nationals.

 

Where the Sierra went in at around 150 km/hr, this guy hit the the wall a diagonal blow at just under 200 km/hr

 

In the sprintcar design, the driver is harnessed to the space frame, and the space frame is triangulated around the driver, so they get their priorities right, and then make the rest of the car as light as possible.

 

In this footage, you'll see a lot of rivet shear, and in fact at one point a rescue crew member just pulls a wing side panel off.

 

In other words these rivets are not a safety item, so no need to fuss about their integrity.

 

 

 

[Guest Maj Millard]

Re: Unzipped rivits....when a person designs an aircraft the main consideration is to the forces that the airframe must handle in flight. you do of course consider the pilot protection angle and design that in also, as the designer appears to have done well in this case. Seeing 'unzipped' rivit lines on a crashed fuselage is not that uncommon, things have to give somewhere.

 

It is almost impossible of course to totally design an aircraft to handle any and all impacts with the ground, or in this case a ferris wheel. To do so would ensure the aircraft was too heavy to ever leave the ground.

 

It is always interesting to study a wreck after impact with a solid object but those forces are impact forces which are unusual forces for an aircraft, and need to be viewed as such. Things can always be learnt of course and I'm sure Gary has in this case............................................................................Maj...

 

 

 

[Hargraves]

They are tough little aeroplanes

g'day swany is that a 500 your flying in the photo

 

 

[Thruster87]

Re: Unzipped rivits....when a person designs an aircraft the main consideration is to the forces that the airframe must handle in flight. you do of course consider the pilot protection angle and design that in also, as the designer appears to have done well in this case. Seeing 'unzipped' rivet lines on a crashed fuselage is not that uncommon, things have to give somewhere.It is almost impossible of course to totally design an aircraft to handle any and all impacts with the ground, or in this case a ferris wheel. To do so would ensure the aircraft was too heavy to ever leave the ground.

It is always interesting to study a wreck after impact with a solid object but those forces are impact forces which are unusual forces for an aircraft, and need to be viewed as such. Things can always be learnt of course and I'm sure Gary has in this case............................................................................Maj...

All the ones of accident damaged aircraft [not flying race cars] that I've come across, the occurrence of unzipping rivet lines is not common.There is a lot more tearing taking place of the parent material .These aircraft I'm referring to are salvage [some world war 2] from around the world and rebuilt if viable at HARS. Bit of an example of the Qantas bottle explosion below. Cheers

 

 

[turboplanner]

I'd agree with you there because you are describing monococque construction where the rivets are structural components and are designed not to be the weakest point.

 

Cover panels are expendable, so no need to got to that expense.

 

 

[David Isaac]

Anyway you look at this incident, you have got to say one thing; Gary Morgan has built one heck of a tough aircraft. Me? I will fly in anything he has built.........

I can make no comment as to the 'toughness' of this little aircraft because I simply do not know how 'tough' it is. I will certainly say that the resultant damage to any aircraft in this accident should not be used as any example of how 'tough' it is in these circumstances.

This accident is unique in that the aircraft was simply caught by a big metal net at low speed (the aircraft was slow and on the verge of the stall from the witness reports I was told), the net being the Ferris wheel. The effect of which was a yielding object and the deceleration forces absorbed by the distortion and movement of the Ferris wheel and the tearing of of the aircraft wings and other components.

 

We really ignorantly kid ourselves if we think this is what would happen if you hit the side of a mountain, or spun in from some height. There is a fair bit of romantic nonsense saying this aircraft is 'tough' based on the damage in this circumstance. Please understand I am not saying the the Sierra is tough or otherwise, I am just taking an objective look at the circumstances.

 

 

[turboplanner]

I was going to say nearly the same thing. The aircraft all but flew into a safety net on this particular occasion, but of a key part of the space frame had hit one of the heavier duty parts of the ferris wheel, the there may have been frame crush. If the ferris wheel hadn't been there and the aircraft had hit the trunk or a large bough of one of the trees reported to be in the background there would have been much greater deflection.

 

The deceleration effect from what did bend in both structures was more likely to be what saved their lives, by preventing brain crush.

 

What you could say with this crash though is that in this instance the space frame may have saved some more extensive crushing on the way in.

 

 

[Guest Maj Millard]

thruster87, The photo in your post #36 showing the damage to the Qantas aircraft illistrates damage to a composit fairing does it not ?......These generally don't use rows of rivits in their construction.............Maj...

 

 

[Guest Swanny]

g'day swany is that a 500 your flying in the photo

Hi hardgraves

No Its a Strut braced Drifter.

 

 

[Thruster87]

thruster87, The photo in your post #36 showing the damage to the Qantas aircraft illistrates damage to a composit fairing does it not ?......These generally don't use rows of rivits in their construction.............Maj...

Maybe if you look a little deeper. Cheers [used to take these fairings of to do inspections, when I worked for Qantas]