ELA Eclipse Undercarriage main landing gear collapse - Please inspect

[Abid]

Aluminum as a spring leaf? Do you know how many airplanes use Aluminum leaf springs?
Try this just for a sample

Grove Landing Gear

Same for even the axles. Tons of them use Machined Aluminum axles. Grove, Matco, Cleveland and so on.
And no. You cannot get the strength from Steel alloys at the same weight as 7075-T6 Aluminum. Ain't ever going to happen. 7075-T6 Aluminum for the same strength is going to be 45% of the weight of Steel alloy. The safety factor applied in such Aluminum applications is supposed to be 2x as opposed to 1.5x. This is to keep fatigue life in check.
Now if your engineering is crap, your manufacturing engineering is crap, then yes you are going to have junk in = junk out. That isn't the fault of the material. That is the fault of an engineer not knowing how to engineer for the given material.
Why would you drill a hole through Aluminum. To secure the landing gear in its bracket of course. You know so many rotors whose hub bar is made of solid Aluminum with holes in the hub bar to bolt clamping plates to clamp to blades. Dominator (Dragon Wings), GyroTechnic, Averso, and tons of others. By this logic all of these are wrong. No they aren't wrong. They are just done properly and inspected for torque and tightness every year. You may not care about the bore not being smooth but Physics does care. A loose uneven hole creates movement and movement creates fatigue. Simple as that. The assembly needs to act as one unit between landing gear leg and its securing/supporting structure. Tubes do not make a great landing gear. Leaf springs are solid and usually machined from bigger to smaller radius to behave properly as landing undercarriage.
I agree there is nothing earth shattering here but I think you are completely off base in your assumptions.
In this particular case if there was a previous incident as was said with rims coming off because of wrong bolts being used, then it is very likely that in that incident that landing gear took a lot of abuse and that hole became damaged and no one bothered to inspect and check it and fix it. A simple fix would be to redrill and ream and upsize the hole and use an Aluminum bushing pressed in to bring it back to bolt size. That would have halted the problem with a proper bolt torque and stop the movement of the landing gear inside the bracket and thus stopping the accelerated fatigue cycle. A proper A&P mechanic or an engineer would know to do that. An end user or a car mechanic who just wrenches and knows nothing else, won't.

I will agree with you on this. If the hole is drilled in the area where the bending loads concentrate, then it is in the wrong place and will cause accelerated fatigue and design should be changed. But honestly, I have never bothered to look closely enough at an ELA Eclipse to really say that for certain. So, I hesitate to blame the design so far. Maybe I will get a chance to look at an Eclipse undercarriage more closely at Mentone and can determine that. It won't be hard to really. I would be surprised though. These guys have been designing gyroplane frames for a while. I mean they must know that by now ...

Attached you will see Aluminum leaf landing gear in a Delta Jet trike that crashed in a cow field after previous owner had put on 373 hours on it because the 73 yo new owner/pilot did not take enough training to get the add on and decided to fly it, got scared and landed in a cow pasture completely doing a number on it. You can see one side is completely bent up but it did not break. There are no holes in the area where it bends though.
You can see Recon airplane I just designed has Aluminum leaf landing gear and how it is secured. No holes in the area bending loads concentrate instead a clamping bracket securing it to the fuselage. This is similar to an Avid Flyer and KitFox and these planes operate out of grass fields all the time. There is no problem.
Also the Aluminum leaf landing gear on an AR-1. This is simply a borrowed from self design of undercarriage from Delta Jet 2 trike except beefier to carry extra 150 pounds of gross weight on the gyro.

 

[Chook]

Was this rim on the same side as the landing gear that broke now? That could have caused damage in that bolt hole when the rim came off. That damage then started the fatigue because it was not caught in a proper thorough inspection before.

Abid it certainly looks like the port side wheel has been involved on both occasions.

Regards.........Chook.

 

[Aerofoam]

Well you can see the fatigue though correct. It is clear as the blue sky in that picture. Unless this landing gear has seen over 2000 hours and many cycles, that fatigue only has one cause. Movement. Movement would not happen if the bolt was tight and secured.
I do not think this is design flaw necessarily. It may be but we don't have enough info to say that. This model did pass German BUT certification which does require dead drop tests and a safety factor. I think this is a manufacturing flaw or if this is the same side where people are saying the rim came off during ground roll for takeoff, then it is a flaw created from that incident without being properly checked and caught back then and made worse with further usage. So that we are clear, I am not prepared to say this is a design flaw but I am prepared to say it is good to inspect this area. If you have things like rims coming off, then inspection shouldn't just stop at the rim and axle. Many end users always seem to fall in this trap. You really ought to inspect the whole assembly and in a gyro even the frame. Load paths go through the whole structure right into the mast.

The horizontal hole doesn't present a large compromise to the vertical forces, but the horizontal forces magnified by irregularities in a grass
strip are certainly going to cause more problems that maybe were not accounted for.. As far a spring is concerned, without knowing the measurements, I think it looks too small even if it didn't have a hole through it. A forward control rod could be very small and add immense strength to the system making it far more robust for rough fields. Maybe this was a fluke, a one time isolated incident totally brought on by a prior wheel issue. Lets hope so, but from this armchair quarterback position, I think it should have been executed better.
I have seen many solid AL struts, they are usually a wider section, quite heavy and the better ones are heat treated and forged.
lets compare apples to apples here, we are talking about relatively light duty equipment for a recreational vehicle, but it can still hit hard and be subject to shock loading. The machined heat treated suspended landing gear on a F-18 was massively designed for impact, no comparison...
They are usually on aircraft that land on paved runways and some have suspensions which changes the whole enchilada.
Of course proper engineering is the key ingredient, but again, why such a small margin of error???
Almost all of the DOD equipment I have designed has been able to sustain 5x the estimated working load.
I have had experience in off road racing with rail type vehicles and mountain bikes. Aluminum fails quickly when subjected to repetitive shock
loading. I have yet to see and off road race car made from aluminum, they are always steel and aluminum mountain bikes are generally only about 12% lighter than ChroMo and they break. When you can shave a few ounces from a racing bike and the MFG gives you a new one when it breaks, AL is great.
My friend and cohort in UAV projects started out making titanium mountain bikes in the 90's
Ti was/is the best option, but the cost is much steeper and all fabrication processes are more critical....

 

[Abid]

The horizontal hole doesn't present a large compromise to the vertical forces, but the horizontal forces magnified by irregularities in a grass
strip are certainly going to cause more problems that maybe were not accounted for.. As far a spring is concerned, without knowing the measurements, I think it looks too small even if it didn't have a hole through it. A forward control rod could be very small and add immense strength to the system making it far more robust for rough fields. Maybe this was a fluke, a one time isolated incident totally brought on by a prior wheel issue. Lets hope so, but from this armchair quarterback position, I think it should have been executed better.
I have seen many solid AL struts, they are usually a wider section, quite heavy and the better ones are heat treated and forged.
lets compare apples to apples here, we are talking about relatively light duty equipment for a recreational vehicle, but it can still hit hard and be subject to shock loading. The machined heat treated suspended landing gear on a F-18 was massively designed for impact, no comparison...
They are usually on aircraft that land on paved runways and some have suspensions which changes the whole enchilada.
Of course proper engineering is the key ingredient, but again, why such a small margin of error???
Almost all of the DOD equipment I have designed has been able to sustain 5x the estimated working load.
I have had experience in off road racing with rail type vehicles and mountain bikes. Aluminum fails quickly when subjected to repetitive shock
loading. I have yet to see and off road race car made from aluminum, they are always steel and aluminum mountain bikes are generally only about 12% lighter than ChroMo and they break. When you can shave a few ounces from a racing bike and the MFG gives you a new one when it breaks, AL is great.
My friend and cohort in UAV projects started out making titanium mountain bikes in the 90's
Ti was/is the best option, but the cost is much steeper and all fabrication processes are more critical....

You say talk apples to apples. F-18 and UAV and mountain bikes and rally cars????
Aircraft spend 98% time in the air not the ground. These gyroplanes are not made to go land on 9” rocks in Alaska either. I am sure this guy is just flying from a normal grass field in France.

Anyway my point is there is a huge number of aircraft using 7075-T6 or 2024-T4 spring leaf landing gears in the real world and many like KitFox are made to fly from grass fields. Those landing gears however are usually not round at all. The reason is deflection front and back as compared to steel where one could get away with round. AR-1 landing gear is 7/8” thick and at the widest point 4” wide plate. It reduces front to back horizontal deflection.
Given that this Eclipse gear passed BUT testing it must have gone through dead drop tests. Those usually test 4 times normal working load. And 6 times working load for ultimate drop height with deformation allowed. So dimensionally this gear may be ok but it’s shape is not good for grass fields

 

[Aerofoam]

" The reason is deflection front and back as compared to steel where one could get away with round. AR-1 landing gear is 7/8” thick and at the widest point 4” wide plate. It reduces front to back horizontal deflection."

I think that is the whole point and my argument.....

 

[Abid]

I think that is the whole point and my argument.....

Well that's true. It also is just common sense. You cannot blindly copy a steel spring leaf gear system into Aluminum. You have to understand that Aluminum's modulus of elasticity is quite different and design around it which basically usually mean a different shape. Same for composite landing gear. Round usually isn't the way to go. Won't see many Aluminum undercarriage that are round. In fact, I know of none besides in gyroplane world and trike world. In trike world they are for lite trikes and it works ok there but still was designed by a non-engineer.

 

[Vance]

I think that is the whole point and my argument.....

Please help me understand the point of your argument.

I read your posts carefully and somehow I am still missing the point.

 

[Aerofoam]

Please help me understand the point of your argument.

I read your posts carefully and somehow I am still missing the point.

In a nut shell, it's my opinion based on empirical knowledge and hands on experience with materials,
that the small Dia. round AL sprung landing gear is not the best shape design or use of material.
Aluminum has poor fatigue properties and is not a great spring to begin with.
A round profile steel structure can be strong enough and can be an excellent spring.
The common aluminum landing struts that have been around for decades are large flat profiles which have some vertical elasticity, but are very solid fore and aft. They are also quite beefy compared to their steel counter parts.

The ELA landing gear may be adequately designed, but in my opinion it needs a larger margin of error/strength.
I believe it can be easily built to withstand many years of rough field use.
These things sort themselves out with time and I can't think of anything that couldn't be improved after some real world use...
I commented on other vehicle genres to point out that aluminum is rarely used for repetitive shock loading applications unless
it has a planned replacement period.
In the off road worlds, it was discovered that weight savings by using aluminum on key structural elements were not that great because
much less steel can be used in the same application and it will have a better performance and fatigue life.

 

[Vance]

In a nut shell, it's my opinion based on empirical knowledge and hands on experience with materials,
that the small Dia. round AL sprung landing gear is not the best shape design or use of material.
Aluminum has poor fatigue properties and is not a great spring to begin with.
A round profile steel structure can be strong enough and can be an excellent spring.
The common aluminum landing struts that have been around for decades are large flat profiles which have some vertical elasticity, but are very solid fore and aft. They are also quite beefy compared to their steel counter parts.

The ELA landing gear may be adequately designed, but in my opinion it needs a larger margin of error/strength.
I believe it can be easily built to withstand many years of rough field use.
These things sort themselves out with time and I can't think of anything that couldn't be improved after some real world use...
I commented on other vehicle genres to point out that aluminum is rarely used for repetitive shock loading applications unless
it has a planned replacement period.
In the off road worlds, it was discovered that weight savings by using aluminum on key structural elements were not that great because
much less steel can be used in the same application and it will have a better performance and fatigue life.

Thank you Aerofoam.

I like the aluminum landing gear on the AR1 and every aircraft I have flown with Grove aluminum landing gear worked well.

If you feel that aluminum is a poor spring material you probably don't like gyroplane rotor hub bars.

 

[Andino]

In the off road worlds, it was discovered that weight savings by using aluminum on key structural elements were not that great because
much less steel can be used in the same application and it will have a better performance and fatigue life.

Indeed. E-AB kit designers take note!

 

[Strike]

SWill be!! I much prefer my system, maybe not very elegant, maybe not aerodynamic ok mah........

 

[Aerofoam]

Thank you Aerofoam.

I like the aluminum landing gear on the AR1 and every aircraft I have flown with Grove aluminum landing gear worked well.

If you feel that aluminum is a poor spring material you probably don't like gyroplane rotor hub bars.

The Grove profile is probably more appropriate (Flat, not round) than the small round profile we were discussing.
Rotor hub bars are very beefy for the given loading and do not see the same kind of shock loading present when making impact
with solid objects. The rotor blades are effectively the elastic component and there are hopefully no stress risers present.

 

[Abid]

The Grove profile is probably more appropriate (Flat, not round) than the small round profile we were discussing.
Rotor hub bars are very beefy for the given loading and do not see the same kind of shock loading present when making impact
with solid objects. The rotor blades are effectively the elastic component and there are hopefully no stress risers present.

There is actually stress riser right as the blade transitions to the hub bar via clamping plates. Right there is a stress riser. That is where Trendek, AutoGyro and ELA blades usually start cracks and just as you saw in this landing gear, accelerated fatigue starts right around the vertical bolt hole. Obviously, the trick is to reduce the concentration of bending load right at the clamping plate around the bolt hole. If that concentrated loads can be spread over a bigger area, it would be fine.