Help needed

[Thunderdownunder]

Hi everyone

I need some help. One of my relatives was killed in a Helicopter accident last year and the air investigation reports have only come back with more questions than answers.

 

One thing that has come back which we are starting to research is how long will a helicopter engine run for after a disintegration? The chopper(EC120) was travelling at speed (Not known) when it impacted through dense foliage then hitting some large trees (1/2 meter diameters and a very solid wood) roughly 3 meters from their bases pushing them over from the roots and and on finally hitting the ground after basically disinegrating, the engine was still running for a period of time. Can anyone advise one how long an engine would run for after something as catstrophic as this? I was also told about half the air intake was covered at the point it reached the ground and that internally the the edges of the engines tubine blades were running white hot and their outer edge had cracked and sheared approximately a quarter inch from their circumference.

 

Unfortunately there was no radar tracking available to tell the airspeeds and weather conditions were cool with low level cloud which forced them to fly low but still good visability. We are still trying to work out why the Helicopter crash happened as there were no witnesses and no black box. What ever happened, happened very quickly as unfortunately had he turned an altered course to go back where he came from and a couple of miles from where he turned he crasehed. Also to note, had he crashed 2 meters to the left or right, he would have been in open fields.

 

Any advice will be greatly appreciated

[67november]

Hi TDU, don't know if anyone can help out with specific answers, only theories and conjecture.

 

as to the engine ? there are many variables that factor in as to how long it ran after impact. if indeed it was running prior to impact, it may have had a turbine wheel failure resulting in the ejection of turbune blades throught the engine and cowling. thus contributing to the cause of the wreck.

is the investigation complete? or is the info you have from the preliminay report?

 

i hope you can find your answers, and my condolencies to you and yours.

[Thunderdownunder]

Hi 67

Thanks for your quick response. We have a provisional report and agree that there is only speculation now as to what may have happened.... but any information is better than nothing as the provisional enquiry is pointing towards being inconclusive.

 

We are told that the engine was running prior to the crash and can disount the the ejection of turbine blades through the cowling as I am led to believe they were intact but missing the last quarter inch of their outer edges only. Also to note, and please, I am not a chopper pilot or mechanic so my terminology will not be technical, but the when the helicopter was moving through or within the trees and the rotors no longer had the abilty to turn, the engine had enough force to twist the rotor shaft, what looks like a 10 inch long piece of stainless steel fully back onto itself like a knot before the coupling let go and allowed the engine to run free for whatever period of time. These are several things that have been inconclusive in the report and we are finding hard to find answers

 

Please let me know your thoughs. I am quite willing to pass on information which may be of benifit and will assist in any scenarios you may have

 

Thanks

[ascott20]

Hey,

 

I'm not going to even try to speculate what caused the accident. Without knowledge of the type of flight condition he was in, we could discuss almost every type of emergency that could result in this type of accident, and they're numerous.

 

As for the engine, turbines are simple. As long as there is some amount of smooth airflow and fuel supplied, they will sustain the fire in the chamber. Also, the drive shaft could be torqued to shear if the rotor blades were allowed to contact a significant amount of trees that could cause them to abruptly stop. This would be similar to twisting a coke can by twisting at one end and holding the other steady.

 

The only thing I will say is that I doubt this was an engine related malfunction from what you have mentioned. Now for flight control systems, that's another issue. But like I said... there are lots of variables that need to be worked out before assumptions can be made.

[67november]

Hi 67

Thanks for your quick response. We have a provisional report and agree that there is only speculation now as to what may have happened.... but any information is better than nothing as the provisional enquiry is pointing towards being inconclusive.

Thanks

 

YW, TDU.

 

I can completely understand your frustration on the accident report as i've been there myself.

don't get your boxers in a bunch as it will take sometime to get the final report. prolly 2 to 3 years sometimes, if not longer. As you and your kin have joined the unfortuniate(sp?) club of loosing a family member via a helo wreck is a tuff thing to grasp at times. when i lost my uncle in a canadian crash it was more like loosing an older brother than an uncle. be paitent and be open to those who offer condolences.

 

be there for your family, it's VERY important.

[Witch]

I used to work on small turbines, and as long as fuel and air are available, it'll run.

 

Now the tricky part. If the compressor blades are damaged, and have injested debris, it may still run, but with decreased airflow into the combustion chamber. This may cause the turbine section to run hotter and even melt the turbine if it gets too hot.

 

I may have misunderstood, but you say the turbine blades were white hot and about a quarter inch shorter. This seems classic of a, for lack of a better term, full fuel flow scenerio. What I mean is that there is full fuel flowing into the engine and this causes it to burn more fuel than needed. As a result, the combustion flame it bigger and longer, and "shoots" into the turbine wheel. The wheel can't take these temperatures and deforms, melts, and flings metal.

 

The turbines I worked with often had "Hot Starts" where initial combustion caused excess fuel in the combustion chamber to ignite. The result was a ten to fifteen foot flame to shoot out of the exhaust. Not good for the turbine, but neat to see, especially at dusk.

 

Hope this helps a little.

 

Later

[Thunderdownunder]

Hi everyone

 

Thanks for all your input...its given us some direction to move towards.

 

Attached (I hope, if not let me know and I'll forward the photo) is a photo of the aft turbine which shows the degree of damage to the turbine blades. I'm told that they have definitely sustained excess heat but they have yet to open the casing to see inside, so everything is speculation at this point. The air intake is intact but the engine seems to be locked in position not allowing the aft turbine to rotate. Any ideas?

[Witch]

The air intake is intact but the engine seems to be locked in position not allowing the aft turbine to rotate. Any ideas?

My first thought about the turbine not rotating would be because it's siezed due to lack of lubrication. Maybe the oil flow was reduced or stopped, and while the engine kept running, the bearings got hotter and hotter, and finally siezed. That'd be my first guess.

 

Another thought would be the shaft bent or broke due to warpage from heat.

 

Without more info and looking at the engine, all I can do is speculate, and this is what that is; speculation.

 

Later.