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Mosquito accident in Odessa Florida
#41
Thank you both for your detailed and considered responses. The more we know about our systems the better off we will be in the long. I for one have learned tons I did not know when I started.

An automated ECU will certainly be a welcome addition.

And is it possible to prepare some type of tutorial on proper mapping in the meantime? Perhaps a workshop at the fly-in, since this seems to be a most critical part of the engine?
XE285 #1329 N869DJ
Start: June 2018
Done:  Sep 12, 2018  Sleepy 
AWC Issued: Sep 26, 2018  Big Grin  
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#42
For 285 owners that havent done so already, something I would recommend and have done on my machine is to connect the 'Check Engine' and 'Water Temp Warning' outputs of the ECU to lights on your dash.

Gary
XE285 in NZ
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#43
FWIW, I'm using the Pod 300, and the water temp is always in my scan now. I also have a thermocouple from the radiator going to my TC-3 with an alarm set.
XE285 #1329 N869DJ
Start: June 2018
Done:  Sep 12, 2018  Sleepy 
AWC Issued: Sep 26, 2018  Big Grin  
Reply
#44
I also have the dynojet with autotune (wideband o2) and the pod 300 for quick reference on the dash. Haven't had a chance to start tuning it yet though, only just began hover testing. I'm willing to share all my findings and eager to hear from everyone if or when they find things that work for them!
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#45
(01-28-2020, 08:08 PM)Dwight,Thanks for the thorough response.  I do have a couple of questions that I do not understand.  The first has to do with the auto.  It is mentioned that the rotor blades were not turning at all.  Would they really stop completely while descending? auto or not.  I am not helicopter trained.....yet.Separately, and I do understand that we will sometimes not know the actual cause, but the engine quit and did not seize but the piston was destroyed and it appears that this is caused by an over temp issue.  But you stated the ECU should have shut down the engine in the 2nd or 3rd limp mode before destruction (unless 600 degrees is the final limp mode).  Did the ECU fail?  How much time in seconds was it from first limp mode ~185 degrees to 600 degrees?  Any idea why there was an over temp issue?  What part in the cooling system failed?Just trying to understand.Travis Wrote:         In regards to the accident, the FAA and the NTSB are not required to come to a conclusion in any accident. I was not in the aircraft or even in the area at the time of the accident. If there is not clear evidence that shows a clear cause then it is only speculation and as any good agency should do is not conclude anything on speculation. The owner and operator of this aircraft was the only one there and I would consider him a friend. I received a call from the NTSB to help in the post-accident investigation, which as always I accepted. In a briefing from the FAA investigators they provided pictures and notes from the on sight investigation. They noted the pilot had said the engine stopped in flight with no indication of trouble. They also noted that upon impact the tail rotor and main rotor were not turning (zero rpm). Adam and I met up with the investigators at an FAA hanger on the east coast of Florida where the wreckage had been taken. Based on the information with which we started, was there a mechanical reason a proper autorotation had not been accomplished. All bearings and flight controls where inspected for function and or mechanical failure. It was determined no mechanical failures where found in this area previous to impact. We then turned to instrumentation - the electrical system was still intact and it powered up. Then all data from the data logs was down loaded and retrieved, turning our attention to the engine - we removed the spark plugs first to look for a lean or rich condition. We verified that the fuel system was intact and that fuel and oil was onboard in tanks prior to impact. Inspect all components to the engines cooling system. We disassembled the engine to inspect the damage on internal components caused by the engine stoppage.
      Conclusions are based on facts collected over the years in some cases, but most were based on the facts collected in the investigation. It is not unusual for post-accident data to not match up with witnesses or onboard survivor accounts. Call it the fog of war or being overwhelmed at the time, it happens to all of us including myself. After a mechanical failure in flight - with flight controls intact - a proper autorotation would result with main rotor rpm still turning between 80 to 110 percent upon contact with LZ . In this case it did not happen and the reason is unknown but it did not appear to be mechanical. The inspection of the spark plugs indicated a slightly rich condition but not excessive and no indication it would cause an engine shut down. Color indications inside of the exhaust tubes were the same as the plugs. The fuel cell still had fuel in it as did the fuel lines and injectors indicating fuel was available to the engine components. Internally on the engine one quarter of one piston had melted and broke off the piston head. The tops of both pistons had heat detonation marks on them. The engine showed no signs of seizing but exhibited scoring on the cylinder that the piston was damaged. All cooling hoses where melted off the engine leaving some melted residue at the hose clamps. The hoses are rated up to 275 degrees with operating range between 195 to 200 degrees. The data retrieved from the electronic flight logs indicated coolant (engine) temperatures reached as high as 600 degrees before data logging was terminated. Why the engine quit can be a couple reasons: the current ECU is equipped with three limp modes or self-preservation modes. The first is tripped at just under 190 degrees which the ECU will over fuel by 10 percent and retard the timing by ten percent. In this first limp mode the helicopter is still flyable which I have done several times but the engine will run quite rough. If the conditions persist the second limp mode will continue to add fuel and retard timing even more. If it is left unchecked the third mode will force the engine to an idle and the operator can do nothing to change this condition. We can only speculate at this point why the engine quit. It could have gone into this final limp mode or the piece that came off the piston could have lodged in the rotating assembly stalling the engine. The final answer we may never know as well as what caused the engine to overheat in the first place. But, as the data showed from the time the engine overheated, tripping the warning at 185 degrees, to the point that all hoses melted off and the indicator reached 600 degrees, should have been ample time to react. The main reason we volunteer to help in these investigations, at our own expense, is to see or find failures that can be improved upon. If we were trying to hide something as indicated by some, the FAA is there for the inspection and to keep that from happening, (as they should). In the end, no aircraft can guarantee not fail at some point - nor the pilot, as in the news today where a very tragic S-71B helicopter accident in California took all souls onboard. This is one of the most sophisticated helicopters and has been in production for many years. Whether this accident was caused by mechanical failure or pilot error - it only reminds us of the risk all of us take each day including driving down the highway.
        In regards to the 285 engines and seizing we have repeatedly leaned this engine out to the point they quit running and have never had one seized up. There are two reasons for this: one being liquid cooled keeps the thermal dynamics more even throughout the engine in its operation (no hot spots). The second is the oil injection continually injects oil into the engine regardless of a lean condition making seizing much less likely. To say you cannot seize this engine would be an over statement but we have not to date seen it happen. For these reasons liquid cooled fuel oil injected two strokes have proven to be as reliable as there four stroke counter parts.
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