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EC120

Old 28th Aug 2009, 19:10
  #501 (permalink)  
 
Join Date: Aug 2002
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EC say the VEMD does not lie.
The 4-digit T4 recorder on the VEMD over-limit page is better than the 3-digit original, because once you went past 999 there was no knowing what the upper figure was. I suspect in your case such a high and long overtemp meant a whole new turbine module. The damage from such an overtemp will probably have been obvious to Turbomeca engineers.
The only known snag with the VEMD is a spurious NR exceedance (over the high limit) for 000 secs; this is caused by a voltage spike (turning on and off the landing lamp could do it), should have ben rectified by an SB upgrade, but may still apparently occur. AFAIK, this is the only VEMD Over Limit warning where your Maintenance Org can let you fly without an engineeer first inspecting.
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Old 28th Aug 2009, 19:13
  #502 (permalink)  
 
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Not false Temperature readings, but Rotor RPM and Torque.
Luckily this readings where to high to believe and we could proof with GPS track, that at the moment that occurred, we passed a high intensity transmitter station which caused the VEMD to go mental.
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Old 28th Aug 2009, 20:27
  #503 (permalink)  
CVR
 
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120

Spurious NR exceedances usually pop up if you fly close to high tension power lines......but never heard of a false over temp reading.
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Old 30th Aug 2009, 02:12
  #504 (permalink)  
 
Join Date: Jun 2009
Location: Fleetwood, PA
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yeah, i've seen the nr overlimits many times where we fly in pa and nj due to the towers. its just poor timing on this overtemp. our head mechanic who read the vemd after the other pilot found an overtemp limit notice has left the company. other pilot swears he never overtemped, engine sent out, partial disassembly, large bill to pay. i'm a 200hr pilot going against a 20,000 hr pilot of which 3000 is in rotorcraft. he says he did not overtemp it and the vemd lied. (overtemp clearly showed up on his flight number, not mine) eurocopter was not told to investigate, only told there was an overtemp and do what the have to do. real crappy situation
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Old 30th Aug 2009, 04:24
  #505 (permalink)  
 
Join Date: Jul 2006
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Backing up what the previous posts have noted about the NR indications around wires and towers. I have the Service Bulletin here if you need it.

I know of 3 previous over temps in EC120's all associated (so I'm told) with fitment of the dual controls. The next start if they are incorrectly fitted will guarantee an over temp.
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Old 30th Aug 2009, 15:18
  #506 (permalink)  
 
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2per
Are you saying the controls produce a erroneous reading? or there is a true OT due to duals being fitted
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Old 31st Aug 2009, 03:53
  #507 (permalink)  
 
Join Date: Jul 2008
Location: melbourne
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VEMD

Wow 1100 for 11 sec, Thats a crazy over temp. Sounds odd how can the pilot not know and for so long, was it in flight or on a start, was it cooked in the end? I have noticed that the EC120 has a few little Bugs. If your not careful on a start it can bite you. 1 out of 50 starts for me and for no reason the T4 sky rockets, Battery good and residual temp under 175 degrees always. Im now modulating the start to be safe.

False NR reading i have had this happen twice, man its scary when you land and shutdown you see that Overlimit Detected, your heart just sinks. We had the resister mod done to the NR indicator and sure enough after that another NR over limit, no warning no indication, seems to be more going on here.

Whats going on with these VEMD's any other aircraft have problems AS350 or Ec130? Damn computers just cant trust them, bring back the trusty gauges.
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Old 3rd Sep 2009, 17:33
  #508 (permalink)  
 
Join Date: Jun 2009
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i'm not sure what he did. he denies doing anything wrong and the mechanic that did the investigation after the overlimit was noticed on the vemd has left the company. can avionics be powered up with no engine installed? i want to read the vemd report on the flight and get the facts. i dont' think it lied. i think the only lies the vemd puts out are the nr ones with transmission towers. i hear you on the gauges, however, with another pilot flying this thing, i'm glad there is a vemd, it gets rid of any trust issues.
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Old 4th Sep 2009, 15:55
  #509 (permalink)  
 
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Make sure the starter generator wires are not touching(put some masking tape over them individually to prevent them touching) and you can switch on power as long as obviously nothing else electrically is removed and or disturbed that could cause problems. The maintenance page will be accessable where you can either check the flight report the over limit was detected and check the over limit page and see what it counted accumulatively.

11s is a very long time for a engine to be at that T4. one must almost be standing outside the aircraft during starting not looking anywhere or hearing anything and just push the lever regardless. Why is the engine removed? Is it for checks after the incident?

Just a thought. Make sure your engineer does the T4 harness and calibration check when the engine is refitted. It might be that one of the anumel/chromel probes are defective and thus registered a higher resistance causing the high indication. Also check the airframe loom from the plug to the VEMD for correct resistance.

Will be interesting to know the outcome.
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Old 5th Sep 2009, 06:20
  #510 (permalink)  
 
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Generator

Anyone had this on there machine, i have noticed a lot of Generator overlimits on the machine i fly lately on starts. As soon as that limit is diplayed i hit the button to have a look what the generator is doing and this morning i see 170Amps and decreasing to the normal, this happens on only some starts not all. I wonder whats going on to surge the generator so much any ideas?
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Old 5th Sep 2009, 06:35
  #511 (permalink)  
 
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cleartorotate, in what phase does this occur? Is it just after start as the gennie comes online at gnd idle or at flt idle? Do you start with a GPU or not? If you do use GPU does it happen with a batt start as well as a GPU start? During the start what is the voltage drop ie 24v before start dropping to 19v? Do you start with the "GEN" selected? Sorry for the questions but there are a few variables here.
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Old 5th Sep 2009, 07:30
  #512 (permalink)  
 
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Generator

This happens on a normal start no GPU.
Voltage starts at around 24.8v and drops to about 19v
Generator is on during start
The OL comes on just after the start cycle and VEMD switches to Flight Display Ground Idle.

Seems to be happening when Gen comes online. Spikes the amps and drops to normal operating amps.

I hope that makes more sence now.
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Old 5th Sep 2009, 08:31
  #513 (permalink)  
 
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Last question. Does she do the same if you do a GPU start?
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Old 5th Sep 2009, 09:09
  #514 (permalink)  
 
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Generator

Well i have not tried a gpu start, so dont know the answer to that..
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Old 5th Sep 2009, 12:16
  #515 (permalink)  
 
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It would be interesting to try a GPU start and see. That will either point to the battery or exclude it. I have had batteries with normal voltage indication not capable of handling a start due to the amps being drawn and that normally is caused by a problematic cell so maybe if she does not do it with the GPU it could be the battery drawing the amps from the gennie to recover it's charge as soon as the gennie comes online?
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Old 5th Sep 2009, 13:50
  #516 (permalink)  
 
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How far can the voltage safely drop on start? I have heard 15v but am not sure if that is OK.

John
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Old 5th Sep 2009, 16:00
  #517 (permalink)  
 
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18 volts is the safe norm with 16v as an absolute min in my experience. Have seen them handle below that as far as 12 volts, but it all depends on the state of the battery and what is the reason for it not being able to sustain voltage. If the battery for instance was completely rundown at some point and then just recharged instead of deep cycled you are playing with fire as it could be battling to produce sufficient amps(voltage might still be fine) to drive the starter at a rate at which the N1 can increase sufficiently and thus airflow to what the FCU expects inducing the fuel. If it is a first time for the volts to run that low cause the batt was just on too long before start or other equipment driven, you can getaway with it and then sometimes you might see the warning when the gennie takes over as the batt draws the current from it to reinstate it's charge-not electrically inclined so technically the explanation will not be correct but this is how I have understood it in the field.
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Old 5th Sep 2009, 17:18
  #518 (permalink)  
 
Join Date: Nov 2005
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We have a problem with our GEN light stays on, we replaced the generator, main electric box, even the lacu, but the problems still exists. We tried our parts on another EC120, no problem. Checked all the cabling for grounding/corrosion issues, nothing. Note the helicopter had been sitting in the hanger for 5 months.

Any ideas ......
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Old 6th Sep 2009, 18:05
  #519 (permalink)  
 
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After standing that long, have you tried to swop the ASU's in the rear baggage bay rack with the other machine?
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Old 7th Sep 2009, 08:32
  #520 (permalink)  
 
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After standing that long, have you tried to swop the ASU's in the rear baggage bay rack with the other machine?
Yes, we did.
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