As 350 B3
Join Date: Jul 2004
Location: Huntsville AL
Age: 51
Posts: 139
Likes: 0
Received 0 Likes
on
0 Posts
I'm a bit getting in on this but I think I can help.
First, the B3 and B4 are both FADEC equiped although one is single channel and one dual (the newer B3s are in fact dual channel as well). The FADEC system uses a few things for the start sequence. It uses OAT to set a basic fuel flow law. Then it indexes T4 to N1 to modify that law and effect the start. Basically speaking it adjust the fuel flow to get a certain T4 for a certain N1 speed. Now most folks used to think that it would automatically handle a hot start situation. THIS IS NOT TRUE!! with the laws as stated above it had a limited authority over fuel flow and you could still have a hot start. I have seen engines removed for going to over 999 degrees T4 when the pilot did not react and abort the start.
Now with the new TU standard DECU software (TU143 for the single channel and TU144 for the dual channel) it will automatically abort the start if it reaches 865 degrees T4. So with the old system it would not do anything to hot start itself but if you dumped in a bucket of fuel it wouldn't stop it either. With the new software it will close the stop electrovalve if it hits 865 which SHOULD cool things off but it also shuts off the starter...so if there is still fuel in the chamber you will have to hit the crank button to clear it out.
Now as far as cranking to reduce residual temp in the engine prior to a start, I don't see why you would need to. The Arriel engine (as well the Arrius) both initiate a start with fuel being delivered right away. They don't spool up to a certain speed before introducing fuel like C-20 types. Below about 10% N1 the only fuel going into the engine should be through the start injectors. These injectors will only supply enough fuel to get about 200-300 degrees T4.
So if the T4 is indicating say 200 degrees and you want to start and you do a ventilation to reduce temp with cool airflow you are going to cool off the turbine wheel and blades and then as soon as you start you will hit them with 200-300 degrees right away from the start injectors. So if you are at only 200 then you should be able to go ahead and start and the FADEC laws will adjust the fuel flow as needed to get things moving correctly. No need to drain the battery bringing the temp down and then adding it right back in again.
Now this is for the FADEC equipped engines. If you are flying an EC120 or an older 350 without FADEC then you are the only one modulating fuel flow during the start. In the case of the EC120 which has gotten a reputation for hot starts it is probably best to get the temp down first, otherwise you will need to be Johnny on the spot with the twist grip to avoid overtemp.
Hope it helps!
Max
First, the B3 and B4 are both FADEC equiped although one is single channel and one dual (the newer B3s are in fact dual channel as well). The FADEC system uses a few things for the start sequence. It uses OAT to set a basic fuel flow law. Then it indexes T4 to N1 to modify that law and effect the start. Basically speaking it adjust the fuel flow to get a certain T4 for a certain N1 speed. Now most folks used to think that it would automatically handle a hot start situation. THIS IS NOT TRUE!! with the laws as stated above it had a limited authority over fuel flow and you could still have a hot start. I have seen engines removed for going to over 999 degrees T4 when the pilot did not react and abort the start.
Now with the new TU standard DECU software (TU143 for the single channel and TU144 for the dual channel) it will automatically abort the start if it reaches 865 degrees T4. So with the old system it would not do anything to hot start itself but if you dumped in a bucket of fuel it wouldn't stop it either. With the new software it will close the stop electrovalve if it hits 865 which SHOULD cool things off but it also shuts off the starter...so if there is still fuel in the chamber you will have to hit the crank button to clear it out.
Now as far as cranking to reduce residual temp in the engine prior to a start, I don't see why you would need to. The Arriel engine (as well the Arrius) both initiate a start with fuel being delivered right away. They don't spool up to a certain speed before introducing fuel like C-20 types. Below about 10% N1 the only fuel going into the engine should be through the start injectors. These injectors will only supply enough fuel to get about 200-300 degrees T4.
So if the T4 is indicating say 200 degrees and you want to start and you do a ventilation to reduce temp with cool airflow you are going to cool off the turbine wheel and blades and then as soon as you start you will hit them with 200-300 degrees right away from the start injectors. So if you are at only 200 then you should be able to go ahead and start and the FADEC laws will adjust the fuel flow as needed to get things moving correctly. No need to drain the battery bringing the temp down and then adding it right back in again.
Now this is for the FADEC equipped engines. If you are flying an EC120 or an older 350 without FADEC then you are the only one modulating fuel flow during the start. In the case of the EC120 which has gotten a reputation for hot starts it is probably best to get the temp down first, otherwise you will need to be Johnny on the spot with the twist grip to avoid overtemp.
Hope it helps!
Max
Join Date: Dec 2003
Location: Australia
Posts: 72
Likes: 0
Received 0 Likes
on
0 Posts
Never had any probs with either the B4 or the 350 (2B1) with start up straight after a shutdown but for memory there is no mention of cranking the engine prior to start as with say a B206 to reduce temp's, but if she gets hot Abort Start (switch off), Boost Pump off, GEN off and crank.
The EC120 is a little different but still reasonable just keep an eye on the procedings....modulate.
As with all of em stay focused.
does anyone know if they (the frenchies) intend uping the 120.....wider chord blades and squuzing a little more power out of the donk?
It would be well worth it a great little helicopter.
The EC120 is a little different but still reasonable just keep an eye on the procedings....modulate.
As with all of em stay focused.
does anyone know if they (the frenchies) intend uping the 120.....wider chord blades and squuzing a little more power out of the donk?
It would be well worth it a great little helicopter.
Join Date: Feb 2003
Location: Canada
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Further to the above (re: crank for engine fire during start & also for other maintenance duties), Eurocopter states that the "CRANKING" function as:
"This function is independent of the starting function; it is used to cool the air duct and drain out any fuel remaining inside after an aborted start."
For an engine relight in flight, cranking also is not used - NG has to be below 5% for the 2B engine prior to selecting ON on the starter switch (otherwise it will not start), however on the 2B1, the switch is turned ON and will automatically start once the NG goes below 17%.
"This function is independent of the starting function; it is used to cool the air duct and drain out any fuel remaining inside after an aborted start."
For an engine relight in flight, cranking also is not used - NG has to be below 5% for the 2B engine prior to selecting ON on the starter switch (otherwise it will not start), however on the 2B1, the switch is turned ON and will automatically start once the NG goes below 17%.
AS 350 B3 amber gov light
Our one B3 (Arriel 2B) keeps getting an amber GOV that comes on after 15min flying and stays on until shut down and then it goes on when going from gnd to flt idle.
It's got everyone stumped and we need help...
Anyone have any ideas
It's got everyone stumped and we need help...
Anyone have any ideas
Join Date: Apr 2012
Location: Italy
Age: 36
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
Got the same problem a couple of times, check rotor brake, normally is the micro switch malfunction that prevent the GOV to work correctly.
Troubleshoot it, first to touch everything else. I know for sure that RMM says something about that problem. Try to look in it...
Troubleshoot it, first to touch everything else. I know for sure that RMM says something about that problem. Try to look in it...
Join Date: Jun 2009
Location: In the desert southwest
Posts: 181
Likes: 0
Received 0 Likes
on
0 Posts
had it recently
Turned out to be the collective position potentiometer, or something like that. Took our mechanic about 4 hours to replace the faulty one. It is located under the floor inside the right stowage compartment near the bulkhead, front end. It is a small part but a bugger to replace. He had to remove the O2 system tank and hardware first and then remove the faulty unit and solder all the wiring into the new one.
Hope that helps.
Cheers
Hope that helps.
Cheers
This is a known issue with some multi engine aircraft. The fadec gets fooled into either delivering max power or minimum torque on the affected engine until the coll is repositioned Not fun either way.
Last edited by Sir Korsky; 22nd May 2012 at 01:44.
Thanks for the help so far...I've passed all that on and I'm now getting the whole story out from the engineers:
"not only does it give you a gov light but the engine does not go from flight idle to ground idle and some time's does not shut the engine down if you select engine off."
"not only does it give you a gov light but the engine does not go from flight idle to ground idle and some time's does not shut the engine down if you select engine off."
Join Date: Jun 2007
Location: foot of a mountain
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
We often turn to the engine immediately if we see a GOV to look for the fault. We forget the VEMD is "Vehicle" and "engine" and if 1 of your screens fail you will get a flashing or solid GOV dependant on mod status and so the sensors on the airframe(interface) and leading to the VEMD will also activate a GOV. One I had was for pitot static gen to the VEMD vs what the DECU send and it set the GOV on due a discrepency.
