Agusta AW139
Ignition keeps operating until the EEC senses NG of 50% +/- 1%. Not on time.
Edit: Actually that is only true for Auto Mode. Manual is NG 49% +/- 1%.
Edit: Actually that is only true for Auto Mode. Manual is NG 49% +/- 1%.
Last edited by noooby; 24th Nov 2014 at 22:32.
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Ignition keeps operating until the EEC senses NG of 50% +/- 1%. Not on time.
Edit: Actually that is only true for Auto Mode. Manual is NG 49% +/- 1%.
Edit: Actually that is only true for Auto Mode. Manual is NG 49% +/- 1%.
AW139 EASA b1.3 Training Manual. I'll have a look in the pilot ground school notes later.
Have a look at the MFD next time you start. IGN and START captions will go out together at 50% in Auto (commanded by EEC) or 49% in Manual (Commanded by GCU).
Have a look at the MFD next time you start. IGN and START captions will go out together at 50% in Auto (commanded by EEC) or 49% in Manual (Commanded by GCU).
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I agree that the captions are there, but that is no guarantee that the ignitors are firing.
Noooby, thanks very much for the reference, that was what I was looking for.
In that same manual, does it say why the 10 sec limit is quoted in the RFM? If I recall from my 212 days there is a certain amount of fuel pressure from the high pressure pump that is required to open the flow divider, so I'm thinking that AW/Pratt is saying that if by the time you reach 10 secs without light up then the flow divider has not opened.
Am I on the right track? I don't go along with the too much fuel in the can theory, if that was the case selecting the mode switch to off at that critical moment just as it lights would be a sure fire ( pun intended) way to an exhaust fire or hot start.
Cheers
Noooby, thanks very much for the reference, that was what I was looking for.
In that same manual, does it say why the 10 sec limit is quoted in the RFM? If I recall from my 212 days there is a certain amount of fuel pressure from the high pressure pump that is required to open the flow divider, so I'm thinking that AW/Pratt is saying that if by the time you reach 10 secs without light up then the flow divider has not opened.
Am I on the right track? I don't go along with the too much fuel in the can theory, if that was the case selecting the mode switch to off at that critical moment just as it lights would be a sure fire ( pun intended) way to an exhaust fire or hot start.
Cheers
In my experience, Non-PC Plod has hit the nail on the head, as it should be assumed that as a result of the failure of the engine to light-up, un-burnt fuel may have collected in the combustion chamber and gas generator case, thereby increasing the risk of a hot start during any subsequent start attempts.
Following an aborted engine start the RFM calls for a dry motoring run, post a drain period, before attempting another start does it not?
Following an aborted engine start the RFM calls for a dry motoring run, post a drain period, before attempting another start does it not?
DRY MOTORING PROCEDURE
Following an aborted start shutdown, perform the following procedure allowing a 30 seconds fuel drain period before restarting. The procedure is used to clear internally trapped fuel and vapor:
Following an aborted start shutdown, perform the following procedure allowing a 30 seconds fuel drain period before restarting. The procedure is used to clear internally trapped fuel and vapor:
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I'm afraid you are mixing apple and oranges there.....I'm not talking about an aborted start and subsequent restart. That same procedure is in place whether you abort the start after 5 secs or 25 secs.....
I'm wondering why the 10 sec limit on light up, which is right there in the RFM along with blades not turning, etc.....
I'm still thinking that they are assuming that if it has not lit by then the flow divider has not and will not open so it will not get any fuel.......just looking for where that is written ( or not) not looking for opinions, looking for proof just as noooby gave me on the ignitors.
I'm wondering why the 10 sec limit on light up, which is right there in the RFM along with blades not turning, etc.....
I'm still thinking that they are assuming that if it has not lit by then the flow divider has not and will not open so it will not get any fuel.......just looking for where that is written ( or not) not looking for opinions, looking for proof just as noooby gave me on the ignitors.
Outwest, you might be better off asking Pratt, than asking Agusta.
The Ignition caption does mean that the igniters are being told to fire. That is part of the logic through the EEC. If there is no Ignition caption, then the message has not been sent to the igniters to fire. It isn't just a message, that appears between certain RPM's, it is part of the circuit to the igniters.
I've looked throught he QRH and the Type Rating Ground School, but can't find any reason there. You'd need to talk to a Flight Instructor at Agusta, or to Pratt.
And while the box or both igniters may have failed (very unlikely), they are checked at scheduled intervals by the mechanics.
The Ignition caption does mean that the igniters are being told to fire. That is part of the logic through the EEC. If there is no Ignition caption, then the message has not been sent to the igniters to fire. It isn't just a message, that appears between certain RPM's, it is part of the circuit to the igniters.
I've looked throught he QRH and the Type Rating Ground School, but can't find any reason there. You'd need to talk to a Flight Instructor at Agusta, or to Pratt.
And while the box or both igniters may have failed (very unlikely), they are checked at scheduled intervals by the mechanics.
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10 second light-off
I would not of thought that you abort a start based on 'no fuel' scenario...especially when there is starter limitations way above this limit which would permit you to continue motoring.
In any case I recently spoke with a good friend of mine who is a PWC Tech Rep and he stated the 10 second limit is for the exact opposite...if you have more than 10 seconds worth of fuel in the engine before light-off than expect a hot start. Another words the limitation is there to prevent hot starts.
Unfortunately I don't have any reference for this and would not recommend to test the theory!
SS
In any case I recently spoke with a good friend of mine who is a PWC Tech Rep and he stated the 10 second limit is for the exact opposite...if you have more than 10 seconds worth of fuel in the engine before light-off than expect a hot start. Another words the limitation is there to prevent hot starts.
Unfortunately I don't have any reference for this and would not recommend to test the theory!
SS
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Well not to take away from a P&W tech rep but that is simply not true. Fuel is not being dumped into the can from the very first selection of idle on the mode switch.So there is not 10 secs worth of fuel.
I again go back to my 212 days. If memory serves passing thru 10% ( maybe it was 12) Ng, we rolled the throttles on and waited for light up. I remember flying with a pilot one time who set the throttles to idle and then hit the starter. I was shocked and assumed that we would get a hot start. Nothing out of the ordinary happened, as the Ng went thru about 12% the light up was normal.
So again, I go back to the flow divider and the pressure required to open it.
Geoff.....where are you on this?
I again go back to my 212 days. If memory serves passing thru 10% ( maybe it was 12) Ng, we rolled the throttles on and waited for light up. I remember flying with a pilot one time who set the throttles to idle and then hit the starter. I was shocked and assumed that we would get a hot start. Nothing out of the ordinary happened, as the Ng went thru about 12% the light up was normal.
So again, I go back to the flow divider and the pressure required to open it.
Geoff.....where are you on this?
It doesn’t matter that its 10 seconds, 8 seconds or 6 seconds worth, it’s the build-up of un-burnt fuel without ignition that is the cause for concern.
Fine detail aside, initial Ng acceleration results in a rise in metered HP fuel to the flow divider, which when unseated, schedules metered fuel to the primary and secondary fuel nozzle manifolds (as a function of primary manifold pressure) via separate spring loaded valve ports.
As the twin igniters are positioned adjacent to Primary and not Secondary nozzles, and that the Secondary nozzle valve port opens at a higher pressure than for Primary nozzles, were the Secondary valve to open before the Primary, increased fuel flow would enter the combustion chamber away from the igniters, thereby increasing the likelihood of a hot start, which would explains why many engine types have this 10 second limitation for indication of a light-up.
Both valves ports should be open with all nozzles flowing by around 35% Ng, and as I recall, close to idle speed is achievable with just min fuel flow (i.e. before compressor discharge air influences P3 bellow/fuel valve positioning).
Noting your 212 days, there is no HP fuel flow without Ng rotation, so initially no fuel pressure to open up and surge through the flow divider. Additional metered fuel flow in excess of min fuel flow settings is a function of P3, and as P3 is directly proportional to Ng speed, setting the condition levers to idle or even flight before engine start will not result in a hot start, as there is no input reference to increase fuel flow to the flow divider much before idle speed is obtained. (PPRuNer’s - Please do not try and disprove this theory at home
).
Fine detail aside, initial Ng acceleration results in a rise in metered HP fuel to the flow divider, which when unseated, schedules metered fuel to the primary and secondary fuel nozzle manifolds (as a function of primary manifold pressure) via separate spring loaded valve ports.
As the twin igniters are positioned adjacent to Primary and not Secondary nozzles, and that the Secondary nozzle valve port opens at a higher pressure than for Primary nozzles, were the Secondary valve to open before the Primary, increased fuel flow would enter the combustion chamber away from the igniters, thereby increasing the likelihood of a hot start, which would explains why many engine types have this 10 second limitation for indication of a light-up.
Both valves ports should be open with all nozzles flowing by around 35% Ng, and as I recall, close to idle speed is achievable with just min fuel flow (i.e. before compressor discharge air influences P3 bellow/fuel valve positioning).
Noting your 212 days, there is no HP fuel flow without Ng rotation, so initially no fuel pressure to open up and surge through the flow divider. Additional metered fuel flow in excess of min fuel flow settings is a function of P3, and as P3 is directly proportional to Ng speed, setting the condition levers to idle or even flight before engine start will not result in a hot start, as there is no input reference to increase fuel flow to the flow divider much before idle speed is obtained. (PPRuNer’s - Please do not try and disprove this theory at home
).
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Lost in last week's tsunami of industry news:
Former AH175 client Héli-Union the launch customer of 7-ton AW139
I/C
Former AH175 client Héli-Union the launch customer of 7-ton AW139
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noooby,
Didn't want to quote HELiDATA too much – it's a great resource, and deserves subscribing to – but in short it reports that Héli-Union "has deferred 'indefinitely' its order for the H175," with ten 7-ton MGW AW139s ordered.
I/C
Didn't want to quote HELiDATA too much – it's a great resource, and deserves subscribing to – but in short it reports that Héli-Union "has deferred 'indefinitely' its order for the H175," with ten 7-ton MGW AW139s ordered.
I/C
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AW 139 check list
another question for AW139 operators....
The QRH provided with the helicopter does not have the checks for the optional equipment.
As any optional equipment has dedicated checks, does anyone of you made a proper check list including all checks for all the equipment?
For example we have hoist..hook...emergency floats...flir....trakkabeam....but as they are not mentioned in the checks, some pilots check them only where they are supposed to use them during the flight, looking directly to the RFM, not in every flight.
What do you do?
The QRH provided with the helicopter does not have the checks for the optional equipment.
As any optional equipment has dedicated checks, does anyone of you made a proper check list including all checks for all the equipment?
For example we have hoist..hook...emergency floats...flir....trakkabeam....but as they are not mentioned in the checks, some pilots check them only where they are supposed to use them during the flight, looking directly to the RFM, not in every flight.
What do you do?
RepVolo...
As a professional pilot you are expected to check your equipment, especially your mission critical equipment during your preflight inspection at the beginning of your shift, not just before use.
You can add those checks to those listed as pre-flight or "hangar" checks, since they are best done with an EPU connected to the helicopter.
PM me for additional guidance.
As a professional pilot you are expected to check your equipment, especially your mission critical equipment during your preflight inspection at the beginning of your shift, not just before use.
You can add those checks to those listed as pre-flight or "hangar" checks, since they are best done with an EPU connected to the helicopter.
PM me for additional guidance.