AW139 Battery start procedure
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AW139 Battery start procedure
For battery start procedure, there is a NOTE as follows;
If engine N°2 is to be started first, set BUS TIE switch to ON and confirm MAIN BUS 2 voltage is not below 23V.
I thought ENG 2 Starter/Generator was powered by DC MAIN BUS 2, so we got to set BUS TIE SW to ON to start No.2 ENG first, but it is described in RFM 3-51 that ENG 2 IGNITER & START is powered by DC ESS BUS 2.
I wonder if we can start No.2 ENG first with BUS TIE SW in AUTO position in battery start.
If engine N°2 is to be started first, set BUS TIE switch to ON and confirm MAIN BUS 2 voltage is not below 23V.
I thought ENG 2 Starter/Generator was powered by DC MAIN BUS 2, so we got to set BUS TIE SW to ON to start No.2 ENG first, but it is described in RFM 3-51 that ENG 2 IGNITER & START is powered by DC ESS BUS 2.
I wonder if we can start No.2 ENG first with BUS TIE SW in AUTO position in battery start.
From the AW tech notes
If the bus tie is left in auto in the situation you describe, the no2 starter gen will not be powered.
ELECTRICAL POWER – MAJOR COMPONENTS
STARTER-GENERATOR
Two 9-kW DC starter-generators are used to start the relevant engine and, when the engine is running, to produce DC power.
The starter-generator no. 1 is connected to the MAIN BUS 1; the starter- generator no. 2 is connected to the MAIN BUS 2.
STARTER-GENERATOR
Two 9-kW DC starter-generators are used to start the relevant engine and, when the engine is running, to produce DC power.
The starter-generator no. 1 is connected to the MAIN BUS 1; the starter- generator no. 2 is connected to the MAIN BUS 2.
BATTERY STARTING
The following diagrams represent the sequence of actions for a normal battery starting of the engines (steps 1 to 8 on the simplified schematic diagram). In this example engine no. 2 is started first.
Refer to AW139-RFM-4D – Section 2 for Normal Procedures.
STEP 1
Helicopter is parked and ready for flight. All switches are in the safe position.
STEPS 2 TO 3
When BATTERY MASTER switch is set to ON, Main and Aux Batteries are connected to ESS BUS 1 and ESS BUS 2 thus providing power to the rotorcraft essential loads.
The BATTERY MASTER switch at ON also enables the BATTERY MAIN and the BATTERY AUX switches.
When BATTERY MAIN switch is set to ON, the Main Battery is connected to MAIN BUS 1 (Main Battery contactor K3 closes) which is then also powered. When BATTERY AUX switch is set to ON, the Auxiliary Battery is connected to MAIN BUS 2 (Aux Battery contactor K4 closes), but MAIN BUS 2 is notpowered because of the reverse biased diode (CR5) which only permits recharging of the Auxiliary battery from MAIN BUS 2.
When GEN 1 and GEN 2 switches are set to ON they give an input to the relevant GCU so that the GCU will put the relevant generator on-line as soon as conditions permit.
23 VOLT CHECK
Before attempting starting the engine on batteries, the pilot has to check that the involved MAIN BUS voltage is not less than 23 V.
STEP 4
As in this example the engine no 2 is started first, the BUS TIE switch must be set to ON to power MAIN BUS 2.
BUS TIE Contactor closes thus connecting MAIN BUS 1 and MAIN BUS 2.
Refer to AW139-RFM-4D – Section 2 for Normal Procedures.
STEP 1
Helicopter is parked and ready for flight. All switches are in the safe position.
STEPS 2 TO 3
When BATTERY MASTER switch is set to ON, Main and Aux Batteries are connected to ESS BUS 1 and ESS BUS 2 thus providing power to the rotorcraft essential loads.
The BATTERY MASTER switch at ON also enables the BATTERY MAIN and the BATTERY AUX switches.
When BATTERY MAIN switch is set to ON, the Main Battery is connected to MAIN BUS 1 (Main Battery contactor K3 closes) which is then also powered. When BATTERY AUX switch is set to ON, the Auxiliary Battery is connected to MAIN BUS 2 (Aux Battery contactor K4 closes), but MAIN BUS 2 is notpowered because of the reverse biased diode (CR5) which only permits recharging of the Auxiliary battery from MAIN BUS 2.
When GEN 1 and GEN 2 switches are set to ON they give an input to the relevant GCU so that the GCU will put the relevant generator on-line as soon as conditions permit.
23 VOLT CHECK
Before attempting starting the engine on batteries, the pilot has to check that the involved MAIN BUS voltage is not less than 23 V.
STEP 4
As in this example the engine no 2 is started first, the BUS TIE switch must be set to ON to power MAIN BUS 2.
BUS TIE Contactor closes thus connecting MAIN BUS 1 and MAIN BUS 2.
twinbird, which battery is used for starting the engines and where is it located?
Answer: Main Battery and it is on the #1 side. So you need Bus Tie ON as you are cross feeding electrical power to start #2 on battery. If you set Bus Tie to AUTO and the voltage drops below a prescribed value, the Bus Tie will disconnect and the starter will disengage.
Battery start is always quicker on #1 engine. Less diodes to go through, so less voltage drop.
Answer: Main Battery and it is on the #1 side. So you need Bus Tie ON as you are cross feeding electrical power to start #2 on battery. If you set Bus Tie to AUTO and the voltage drops below a prescribed value, the Bus Tie will disconnect and the starter will disengage.
Battery start is always quicker on #1 engine. Less diodes to go through, so less voltage drop.
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Thank you very much for all the replies. I understand the system overview,
but how should I get the fact that ENG 2 IGNITER & START is powered by DC ESS BUS 2.
I'm confused...
but how should I get the fact that ENG 2 IGNITER & START is powered by DC ESS BUS 2.
I'm confused...
Equally confusing is the mix of switch directions.
In the S76, everything ON is forward.
In this one, electrical switches ON are rearward, but fuel switches, pumps etc are Forward.
A potential for finger trouble - everything should be consistent, either all forward for ON, or all backward, it is dangerous to have a mix.
In the S76, everything ON is forward.
In this one, electrical switches ON are rearward, but fuel switches, pumps etc are Forward.
A potential for finger trouble - everything should be consistent, either all forward for ON, or all backward, it is dangerous to have a mix.
In this one, electrical switches ON are rearward
Edit: if you are referring to the YouTube clip, the switches you see are on the overhead panel, they are moved forwards to the on position.
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Starting No 2 first.....
..... why would you. Placing the Bus Tie Switch ON will load up the battery with the services on the Main 2 BB - not so smart if you are short of battery volts.
It is possible to start an engine with less than the required 23v but this is not recommended by the engine manufacturer because the resulting engine acceleration is too slow. This results in a low cooling air mass flow through the turbine area internals. This can lead to extreme heat in areas where the subsequent excessive metal expansion causes blade-rubbing on the inside of the turbine case. At the next internal inspection, the engine would be pulled for an overhaul.
A 'one-off' such start in extremis would probably be OK but those that have done it habitually have paid the price.
G.
It is possible to start an engine with less than the required 23v but this is not recommended by the engine manufacturer because the resulting engine acceleration is too slow. This results in a low cooling air mass flow through the turbine area internals. This can lead to extreme heat in areas where the subsequent excessive metal expansion causes blade-rubbing on the inside of the turbine case. At the next internal inspection, the engine would be pulled for an overhaul.
A 'one-off' such start in extremis would probably be OK but those that have done it habitually have paid the price.
G.
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TWINBIRD,
You are quite right, it is confusing. Both QRH and RFM say that the starter gens are on DC essential, and they are appear to be in the DC essential area on the overhead c/b panel. So why do all the training manual circuit diagrams show them off the main buses?
I have been trying for a couple of days to bump into one of the groundschool experts and ask them over a coffee. If I manage to pin them down and get an answer, I will post it on here.
You are quite right, it is confusing. Both QRH and RFM say that the starter gens are on DC essential, and they are appear to be in the DC essential area on the overhead c/b panel. So why do all the training manual circuit diagrams show them off the main buses?
I have been trying for a couple of days to bump into one of the groundschool experts and ask them over a coffee. If I manage to pin them down and get an answer, I will post it on here.
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There is one way only to start up engine n°1 (this is the less battery consuming engine) without GPU with main battery with less than 23V and/or residual ITT > 280°C and without having vented (dry motored) the engine before shut down.
The procedure is out of the manuals, its name is "semi-automatic procedure".
Sure lot of gentlemen are aware of this.
The procedure is out of the manuals, its name is "semi-automatic procedure".
Sure lot of gentlemen are aware of this.
The bus tie closes when manually switched to the on position. It will close in Auto mode when external power is connected or when one gen is failed. I was told there is a remote chance the auto mode could open the bus during the start sequence resulting in an inadvertent hot start on the #2 engine.
Like how to recharge the batteries from GPU. Very simple, but not in the manual!
There have been concerns on other types that allowing a rapid charging with the GPU
- following a low batt voltage situation for example - could create conditions for thermal runaway in the battery.
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TWINBIRD,
You are quite right, it is confusing. Both QRH and RFM say that the starter gens are on DC essential, and they are appear to be in the DC essential area on the overhead c/b panel. So why do all the training manual circuit diagrams show them off the main buses?
I have been trying for a couple of days to bump into one of the groundschool experts and ask them over a coffee. If I manage to pin them down and get an answer, I will post it on here.
You are quite right, it is confusing. Both QRH and RFM say that the starter gens are on DC essential, and they are appear to be in the DC essential area on the overhead c/b panel. So why do all the training manual circuit diagrams show them off the main buses?
I have been trying for a couple of days to bump into one of the groundschool experts and ask them over a coffee. If I manage to pin them down and get an answer, I will post it on here.
I look forward to the answer.
Yes, but what happens if you go out to the aircraft and discover someone has left a direct service on and the battery is lower than min for start? If you don't have the time to change the battery, do you start it on GPU and then let the aircraft or GPU push charge into it?
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There is one way only to start up engine n°1 (this is the less battery consuming engine) without GPU with main battery with less than 23V and/or residual ITT > 280°C and without having vented (dry motored) the engine before shut down.
The procedure is out of the manuals, its name is "semi-automatic procedure".
Sure lot of gentlemen are aware of this.
The procedure is out of the manuals, its name is "semi-automatic procedure".
Sure lot of gentlemen are aware of this.
Could you let me know the way called "semi-automatic procedure".
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I thought ENG 2 Starter/Generator was powered by DC MAIN BUS 2, so we got to set BUS TIE SW to ON to start No.2 ENG first
but it is described in RFM 3-51 that ENG 2 IGNITER & START is powered by DC ESS BUS 2
Battery start is always quicker on #1 engine. Less diodes to go through, so less voltage drop.
how to recharge the batteries from GPU. Very simple, but not in the manual!
It will close in Auto mode when external power is connected or when one gen is failed.
out of interest, what are peoples thoughts about this?
There have been concerns on other types that allowing a rapid charging with the GPU
- following a low batt voltage situation for example - could create conditions for thermal runaway in the battery.
There have been concerns on other types that allowing a rapid charging with the GPU
- following a low batt voltage situation for example - could create conditions for thermal runaway in the battery.
If you have gpu available, wouldn’t the safest option be to use it to provide start power, then let the battery recharge in the manner intended?
Yes, but what happens if you go out to the aircraft and discover someone has left a direct service on and the battery is lower than min for start?
If you don't have the time to change the battery, do you start it on GPU and then let the aircraft or GPU push charge into it?
I was lucky that I only had several unfamiliar CAS messages, but didn't have DUs black out. I heard DUs black out happened in the situation.
Could you let me know the way called "semi-automatic procedure"