AW139 Battery start procedure

[twinbird]

:confused: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.

[Nescafe]

From the AW tech notes

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.

If the bus tie is left in auto in the situation you describe, the no2 starter gen will not be powered.

[Nescafe]

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.

[noooby]

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.

[Sir Korsky]

https://www.youtube.com/watch?v=HNjCL651-dU

HNjCL651-dU

Explanation at 1.00

[twinbird]

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...

[Ascend Charlie]

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.

[Nescafe]

In this one, electrical switches ON are rearward

Not so. Everything goes forwards to go on.

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.

[Ascend Charlie]

AHA!!

Thank you. Forward is ON, all good. The 76 had almost everything on the lower console.

[Geoffersincornwall]

..... 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.:ok:

[Non-PC Plod]

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.

[maeroda]

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.

[noooby]

Lots of things aren't in the manuals (unfortunately). Like how to recharge the batteries from GPU. Very simple, but not in the manual!

[Sir Korsky]

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.

[[email protected]]

Like how to recharge the batteries from GPU. Very simple, but not in the manual! 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.

[Nescafe]

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?

[twinbird]

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.
Thank you very much Non-PC Plod!
I look forward to the answer.

[[email protected]]

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?

[twinbird]

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.
I had a few times to start engine with less than 23V battery. 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".

[Buitenzorg]

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 firstThis is correct.
but it is described in RFM 3-51 that ENG 2 IGNITER & START is powered by DC ESS BUS 2This is NOT correct. There is no circuit breaker between the starter/generator and the respective main bus (in this case, main bus 2), but a "contactor"; in essence, a relay. This relay is powered by the respective essential bus, not the starter itself.
Battery start is always quicker on #1 engine. Less diodes to go through, so less voltage drop.Bingo. Only time I'll agree to start #2 off internal battery is with both good voltage and cold engine. We tend to park with left side upwind so this is "almost never".
how to recharge the batteries from GPU. Very simple, but not in the manual!I like that too! That way it's the engineers who'll be responsible for choosing that short-cut and the resulting hot start or worse if some battery cells happen to be damaged rather than the battery depleted. The level of system knowledge displayed here supports not letting pilots make these calls.
It will close in Auto mode when external power is connected or when one gen is failed.At the time of starting the first engine NEITHER generator is working so the bus tie will be open => no power on main bus 2 => no power to starter/generator 2 even if the starter/generator "contactor" (see above) is closed.
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.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?Would you rather have a thermal runaway in an empty aircraft sitting on the ramp, or in an aircraft with both engines running, and you being strapped inside it? Also, the GPUs I've used had slightly lower voltage (and therefore, lower charging current) than the generators gave after engine start, therefore IMO a lower chance of thermal runaway.
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?This is indeed by far the most prevalent cause of low battery voltage on start-up, far more common than damaged battery cells or wiring/circuit faults, and is why recharging from the GPU is so popular.
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?How important is it to take off on that flight right now? Life or death type important? The procedure you propose definitely comes with an increased risk of problems that will preclude the flight from taking place at all, but maybe taking that chance is warranted under the circumstances? I only fly simple O&G offshore revenue flights and would rightly be censured for taking this option even if I were to get away with 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.Not only that, the EECs (during engine start) and GCUs are also powered off the essential buses; would you even be able to abort the ongoing start when your only source of electrical power flakes out?
Could you let me know the way called "semi-automatic procedure"I think it's in the RFM under "MANUAL ON GROUND START PROCEDURE". I would NOT recommend this for low battery voltage - if the screens blank out, how can you tell if the start is going hot? If you then abort the start because the blank screens, how do you know if you have pooled fuel inside the engine case still burning? Unless you see flames coming out of the exhaust once you get out, in which case what'll you do now, with really, conclusively, no battery power to speak of?

[maeroda]

Semi automatic procedure is feasible if before shut down dry motoring cannot be performed for any reason and APU is not available.

Before going on, set MFD CPL, MCDU CPL & PIL brakers out, RCP to MFD CPL only, all electrical power consuming items set wisely OFF.

Check BATT not bellow 20V and residual ITT between 250° / 280° C.

ENG#1 only, battery start procedure setup (leave all systems checks for after start).
GOV switch: AUTO
ECL: OFF (using beeper trim)
FUEL boost and switch: ON both
ENG switch: IDLE
---wait 5 to 7 seconds, check ITT must decrease---
NG @15% minimum
ECL: IDLE (min) using beeper trim.

example:
A/C long nose, 44Ah & 27Ah batteries installed, EAPS installed, supp. 85 NOT installed, startup @ SL and OAT 50°C, BATT: 20V and residual ITT:280°C: ITT peak on startup could be around 780°C for less than 1 second.

If MFD goes blank: abort procedure or count seconds and push ECL to IDLE anyway, remember the hot start graphic assessment gives large margin to ITT vs time.

cheers

[noooby]

Hi Crab,

External GPU recharges batteries much slower than onboard Generators. GPU recharges at about 75Amps and it rapidly ramps down. Aircraft Generators push 200+Amps into the batteries after start.

I used to use GPU recharging where we had hangar power for the aircraft, but not a GPU on the line. Top up the batteries before pushing out to the line to make sure every last Volt was in there!

One thing that catches many people out is when they use a battery cart (as opposed to a diesel GPU.

Once the battery cart voltage drops below the aircraft battery voltage (like during a start because the 139 sucks so much out of the batteries), the aircraft battery will try to charge the battery cart as well as try to start the engine. You're better off not using a battery cart at all. Diesel GPU or nothing.

There is no diode or reverse current relay on the External Power circuit.

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.

[malabo]

ENG#1 only, battery start procedure setup (leave all systems checks for after start)

Skilled crew can move through the checklist pretty quick, with a good copilot and batteries I could get all the RFM battery start system checks done and still have 23v for the start. With suspect batteries nobody I knew would do any systems checks before a battery start. If it was fine when shut down, then likely so on start - helicopter doesn't know if it is the same day or the next. Also depends if dicking around until below 23v results in sleeping in the back of the helicopter for a couple of days instead of back in your 5 star hotel. 139 always had lower than normal battery voltage, heard of some operators adding an extra 1.5v cel to the battery pack. BTW, I knew of some offshore operations where the pilots have never done a battery start, only GPU, and in fact battery starts were prohibited by ops. Those would never know what condition their battery was in.

[maeroda]

Malabo,
what you say is correct..... unless you leave the bird parked in an deep African hangar with monkey helicopter engineers unable to count from 1 to 10 on their two hands junking around and playing pretending they're real engineers....or you work in extreme cold weather like Aosta or Sondrio in wintertime at 3000 meters, or you fly chewed asses in short range hems flying 10 minutes long missions, or you forced to shut down the bird for any reason on a drill ship only to discover the ship GPU is U/S in spite of what the HLL was stating before leaving base onshore (damned offshore operations!).

Also, maybe some of us do not have any copilot because we fly single pilot since the very beginning on type and even so the company check list wisely states if is battery or GPU start as a reminder and as the RFM says the same anyways; it goes without saying that we still don't need any checklist for start up as we do it routinely by heart.

Apart of personal recollections, there are quite some situations where we may be forced to start up bellow 23V without APU unless we love to wait for help on a mountain peak or into a remote jungle.

But mostly, this procedure is designed to avoid hot-starts after flying short legs without carrying APU and no time for the generators to recharge hard used batteries, you know that battery Voltage could be OK but battery Capacity could be not.

Cheers

[belly tank]

As Malabo said with a good crew flow you can startup pretty quick. We routinely use ships battery only for the start at our base and ive never seen the voltage drop below 23V prior to starting No1.

[Non-PC Plod]

Twinbird,

There you go - Buitenzorg got it, and it makes absolute sense although it is not well-described in the manuals. Both the generator control units and the EECs are powered from the essential buses before and during the start, although the power to the starter motor itself comes from the main bus.
Be careful - as Geoffers said, starts below 23v could well be trashing the back end of the engine.
As others have said, if you regularly exercise the batteries by using them instead of GPU to start, they will hold 23v OK. If you always do ground power starts, the batteries rapidly deteriorate. Fortunately, you can fix them by using them, and in fact I have seen batteries recover to normal within several days of being used regularly for starts.
There is also a new-ish modification available (supplement 85 - improved engine starting kit) which gives a bigger aux battery, and connects both the main and aux batteries in parallel for start, which gives a bit more oomph for those operators in situations like those described by Maeroda. It also gives longer endurance following a double DC gen fail.

[Outwest]

Just do this and all those problems go away....

Concorde Battery Announces AW139 STC With Multiple Validations | Aero-News Network (http://www.aero-news.net/index.cfm?do=main.textpost&ID=DFCE1F5D-16BA-45FC-92FA-2D79AC6E7108)

[maeroda]

Belly tank,

I agree with you, but try to think about doing 10 to 20 flights per day of 10 to 15 minutes each from start to stop and being forced to shut down between flights.
Sooner or later you will face the need to start up with APU or with less than 23V battery voltage.

[[email protected]]

Nooby - thanks for the reply - it would seem then that the worse case would be finding the battery was low on volts for start, using a GPU to get the engines going and then allowing the generators to rapidly charge the batteries. Again, what about the risk of thermal runaway in this case? Any experience of it?

[belly tank]

Maeroda,
Yes I concur with your situation that is a lot of starts a day!. We generally only do 2-3 starts a day and flights 1.5 - 2.0 hrs between starts. All the best:ok:

[ShyTorque]

Lots of things aren't in the manuals (unfortunately). Like how to recharge the batteries from GPU. Very simple, but not in the manual!

Does the system allow this? On other aircraft by this manufacturer, connecting a GPU isolates the battery, so it cannot charge it.

[maeroda]

On AW139's, recharging main & aux batteries could be accomplish as follows:
- plug GPU (either diesel or electric powered by 3phase) to a/c
- BUS TIE switch ON
- braker BUS CONT 1 out

Monitor time, max charge time is 5 minutes.

[ShyTorque]

On AW139's, recharging main & aux batteries could be accomplish as follows:
- plug GPU (either diesel or electric powered by 3phase) to a/c
- BUS TIE switch ON
- braker BUS CONT 1 out

Monitor time, max charge time is 5 minutes.

But is this technique approved by the manufacturer?

[maeroda]

Of course is not, as well as it isn't the semi automatic startup procedure I've described above.

[noooby]

You also have to have Ext Pwr, Master, Main Batt and Aux Batt ON.

[maeroda]

Sorry Nooby, I forgot to mention the basic electrical power setting...it was going without saying to me.

[ShyTorque]

If it's not an approved procedure, I for one wouldn't ever try it unless it was a life or death situation. Goodness knows what damage could be done to the aircraft systems if there is a regulator problem with the GPU.

[tottigol]

It seems as everybody is an expert on OEM non approved procedures.

[maeroda]

Shy torque,
in general, you may be right but this carries the assumption that manufacturers are doctors doctors in everything, and that's not the case talking about Agusta.

But honestly, I've been going on with that startup procedure since around 2008 and there's nothing to be worried about in starting the bird in that way, specially if working (I say working, not hauling from A to B where A and B are well served aerodromes).

Regarding battery charging option and Tottigol: again, since first release to service with whose ****ting OEM batteries equipping the short noses birds, that was one of the ways to have some more juice in the battery theirselves when really doing the job the helicopter was supposed to do according to Agusta.
Job that was definitely out of the reach of the 139 without a little help from the operators (because Agusta didn't know any **** about how to operate the helicopter off airports), hence somebody of us had to go on and think it all the way around to skip the option to be forced to stay overnight on a freezing pinnacle at 4000 meters without appropriate gear in the cargo hold.

This wouldn't be happening with an Airbus H145 for sure.

[noooby]

Actually the battery charging method was developed at Agusta and shown to me (and many other early Customers) by the head of Avionics on the production line as they were also having issues with battery capacity.
That was in 2005 and you'll still find people at Agusta using that method occasionally.

[ericferret]

The 169 electrical system allows battery charging from ground power as a normal operation. Progress.