A320 PA volume - headset/ACP vs handset
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A320 PA volume - headset/ACP vs handset
The training department at my airline tells us not to make normal PA announcements using the pushbutton on the Audio Control Panel. They tell us to use the dedicated PA handset on the aft of the center console instead. They claim that the ACP method is too loud, so it should only be used for emergency announcements. (One instructor went so far to say the ACP has an additional amplifier.) They say that, instead, the dedicated PA handset should be used for commonplace announcements, due to its lower volume level.
However, I can find no reference for this in our manuals. Also, I have tested PA's both ways with other crewmembers in the back and they said that, not only was the ACP PA not louder, they thought it sounded better than the handset. What say you, Airbus experts? Is there any validity behind my company's guidance, or is it just a myth that won't seem to go away?
However, I can find no reference for this in our manuals. Also, I have tested PA's both ways with other crewmembers in the back and they said that, not only was the ACP PA not louder, they thought it sounded better than the handset. What say you, Airbus experts? Is there any validity behind my company's guidance, or is it just a myth that won't seem to go away?
Last edited by Skepilot; 10th Dec 2019 at 16:24.
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I’ve heard that before. My last company’s manuals mentioned it. It makes sense, but I’ve never tested it. Current company is silent on the topic.
Nonetheless, we weren’t told not to use the ACP, just made aware of the difference. Perhaps a customer option?
Nonetheless, we weren’t told not to use the ACP, just made aware of the difference. Perhaps a customer option?
Another take on it
On the A320 (and I suspect all Airbus, and pretty sure the same on the 787) the PA handset is wired to the hot battery bus, so it will always work. ie: after both engines and APU are shutdown via the fire PB in an evacuation you can easily make the announcement via the Handset.
Only Capt side audio selector works but needs to be reselected after power transfer to use the radio or the PA button. (Often forgotten in the mad rush of an evac)
So in the spirit of “practice what you play”, if you get in the habit of using the PA handset for all cabin announcements, when you come to a real emergency, your muscle memory will reach for the handset and the message will get through.
RTO for example, “STOP” -> REV Thrust -> IDLE -> Park Brake On -> PA handset. It’s a very simple movement of the hand in the same direction.
As for the volume as mentioned by the OP, never heard that, don’t know the answer. Some of our a/c are really loud, some not so loud.
An old maintenance joke from a bygone era.
Tech log entry “PA unbelievably loud”
Maint Entry “ PA turned down to more BELIEVABLE level”😂😂😂
Only Capt side audio selector works but needs to be reselected after power transfer to use the radio or the PA button. (Often forgotten in the mad rush of an evac)
So in the spirit of “practice what you play”, if you get in the habit of using the PA handset for all cabin announcements, when you come to a real emergency, your muscle memory will reach for the handset and the message will get through.
RTO for example, “STOP” -> REV Thrust -> IDLE -> Park Brake On -> PA handset. It’s a very simple movement of the hand in the same direction.
As for the volume as mentioned by the OP, never heard that, don’t know the answer. Some of our a/c are really loud, some not so loud.
An old maintenance joke from a bygone era.
Tech log entry “PA unbelievably loud”
Maint Entry “ PA turned down to more BELIEVABLE level”😂😂😂
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The volume output between the PA key on the ACP and the PA handset is the same.
This is one of those things they teach in your 320 and 330 fleets that falls into "we've always taught that."
Hope this helps
This is one of those things they teach in your 320 and 330 fleets that falls into "we've always taught that."
Hope this helps
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I'm kind of thinking it may have been true on the early A320s, and the "institutional memory" is just being applied to the entire fleet. It's definitely not true on our new ones.
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I wish they’d have copied Boeing and allowed us to speak with the flight attendants using the handset.
On the A320 (and I suspect all Airbus, and pretty sure the same on the 787) the PA handset is wired to the hot battery bus, so it will always work. ie: after both engines and APU are shutdown via the fire PB in an evacuation you can easily make the announcement via the Handset.
Only Capt side audio selector works but needs to be reselected after power transfer to use the radio or the PA button. (Often forgotten in the mad rush of an evac)
So in the spirit of “practice what you play”, if you get in the habit of using the PA handset for all cabin announcements, when you come to a real emergency, your muscle memory will reach for the handset and the message will get through.
RTO for example, “STOP” -> REV Thrust -> IDLE -> Park Brake On -> PA handset. It’s a very simple movement of the hand in the same direction.
As for the volume as mentioned by the OP, never heard that, don’t know the answer. Some of our a/c are really loud, some not so loud.
Only Capt side audio selector works but needs to be reselected after power transfer to use the radio or the PA button. (Often forgotten in the mad rush of an evac)
So in the spirit of “practice what you play”, if you get in the habit of using the PA handset for all cabin announcements, when you come to a real emergency, your muscle memory will reach for the handset and the message will get through.
RTO for example, “STOP” -> REV Thrust -> IDLE -> Park Brake On -> PA handset. It’s a very simple movement of the hand in the same direction.
As for the volume as mentioned by the OP, never heard that, don’t know the answer. Some of our a/c are really loud, some not so loud.
1. CABIN CREW (PA) ... ALERT: The FCTM RTO Flow Pattern is suggesting the ACP PA button should be used.
2. EVACUATION .... INITIATE: Nothing is specified, but I normally use the ACP PA button to save time prior to pressing the EVAC COMMAND button.
Also, the ACP PA button is momentary and does not need to be re-selected after transfer to hot bus battery power (I think...).
By always using the handset for passenger PAs, you separate speaking to passengers away from the ACP in your mind, so it reduces that possibility. We can still use the PA switch on the ACP for emergency CC announcements.
Re: relative volumes, the PA volume is increased when the engine(s) are running. Maybe it increases differently depending which PA method is used, so you would only hear a difference in flight?
For an RTO followed by an EMER EVAC, there are 2 calls using the PA system.
1. CABIN CREW (PA) ... ALERT: The FCTM RTO Flow Pattern is suggesting the ACP PA button should be used.
2. EVACUATION .... INITIATE: Nothing is specified, but I normally use the ACP PA button to save time prior to pressing the EVAC COMMAND button.
Also, the ACP PA button is momentary and does not need to be re-selected after transfer to hot bus battery power (I think...).
1. CABIN CREW (PA) ... ALERT: The FCTM RTO Flow Pattern is suggesting the ACP PA button should be used.
2. EVACUATION .... INITIATE: Nothing is specified, but I normally use the ACP PA button to save time prior to pressing the EVAC COMMAND button.
Also, the ACP PA button is momentary and does not need to be re-selected after transfer to hot bus battery power (I think...).
Our company used to have a "Technique Only" bias to the Handset, it even appears in a training video of a RTO. In saying that, we have gone to EBT and now training is so much better and as long as you achieved the desired outcome, and learnt something, everyone is happy.
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Had a look at the aircraft maintenance and schematics manuals and the only difference between the handset and ACP’s is the handset goes directly to CIDS whereas the ACP’s all go to the audio management unit then from the AMU to CIDS.
It’s the CIDS that receives the engine running and cabin decompression signals to increase the volume so the same volume would be heard from either source of mic (Boom-mic or Handset)
The ACP 1, 2, AMU and CIDS are all powered by the 28VDC ESS BUS and the ACP 3 is powered by DC BUS 1 so in theory they are all always available.
//Edited to replace BATT BUS 1 with DC BUS 1//
It’s the CIDS that receives the engine running and cabin decompression signals to increase the volume so the same volume would be heard from either source of mic (Boom-mic or Handset)
The ACP 1, 2, AMU and CIDS are all powered by the 28VDC ESS BUS and the ACP 3 is powered by DC BUS 1 so in theory they are all always available.
//Edited to replace BATT BUS 1 with DC BUS 1//
Last edited by aeo; 18th Apr 2022 at 05:59.
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What about in the case of loss of DC ESS Bus and an emergency evacuation is required? Is the handset still available to communicate with the cabin crews? Or we need to use ACP 3 to make the emergency announcement?
Thanks.
Thanks.
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If you lost your DC ESS Bus you would lose the CIDS so no PA Availability at all - comm’s with the cabin crew would also be lost.
LOSS of TRU 1 + 2 (AC Bus 1 + 2 loss) would mean no DC 1 BUS therefore no ACP 3 - But you still would need CIDS for PA.
The only way to lose DC ESS BUS would be if Battery 2 was either flat or turned off (above 50 knots you cannot switch it OFF - well you can but if it’s supplying the essential DC bus nothing will happen).
In other words it’s Airbus’ intention that the ESS DC BUS will always be powered no matter what the failure.
Hope this isn’t too much info … 😉
LOSS of TRU 1 + 2 (AC Bus 1 + 2 loss) would mean no DC 1 BUS therefore no ACP 3 - But you still would need CIDS for PA.
The only way to lose DC ESS BUS would be if Battery 2 was either flat or turned off (above 50 knots you cannot switch it OFF - well you can but if it’s supplying the essential DC bus nothing will happen).
In other words it’s Airbus’ intention that the ESS DC BUS will always be powered no matter what the failure.
Hope this isn’t too much info … 😉
Last edited by aeo; 18th Apr 2022 at 06:12.
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Thank you for your reply. I’m getting a bit confused tho cause one of my friend just did a simulator session with DC ESS bus fault and he told me the hand mike was working when doing PA announcement. Or he would be using F/O hand Mike or his head set mike with ACP 3 to make pax announcement. But FCOM says “Flight interphone is unserviceable with DC ESS fault. 
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The plot thickens … This is straight from the maintenance manual.
////////////
CIDS Power Supply:
The service bus, the essential bus and the hot battery bus supply electrical power to the CIDS.
Depending on the available bus the CIDS operates in the:
- Normal mode or
- Emergency mode.
In the normal mode the service bus supplies 28VDC to the CIDS. All functions of the system operate fully.
In the emergency mode the essential bus supplies 28VDC to the CIDS. If the essential bus is not available then (if emerg lights are in arm or on) the hot battery bus supplies CIDS.
To conserve power the system operates with minimum functions.
The ACP’s and the AIP’s do not operate.
The remaining functions are:
- PA
- Cabin Interphone
- EVAC
- Smoke Detection
////////
So I guess it really depends on the failures your friend encountered in the SIM. If he had an ESS BUS fault when in Emergency Elec Config then the hot battery bus would supply those very basic CIDS functions - But no ACP 3.
Also, the AMU would not be powered so Cockpit Handset is all you would have.
If the ESS BUS fault occurred with power available then selecting the FO’s audio to 3 would transfer all of his audio equipment (including hand held mic) onto ACP 3.
Cockpit Handset would also be available.
////////////
CIDS Power Supply:
The service bus, the essential bus and the hot battery bus supply electrical power to the CIDS.
Depending on the available bus the CIDS operates in the:
- Normal mode or
- Emergency mode.
In the normal mode the service bus supplies 28VDC to the CIDS. All functions of the system operate fully.
In the emergency mode the essential bus supplies 28VDC to the CIDS. If the essential bus is not available then (if emerg lights are in arm or on) the hot battery bus supplies CIDS.
To conserve power the system operates with minimum functions.
The ACP’s and the AIP’s do not operate.
The remaining functions are:
- PA
- Cabin Interphone
- EVAC
- Smoke Detection
////////
So I guess it really depends on the failures your friend encountered in the SIM. If he had an ESS BUS fault when in Emergency Elec Config then the hot battery bus would supply those very basic CIDS functions - But no ACP 3.
Also, the AMU would not be powered so Cockpit Handset is all you would have.
If the ESS BUS fault occurred with power available then selecting the FO’s audio to 3 would transfer all of his audio equipment (including hand held mic) onto ACP 3.
Cockpit Handset would also be available.
Last edited by aeo; 19th Apr 2022 at 15:03.
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Hello Aeo,
Ok thank you for your reply. I believe my friend only had GEN 1 fault then DC ESS bus fault followed by APU fire on short final resulting with potential emergency evacuation after landing.
Ok thank you for your reply. I believe my friend only had GEN 1 fault then DC ESS bus fault followed by APU fire on short final resulting with potential emergency evacuation after landing.