Service Bulletin 747-24-2246
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Service Bulletin 747-24-2246
Last year AD note 2009-15-12 has been published. This AD note prescribes to accomplish Boeing SB 747-24-2246. The purpose of this SB is to give flight crew the possibility to remove electrical power from IFE and other non-essential systems through left and right utility switches S19 and S20, and keep the passenger reading lights on by switching them to the AC busses. Is there anyone who has experience with this SB? What is the added value of this modification to the present system? By switching S19 and S20 to "OFF" you're already removing power from all non essential systems...
Bulletin 747-24-2246
The purpose of the AD would be evident by the reason to put it out! Along of course with th effectivity and compliance date.
There is also the local Boeing field office rep to give an answer unless I am presuming if you are working for a company with access to a technical dept the guys would no doubt give out that info anyway!
I am speaking as an ex development engineer retired and things may have changed of course but generally having been responsible over may years for SB and AD action the reasons are always many and varied with perhaps an operator in some
cases finding in service problems which will result in SB action especially if there are FAA or CAA inputs!!
There is also the local Boeing field office rep to give an answer unless I am presuming if you are working for a company with access to a technical dept the guys would no doubt give out that info anyway!
I am speaking as an ex development engineer retired and things may have changed of course but generally having been responsible over may years for SB and AD action the reasons are always many and varied with perhaps an operator in some
cases finding in service problems which will result in SB action especially if there are FAA or CAA inputs!!
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I am only guessing here but it would seem logical that having the ability to switch the power off from the IFE would eliminate a re-occurence of swissair 111 in which the fire could not be extinguished due to no way switching off the IFE.
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BACKGROUND
The change described in this service bulletin will allow the flight crew to remove power from the non-essential cabin systems if smoke or flames occur.
We have received numerous reports of smoke or flames in the passenger cabin related to the wiring for the passenger cabin in-flight entertainment system, cabin lighting and passenger seats.
It is not easy to remove the electrical power to these systems to stop the smoke or flames.
New relays can be installed to allow the flight crew to remove the electrical power from the non-essential passenger cabin systems using the left and right utility bus switches.
The change described in this service bulletin will allow the flight crew to remove power from the non-essential cabin systems if smoke or flames occur.
We have received numerous reports of smoke or flames in the passenger cabin related to the wiring for the passenger cabin in-flight entertainment system, cabin lighting and passenger seats.
It is not easy to remove the electrical power to these systems to stop the smoke or flames.
New relays can be installed to allow the flight crew to remove the electrical power from the non-essential passenger cabin systems using the left and right utility bus switches.
Again, I don't know about the 747 but on the 75 and 76 the utility bus switches don't knock off the lights or entertainment systems.
We have seperate IFE power switches in the cabin on our fleet but I know we have a mod program coming up to install a switch in the flight deck for all our aircraft that have IFE. Our new aircraft (Airbus and Boeing) in the the last 12 months have come with this as standard fit. It's labelled Commercial power on the Bus but does the same thing.
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Reading through this also seems to answer all of your questions too.
http://rgl.faa.gov/Regulatory_and_Gu...2009-15-12.pdf
http://rgl.faa.gov/Regulatory_and_Gu...2009-15-12.pdf
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When analyzing the schematics in this SB the only conclusion which you can make is that only passenger reading lights are switched to an AC bus after switching the utility switches. The aim of the AD note is to remove power from IFE and other non-essential systems. As far as I know passenger reading lights are non-essential systems. By performing this SB the passenger reading lights will become an essential system. What if there is smoke in the passenger compartment caused by the wiring in the passenger reading lights? Pressing the utility switches in OFF will not solve this problem.
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I guess they feel the IFE and Cabin lights are most likely to cause smoke or flames wheras there haven't been any problems caused by the reading lights?
IFE and Cabin lighting are two areas that many operators retrofit systems and these are more likely to cause problems than the standard fit reading light system. If you read the link I provided above, not everyone agrees with the intent of the SB and some operators have applied to dodge it.
That's my take on it anyway.
IFE and Cabin lighting are two areas that many operators retrofit systems and these are more likely to cause problems than the standard fit reading light system. If you read the link I provided above, not everyone agrees with the intent of the SB and some operators have applied to dodge it.
That's my take on it anyway.
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You're right. When reading the link which you've send, you'll see that not everyone agrees with this SB.
In my opinion this SB does not meet the intention of the AD. The passenger reading light are a non-essential system, that is the reason why it is possible to switch it off through the utility switches.
Even if you retrofit your aircraft, you are not "allowed" to put non-essential systems under the "normal" ac busses. For the simple reason that flight crew must be able to turn it off without affecting other flight critical systems.
As far as I know, I can't remeber any accident or incident with flames in the passenger compartment. Smoke development is not the same as fire.
In my opinion this SB does not meet the intention of the AD. The passenger reading light are a non-essential system, that is the reason why it is possible to switch it off through the utility switches.
Even if you retrofit your aircraft, you are not "allowed" to put non-essential systems under the "normal" ac busses. For the simple reason that flight crew must be able to turn it off without affecting other flight critical systems.
As far as I know, I can't remeber any accident or incident with flames in the passenger compartment. Smoke development is not the same as fire.
