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thewizbizman
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Avionics Bay Access and Pressurization

Mon Jan 24, 2022 2:21 pm

Greetings, wanted to see if anyone could spare some knowledge on what commercial aircraft have avionics bays, in what aircrafts is it accessible during flight, and are they normally pressurized.

Thanks for the insight
 
extender
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 3:32 pm

Of the Boeing and Airbus, they are all in the pressurized area of the fuselage. 707 is accessible, some of the Airbus wide bodies as well.
 
Lpbri
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 4:13 pm

All airliners have forward E&E compartments. On wide bodies, they are accessible from the cabin, narrow bodies they are not. On the 777, the E&E is accessible from the forward cargo. The 787 also has an aft E&E, not accessible from the cabin but from the aft cargo. All E&E compartments have external access.
 
VMCA787
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 6:00 pm

On the 747, there is a bulkhead door in the fwd wheel well. No warning light in the cockpit.
 
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DL_Mech
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 6:33 pm

Some E&E cabin access doors have been deactivated due to security reasons.
 
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akoma
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 6:50 pm

VMCA787 wrote:
On the 747, there is a bulkhead door in the fwd wheel well. No warning light in the cockpit.


Interesting... what version of 747 is this?
I have not come across a door in the fwd wheel well leading into the fwd EE compartment among the many 747s I have been on. However, I have only been on the regular -200, -300 & -400 versions.
On most of the 747s I know, the front part of the fwd EE compartment meets the fwd bulkhead via two side crawl-ways, with the weather radar antenna mounted on the other side. There are small glass windows present in the fwd EE compartment to view the NLG, but I have not seen an actual door.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 9:08 pm

VMCA787 wrote:
On the 747, there is a bulkhead door in the fwd wheel well. No warning light in the cockpit.


Sure about that? MD11 has one that I only found out about recently. Never saw one on a B747.

As stated, just about every ATC aircraft has an E&E compartment, or two, and as far I’ve come across, they are all pressurized. Accessible is a different story.
 
GalaxyFlyer
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 10:06 pm

Yeah, the Whale has one. A friend, who was a wrench on it at UPS loved to tell of diverting into King Salmon and using it as a way to the ground to order fuel. No stairs available.
 
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zeke
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 10:07 pm

Lpbri wrote:
On wide bodies, they are accessible from the cabin, narrow bodies they are not.


In Airbus widebodies there is no access from the cabin to the bay.

DL_Mech wrote:
Some E&E cabin access doors have been deactivated due to security reasons.


Following MH370, does not take a rocket scientist to know what the smart money was on for the cause.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 10:28 pm

GalaxyFlyer wrote:
Yeah, the Whale has one. A friend, who was a wrench on it at UPS loved to tell of diverting into King Salmon and using it as a way to the ground to order fuel. No stairs available.


Yes, but that is the normal E&E access in the floor of the main deck. Six’ish feet below that is the exterior E&E door, which is monitored by a warning system.

zeke wrote:
In Airbus widebodies there is no access from the cabin to the bay.


Our A300 have access from the flight deck. Can’t recall if that access exists on pax birds…Pan Am was a long time ago.
 
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77west
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Re: Avionics Bay Access and Pressurization

Mon Jan 24, 2022 10:58 pm

fr8mech wrote:
GalaxyFlyer wrote:
Yeah, the Whale has one. A friend, who was a wrench on it at UPS loved to tell of diverting into King Salmon and using it as a way to the ground to order fuel. No stairs available.


Yes, but that is the normal E&E access in the floor of the main deck. Six’ish feet below that is the exterior E&E door, which is monitored by a warning system.

zeke wrote:
In Airbus widebodies there is no access from the cabin to the bay.


Our A300 have access from the flight deck. Can’t recall if that access exists on pax birds…Pan Am was a long time ago.


Here is a video of the A350 EE bay with the hatch on the flight deck.

https://www.youtube.com/watch?v=LxS2RR-Vx_s
 
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Starlionblue
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 1:30 am

Lpbri wrote:
All airliners have forward E&E compartments. On wide bodies, they are accessible from the cabin, narrow bodies they are not. On the 777, the E&E is accessible from the forward cargo. The 787 also has an aft E&E, not accessible from the cabin but from the aft cargo. All E&E compartments have external access.


Semantics but not always from the cabin. Some avionics bays have the access hatch in the cockpit.

fr8mech wrote:
GalaxyFlyer wrote:
Yeah, the Whale has one. A friend, who was a wrench on it at UPS loved to tell of diverting into King Salmon and using it as a way to the ground to order fuel. No stairs available.


Yes, but that is the normal E&E access in the floor of the main deck. Six’ish feet below that is the exterior E&E door, which is monitored by a warning system.


zeke wrote:
In Airbus widebodies there is no access from the cabin to the bay.


Our A300 have access from the flight deck. Can’t recall if that access exists on pax birds…Pan Am was a long time ago.


Same on the A330/A340 and the A350.
 
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77west
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 1:41 am

Starlionblue wrote:
Lpbri wrote:
All airliners have forward E&E compartments. On wide bodies, they are accessible from the cabin, narrow bodies they are not. On the 777, the E&E is accessible from the forward cargo. The 787 also has an aft E&E, not accessible from the cabin but from the aft cargo. All E&E compartments have external access.


Semantics but not always from the cabin. Some avionics bays have the access hatch in the cockpit.

fr8mech wrote:
GalaxyFlyer wrote:
Yeah, the Whale has one. A friend, who was a wrench on it at UPS loved to tell of diverting into King Salmon and using it as a way to the ground to order fuel. No stairs available.


Yes, but that is the normal E&E access in the floor of the main deck. Six’ish feet below that is the exterior E&E door, which is monitored by a warning system.


zeke wrote:
In Airbus widebodies there is no access from the cabin to the bay.


Our A300 have access from the flight deck. Can’t recall if that access exists on pax birds…Pan Am was a long time ago.


Same on the A330/A340 and the A350.


Looks like A380 as well: http://www.gillesvidal.com/blogpano/cockpit1.htm

The 747 one is shown quite well on a Sam Chui video where they climb up an old stored one in the desert, they climb up on the nose gear and them up into the EE bay and then through a panel in the floor of the old first class.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 2:21 am

77west wrote:

The 747 one is shown quite well on a Sam Chui video where they climb up an old stored one in the desert, they climb up on the nose gear and them up into the EE bay and then through a panel in the floor of the old first class.


Back when I was a newly minted, youthful and energetic A&P, I would climb up the aft side of the gear, reach back unlatch and open the hatch and scamper inside. Later as youth and energy dissipated, iI would climb up, open the hatch, reach in and deploy the ladder (that was tricky, but could be done), climb back down and climb the ladder into the compartment…like a civilized person.

Now, I just send someone up and tell them to shoot me a picture of what they want me to see…or I just take their word for it. I’m too old for that kind of action.
 
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thewizbizman
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 3:42 am

Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?
 
113312
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 4:11 am

While this question, I'm sure, is a quest for information and knowledge, to answer it in a public forum could constitute a security risk for commercial operations. I would suggest to the site administrator that the replies be considered and filtered for potential sensitive information. I would not want to see innocent questions and well meaning answers later involved in an investigation. Access to the flight deck and equipment of the aircraft is restricted and must be secure from malevolent intervention.
 
celestar345
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 4:11 am

fr8mech wrote:
VMCA787 wrote:
On the 747, there is a bulkhead door in the fwd wheel well. No warning light in the cockpit.


Sure about that? MD11 has one that I only found out about recently. Never saw one on a B747.

As stated, just about every ATC aircraft has an E&E compartment, or two, and as far I’ve come across, they are all pressurized. Accessible is a different story.


Working on a 747 C-check at the moment and can't find it....

As you said my colleagues say that it must be an MD-11 which has access door there.

For Airbus there is no lock for access, for obvious reasons.

For Boeing most hatch doors are locked which requires key to open and carpeted over, or simply has no access handle on the cabin side.

fr8mech wrote:
Back when I was a newly minted, youthful and energetic A&P, I would climb up the aft side of the gear, reach back unlatch and open the hatch and scamper inside. Later as youth and energy dissipated, iI would climb up, open the hatch, reach in and deploy the ladder (that was tricky, but could be done), climb back down and climb the ladder into the compartment…like a civilized person.


I still do this all the time especially these days when a lot of parked aircraft need to perform prolonged parking procedures, jumping up and down the 747 & 767 when the air stairs are not available and have to climb up to the cockpit. 777 is just too high and will need access ladder...

thewizbizman wrote:
Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?


Unlikely the will need to, but you never know when you will need to. We had one incident where a power transfer relay decided to fail during a test flight, whole cockpit went black and only standby instruments available. Jumped down within 30 seconds and smacking the relay like mad to bring it back to life...
 
FGITD
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 4:42 am

fr8mech wrote:

Now, I just send someone up and tell them to shoot me a picture of what they want me to see…or I just take their word for it. I’m too old for that kind of action.


One of my fond memories from when I first started working in airline operations is when one of our older engineers really involved me in his work, giving me precise instructions, drew a layout of what to look for, and gave me a radio. Then had me awkwardly climb up and take a picture and send it to him.

As soon as my feet hit the ground again I realized exactly what he’d used me for. All the same, a pretty neat experience for a non-engineer.

Wouldn’t exactly refer to this topic as SSI. It’s not easily accessible from the cabin, and if you’re able to reach it while on the ground, about 1000 other security items have already failed
 
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77west
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 4:50 am

113312 wrote:
While this question, I'm sure, is a quest for information and knowledge, to answer it in a public forum could constitute a security risk for commercial operations. I would suggest to the site administrator that the replies be considered and filtered for potential sensitive information. I would not want to see innocent questions and well meaning answers later involved in an investigation. Access to the flight deck and equipment of the aircraft is restricted and must be secure from malevolent intervention.


Here is a video of the 747 hatch https://youtu.be/OK9zhumtGg0?t=327

In terms of security, as the vast bulk of these internal-access doors are already behind a locked and fortified cockpit door I don't think there is any inherent risk. There is enough publicly available information that it is a bit of a moot point. The location of these hatches is often laid out in the emergency / firefighting documentation which is also public.
 
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Starlionblue
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 6:26 am

113312 wrote:
While this question, I'm sure, is a quest for information and knowledge, to answer it in a public forum could constitute a security risk for commercial operations. I would suggest to the site administrator that the replies be considered and filtered for potential sensitive information. I would not want to see innocent questions and well meaning answers later involved in an investigation. Access to the flight deck and equipment of the aircraft is restricted and must be secure from malevolent intervention.


What risks are we protecting from exactly? This information is widely and easily available to the public.

A quick YouTube search will show you how to access the avionics bay. This doesn't mean that access is simple for those without the required clearance.
 
VMCA787
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 7:20 am

fr8mech wrote:
Sure about that? MD11 has one that I only found out about recently.


Am I sure about that? with about 12,000 hours on various models through the 100, 200, SP, 300 and 400 freighters and PAX versions, YES! I would suggest it's kind of like your revelation on the MD-11

Sadly, I have even had the pleasure to crawl up there to get into the aircraft.
 
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77west
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 7:22 am

Just came across this picture in the thread about the stowaway on the Cargolux flight showing the 747 exterior hatch in use and thought it was interesting info for this thread

 
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747classic
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 7:58 am

All versions of the 747 have an entry hatch in zone A (slightly fwd of main entry door L1, in the aisle between the aft seats.) to enter the E &E compartment.
Just behind the nose gear strut, there is a small plug type entry door to enter the E &E compartement from outside.
At the picture below you can see the "fitst class hatch with a fixed stairs to descend into the E & E bay from inside the plane.
At the RH side you can see the movable stairs than can be put down to reach the nose gear (with the plug type door open !)

Image

Original uploaded by IAN ABBOTT at flickr, see : https://www.flickr.com/photos/ian_e_abb ... otostream/
 
classicjets
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 1:28 pm

In this ATC video, a Lufthansa pilot exits the aircraft (I believe A340) to secure an exterior panel. Given that the aircraft already taxied from the ramp, presumably he got out via the E&E compartment.

https://youtu.be/2fs9HcdhUFI

Sent from my ELE-L29 using Tapatalk
 
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thewizbizman
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 2:06 pm

celestar345 wrote:
thewizbizman wrote:
Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?


Unlikely the will need to, but you never know when you will need to. We had one incident where a power transfer relay decided to fail during a test flight, whole cockpit went black and only standby instruments available. Jumped down within 30 seconds and smacking the relay like mad to bring it back to life...


Thats a really interesting story to me. Are ATPs trained in identifying systems within the compartment and remediating errors? Or is this something some pilots just learn out of personal choice? I ask as I am a student pilot with hope of moving into the commercial world, and just want to learn as much as I can about larger aircraft.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 6:56 pm

VMCA787 wrote:
Am I sure about that? with about 12,000 hours on various models through the 100, 200, SP, 300 and 400 freighters and PAX versions, YES! I would suggest it's kind of like your revelation on the MD-11

Sadly, I have even had the pleasure to crawl up there to get into the aircraft.


An actual door? Not an access bulkhead that’s bolted on? That’s what you’re talking about. In the nose wheel well? Exactly where?

I only ask because I have 35 years in aircraft maintenance and cut me maintenance teeth on Pan Am’s 747’s, and have worked on them, or managed the workload on them, almost continuously for that time.

I’m always open to learning new stuff.
 
bigb
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 7:16 pm

Next time I do a walk around of the whale I will take a look, but I do know there is a dress panel aft of the nose gear.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 7:30 pm

bigb wrote:
Next time I do a walk around of the whale I will take a look, but I do know there is a dress panel aft of the nose gear.


I’ll walk out to one tonight. Should have one in the barn, with the NWW doors open. Might even have a stand in the wheel well.
 
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zeke
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Re: Avionics Bay Access and Pressurization

Tue Jan 25, 2022 9:06 pm

fr8mech wrote:
Our A300 have access from the flight deck. Can’t recall if that access exists on pax birds…Pan Am was a long time ago.


The flight deck is not the cabin, the cabin is the area behind the flight deck door where either passengers or cargo is carried.

thewizbizman wrote:
Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?


No, and years ago we contacted the OEMs and they confirmed this. There is no procedure that calls for that.

The reason for the access is so maintenance can carry out procedures whilst on the ground.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 3:42 am

fr8mech wrote:
I’ll walk out to one tonight. Should have one in the barn, with the NWW doors open. Might even have a stand in the wheel well.


We got a -400 in the barn. There is no access door/hatch/panel in the NWW. There is the main equipment center access door just aft of the nose gear, then there is a center equipment access door about 25 or so feet back. Both these doors are monitored by the door warning system.
 
Lpbri
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 11:37 am

I would think the crew would want access to the E&E in the event of a fire.
 
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747classic
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 12:26 pm

Here is your E & E entry hatch at a factory built 747-400ERF : the yellow hatch just aft of the second cargo loading wheel from left to right.

Image

 
RetiredWeasel
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 4:39 pm

thewizbizman wrote:
Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?


In the 747-200s there was definitely an emergency procedure for the FE to go down and unbolt a plate to release the nose gear. The wrench was even kept on a lanyard down there. This EP was noted as the last option if the first two didn't work for dropping the nose gear. During initial checkout every FE/SO went to the hanger, opened the hatch, climbed down and was shown where the bolts, the mechanism and the wrench were located.
Edit: Upon further memory digging, this procedure actually would be performed to release the nose gear door which may be keeping the gear from falling.
 
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fr8mech
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 6:18 pm

RetiredWeasel wrote:
thewizbizman wrote:
Thanks for the insight. Is there ever a reason the avionics compartment would need to be accessed by crew mid-flight?


In the 747-200s there was definitely an emergency procedure for the FE to go down and unbolt a plate to release the nose gear. The wrench was even kept on a lanyard down there. This EP was noted as the last option if the first two didn't work for dropping the nose gear. During initial checkout every FE/SO went to the hanger, opened the hatch, climbed down and was shown where the bolts, the mechanism and the wrench were located.
Edit: Upon further memory digging, this procedure actually would be performed to release the nose gear door which may be keeping the gear from falling.


Yes, there was a red painted 7/16th wrench hanging from a lanyard. There were 6(?) bolts whose heads were painted red. When removed, the nose gear door actuator would be freed. In theory, if the nose gear door actuator was preventing gear extension, the weight of the gear on the doors would be enough to push through and get the gear into the airstream.

This wrench was on my overnight maintenance checklist.
 
kalvado
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 7:48 pm

Lpbri wrote:
I would think the crew would want access to the E&E in the event of a fire.

To let air into the fire and smoke into the cockpit? Not sure how smart that is....
 
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zeke
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 8:40 pm

kalvado wrote:
To let air into the fire and smoke into the cockpit? Not sure how smart that is....


During our emergency procedures training we are put into a dark smoke filled room and asked to remove an object whilst wearing onboard protective equipment.

Pilots would be better off directing their energies into running the procedures carefully while developing a plan of what to do.
 
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Horstroad
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Re: Avionics Bay Access and Pressurization

Wed Jan 26, 2022 8:47 pm

kalvado wrote:
Lpbri wrote:
I would think the crew would want access to the E&E in the event of a fire.

To let air into the fire and smoke into the cockpit? Not sure how smart that is....

The equipment down there is ventilated anyways. It's not sealed off. Usually you can throw stuff down to the E&E compartment fwd of the rudder pedals.
 
celestar345
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Re: Avionics Bay Access and Pressurization

Thu Jan 27, 2022 10:40 am

Horstroad wrote:
kalvado wrote:
Lpbri wrote:
I would think the crew would want access to the E&E in the event of a fire.

To let air into the fire and smoke into the cockpit? Not sure how smart that is....

The equipment down there is ventilated anyways. It's not sealed off. Usually you can throw stuff down to the E&E compartment fwd of the rudder pedals.


Now that explains where all those @#$%^^%$$ down at the E&E compartment, tangled at the harnesses and cables and makes troubleshooting work horrible...
 
Woodreau
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Re: Avionics Bay Access and Pressurization

Thu Jan 27, 2022 12:33 pm

I lost a pencil in the avionics bay when I accidentally dropped it in the flight deck and caught it with my boot.

I tried to retrieve it by sliding the pencil up against the rudder adjustment thingy with my boot. And it fell into the avionics compartment.

So I had to call maintenance to retrieve my pencil.

I have no confidence that smoke would not end up in the flight deck if there was a fire in the avionics bay.
 
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zeke
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Re: Avionics Bay Access and Pressurization

Thu Jan 27, 2022 9:50 pm

Woodreau wrote:

I have no confidence that smoke would not end up in the flight deck if there was a fire in the avionics bay.


The way the ventilation works on the A320/30/40 air is drawn from the cockpit into the bay, not the other way around. It was tested as part of the certification.
 
bigb
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Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 12:54 am

No door in the nose wheel well of the 747.
 
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747classic
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Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 7:21 am

bigb wrote:
No door in the nose wheel well of the 747.


The E&E bay entry door is just aft of the aft pressure bulkhead of the nose wheel well.
See at time 05:34 : https://www.youtube.com/watch?v=OK9zhumtGg0

And : https://crewroom.alpa.org/CARGO/Desktop ... ntID=40942

When our (cargo) 747 was parked at a remote position during a night stop with no main entry door stairs available, we always used the E & E bay entrance to board our aircaft to fire up all systems, before finally the stairs arrived (always too late !) to bring up our suitcases.
 
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747classic
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Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 12:45 pm

The MD11 E & E compartment entry hatch, aft of the capt's seat.at the flightdeck. (also at the DC10 series).
See : https://www.youtube.com/watch?v=fAGR-lsjcCQ
 
bigb
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Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 7:10 pm

747classic wrote:
bigb wrote:
No door in the nose wheel well of the 747.


The E&E bay entry door is just aft of the aft pressure bulkhead of the nose wheel well.
See at time 05:34 : https://www.youtube.com/watch?v=OK9zhumtGg0

And : https://crewroom.alpa.org/CARGO/Desktop ... ntID=40942

When our (cargo) 747 was parked at a remote position during a night stop with no main entry door stairs available, we always used the E & E bay entrance to board our aircaft to fire up all systems, before finally the stairs arrived (always too late !) to bring up our suitcases.


Yes, that door is aft of the nose gear. I know that one is there as I preflight it often.

However there is no door inside of the nose wheel well, not in the nose gear wheel like it was eluded to earlier.
 
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atcsundevil
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Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 10:50 pm

It's fair to be concerned over safety and security when discussing potentially sensitive topics such as this. However, the information being discussed here is widely available on the internet. Provided no truly sensitive or compromising information is being shared, there's no reason not to have the discussion.

On a side note, please show respect for other users. There no need for personal attacks anywhere on this forum.

✈️ atcsundevil
 
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LyleLanley
Posts: 644
Joined: Wed Dec 18, 2019 9:33 pm

Re: Avionics Bay Access and Pressurization

Sat Jan 29, 2022 11:19 pm

Since that warning was for me, I’ll take the L and rephrase.

113312, this isn’t WW2 and tech ops isn’t a norden bomb sight factory or a navy shipyard. This is common knowledge anyone with a couple days experience at an airport can learn, so chill out and stop alluding to your supposed clearances and vague insider knowledge. Especially since many of us actually have those but aren’t dropping it like an EDM song. Not only does putting tech ops on blast not help your case, it hurts it.
 
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rjsampson
Posts: 546
Joined: Sat Jul 31, 2010 12:00 am

Re: Avionics Bay Access and Pressurization

Sun Jan 30, 2022 6:40 pm

I have to wonder why large avionics bays haven't gone by the wayside on newer A/C's. No doubt a modern smart phone has more than enough compute power for every system on the aircraft. Not that I'd be advocating for a central controller or anything. I have heard that a lot of the technology is deliberately "rugged" (e.g. using highly outdated, [presumably more reliable] processors like 8086's).

One would think however that reliability and redundant lightweight controllers would save a significant amount of weight, free up room for cargo, and ultimately generate substantial savings and revenue.

Any thoughts?
 
kalvado
Posts: 3664
Joined: Wed Mar 01, 2006 4:29 am

Re: Avionics Bay Access and Pressurization

Sun Jan 30, 2022 9:37 pm

rjsampson wrote:
I have to wonder why large avionics bays haven't gone by the wayside on newer A/C's. No doubt a modern smart phone has more than enough compute power for every system on the aircraft. Not that I'd be advocating for a central controller or anything. I have heard that a lot of the technology is deliberately "rugged" (e.g. using highly outdated, [presumably more reliable] processors like 8086's).

One would think however that reliability and redundant lightweight controllers would save a significant amount of weight, free up room for cargo, and ultimately generate substantial savings and revenue.

Any thoughts?

Without knowing details, as a wild guess..
There are things other than computers down there, and they may be bulky.
INS likely limited by the laser gyros - or whatever they use - and probably takes at least one position in the rack. Probably there is a backup.
Radars and radio transmitters are higher power RF devices and would need some room.
Power conversion and distribution is another bulky item which comes to mind.
Last, but not the least - at least most critical systems need backups, and those backups have to be physically separate - including power supplies. Modularity to help with quick diagnostics and component replacement
 
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zeke
Posts: 17190
Joined: Thu Dec 14, 2006 1:42 pm

Re: Avionics Bay Access and Pressurization

Sun Jan 30, 2022 10:52 pm

rjsampson wrote:
I have to wonder why large avionics bays haven't gone by the wayside on newer A/C's. No doubt a modern smart phone has more than enough compute power for every system on the aircraft. Not that I'd be advocating for a central controller or anything. I have heard that a lot of the technology is deliberately "rugged" (e.g. using highly outdated, [presumably more reliable] processors like 8086's).

One would think however that reliability and redundant lightweight controllers would save a significant amount of weight, free up room for cargo, and ultimately generate substantial savings and revenue.

Any thoughts?


The amount of compute power on a newish airliners far outperform a cell phone. The A350 for example has multiple blade servers running many avionics applications on a real time operating system. They are connected via a redundant ADFX network. The servers and networks have multiple levels of redundancy.

Have a look at this for some background info https://www.smartcockpit.com/docs/a350- ... pilots.pdf
 
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Starlionblue
Posts: 21063
Joined: Fri Feb 27, 2004 9:54 pm

Re: Avionics Bay Access and Pressurization

Sun Jan 30, 2022 11:57 pm

rjsampson wrote:
I have to wonder why large avionics bays haven't gone by the wayside on newer A/C's. No doubt a modern smart phone has more than enough compute power for every system on the aircraft. Not that I'd be advocating for a central controller or anything. I have heard that a lot of the technology is deliberately "rugged" (e.g. using highly outdated, [presumably more reliable] processors like 8086's).

One would think however that reliability and redundant lightweight controllers would save a significant amount of weight, free up room for cargo, and ultimately generate substantial savings and revenue.

Any thoughts?


Computers are smaller but there are a lot more of them on a modern aircraft than on an older one. There is also much more redundancy and error detection correction capability.

Certainly small units are possible, but we're talking a working vehicle. Being able to replace a unit with a large, rugged casing and a big handle in the field has value, even if the computer inside isn't that massive. The Airbus flight control computers don't really have to do very much in modern computing terms, but the package is a relatively bulky thing with a handle.

As mentioned above, not everything in there is just a computer either.

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