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HAWK21M
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Mdcd Mechanisms.

Sat Dec 22, 2007 3:05 pm

Can Anyone Add to the Various MDCD [Main Deck Cargo door] control systems in place Worldwide.
Phosphate Ester based fluid like Skydrol & Mineral Based Fluid like MIL-H-5606 systems are Available.In the Former it can be built into the Aircraft system or Isolated.

The Holding of the door in open position can be by Hydraulic Actuator Mechanical locks- requiring Hyd pressure to release or the common Holding valve.

Can anyone add to this...
The above is common to B737 & B757 Freighters.....What about the MD11,B747,B727,B707,A300,A310,B767 freighters.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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jetmech
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RE: Mdcd Mechanisms.

Sat Dec 22, 2007 3:40 pm



Quoting HAWK21M (Thread starter):

The 747 main cargo deck doors (side and nose) are electrically powered.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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fr8mech
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RE: Mdcd Mechanisms.

Sat Dec 22, 2007 6:17 pm



Quoting JetMech (Reply 1):
The 747 main cargo deck doors (side and nose) are electrically powered.

Evergreen used to, and may still, operate the Pemco door (at least I think it was Pemco). That was hydraulic.

Our B767's are electric, main and lower.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
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HAWK21M
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RE: Mdcd Mechanisms.

Sat Dec 22, 2007 9:19 pm



Quoting JetMech (Reply 1):
The 747 main cargo deck doors (side and nose) are electrically powered

That would need to be Reliable Motor.What is the back up.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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jetmech
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RE: Mdcd Mechanisms.

Sun Dec 23, 2007 12:36 am



Quoting Fr8mech (Reply 2):
Pemco door

No worries. I'm sure that Boeing installed main cargo doors are electrically powered.

Quoting HAWK21M (Reply 3):
What is the back up.

The backup is manual winding using a speed brace (either 3/8" or 1/2" drive, not sure). On 747 cargo doors, the latching mechanism is also electrically driven, so you would need to manually wind at two or three separate locations to manually open or shut a door.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
kaddyuk
Posts: 3697
Joined: Thu Nov 08, 2001 1:04 am

RE: Mdcd Mechanisms.

Sun Dec 23, 2007 5:38 am



Quoting JetMech (Reply 4):
The backup is manual winding using a speed brace (either 3/8" or 1/2" drive, not sure). On 747 cargo doors, the latching mechanism is also electrically driven, so you would need to manually wind at two or three separate locations to manually open or shut a door.

Had to wind open and close the lower deck cargo doors on a B767 yesterday. After it departed a pax went sick and it came back on stand, they unloaded the passenger and got me to wind the aft door open a second time...

It takes 1200ish turns to open each door and you cant use an electric drill because they dont have enough torque.

My shoulder hurts now...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
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HAWK21M
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RE: Mdcd Mechanisms.

Mon Dec 24, 2007 7:10 am



Quoting JetMech (Reply 4):
No worries. I'm sure that Boeing installed main cargo doors are electrically powered.

Electrically controlled hydraulically operated.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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fr8mech
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RE: Mdcd Mechanisms.

Mon Dec 24, 2007 5:49 pm



Quoting Kaddyuk (Reply 5):
It takes 1200ish turns to open each door and you cant use an electric drill because they dont have enough torque.

We use an air rachet on that particular door.

Quoting HAWK21M (Reply 6):
Electrically controlled hydraulically operated.

No, the B747 main door (Boeing installed) is completely electric in operation. 1 latch actuator, 2 hook actuators and 1 lift actuator. Each can be operated with a speed handle or high output screwgun.

As I recall, the B757 main door is hydraulic in operation. The door is sequenced using priority valves, not swtiches. It is controlled using a switch by the entry door, but he switch just controls the bypass valve and directional control valve.

Quoting JetMech (Reply 4):
No worries. I'm sure that Boeing installed main cargo doors are electrically powered.

The Pemco door sucked. Hydraulic operation, with a laser for a door warning system. Good in theory, but after a couple of cycles the grease would fill the holes that the laser shot through. Pain in the butt.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
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jetmech
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RE: Mdcd Mechanisms.

Mon Dec 24, 2007 8:08 pm



Quoting Fr8mech (Reply 7):
Good in theory, but after a couple of cycles the grease would fill the holes that the laser shot through. Pain in the butt.

That's different! I presume that pain in the butt aspect was false warnings of an open door configuration?

Quoting Fr8mech (Reply 7):
No, the B747 main door (Boeing installed) is completely electric in operation.

I'm pretty sure that Boeing installed nose cargo doors on the 747 are completely electric as well. Is there any group doing aftermarket nose cargo door fitments to 747's?

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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TZTriStar500
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RE: Mdcd Mechanisms.

Mon Dec 24, 2007 9:33 pm

From my past work experience and research the MCD mechanisms that I've come across are:

*737-200/-300/-400 all aftermarket STCs (Pemco, AEI, IAI/Bedek) are independent hydraulically actuated SKYDROL based systems. Althought Pemco did develop an electromechanical system for their -200/-300 STC, it was only installed on two -200s that originally went CanAir Cargo.
*727-100/-200 All STCs where independent hydraulically operated with either 5606 or SKYDROL.
*747 Boeing factory built where all electromechanical. The first STC was designed by PEMCO for GATX/AirLog which owned it....not sure who owns it now, but was fraught with reliability problems, ADs, and poor workmanship.

One interesting aspect of the narrowbody cargo door STCs was that most of them used an original Douglas designed overcenter latch from the 1950's....great design that latched over horizontal pins in the lower door sill and when it went overcenter all outward force on it (e.g. from pressurization) actually placed further force on it in the closed direction.
35 years of American Trans Air/ATA Airlines, 1973-2008. A great little airline that will not be soon forgotten.
 
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HAWK21M
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RE: Mdcd Mechanisms.

Tue Dec 25, 2007 3:19 am



Quoting Fr8mech (Reply 7):
the B757 main door is hydraulic in operation. The door is sequenced using priority valves, not swtiches. It is controlled using a switch by the entry door, but he switch just controls the bypass valve and directional control valve.

Thats true for the -SF,In build to the LH Hydraulic system.The -PCF use an Isolated Hydraulic [Skydrol] system.

Quoting TZTriStar500 (Reply 9):
737-200/-300/-400 all aftermarket STCs (Pemco, AEI, IAI/Bedek) are independent hydraulically actuated SKYDROL based systems

Our Five B732SFs use MIL-H-5606 as a seperate MDCD operating system using an Electric motor & Hand pump backup.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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TZTriStar500
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RE: Mdcd Mechanisms.

Tue Dec 25, 2007 4:38 am



Quoting HAWK21M (Reply 10):
Our Five B732SFs use MIL-H-5606 as a seperate MDCD operating system using an Electric motor & Hand pump backup.

Yes, you are correct. I forgot that the AEI door uses 5606.
35 years of American Trans Air/ATA Airlines, 1973-2008. A great little airline that will not be soon forgotten.
 
kaddyuk
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RE: Mdcd Mechanisms.

Tue Dec 25, 2007 7:06 pm



Quoting Fr8mech (Reply 7):
We use an air rachet on that particular door

Not too easy to get an air driven rachet out to a remote stand though is it?? :P
Whoever said "laughter is the best medicine" never had Gonorrhea
 
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fr8mech
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RE: Mdcd Mechanisms.

Wed Dec 26, 2007 2:35 am



Quoting Kaddyuk (Reply 12):
Not too easy to get an air driven rachet out to a remote stand though is it?? :P

Nitrogen carts are beautiful things, when the bottles are full.

Quoting JetMech (Reply 8):
That's different! I presume that pain in the butt aspect was false warnings of an open door configuration?

Yup.

Quoting JetMech (Reply 8):
I'm pretty sure that Boeing installed nose cargo doors on the 747 are completely electric as well. Is there any group doing aftermarket nose cargo door fitments to 747's?

I'm going to guess it is cost prohibitive.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
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HAWK21M
Topic Author
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RE: Mdcd Mechanisms.

Wed Dec 26, 2007 4:29 am



Quoting Fr8mech (Reply 13):
Nitrogen carts are beautiful things, when the bottles are full.


Arn't they supposed to be.  Smile

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
kaddyuk
Posts: 3697
Joined: Thu Nov 08, 2001 1:04 am

RE: Mdcd Mechanisms.

Wed Dec 26, 2007 10:29 am



Quoting HAWK21M (Reply 14):
Arn't they supposed to be.

I wish I had one £/$/€ for every time I dragged a nitrogen cart out to top up a door assist bottle and found it to be at the 1200psi mark... LoL!
Whoever said "laughter is the best medicine" never had Gonorrhea
 
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HAWK21M
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RE: Mdcd Mechanisms.

Wed Dec 26, 2007 8:52 pm



Quoting Kaddyuk (Reply 15):
I wish I had one £/$/€ for every time

Your Fonts look weird.Could you rephrase that sentence.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
A/c train
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RE: Mdcd Mechanisms.

Sun Jan 20, 2008 1:17 pm

Flap drive tool for cargo doors, cordless may have the guts, ive wound reverser sleeves back with cordless drills. Its the apprentice duty to do things like that anyway ! I only do it when I dont have an apprentice.
Top hyds up when pipes burst dumping system contents using the flex pipe and handle supplied with aircraft. Character building.
 
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HAWK21M
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RE: Mdcd Mechanisms.

Sun Jan 20, 2008 6:25 pm



Quoting A/c train (Reply 17):
ive wound reverser sleeves back with cordless drills

The Torque limitations is the key & has not to be exceeded.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
MD11Engineer
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RE: Mdcd Mechanisms.

Sun Jan 20, 2008 8:02 pm

The MD-11 uses a hydraulically operated MCD. It has it's own small reservoir and pumps (one electric, one manual) in the nose wheel well. There exist two variants:
The one originally designed by Douglas (which is AFAIK also used on the DC-10), which requires the door to be manually unlocked from inside (or from outside from the main deck loader) and uses a simple manually (by a T-handle) operated valve with a microswitch to start the pump attached under a panel in the cabin floor just inside the main entry doo to operate the latch actuator and the lift actuator (controlled by sequence valves). This system is virtually foolproof.

Then there exists the Boeing redesign, which was adopted e.g. by UPS. There the manual valve was replaced by two electrical actuated ones in the nose wheel well, which were operated by push buttons in a panel just aft of the main entry door. This system also had a seperate lockpin unlock actuator and a latch actuator.
The problem was that the electric valves of gave trouble, leading to loading delays, especially if the plane had a long trip and the valves were cold soaked. In this case the valves had to be manually overridden and the door manually unlatched from the outside. We also experience problems if the pressure relief doors in the MCD were frozen into position (e.g. if the plane had departed from a hot, humid place, e.g. in India or Hong Kong and flown to cold Europe).
Then the latch actuator was not strong enough to open the relief doors (besides moving the locks). In this case you had to assist by pushing on the relief doors from the outside.
The lockpin unlock actuator, the latch actuator and the lift actuator were controlled by sequence valves.

The only advantage of this much more complicated system was that the pilots did not have to go on their knees anymore to open the door.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
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HAWK21M
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RE: Mdcd Mechanisms.

Sun Jan 20, 2008 9:09 pm

Quoting MD11Engineer (Reply 19):
The MD-11 uses a hydraulically operated MCD

What fluid Mineral based or phosphate ester based ?
regds
MEL.

[Edited 2008-01-20 13:10:35]
I may not win often, but I damn well never lose!!! ;)
 
MD11Engineer
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RE: Mdcd Mechanisms.

Sun Jan 20, 2008 9:22 pm



Quoting HAWK21M (Reply 20):
Quoting MD11Engineer (Reply 19):
The MD-11 uses a hydraulically operated MCD

What fluid Mineral based or phosphate ester based ?
regds
MEL.

Phosphate ester based.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
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HAWK21M
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RE: Mdcd Mechanisms.

Mon Jan 21, 2008 8:56 am



Quoting MD11Engineer (Reply 21):
Phosphate ester based.

Our B732SFs use MIL-H-5606 & remote system.
The B752SFs use skydrol & from LH Hyd system.
The B752PCF use skydrol & remote system.

regds
MEL
I may not win often, but I damn well never lose!!! ;)

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