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HAWK21M
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B752 Main L/G Door Closure On Ground Video.

Thu Jul 05, 2007 4:57 am



Theres is quite a T/D between both gear doors closing.Unless its due to air in the lines due a component replacement.
Views.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
rendezvous
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 05, 2007 12:06 pm

Maybe this was a retraction using the alternate system?
 
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jetmech
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 05, 2007 12:43 pm

Quoting HAWK21M (Thread starter):

I don't know how it is with a 757, but on the 767 and A330 / A340, there are separate handles for manual opening of each set of main gear doors. Is there only one handle for both main gear doors on the 757?

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 05, 2007 5:12 pm

Quoting JetMech (Reply 2):
Is there only one handle for both main gear doors on the 757

One Switch for Arming & One Switch for Lowering.needs momentary contact.
There is one test sw for the Safe light & One sw for the retraction of all Three [Nose & Main] gear doors.

Hence lowering has to be done from Nose [P62] for Nose gear doors & Main wheel well panel [P72] for Maingear doors.But retraction of doors has to be done from P72 panel for all.

regds
MEL
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jetmech
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RE: B752 Main L/G Door Closure On Ground Video.

Sun Jul 08, 2007 10:04 am

Thanks MEL,

Quoting HAWK21M (Reply 3):
Hence lowering has to be done from Nose [P62] for Nose gear doors & Main wheel well panel [P72] for Maingear doors.

It appears that there is another difference between the 757 / 767. On the 767, the nose gear doors are opened and closed manually by hand. The nose gear doors are driven by the gear itself, with part of the linkage having a manually activated telescoping action to allow opening on the ground.

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
A/c train
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 3:50 am

HAWK21, You have the door opening sequence the wrong way round, to lower the doors, you select 2 switches )arm and lower I think), ill know when I see the panel as the decals are usually worn off with skydrol anyway, these switches are in the panel aft of the r/h mlg door. (dont remember panel numbers), you will then hear the altn extend power pack run and funnily enough that is the test for that system( OOP check) on some airlines, on selecting this, all the doors will open and you check for the red light, red light, = doors unsafe(literally with safety vaalve pstn).
To raise the doors, you select left system ACMP on, and raise the Main gear doors from the aft r/h mlg door panel and the nose doors off the nose leg panel, aft l/h side.

767 NLG doors are as Jet mech says mechanically connected to the nose leg through bellcrank and pogo rods, hence when nose gear extended, they will appear to droop, this is normal and will be flush provided rigging is correct on retraction, so no bother.
To open 767 NLG doors, pull the ring pull on both sides, this lever is on the telescopic strut, to open MLG doors, 2 handles in WTB fairings aft of relevant MLG door, cable system from handle, 2 raise MLG doors reverse operation with umm umm cant remember which system, ?? brakes is R and C so C being the the BIG system on a 767, I would say centre system ACMP, give away with the ADP being in the C system for high demand, hence its known as a Demand pump.
For NLG doors, just push up and here the locking cam engage. Sometimes it doesnt, try pushing harder, if no luck, you may have to do some lateral thinking with the pogo strut, if you mess with the rigging of that strut, you must swing the leg for rigging checks, you CAN jack the nose of a 767 BTW, you must read the AMM for specific fuel loads when doing this for C of G pstn.
ive gassed too much.
regds a/c
 
Mender
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 4:56 am

What I saw in the video appeared to be completely normal to me. In normal operation the resistance cause by air loads should even up the door closure speeds.

If you've ever seen a full gear retraction on jacks you'll understand. It's quite normal for one gear to partially retract before the other starts to retract. For example, you could see the left gear side brace unlock and the left gear partially retract to about 45 degrees then the right gear side brace unlock and the right gear fully retract with the left still about 45 degrees. Once the right gear is fully up then the left will go fully up. What's more if you repeated the test, it would happen the other way round with the right gear moving first. Sometimes the nose gear will partially retract, then, when a main gear starts to retract the nose gear will fall a little before going fully up.

It's not because one gear is stiff or anything, it's because the ACMP on it's own doesn't produce enough hydraulic flow. It really needs the flow from the EDP. This is why Boeing recommend the use of a hydraulic rig for gear retraction tests.
 
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jetmech
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 12:58 pm

JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 6:02 pm

Quoting HAWK21M (Reply 3):
One Switch for Arming & One Switch for Lowering.needs momentary contact



Quoting A/c train (Reply 5):
You have the door opening sequence the wrong way round, to lower the doors, you select 2 switches )arm and lower I think

Wasn't that what I said.Only momentry ctc is needed for the Powerpack to function.
regds
MEL
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SNA350
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 6:23 pm

where are those activation switches located?
Aircraft flown: B733, B734, B736, B737, B738, B744, B752, B763, B772, A319, A320, A321, A343, A346, Do328, CRJ7, E190
 
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 7:02 pm

Quoting SNA350 (Reply 9):
where are those activation switches located

For the Main Gear LH of the RAT Panel aft of MWW & for the Nose gear LH NLG panel.
regds
MEL
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Mon Jul 09, 2007 7:05 pm

Quoting HAWK21M (Reply 3):
Hence lowering has to be done from Nose [P62] for Nose gear doors & Main wheel well panel [P72] for Maingear doors.But retraction of doors has to be done from P72 panel for all.

A typo correction .....Hence lowering has to be done from Main wheel well panel [P72] for Nose gear doors & for Maingear doors.But retraction of doors has to be done from P72 panel for Main Gear doors & P62 for Nose gear doors.
regds
MEL
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EMBQA
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RE: B752 Main L/G Door Closure On Ground Video.

Tue Jul 10, 2007 1:27 am

Quoting Mender (Reply 6):
It's not because one gear is stiff or anything, it's because the ACMP on it's own doesn't produce enough hydraulic flow. It really needs the flow from the EDP.

My thoughts as well. When doing gear swings on the E190 its the same way. Select gear up and the mains break over, then slowly retract... once the mains are up, then the nose breaks over and goes up.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
A/c train
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RE: B752 Main L/G Door Closure On Ground Video.

Tue Jul 10, 2007 4:10 am

Hawk21, your typo correction was what I meant.
 
MD11Engineer
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RE: B752 Main L/G Door Closure On Ground Video.

Tue Jul 10, 2007 4:22 am

Quoting HAWK21M (Reply 3):
Quoting JetMech (Reply 2):
Is there only one handle for both main gear doors on the 757

One Switch for Arming & One Switch for Lowering.needs momentary contact.
There is one test sw for the Safe light & One sw for the retraction of all Three [Nose & Main] gear doors.

Hence lowering has to be done from Nose [P62] for Nose gear doors & Main wheel well panel [P72] for Maingear doors.But retraction of doors has to be done from P72 panel for all.

regds
MEL

The 757 uses a small DC operated hydraulic pump to pressurise the main wheel well door and main landing gear up lock unlock actuators for opening the doors on ground. This pump is normally used to drop the gear in alternate mode (failure of the IIRC Right hydraulic system). It has it's won little reservoir (actually just a length of large diameter pipe and is located on the fwd keel beam in the RH main wheel well. It also provideds pressure to operate the nose gear door actuator and the nose gear lock actuator, when the gear is retracted, just enough to get over the overcentering of the drag strut, to let the gear then fall by gravitation and slipstream.
The reason why you are only supposed to hold the "open" switch momentarily is that an operation of this pump for longer periods can cause it's motor to burn out.
The pump usually only provides enough volume to unlock one actuator at a time.
Closing the doors is done by using the normal hydraulic system. For safety reasons the nose gear door has a seperate switch on the nose gear panel, so that the person closing either the main doors or the nose door will be right beside the respective door to prevent accidents.


Jan
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Tue Jul 10, 2007 8:01 pm

Quoting MD11Engineer (Reply 14):
This pump is normally used to drop the gear in alternate mode (failure of the IIRC Right hydraulic system).

Its termed the "Power Pack"

Quoting MD11Engineer (Reply 14):
The reason why you are only supposed to hold the "open" switch momentarily is that an operation of this pump for longer periods can cause it's motor to burn out.

True.

Quoting MD11Engineer (Reply 14):
The pump usually only provides enough volume to unlock one actuator at a time

I don't agree Jan.The Hydraulic fluid used for unlocking is minimum from that stored in the line & used by the powerpack.

regds
MEL
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MD11Engineer
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RE: B752 Main L/G Door Closure On Ground Video.

Tue Jul 10, 2007 8:58 pm

Quoting HAWK21M (Reply 15):
Quoting MD11Engineer (Reply 14):
The pump usually only provides enough volume to unlock one actuator at a time

I don't agree Jan.The Hydraulic fluid used for unlocking is minimum from that stored in the line & used by the powerpack.

regds
MEL

The three actuators (two for the main wheel doors, one for the nose) will have tolerances and usually one will be a bit harder to open than the other. So the actuator with the lesser resistance unlocks first and the other one a little bit later, as soon as the first is fully extended, because in meantime the little pump has to fill up the first actuator's volume to equalise the pressure drop which happens while the first actuator extends. Full pressure in the pipes will only be reached after the first actuator reached it's end stops. Only then will there be enough pressure again to unlock the second actuator. Next time you open the gear doors, watch them: One will open first and the other one maybe a second later.

Jan
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Wed Jul 11, 2007 12:21 am

Quoting MD11Engineer (Reply 16):
Next time you open the gear doors, watch them: One will open first and the other one maybe a second later.

Agreed.you stated one actuator at a time which I disagree.Every actuator will be different & hence the opening time will vary slightly.Explain the closing doors as in the video.Is that Hydraulic lock related.
regds
MEL
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MD11Engineer
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RE: B752 Main L/G Door Closure On Ground Video.

Wed Jul 11, 2007 2:00 am

Same story:

You can see when the guy pressed the "arm" and "Close" switches, because at this moment the warning light starts flashing. You can also hear the hydraulic pump producing flow (change of sound). This means that temporarely the hydraulic pressure drops. As soon as the first door is closed and the actuator stops moving, the other door starts to close.
Apparently the left actuator was a bit easier to move then the other one. This is completely normal. I worked 757s for 5 years in CGN and there is ALWAYS a delay on both opening and closing the doors.

Jan
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Mender
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RE: B752 Main L/G Door Closure On Ground Video.

Wed Jul 11, 2007 6:30 am

I agree with MD11Engineer.

IIRC The door actuator needs a certain pressure to unlock (without pressure you can't simply push the door closed) whichever actuator unlocks first lowers the pressure in the system whilst it is receiving hydraulic flow. Once it closes the hydraulic flow stops and the hydraulic pressure builds up and unlocks the other actuator. Watch the pressures on EICAS the next time you close the gear doors and you'll see the pressure drop when the actuators move.

I haven't seen/heard the video with sound on. Neither can we can't see if someone is trying to close the nose gear doors at the same time. This would really drop the system pressure.

Anyway, the big question is why has the bloke still got his hand on the switch once he's flicked it. Is he holding the switch in the closed position all the time?

Whatever he's doing he's wasting his time. Once the switch has been flicked he cannot stop the doors closing from there and he doesn't need to hold it in the closed position while the doors operate.
 
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Wed Jul 11, 2007 5:11 pm

Quoting MD11Engineer (Reply 18):
I worked 757s for 5 years in CGN and there is ALWAYS a delay on both opening and closing the doors.

A small T/D I understand but such a long delay that one door closes before the 2nd door starts closing seems abnormal.

Quoting Mender (Reply 19):
Anyway, the big question is why has the bloke still got his hand on the switch once he's flicked it. Is he holding the switch in the closed position all the time?

Whatever he's doing he's wasting his time. Once the switch has been flicked he cannot stop the doors closing from there and he doesn't need to hold it in the closed position while the doors operate

Shouldn't closing the door close Sw be held in until the doors totally close.Only the Open & Arm sw should be held momentarily to avoid burn out.

regds
MEL
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A/c train
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RE: B752 Main L/G Door Closure On Ground Video.

Wed Jul 11, 2007 11:55 pm

The reason you do this test of the altn extension powerpack on an OOP is beacuse they are prone to icing and moisrure ingress due to there location, the test is just to drop the doors and listen, correct me if im wrong, but you dont need to select armed to raise the doors, just L/H system pressure and hold the switch to close for a couple of secs?? you will get red unsafe light and one door will raise and be nearly closed before the other, then the NLG doors, the NLG doors can be a problem sometimes.
One way to get around this is just to let the system pressure decay and start again, i.e, switch pump off then on, or get your broom out and poke the safety valve/ microswitch mechanism, fwd face of the NLG bay. Last but not least, stick the pins in and hit lock override, the rest is history !!!
 
fr8mech
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 12, 2007 1:39 am

This is excerpted from the AMM:

Opening the doors:

3) Supply electrical power (Ref 24-22-00).

S 012-014

WARNING:MAKE SURE THERE ARE NO PERSONS OR EQUIPMENT AROUND THE NOSE OR MAIN LANDING GEAR BEFORE YOU OPEN THE DOORS. THE DOORS OPEN AND CLOSE QUICKLY AND CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT.

CAUTION:DO NOT OPERATE THE POWER PACK (ALTERNATE EXTEND) FOR MORE THAN FIVE MINUTES. AND Irtysh-Avia (Kazakhstan)">IT CAN BECOME TOO HOT. THIS CAN CAUSE DAMAGE TO THE MOTOR.

(4) Do not operate the power pack until it becomes cool:

(a) Let the temperature of the power pack motor become less than 150°F before you operate it again.

NOTE:If you cannot measure the temperature of the motor, let it become cool until you can touch it with your hand.

S 862-074

(5) Open the ground control access door, 198PR (Ref 06-41-00), to get access to the electrical service panel, P72, for the main wheel well (Fig. 201).

S 862-016

CAUTION:DO NOT HOLD THE "ALL DOORS OPEN" SWITCHES IN THE "ARM" AND "OPEN" POSITIONS FOR MORE THAN TWO (2) SECONDS. IF YOU HOLD THE SWITCHES TOO LONG, THE POWER PACK CAN BECOME TOO HOT, AND CAN CAUSE THE ALTERNATE EXTENSION SYSTEM TO NOT OPERATE.

(6) At the same time, move the ALL DOORS OPEN ARM switch to the ARM position and the ALL DOORS OPEN switch to the OPEN position.

NOTE:The power pack releases the doors but does not put the doors in the open position.

(a) The main and nose landing gear doors will come open.

(b) If it is necessary, manually put the doors to the fully open position.

S 862-017

WARNING:MAKE SURE THE PRESSURE IS REMOVED FROM THE LEFT AND RIGHT HYDRAULIC SYSTEMS BEFORE YOU GO INTO THE WHEEL WELLS TO INSTALL THE DOOR LOCKS. INJURY TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR IF THE SYSTEM IS PRESSURIZED.

(7) Remove the pressure from the left and right hydraulic systems and reservoirs (Ref 29-11-00)

Closing the doors:

(1) Pressurize the left hydraulic system and reservoirs (Ref 29-11-00).

S 842-049

(2) Move the MAIN GEAR DOOR CLOSE switch to the DOOR CLOSE position, to close the main landing gear doors.

S 412-051

(3) Close the access door 198PR (Ref 06-41-00).

S 842-053

(4) Move the NOSE GEAR DOOR CLOSE switch to the DOOR CLOSE position, to close the nose landing gear doors.

S 862-054

(5) Remove the hydraulic power if it is not necessary (Ref 29-11-00).

S 862-055

(6) Remove the electrical power if it is not necessary (Ref 24-22-00).

Now, someone from Delta confirm this, but I recall that Delta's aircraft do not use the alternate extend system to open the doors. They have a mechanical linkage which moves the lock. Correct?

I suspect the doors are closing slowly and unevenly because of system pressure. Someone is probably closing the nose doors at the same time. I won't say I see this everytime I've witnessed or operated the doors closed on the ground, but this is far from abnormal.

As I recall, from operating the doors, the door closed switch is actuated and the doors close, you do not have to hold it in the closed position.
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HAWK21M
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 12, 2007 3:21 am

Quoting Fr8mech (Reply 22):
As I recall, from operating the doors, the door closed switch is actuated and the doors close, you do not have to hold it in the closed position

Isn't it a momentary switch,that needs to be held in the closed position until both nose gear Doors are closed,which can be confirmed with "Doors" Annunciator light extinguishing. on P3.
regds
MEL
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fr8mech
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 12, 2007 4:16 am

It is a momentary switch, but once the sequence starts it continues. I'm away from the WDM right now, but I'm sure a holding relay is used. I used to hit the switch, close the panel and move on to bigger and better things.
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Mender
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RE: B752 Main L/G Door Closure On Ground Video.

Thu Jul 12, 2007 4:51 am

Quoting HAWK21M (Reply 23):
Isn't it a momentary switch,that needs to be held in the closed position until both nose gear Doors are closed

It's as Fr8Mech states and this is true of both the nose and the mains, hence......

Quoting Mender (Reply 19):
Anyway, the big question is why has the bloke still got his hand on the switch once he's flicked it.

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