Cargolux nose gear collapse in Shanghai.
Combine Operations
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But the difference is that in this incident the aircraft is on the ground, and the operating mechanism, as I understand it, is in the wheel bay.
Why does anyone need to enter a wheel bay and deliberately retract the undercarriage when the aircraft is not on jacks?
Am I missing something obvious? Please be gentle.
Why does anyone need to enter a wheel bay and deliberately retract the undercarriage when the aircraft is not on jacks?
Am I missing something obvious? Please be gentle.
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quote:
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
There are plenty of reasons to simulate a gear up situation on the ground and to actuly swing the gear with a/c on the ground.the big differance is one is done on jacks (normally) and the other is done FOLLOWING the maint manual procedures (boeing not only designed the plane but the maint manual aswell).things like replacing hydraulic valves or pipes will need tobe pressure/leak checked-this can be done without a full gear swing as most airports in the world will not have the jacks readly avail for your a/c type-and they are big expensive things to have or ship.
The downlock pins used by maint will stop the gr moving-fullstop.
due the overcentering of the mechenism they are not resisting the full power on the actuators
quote:
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
There are plenty of (maint) reasons to simulate a gear up situation on the ground and to actually swing the gear with a/c on the ground.the big difference is one is done on jacks (normally) and the other is done FOLLOWING the maint manual procedures (Boeing not only designed the plane but the maint manual as well).things like replacing hydraulic valves/actuators or pipes will need to be pressure/leak checked-this can be done without a full gear swing as most airports in the world will not have the jacks readily avail for your a/c type-and they are big expensive things to have or ship.
The downlock pins used by maint will stop the gr moving-fullstop.
due the over centering of the mechanism they are not resisting the full power on the actuators
hope this helps
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
There are plenty of reasons to simulate a gear up situation on the ground and to actuly swing the gear with a/c on the ground.the big differance is one is done on jacks (normally) and the other is done FOLLOWING the maint manual procedures (boeing not only designed the plane but the maint manual aswell).things like replacing hydraulic valves or pipes will need tobe pressure/leak checked-this can be done without a full gear swing as most airports in the world will not have the jacks readly avail for your a/c type-and they are big expensive things to have or ship.
The downlock pins used by maint will stop the gr moving-fullstop.
due the overcentering of the mechenism they are not resisting the full power on the actuators
quote:
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
There are plenty of (maint) reasons to simulate a gear up situation on the ground and to actually swing the gear with a/c on the ground.the big difference is one is done on jacks (normally) and the other is done FOLLOWING the maint manual procedures (Boeing not only designed the plane but the maint manual as well).things like replacing hydraulic valves/actuators or pipes will need to be pressure/leak checked-this can be done without a full gear swing as most airports in the world will not have the jacks readily avail for your a/c type-and they are big expensive things to have or ship.
The downlock pins used by maint will stop the gr moving-fullstop.
due the over centering of the mechanism they are not resisting the full power on the actuators
hope this helps
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It is no simple method to get the gear up, it is a very deliberate action and the override system is installed as said for the benefit of the cockpit crew, so that in the event of a failure of the system to think it's off the ground the crew can have a quick check to ensure the gear is centered and in the tilt position and then in a two handed operation, remove the guard (classic) push the LOCK OVRD button (-400) and with the other hand pull (extend) the gear lever out to clear the detent and then lift it through OFF and into the UP detent.
These are some reasons to move the gear lever on the ground:
1. You want to check the retract system (put it on jacks select gear up) very impressive to watch.
2. You want to leak check the "UP" side of the system (put the down-lock pins in). Using the override, select gear up.
3. You want to check the gear doors (put the down-lock pins in). Using the override, select gear up.
There is a manual release for the doors (one left side of nose gear other left body gear wheel well), but they don't open hydraulically they just free-fall open then close hydraulically, this is why you will have to use the gear lever if you want them to open hydraulically.
4. You want to get the F/Os CDU/FMS which may foul with the gear lever (put the pins in). Using the override as well select gear to up or off.
The original CDU on the classic didn't foul with the gear as it was half as big and could be moved to avoid the gear lever.
So basically if you're going to deliberately move the gear lever, deliberately put the pins in.
These are some reasons to move the gear lever on the ground:
1. You want to check the retract system (put it on jacks select gear up) very impressive to watch.
2. You want to leak check the "UP" side of the system (put the down-lock pins in). Using the override, select gear up.
3. You want to check the gear doors (put the down-lock pins in). Using the override, select gear up.
There is a manual release for the doors (one left side of nose gear other left body gear wheel well), but they don't open hydraulically they just free-fall open then close hydraulically, this is why you will have to use the gear lever if you want them to open hydraulically.
4. You want to get the F/Os CDU/FMS which may foul with the gear lever (put the pins in). Using the override as well select gear to up or off.
The original CDU on the classic didn't foul with the gear as it was half as big and could be moved to avoid the gear lever.
So basically if you're going to deliberately move the gear lever, deliberately put the pins in.
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Originally Posted by Volume
The guys in the Concorde would have been lucky if they would had the chance to override the ground sensor with the severed wiring and power the hydraulic system with two engines not running, just to get that damn gear up and the drag reduced.
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Originally Posted by SMOC
These are some reasons to move the gear lever on the ground:
1. You want to check the retract system (put it on jacks select gear up) very impressive to watch.
2. You want to leak check the "UP" side of the system (put the down-lock pins in). Using the override, select gear up.
3. You want to check the gear doors (put the down-lock pins in). Using the override, select gear up.
There is a manual release for the doors (one left side of nose gear other left body gear wheel well), but they don't open hydraulically they just free-fall open then close hydraulically, this is why you will have to use the gear lever if you want them to open hydraulically.
4. You want to get the F/Os CDU/FMS which may foul with the gear lever (put the pins in). Using the override as well select gear to up or off.
The original CDU on the classic didn't foul with the gear as it was half as big and could be moved to avoid the gear lever.
So basically if you're going to deliberately move the gear lever, deliberately put the pins in.
1. You want to check the retract system (put it on jacks select gear up) very impressive to watch.
2. You want to leak check the "UP" side of the system (put the down-lock pins in). Using the override, select gear up.
3. You want to check the gear doors (put the down-lock pins in). Using the override, select gear up.
There is a manual release for the doors (one left side of nose gear other left body gear wheel well), but they don't open hydraulically they just free-fall open then close hydraulically, this is why you will have to use the gear lever if you want them to open hydraulically.
4. You want to get the F/Os CDU/FMS which may foul with the gear lever (put the pins in). Using the override as well select gear to up or off.
The original CDU on the classic didn't foul with the gear as it was half as big and could be moved to avoid the gear lever.
So basically if you're going to deliberately move the gear lever, deliberately put the pins in.
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Originally Posted by ARINC
But surely all this is done on Jacks !!! No need whatsoever to have a live system with weight on...an accident waiting to happen
The problem with the B747 is that the nose gear downlock pin is out of sight. It is high up in the bay and the visual access is very poor, unless the fwd doors are open.
The other B747 problem is that it is a big aircraft. I am lucky, I work on the line by myself. If I put the pins in, they will stay in until I take them out. At a main base there will be many people working the aircraft at the same time, and if you select UP with hyd px on and someone else has removed the pin (or it has fallen out as happened at BA recently!), the nose gear will retract.
Combine Operations
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Originally Posted by nitro rig driver
quote:
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
I cannot come up with a reason for there ever being a need to retract the undercarriage while the aircraft is on the ground, with or without power; or imagine such an event without major damage being caused, and possibly injury or death. This is a Murphy if ever there was one.
Despite the various attempts by some obviously very clever people above, I'm afraid I'm at the bottom of the class on this. I still fail to see how, if you have weight on the wheels and you raise those wheels, those wheels are actually going to rise. All I can see happening is the aircraft is going to sink. This is, after all, exactly what happened in this incident, and others. What is going to support the aircraft's weight? Weight on wheels, remember - no jacks.
If the preceding paragraph is, by some miracle, correct, then we return to question which I seem to have stolen: why should an aircraft have designed into it a system to raise the undercarriage whilst on the ground, with weight on the wheels?
Perhaps it should be called an aircraft lowering system.
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Originally Posted by Farmer 1
why should an aircraft have designed into it a system to raise the undercarriage whilst on the ground, with weight on the wheels?
The fact the A/C is on the ground means the gear is not tilted and therefore means the gear lever is prevented from being selected up.
The OVRD system is installed to allow the flight crew to select the gear up in case the gear lever is prevented from being selected up after checking the gear is centered and all the main gear are in the correct tilt position. i.e. a failure in the gear lever lock system.
So basically it's a maintenance procedure to use lock override as a way to function test those items that are used during gear up selection.
Hope that helps Rgds SMOC.
