Nitrogen "Blow Down" Gear

[BradG]

Ok, i understand that some Twin Cessna's, including the Citation have a nitrogen bottle to blow down the gear. I have never flown any of these aircraft, so maybe someone can enlighten me. What kind of gear system to these aircraft have (Hydraulic, Electic-mechanical, etc)? And why is a large pressure needed to get it to come down? No crank, pump, or dump valve? Im gettin ready for my CFI ride, and was studying gear systems, and i remembered the nitro. bottle thing, and cant find a darn thing about it in any of the books i have. Thanks

 

[Timebuilder]

The Lear has a bottle of air for the same purpose in a emergency.

The Citation is very likely to be similar: normal use is hydraulic, controlled by electric, and a gas or air bottle for emergency use when the hydraulic system fails.

The description you are looking for will only be found in the AFM for the aircraft, or the associated type rating training manual.

At this point, this info is an interesting diversion for you. I'd continue to study the aircraft systems you will be asked about during your upcoming checkride.

 

[Buschpilot]

Some airplanes use the blow down bottle to help "aid" the hydraulic pump push the gear down, which is tough to due cuz of the airflow. My plane (turbo commander) also has to push the gear 'over center' to lock it. This is also aided by nitrogen.

Think about this: If the nitrogen is pushed back into the bottle on the up cycle, what happens if the bottle is overcharged to begin with?

 

[Timebuilder]

We may be talking about two different concepts here: the use of a nitrogen charged accumulator to help actuate the gear in normal use, and the "blow down" of the gear in an emergency situation.

Anyone have an additional insight?

 

[Bill Mostellar]

the "blow down" of the gear in an emergency situation.

In these situations, the system will also [typically] reposition the "landing gear control valves" to the "down" position, thus allowing any hydraulic pressure that might be holding the gear "up" to return to the reservoir.

I wish you success!

 

[Joe Jet Pilot]

Not A Cessna

Not all nitrogen bottles are used for "blow down" of the gear. In the case of the Beechjet the only thing that the nitrogen bottle is used for is to blow the gear doors up and the emergency brake.