REFLECTOR: Hydraulic system pressure

[Scott Baker]

On 9/6/2013 1:03 PM, jerry at jlbent.com wrote:
> I guess this raises a question about the dump valve and gear down 
> saftey. If the nose gear needs the pressure to maintain the lock, then 
> we should be aware of an increased probability of nose gear collapse 
> when using the dump valve.
> Jerry Brainard
> Jerry at JLBEnt.com
>
Absolutely! And especially with a tired NG overcenter gas spring. The 
fear of a nose gear collapse following an emergency landing gear 
extension using the dump valve is the main reason for installing a NG 
Safety Stick.

7.9.2 - Nose Gear Safety Stick
The velocity nose gear uses a gas spring to hold the nose gear 
overcenter against the
overcenter stop. There is a possibility that after years of use the gas 
spring can loose
it’s pressure and not work properly. Since there is that possibility 
that your gas spring
may not have enough force to push your gear into the overcenter position 
there is a
way to check to make sure the nose gear is in the overcenter position 
before landing
in an emergency situation.
You will need to get an 8 inch long 1 inch diameter wood dowel. Using a 
1-1/8”
diameter hole saw you will drill two holes in the keel that are 
positioned just under
the pivot point of the overcenter linkage and shock as shown in figure 7-57.
Figure 7-57 Nose Gear Safety Stick Hole
In the event that you need to do an emergency extension. After the gear 
is fully extended
close the dump valve then insert the safety stick about half way in the 
hole in
the keel on the pilots side. Push the stick down and pivot it on the 
keel so the other
end of the stick will push up on the pivot point between the shock and 
the overcenter
linkage. What you are doing is verifying that the linkage is up against 
the overcenter
stop. The stick is long enough that you can then insert it in to the 
keel and partially out
the copilots side and leave it their during your landing. This is just a 
little extra
insurance to make sure the gear stays overcenter during your landing.

Scott B.