REFLECTOR: Hydraulic system pressure

[Don Johnston]

I think that's why having the gas strut in good condition is important.

If you've got hydraulic pressure or a good gas strut, you're in good
shape.  Lose both, and it could get... interesting.


On Fri, Sep 6, 2013 at 12:03 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
>
>
>     -------Original Message-------
> From: Scott Baker <scottb33333 at gmail.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Subject: Re: REFLECTOR: Hydraulic system pressure
> Sent: Sep 05 '13 3:56pm
>
> On 9/5/2013 4:25 PM, John Dibble wrote:
> > On 9/5/2013 3:08 PM, Scott Baker wrote:
> >> Hello John,
> >> The recommended gear DOWN hydraulic pressure of 550psi is already
> >> significantly lower than the recommended gear UP pressure (something
> >> in the neighborhood of 1150psi).
> >> While true, the main landing gear does not benefit from hydraulic
> >> pressure when in the gear DOWN and LOCKED position - the nose gear
> >> linkage is aided by hydraulic pressure to keep it in the over-center
> >> (Down/Locked) position.
> >> Somewhere in the Reflector archives is a video focusing on the nose
> >> gear mono shock a! t the moment of landing.  When the nose wheel
> >> touches the runway, the top of the nose strut wants to move rearward
> >> - and in fact, it does move a small distance, which is counteracted
> >> by the mono-shock.  Without the benefit of hydraulic pressure to help
> >> keep the nose gear linkage in the over-center position, the nose gear
> >> could easily collapse at the nose wheel touches down.
> > I respectfully disagree.  With the linkage in over center position,
> > rearward strut motion will try to push the linkage even more over
> > center, but the cylinder won't allow that because it's extended as far
> > as it can go.
> >
> > John
> >
>
> Theory and reality sometimes do not match.
> When considering "What gear-down hydraulic pressure is the best?" ...
> Since the hydraulic system is already in place - and since the factory **recommended
> 550psi is a really low pressure for hydraulic systems that
> does not cause undue stress on hydraulic seals (and is proven to work) -
> why not err on the side of what works?
> Fixing an abraded nose section following a nose gear collapse is a major
> inconvenience.  Why invite trouble?
> Best,
> Scott B.
>
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