lml@lancaironline.net Mailing List Archive

Wolfgang,

I think you missed the point of my last post. I was describing the benefits of having momentary switches Angier suggested to jumper across the pressure switches. The three examples cited are not in any way related to hydraulic lock-up nor are they addressed by your module. Designing another circuit to detect, identify and properly respond to component failures is a tad complex. The pressure switch failure I described is a perfect example. In those situations, having more information along with more options available to the pilot is a good thing?

Regarding the pumps Lancair currently sells, both Oildyne and Lancair have already acknowledged that the pump currently sold can lock up when used in a stock 320/360. The reason for not offering the proper pump configuration for the 320/360 is purely financial - very low volume. Lancair did suggest that they could include a warning regarding the lock up potential each time they ship a pump as a replacement for a 320/360. This leaves the aircraft owner in an awkward position. The ironic thing is that a properly configured pump can be obtained directly from a Parker distributor for much less.

My concern with misconfigured pumps trickling out into the fleet is that it will eventually catch pilots unaware of the technical issues off-guard.

Chris Zavatson

N91CZ

360std

www.N91CZ.net

From: Wolfgang <Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Wednesday, February 22, 2012 9:36 AM
Subject: [LML] Re: 320/360 Hydraulic Pressure Switch

We can keep this up for the next year but I believe talking it to death will not fix the problem. My preference is to have a system that takes care of itself. You seem to want to be "involved" in the anomalies of flight. If most people wanted to be "involved", we wouldn't have things like FADEC's and auto pilots. The module I provide can help keep flight a bit more self sufficient and safer. If you could convince Oildyne and Lancair that they have a problem with the pumps as used in Lancairs, and fix the problem, then more power to you and the Lancair owners. But in the mean time. I still like my gear module.

Wolfgang

----- Original Message -----

From: Chris Zavatson

To: lml@lancaironline.net

Sent: Tuesday, February 21, 2012 9:01 AM

Subject: Re: [LML] Re: 320/360 Hydraulic Pressure Switch

" . . . you can only override one pressure switch at a time or overload the system.
You need one switch each for the up and down. In the event of a problem you have to make sure you push the right switch"...

Overload what exactly? The gear selector determines which pressure switch is powered. If you jumper across an unpowered switch, nothing happens.

While I do not advocate putting in switches to mask a pump problem that should really be investigated and fixed at the source, momentary switches have other benefits.

1. Checking the relief valve settings in the pump. By holding down the switch, one can see the relief valve setting of the pump.

2.  Back-up for a failed pressure switch. This was more common with the VEP switches, but current version is not immune.

3. Recharging the system on demand - The hysteresis loop on the pressure switches is quite large. The gear can start to sag before the pressure switch recharges the system. This is more of an issue for the Outback Gear due to the higher aerodynamic loads pulling on the gear.

With automation and complexity come new failure modes.  Give the pilot enough information about the state of the aircraft systems to figure out what happened and enough controls to solve the problem.

Last summer when the high pressure switch went out, the pump shut off before the gear was all the way up. Higher than normal air noise was the first clue. A quick look at the pressure gauges revealed the high side at only 800 psi. The momentary switch pulled the gear the rest of the way up.   Examination of the pressure switch uncovered intermittent electrical contact within the switch when pressurized.

Chris Zavatson

N91CZ

360std

www.N91CZ.net

From: Wolfgang <Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Monday, February 20, 2012 4:58 AM
Subject: [LML] Re: 320/360 Hydraulic Pressure Switch
Yes, that would be easy . . . except . . . you can only override one pressure switch at a time or overload the system.You need one switch each for the up and down. In the event of a problem you have to make sure you push the right switch.If you come up with some more complicated wiring, you could make it work with only one switch for both up and down but you still have to push the button if something isn't working as required.. . . or . . . you could put in a completely automatic system . . .Wolfgang----- Original Message ----- From: "Greenbacks, UnLtd." <N4ZQ@VERIZON.NET>To: <lml@lancaironline.net>Sent: Friday, February 17, 2012 1:07 PMSubject: Re:320/360 Hydraulic Pressure SwitchSeems to me the simplest and least expensive option would be to install a momentary on switch in the cockpit to override and close the open pressure switches.Just my 2 cents.Angier AmesN3ZQ --For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html

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