How would one get hold of a 737 rudder servo valve

[Barkmi4]

I apologise if this has been brought up before, but I'm yet to find any information upon it.

As part of a uni project I'm investigating the defective 737 rudder servo from the original and classic 737s. Research says over 2,700 were replaced by November 2002, and I'm trying to get my hands on one.

I've contacted a number of companies but am yet to have any joy in locating any. Does anyone have any idea how to find one? They are a relatively small part, I imagine if anyone were to keep a part they've stripped this would be it because of its conviniet size.

I hope someone can help, Thanks in advance.

[vapilot2004]

While I don't know of a current source of such a servo valve, the troublesome units were built by Parker-Hannifin.

An historic note that is not widely discussed: it was upon P-H testing data that Boeing based their initial findings where it was thought the rudder hard overs were not caused by the aircraft or its systems.

[Barkmi4]

Appreciate the response, not sure what you mean by Boeings initial findings.

I know it took them years, through several different investigations until they found the unit could jam or reverse. Off the top of my head I can't remember which incident it was, but I know if the primary slide jamed and the valve was subjected to thermal shock the secondary slide could jam or reverse. Is this the point you're referring to or have I missed something?

I've tried to get hold of a valve from Parker, refered me to one of their offices in Michegan but no response.

Cheers for the response

[vapilot2004]

I can see why it might be hard to put hands on an original (and defective) PH PCU - 1.) they've all been replaced years ago, 2.) generally, defective FRU's are eventually binned or locked away (thanks legal department) but not after the factory has had a chance to examine them and the component parts for failure modes - allowing for an extraction of the weak link in the design or manufacturing process. Possibly the NTSB would have a couple of the accident/incident units still lying around.

We operated the classic for a few years before I came along. I'll see what our guys know about the PCU's disposition specific to our outfit.

Appreciate the response, not sure what you mean by Boeings initial findings.

I know it took them years, through several different investigations until they found the unit could jam or reverse. Off the top of my head I can't remember which incident it was, but I know if the primary slide jamed and the valve was subjected to thermal shock the secondary slide could jam or reverse. Is this the point you're referring to or have I missed something?

Precisely - you've nailed it in your 2nd paragraph, Barks!

[vapilot2004]

Not sure if you have this information, but wanted to share Barks.

Our earlier birds, 733, 734, fitted with Parker Hannifin PCU's, were upgraded in the mid-1990's. Nothing more specific yet as to the disposition of our pulled PCU's, however I do have a part number that may assist you in your search. The original Boeing part number for the defective PCU was 65-44861. Later iterations of similar units carried sub-part designations, ie:-01, -02, etc.

You should be able to find some spares out there that, while rebuilt with a new valve assembly and limiter would have the basic design of the original intact.

Additional information from the coverall gang:I've been told de-certified units (of all types) have been known to survive and end up in inventories carried by the third world. Perhaps a look at African, South American, and Near-Eastern sources would be a worthwhile endeavor. Finally, a classic bird that was put to desert sleep prior to 1995 (when PCU replacement was first begun per AD) could be another source. Happy hunting!

[N707ZS]

Possibly try investigating companies at Bournemouth airport it was the last resting place for a number of 200s. Don't know if European operates in any form down there.

[Barkmi4]

Cheers guys, still looking but had no joys yet. I'll look into Bournemouth and see what it brings up. Harder still because most UK airlines that flew the old 732,733s don't exist anymore.
If you do stumble across anything be sure to let me know.

Thanks again

[Newforest2]

Aircraft salvage, recovery and disposal services - Air Salvage International (http://www.airsalvage.co.uk/)

If I was starting at square one, these are the people I would call, if they don't know, it is not available in Europe!

[Barkmi4]

Cheers, I did actually get in contact with them, the MD Contacted me a few times, but unfortunately they didn't have any available