To pressurize or not?
 

I am in a bit of a quandary , regarding the exterior inspection of a B737-700, that I wanted to ask.

The fact is, that the exterior inspection procedure tells you to verify any fluid leaks during the walk around, but doesn’t specifically say to pressurize the hydraulic systems as we were used on the 737-200.
The question is: do we have to pressurize hydraulics or it is not necessary?
I personally think that in order to check for any fluid leakage, you should pressurize it.
I am not aware of any airplane manufacturer documentation that explains the change in philosophy regarding preflight configuration.

But I would like to know what does Boeing say about it, if anyone knows, and of course your personal view of the subject.

Happy Trails!!

Well it makes sense to me that a leak would be for more easy to see in a pressurized system.

......and not just the hydraulic system.

I have on 2 occasions detected fuel leaks during a pre-flight inspection, as a result of the fuel pumps being pressurized (it was policy at a previous carrier I flew for).

Well, if it doesnt say to pressurise the hydraulics...



Sounds like a maintenance action to me.



When we acquired a smaller Airline a few years ago some of their crews continued to follow their preflight procedure which involved turning ON all exterior lights including anti-collision and strobe lights at the gate while conducting their walk around checks.


This was most distracting until someone said what are you doing ?

This is a maintenance function, not for a pilot walk-around inspection. We don't pressurize hydraulics until all doors are closed, gear pins removed, and cleared by ground personnel via intercom, prior to push back. . . . What's next? Would you as a pilot also be walking around with a tire gauge and checking tire pressures? :ooh:

Call me old-fashioned, but I'd rather discover a hydraulic failure or fuel leak on the ground than in the air. :)

Unless the leak just happens to start as you begin your walk-around there will be signs of it already without any pumps on.

There is nothing to prevent you from pressurising the hydraulic systems for the walka round as long as you return them to the state prescribed by your company for start up. The hydraulic quantity gauges should give you any indication of loss of hydraulic fluid that you need to know as well if not better than a pressurised system during the walk around. As long as the gear bay is kept clean enough you should be able to notice where a leak has occurred by dirt sticking to the leaked fluid.

My advice is that you stick to the guidance or SOP that your company uses, but that you raise the question with your tech manager or chief pilot.

When you conduct the walk around, you are looking for leaks - not necessarily for something leaking. :) Look for fresh, wet, fluid sprayed in the hydraulic bay.

I'm not shure if you want to be around a 3000 PSI hydraulic line with a hole in it :8

Quote:

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I am in a bit of a quandary , regarding the exterior inspection of a B737-700, that I wanted to ask.

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When doing an "external inspection" you are looking for evidence of the leak, not the leak its self. You cound have a leak in the aileron servo the the evidence, puddle of fluid may be many feet away. Fluid runs down hill and the leak in the aileron servo may show up as a puddle under the wheel well.

Even if you pressurized the hydraulic systems it may not help in finding the leak, just make more evidence.

other than the first flight, wouldn't the system be pressurised till shut down, allowing the leak to be detected in the walk around

Hydraulic leaks leave residue behind. They are easy to identify. Fuel leaks in many cases, are not.

Hydraulic leaks or residue is generally easy to identify regarding fresh, vs. a previous leak. The system need not be pressurized to identify such a leak. Only if there's a question should one clean the area, re-pressurize, and verify the leakage.

Follow your directives.

Thank you all guys for your inputs.

Happy trails!!