Forum: F-16 Procedures

This picture definitely speaks a thousand words!
Source: http://www.shaw.af.mil/news/story.asp?id=123253471

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Gee...what gave it away I wonder? Wink

How many crew chiefs here had jets where you always had to bleed one hydraulic system and service the other. aka; bleed over.

curries103 wrote:

How many crew chiefs here had jets where you always had to bleed one hydraulic system and service the other. aka; bleed over.

I’m sure every crew dawg has seen it. Seems to happen more frequently when the outside ambient temp is very hot, and when B has lots of air in it. Fill B and bleed down A is the story. X-over is most likely taking place in an ISA or PDU.
Even though the book has a procedure for servicing hydraulics with the engine running, I don’t like doing it.
Remember, when you dump your reservoir accumulators, the increment should not rise by more than 5%, if you investigate and take action of that anomaly immediately (it’s in the FI) then you will prevent what is happening in the photo. That sucks.

VarkVet wrote:

I’m sure every crew dawg has seen it. Seems to happen more frequently when the outside ambient temp is very hot, and when B has lots of air in it. Fill B and bleed down A is the story. X-over is most likely taking place in an ISA or PDU.

We have a requirement on JSF to have 0 X-system leakage. I have no idea what the requirement was on F-16, but I would hope hydraulic component design has improved since then. I will be interested to see if this same type of comment will be made as crew chiefs get their hands on the JSF.

trouble shooting the crossover in the FI sucks. gets fluid everywhere! pressure on "B" remove "A" hyd lines Thumb

Crossover occurs in the airliners as well, especially Boeing 757s. We typically would power up the higher qty. hyd. system and pump the brakes (rudder pedals) alternatively until the im-balance was resolved. This could take anywhere from 30 seconds to a minute to accomplish. The F-16 is approximately the same era of aircraft design.

Quote:

trouble shooting the crossover in the FI sucks. gets fluid everywhere! pressure on "B" remove "A" hyd lines Thumb

Ever think about zip tying plastic baggies over the return nipples on the servo/actuators themselves? Makes less of a mess and you can better see where the problem is. That's what we did on Apaches when we had this problem (which did happen occasionally). Last time I checked the MSDS showed hydraulic fluid to be toxic. I never wanted to touch that stuff.

In my day on the F-16 at Hill AFB we used a hand pump. This would be the first years, you know stone age of the F-16. That is before we thought about placing a flow restrictor in the JFS starter circuit. 350 strokes of the pump, four crew chiefs and ten minutes if you did not get the JFS to lite off the first time. We got a little smarter and hooked up hydraulic mules to pump the B system accumulator up and then we let it sit for five minutes to get the air out. The fluid would always get air in it and if you did not bleed it out. Well that is a different story. The original 1976-78 models at Hill were anything but perfect. The fluid transfer problem is a constant problem on many aircraft models military and commercial. After 4 years in the Air Froce and 26 years at Boeing. Balancing the hydraulic system quanities between systems is just an everyday just do it thing. Engineers could develop a better system but the airplane might not get off the ground. So the crew chiefs and ground pounders of the world suck it up and git r done. Some airplanes require more TLC then others. Even the brand new ones!!

Forum: F-16 Procedures

Infamous B System Hydraulics