The idea of having this thread going is great, but quite frankly, it's not very useful as long as all types are mixed like this. PPRuNe should really consider having a separate forum area (perhaps inside of techlog) with separate threads for each aircraft mentioned. That way, type specific discussions would be kept cleaner and easier to browse through.
vd8, re 737 Classic Hyd fluid transfer. A very common occurrence on the 73.In theory fluid transfer should be impossible,but a couple of leaking vlvs cause the problem. Speak to your local engs,there are two methods used on the ground to re-establish levels. If you can't get an answer,PM me & I'll dig the full info out.
Some more details? Is this peculiar to the BE20 or does it affect the 90 / 1900 for example, is there something special about the system or could it potentially affect any pressurised/non pressurised aircraft? How does the error appear through the range, and is it only one ASI affected? I'm curious, sounds like a good one to try in the sim.
Rudder limiter warning coming on intermittently during cruise.
All functional tests proved serviceable several times by numerous engineers on ground. Fault was a defective Tail Cone valve not opening properly, causing ice/moisture ingress in the tail section, subsiquently affecting actuators and position pots for the rudder limiter...
Blue and Green or Blue and Yellow HYD fault light flashing on OVHD with no associated ECAM. Cause: Associated engine oil pressure switch fault. That's right OIL pressure switch.
Airbag uses signal from engine oil px to tell other systems when the engine is running.... So perhaps, no signal from switch meant the ptu was armed, but not running since the edp was doing just fine... hence fault light but no action required?
Regarding PB switches not turning on/off with too brief a push: A lot of electronic circuits now incorporate "de-bounce" logic into their switching. A mechanical electric switch can obviously only be on or off, but sometimes as it is operated, the contacts can bounce, causing several on/offs to occur within microseconds of each other. This is not a problem with say a simple light or a fan, but now that many systems are computer interfaced, a rapid sequence of on/offs can totally confuse a system. Therefore, many switches use de-bounce logic which ignore rapid changes and only register longer term changes.
This is not such a problem with toggle switches, but can be with Airbus pushbutton types. My Airbus training reinforced this by telling me to make (relatively) slow , positive selections on the pushbuttons, and wait to see the integral caption light go on before releasing pressure on the switch.
Even so, I have recently had a yellow pump refuse to switch off via the push button until I tried slowly several times - think this was a fault though.
vd8 During flight and especially landing hydraulic fluid transfer from B to A. It became 100 A and 85 B. No leak found
I thought that was normal on 73 classic? Qty changes when gear position changes on A system.
On 73Ng a particular pseu fault can cause the gear transfer unit to operate and send B system fluid/pressure to drive the gear and "over flow" A sys to the point of it dumping the excess overboard. In the case I saw the PSEU had incorrectly sensed an eng failure.
In response to VD8 his question, altough a bit late (only just read it now), maybe this is what you are looking for:
When accepting the aircraft and finding the hydraulic quantity indication over maximum (106% on the NG) in e.g. System A:
To transfer from system A to B: ELEC A pump ON ParkBrake SET ELEC A pump OFF (pressure drop) ELEC B pump ON ParkBrake RELEASE ELEC B pump OFF (pressure drop)
repeat as needed (usually 3-4 times suffice)
Although this was an overfull SYS B, an overfilled hydraulic system has at least once led to an evacuation after vacating the runway, putting the flaps to up, causing hydraulic vapor to enter the cabin (check valve failure). Bad press and very sick customers.
As correctly pointed out, quantity indications vary with configuration and with diff temperatures, and fluid does seem to travel from system to system.
Several years ago starting at SSH, right started normally and during the left engine start, the right just wound down. Both the EEC and ELC had failed. Trying to make any sense of the EICAS was not easy! Something to do with the small dedicated gen on the engine used just for the EEC, I think. No doubt someone will correct me if I'm wrong!