Hydraulics B757
Good morning everybody.Having a look to the HYD system on the 75,I got sevral questions that I am sure somebody will know the answers to(at least to some of them)
I got 13 questions,I know it can be boring,but at least I hope to get some answers from the knowledge community and hopefully it ll be usefull for somebody else since discussions always make us think a little more.
Here they are.Thank you in advance:
1-It says that when Left engine and electrical Hydraulic punps fail,the Status page shows the PTU output.
---Does the Status page also shows the PTU output if only the L engine Hyd pump fail?
2-QRH says that if Lest System fails,PTU may be unavailable because of a Leak.
---What about then about the reserve fluid in the reservoir for the PTU?Can we also loose that?
3-Any idea of the reason why "USE DIFFERENTIAL BRAKING" is mentioned on the L hyd syst failure but not on the R Hyd syst failure?I thought they recommended differential braking because you loose that side s Reverser.But that s the same for both sides..
4-Why,in case of 2 simultaneous Hyd systems failure they put a Maximum Crosswind?is that because only one of the 3 actuators per control surface is available?
5-If Autobrake becomes INOP with a R Hyd system failure,why Autobrake does NOT become INOP when R and Center systems fail?
6-Theory says that Normal and Reserve Brakes (powered by R system)have total Antiskid capacity,but that Alternate Brakes(L system) have only laterally paired capability regarding antiskid.Then shouldn t all the QRH having a R syst failure(R,R and C or R and L) mention the reduced antiskid capability on the landing performances?
7-electrically speaking,where do the elec Hyd Pumps(the Left,Right and the 2 center ones) take the Energy from?what Bus?is that SBY?
8-any idea of the output(PSI) of the engine and the elec Hyd pumps?In normal operation they re all operating so I don t know if when the Engine starts running the eng pump overrides the electrical(more output) or if both work together
9-Pulling the fire switch not only cuts the HYD fluid to the pump but also the cooling fluid that still goes though when we select the pump off.So the question is:is Maintenance actio required after we pull the fire switch?what happens then if we push the handle back in?
10-Why we loose all Autopilots with (R,C) Hyd failure?why L A/P won t work?I thought every system powers its Servo
11-what is the real difference between reserve Brakes and accumulator Pressure?
12-The Diagram shows all the 3 systems linked to spoilers.How s that?L system to left spoilers panels,R to Right, and Center what?
13-Where are the Hyd fluid reservoirs located on the Airplane?How many Gallons or liters of fluid?
I told you it could be boring.
But thanks