This is what I read in a website (
http://wisdomseva.com/ghyds.html) created by an Indian Airlines Captain:
DESIGN DEFICIENCY IN A320 ‘ GREEN ’ HYDRAULIC SYSTEM
Some time back, I used to notice the Green Hydraulic System indication of the A320 showing decrement during flight at higher altitudes with time, comparing to the Yellow & Blue system. My wonde for the reason compelled me to accomplish in-depth study of the entire Hydraulic system of the A320 a/c as something inside me, within, was inspiring me to do so, telling me that there is something wrong. I made several workshop / hangar visits, studied the system layout, circuit diagrams and various Maintenance Manuals involving lot of tedious effort & time.
Ultimately, the truth revealed by itself. I found, ( unlike the other two systems ), the Green Hydraulic System Reservoir and its associated circuit so located by design that when it gets subjected to cold- soak, the hydraulic fluid contracts to such an extent that would trigger a SYS LO LVL thereby causing lot of problems for the ignorant pilot. I took up the matter with the DGCA/IAL authorities but my theory was rejected & all efforts were in vain.
My belief was firm, something within me inspired me to go ahead & stop not till the goal is reached. I approached the Airbus Industrie with the problem alongwith all the papers, drawings & my hard-work. The AB carried out detailed investigations / flight tests. This is what was their finding :
Quote : “ After several reviews with different Airbus resources involved in definition and design of the A320 hydraulic and landing gear system we came to the following conclusion :
It has been confirmed that assuming the very specific case of a flight proceeded with abnormal L/G door Config ( Partially or fully open ) in high altitude, it leads to an cold soak effect on the green Hydraulic system that may be followed by the triggering of the ECAM LO LVL warning. Applying the ECAM procedure will lead to a loss of the green hydraulic system.
The loss of the green hydraulic system is considered as major, whereby the a/c is flying in normal law and apart from landing gear gravity extension and multiplying the landing distance per 1.1, no specific crew action is required. When during decent when the cold soak effect disappears, the fluid quantity indication on the system page may return back to normal and when monitored by the flight crew, the lost system could be recovered.”
Unquote : I also gave them the modification proposals in regard to the design in their circuit to overcome this problem which they also accepted. But stated that the expenditure involved was not feasible / due low probability etc.and to let things continue as it is. They also regretted the delay in reply as a number of Airbus departments were involved in the investigation.
What the Airbus gave me in return for my hard work :
‘ THANK YOU FOR YOUR INPUTS ’, Yes, just these five words.
Any takes on this one?