Citation X (C750)
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Troubleshooting; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Chart Or Publication; Manuals; Human Factors
During a July morning 2014; we started the right engine on a Cessna CE-750 aircraft. After starting the Right engine; we performed a Power Takeoff Unit (PTU) Hydraulic Transfer Check. We noticed that the 'A' Hydraulic System pressure would not show 'Green'. The Hydraulic System was cycling as it should and by deploying the speed brakes we activated the PTU. The PTU was cycling from 1;500 PSI - (2500-2700); but would never show a 'Green' indication. We thought this was odd and confirmed that the 'A' System would pressurize using the 'A' Auxiliary ( Aux) Pump; which it did. Shutting off the 'A' Aux Hydraulic Pump again let the system bleed down and the PTU took control again; but only produced 'Amber' indications. We decided to call Maintenance and he seemed a little puzzled also as to why. After Captain X and Maintenance exchanged a little troubleshooting and information sharing; Maintenance decided it should be escalated to a Technical Group. Technical concluded that the PTU was not providing enough power to the 'A' Hydraulic System of at least 2;800 PSI and that was why it was not working properly and showing 'Amber'.  We then conferenced company Maintenance back on the phone and he had different numbers from the Technical Group and said that we were fine; but could not give us a reason as to why the hydraulic indications were 'Amber'.  This whole conversion was with Captain; but as soon as we questioned why 'Amber' indications were present; the conversation went south very quickly. I have to say that the Captain did a good job of standing his ground. Maintenance started yelling and honestly acting in a way I have never heard before. The lack of answers and conflict of limitations from two sources was very disconcerting. I am not a rocket scientist; I know that. However; if the PTU function is supposed to charge the system to a 'Green' indication; then it should. Airline Transport Pilot. Contracted Maintenance. Repositioning flight. Flight cancelled.
Approximately late morning July 2014; Captain X called Maintenance Control with a concern about his Hydraulic System 'A' readings with just the Right engine running on a CE-750 in ZZZ.  The Hydraulic Power Transfer Unit (PTU) was using System 'B' pressure to power the 'A' system to 2;700 PSI; but the digits [hydraulic pressure readings] were 'Amber'. I researched PTU operations in the Cessna CE-750 Maintenance Manual (M/M); the PTU should produce 'A' System pressure at 2;600 PSI +/-400 psi; M/M 29-20-04; PTU Maintenance practices; Paragraph 4; Item 11.  The crew's concern was about the numbers being in 'Amber'; to which I said they should be until 2;800 PSI; at which point they should be 'Green'.  To get more information on the issue we contacted Technical Group Representative X  who reiterated what Captain X and I had spoken about; the pressure indication should be 'Amber' until above 2;800 PSI. Captain X and I had also discussed the pressure of the 'A' System and agreed the PTU was making the correct pressure per the M/M and the AFM; which he had looked up and I did as well.  In the AFM; under the 'Normal' tab; Page XXX-10; Starting Engines; Paragraph 5; Item 'b'; the PTU should produce Hydraulic System 'A' pressure '1;500 to 2;700' PSI. Technical Group Representative X pointed us to the 'Operating Limitations' tab in the AFM; 'EICAS and Instrument Markings' where it states: 'Hydraulic System A and B Pressure; Digital Indication; Green Range; 2800 to 3;200 PSI; Amber Range <2;800; >3;200 PSI.'   Captain X stated he always remembered the numbers being 'Green' all the time.  I told him obviously the Manufacturer of the aircraft and what they put in their AFM and M/M must be wrong; write it up and send it in.  The Crew sent in the following: 'Hydraulic 'A' side pressure during the PTU Check is Amber and remains Amber during PTU cycling and bleed down. Pressure cycles between 2;700 PSI and 1;500 PSI but remains Amber the entire time.' By sending in this squawk; I believe the Crew is falsifying company documentation and forcing me to be a part of it by having to enter the squawk into the Maintenance Information System.  Per the Crew squawk above; the PTU was producing 'between 2;700 PSI and 1;500 PSI.' (as stated above: In the AFM under the 'Normal' tab for 'Starting Engines'; Paragraph 5; Item 'b'; the PTU should produce Hydraulic System 'A' pressure '1;500 to 2;700 PSI.')   Again; in the Crew's words 'but remains Amber the entire time.' As stated above: 'Operating Limitations' tab in the AFM; 'EICAS and Instrument Markings; where it states: 'Hydraulic System A and B Pressure; Digital Indication; Green Range; 2;800 to 3;200 PSI; Amber Range [less than] <2;800; [or greater than] >3;200 PSI.'.  What this crew is writing up as a discrepancy is addressed in their AFM as 'Normal' operations and indications.  This was conveyed to them by Maintenance Control and Cessna Technical Group.  I believe this [flight] crew needs more recurrent training about the operations of the aircraft and to learn not to rely on their memories; but to rely on their AFM; FOM; etc.; for information.
A pilot and a Maintenance Controller describe different perspectives on whether or not a Power Transfer Unit (PTU) on a Cessna CE-750 aircraft was providing enough hydraulic power. Hydraulic pressure from PTU would not move beyond the 'Amber' indication range.