A319 flight crew reported hydraulic pressure issue during pushback that resulted in sheared tow bar pin due to non-compliance with MEL.
Synopsis
A319 flight crew reported hydraulic pressure issue during pushback that resulted in sheared tow bar pin due to non-compliance with MEL.
Narrative
While this report is for our failure to comply with an MEL; which caused a tow bar pin to shear; it is also be bring awareness to operating with excessive MEL's on an aircraft. Aircraft X had 8 logbook deferral items and 6 MEL's.Maintenance was called for an incorrect MEL control number on the placard and a different missing placard. During our departure brief; per current MEL's we briefed turning off A/SKID & N/W STRNG; along with the need to express that the PARK brake was off to the push crew along with visual closed and locked of the 1L door to comply with all the MEL's on the aircraft. Several mechanics came out and one of them stated that MEL XX-XX was removed. I stated oh good; we don't need to do the A/SKID & N/WW STRG off". He said "you are good to go". When in reality MELXX-XXA was removed but XX-XXB remained and to comply with the MEL; hydraulic pressure to the nose wheel steering needed to be shut off. We did not; and upon starting the engine; the rising hydraulic pressure sheared the tow bar shear pin.After tracking the logbook; Aircraft X had no damage noted for the incident.After being towed back to the gate and now an incident was weighing on the FO and myself; we were given a new plane.Aircraft Y had 9 logbook deferral items and 4 MEL's. Maintenance was called on MEL XX-XY and XX-XZ to get clarification on verifying Auto Brake indications. The ECAM Wheel page had no indications of the operation of Auto Brake. A total of 5 mechanics came out and all were unsure of the indication or lack of it. This caused about a 2-hour delay. One mechanic went to another aircraft and researched and came back with the fix. The MEL does not state that hydraulic pressure must be on system for Auto Brake to show indication and operation. All of us said this is a poorly written MEL; and the need for hydraulic pressure should be on that MEL.The issues this evening stemmed from broken aircraft with an excessive amount of MEL's and multiple MEL's on the same system; 3-hour delays rolling into the night; 1 hour between flight from delay; and in the end approaching the expiration of our duty time past midnight.Things that could have prevented this incident: Attention to detail on complex MEL compliance in compressed time due to delays. When in doubt; delay engine start until push back and disconnect is complete. Very cautionary use of aircraft with excessive MEL's with numerous MEL's on the same system. Due diligence when operating and approaching duty time limit late into the night."
Second reporter narrative
We arrived at gate XX from delayed flight from ZZZ1 and had roughly an hour between upcoming scheduled flight. I walked from [gate] XX to XY which took roughly 18 minutes. Arrived at aircraft and while captain started checking out MEL procedures (We had six on the aircraft) I went out and did the walk around. I returned after walk around and loaded flight plan and prepped the aircraft. Captain was writing notes in multiple procedures would have to complete with up coming MELs. We then worked through normal briefing items and route verification and briefed MEL procedures; including turning off antiskid due to Nose Wheel Steering MEL. While captain briefing I verified that placard numbers were correct; and found that they were not correct. Called maintenance to the aircraft and on their arrival addressed correcting the placards; during this process one of the MEL's that had been removed was one of the two MEL's for nose wheel steering issues. The captain asked the maintenance crew then if we would not have to do the procedure. He replied no that has been fixed. Shortly thereafter we began push back; we confirmed that light ground crew normal sees with nose gear was still not working for brakes. Push back then occurred normally with confirmation of brakes. Engine start was called for and shortly after starting engine one loud noise and pushback was immediately stopped. We called maintenance and let them know had issue that needed inspection. We shut down engine after talking to ramp to see if could stay where at due to not knowing if could be moved. Maintenance arrived and began inspection. Tow bar and nose gear initially inspected and multiple times said seeing no issues. But then found a hydraulic leak and determined safe to pull back to gate. Coordinated with Operations to allow them to determine next steps operationally.Cause: Aircraft with multiple MEL items and on same system. Confusion due to incorrect placarding initially and statement that something was fixed in same system and then asking if procedure not required with reply no that has been fixed. Crew not verifying that MEL with procedure that previously discussed was the one that actually got fixed.Recommend that engine start be delayed until after towbar disconnected from aircraft or possibly procedure where nose wheel/antiskid switch is always shut off until ready to taxi.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.