B777 flight crew reported they released their brakes while parked at the gate due to a hot brakes EICAS and the aircraft rolled several inches while a Maintenance Technician was servicing the landing gear.
Synopsis
B777 flight crew reported they released their brakes while parked at the gate due to a hot brakes EICAS and the aircraft rolled several inches while a Maintenance Technician was servicing the landing gear.
Narrative
We arrived at the gate in ZZZ and not long after setting the parking brake and completing the parking checklist; got a Brakes Hot EICAS message with accompanying Electronic Checklist (ECL). My FO (First Officer) accomplished the checklist as a read and do. When he came to the item that called for the parking brake to be released; I looked out through the front windscreen to see if the Marshaller was still in position and had yet given the chocks inserted signal but he was already gone. I then instructed my FO to call Operations to see if they could determine if our chocks were in place to which they said yes. I then released the parking brake per the ECL and immediately noticed the aircraft moving slowly backwards. It appeared to move approximately 6 inches then stopped as it appeared to rest on the aft chock. We completed the Brakes Hot ECL.Shortly afterwards; a Maintenance Technician came in the cockpit visibly very aggravated asking us who said it was OK to release the parking brake? He went on to say the he was checking tire pressures when the aircraft started moving. Being on the B777 for a year now; it was then that I remembered the SOP from my previous fleet requiring one of us to go down and visually verify that all wheels were chocked before releasing the parking brake assuming that it applied to the B777 fleet as well. I was then very annoyed at myself for this error and very apologetic to our Maintenance Technician. It didn't seem to help much and I didn't blame him for being very annoyed. I could have severely injured or even killed him or someone else working near our wheels. Afterwards; my FO took the opportunity to look up the SOP which I referred to. He couldn't find it anywhere in a search of our FM or FOM. I eventually also searched for it or any guidance on releasing the parking brake at the gate due to hot brakes. To my surprise; I found nothing. One reference in the FOM says:'PARKING BRAKE - As soon as the aircraft comes to a stop at the final parking spot; set the parking brake. Never release the parking brake without direct contact with the marshaller (e.g.; chocks-in hand signal or verbal notification). If hot brakes are suspected; see FM for hot brakes procedures.'In referencing the B777 FM for hot brakes procedures; the only reference is with regard to a rejected take off. We could find no reference at all for hot brakes at the gate after taxi in. I make no excuses for the fact that my actions caused my aircraft to move without ground personnel in close proximity to it being made aware but in evaluating why it happened; it would appear that we actually have no specific guidance except for a hand signal or verbal notification that the chocks are in which we did receive from the Operations agent. In light of the fact that our Maintenance Technician and others could have been injured or worse though; that procedure is clearly insufficient. To my knowledge; the Operations Agent only verified through the cameras that chocks were in; as we asked her to do; and not that aircraft was sufficiently clear of personnel and equipment in order to safely release the parking brake. Even the SOP from my previous fleet only required that we verify visually that the chocks were in place but not to verify that the area was sufficiently clear or to notify any personnel working in close proximity to the aircraft that it may move a few inches; also insufficient. Without specific and effective guidance on releasing the parking brake after gate arrival for any reason; we disservice our crews and ground personnel and put them harms way. That applies to all fleets and would have been helpful to us in this situation. We had a thorough debrief and I'm confident that we won't make that error again.
Second reporter narrative
I was PF (Pilot Flying) for a normal 30 flap landing on XXR in ZZZ. The approach was flown with flaps 30 and auto brakes 3 selected. The aircraft was slowed with idle reverse and the auto brakes remained engaged until below 80 kts. The aircraft was taxied off [Taxiway] ZXX to XX; ZZ; and Gate ZXX. As we approached our parking spot we got a BRAKE TEMP EICAS message. The Captain was focused outside on the automated parking system. I didn't want to distract him at that time; and I didn't think we could have a brake temp problem after a normal landing and short taxi in. We blocked in; and I ran the parking flow. At that time; I let the Captain know we had a BRAKE TEMP EICAS and non normal checklist. We ran the parking check and completed the BRAKE TEMP non-normal. I displayed the Gear schematic on the Captains MFD. The aft right inboard brake temp was an amber 5.2. All other brake temps were green.I read through the non-normal including the bullets associated with step 4 which states to observe brake cooling restrictions. Bullet three; step 4 states to 'Coordinate with Maintenance and consider releasing parking brake to aid cooling. Ensure chocks are in place.' As I read it; I thought the intent was to coordinate with Maintenance for the hot brakes issue and coordinate with the Ground Crew or Operations to release the parking brake. The Brake Temp Cooling Chart states for temps from 5.0 to 9.9-clear runway. Do not set parking brake. We discussed the need to release the parking brake and the fact that the Ground Marshallers were no longer in view. The Captain asked me to call Operations to confirm that the chocks were in place. Operations initially did not understand and responded with the block-in time when the system updated. I called a second time to clarify I needed to know if the wheel chocks were in place. The second response confirmed the wheels were chocked and the parking brake was then released. Shortly after brakes were released; I noticed the brake temp dropped to 5.1. I considered that the brakes had reached their max heating and would continue to cool back into the normal range. At that time; a Maintenance Technician came to the flight deck and asked why the brakes were released. He notified us that he had been checking the gear at the time of brake release and he was visibly and understandably upset because the aircraft moved slightly as it settled in the chocks. The Maintenance Technician was made aware of the gear schematic. The Maintenance Technician did not seem concerned with the amber brake temp indication; and he responded that he needed to change a center brake on that gear anyway.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.