Commercial Fixed Wing
Communication Breakdown; Training / Qualification; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Aircraft Aircraft Damaged
Incorrect / Not Installed / Unavailable Part; Weather; Procedure
We continue to have aircraft either sliding or rolling on the gates [in frigid weather]. We have been told that the brakes must be released to allow for cooling.Last year after we had two rollbacks (one that resulted in major damage) within a few days. The company put a pilot bulletin out that stated all brakes must be set while the aircraft was on the gate in ZZZ until further notice. That standard stayed in place for two months and we didn't have any more occurrences of uncontrolled moving aircraft on the gates. There was a team of manager level people that convened to investigate and solve the problem immediately after these two instances. Up to that point in time we probably had [over 10] reported movements in the previous 12 months. We don't know how many movements went unreported. The investigative team concluded that the aircraft were not being properly chocked and that certain gates would require 'double chocking' to compensate for the greater slope on those gates.Since that time we've only experienced one aircraft movement that resulted in another major aircraft damage. This incident was caused by a brake release of an aircraft that was parked by the tow vehicle and the pilot released the brakes without the aircraft being chocked because the ramp was closed due to lightning in the area. Since cold weather has set in and we have ice and other contaminants on the tarmac; we have once again begun to experience uncontrolled aircraft movements while on the gates. Some of these are happening during the chocking process and some are after the aircraft is chocked.The problem of aircraft moving uncontrolled on the gate is a serious problem in and of itself; but we have evolved into a state of affairs where the uncontrolled movements are so frequent that many workers have accepted it as the norm and they are not reporting them. Out of four movements in the past week only one was reported and documented. There are two reasons that I hear when I ask why people don't want to report these movements. They are:1. They have expressed concerns in the past about these movements and the proposed solution of double chocking and making sure the chocks are used correctly is not being well received by the frontline folks doing the work. Everyone out there knows that a piece of rubber that is frozen sitting on a slick or icy surface is not going to hold a fully loaded AC from moving. The reference that is always used is 'There is a reason they freeze hockey pucks before they use them in a game; so they move on the ice better;' Rubber chocks sitting out in sub zero temperatures 24/7 are going to react the same way when you put them down on ice or slick concrete that is covered with glycol or some other slick ice melting product.2. The [ground crew] reporting procedure is too difficult to use. It takes too long to fill out the report and the availability of a computer that is capable of accessing the system is hard to find on the ramp.Regardless of how many safeguards we implement on the ramp to prevent injury or damage; we can't safeguard 100% against uncontrolled brake releases or brake releases/brake sets that are not communicated. Failure to communicate that brakes are still set can also lead to damage and/or injury. Ultimately; the flight deck has to be accountable for ensuring that brake set/release is communicated to the ground crew prior to the actual act to prevent uncontrolled movements.
An air carrier ground employee; addressed issues with uncommanded movements of aircraft while parked at gates made slippery by frozen precipitation.  He cited the practice of releasing parking brakes for cooling and the use of ineffective chocking techniques as contributory factors.