pilot's conclusion from his own past success:
"... regularly use hand signals with the ground crew, it is a tried and tested method of communication...."
First -- PLEASE add the source/date (link) to the ramp-mishap cited in the initial message(?).
The mishap report mentions this observation, cited in top slot:
"... Instead of ... headset ... agreed to work with hand-signs ... compromised the safety ..."
This is mostly about safety during
push-back, and during an unexpected stop for additional
LATE BAGS. The case for redundant safety features [first VOICE with added backup by SIGHT-signals] is mostly driven by ramp-mishap history.
Push-back or Power-Back is a period of poor SIGHT-view down proposed track. Wing-walkers don't have perfect communication with either the Pilots nor the Tug Driver. The Pilots have NO VIEW of the push-back corridor. The Tug Driver's view is obstructed by the aircraft. Inside the cockpit, sometimes the two pilots' COMM are split (ATC/Ramp Control and maybe INPH with push-crew).
There have been fatal mishaps during Push-back and during the STOP-go after added LATE BAGS.
Worse still have been the LACK of COMMUNICATION once the victim is on the ground, with a line of rush-rush hub departures wanting to taxi near the downed victim; & gun-ho operator wanting to move the now- blocking aircraft.
? Could any list of mishaps, or equipment damage, persuade you toward the idea of redundant safety features during Push-back? Unfortunately, even the added safety feature (long cord to working Headset) has induced other problems/injuries -- your proposal to avoid any outside Headset might be justified by those odd cases.
Literature cites $$$-damages, injuries, and fatalities (see Bob Mathew's papers from ISASI 2003, and ICAO Journal, #3, 2004 "Ramp Safety"). Not sure any history would add to this discussion, since any added safety feature [eg, voice COMM] induces added risk, & additional failure modes.
=== // ==
My own record of non-fatal Ramp Mishap cases supports the statement (below) in the GAO's rpt. Even some fatal cases were NOT recorded in any mishap report, leaving the factors uncertain, found only in personal records collected by individuals. For Ramp Mishaps, my main concern is
a cascading _interaction_ of failures, during Push-back or Late Bags, due to mis-communication, & lack of view from Cockpit nor Tug.
GAO-08-29, Nov2007,
Runway and Ramp Safety, this from pg 48:
"We found no source of comprehensive data on airport ramp accidents. Various aviation entities collect ramp accident data, but they are not complete enough to be useful for industry wide analyses, and, in many cases, the entities were not willing for competitive reasons to publicly disclose the data. Many industry stakeholders indicated to us that they lack complete ramp accident data. Without such data, it will be difficult for the aviation industry to understand the nature, extent, and cost of ramp accidents and to allocate appropriate resources and methods to improve ramp safety...."