hobbs meter, aviation, change, time, times, flying, electronic

Time for a Change of Times

By Rob Neil

It is often said that there are only two ingredients necessary for powered flight—airspeed and money. Anyone who has flown a powered aircraft—fixed- or rotary-winged—knows there are two others that are equally essential: timekeeping and documentation.


While airspeed and money will get anything airborne, keeping it there (legally) requires a weight of documentation at least equal to the weight of the aircraft, and much of that documentation revolves around accurate recording of a range of times, such as aircraft engine airframe and component times, fuel use, and crew flight and duty times; safe and effective navigation also relies on accurate timekeeping and documentation.


Accordingly, aviation authorities around the world require operators, maintenance organisations and pilots to measure and record these various times in great detail.

Among the many other parameters operators are required to record for every flight are the time at which it commences, and the total elapsed time of the flight.


In view of the myriad of other aspects required to be measured, weighed, documented and accounted for with great accuracy in preparation for flight, one might assume the measuring and recording of time might be equally strictly controlled.


So just how does an operator/pilot measure and record the “vital” time of flight commencement and total flight time? The rules simply require the daily flight records to be “accurate”; a pilot’s $20 wristwatch is considered to be accurate enough to achieve the requisite “accuracy”, as are the typical 40-year-old mechanical clocks fitted to the instrument panels of many light GA aircraft.


When it comes to recording and documenting the time in service of airframes, engine, propellers/rotors and other lifed components, many operators rely on the ubiquitous Hobbs meter. As ubiquitous as it might be, the Hobbs is nothing more than a mechanical counter connected to a switched power source (e.g. collective and oil pressure). Despite the fact it is not a certified timepiece, and relies on a pilot writing down on paper the time/s displayed on the instrument’s face, use of the Hobbs meter is considered perfectly suitable to measure time in service of aircraft and flight-critical components.


The dangerous practice—certainly not unheard of—of disconnecting a Hobbs meter introduces potentially deadly risks to flight, allowing unscrupulous operators to “cheat” on maintenance by exceeding the safe lives of engines and other time-limited components.


So…while wristwatches, 40-year-old mechanical clocks, human-error-prone pen-and-paper are all “safe” and “acceptable” methods of recording life and safety-critical flight times and time in service, aviation authorities have been slow to accept the introduction of fail-safe, human-error-proof, automatically transmitted (to whomever requires such information) times recorded by electronic flight instruments using GPS atomic clocks that are accurate to within milliseconds of global standard times.


While aviation authorities have good reason to be conservative when introducing changes to any aspect of aviation, in this age of exponentially rapid technological advancement, it is hard to understand any reluctance to accept technological alternatives to mechanical clocks and pen-and-paper—especially when such information can be linked via computer to such things as maintenance records, crew flight and duty time registers, rostering personnel, and potentially even directly to the regulatory body itself, should this be desired.


It is to be hoped that aviation authorities move to accept automated, human-failure-proof time recording soon—and before the time comes that the only human required on the flight deck will a “scribe” whose sole job will be to watch and write down the details displayed on the dial of a Hobbs meter…