time between overhauls(One important measure of an aircraft engine's overall economics is how often it has to be overhauled, the so-called time between overhaul, typically seen as TBO or TBOH. wiki Alexander Demidov)
service before overhaul(если не в часах. It is a 1930's design meant to deliver 100000 km of service before overhaul, with one valve job along the way. Alexander Demidov)
