CAR requires that all aircraft instruments and installed equipment be operative prior to each departure. It is allowed operations with inoperative equipment determined to be nonessential for safe flight.
The deferral provision of is widely used by most pilot/operators. Its popularity is due to simplicity and minimal paperwork. When inoperative equipment is found during preflight or prior to departure, the decision should be to cancel the flight, obtain maintenance prior to flight, or to defer the item or equipment.
Maintenance deferrals are not used for inflight discrepancies. The manufacturer’s AFM/POH procedures are to be used in those situations. The discussion that follows assumes that the pilot wishes to defer maintenance that would ordinarily be required prior to flight.
Using the deferral provision, the pilot determines whether the inoperative equipment is required by type design,CAR, or ADs. If the inoperative item is not required, and the aircraft can be safely operated without it, the deferral may be made. The inoperative item shall be deactivated or removed and an INOPERATIVE placard placed near the appropriate switch, control, or indicator. If deactivation or removal involves maintenance (removal always will), it must be accomplished by certificated maintenance personnel and recorded in accordance with CAR.
For example, if the position lights (installed equipment) were discovered to be inoperative prior to a daytime flight, the pilot would follow the requirements of CAR.
The deactivation may be a process as simple as the pilot positioning a circuit breaker to the OFF position, or as complex as rendering instruments or equipment totally inoperable. Complex maintenance tasks require a certificated and appropriately rated maintenance person to perform the deactivation. In all cases, the item or equipment must be placarded INOPERATIVE.
All aircraft are eligible to use the maintenance deferral provision subjected to once an operator requests an MEL, an approved by DGCA, then the use of the MEL becomes mandatory for that aircraft. All maintenance deferrals must be accomplished in accordance with the terms and conditions of the minimum equipment list (MEL) and the operator-generated procedures document.
Deferred defects are defined as those defects reported in operational service which is deferred for later rectification.
Carried forward defects are defined as those defects arising during maintenance which are carried forward for rectification at a later maintenance