The TLB (Technical Log Book) is the aircraft's technical record. It is where the crew writes up discrepancies found before, during and after the flight, where maintenance records the corrective action or the deferral of the item under the MEL, and where the aircraft's release for the next flight is kept. Brazilian regulations have no document called a TLB: that content sits in the logbook (diário de bordo), regulated by Resolution No. 773/2025 of ANAC (Agência Nacional de Aviação Civil, Brazil's civil aviation authority), in the aircraft log required by RBAC 135 and in the maintenance records of RBAC 43. RBAC stands for Regulamento Brasileiro da Aviação Civil, the Brazilian Civil Aviation Regulations.
Understanding the correspondence avoids two mix-ups: thinking a book is missing on board, and thinking the logbook is only a record of hours.
The TLB as international practice
The most detailed example is in European regulation. EASA's continuing airworthiness rule (Part-M, point M.A.306, aircraft technical log system) requires operators in commercial air transport, commercial specialised operations and commercial training organisations to keep, for each aircraft, a technical log system containing:
- information about each flight necessary to ensure continued flight safety;
- the current aircraft certificate of release to service (CRS);
- the maintenance status, with the next scheduled maintenance due;
- all outstanding deferred defect rectifications that affect the operation;
- guidance on the maintenance support arrangements.
EASA's own guidance material describes the technical log as the system for recording defects and malfunctions during operation and the maintenance carried out between scheduled base maintenance visits. The text is in the Easy Access Rules for Continuing Airworthiness. Other authorities use other names for the same function: the US air taxi rule, 14 CFR 135.65, speaks of an aircraft maintenance log.
What goes into a TLB
Putting together what the European rule asks for, a typical TLB has five blocks:
- Flight data: date, places and times of takeoff and landing, and accumulated hours, to know how much is left until the next maintenance.
- Discrepancies: any failure, defect or malfunction observed, dated and signed by the commander. Under the European guidance, the page also records a flight with no defects, to keep the record continuous.
- Corrective action and release: what maintenance did and who released the aircraft.
- Deferred items: each postponed defect, with a cross-reference to the original entry, date, description and, later, the final rectification.
- Maintenance status: what was done last and what comes due next.
Where this sits in Brazil: the logbook
ANAC Resolution No. 773/2025, published in the DOU (Diário Oficial da União, Brazil's Official Gazette) on June 30, 2025 and in force since January 1, 2026, regulates the logbook and repealed Resolution No. 457/2017 (art. 16). What it changed is covered in Resolution 773/2025 and the digital logbook.
Article 2 settles the underlying question: the logbook is the official means of recording the aircraft's operations, its maintenance actions and the other required information. The TLB blocks map like this:
| TLB block | Where it sits in Brazil |
|---|---|
| Flight data | Logbook, art. 6 of Resolution 773 |
| Reported discrepancy | Art. 6, XIII: technical discrepancies and who detected them; RBAC 135.65(c)(1) |
| Corrective action and release | Art. 8, sole paragraph; RBAC 43, sections 43.9 and 43.11 |
| Deferred item | Deferred corrective action (ACR, ação corretiva retardada): art. 8; list of ACR items in IS 91-012C |
| Maintenance status | Art. 9: last and next maintenance, acknowledged by the pilot in command |
Article 8 requires the operator to arrange the correction of technical discrepancies identified by the crew and to make the logbook available to the person responsible for the approval for return to service, who records the corrective action or the authorization of deferred corrective action. Article 9 requires the operator to inform the pilot in command of the type of the last maintenance intervention (except transit and daily checks), with its date and the person responsible, the type of the next one and the airframe hours expected for it. The pilot acknowledges this with a signature before the flight. It is the Brazilian equivalent of the TLB's maintenance status.
In the physical logbook model cited by IS 43-012B (IS stands for Instrução Suplementar, ANAC's supplementary instruction), this technical part is Part 2, "Aircraft Technical Status" (Situação Técnica da Aeronave), intended for discrepancies and their corrections, the last inspection and the due date of the next one. IS 91-012C refers to a "dedicated record corresponding to part II of the logbook", which indicates that this part may be kept separate from the rest of the logbook.
The RBAC 135 aircraft log and RBAC 91
For air taxi operations, section 135.65 of RBAC 135 requires a log on board each aircraft for crew information, flight hours, irregularities observed on each flight and the corrective actions taken or the postponement of the correction. The log may be split into aircraft records and crew records. The pilot in command enters each irregularity observed before, during and after the flight and, before each flight, checks the status of the irregularities entered on previous flights. Whoever takes corrective action records it in the same log. In substance, this is what the industry calls a TLB.
In RBAC 91, the term appears in section 91.213(a)(4): to take off with inoperative equipment under an MEL, the entries in the "aircraft maintenance log" (livro de manutenção de bordo) must give the pilot information about that equipment.
Deferred items: the MEL and deferred corrective action
Deferring an item under the MEL requires an approved MEL. Under RBAC 91.213(a), except for the cases in paragraph (d), takeoff with inoperative equipment is only permitted if there is on board an MEL developed by the operator and approved by ANAC. Under RBAC 135, section 135.179(b) requires an approved MEL and a letter from ANAC authorizing the operation, and the records identifying the inoperative items must be available to the pilot. How to read an item on the list is covered in MEL: how to interpret and apply it.
IS 91-012C, an ANAC acceptable means of compliance, advises keeping on board, together with the logbook, an up-to-date list of ACR items. Its fields include: description of the defect, equipment, MEL item number and repair category, entry date, the page of the record that originated the item, (O) and (M) actions including placards, who released the aircraft and the deadline for the correction. It is the same deferred items block as the European TLB, under another name.
The release: RBAC 43
What the TLB calls a CRS is, in Brazil, the approval for return to service. Sections 43.9 and 43.11 of RBAC 43 require each person who performs maintenance to enter in the record a description of the work, the dates and the name and signature of whoever approved the return to service. Who may approve is set out in section 43.7.
Summary for those coming from abroad
If a manual, a contract or an auditor asks for the TLB, the answer in Brazil is the aircraft's logbook, with its technical part, plus the list of ACR items when the operation uses an MEL. What changes is the name. What matters stays the same: discrepancy recorded, corrective action or deferral based on the MEL, signed release and a pilot who is aware before the flight. The other terms are in the glossary of aviation management, and the difference between the technical control regimes is in RBAC 91 × RBAC 135.
Alis's electronic logbook is accepted by ANAC, and the discrepancies recorded in flight go on to the CTM (Maintenance Tracking, or Controle Técnico de Manutenção), the aircraft's maintenance control.
This article is informational and does not replace consulting ANAC's current regulations or your operation's approved manuals.