TCDS (Type Certificate Data Sheet). See Type Certificate Data Sheet.
TCLT (tentative calculated landing time) (air traffic control). A projected time calculated for the adapted vertex for each arrival aircraft based upon runway configuration, airport acceptance rate, airport arrival delay period, and other metered arrival aircraft.
TCLT is either the vertex time of arrival (VTA) of the aircraft or the tentative or actual calculated landing time (TCLT/ACLT) of the previous aircraft plus the arrival aircraft interval (AAI), whichever is later. TCLT will be updated in response to the aircraft’s progress and its current relationship to other arrivals.
TCP (trichresyl phosphate). A colorless, combustible compound, (CH3C6H4O)3PO, that is used as a plasticizer in aircraft dope and an additive in gasoline and lubricating oil. TCP aids in scavenging lead deposits left in the cylinders when leaded fuel is burned.
TDC (top dead center). The position of a piston in the cylinder of a reciprocating engine when the piston is at the top of its stroke and the piston pin, crank pin, and the center of the crankshaft are all in line.
tear-down area (overhaul shop). The area in an overhaul shop set aside for disassembling the equipment being overhauled. Tear-down areas are usually located near the point the equipment is received into the shop. There are facilities in the tear-down area to remove most of the grease and dirt from the equipment before it is taken into the main part of the shop.
TEB (triethyl borane). A fuel additive that ignites on contact with oxygen. It is used as a catalyst to ignite the low-flammable JP-7 used in the Lockheed SR-71 fuel during engine start and afterburner lights.
technetium. A synthetically produced, silvery-gray, metallic chemical element. Technetium’s symbol is Tc, and its atomic number is 43. Technetium is used in the manufacture of corrosion-resistant steel.

Technical Standard Order. See TSO.
technician. A specialist in one of the technical fields. In research and development, technicians often assist engineers. The engineer’s knowledge of the theory behind the project is usually greater than that of the technician, but the technician usually has a more practical approach and is able to build the things the engineer designs.
tee fitting. A connector, made in the shape of the letter T, for joining either rigid or flexible fluid lines.