| Acronym | Meaning |
| DIF | Discrete Increment Filter |
| MF | Middeck Forward |
| TCA | Translation Controller Assembly |
| IOB | InPut/Output Buffer (if Bus |
| LLI | Limited Life Item |
| DP | Differential Pressure |
| HAC | Heading Alignment Circle |
| MCA | Maximum Crossing Altitude |
| DRL | Document Requirements List |
| TECH | Technical |