| 271 | GY-00a | 1978 | | | |
| 272 | GY-00a | 1978 | | | Renumbered to 512 in 1990 |
| 273 | GY-00a | 1978 | | | Renumbered to 513 in 1990 |
| 274:1 | GY-00a | 1978 | | | Renumbered to 514 in 1990 |
| 275:1 | GY-00a | 1978 | | | Renumbered to 515 in 1990 |
| 276:1 | GY-00a | 1978 | | | Renumbered to 516 in 1990 |
| 277:1 | GY-00a | 1978 | | | HBU-4 hump booster unit (slug),renumbered to 517 in 1990 |
| 278:1 | GY-00a | | | | HBU-4 hump booster unit (slug),built new 1978 renumbered to 518 in 1990 |
| 279:1 | GY-00a | 1978 | | | HBU-4 hump booster unit (slug), renumbered to 519 in 1990 |
| 280:1 | GY-00a | 1978 | | | HBU-4 hump booster unit (slug), renumbered to 520 in 1990 |
| 281:1 | GY-00a | 1978 | | | HBU-4 hump booster unit (slug) renumbered to 521 in 1990 |
| 282 | GY-00a | 1978 | | | HBU-4 hump booster unit (slug), renumbered to 522 in 1990 |
