From Halopedia, the Halo wiki
The D79-TC Pelican, formally designated Dropship 79 Heavy - Troop Carrier, is a UNSC dropship designed by Misriah Armory. Infrequently in service as early as 2526, the D79 had become the UNSC's standard dropship by 2557, supplanting the D77 and D77H models. A gunship variant (the G79H-TC/MA) is also produced.
Unlike the D77 and the D77H Pelicans, the D79 features a twin-bubble canopy akin to that of the 21st century Mi-24 Hind gunship/attack helicopter; flight controls and frontal weaponry triggers are linked to the lower seat, while the dorsal turret is manned through the upper seat. The D79 Pelican features increased hull armor and more powerful engines compared to its predecessors. It has a sleeker, more rounded fuselage which presumably improves its aerodynamics. A tall air intake is located immediately adjacent to the fuselage on either winglet, while a shorter but wider intake is mounted in front of and beneath each forward thruster; two smaller intakes are located above these. Two small maneuvering thrusters are mounted on either side of the fuselage. The Pelican is armed with a pair of GAU-53 70mm rotary cannons mounted on a gimbal, below its nose.
Misriah's D81-LRT Condor uses an airframe strikingly similar to the D79's, as it uses the D79-TC Pelican as the base. However, the Condor possesses a slipspace drive and additional thrust nozzles, in addition to substantially greater length.
In addition to the standard dropship model, a gunship model (designated Gunship 79 Heavy Troop Carrier/Mobile Armory) is also used. This version incorporates heavier armament than the dropship version and additional weapons and ammunition racks for the resupply of ground troops.
The Liang-Dortmund Corporation has access to specialized Pelicans suited to their needs.
In the level Infinity, Pelicans can be shot down by enemy fire, despite their actions being scripted, which can cause them to fall on top of the player and kill them. Additionally, sometimes the pilots will be killed, resulting in the aircraft crashing but not being destroyed. The Pelican's cockpit will be open and the aircraft can be flipped, but it cannot be piloted by the player.
List of appearances