Mexicana's JATO-Equipped Boeing 727-200s

Mexicana operated a unique variant of the Boeing 727-200 that had JATO provisions to allow full payload operations out of high elevation airports like Mexico City.

There were only 12 727s that were built with the JATO provision and they were actually the more powerful 727-200 Advanced versions. Mexicana served several high-elevation airports where the 727 would have been payload restricted to account for the possibility of the loss of one engine at takeoff.

At higher elevations, particularly on hot days, wings will generate less lift and jet engines will develop less power than at a lower elevation airport on a cooler day. That's why the runways at airports like Denver or La Paz, Bolivia, are so long.

Mexicana took delivery of special 727s that got around this limitation by having a JATO installation in the lower aft fuselage just behind the wings. These aircraft could be identified by having a shallow dorsal fairing ahead of the #2 intake that accommodated some of the rerouted cables and ducting displaced by the JATO provision. There's a misconception that this fairing is a reinforcement brace, though.

The rocket installation was intended for emergency use only when flying out of a hot and high airport at maximum gross weight. Without JATO, the 727 would have to be payload restricted to account for the need to reach a safe altitude in the event of an engine loss after committing to takeoff. By having JATO, Mexicana could operate its 727-200s at full payload. In the event of an engine loss past V1, the JATO unit would fire and allow the heavily-laden jet to reach a safe altitude.

The JATO provision was made obsolete by later upgrades to the JT8D engine that featured APR- automatic power reserve. It sensed a power decrease from one of the engines failing on takeoff and automatically boosted the power to the remaining two engines by a significant margin.

Images: AWST, Boeing