What's the difference between underhung and underslung?

Underhung

Definition:

(a.) Resting on a track at the bottom, instead of being suspended; -- said of a sliding door.
(a.) Having the lower jaw projecting.

Example Sentences:

Definition:

Example Sentences:

(1) Applications by fixed-wing and helicopter underslung spray systems equipped with hydraulic nozzles provided good coverage of test areas as indicated by the mortality patterns of sentinel mosquitoes.
(2) The fixed-wing (Ayres Thrush) aircraft treated 260 ha (640 acres) in 45 min and could carry a full load of 1500 liters (400 gal) at temperatures in excess of 38 degrees C. In contrast, the helicopter (Bell UH-1) with an underslung spray system (Simplex Model 6800) required over 2 hrs to treat the same area at lower temperatures and could not carry a full load of 570 liters (150 gal) at temperatures greater than 38 degrees C.
(3) As a test pilot I was evaluating the pure flying qualities of the aircraft or systems – such as lighting systems for a cockpit, or sighting systems, or underslung loads.