They’re attempting to arc the finished foam onto the fire, one of the three methods for foam application. The truck with the nozzle nearly vertical is too close to fire to be attempting to do that; at their close proximity, they’d be better off attempting the roll-on method for the foam, shooting the ground just in front of the fire and pushing the finished foam into the fire itself. The first truck shown attacking the fire, has a good foam application going with a slight angle, closer to the aircraft, and moderate fog nozzle selection, putting some good foam on the fire.
With foam, at the pressure these guys are flowing, they cannot hit the fire directly with a straight stream. This will result in unfinished foam being applied to the fire, and very high temp pooled fuel fires like this one will just eat the unfinished foam, that never gets aerated enough to be able to form a vapor and cooling blanket, is thus ineffective, and just gets eaten up by the fire. This is known as plunging, and it results in high amounts of wasted foam and water, with little accomplishment in suppression.
The AA 383 engine fire at ORD in 2016, you can see the plunging happening in the ARFF truck cams, and the resultant low effect on the fire. Plus, foam/water has little effect anyway on a three-dimensional fuel fire. Crew here needed to cease the foam straight stream that wasn’t accomplishing anything except plunging, dismount a firefighter or two to pull a handline and actually be able to reach the seat of the fire that the crash trucks can’t, and deploy some form of dry chemical powder such as Purple K, in order to really take down that running fuel fire. The other ARFF truck nearly hitting them as it was leaving the scene, as well as the never ending activated PASS alarm, is also noteworthy.
Video here
View: https://www.youtube.com/watch?v=nAf4XmoRRcU