Stall Speed, Flaps Down: 91 mph (146 kph) at 16,000 lbs (7 257 kg)
The speed that an airtanker flies at when making retardant drops on a fire is related to Vs. This is expressed as a formula (1.3*Vs). According to the specs found on the Queen Bee web site, the drop speed is in the 120 to 130 mph range. For a more detailed discussion of the calculation of the drop speed (from which I based this discussion) using the AT-802 as an example, go to this BLM aviation page, an automatic download of a MS word document.
TL Stein offers this explanation of stalls, retardant drops, terrain, and fire-produced weather:
Stalls are to be avoided in ALL cases, excepting the landing phase of an aircraft. In the air tanker world, landing is the only place you want a STALL. Fire produces it's own weather conditions. A tanker making a drop in a canyon can experience a tailwind on approach to the drop, which drops the forward airspeed. Over the fire, a severe lift condition can and does occur, due to the heat raising from the fire. During the drop phase, the aircraft releases it's load and becomes much lighter. Consider the thermal wind activity over the drop zone, combined with a sudden tail wind. The aircraft can loose enough forward airspeed over the wing to cause it to stall and crash. This is why airspeed / drop speed are critical to the aircraft and the mission. In the real world, stalls are practiced at a good altitude to enable a successful recovery. This is mandatory for a "type rating" in the aircraft you will be certified to fly. Stalls close to the ground, in a fire fighting scenario leave no room for recovery. There are a lot of memorials to pilots who stalled and crashed. Why? Constantly changing conditions over the fire is a good start. You can make two passes over a fire and the flight conditions will never be the same on each pass. The best tanker pilots on earth know this. Each drop you make you run the risk of something going wrong, it's a given and we know it.
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