The "grand opening" of the helipad at a local hospital (Photo #1) became transcendental due to some very photogenic clouds and a colorful airborne ambulance disguised as a helicopter. The cloudy-bright conditions allowed for a diffused but direct light source yielding relatively sharp-edged shadows. The clouds also provided some natural reflected fill light for my subjects. This results in a quality of light very different from heavy overcast or open shade situations, and yields more saturated colors. Photographic Slam Dunk!
In spite of all this lighting goodness, flash can, and did, play a supporting role in my lighting solution. If you look closely, you can see the shadow of the helicopter on the landing pad, so my three subjects could benefit from some additional light. While there was some fill light bouncing off of the clouds, it wasn't enough to provide detail without increasing my exposure to favor my shaded subjects. But had I done that, I would have blown out (overexposed) the blue sky/wispy cloud background.
In this cropped portion (Photo #2), you can see the shadow (arrow) cast by the speedlight I aimed into the patient compartment of the helicopter. Shadow notwithstanding, the addition of the flash gave me plenty of subject detail without compromising my cloud-friendly exposure settings.
Let me add a few words of caution. First, the cloud cover, acting as a diffuser, effectively reduced the sun's output by a full stop. This allowed me to select a flash-friendly exposure time of 1/250 of a second and an aperture of F 13. The speedlight doesn't have much juice when fired at that distance, but you don't need much, since its output is added to the light already filling the shadows. The trick is to not blow out the highlights, which almost happened in this shot.
Helicopters and fire engines - Two of my favorite things!