A small twin is not going to get a lot of attention from the local photographers at Paine Field on a busy day with lots of traffic. However, it was still relatively early in the day and the air still had a fair bit of moisture in it. I took a guess that this might result in some prop vortices so decided to shoot it anyway. Sure enough, some swirls of moisture showed themselves. Not a dramatic look to them but still what I was after and there wasn’t anything else to do anyway!
Damp days can make for great prop vortices on takeoff. However, I have been feeling less than satisfied with my results recently. As I was going through some shots, I made a discovery that should probably have been something I worked out before. I like to have a good amount of prop blur so drop the shutter speed down when I can. I go with a high frame rate with the aim of getting a good sharp shot amongst the more blurry examples.
As I go through the shots, the sharp ones have okay prop vortices but not great. Then I will come across some really nice vortices but the shot is otherwise not sharp. It seems that, in panning with the plane to get a sharp shot, the trailing vortex gets blurred out. If I am not panning well, the vortex can be the thing I have tracked better and it shows up well. I have seen shots from others with the props almost frozen with a high shutter speed and the vortices easily seen.
Consequently, I am going to have to make a decision in future. How much prop blur do I want versus the ability to see the vortices well. A little trial and error will be involved. At least it is fall/winter so the Pacific Northwest will probably provide me plenty of damp days on which to experiment!
My buddy Paul was visiting so we had a day out looking for some interesting shot opportunities. We started off the day at Paine Field before the sun was really up. A Dreamlifter was due in and we figured we would give it a try. However, as we drove towards Everett, the fog was pretty thick. The field is on the top of the hill so we thought it might be clear, but things did not look promising as we got closer. The low cloud was also blocking off the sun that was just above the horizon which, given that it would have been backlighting the jet, might have been a bonus.
The Dreamlifter came out of the cloud very late on the approach and I was able to grab a few shots of it as it emerged. It was a rather ethereal look as it came into view. The dampness of the air meant that the plane was pulling vortices as it floated across the threshold and in to the touchdown zone. Conditions might not have been the sort of thing that sounded good, but the result was a really cool shot opportunity. As the plane taxied in to park, we got more shots of it although there was one that would have been fantastic, but Paul only spotted it when it was too late and I didn’t see it at all. I won’t say what it was but maybe there will be another chance in which case you will see it here!
With a sharp LERX, the F-16 regularly pulls a nice vortex on each side as it maneuvers hard. Getting a shot of that is not a surprise. However, I have recently been slowly making my way through shots from RIAT (months after the event) and I was working through some shots of the Belgian F-16 display. I came across a shot of the jet pulling and rolling, taken from astern of the aircraft. I noticed a second, smaller vortex trailing from the tail plane. It appears that, with differential tail for the roll, there is a vortex coming from the tail plane – possibly at the route. This pleases the old aero guy within!
A couple of Kenmore Air planes departed from Kenmore while I was at Log Boom Park. The conditions were pretty damp and humid (and were about to be joined by pretty heavy downpours of rain!). This meant the departing planes had a good chance of pulling some streamers from the prop tips. Sure enough, when the Otter took off (and it started the takeoff run a little early which helped the shooting angles) the prop was streaming some vapor. The shape of the cone of the tip vortices as they flow across the fuselage was quite interesting.
A little while later (and just before the downpour began), a turbo Beaver came out. It, too, pulled some nice vapor from the prop tips as it accelerated across the water. A bit of a cross wind was apparently coming in (no doubt related to the impending storm) and they got airborne one float at a time. At this point we retreated to the car – but not in time to avoid the rain entirely!
Departure day at RIAT was a bit overcast, much like the majority of the show. The damp atmosphere did have the positive effect of meaning many of the more powerful prop aircraft were pulling vortices from the tips of their propellers. This was most obvious earlier in their take off runs but you could get a pretty good view of it even head on from where I was sitting in the FRIAT stand. Here is one of the Hercs that was beating the air into submission.
Damp and cloudy days are not always ideal for aviation photography but they can provide some interesting options. One weekend I was up at Everett when they were approaching from the south. The jets broke out of the cloud at quite low level but there was some light from the side coming under the clouds. The damp air meant that the jets were pulling some conspicuous vortices as they flared for landing. They were a long way off but it was possible to get some shots of them. The 747 produced vortices that were easier to see but the 787s didn’t do too badly either.
San Francisco Bay tends to provide a bit of moisture in the air that shows up as vapor clouds in the trailing vortices of approaching airliners. Before the planes reach Coyote Point, they are often trailing these streamers but, as they get closer to the airport, something about the conditions must change as they do seem to peter out. However, on some occasions, the moisture content must have been higher as the streamers lasted longer.
Engine nacelles are optimized for cruise performance. At high angles of attack, their shape results in some rather awkward flow properties which can influence the wing performance above and behind them. In order to control things, you will see small vanes attached to one or both sides of the nacelle that generate a vortex that stabilizes the flow somewhat. As an aircraft rotates at takeoff, the strength of this vortex increases and it will often become visible as moisture in the air condenses within in. This vortex will stream back up and over the leading edge of the wing.
When you are inside the aircraft, this is pretty easy to see provided the conditions are right. From head on or aft they are also quite conspicuous. It isn’t often that you get a good view from above. When I was flying over LAX in the helicopter, the aircraft departing from the north complex had better light on them. However, the runways are offset so the rotation point is further west and beyond the area in which we are allowed to fly. However, you can get a view from above and behind as the jets get airborne. An El Al 777 took off while I was up and I managed to get some shots of it as it rotated and climbed away and the vortices were clear to see as the angle of attack increased.
Every once in a while, when photographing a fast jet at transonic speeds, you might get something in the background that allows the diffraction caused by the formation of shockwaves to be visualized. I have posted about that here. I was in Vancouver and shooting the floatplanes taking off from the harbor (since it is a Canadian harbor, perhaps I should write harbour). As I was looking through the images zoomed in to check on sharpness, I realized that there was a visual effect of a similar nature. (If you think this is a Schlieren effect, it is not. That is a technique that involves a certain type of lighting to show the density differences but should not be applied to every time you see it in the wild.)
I don’t know whether what is showing up is the result of shocks forming on the props as they spin rapidly or just the tip vortices causing a similar effect. You can often see diffraction in trailing vortices. Whatever the reason, as you look above the aircraft at the patterns of structures on the shoreline beyond, you can clearly see some interesting effects. Since the props are spinning fast and there is an overlap of the wakes from each pass of a blade, the shapes are rather complex. Now I know that this is a thing, I might be tempted to take a longer lens and see what I can get in more detail of this interesting visual effect.