16 December 2013

The Research Flight That Was Meant to Happen

We had an incredibly interesting day/evening yesterday, but before I get into the details, I wanted to start by mentioning that I traveled up to North Redfield, NY today (on the Tug Hill plateau east of Lake Ontario) to RAISE one of our instruments about 3 feet higher in order to keep it out of the snow. The instrument was already ~5 feet above the ground and the snow was about a foot or so below it. This is at one of our ground sites, which I've talked about in previous posts, that is run by folks from the University of Utah and has received a total of 80 inches of snow in the last 7 day with more to come this week. Here's one photo I took today - the rest can be found at the very bottom of this post!

Snow 4-5 feet deep at the OWLeS ground site in North Redfield, NY

The Flight That Almost Wasn't

So I think I should tell this like a story, in chronological order. This may be a bit lengthy, and I apologize, but looking back I'm quite amazed at how everything went last night and how it just all worked out so perfectly in the end. Anyway, I hope you all enjoy this and aren't dozing off 5 minutes from now haha.

Flight Plan - At the OWLeS 1 pm weather briefing yesterday (Sunday), it appeared as if a relatively weak long-fetch single band was going to develop sometime around sunset but die off during the overnight hours. We weren't expecting anything spectacular for sure, with some of us perhaps even thinking that it wasn't worth it to even fly the King Air. Ultimately, we decided we would have a 5:30 pm takeoff, fly for 3.5 hours collecting data over the weak band, and call it a night.

Pre-flight - My advisor and I arrived at the local airport by 2:30 pm, expecting to go through the typical pre-flight routine. It was quite windy outside at this time, and fairly cold. The other crew members had already arrived and immediately informed us that while the plane was sitting outside being fueled, blowing snow from the hangar roof had collected on the wings of the King Air and had begun to melt. This is a big no-no, as any melted snow on the wings would freeze after take off and cause issues with flying. In the words of our aircraft scientist Jeff, "We might not be able to fly today, guys...". And this was ~3 hours before our scheduled take-off.

They moved the King Air back inside the hangar, brushed off the snow, and dried the plane off - all while keeping the hangar as cold as possible so that the temperature of the metal surface of the plane would be cold enough as to not melt any snow that fell on it. However, we were still concerned because the plane must be taken back outside about an hour before take-off in order to turn on some of the instruments, like the radar. If snow was still blowing off the roof, the plane would have to be brought back inside and dried off AGAIN - and that would have essentially ended our chances of flying. We can't fly past 10 pm, so for a 3.5 hour flight we need to be in the air by 6:30 pm at the latest.

Boarding and take-off - Well, we pushed the plane back outside about an hour before take-off, and lo and behold the wind had died down significantly! No blowing snow anymore. Hallelujah! It looked like we'd be flying afterall. So around 5:15 pm we all loaded onto the plane to get ready for the flight. A very light snow had begun to fall, but it was nothing to be concerned about. We've taken off in light snow before.

As our pilot began turning the King Air to taxi to the runway, we quickly figured out that the brakes on one of the plane's wheels had frozen up. The wheels would not turn at all. Obviously, we cannot take-off or land with a wheel that does not turn. So our pilot tried moving the King Air forward in an attempt to brake the ice loose. No luck. He tried again. Once again, nothing. At this point, there really wasn't anything we could do except push the plane back into the hangar and let the ice melt - ending our chances of flying. Our pilot gave it one last shot, and all of a sudden the wheel broke loose from the ice and we were good to go. Wow! Sigh of relief.

We taxied to the runway to take off. By this time, the light snow that was falling had turned into a moderate snow. We stopped at the runway as our pilot radioed Air Traffic Control to get clearance to take off. We were told to wait 5-10 minutes as another plane was in the area and needed to move first. We ended up waiting about 15 minutes before we were given clearance, during which an inch of snow had accumulated on the wings. This could have presented another problem. Right before we entered the runway, our pilot told us that if the snow on the wings had not blown off by the time we were traveling 60 knots (70 mph) down the runway, we would have to abort take-off - again, this would probably end our chances of flying. We took off down the runway, and fortunately the snow blew off rather quickly and before I knew it we were in the air and headed to Lake Ontario.

Flight - The flight itself, compared with what we had just gone through, was fairly easy. However, once we got to the weak developing snow band and began flying through the tops of the clouds, we noticed that there was a lot of supercooled liquid water in the clouds. The air temperature was -25C. Supercooled liquid water is water that remains a liquid at temperatures below freezing. Water, under the right conditions, can actually exist in the atmosphere as a liquid down to temperatures as low as -30C or even -40C. Pretty cool. Anyway, supercooled liquid water freezes immediately once it hits an object, kind of like freezing rain. That's how you get those really cool, wind-blown ice features on trees at the tops of mountains in the winter. Those features are called rime, or rimed ice. 

Anyway, too much supercooled liquid water presents a MAJOR issue for the King Air (and any airplane, really). When the liquid hits the wings of the plane and our instruments attached to the wing, it freezes and creates a layer of ice on the wings and instruments (and ice can be pretty heavy). Eventually, if the ice builds up too much, it causes aerodynamic problems and will also prevent the instruments from working properly (if at all). Planes have the ability to break a lot of the ice off the wings, but any ice that builds up on the instruments will remain there until landing. So we were encountering a LOT of liquid in these clouds, causing some ice to begin to accrue. And this was at the TOP of the clouds. Eventually a couple of our instruments stopped working, and we still had to fly INTO the clouds at lower altitudes later in the flight. The possibility existed that were might have to end the flight early if the icing was worse down below.

When we did finally drop down to a lower altitude, we weren't sure what to expect in the snow band clouds. More liquid? Or ice crystals? We were hoping the cloud would mostly be made of ice crystals because ice crystals are already frozen and do not stick to the instruments. But if there was so much liquid at higher altitudes, what were the chances that there would be ice crystals below? Turns out that was indeed the case - mostly ice crystals at the lower elevations. We lucked out again and were able to finish the flight as we had planned! Not only that, but somehow the snow band had intensified immensely during the flight and was dumping snow at 3 inches/hour below! One of our OWLeS groups measured 17 inches of snow over a period of 6 hours. In hindsight, this was perhaps the strongest band we have seen since OWLeS began (even though it was a very short event...the band weakened during the early morning hours). Very surprising, and we collected a great data set!

Landing and post-flight - You thought the story was over? Haha, yeah right. The conditions at the airport where we were to land were pretty good as we were coming in - overcast with some light snow and visibility of 5 miles. We came in for the landing, touched down successfully, and began taxiing back to the hangar. We parked the plane outside the hangar and went inside to warm up and put some of our belongings away.

We had to go back outside though to help bring the plane into the hangar. Total blizzard! Heavy snow and gusty winds, seemingly out of nowhere. The airport we're at has these little "tugs" that push the planes into/out of the hangars, similar to those little vehicles that push commercial airliners away from the gate. Anyway, the tug could not get any traction to pull the plane due to the quickly-accumulating snow. So we all had to actually help push the King Air back into the hangar - with our own hands! We were throwing sand under the tires of the tug to give it traction as well. Never thought I'd be doing that at the end of the night. Fortunately, we got the plane back in the hangar. Finally, we were done! Below are two pictures of some of the rimed ice that had built up on the instruments and remained all the way to the end.

Rimed ice on a few of our instruments

A big chunk of rimed ice from the plane
So I hope that story was as gripping for you as for me. Given that we were almost prevented from flying 3 separate times before we even left the ground - and then we ended up collecting a tremendous data set from an unexpectedly strong lake-effect snow band - I'd say yesterday was just an all-together awesome day!

As promised, here are the rest of the photos from my visit to North Redfield today...

Lacona, NY - at least 3 feet of snow here

The hotplate I had to raise ~3 feet higher. Otherwise, it would eventually get buried by all the snow.
The top of the plate is ~5 feet off the ground already

I was standing on about 2 feet of snow in this photo. The deepest spots came up to my chest!

The huge house at the site

Beautiful snow!

One of the University of Utah insturments

Huge icicle

The raised hotplate. Now that's a lot better! I hope I don't have to come raise it AGAIN though...

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