The Final CASIE flight

Due to fog and low visibility today (31st), the team will pull the plug on this deployment and prepare the aircraft and support equipment for shipment back to the USA. This weather has stopped all airline service to Ny-Alesund, so the flights are backing up. Most all of us will be departing on Monday (weather permitting!).

 The SIERRA performed very well during this op, especially considering that it is a prototype with low flight hours. In fact, this deployment way more than doubled the number of flight hours on the platform. The aircraft unintentionally flew through clouds and potential icing conditions. The engine, flight controls and other aircraft systems never missed a beat. For the most part, we were able to work around the unreliability of the Iridium link. This is an issue the team will fully address upon our return to the USA

The only issue related to flight safety was a broken thrust link on the engine that was discovered after flight #7. Apparently, there were sufficient alternate load paths available to carry the propeller loads into the airframe. A little bit of luck is a necessary commodity when flying UAS in harsh environments and the gods were smiling upon us. The thrust link was replaced with a spare and reinforced with some aluminum provided by one of the repair shops here. You just can’t have enough spares, so bring everything you have because you won’t know what you’ll need (note to self: remember 3-hole punch next time, they don’t have them here).

The project also had to get an extension of hours to continue flying. There are established inspection schedules and we were up against one that would have required significant disassembly of the aircraft. We did not have the time to complete it, so we asked the Airworthiness and Flight Safety Review Board to allow us to fly two additionial flights without doing the inspection. After a thorough discussion about the nature of the inspection and developing some risk mitigations, the Board granted approval. The team appreciates the dedication and resposiveness of the Board in finding a way to allow the flight op to move forward safely.

Of course, the last flight (#11 on 29 July) could not have been easy and uneventful. What’s the fun in that? Satellite imagery showed mostly cloudy conditions over the sea ice, but does not tell you where the cloud bases are. The flight plan involved a long transect to the northwest and imaging local glaciers with a total mission distance of 1000 km. For most of the flight, the relative humidity was reading 95%, but since the outside air temperature was +5 C there was no potential for icing. The aircraft was redirected north in an attempt to find clearer skies.

After returning from the sea ice mission, the aircraft was to be tasked to fly 60 nm over the local glaciers to provide imagery for our PI and the British and German research teams. Unexpected weather had descended on Ny-Alesund and the ceiling was only 300 ft with ½ mile visibility. The SIERRA is not equipped with autoland and must be flown with a manual RC controller for takeoff and landing. The team was quite concerned about our ability to recover the aircraft safely.

During the early check flights, the team had optimized several autonomous approaches for landing in poor weather and that preparation really paid off. We selected a right hand pattern for runway 12 in light wind and fog. The SIERRA entered this pattern at 1000 ft MSL and although we could not see the aircraft we could certainly hear her with those straight pipes on the engine. The GCS operator commanded the autonomous approach pattern which caused the aircraft to descend and make passes up the runway at 200 ft AGL. It was very erie seeing the aircraft emerge from the fog, but then disappear again. We had no choice but to lower the altitude over the runway and we did that twice before feeling like we could pick up the aircraft far enough out to make a landing. With full engine idle and full flaps commanded on the RC handset, I engaged manual control on short final at 125 ft AGL as the aircraft just became visible. The autopilot had done a great job of altitude control and ground track accuracy, so the descent and flare to landing were uneventful (see link to video). Anticipating potential problems and formulating solutions ahead of time makes people look smarter than they probably are. Luck still favors the prepared, though.

It has been an excellent deployment and we’ve made lots of new friends from many different countries. The folks at Kings Bay do an amazing job supporting the researchers and the infrastructure here is second to none. The team hopes to return some day.

 
Final Numbers:

59.9 hours on this deployment from 11 flights

2923 kilometers flown over sea ice (goal was 2500 km)

To view a short video of the final approach and landing click on the link below.

http://geo.arc.nasa.gov/casie/FoggyLanding.avi

 
– Posted by Mark Sumich, SIERRA Chief Pilot

 

1 thought on “The Final CASIE flight”

  1. It was a pleasure to have you and your team in this village. Remarkable science combined with an open mind to this international community.
    Please return in future with the same good spirit. All the best with analysing the data.

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