At the 2013 Twin Commander University, David Tenenbaum gave a lunch presentation on his successful efforts to develop, certify, and produce a hydrocarbon-resistant nylon-blend pod mounted on the belly of his Twin Commander that could hold four small GoPro HD video cameras for spectacular, unobstructed in-flight footage. We asked him to author a story about his project, including the latest news about it.
As corny as it sounds, my wife and I got our Twin Commander 980 to be our “magic carpet,” to let us take the longer-distance trips to interesting places we always wanted to see.
Our first planned big trip was to Alaska. Since we both were formerly photojournalists, of course we wanted to come back with pictures, primarily of Mt. McKinley since we planned to fly up and around it.
Someone brought the GoPro cameras to my attention (all the cool kids use them for skateboarding, skiing, bungie jumping, and mountain biking). We got one of the tiny things (would you believe 2.3-inches wide, 1.6-inches high, and 0.8 inches deep) and ran some tests. Sure enough, it gives amazing HD-quality video. At the same time we love crisp images, the kind you can only get if there is nothing between the camera lens and the subject, meaning not shooting thru the cockpit glass windows. So I mounted it solidly to our rear tie-down bracket, and off we went.
The video was breathtaking, and the best part was that all I had to do was turn the camera on during preflight, and then just fly the airplane. No constant fiddling, and I could pay attention to flying. But it was pointed out to me that what I had done –– mounting it on the tie-down bracket –– did not have FAA approval.
We realized we wanted to do more of this airborne video stuff, but we wanted to do it legally, which meant getting an FAA-approved Supplemental Type Certificate (STC). We also realized it would have been even better if we had cameras pointing in all four directions (front, back, left, and right).
So the mission was to design a pod (we called it “Eagle360”) that could hold four cameras; that could be certified for a wide range of aircraft; that was strong, safe, and simple to use; that could be mounted on the aircraft and removed in seconds; was reliable; and by the way, really affordable. After all, when the cameras cost just $300 you really cannot charge too much for the pod they go in!
Next came learning about the STC process. Turns out that for things that go on the outside of the aircraft the FAA mostly worries about two things:
- Will it disturb airflow to a control or lift surface?
- What additional lift and drag does it develop, how will the mounting design absorb that, and how will the device absorb these forces?
So, a lot of the data we had to produce on a prototype was to measure lift and drag, and that meant installing pressure sensors pointing down (lift), and to the front (drag), and logging the measurements at lots of different airspeeds, altitudes, and angles of attack. The first lesson I learned was that flight test is really hard flying! Hitting all the numbers while recording time and other variables while working with ATC in the Boston area to do weird step-climbs is stressful and exhausting. I have a newfound respect for people in the flight-test business. Turns out it is way harder than guys like Neil Armstrong made it look on TV!
To figure if the pod structure itself can hold up, you have to do a thing called “Finite Element Analysis” where you feed your design (including the strength of the materials you are using) into a computer program which chops it up into something like 80,000 little pieces, then figures out what each of those pieces would “feel” as you hit them with more and more lift and drag forces. You keep cranking the forces until something breaks, and the computer tells you where the failure will take place and what margin of safety you will have. We designed the pod to have margins of safety even while moving at 408 knots at sea level. If any of you go faster than that, can I come for a ride?
In the course of developing the Eagle360 we had lenses that got covered with frost at altitude, vibration that made it look like we were flexing the aircraft’s skin, batteries that froze, and fasteners that fractured. We learned about venting, and about plastics. We wanted to make the pod out of clear plastic, but all clear plastics get cloudy and brittle if exposed to hydrocarbons such as are found in avgas/JetA, oil, etc. We learned lots of tips about easy editing of video, camera care, power requirements, how to make structures fail safely, and how much to over-design them. It has been a non-stop education of weird knowledge!
After a mere two years of work we were granted an STC by the FAA for 52 types of airframes, ranging from Cessna 152s to CJs and Phenoms. Happily, Twin Commander pilots have been great early adopters. The DOD recently flew a pod to test a classified antenna system, and people are coming up with commercial uses as well. It has also led to some of the most fun flying I have ever done, including a formation flight with an L-39 and an aerobatic air show star!
Now what? We designed the camera pod to have room for cool new stuff, and we are flight testing the first development: an expanded battery pack that will power four cameras for more than six hours each. Also on the list are reliable remote control and capturing cockpit audio, as well as GPS logging so the video can be played back against a map view. We are sure people will come up with new cool things they need for applications we haven’t even dreamed of.
Our hope was to make high-quality video accessible to all kinds of pilots, and we are giving it our best shot!
To learn more about the Eagle360, go to David’s website: http://airbornesensor.com/index.html