Test Pilot

My airplane has wingtip-mounted fuel tanks, installed under a supplemental type certificate (STC). In many ways, theyve transformed and improved the machine by adding greater loading flexibility, thanks in part to a gross-weight increase. What drag they produce isnt noticeable, and the additional endurance means the airplane is faster over some trips than it was before. For many of my destinations, I can depart with full tanks, fly to my destination, shoot an approach, miss it and fly home with reserves.

Joseph E. (Jeb) Burnside

Thursday, November 29, 2018 at 12:00 AM ET

Verified

Key Takeaways:

Aircraft modifications, even under a Supplemental Type Certificate (STC), require careful and deliberate test flights to evaluate changes in flight characteristics, particularly stall behavior, as they can transform the aircraft into an essentially "untested" machine.
A fatal accident involving a Bellanca Citabria, modified with vortex generators, occurred when the pilot attempted stall practice at a dangerously low altitude, compounded by sun glare and a lack of specific guidance from the manufacturer on post-modification test procedures.
The NTSB determined the accident's probable cause was the pilot's operation at an altitude too low for stall recovery, his inability to recognize altitude deviations, and insufficient knowledge of the modified aircraft's stall performance due to inadequate manufacturer information.

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My airplane has wingtip-mounted fuel tanks, installed under a supplemental type certificate (STC). In many ways, they’ve transformed and improved the machine by adding greater loading flexibility, thanks in part to a gross-weight increase. What drag they produce isn’t noticeable, and the additional endurance means the airplane is faster over some trips than it was before. For many of my destinations, I can depart with full tanks, fly to my destination, shoot an approach, miss it and fly home with reserves.

But the first time I flew the airplane after the installation was complete and signed off, I did slow flight and stalls to determine if the airplane’s low-speed characteristics had changed. After leak checks, I topped all the tanks and took off solo, heading for the practice area. I climbed to 3000 feet, cleared the area and flew level turns with the stall warner on for about five minutes. Then I pulled the power off and kept easing back on the yoke until the stall broke and the airplane fell off on a wing. I recovered, did one with some power and went home. My brief career as a test pilot was over. With the tip tanks installed, the airplane basically handled as it did before, and I was satisfied. But it just as easily could have gone pear shaped. I was, quite literally, the first to fly what was essentially an untested airplane.