Jetwhine

Aviation buzz and bold opinion

Flight Testing

Boeing Flight Test Engineers Get Creative

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Test pilots and flight test engineers are an amazing and interesting group of people. But they are deadly serious about their work because focus and attention to detail preserves not only their lives, but those who go aloft in the aircraft they are testing. Some aspects of certification flight tests can be eternally boring.  Tests for function and reliability and extended ops, or ETOPS, for example, can involve flights lasting 15 hours or more.

image/photoMy only experience with long duration flight was the 17-hour confinement, not counting the Alaskan fuel stop,  in a stretch DC-8 with max density seating. It carried me, and the hefty Air Force and Army sergeants on my left and right, to Asia in 1975. Aside from better, more comfortable seats, I can’t imagine the willpower it takes to focus on precisely flying the data points and monitoring the data.

Then I found Randy’s Journal, that’s Randy Tinseth, VP of marketing for Boeing Commercial Airplane. How much fun would it be to use a 747-8 Freighter to scribe on a FlightAware map a “747” that covered 15 states stretching east from Washington to Wisconsin and south to California, New Mexico, and Texas? From Paine Field, the 17-hour function and reliability test flight had to go somewhere, so why not have fun with it?

Not to be outdone, the flight test crew of the 747-8 Intercontinental had an 18-hour ETOPS test flight to plan, and they figured it would be just enough time to fly over every one of the lower 48 states. This time they tracked their route on a Google Earth map. The test “helps determine how far the airplane will be able to travel from a suitable diversion airport,” Randy wrote, adding, “After the Intercontinental returned to Everett, it still had more than two and a half hours worth of fuel left.”

And to fill the downtime on that flight, one of the flight test analysis engineers walked a half-marathon. “In 15 minute increments, she circled a 225 foot loop around the aft section of the airplane—310 times.”  Oh, what I would not have given for that opportunity back in the day. — Scott Spangler

Monnett Finally Lives His SubSonex Dreams

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John Monnett has been dreaming about a homebuilt jet since the 1980s, so one can only imagine the barely controlled eagerness that filled him with the first flight of the SubSonex. And one can only imagine the internal debate between making that flight himself or turning it over to someone like, Bob Carleton, right, who has the necessary flight experience and, perhaps more important, experience with the PBS TJ-100 engine, which powers Carleton’s Super Salto Jet Sailplane.

But Monnett is the consummate professional, and safety always trumps decades of jet fueled desire. Carlton made the first flight on August 10, and explored the flight envelop from stalls to more than 200 knots true airspeed. Monnett climbed into the SubSonex for his first flight on August 25, and he has built his experience and confidence in the design since then. One happy revelation is that the TJ-100’s fuel economy has been better than expected. As the testing program moves forward, the Hornets’ Nest R&D team has replaced the nose wheel with a retractable unit to improve yaw stability in cruise (and an increase in cruise speed, too!).

A design study for the second SubSonex prototype is underway. Its goals are a larger cockpit, a sleeker nose, and (maybe) a removable wing for easier transport and storage. But the real question is this: As it flies now, how does the SubSonex compare to decades of jet propelled daydreams?

“Doesn’t everyone who has dreamed want one of these? Flying the jet is a hoot! It is like flying a sailplane only a lot faster,” John said. “So far, it has exceeded my expectations. It is, remarkably, very stable and comfortable at lower speeds and gets even better as you ramp up. Looking at the stoic cockpit videos doesn’t give the impression I am having a good time. I can’t think of any other aircraft I’ve flown that is this much fun! Beneath that old man’s skin is a kid again!”