The twenty four UC-1 Twin Bees made by STOL Aircraft, Inc.during the 1980’s occupy a unique place in aviation history. They were the last multi-engine flying boats produced in the United States. Through a quirk of fate, mine, hull #23, is the newest of the type still flying and, as such, is a unique historical artifact. The FAA Aircraft Register lists thirteen UC-1’s. NTSB accident reports show that three of these were destroyed in crashes. A correspondent tells me he has the engines off a fourth. That reduces the total to no more than nine. The Twin Bee indeed is indeed an endangered species.
When Joseph Gigante and his colleagues of United Consultants undertook to design andproduce a multi-engine amphibious flying boat, they decided not to go through rigors of obtaining a new type certificate, but rather to modify the existing Republic RC-3. They removed the 215 horsepower Franklin pusher engine, added two and a half feet to each wingtip, spliced a four foot section into the fuselage just aft of the cockpit and put two 180 horsepower Lycoming fuel injected IO-360 engines with constant speed, full feathering Hartzell propellers atop the wings.
The result was funny looking and had serious center of gravity problems. It still looks funny. The center of gravity problems were solved by increasing the 75 gallon main fuel tank to 85 gallons and adding a 16 gallon fuel tank near the tail to or from which fuel can be transferred in flight to adjust the center of gravity.
How does it fly? Over the past half century, I’ve learned that funny looking planes fly funny. That said, let’s go for a ride.
You can get into very serious trouble just by not properly securing the doors. The pilotand copilot doors are trapezoids measuring three feet by three feet that open to the rear. As if the fact that an opening door would swing back and slam into the fuselage were not enough, an errant door will also swing into the propeller arc and send the plane out of control. There are two extra fasteners on each door, a red flashing light if the doors are not locked and a steady yellow light if they are. What me worry?
Directional control on the ground is a challenge. The vertical stabilizer is a huge flat thing sticking twelve feet into the air. The tail wheel swivels. The brakes fade when they get hot. A quartering tailwind while taxiing on a narrow taxiway has embarrassed the best of us. Directional control on takeoff and landing is simplified by a locking tailwheel. Fear not, should you forget to lock it, you’ll know within seconds of advancing the power. Land with it unlocked and you stand a good chance of producing a 3,000 pound lump of crumpled sheet aluminum.
A light twin (two wing mounted reciprocating engines and weighing less than 6,000 lbs.) is not required to maintain altitude on one engine. The book says a Twin Bee will climb at about 200 feet per minute at gross with one feathered. However, NTSB records show at least one instance where it couldn’t. If someone shows you an ATP gotten in a Twin Bee and all the events were honestly done, you stand in the presence of a person to whom Chuck Yeager would demur.
During trimmed, steady-state cruise, every once in a while the Twin Bee will make up its mind to go wandering off. It suffers from phugoid, or long term, oscillation. Try as one might, you can’t trim it out. This doesn’t hurt anything or present a danger. It’s annoying. During a five hour flight there will be several unexpected minor “attitude excursions.”
Landing is a piece of cake with the caveat, “Thou Shalt Not Get Slow!” With no flaps, the entire wing stalls at the same time. With flaps down, the tips stall first, but not by much. If you’re slow with low power, the Twin Bee can suddenly drop out from under you. If you hit too hard bulkheads collapse, rivet lines rupture and the hull floods. Hit nose hit first and the part of Bernoulli’s Law speaking to the greatest force being perpendicular to the greatest curvature comes into play and over you go. NTSB records tell of an accident in which a student attempting a no-flap landing came to grief. The feds don’t speculate. However, my reading of the report suggests the plane stalled, dropped and flipped.
Flying boats failed as airliners because loading and unloading on the water is inconvenient. The wingtip float keeps you from siding up to a dock. Nose-to docking requires a crew, spring lines and bumpers. Loading and unloading from a lighter at a mooring usually degenerates into a gymnastics exhibition. The most convenient way to load and unload a flying boat is on solid ground, and even that is not always graceful. If you must fly a boat, you have to accept that loading and unloading is not a single person activity, and it usually requires special equipment.
Despite its looks, nasty habits and glacier slow cruise, I love owning and flying a piece of history.
SEABEE HOMEJanuary 28, 2003