BD-5 crash in Australia

"Stealth Pilot" wrote ...
holding the aircraft low to the ground and accelerating in level
flight does two things.
it gets you to a safer climbout speed faster.
if the engine does quit you avoid the spine destroying thump into the
ground.

That wouldn't help on the BD-5. The BD-5 is a very poorly designed airplane
and your friend had the quintessential BD-5 accident. There have been
several accidents and deaths along these lines. These usually happen early
in the testing program. The pilot is new to the airplane and the airplane
has an engine cooling problem. That's inherent in the design and the
designer never solved the problem. The pilot taxis out to the runway as the
engine compartment overheats causing a new problem in the fuel system. Once
on the runway, the pilot applies power pouring more heat into the
compartment. The engine lasts long enough to get in the air and the engine
quits. On the BD-5 all the big weights are down low. The fuel is on the
bottom of the airplane, the pilots center of gravity is low and the engine
is fairly low. That makes the airplane center of gravity low but the thrust
line is up at that top of the airplane. The high thrust line wants to push
the nose down so the pilot has to compensate with aft stick. Now the engine
stops. The clutch disengages the engine and the prop and the prop sits out
there windmilling. A windmilling prop is like a parachute, now trying to
pull the nose up. The airplane controls are commanding nose up already so,
between the controls and the prop, up the nose goes. If the pilot's not
spring loaded to shove the nose down, it won't go down. It will pitch up
violently and the g-loading will go up. This causes the wing skins to
wrinkle and that destroys the wing aerodynamics. The airplane does a high
speed stall and, without altitude to recover, it slams into the runway. If
the pilot's lucky. If not, the airplane stalls asymmetrically and
half-snaps to the inverted position and slams into the runway with generally
fatal results. Your friend was lucky.

Rich

In a previous article, "Richard Isakson" said:
bottom of the airplane, the pilots center of gravity is low and the engine
is fairly low. That makes the airplane center of gravity low but the thrust
line is up at that top of the airplane. The high thrust line wants to push
the nose down so the pilot has to compensate with aft stick. Now the engine
stops. The clutch disengages the engine and the prop and the prop sits out
there windmilling. A windmilling prop is like a parachute, now trying to
pull the nose up. The airplane controls are commanding nose up already so,
between the controls and the prop, up the nose goes. If the pilot's not
spring loaded to shove the nose down, it won't go down. It will pitch up
violently and the g-loading will go up. This causes the wing skins to

The Lake Amphibian, and probably most boat-hull type amphibs, have that
same problem. The weight and drag are down near the hull, and the thrust
comes from that engine mounted on a pylon above.


--
Paul Tomblin http://blog.xcski.com/
If I have pinged farther than others, it is because I routed upon
the T3s of giants.
-- Greg Andrews

On Thu, 24 May 2007 11:13:47 -0700, "Richard Isakson"
wrote:

"Stealth Pilot" wrote ...
holding the aircraft low to the ground and accelerating in level
flight does two things.
it gets you to a safer climbout speed faster.
if the engine does quit you avoid the spine destroying thump into the
ground.

That wouldn't help on the BD-5. The BD-5 is a very poorly designed airplane
and your friend had the quintessential BD-5 accident. There have been
several accidents and deaths along these lines. These usually happen early
in the testing program. The pilot is new to the airplane and the airplane
has an engine cooling problem. That's inherent in the design and the
designer never solved the problem. The pilot taxis out to the runway as the
engine compartment overheats causing a new problem in the fuel system. Once
on the runway, the pilot applies power pouring more heat into the
compartment. The engine lasts long enough to get in the air and the engine
quits. On the BD-5 all the big weights are down low. The fuel is on the
bottom of the airplane, the pilots center of gravity is low and the engine
is fairly low. That makes the airplane center of gravity low but the thrust
line is up at that top of the airplane. The high thrust line wants to push
the nose down so the pilot has to compensate with aft stick. Now the engine
stops. The clutch disengages the engine and the prop and the prop sits out
there windmilling. A windmilling prop is like a parachute, now trying to
pull the nose up. The airplane controls are commanding nose up already so,
between the controls and the prop, up the nose goes. If the pilot's not
spring loaded to shove the nose down, it won't go down. It will pitch up
violently and the g-loading will go up. This causes the wing skins to
wrinkle and that destroys the wing aerodynamics. The airplane does a high
speed stall and, without altitude to recover, it slams into the runway. If
the pilot's lucky. If not, the airplane stalls asymmetrically and
half-snaps to the inverted position and slams into the runway with generally
fatal results. Your friend was lucky.

Rich


the differences between these aeroplanes and the originals are subtle
and many. I just have not had the opportunity to discuss the comments
with the two guys. soon hopefully.
Stealth Pilot