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Excerpt from Steve Young's mail:
"When I got close to home I turned on the
avionics and the master switch on to see if the gear would go down. I felt
the right one lock down and then everthing when dead.
....
I opened the dump valve and pulled the curcuit
breaker at this time. I went through the procedures with no luck. I was thinking
at the time that I needed to stay at the 120 knots so I would take the doors
off. Hind sight is always 20/20 and I should have been alot more aggressive. I
wish now, I would have climbed higher and build more speed prior to the yawing
since I lost the gear door anyway on landing."
For the last several years I've been flying a
Commander 112 which has a gear system nearly identical to the Legacy; i.e. an
electric motor drives a hydraulic pump which operates the landing gear.
Just like the Legacy, and as far as I know the 320/360, the gear is held
up by hydraulic pressure and emergency extension uses a simple dump valve
to relieve pressure in the gear hydraulic cylinders.
Gravity starts the gear down and springs, rather than gas struts, finishes
the gear extension and locks the over-center links in place. I've had
to use the dump valve twice in flight. The first time the gear failed to
extend when attempting to land at an airport about 30 min from my home
base. I flew back home, slowed to about 90 kts before entering
downwind (normal approach for the 112 is 80 KIAS) and activated the dump
valve. The gear came down just like when it was on jacks during
the annual inspection (you do check the emergency extension at least yearly,
right?), I got 3 green and landed with no problems. After getting back to
the hangar we put the plane on jacks and, of course, the gear worked just fine;
could not get it to fail. But like the old
saying goes, problems that go away by themselves come back by themselves.
About 100 flying hours later the gear failed to
extend, again. This time I didn't slow down as much before hitting the
dump valve. (Max gear extension speed on the 112 is 130 KIAS.) Like
before the mains came down immediately. (They're pretty heavy and actually
free fall faster than the normal extension.) The nose gear takes a little
longer, but this time it didn't come all the way down; no green nose gear
light. I tried pulling a couple of G's but no luck. (My wife was
with me so I didn't want to pull too hard.) But as I slowed
below 100 KIAS and started extending the flaps the nose gear locked in
place. At this point I started breathing again. Once again the
landing was uneventful, but this time back in the hangar and on the jacks the
gear motor refused to run at all.
After replacing the motor/pump assembly we ran
some extension experiments and came to two conclusions. First, the
main gear does not appear to be sensitive to airspeed during an emergency
extension, but the nose gear does. Slower is
better. Unless you've lost the engine you can always speed up and yaw
if you need more force on the main gear doors to lock the mains in place, but
let the nose gear lock first. Second, emergency extension worked
better, i.e. was more positive, when we started with the gear fully
retracted. Starting a normal gear extension then killing power with the
gear partially extended, then hitting the dump valve didn't always result in
positive gear extension, even when sitting on jacks. We also ended up
replacing the nose gear springs and got more positive extension on the
nose gear, so check your gas struts regularly.
Granted this was all on a Commander 112, not a
Lancair, but due to the similar gear systems I think the rules I've set for
myself for emergency extension on the 112 may also work on the
Legacy and 320/360: 1) Slow down as much as possible before activating the
dump valve. This makes it easier to extend the nose gear. 2) If you
are having electrical problems don't even try to do a normal extension.
Leave the gear fully retracted then pull the gear breaker and use the dump
vavle.
Of course trying this out at a safe altitude in
your own plane is highly recommended. Your mileage may vary.
Tom Gourley
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