Lancair Legacy Design Flaw?

Ron Wanttaja wrote:
Gregory Hall wrote:

This is the safest homebuilt IMO.(VariEze ). The canard makes it
foolproof.

If that were the case, the Velocity would have a better safety record
than the Lancair family. Based on my statistics from 1999 through
2006, it doesn't... the Velocity has about a 20% higher accident rate.
In fact, the Velocity has a rate almost three TIMES higher that of
the RV fleet. Which isn't doesn't use canards, either.

The difference in fleet size does affect the statistics, of course....

Still, it might be reasonably argued that when a Lancair aircraft is
involved in an accident, it has a higher probability of yielding fatalities
than other aircraft. Consider:

I did a simple NTSB search[1] (from 1-1-1962 to present) using "Lancair" in
the Make/Model field and it appears that out of 151 matching accident
records, 70 involved fatalities. Is that 46% value close to typical or is
it, as I suspect, on the high side[2]?

When I entered "Lancair Legacy" in the Make/Model field out of 11 matching
records 7 of them involved fatalities. The 63% value seems even more
unusual. But the accident count is a small number, so may be misleading.

(Yes - I know the entered keywords may not find all relevant records, but
I'm assuming the missed records have similar proportions of fatal to total
accidents as the matching records.)

If the fractions are not typical, could it be because Lancair
incidents/non-fatal "accidents" aren't reported as often as for other
makes? Or is the aircraft dangerously unforgiving such that an accident has
a high likelyhood of leading to fatalities? Or is there another reason for
the differences?

[1] http://www.ntsb.gov/ntsb/query.asp

[2] By comparison, from 1-1-1962 to present and entering "701" in
Make/Model and setting "Amateur Built" to Yes yielded 27 records for the
Zenith CH 701 aircraft. Only one of those records involved fatalities. Only
4% of accidents involved fatalities.

Ron Wanttaja wrote:
Gregory Hall wrote:

This is the safest homebuilt IMO.(VariEze ). The canard makes it
foolproof.

If that were the case, the Velocity would have a better safety record
than the Lancair family. Based on my statistics from 1999 through 2006,
it doesn't... the Velocity has about a 20% higher accident rate. In
fact, the Velocity has a rate almost three TIMES higher that of the RV
fleet. Which isn't doesn't use canards, either.

The difference in fleet size does affect the statistics, of course....

Ron Wanttaja

I have long wondered if the canard fliers who have accidents are
assuming "canards are safer" and get careless.

Dan, U.S. Air Force, retired

(Apologies to Jim; I'm snipping quite a bit of his excellent posting and
quoting him a bit out of order.)

Jim Logajan wrote:

Still, it might be reasonably argued that when a Lancair aircraft is
involved in an accident, it has a higher probability of yielding fatalities
than other aircraft. Consider:

[Snip]

When I entered "Lancair Legacy" in the Make/Model field out of 11 matching
records 7 of them involved fatalities. The 63% value seems even more
unusual. But the accident count is a small number, so may be misleading.

[Snip]

[2] By comparison, from 1-1-1962 to present and entering "701" in
Make/Model and setting "Amateur Built" to Yes yielded 27 records for
the Zenith CH 701 aircraft. Only one of those records involved
fatalities. Only 4% of accidents involved fatalities.

The problem is separating the "This is due to the aircraft being a
Lancair" issues from the "This is a high-performance aircraft" ones.
The survivability of an accident is dependent on a huge number of
factors, but a big one is the speed involved. Energy is equal to the
mass times the velocity squared.

Obviously a Zenair undershooting and hitting the trees at 35 knots is
going to be MUCH more survivable than a Lancair hitting the same trees
at 80. The fatality rate *might* be the same, if a Zenair hit the trees
at 80, but there's no way to make a fair comparison.

One can certainly argue that the Zenair's ability to slow down makes it
a safer airplane. But then, if one wants performance at the HIGH end,
one usually has to give up somewhat at the low-end range. TANSTAAFL.

A better comparison would be that of planes of similar high-end
performance... Lancairs, Glasairs, and RV-8s, for instance.

I took a quick look at my database (which covers Jan 1999 through Dec.
2006). The results were practically a wash...36% of two-seat Lancair
accidents were fatal, vs. about 40% of Glasairs. RV-8s were right
between at 38%.

Digging a little more, RV-6s were at about 26%, RANS (all models) were
34%, Avid Flyers (all models) were 10%, and Zenairs (all models) were
22%. For anyone keeping score, about 30% of first-flight accidents kill
the pilot.

(Yes - I know the entered keywords may not find all relevant records, but
I'm assuming the missed records have similar proportions of fatal to total
accidents as the matching records.)

Welcome to my world. :-)

If the fractions are not typical, could it be because Lancair
incidents/non-fatal "accidents" aren't reported as often as for other
makes?

I would suspect the opposite. Lancairs are expensive airplanes. Bet
the vast majority of the owners have insurance, and the insurer probably
won't pay off if the accident isn't reported to the FAA. They're also
complex aircraft, which means it's tougher to just pull up with a
trailer and haul off the wreckage before the FAA gets there. Been known
to happen, locally...

Ron Wanttaja

In article ,
"Morgans" wrote:

"Steve Hix" wrote
Like Mignet and his Pou-du-Ciel (Flying Flea).

Everything going swimmingly, unless you manage to somehow get it
inverted.

At which point it becomes so stable that it would stooge about until it
ran out of fuel, no way to bring it upright again.

How about half of an outside loop?

That was *if* you were lucky, having enough altitude to complete the
half outside loop before hitting the ground.

It was a problem involving interference between the two tandem wings of
the Flea. (The only controls available in the original Fleas were pitch,
controlled by tipping the front wing up or down, and rudder, which
controlled roll through a lot of dihedral inducing yaw-roll couple. They
were not very good at handling any crosswind component on landing, but
most were flown off large open fields, letting the pilot operate
directly into the wind.)

Suppose the pilot pushed the stick forward to gain speed. As the speed
built, up the rear wing, operating at a greater effective angle of
attack (being fed air from the front wing) would gain lift and pitch the
aircraft's nose further down.

The pilot's normal reaction would be to pull back on the stick, which
increased the front wing's angle of attack by lowering the trailing edge
of the wing.

Because the trailing edge of the front wing was close to the leading
edge of the rear wing, the front wing's downwash accelerated the air
over the rear wing increasing its lift and thus increasing pitch-down,
resulting in flight directly into the ground if you had insufficient
altitude.

If you had enough altitude, it would fly a half outside loop, and at
that point become so stable that there was no recovery from the inverted
flight.

Eventually, the design was tweaked to get around the problem, but not
all examples of the Flying Flea were updated.

On Thu, 30 Oct 2008 19:38:03 -0700, Ron Wanttaja wrote:

Gregory Hall wrote:

This is the safest homebuilt IMO.(VariEze ). The canard makes it foolproof.

If that were the case, the Velocity would have a better safety record
than the Lancair family. Based on my statistics from 1999 through 2006,
it doesn't... the Velocity has about a 20% higher accident rate. In
fact, the Velocity has a rate almost three TIMES higher that of the RV
fleet. Which isn't doesn't use canards, either.

The difference in fleet size does affect the statistics, of course....

Ron Wanttaja

Ron, do you judge from this that the Velocity (or the pusher/canards in
general) have basic design issues (such as the Lancair's low speed
regime history)?

"Steve Hix" wrote in message
...
In article ,
"Gregory Hall" wrote:

France? I don't live in France. I built and used to fly a Rotec Rally 2B
many years ago. It was a tail dragger with a high wing and the motor was
mounted atop the win[g] with a pusher prop.

When I got it trimmed out correctly at cruise speeds I could lean forward
in
the seat to nose it down and lean back in the seat to nose it up.

Sort of like a Taylorcraft or Cessna 140 or similar small aircraft.

Even as
well-balanced as it was at about half throttle, when the engine quit it
would pitch up immediately and drastically because the high engine
placement

... Placed the thrust line enough above the center of drag that adding
power caused a downward pitch moment, and reducing power resulted in a
upward pitch.

and pusher prop had enough leverage so that the proper trim at the tail
counteracted the nose down force of the engine and prop.

Which is what the horizontal stab/stabilator is for.

If you didn't
immediately push the stick way forward when the engine quit it was a
matter
of seconds before it would nose up fast and stall and then you would have
no
control at all from the stick until it fell for a while and the nose
dropped
(thank god for that) so you could gain speed provided you had enough
altitude to get control of it again. But it didn't glide too well being a
single surface wing with wire bracing. Perhaps 2:1 glide ratio. But it
was
easy to land with no power but you had to come in hot and steep and at
the
last second pull back on the stick and flare it.

It looks to me like the Legacy would act pretty much the same if the
engine
quit.

Except for the Legacy not incorporating those design elements that
result in the pitch/power response of the Rotec Rally. The Rally needs a
lot of upward pitch dialed in for level cruise (which ought to be
contributing a lot of drag as an added bonus), giving you some nasty
response to losing power.

In particular, both thrust and drag components in the Legacy are much
closer in alignment, resulting in much less pitch change when power
changes.

The two aircraft behave very differently in many aspects, and the Legacy
not much at all as you've asserted.


Thanks guys. I think I understand the differences now. The part about the
forces being in better alignment makes sense to me and pusher vs. puller.
I'll have to retract my ill-conceived statements about the Legacy. By bad!

--
Gregory Hall

Dan schreef:

When someone invents something foolproof someone else invents a better
fool.

Think I'll use that for my e-mail signature for a while. Thank you!

In article ,
cavelamb himself wrote:

Alan Baker wrote:

Anyone who thinks an aircraft can be made "foolproof" is a fool who
shouldn't be flying.


You won this round, Alan!

Thanks, I guess. But I prefer to win against an opponent who's a little
tougher than that...

:-)

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

In article ,
"Gregory Hall" wrote:

"Vaughn Simon" wrote in message
...

"Gregory Hall" wrote in message
...


It looks too much like an irresponsible, hot rod, stunt plane to me.

Well, you sucked me in at first, so on a troll scale of zero-to-10 you
rate at least a five. How are things in France?

Vaughn


France? I don't live in France. I built and used to fly a Rotec Rally 2B
many years ago. It was a tail dragger with a high wing and the motor was
mounted atop the wind with a pusher prop.

When I got it trimmed out correctly at cruise speeds I could lean forward in
the seat to nose it down and lean back in the seat to nose it up. Even as
well-balanced as it was at about half throttle, when the engine quit it
would pitch up immediately and drastically because the high engine placement
and pusher prop had enough leverage so that the proper trim at the tail
counteracted the nose down force of the engine and prop. If you didn't
immediately push the stick way forward when the engine quit it was a matter
of seconds before it would nose up fast and stall and then you would have no
control at all from the stick until it fell for a while and the nose dropped
(thank god for that) so you could gain speed provided you had enough
altitude to get control of it again. But it didn't glide too well being a
single surface wing with wire bracing. Perhaps 2:1 glide ratio. But it was
easy to land with no power but you had to come in hot and steep and at the
last second pull back on the stick and flare it.

It looks to me like the Legacy would act pretty much the same if the engine
quit.

Greg,

What was happening to you was not caused by the *weight* of the engine,
but the change from higher than CoM thrust creating a pitch down torque,
to higher than CoM drag creating a pitch up torque.

Congratulations: you've just rediscovered one disadvantage of having a
thrust line that doesn't go through the centre of mass.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

In article
,
BobR wrote:

On Oct 30, 5:12*pm, "Gregory Hall" wrote:
"Vaughn Simon" wrote in message

...



"Gregory Hall" wrote in message
...

It looks too much like an irresponsible, hot rod, stunt plane to me.

* Well, you sucked me in at first, so on a troll scale of zero-to-10 you
rate at least a five. *How are things in France?

Vaughn

France? *I don't live in France. I built and used to fly a Rotec Rally 2B
many years ago. It was a tail dragger with a high wing and the motor was
mounted atop the wind with a pusher prop.

When I got it trimmed out correctly at cruise speeds I could lean forward in
the seat to nose it down and lean back in the seat to nose it up. Even as
well-balanced as it was at about half throttle, when the engine quit it
would pitch up immediately and drastically because the high engine placement
and pusher prop had enough leverage so that the proper trim at the tail
counteracted the nose down force of the engine and prop. If you didn't
immediately push the stick way forward when the engine quit it was a matter
of seconds before it would nose up fast and stall and then you would have no
control at all from the stick until it fell for a while and the nose dropped
(thank god for that) so you could gain speed provided you had enough
altitude to get control of it again. But it didn't glide too well being a
single surface wing with wire bracing. Perhaps 2:1 glide ratio. But it was
easy to land with no power but you had to come in hot and steep and at the
last second pull back on the stick and flare it.

It looks to me like the Legacy would act pretty much the same if the engine
quit.

--
Gregory Hall

Oh for gawd sake, you are talking about two totally different designs
and the aerodynamics of the two are totally different. The Lancair is
NOT a pusher and the engine is mounted forward of the CG instead of on
top of it. When the engine quits it will not pitch upward. The plane
you flew had the engine well above the center of gravity with a pusher
prop and as a result produced a force that pushed the nose of the
aircraft down. The two planes would not act pretty much the same at
all. The weight of the engine on the Legacy is forward of the CG and
as a result always pulling the nose of the plane down. The counter to
the nose down is the horizontal stabilizer and the elevator. Look at
the angle of incedence on the Horizontal Stabilizer and you will find
a slight downward angle, not an upward angle as is common on the
wing. This counteracts the force from the weight of the engine. An
engine out condition will not have a significant effect on pitch until
the airspeed changes and that will result in a nose down, not nose up
pull.

The one thing not quite right is that there is no important difference
between tractor vs. pusher configurations with respect to directional
stability.

Like some of the early rocket designers (e.g. Goddard), you are falling
into the fallacy that somehow pulling is more stable than pushing. This
is not so.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg