RAH'er has forced landing

From Monday's FAA accident summary:

IDENTIFICATION
Regis#: 4449E Make/Model: EXP Description: EXP-
Date: 12/18/2004 Time: 1950

Event Type: Incident Highest Injury: None Mid Air: N Missing: N
Damage: None

LOCATION
City: LEESBURG State: FL Country: US

DESCRIPTION
ACFT MADE AN EMERGENCY LANDING NEAR A ROAD 15 MILES SOUTH OF LEESBURG, FL

N4449E is an "EZ" registered to a George Graham...RAH'er George Graham's
Mazda-powered Long-EZ, I believe. Congrats to George for not only coming
through with a whole skin, but for bringing off a off-field landing in a hot
homebuilt without damage.

Ron Wanttaja

A little update on George...
pasted from a list-serv regarding the Mazda rotary conversion that I
frequent... The problem wasnt the engine.. it was the peripherals.. and
the pasted bit below is from a maker of PSRU's who was uninvolved with
the accident airplane:


George Graham, one of the early aviation rotary adopters, isn't on the
list so though I'd pass along his latest. After 200+ hours, his second
Mazda manual transmission (2nd gear) PSRU stripped it's gears and he
dead sticked safely on a road about 10 miles from Leesburg Fl yesterday.
No damage to him or plane but he doesn't want to take a chance on the
transmission again. I'll be building him an RD-1A. He glided about 20
miles from an altitude of only 5000 ft with the prop freewheeling!

PASTE complete..

The glide distance has since been re-evaluated, but overall everyone is
glad it worked out ok.. and on a secondary personal note its refreshing
that the engine itself was not the point of failure

Dave

Ron Wanttaja wrote:
From Monday's FAA accident summary:

IDENTIFICATION
Regis#: 4449E Make/Model: EXP Description: EXP-
Date: 12/18/2004 Time: 1950

Event Type: Incident Highest Injury: None Mid Air: N Missing: N
Damage: None

LOCATION
City: LEESBURG State: FL Country: US

DESCRIPTION
ACFT MADE AN EMERGENCY LANDING NEAR A ROAD 15 MILES SOUTH OF LEESBURG, FL

N4449E is an "EZ" registered to a George Graham...RAH'er George Graham's
Mazda-powered Long-EZ, I believe. Congrats to George for not only coming
through with a whole skin, but for bringing off a off-field landing in a hot
homebuilt without damage.

Ron Wanttaja

On Tue, 21 Dec 2004 03:00:05 GMT, Dave S
wrote:

The glide distance has since been re-evaluated, but overall everyone is
glad it worked out ok.. and on a secondary personal note its refreshing
that the engine itself was not the point of failure

Dave

Dave, my feeling is that it does not matter that the engine did not
fail, the PSRU did and the result is the same: No engine and a forced
landging.

I wondered about using a transmission for a PSRU instead of a PSRU for
a PSRU. The problem with using a transmission is that the all the
gears except for fifth, are designed for light usage. In otherwords
they weren't designed to be used continuously with the engine pulling
50% or more power. George's transmission is not the first to fail
because of this.

Using the transmission for a PSRU is not necessarily a bad thing, but
the gears that will be used and the bearings that support the gears
may need to be re-evaluated.

Corky Scott

Corky Scott wrote:

On Tue, 21 Dec 2004 03:00:05 GMT, Dave S
wrote:


The glide distance has since been re-evaluated, but overall everyone is
glad it worked out ok.. and on a secondary personal note its refreshing
that the engine itself was not the point of failure

Dave


Dave, my feeling is that it does not matter that the engine did not
fail, the PSRU did and the result is the same: No engine and a forced
landging.

I wondered about using a transmission for a PSRU instead of a PSRU for
a PSRU. The problem with using a transmission is that the all the
gears except for fifth, are designed for light usage. In otherwords
they weren't designed to be used continuously with the engine pulling
50% or more power. George's transmission is not the first to fail
because of this.

Using the transmission for a PSRU is not necessarily a bad thing, but
the gears that will be used and the bearings that support the gears
may need to be re-evaluated.

I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.

It used to be that 4th gear in most four-speeds was 1:1 and this was
often accomplished by simply connecting the input and output shafts
directly with a collar. So, I suppose this could have been more rugged
as the gears were just along for the ride at that point. However, some
new transmissions have the 5th or 6th gear as a overdrive gear, and
occasionally even the 4th, and may not even have a 1:1 ratio. In these
designs, every speed is being driven through the gear set/layshaft.

If you have a design reference for transmissions being designed to not
handle full torque in anything but high gear, I'd be interested in
seeing it. Also, if you have a list of such transmissions that would be
interesting as well.

Matt

Matt Whiting wrote:



I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.

It used to be that 4th gear in most four-speeds was 1:1 and this was
often accomplished by simply connecting the input and output shafts
directly with a collar. So, I suppose this could have been more rugged
as the gears were just along for the ride at that point. However, some
new transmissions have the 5th or 6th gear as a overdrive gear, and
occasionally even the 4th, and may not even have a 1:1 ratio. In these
designs, every speed is being driven through the gear set/layshaft.

If you have a design reference for transmissions being designed to not
handle full torque in anything but high gear, I'd be interested in
seeing it. Also, if you have a list of such transmissions that would be
interesting as well.

Matt

I would think that if anything the lower gears would have to be be
beefier than the higher ones, at least on the output shaft. Torque
increases as rotational speed decreases, right? This is why axle shafts
tend to snap when starting a heavy load from a dead stop.
I just replaced fifth gear in my Nissan NX a month or two ago. It was
pretty much worn out, and not really beefy to begin with. You do spend
most of your time driving sitting in your highest gear so it will see
the most wear, but not necessarily the highest torque loads. All the
gears are equally wimpy, but the 1st and 2nd shifting collar is a little
longer and engages more teeth than the others. This seems to confirm
that 1st and 2nd are stronger gears than 4th or 5th.This car has the
smallest tranny I've ever worked on and one look inside would make you
REALLY glad you aren't flying behind it. Those gears are tiny, and
eyeball engineering would lead me to believe they aren't up to the job
of swinging a prop. Graham's two failures pretty much confirm this. I
can't imagine the mazda's gearbox is any beefier than this one. Flying
with one of these is 'experimental' all right.

Jason
Challenger-II

On Tue, 21 Dec 2004 11:46:46 -0500, Matt Whiting
wrote:

I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.

Matt, it isn't a matter of being strong enough to withstand occasional
pulls at full throttle, it's the continuous use that appears to be the
problem, and also that this may be a problem endemic to transmissions
being used as PSRU's.

My curse is that I read a LOT. One of the many articles I read a
number of years ago was about a builder trying to use a Honda Goldwing
engine for his airplane engine. This engine has an integral
transmission which he used as the PSRU. He used second or third gear
for his output gear and the transmission failed, like George's.

The reason for the failure, if I'm remembering this correctly, was
that the lower gears were not designed for continuous transmission of
power, at least not at the power levels required for flight. Whether
it was the width of the gears or the size of the bearings that
supported them, or even if there were bearings supporting the shaft, I
don't know. It could also have been a problem with prop loads on the
output shaft, not sure. But the transmission as a psru failed.

It could be the gears that failed, or it could be that the output
shaft could not stand up to the prop loads, don't know how George
supported the output shaft.

In any case, George should be congratulated for safely landing an
airplane with a decoupled prop that has one of the higher landing
speeds for light airplanes around. Putting down after a total loss of
thrust is never easy unless you practice frequently and even then you
always know it's just practice and a blown approach can be salvaged by
advancing power and trying again.

But the real thing is the real thing, and while some people flying
Long E-Z's manage to be at around 60 mph when touching down, most I've
heard of are faster than that to prevent the nose from pitching down
prematurely and uncontrollably.

Good job George.

Corky Scott

PS, I hope George posts here what failed in the transmission. It
would be illuminating.

Corky Scott wrote:
On Tue, 21 Dec 2004 03:00:05 GMT, Dave S


Dave, my feeling is that it does not matter that the engine did not
fail, the PSRU did and the result is the same: No engine and a forced
landging.

(snip)

Corky Scott

It sure matters to me. The mazda rotary is about the only auto
conversion that I have even given any serious thought to. I have one
assembled on a stand at the hangar waiting to be put on the airframe. We
are hoping to fly it to Osh 2005 (so we have a timetable to try and
meet, safety permitting) ANY power loss incident involving one concerns
me greatly since I am going to be one of the follow-on experimenters
behind the trailblazers. I'm using a commercially produced PSRU.. not a
transmission made into a PSRU... so yea.. it matters quite a bit to me
that the power failure wasnt in the engine itself, but one of the
peripherals.

So far, in the past 6 months, the list of Mazda engine casualties has
included 3 blown turbos (2 by one person), one of those blown turbo'd
engines ALSO had a shoddy rebuild by a local race shop that contributed
to power probs. There has been a blown oil cooler (fashioned from an a/c
evaperator core) resulting in a dead stick landing into Spencer
NOLF/Helicopter field and then this tranny failure. By and large, almost
all of the failure modes are being attributed to causes other than the
heart of the engine failing. And ALL of the failure modes involve either
substandard labor or the use of automotive accessories in a manner they
were originally never intended for. This is actually refreshing that the
engine itself is not the problem (no bad cranks, blown seals, etc)

The dead stick plane actually looks like its going to be flyable now
without a rebuild (pilot pulled power immediately when the oil cooler
blew, and when he tried to advance the throttle slightly, it stumbled
and died. Actually appears that it didnt seize or scorch the rings.

Dave

Corky Scott wrote:

On Tue, 21 Dec 2004 11:46:46 -0500, Matt Whiting
wrote:


I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.


Matt, it isn't a matter of being strong enough to withstand occasional
pulls at full throttle, it's the continuous use that appears to be the
problem, and also that this may be a problem endemic to transmissions
being used as PSRU's.

My curse is that I read a LOT. One of the many articles I read a
number of years ago was about a builder trying to use a Honda Goldwing
engine for his airplane engine. This engine has an integral
transmission which he used as the PSRU. He used second or third gear
for his output gear and the transmission failed, like George's.

That wouldn't be too surprising as airplanes require much greater
continuous power output than cars or motorcycles.


The reason for the failure, if I'm remembering this correctly, was
that the lower gears were not designed for continuous transmission of
power, at least not at the power levels required for flight. Whether
it was the width of the gears or the size of the bearings that
supported them, or even if there were bearings supporting the shaft, I
don't know. It could also have been a problem with prop loads on the
output shaft, not sure. But the transmission as a psru failed.

This is the part I don't buy as there is nothing different about the
lower gears than the higher gears. This is the part I think is a myth.
I believe that ANY gear selected in the GW transmission would have
failed under long-term high power output. I don't think this is an
issue preferential to the higher numerical ratio ("lower") gears.


It could be the gears that failed, or it could be that the output
shaft could not stand up to the prop loads, don't know how George
supported the output shaft.

In any case, George should be congratulated for safely landing an
airplane with a decoupled prop that has one of the higher landing
speeds for light airplanes around. Putting down after a total loss of
thrust is never easy unless you practice frequently and even then you
always know it's just practice and a blown approach can be salvaged by
advancing power and trying again.

But the real thing is the real thing, and while some people flying
Long E-Z's manage to be at around 60 mph when touching down, most I've
heard of are faster than that to prevent the nose from pitching down
prematurely and uncontrollably.

Absolutely. An E-Z would not be high on my list of airplanes to land
off-field.


PS, I hope George posts here what failed in the transmission. It
would be illuminating.

That it will.


Matt

On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
wrote:


The reason for the failure, if I'm remembering this correctly, was
that the lower gears were not designed for continuous transmission of
power, at least not at the power levels required for flight. Whether
it was the width of the gears or the size of the bearings that
supported them, or even if there were bearings supporting the shaft, I
don't know. It could also have been a problem with prop loads on the
output shaft, not sure. But the transmission as a psru failed.

It could be the gears that failed, or it could be that the output
shaft could not stand up to the prop loads, don't know how George
supported the output shaft.

In any case, George should be congratulated for safely landing an
airplane with a decoupled prop that has one of the higher landing
speeds for light airplanes around. Putting down after a total loss of
thrust is never easy unless you practice frequently and even then you
always know it's just practice and a blown approach can be salvaged by
advancing power and trying again.

But the real thing is the real thing, and while some people flying
Long E-Z's manage to be at around 60 mph when touching down, most I've
heard of are faster than that to prevent the nose from pitching down
prematurely and uncontrollably.

Good job George.

Corky Scott

PS, I hope George posts here what failed in the transmission. It
would be illuminating.



What really beats on the gears, and what automotive use does not
experience, is the harmonics. Harmonics load the gears in BOTH
directions, with in the order of 10 times the steady state torque.

That tends to shear off teeth!!!

wrote in message
...
On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
wrote:

What really beats on the gears, and what automotive use does not
experience, is the harmonics. Harmonics load the gears in BOTH
directions, with in the order of 10 times the steady state torque.

That tends to shear off teeth!!!

Torsional resonance has been a problem with many PSRU units, over many
years, including units from big manufacturers of certificated equipment. If
resonance is not carefully studied and tested for, you are almost guaranteed
to have a problem.

Does your car have a harmonic balancer on the crankshaft? Why do you
suppose it is there?

I work with big trucks and we have a problem there with torsional resonance
from the power pulses of the big diesels, especially at high torque and low
rpm (sound familiar?). If, for instance, one removes a clutch with a
dampened disc and replaces it with a clutch with a solid disc, the
transmission input shaft splines might shear -- or the transmission gears --
or the differential gears. It is almost impossible to convince a customer
that his cheap clutch replacement caused his rear axle to fail, but it did!
Truck component manufacturers put a lot of effort into finding and
eliminating resonance. I hope your PSRU designer did too...

Also note that changing ANY component in the drive train can mess up the
torsional dynamics, which is a bad thing for a bunch of experimenter
homebuilders. Even cutting down a metal prop a couple inches. Why do you
suppose that the FAA will allow a 25 hour test period with a certified
propeller/engine combination, but 40 hours without?
Resonance is a big reason.
-Bob