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Good concept Mark, the devil is in the details. My
incident, which happened on the ground, would be a Pucker factor of 1 --
however, if it had happened in the air (anywhere), it would have resulted in an
immediate forced landing, and probably a total rebuild of the engine, with a PF
of 4. It was 'sudden', and 'impressive' with the coolant dump.
SO, a key factor of your table is some narrative of
the 'incidents' impact on flight capabilities of the event.
Bill Schertz
KIS Cruiser #4045
N343BS
----- Original Message -----
Sent: Monday, April 13, 2009 4:11
PM
Subject: [FlyRotary] Re: forced
landings
Dave,
You're definitely in tune with the intent of the database. And I'm
just trying to keep it managable. I will go ahead and include items
discovered during preflight or maintenance which in all probability would
have resulted in an in-flight failure. Those will get a
pucker factor (PF) rating of 1. An example would be Ed's oil pump
failure due to a missing woodruff key.
Incidents that happened in flight that resulted in loss
of power, but continued flight was possible, will receive
a PF rating of 2. Such as a turbo hose blowing off.
Incidents that happened in the air that resulted in a precautionary
landing will be rated a PF 3.
Incidents which happened in the air which necessitated a forced
landing (on or off field) will get a PR of 4.
And finally, incidents which resulted in a crash and/or fatality will be
rated PF 5.
So, when reporting failures, please provide enough information for me to
determine the proper PF rating.
Thanks,
Mark
On Mon, Apr 13, 2009 at 3:47 PM, David Leonard <wdleonard@gmail.com>
wrote:
Mark,
Thanks for putting together this database. I agree with you and
Al G. that we should keep it to issues with the engine and it's
systems. But I also agree with John and Al W. that we should somewhere
include things that probably would have caused an in-flight failure,
especially when found on pre-flight, run-up or take off roll. That is
good stuff. Not the idiot-pilot-owner stuff like forgetting to attach
the return fuel line, but the alternator bracket and PSRU issues etc - that
could really help someone.
Similarly, just because it is in flight does not make it
newsworthy. Like the intake hose blow offs that John and I have both
experienced. Sure, something happened and you are damn sure going to
return to the airport and check it out even though you are pretty sure you
know what happened and it will not affect the safety of flight. OOps,
didn't tighten that hose tight enough.
In other words, I think Johns incident #1 is far more significant than
incident #4.
Maybe to clarify:
#1 caused actual damage to the engine AND he NEEDED to land soon
because of oil loss. Power produced was less than normally aspirated
power. This is an interesting mechanical possibility (that a turbine
blade somehow got BACK into the engine to bust the apex seal) and something
important to consider when designing a turbo install.
#4 caused only a reduction to normally aspirated power and a
skipped heart beat or two. No damage, no real need to land other than
as a precaution. No design flaw or mechanical issue - just an
underestimation on how tight to make the hose clamp. (and believe me, they
have to be very tight if there is no bead under the hose.) --
David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.nethttp://RotaryRoster.netOn Mon, Apr 13, 2009 at 6:16 AM, Mark Steitle <msteitle@gmail.com> wrote:
Dave,
I have decided to take Al's suggestion and limit the
criteria for the spreadsheet to basically include any in-flight system
failure which interrupts the planned flight and results in a premature
landing. Based on this, I will add #3 & #4 as well as the
one resulting from a ruptured coolant hose.
Mark S.
On Mon, Apr 13, 2009 at 7:55 AM, David Leonard
<wdleonard@gmail.com> wrote:
Mark, And did you get these? Added by me and John Slade under
the wrong thread title:
On Sun, Apr 12, 2009 at 5:15 PM, John Slade <jslade@canardaviation.com> wrote:
Here's a few for the list, Mark,
1. Stock turbo bearings collapsed
& took out apex seal. Flew home at reduced power.
2.
Fuel filer (sinstered bronze) looked clean but was restricting fuel
flow. Flew home on other tank.
3. Bad / intermittent
contact on ignition timing sensor made engine run rough. Landed normally
and repaired.
4. Turbo hose blew off on take-off. Returned
to land at reduced power.
John
------
Been
there, done that. (the blown-off intake hose)
Also:
I have burned out 2 turbos. The first caused
precautionary/urgent landing at an airport pending shutting off fuel
flow to the turbo. The second, I flipped a turbo oil shut off
switch and flew 1000NM to get home.
Had a fuel pump die in flight, switched to the other and kept
flying.(soft failure)
I had a bad injector enable switch causing rough running during
some phase one flying (after major change)... landed
normally
Forgot to re-connect fuel return line in engine bay after doing
some work. dumped a couple gallons of fuel onto the running engine
until I smelled gas and shut down the engine.. (never left the parking
space - but it could have been really bad.
Cracked alternator mount bracket found on pre-flight during
phase one testing. Would have lost cooling and alternator if it
happened now.
PSRU sun gear pin broke from a backfire during run-up.
Was able to taxi back but would not have been able to
fly.
This is good - broke a coolant line in flight and
smelled coolant... landed at nearby airport and taxied up to
restaurant with steam spewing out of the cowl. Me and my buddy
calmly walked into the restaurant and had breakfast. Afterward, we
borrowed some tools and fixed the coolant line. Went back into the
restaurant to ask for 2 pitchers of water to put in our plane.
Continued ski trip to Mammoth. The end.
On Sun, Apr 12, 2009 at 2:03 PM, Mark Steitle
<msteitle@gmail.com> wrote:
Thanks
Bill,
With the addition of Bill's exciting adventure, and one
of my own, we're up to 18 incidents in the database. These last
two, along with Ed's brake fire, and an oil coolant rupture, totals
four incidents involving fires during ground operations.
Hopefully, everyone carries at least one fire extinguisher in their
airplane.
Mark S.
On Sun, Apr 12, 2009 at 2:56 PM, Bill Schertz
<wschertz@comcast.net> wrote:
One other thing to watch out for --
This occurred during ground testing, but if it had happened in the
air it would have been a forced landing.
From my post of Feb.
8
Well, I haven't heard of this happening
before -- I was ground running my engine to tune it with the
EM-2 and EC-2. Ran for almost an hour, at various rpm's to
change the manifold pressure and tweak the settings. Cooling working
well, I had the top cowling off to allow good exit area since I was
tied down. Coolant pressure about 14 psi as reported on the
EM-2.
Engine was running good, took it up to
~6000 rpm swinging a 76x76 Catto prop, when suddenly there was steam
and fluid on my windshield. Shut it down by killing power to the
EC-2. Coolant everywhere.
Got out and looked to diagnose the
problem -- NOT my plumbing. A FREEZE PLUG in the iron housing
had blown out. Rapid coolant dump.
Secondary effect -- Since I shut down
suddenly from full tilt, either the proximity of the cowl to the
exhaust, or possibly some of the coolant on the exhaust started a
small fire on my cowl. Put it out with extinguisher, but corner is
charred.
Now in repair mode.
--------------------------
Update since this incident: All
freeze plugs (7) on the engine have been replaced by Bruce
Turrentine, and he has inspected the engine. I am currently
reinstalling it and getting ready for more tuning
exercises.
Bill Schertz
KIS Cruiser #4045
N343BS
-----
Original Message -----
Sent:
Sunday, April 12, 2009 1:51 PM
Subject:
[FlyRotary] Re: forced landings
Charlie, That's a very good point. I'm
trying to stay away from assigning a "cause" for whatever happened
because I don't have all the facts. I have a field that says
"Explanation of Failure". Hopefully, we can make statements
as you suggest. Sometimes, even the FAA gets it wrong, like
the time they attributed the engine failure to the builder
removing the oil injection pump. Also, I doubt that we could
all agree on a "single cause" for each failure. Maybe it is
due to a poor weld, or wrong choice of material, or improper
strain relief, or lack of heat shielding, or a little of
each. What I hope to accomplish is to point out areas where
we need to be more careful on how we design a particular part or
system. List is at 16 now. Anyone else want to
add a "dark and stormy night" story to the list?
Mark
On Sun, Apr 12, 2009 at 11:46 AM, Charlie
England <ceengland@bellsouth.net> wrote:
I think that it's just as important to understand the real
cause of the failure. In the case of the plastic fuel flow
sensor, it's highly unlikely that use of the plastic sensor
caused the failure; it was the use of plastic in the wrong area
without any protection. The homebuilder's knee-jerk reaction is
to say 'no plastic sensors because that one melted', even though
there are tens of thousands of the same sensor in use in
boating, a much more severe environment.
Kind of like the
canard builder who tried to put fuel in a wing built with
fuel-soluble foam. Obviously, it failed, but only because of the
wrong application of products, not the products
themselves.
Charlie
From: al wick
<alwick@juno.com>
Sent: Sunday, April 12,
2009 10:13:00 AM
Subject: [FlyRotary] Re:
forced landings
Absolutely excellent Mark. I'd encourage you to get the year
the incident occured too. That will be your proof of reduced
risk from things like this newsgroup.
Avoid the black and white approach: forced landing or not
forced. Because all things are shades of grey. Instead rate the
severity. So it's a 10 if the guy had to glide, it's a 1 if
he did precautionary landing. If you also explain what happened,
then a reader can easily tell you were objective in your rating.
The final piece is about how many flight hours, first flights
there were. Each year there are more engines flying, so way more
likely you will hear of incident. A wild assed guess is ok, if
you just base the guess on some facts. For example, you could
check faa database and find 100 planes registered with rotary
engine in 2005. You can guess that equals 70 hours each. Even
though it's a wild assed guess, it will still be excellent
predictor of change over time. Each year you have the same
"error". So your numbers WILL reflect improvement.
More important than anything. If you can force your self to
say: "That same failure will happen to me". Particularly if you
can look at "contributing factors". Then you can dramatically
reduce personal risk. Good example: We had that guy that
installed plastic fuel flow sensor in fuel line. It melted, he
died. Tracy just reported hot exhaust caused fuel to boil out of
carb. These have the same root cause. You don't want to
say:" I have efi, can't happen to me". You want to say:" I
expect heat will cause a failure. I'll put a thin ss shield
here, with a bit of fibrefax glued to back. So if muffler fails,
it won't affect....."
Every forced landing had 10 little incidents in the past that
preceded it. Your risk isn't some new cause. It's 1 of those 10
incidents that you rationalized away, instead of saying:" that
will happen to me too."
Good stuff.
-al wick
Cozy IV with 3.0 liter Subaru
230+ hrs tt
from Portland, Oregon
---------- Original Message
----------
From: Mark Steitle <msteitle@gmail.com>
To: "Rotary motors
in aircraft" <flyrotary@lancaironline.net>
Subject:
[FlyRotary] Re: Gary Casey was [FlyRotary] Re: Rotary
Engines
Date: Sun, 12 Apr 2009 06:45:24 -0500
Mike,
Has anyone ever tried to document the rotary incidents
resulting in a forced landing?
Here's what I recall from
memory, so it likely is missing a
few;
3 forced landings due to
ruptured oil coolers
1 forced landing due
to apex seal coming out of its slot (rotor out of
spec)
1 forced landing due to improper
assembly of engine (seal wedged between rotor & side
housing)
1 forced landing on highway due
to catastrophic overheating of engine
2
forced landings (one fatal) due to probable fuel system design
flaw
1 forced landing on highway
due to ingestion of FOD.
There were a few others,
such as turbo failures which allowed for continued operation at
reduced power, so we may or may not wish to include those
here.
While a number of these incidents date back
quite a few years, and we have made excellent progress, it says
to me that we still have room for improvement in the peripheral
department. The good news is that out of all of the
incidents listed above, none of them were caused by a true
engine failure. That's where the rotary has really earned
my respect as a viable a/c engine.
Pay attention to the
details!
Mark S.
This has been an interesting
thread. In the end, it doesnt really matter how many "major"
parts you have - even a minor failure can bring you down.
While I believe the basic rotary engine itself is more fault
tolerant than a recip, the peripherals used in the typical
rotary install are a lot more complex than a typical recip
install. Since we rotary fliers dont have the benefit of 70
years worth of experience flying behind the typical LyCon farm
implement I think overall our odds are considerably worse.
Comes down to how well an individual engineer's his
installation and there is a tremendous amount of variation
here.
The dependence on electronics in
the typical rotary install is a good example. I may be a
little sensitive to this issue since I've been trying to
find an intermittent glitch (2 times in 22 hours of engine
testing).
Mike Wills
RV-4
N144MW
-----
Original Message -----
Sent:
Saturday, April 11, 2009 7:31 AM
Subject:
[FlyRotary] Gary Casey was [FlyRotary] Re: Rotary
Engines
Good
analysis and logic, Gary.
You’d
make a good addition to the “rotary community”. I have
noticed over the 10 years I have been flying my rotary
powered RV-6A that the problems have decreased considerably,
the success rate and completion rate has gone up and first
flights are now occurring without significant problems –
even cooling is OK {:>). I believe most of this
improvement can be attributed to folks sharing their
knowledge, problems and solutions with others - such as on
this list.
I
know that fewer parts count is often touted as one of the
rotary benefit – and while it is true that the part count is
lower, the most significant thing (in my opinion) is not
only does the lower part count help reliability (if it is
not there – it can not break), but if you look a the design
of the eccentric shaft (for example) you notice the absence
of the jogs in a typical crankshaft and their stress
points. The thing is over 3” in diameter at some
points and does not have the same inertia loads born by a
piston crankshaft. The parts that are there are of
very robust design. Finally, the rotary is (I believe)
more tolerant of damage and tends to fail “gradually and
gracefully”, it can take a licking and keep on ticking as
the old saying goes. Only extended time and numbers
will provide the true MTBF for the rotary, but I believe it
looks very promising.
Failure
of rotary engines are extremely rare, but unfortunately, as
with many alternative engine installations, auxiliary
subsystems such as fuel and ignition frequently being
one-off designs have been the cause of most failures – with
probably fuel the prime culprit. The good news is that
for some platforms (such as the RVs) we have pretty much
established what will make an installation successful.
The Canard crowd is fast approaching that status with their
somewhat more challenging cooling requirements being over
come.
Having lost a rotor during flight due to putting in high
compression rotors with worn apex seal slots worn beyond
specs (found this out later – my fault for not being aware
of this spec limit and checking it) which led to apex seal
failure and consequence lost of most of the power from one
rotor, I was still able to maintain 6500 MSL at WOT and fuel
mixture knob to full rich – flowing 14.5 GPH – a lot of it
undoubtedly being blown through the disabled
rotor. Flew it back 60 miles to a suitable runway and
made a non-eventful landing. There was a small
increase in vibration due to the power strokes no longer
being balanced, but nothing bad and you could still read the
needles on the gauges. Other folks have had FOD damage
to a rotor and also make it to a safe landing. Two
folks lost cooling (one loss of coolant fluid , one lost of
water pump) and while they did cook the engines, both made
it back to a safe landing. So all things considered, I
think the rotary continues to show that if the installation
is designed properly, it makes a very viable and reliable
aircraft power plant.
Failure
of rotary engines in aircraft are extremely rare, but
unfortunately, as with many alternative engine
installations, auxiliary subsystems such as fuel and
ignition frequently being one-off designs - have been the
cause of most failures. The good news is that for some
platforms (such as the RVs) we have pretty much established
what will make an installation successful. The Canard
crowd is fast approaching that status with their somewhat
more challenging cooling requirements being over
come.
My
rotary installation cost me $6500 back in 1996, the primary
cost being a rebuilt engine $2000 and the PSRU $2900.
I have since purchased a 1991 turbo block engine from Japan
for $900 and rebuilt it myself for another $2200. My
radiators (GM evaporator cores) cost $5.00 from the junk
yard and another $50.00 each for having the bungs welded
on. So depending on how much you buy and how much you
build the price can vary considerably. Today, I would
say it would take a minimum of around $8000 and more
nominally around $10000 for a complete rotary installation
in an RV – some folks could do it for less, some for
more.
But,
regardless of the technical merit (or not) in someone’s
mind, the crucial thing (in my opinion) is you need to
address two personal factors:
1.
What is your risk tolerance? It doesn’t really matter
how sexy some “exotic” engine installation may seem – if you
are not comfortable flying behind (or in front) of it, then
it certainly does not makes sense to go that
route. After all, this is supposed to have an element
of fun and enjoyment to it.
2.
What is your knowledge, experience and background (and you
don’t have to be an engineer) and do you feel comfortable
with the level of involvement needed.
So
hope you continue to contribute to expanding our knowledge
and understanding of the rotary in its application to power
plant for aircraft.
Best
Regards
Ed
From: Rotary motors
in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Gary
Casey
Sent:
Saturday, April 11, 2009 8:36 AM
To: Rotary motors in
aircraft
Subject: [FlyRotary]
Re: Rotary Engines
Just to add a few more comments and
answers to the several excellent comments
posted:
How many parts does it take to make
a rotary rotate? Well, "parts aren't parts" in this
case. Mark was right in that there are maybe 4 "major"
components, but you have to define major. A piston
engine certainly has far more major parts. Is a valve
a "major" part? I think so. Is a rotor corner
button a major part? Not sure, but probably not.
Is each planet gear in the PSRU a major part? I
say yes, and the PSRU is an integral part of the rotary
engine. As someone correctly pointed out, it's not how
many parts, but the reliability of the total system that
counts. Just looking at the history of the rotary
(which, from the implication of another post) it's not that
good, but I don't think it has anything to do with
reliability of the concept. It's more to do with the
experimental nature of the builds and installations.
My original point, perhaps not well expressed is that
to say there are just 4 parts is an oversimplification.
But let's face it, to put in an engine that has had
many thousands of identical predecessors is less
"experimental" than one that
hasn't..
Are we ES drivers more conservative?
Probably so, since the ES is probably one of the
experimentals most similar to production aircraft, and not
just because the Columbia (can't force myself to say Cezzna
:-) was a derivative. Therefore, it tends to attract
conservative builders and owners. Not surprising then
that almost all ES's have traditional powerplants, with the
most excellent exception of Mark. While there may be
more, I know of only two off-airport landings caused by
engine failures in the ES in almost 20 years of experience.
One was caused by fuel starvation right after takeoff
(fatal) and one was caused by a PSRU failure in an auto
engine conversion. So our old-fashioned conservative
nature has served us pretty well.
Yes, I was assuming that the rotary
had electronic fuel injection and ignition, but that by
itself doesn't change the inherent fuel efficiency of the
engine. Direct injection does have a potential to
improve BSFC because the fuel charge can be stratified.
It will probably decrease available power, though.
I think the best rotary will be 5% less efficient than
the "best" piston engine(same refinements added to each).
But I stated that as a simple disadvantage - as Mark
pointed out, it isn't that simple. The rotary already
comes configured to run on auto gas. The piston engine
can also be so configured, but the compression ratio
reduction would reduce its BSFC and maybe durability
advantage. The total operating cost is certainly
significantly less if auto gas can always be used to refuel.
I assumed in my assessment that it will only be
available 50% of the time. The real disadvantage,
which I failed to state, is that the extra fuel required for
a given mission might be 5 or 10% higher and that negated
the weight advantage, if only for long-range
flights.
Is the engine less expensive?
I did a thorough analysis of a direct-drive recip auto
engine installation and my conclusion was that if the auto
engine were equivalent in reliability to the aircraft engine
it would likely cost just as much. Is the same true of
the rotary? I'm not sure, but you have to consider the
total cost, including engineering of all the parts in the
system, not just the core engine. I would love to do a
rotary installation, but I don't think I could justify it by
cost reduction.
It wasn't mentioned in the posts,
but some have claimed the rotary is "smoother" than a recip.
I at first resisted that notion. Sure, any
rotary given sufficient counterbalancing, is perfectly
balanced. A 4-cylinder opposed recip is not - there is
a significant secondary couple. The 6-cylinder opposed
engine is perfectly balanced, but only for PRIMARY and
SECONDARY forces and couples - higher order forces have
never really been analyzed, although they would be very
small. And then consider the forces within the engine
that have to be resisted by that long, heavy, but flexible
crankshaft. So it isn't the mechanical balance that
gives the rotary an advantage. Let's take a look at
the the torsional pulsations, comparing the 3-rotor against
the 6-cylinder: A 6-cylinder engine has 3 power
impulses per rotation, as does the 3-rotor, so they are the
same, right? Wrong. They both incorporate 4
"stroke" cycles, meaning that there separate and sequential
intake, compression, power and exhaust events so that is the
same for both. The power event, which is the source of
the torque impulse, takes 1/2 of a crank rotation for
the recip. In the rotary the power event requires 1/4
of a ROTOR rotation, but the rotor rotates at 1/3 crank
rotation - the result is that the power impulse lasts 3/4 of
a CRANK rotation, 50% longer than in a recip.
Therefore, the torsional excitation delivered to the
propeller, PSRU and to the airframe is significantly less
than for a recip. And if you analyze the actual forces
imparted, they go down by the square of the rpm. The
torsional vibration amplitude goes down by a factor of 4
just because the rpm of the rotary turns about twice as
fast. If you've skipped to the bottom of the
paragraph, as you probably should have :-), yes the rotary
is "smoother" - a LOT smoother.. (my apologies to rotary
purists, for simplicity I used the word "crankshaft" for
both engines)
But just because you can burn auto
gas should you? The biggest problems with auto gas in
recip aircraft have nothing to do with the engine, but with
the high vapor pressure of the fuel - it is more prone to
vapor lock. The fuel systems of certified aircraft are
not particularly well designed with regard to vapor lock.
"Fortunately", rotary engines typically have no
mechanical fuel pump and are forced to rely on electric
pumps. Fortunately because the pumps can be located at
the very bottom of the aircraft and close to the fuel tanks,
making vapor lock much less likely. I would caution
any builders to consider vapor lock possibilities very
seriously, much more so if you intend to run auto gas.
when I was going to do this I planned to put one
electric pump in the wing root of each wing, feeding the
engine directly(the check valve in the non-running pump
prevents back-feeding). Redundancy was by a
"crossfeed" line that could connect the tanks
together.
And thanks, Mark for - probably
incorrectly - referring to me as a "good engineer".
I'll have to put that in my
resume!
(do you allow us outsiders in your
events? I'll park well away
:-)
__________ Information from ESET NOD32
Antivirus, version of virus signature database 3267
(20080714) __________
The message was checked by ESET
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-- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.nethttp://RotaryRoster.net
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