|
Any good machine shop has a bead roller that can
do the job, including mine. Cost about $2.50 a pipe
end.
Greg Ward
----- Original Message -----
Sent: Monday, April 13, 2009 2:17
PM
Subject: [FlyRotary] Re: forced
landings
Dave’s number 4 below
brings up a question I have been pondering.
How do you put a bead
on the ends of aluminum tubing so the hose will not slip
off???
My tubing is inch and
a quarter and probably 0.060 thick. Suggestions
appreciated.
Thanks,
Bill
B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of David Leonard
Sent: Monday, April 13, 2009 4:48
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: forced
landings
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.
#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.net
http://RotaryRoster.net
On Mon, Apr 13, 2009 at 6:16 AM, Mark Steitle <msteitle@gmail.com>
wrote:
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.
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.
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.
--------------------------
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).
----- 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 NOD32
Antivirus.
http://www.eset.com/
--
David
Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
|