|
|
Actually, I like Bill’s suggestion
of using a slice of the next side tubing – but, I think I would still
braze it, I have just never had much luck with sticky stuff (one reason I built
a metal aircraft {:>)).
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Schertz
Sent: Monday, April 13, 2009 6:16
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Beading a
tube - sort of: [FlyRotary] Re: forced landings
Ed's method is very nice, and superior to my suggestion, but
for what it is worth, here is another that I have used, take a piece of
tubing the next size up that just slides over the tubing in question, cut a
ring ~ 3/32 inch wide off the end ( on a lathe if you have one), and JB
Weld it in place on the end of the tube.
Bill Schertz
KIS Cruiser #4045
N343BS
----- Original Message -----
Sent: Monday, April 13,
2009 4:46 PM
Subject: [FlyRotary]
Beading a tube - sort of: [FlyRotary] Re: forced landings
Bill, here is something you might try if
you can not find, beg, or borrow a big expensive beading machine.
Take some soft aluminum rod of the size you
want for a bead. Bend it around the tube and cut it to a length where the
ends of the rod meet around the tube. Position the rod ring near the end
of tube and clamp it in place. Then use some of the HTS- 2000
aluminum brazing rod (other stuff may work, but this is the only rod I’ve
ever had any luck with) and a propane torch to braze the rod on the tube.
A bit of touch up with a fine file or sand paper and you have your bead.
A bit of work, but not that hard and if you don’t have access to a
beading machine one way to get the job done.
URL of site:
http://www.aluminumrepair.com/
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bill Bradburry
Sent: Monday, April 13, 2009 5:17
PM
To: Rotary
motors in aircraft
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
|
|