----- Original Message -----
Sent:
Wednesday, June 03, 2009 8:16 AM
Subject:
[FlyRotary] Incident No. 5119
Certainly not
trying to “TOP” Al’s door incident – by the way, good airman ship and
decisions, Al! Glad the damage was no worst that it
was.
But several folks
who were not at the Texas Round up have asked about the “Ed’s
Incident”. For those of you who were at the roundup, you will probably
want to skip this repeat.
Incident No.
5119
One the way to
Texas I had an incident that ended up in
with me and aircraft making a 7 mile engine-out glide into Craig Field
(Selma, Alabama). Again – NO! It was not
fault of the engine or even the subsystems. But, the complete answer
is not provided until after my litany of the conditions and symptoms – can
you figure it out?
I took off on
Thursday AM planning on stopping in Mississippi to join up with Charlie
England and Tracy. After spending the night there, we all three would
head for Texas. But, the weather (as you are
aware) has been laying over the southeast for days with rain and more rain –
but I launched into it anyway as past Atlanta, GA things were forecast to
improve..
Other than dodging
lines of clouds and a bit of scud running, but not much, I landed at
Alexandria City to the southwest of Atlanta, GA to take on fuel. I then climbed
back in and fire it up and took off.
I noticed that
during climb-out the engine would occasionally miss and thought the fuel
might have had a bit of water in it, but was not really concerned. So
I fly on for approx another 45 minutes and had just passed Selma, Alabama and old
Craig Air Force base, and turned west toward Mississippi, when more symptoms began to
occur.
It started to act
like a case of SAG (fouled spark plugs) where the rpm will drop a bit – not
dangerous - just nerve racking. But, shortly things began to go beyond
the SAG symptoms, so I though I might have an injector problem (like one
sticking open or not opening at all). Since our injectors are in
pairs, I tried turning off one figuring if things got better, then that pair
might have a bad injector.
So I turned off one
pair and sure enough the symptoms abated a bit (more on this later) so I
figured I had a bad injector in that pair. To be certain I turned this
“bad” pair back on and turn off the “good” pair expecting the symptoms to
really get bad as I would now be running on only the “bad” pair – much to my
surprise when I turned off the “good” pair – the symptoms also abated.
So that indicated it was not an injector problem – but what?
About this time, I
decided to turn the aircraft back around toward Craig Field and dodging
clouds headed back with the engine progressively getting worst. It
appeared to be a fuel problem (and while that is ultimately the subsystem
affected - it was not the root cause). The fuel pressure was ranging
from zero to 80 psi, other electrical things were also misbehaving. I
check the voltmeter thinking perhaps the alternator had died – but it showed
14 volts. So back to the fuel system.
Finally, the
engine just stops with the prop standing still - like a hood ornament, I’m
at around 4500-5000 MSL at this point having lost some altitude dodging a
cloud (good old GPS just kept pointing to Craig Field). At that time I
am 7 miles out from Craig Field at 4500 msl with at stopped prop, a crippled
seat cushion and a dry mouth. Yes, I know I’ve been there before, but
I don’t think you ever get “use” to it. I recalled thinking things
just can’t get worst when they very shortly and suddenly -
did.
I keyed the radio
and made a call to Craig Field at 4 miles on the GPS (I’m starting to get
good at this) but before I could get their reply, I heard a
“CLANK” (without the engine
running you can hear things like that) like a relay springing open (it
was) and the entire panel goes dead!!!! No radio, no engine
instruments, not even a stinking LED was lit – only the battery powered
GPS. Can you spell “total electrical failure?” Talk about a
lonely feeling – amazing how comforting having lights on and radio – you
could almost convince yourself this was just a practice engine-out landing,
but not when the panel goes dark. No engine gauges, no radio,
nada!
Well not being one
inclined to panic (but I seriously considered it for a moment {:>)), I
continued toward Craig field – I mean like there were lots of other
alternatives. Well Once again I found myself in the “fortunate
position” of being too high, too much altitude. So I put in 40 degs of flaps
to steepen my rate of descent. But, then I decided this time that rather
than do the 360 I had done on a previous Incident to lose “excessive”
altitude, I would try to glide - a more or less - regular traffic
pattern.
However, I
neglected to remember to retract the flaps. So I found myself on the
downwind around mid-field at pattern altitude (which felt normal) until I
suddenly realized that you CAN NOT maintain that pattern altitude without an
engine!!! Duh!
I knew I could
never make it to the far end of the runway before turning base (toward the
runway), so I started my turn immediately, to make matters a bit worst - I
had been paralleling the runway on the downwind leg a bit too close – must
have been the comforting feeling of being close to safety. This
position naturally required a tighter turn and as I turned I saw I was
likely to miss the runway and land in the grass. So I though I need to
steepen this turn further (this is called COFFIN CORNER), but fortunately
glanced at my airspeed indicator to see it only registering 80 MPH and my
rate of descent (normally 400-500 feet per minute) up to over 1000 feet per
minute. The seat cushion suddenly vanished from this
universe.
But the REAL
danger in this situation, as you all know, is your airspeed gets low, you
are in a steep bank which greatly raises the stall speed - meaning at
80 mph you are close to a stall in a steep turn while your are not in
straight and level. So I immediately straighten out of the turn – the
little voice saying “better to land in the grass than get their concrete
runway all messed up”. So the immediate danger of a stall was
adverted, but I was still pointed toward the ground with a sink rate twice
as high as normal (and I’ve manage a few hard landings even with a normal
sink rate).
The hardest thing
to do when you are sinking at a 1000 fpm a couple hundred feet above the
ground (with your nose already pointed at the ground) is to push the stick
forward steeping the dive even more. But, I manage to do that and
picked enough air speed and energy to flair to a nice touch down – not even
a bump. I’ve always been amazed at what total concentration does to
improve you landing {:>).
Rolled to the end
of the runway and had energy to roll off onto the taxiway. Got
out, check under the aircraft for any evidence of leaks and started pulling
the aircraft toward the far –off – hangar which had an airplane parked in
front of it. A nice looking young woman comes riding a bicycle out to
meet me. Hopped off and holding out her hand said “Hi I’m Angie, looks
like we’ll be spending time together” – so things are starting to look up
{:>)
So pulled the
aircraft in to the hangar where the mechanic came over and ask what the
problem was. Well, I looked at the volt meter and it said the battery
was dead. Mechanic put on a battery charger and announced “Yep! The battery
is dead”. So we both concluded that the alternator must have failed
and not being able to replenish the drain on the battery by all the
electrical systems such as fuel pumps, injectors, ignition coils, etc had
drained the battery.
However, there were
a few problems with the analysis of a failed alternator. First, the
low voltage warning light never came on to warn of an alternator problem,
2nd I never notice the voltmeter showing anything other than what
it should for alternator voltage – like around 14 volts. While
checking the voltage after the Mechanic had charged the battery, I noticed
down below that the “essential bus” switch was in the battery rather than
the alternator position, so flicked it back to the alternator position
figuring I must have accidentally kicked it while getting to some stuff in
the baggage compartment of my RV-6A.
It was getting late
and being a bit tired not to mention stressed, I needed to get a rental car
and a motel for the night. Did that, eat dinner and went to bed after
sitting down and drawing out a problem tree with the entire major elements
of the electrical system.
So next morning I
show up at the hangar early and meet Ben, the mechanic, the battery had
received a charge of only 45 minutes the evening before, So I suggested we
charged it for another hour and try to start the aircraft. Ben
suggested a real stress test of the battery and NOT charge it anymore.
Made sense, so we rolled the aircraft out of the hangar. I hopped in,
threw a half dozen switches and punched the starter button. The engine
started on the first prop blade rotation – so the battery was clearly
OK. The engine is humming like a
top. So I looked over at the voltmeter expecting it to show
only around 12.8 volts instead of the 14 volts a functioning alternator
would produce. Much to my and Ben’s surprise the alternator voltage
read 14 volts. We loaded the alternator by turning on the both l00
watt landing lights, all fuel pumps, the pitot heat, etc. The
alternator voltage only drops perhaps 0.4 volts clearly indicating the
alternator could carry the load and was OK.
So here I am –
battery is OK, alternator is
OK – engine is purring normally,
so clearly this was all a figment of my deteriorating brain cells. I
loaded up the aircraft and launched to do a few circuits of the airport – I
did so and all was operating normally and so I radio them I was head onward
to Texas. While flying, my mind could
not let go of the problem and finally the light came on.
The essential bus
switch had (for my entire 10 + years of flying) been in the alternator
position. The purpose of this switch is to isolate the battery from
the alternator should the alternator fail - to prevent an alternator problem
from draining the battery. So in event of an alternator problem, you
move the switch from alternator to battery. Its call the essential bus
because you only have the essential things drawing from the battery so you
wont’ drain it as quickly. The idea is to give you time (generally
around 30 minutes) to find a safe place to land in case of alternator
failure.
Well, at some point
I had either (not paying attention) turned the switch to battery thinking I
was turning the voltmeter switch to battery - or accidentally had move
the switch from alternator to battery without noticing it by kicking it,
etc. However, it was sort of protected in its position from accidental
activation. It must have happened during refueling – as I got approx 45
minutes down the road on the battery after take off before quality battery
time started to deteriorate. As the battery voltage fell due to the
load (and no alternator link to replenish it), electrical things (mainly
computers first) started acting up until they could not longer run the
engine. The injectors would not open fully, etc. Then as the voltage
level further decreased, the master relay which the battery held closed and
which connected the (fully functional) alternator to the rest of the
electrical system - opened up and removed ALL power from the electrical
system. So no radio, no gauges, etc.
Oh, another
little factor that may have contributed, the voltmeter has a tiny toggle
switch by it marked ALT BAT1 BAT2 for checking alternator battery 1 and
battery 2 (which I no longer fly with) voltages. Down below It a
couple of inches and off to the right is the essential bus normal size
toggle switch – also marked ALT BAT1 BAT1. I normally never touch it
and don’t even think about it. But I could have reached for the
voltmeter toggle thinking to check my battery voltage (which I do as a
regular thing) and perhaps distracted by something reach a bit further down
and instead moved the essential bus switch from Alternator to Battery cause
this entire event. I know that I did not consciously do it. So
it is either accidental or absence minded activation - either way ends with
the same results {:>)
Now it became clear
why it didn’t matter which pair of fuel injectors I turned off – turning off
either pair improved the situation because it slightly reduced the
electrical load by a few amps – and the engine ran slightly better for a few
moments. The same thing had happened when turning off one of the EFI
fuel pumps – but what threw me was the alternator voltage continued to be
normal during this.
After I knew the
cause (switch in wrong position), I decided the problem was fixed so no
reason to return to NC, and I just continued on to Texas.
I know some of you
may think that removing my second battery was a mistake – but, consider
this, having another battery could have meant I would have been much further
from a suitable airfield before they both went south. On the other
hand, it might have caused me to at least think to throw the essential bus
switch to the second battery and have the Light bulb come on. Who
really knows. But, I have in mind a simply addition to my electrical
circuit that should help in the future.
I do want to state
that this time when the problems started I DID switch fuel tanks – but
naturally it had no effect because this time it turned out, it was not a
fuel problem – not the root cause at least.
So what are the
lessons learned:
- Put EVERY critical switch on
your before-takeoff Check list
- Perhaps put a guard around
such critical switches to force conscious activation
- Don’t (hard not to) get overly
focused on what you think is the problem – consider other
possibilities. I thought it was a fuel problem (I even switched fuel
tanks this time) – it turned out to be electrical in its root
cause.
- While the fuel pressure was
jumping all over the place and the EGT was erratic and engine surging
strongly indicating a fuel problem – the ultimate cause was
electrical. Once the voltage got below a certain point the EC2 was
still trying to pull the injectors open, but with the voltage so low it
could not do it properly.
- When the battery voltage
dropped below a certain point, the master relay released and removed the
alternator from the electrical system and the panel went dark – even
though the alternator was still working
- Immediately turn to the
nearest airfield when serious problems occur - THEN work on fixing
them. I only delayed for perhaps 2-3 minutes, but that could have
made a difference.
- Watch out for Coffin Corner turn when turning base
to final – airspeed really bleeds off fast with no engine pulling you
along (and especially with flaps deployed!)
- IF you change your mind about
landing approach type - remember to reconfigure your aircraft for the last
decision – I had left my flaps deployed when I should have remembered to
retracted them. Did that help prevent a Coffin Corner stall and spin
or would it have put me closer to it?
- You must increase airspeed
over the wing to get the sufficient energy to over come a high sink
rate. Pulling back on the stick when the ground is staring you in
the face is the natural reaction – but, pushing forward to lower the nose
is the correct action – providing of course you have sufficient
altitude!
- Battery life
– I had a two year old 680 odyssey battery which I maintain a trickle
charge on whenever I’m not flying. With two EFI fuel pumps, boost
pump, injectors, coils, EC2 and radio and just having started the engine
before take off – this battery lasted 55 minutes. Well, the last 5
minutes was not quality battery time. So in my case, 30 minutes
appears to be a very realistic battery life. In fact, had I turned
off one EFI pump and the boost pump would have gained a few more
miles. But, if I had recognized the need to turn them off at that
time (I normally turn them off at cruise altitude), then I would have
known how to “fix” the problem.
- I’ve decided to add a Schokkty
diode between my essential bus and the alternator – so that as long as the
alternator is producing sufficient voltage, then the battery will be
getting some charge to replace the drain. I’ve also decided to make
that switch position a check-list item.
So what it
boils down to – if I had recognized early on that it was an electrical
problem and not focused so much on the fuel system, I may have noticed the
essential bus switch in the wrong position. Force yourself to examine
other possible causes (easy to say – harder to do).
NEVER, NEVER forget
that flying the airplane is the first and only priority in this type of
situation
NEVER, NEVER forget
that saving your butt is the ultimately end-all priority. When I
decided that landing on the grass was preferable to putting a hole in their
concrete – I just may have made a life-saving
decision.
If anybody else
wants to pick up this baton – I’m ready to hand it over – what? no
volunteers? {:>)
So that’s my story
and I’m sticking to it.
Fly safe,
guys!!
Ed
Ed
Anderson
Rv-6A N494BW Rotary
Powered
Matthews,
NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm