Most of us have flown on commercial airliners and
have noticed that all of them have at least two engines. These
aircraft are designed in such a way that should one engine fail,
the other engine would be able to get the aircraft to a safe landing.
Many of the larger helicopters also have more than one engine
both for power and safety. Our little helicopters do not have
the luxury of twin engines for safety so we must insure that the
systems that have been designed to keep our one engine running
smoothly, even in the event of a fuel pump, ignition, fuel injection
system, or computer failure. Rotorway has included backup systems
for these critical systems but many of us have been flying these
machines with a fatal flaw that can take out all primary and back
up systems simultaneously. WILL YOUR HELICOPTER BE NEXT? Now don’t
panic, there is a simple fix to this problem and I wanted to get
the word out to all Rotorway owners that without this fix, they
may be next, complete engine shutdowns have happened twice that
I know of in just the past 12 months.
Over the years of my involvement with Rotorway helicopters I
have experienced a number of component failures. As I look back
on each of these failures, the majority of them could have been
prevented either by improved maintenance procedures or by carefully
looking at the design of each system on the helicopter. A big
factor in preventing failures is to have as thorough an understanding
of your helicopter’s systems as possible and that is the primary
reason that I take the time to write these articles. My goal is
to pass along the knowledge and experience that I have gained
from flying literally hundreds of different experimental and certified
helicopters over the years including the two Rotorway helicopters
and one Ultrasport 496 that I have personally built and flown.
My helicopter experience began with the purchase of a basic Exec152
that came standard with an automotive-style distributor that ran
off a little wimpy V belt that was about 1/8” wide. We called
it a sewing machine timing belt at the time and that is most likely
what it’s origin was. This system never impressed me as being
reliable and eventually supported that suspicion by failing resulting
in an autorotation to the ground.
Back then those of us who were builders mostly networked by phone
calls and group meetings since we did not have the internet with
which we could network and share our ideas. The Rotorway factory
did not encourage builders to interact with each other and often
builders in close proximity to each other were unaware that there
were other builders nearby. Through clubs like the Sierra Rotorcraft
club that many of us belonged to we were able to compare notes,
meet other builders, and encourage those that were in the building
process.
The main problem that we all were concerned about was that the
ignition system did not have any backup system. If any part of
that system failed, the engine would shut down. Some folks figured
a way to install dual electronic ignition with a set of diodes
both firing the same set of spark plugs. The heads only had one
plug per cylinder and I know of at least one builder who filled
in the spark plug hole and then drilled and tapped in a dual set
to allow for the redundancy of dual plugs.
My very first auto occurred on April 29th of 1993 while providing
autorotation training to a student pilot Dan VanDuesen who was
getting ready to take his check ride at the Rotorway factory.
We had completed several practice autos and were climbing through
250 feet AGL heading for 500 feet AGL for another one when the
engine quit. Dan was on the controls and I realized quite quickly
the benefit of the flight instructor keeping his hands on all
controls at all times. Dan was not fast enough to react on the
controls for me so I immediately lowered the collective into the
pocket and began a turn into the wind. We later discussed the
incident and decided that we both lowered the collective at the
same time. The lowering of the collective actually took place
in less than a second from the time the engine quit so it was
understandable that both of us would not wait for the other to
drop the collective.
I had received autorotation training from several flight instructors
by this time and practiced power recovery autos most times that
I flew. In what seemed to be only about 5 seconds but was actually
more like 10 we were sitting on the ground realizing that we were
still upright and the helicopter was intact. When we got out to
inspect the helicopter we found that the tail rotor end cap was
polished and there was a small rock directly behind the little
Scorpion that had a streak of aluminum on its surface.
Further investigation showed that the single coil on this single
ignition engine had failed resulting in a complete engine shut
down. If this helicopter had been equipped with a dual ignition
system, this failure would not have resulted in the engine quitting.
While I hiked the 3 miles back to my hangar to take the coil out
of my Exec152, Dan used his permanent marker to memorialize that
momentous event. I now have a rock that sits on my desk to this
day as a reminder that things can and will go wrong with these
helicopters but with proper training and good judgment, we can
get through them in one piece.
Since that first auto in 1993, I have had to do several more
in Rotorway helicopters. Each one was a learning experience and
looking back on each one, the failures that precipitated those
autos could have been avoided had I known what to look for.
One of those failures was caused by an old fuel pump. This one
was at least 10 years old and should have been replaced. This
Exec had redundant fuel pumps but one of them failed in a manner
that I had not anticipated. Over time the “O” ring that sealed
the two components of one of the pumps had deteriorated and cracked
to the point that all at once while I was out flying I was engulfed
in fuel vapors and mist and could not even breathe. All I could
think about was those fuel vapors finding their way to the sparking
points of the distributor and the entire helicopter exploding
into a ball of flame.
Fortunately I was able to hold my breath and auto the helicopter
safely to the ground and shut down all electrical before a fire
was able to start. I was sure that I was going to be the first
person arriving at the scene of the accident and that I would
beat the paramedics there by at least 15 minutes. Once the helicopter
was firmly on the ground I bailed out and ran but thankfully no
fire ensued. It is important to remember that components age with
exposure to the elements, including the air that they are in.
A component like a drive belt or water hose can age prior to being
installed onto the helicopter and may need replacing if your kit
is of the older vintage.
I have always thought that the 162F wiring was redundant as it
comes from the factory and is installed on the helicopter. About
a week after providing flight training to one of my students he
called to tell me that he had experienced a complete system shut-down
while flying his 162F. He did an auto and the only damage was
a couple of bent skids. The cause of the problem was a solitary
short in a wire that shorted out against the fuel pump inertia
switch bracket. As you can see from the photo, the wire rubbed
on the bracket until the insulation was rubbed through and the
short occurred. The owner cut out the damaged section and then
soldered the wire together followed by properly insulating the
repair. On my next visit to the student’s location we removed
the wiring bundle and then rewired and secured the wiring to prevent
a future short, as shown in the following photo. I had a difficult
time believing that a single short in the electrical system would
actually shut down all of the helicopters systems at the same
time, after all, we had full redundancy for all critical systems
didn’t we?
While I was providing flight training in another student’s 162F
recently, we had a very unexpected failure of the helicopters
electrical system.
This student had built an elevated helipad that was around 5
feet higher than the surrounding terrain so we would lift into
a hover and then execute a max performance take off to attain
ETL (effective translational lift) as quickly as possible so that
we would not settle toward the high weeds surrounding the helipad.
On one of our lift-offs all at once the engine quit, and the helicopter
settled back onto the helipad. In the deafening silence we immediately
noticed that both FADEC displays were off, all warning lights
were off, the fuel pumps had shut off, and both ignition systems
had quit.
This was not only very puzzling but maddening as well. I had,
up until this time, felt that the 162F electrical system provided
for true redundancy of all critical systems that keep the helicopter
running. Isn’t that what we check during our run-up? We fault
FADEC one system by turning off the FADEC 1 toggle and the back-up
system, FADEC two, takes over the engine operation tasks. We turn
off one fuel pump and the other fuel pump maintains adequate fuel
pressure and keeps the engine running. There are two ignition
systems providing independent spark for the dual plugs on each
cylinder so if one system were to fail the other ignition system
would be there keeping the engine running,,,, right?
I remembered that my student Joe had experienced the same problem
in his 162F and that it was caused by a short in a single electrical
wire, could this most recent failure have been caused by the same
type of short?
What could cause both FADEC systems to simultaneously shut down
at the same time that both fuel pumps quit working and both ignition
systems stopped firing? What happened to the redundant back up
systems that are always there giving us such a warm and fuzzy
sense of security? In both of these incidents, all primary and
backup systems quit simultaneously causing complete and instant
engine stoppage.
Obviously something very major had happened and if it had happened
20 seconds later, you would most likely have been reading about
a crash and rollover involving this flight instructor instead
of this article warning you of the potential danger. Fran and
I pulled the helicopter back into the hanger and began taking
it apart. We first removed all of the access panels so that we
could get a good look at everything. The overhead panel has 10
fuses that come pre-wired as a unit from the factory. It was apparent
that two of the three 30 amp battery fuses had blown.
How could that happen? These fuses are supplied with power from
the battery on one side and then the other side sends power to
the ignitions and the FADECS as well as the fuel pumps. Investigating
further we found that the 30 amp fuse on the single wire that
comes from the alternator, is routed along the passenger side
frame and then up to the battery switch in the overhead panel
was also blown. With all three fuses blowing at one time, this
shut off all power to the FADECS, the fuel pumps, and the ignition
systems. There actually was a degree of redundancy but no independence
from one system to the next.
If you look at the diagram (posted under HINTS AND TIPS) you
can see that the factory has wired the fuses and switches so that
power from the battery fuse 1 comes from the battery, through
the 30 amp fuse, hooks up with the 30 amp lead from the alternator
and then supplies electrical power to Ignition 2, Ignition 1,
FADEC 2, and then FADEC 1 before daisy chaining back up to the
second 30 amp battery fuse. These critical systems and not independently
wired at all but are all wired together in such a manner that
allowed one electrical short circuit to take them all out at the
same time. These two incidents that I am referring to are just
the two that I am aware of. Were there others that caused complete
engine shut downs where the cause was never discovered?
There is a photo of the overhead fuse panel as viewed from the
top side under HINTS AND TIP on this forum. The wires with the
red marking are the ones that are feeding all of the engine systems
as outlined in the diagram above. After the photo was taken, we
rewired the panel to separate the primary systems power from that
of the back up system with no interconnection between the two.
We found the precipitating cause of the trouble to be one of the
fuel tank supports. I have seen a number of different ways of
attaching the fuel tanks on the exec 90 and 162F. The factory
plans call for fabricating clamps that wrap around the frame and
then attach to the tank straps with bolts.
There is a photo in HINTS and TIPS that shows how the wrap around
fuel tank support strap has slid down the frame over a period
of 20 hours. I drew a line on the frame where the strap was originally
and the arrow shows where the tank slid causing the tank and tank
strap to settle approximately one inch,
In many of the 162Fs that I have flown the builder has opted to
weld fuel tank support brackets to the frame that the tank straps
bolt onto. The wisdom of using the welded brackets is that the
fuel tanks cannot slip down the frames as they can when using
only wrap around straps.
In the case of this second failure, the builder used the factory
method of securing the tank straps to the frame with wrap-around
clamps.
With time and the weight of full fuel, the tank on the passenger
side had settled enough that the tank strap crushed the 30 amp
feed wire that runs from the alternator to the overhead panel.
This wire then shorted out to the tank strap blowing all three
fuses that powered all engine systems.
If your Rotorway Exec 90 or 162F has the factory supplied wiring
installed then you most likely do not have the redundancy that
you thought. To date I have helped the owners of several 162F
and Exec 90’s to rewire those critical systems to allow for true
redundancy.
We then separated the wires feeding the critical components
as follows. One 30 amp circuit that runs from the alternator ties
into one 30 amp battery fuse, then FADEC 1 and Ignition 1. The
other 30 amp battery fuse powers the backup system. Now if a short
circuit occurs in one of these systems, it will blow the fuses
or pop the breakers of the associated FADEC and ignition without
taking out the backup systems. Now we have true redundancy of
these critical systems and can fly with a greater degree of reliability.
I would encourage everyone that has one of these helicopters
to trace out your wires and insure that you have true redundancy
and not just a false sense of security.
Fly safe and enjoy your these amazing machines.
Orv Neisingh R/H CFI
Sho-Me Helicopters, LLC