A hot start question

On 10 May 2007 20:44:03 -0700, chris wrote:


That sounds a bit different - mixture rich for a hot start?? Is this
because it's a IO520??? I am using a IO360 in an Arrow, if that makes
any difference..

It makes all the difference in the world. You have Bendix/RSA fuel
injection that does NOT have a constant displacement engine driven
fuel pump and that does NOT have a return line to the fuel tank.

"Classic" Continental fuel injection is a different...

BTW, it's easier to add a little more full if you need to than it is
to clear a flooded engine. Sounds like you've got it figured out.

TC

My Lycoming method is full rich, full throttle, pump till indication, ICO,
throttle cracked, and crank. Hot or cold makes no difference (AEIO-540)

Continental- full throttle, full rich, pump on, throttle cracked at full
rich, and crank.

However, I have had difficulty with hot starts with the Continentals- any
suggestions there? Why are they different?

On Sat, 12 May 2007 06:37:18 -0500, "Viperdoc"
wrote:

My Lycoming method is full rich, full throttle, pump till indication, ICO,
throttle cracked, and crank. Hot or cold makes no difference (AEIO-540)

Continental- full throttle, full rich, pump on, throttle cracked at full
rich, and crank.

However, I have had difficulty with hot starts with the Continentals- any
suggestions there? Why are they different?


On quite a few Lycoming installations, trying to restart within 5-30
minutes using your method tends to flood the engine. On these
installations, leaving the mixture at ICO when cranking works better.

The typical procedure for hot-starting the TCM system is throttle
full, mixture ICO, boost pump on low (if a 2-speed pump install) for
4-5 seconds to "purge" the engine-driven pump. Advance the mixture to
full, look for positive fuel flow indication, mixture to ICO. Bring
throttle back to slightly above idle (like where it is for 1000-1200
rpm). Crank and when the engine fires, accelerates, and starts to lean
out, advance the mixture.

I use this method for cold-starts also, varying the amount of time the
mixture is at full depending on the OAT. Lower OAT-more "prime",
higher OAT-less.

The TCM system is quite a bit different from the RSA/Bendix system
that Lycoming uses.

The primary difference is the engine-driven fuel pump.

On the Bendix system, the engine-driven pump is merely a source of
fuel pressure/flow. The first sign of a failing Lycoming pump is
typically reduced indicated fuel flow at TO/climb power. The pump is
not producing enough volume to generate the needed fuel pressure/flow
to the nozzles.

On the TCM system, the engine-driven pump is an integral part of the
fuel injection system. It is a constant-displacement pump, one pump
revolution always moves the same volume of fuel. Depending on engine
demand, the fuel exceeding what the engine needs is returned to the
fuel tank via a return line. Full rich, less fuel back to the tank,
leaned in cruise, more fuel returned to the tank.

The hot-start theory is that when the engine/fuel pump is heat-soaked,
the fuel in the pump "boils" making fuel delivery from the pump hit or
miss. Running the boost pump with the mixture at ICO circulates fuel
from the tank, through the pump, and back to the tank. This ensures
that the pump with "pump" properly during engine start.

For many years, the TCM system allowed zero fuel to the cylinders with
the mixture in ICO. About 10 years ago, some of the systems specs
changed, allowing a slight amount of fuel to bypass into the cylinders
(obviously not enough for the engine to idle, or it would never shut
down).

It has been a few years since I've worked on them, so I cannot be sure
what the current specs are. Limiting the "boost pump on, mixture at
ICO" purge time to 4-5 seconds will keep the engine from flooding if
the installed system is indeed supplying fuel to the engine in ICO.

One very important aspect of the TCM fuel injection system that is
often not covered well in training is use of the electric boost pump.

The TO fuel pressure and the idle fuel pressure are mechanically
adjusted on the engine-driven pump itself, following specific
procedures with the engine (and the engine-driven pump) running. The
electric boost pump is SUPPOSED to provide pressure and volume
similiar to the engine-driven pump, in theory allowing these same
mechanical adjustments to provide close to the same fuel pressures.

In reality, if the engine-driven pump fails (which doesn't happen very
often) the mixture and possibly the throttle may require drastic
changes to keep the engine producing power.

If the boost pump is operated (on high on a 2-speed install) along
with the engine-driven pump, the increase in combined delivered
pressure and volume will render the mechanical settings pretty much
useless, flooding the engine with fuel. This is usually pointed out
during training and in checklists/manuals.

Hope some of this is helpful;

TC

"chris" wrote in message
ups.com...
Hi peoples.. Hopefully this is an easy one for you experts out
there...

Hot start on a fuel injected Lycoming commonly seems to call for
leaving the mixture at ICO and cranking.

The POH for the Arrow II (Lycoming IO-360-CIC) states for "Starting Engine
When Hot"

1. Open the throttle approx 1/2 inch
2. Turn the master switch ON
3. Turn the electric fuel pump on. * -- hand-written footnote says
"Will probably flood"
4. Put the mixture control in IDLE CUT-OFF
5. Engage the starter... When the engine fires, advance the mixture
control and move the throttle to desired setting.

That doesn't make any sense; it floods. I have better luck starting it
flooded, though, so I end up using the next section,
"Starting Engine When Flooded"

1. Open the throttle full
2. Turn the master switch ON
3. Turn the electric fuel pump OFF
4. Put mixture control in IDLE CUT-OFF
5. Engage the starter... When the engine fires, advance the mixture
control and [then] retard the throttle.

That gets us right to Scott's "that 3000
RPM-panicky-grab-the-throttle-quick-before-we-go-flying-into-the-next-tiedown-row
BS", but I finally got the hang of making it work.

-c

"gatt" wrote in message
...

"chris" wrote in message
ups.com...
Hi peoples.. Hopefully this is an easy one for you experts out
there...

Hot start on a fuel injected Lycoming commonly seems to call for
leaving the mixture at ICO and cranking.

The POH for the Arrow II (Lycoming IO-360-CIC) states for "Starting
Engine When Hot"

1. Open the throttle approx 1/2 inch
2. Turn the master switch ON
3. Turn the electric fuel pump on. * -- hand-written footnote says
"Will probably flood"
4. Put the mixture control in IDLE CUT-OFF
5. Engage the starter... When the engine fires, advance the mixture
control and move the throttle to desired setting.

That doesn't make any sense; it floods. I have better luck starting it
flooded, though, so I end up using the next section,
"Starting Engine When Flooded"

1. Open the throttle full
2. Turn the master switch ON
3. Turn the electric fuel pump OFF
4. Put mixture control in IDLE CUT-OFF
5. Engage the starter... When the engine fires, advance the mixture
control and [then] retard the throttle.

That gets us right to Scott's "that 3000
RPM-panicky-grab-the-throttle-quick-before-we-go-flying-into-the-next-tiedown-row
BS", but I finally got the hang of making it work.

-c

This happened to an Arrow at KGKY (Arlington, TX) some time ago. The pilot
was used to flying with toe brakes; this one had only a handbrake. Chewed a
hole through a chain link fence and hit a car. They found one of the
propeller blades several days later imbedded in the roof of the fire station
1/2 mile away.

"Allen" wrote in message
...

That gets us right to Scott's "that 3000
RPM-panicky-grab-the-throttle-quick-before-we-go-flying-into-the-next-tiedown-row
BS", but I finally got the hang of making it work.

This happened to an Arrow at KGKY (Arlington, TX) some time ago. The
pilot was used to flying with toe brakes; this one had only a handbrake.
Chewed a hole through a chain link fence and hit a car.

That's unfortunate. I wonder how much of an insurance hit he/we will take
for something like that. The very first item in the "STARTING ENGINE"
checklist in the POH is:

1. Set Parking Brakes ON.

Managing the throttle and mixture while simultaneously applying toe brakes
and making sure you're not rolling forward would make me nervous. I amended
my run-up checklist to say "Verify no movement" immediately after setting
the throttle to 2000 RPM 'cause the last thing I'd want to do while
verifying mag drops and engine instruments is to look up and realize I'm
moving.

-c

On May 18, 5:05 am, "gatt" wrote:
"Allen" wrote in message

...



That gets us right to Scott's "that 3000
RPM-panicky-grab-the-throttle-quick-before-we-go-flying-into-the-next-tiedo*wn-row
BS", but I finally got the hang of making it work.
This happened to an Arrow at KGKY (Arlington, TX) some time ago. The
pilot was used to flying with toe brakes; this one had only a handbrake.
Chewed a hole through a chain link fence and hit a car.

That's unfortunate. I wonder how much of an insurance hit he/we will take
for something like that. The very first item in the "STARTING ENGINE"
checklist in the POH is:

1. Set Parking Brakes ON.

Managing the throttle and mixture while simultaneously applying toe brakes
and making sure you're not rolling forward would make me nervous. I amended
my run-up checklist to say "Verify no movement" immediately after setting
the throttle to 2000 RPM 'cause the last thing I'd want to do while
verifying mag drops and engine instruments is to look up and realize I'm
moving.

-c

That sounds good, but I would rather use my toe brakes when starting
and doing a runup. Why?? At least twice while doing a runup in an
Archer the park brake has mysteriously unlocked itself, leaving the
aircraft with the meat grinder spinning at 2000rpm to lurch forward
while I leap on the brakes

I used to use park brake but it just makes me nervous - at least with
leaning hard on the toe brakes I am sure it ain't going anywhere!

"Allen" wrote

They found one of the propeller blades several days later imbedded in the
roof of the fire station 1/2 mile away.

Whoa, there, back up!

That sounds like the "big fish" story. It gets bigger every time it is
told.

A half mile is way too far to be believable, if the prop is thrown from
ground altitude.

Two, three hundred yards, maybe. You would need to show me some
documentation for me to believe much more than that.
--
Jim in NC

I saw the pictures of that. 100 yards, maybe.




Morgans wrote:
"Allen" wrote


They found one of the propeller blades several days later imbedded in the
roof of the fire station 1/2 mile away.


Whoa, there, back up!

That sounds like the "big fish" story. It gets bigger every time it is
told.

A half mile is way too far to be believable, if the prop is thrown from
ground altitude.

Two, three hundred yards, maybe. You would need to show me some
documentation for me to believe much more than that.