Air restart in PA30

Dennis O'Connor wrote:

The tip is to never shut down a good engine in flight... You can test the
feathering on the ground - that is how the mechanic / prop shop does it...
If the engine actually fails in flight there won't be a restart anyway so
there is no defensible reason to put the plane at such risk, for no
reason...

Testing it on the ground won't really 'prove' that the props will feather when
you need them to. You need to put them up in about a one-hundred mile per hour
slipstream to do that.

Anyway, there are good reasons. After my newly overhauled engines (and one new
prop) had about two hundred hours on them, I felt it was time to verify that the
props would feather as advertised. On a nice VFR day, with plenty of alittude
to work with and near an airport, there is nothing wrong with doing this. Leave
the family on the ground, though.

The engine SHOULD restart successfully, but don't count on it until you've
proven them out.

Engines are also routinely shut down and secured in multi-engine training.

-Ryan
CFII-A/MEI/CFI-H

Of all the PA30's I have flown, not one of them would come out of
feather until the engine was running and developing enough oil
pressure to twist the blades back into high RPM. The starter alone is
not enough to make this happen Most, if not all, of the start
procedure is completed while the blades are still feathered, making
for a whole lot of shakin' till it gets running again.




On Thu, 31 Jul 2003 17:57:38 GMT, Chris Kennedy
wrote:

Julian Scarfe wrote:

[snip]

Unfortunately, it didn't restart fine. I was very close to a "uh, we've
painted ourselves into a corner, here" call to ATC and a real engine-out
arrival, when at the 6th attempt in a 1000 fpm dive at 130 KIAS it finally
came back to life. Fortunately we'd been careful to get ourselves plenty of
altitude before the shutdown.

Any tips on air restarts from the other PA30 drivers out there? I think we
followed the POH to the letter, in particular, mixture RICH for the start.
Is that really best? Why does it differ from the ground start procedure?

I'm going to assume from your description that the prop promptly
unfeathered and windmilled when you cranked it -- the starter should
certainly be able to spin things fast enough to get enough oil pressure
to take the prop out of feather -- and that what you're describing is a
situation where you're looking at the left window at a windmilling prop
while trying to avoid conducting a what-not-to-do Vmc demo.

A secured engine gets seriously cold in flight -- and in a hurry. An
[I}O-360 can be surprisingly difficult to start after being shut down
for just a few minutes (enough so that I don't think I'd even consider
doing something like this on, say, an Aztec with 540s).

Cowl flaps closed, max RPM, mixture full rich, mags in start
configuration, maybe a shot of prime if the CHTs have fallen through the
floor, crank until you come out of feather, then add a bit of throttle
until you have signs of life -- all while remembering to fly the
airplane. Mags to run configuration, adjust the mixture and unless you
need the engine back _right now_, when it does come to live nurse it
along at a low power setting until the temps start to look normal, then
reset power on both engines. Don't forget to close the cowl flaps on
the engine you left running when it settles back down...

IMHO everyone should have to experience an actual shutdown and air start
as part of their ME training. There's something seriously disconcerting
about looking out the window at a prop that's not turning and air starts
always seem to require both coaxing and pleading in equal measure -- as
well as three hands (one each for yoke, throttle and starter).

Julian,

Why the dive? Does the airplane have unfeathering accumulators (I've
instructed in Twinkies but don't recall ever being in one with
accumulators)? With or without them, you should not have had to dive
the airplane. (That part of your post bothers me in that I can't
think of what would make it necessary.)

Have a long chat with your mechanic. I've never had problems with
airplanes with accumulators. Without them, there have been a few
times where it took as many as ten or fifteen brief sessions with the
starter to get the prop to windmill and the engine to start, but I'm
usually just patient and careful not to overwork the starter. (All of
that assumes warm weather. On cold weather shutdown and feather
exercises I start the engine again immediately otherwise it can cool
down very fast and I've been told it may or may not restart.) I also
do the exercise up high and very near an airport that is adequate for
a landing if I can't get the offending engine to snort and bellow
again, although in over 25 years of giving multi-engine instruction I
haven't had that happen yet.

All the best,
Rick

"Julian Scarfe" wrote in message ...
As part of a "debugging" process yesterday, chasing a collection of minor
issues, we tested the feathering of the left engine of our Twin Comanche,
which had appeared significantly slower than the right one. It seemed to
feather fine, with the prop stopping in about 10 seconds.

Unfortunately, it didn't restart fine. I was very close to a "uh, we've
painted ourselves into a corner, here" call to ATC and a real engine-out
arrival, when at the 6th attempt in a 1000 fpm dive at 130 KIAS it finally
came back to life. Fortunately we'd been careful to get ourselves plenty of
altitude before the shutdown.

Any tips on air restarts from the other PA30 drivers out there? I think we
followed the POH to the letter, in particular, mixture RICH for the start.
Is that really best? Why does it differ from the ground start procedure?

Julian Scarfe

Bill Zaleski wrote:

Of all the PA30's I have flown, not one of them would come out of
feather until the engine was running and developing enough oil
pressure to twist the blades back into high RPM.

Hmm. Semantics maybe. I don't consider "out of feather" to be the same
as "high RPM" -- only that the blades have moved off the stops and are
presenting increased drag.

The starter alone is not enough to make this happen

It certainly isn't going to take it to high RPM pitch. No argument there.

Most, if not all, of the start
procedure is completed while the blades are still feathered, making
for a whole lot of shakin' till it gets running again.

I've always associated that shake-n'-rattle with the period between when
the engine gasps to life and the prop starts to govern again. It's been
a while since I played this game (it was one thing to do it over the
flatlands, but it's not my idea of fun since moving to the mountains) so
my recollection may be suspect.

--
Chris Kennedy

http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97

"Julian Scarfe" wrote
As part of a "debugging" process yesterday, chasing a collection of minor
issues, we tested the feathering of the left engine of our Twin Comanche,
which had appeared significantly slower than the right one. It seemed to
feather fine, with the prop stopping in about 10 seconds.

That doesn't sound fine to me. Actually, it sounds quite slow. Mine
feather in less than half that time, worst case.

Unfortunately, it didn't restart fine. I was very close to a "uh, we've
painted ourselves into a corner, here" call to ATC and a real engine-out
arrival, when at the 6th attempt in a 1000 fpm dive at 130 KIAS it finally
came back to life. Fortunately we'd been careful to get ourselves plenty of
altitude before the shutdown.

1000 fpm dive? 130 KIAS? I must be missing something - were you
using the starter? Was the starter not able to crank the engine?

Any tips on air restarts from the other PA30 drivers out there? I think we
followed the POH to the letter, in particular, mixture RICH for the start.
Is that really best? Why does it differ from the ground start procedure?

No clue. Unless I've had the engine shut down long enough for the
CHT's to drop to ambient, I use the hot start procedure.

Prop full forward
Throttle full open
Mixture full rich
Boost pump on for 3 seconds
Mixture to idle cut-off
With one hand, crank starter
Once engine catches, advance mixture with second hand while pulling
back on throttle with third hand. Millions of Martians can't be wrong


No, seriously - once the engine catches, it will idle and you have
time to set the throttle and mixture as necessary. I usually set it
for 11 inches manifold to warm up, since that gives approximately zero
thrust.

It should never be necessary to dive for airspeed - if the starter
can't crank the engine then something is seriously wrong.

If the engine was warm and flooded, then starting with mixture rich
can take a long, long time.

Michael

Thanks to all for the comments.

"Chris Kennedy" wrote in message
...

I'm going to assume from your description that the prop promptly
unfeathered and windmilled when you cranked it -- the starter should
certainly be able to spin things fast enough to get enough oil pressure
to take the prop out of feather -- and that what you're describing is a
situation where you're looking at the left window at a windmilling prop
while trying to avoid conducting a what-not-to-do Vmc demo.

My recollection is that it didn't come out of feather, or at least not much.
So my experience was closer to what Bill describes. But it's tricky to see
if the blades are fully feathered or "moved off the stops". It didn't seem
significantly more draggy.

Rick wrote:

Why the dive? Does the airplane have unfeathering accumulators (I've
instructed in Twinkies but don't recall ever being in one with
accumulators)? With or without them, you should not have had to dive
the airplane. (That part of your post bothers me in that I can't
think of what would make it necessary.)

No, no accumulators. The dive was an attempt to get more airflow through
the prop and therefore more lift on the blades helping them to turn as they
unfeathered slightly (or is it less drag as they start to turn?). I don't
have any conclusive evidence that the speed and the restart success were
related, but it "worked".

(FWIW we performed the exercise at altitude and within a few miles of home
base with a nice long runway.)

Julian

Hmmmmmmmmmm

Denny

"Paul" wrote in message

Julian Scarfe wrote in message ...
No, no accumulators. The dive was an attempt to get more airflow through
the prop and therefore more lift on the blades helping them to turn as they
unfeathered slightly (or is it less drag as they start to turn?). I don't
have any conclusive evidence that the speed and the restart success were
related, but it "worked".

:-)

From my experience with the Twin Comanche, the feathered position is a
you-beaut, fair-dinkum FEATHERED position and no way known to man would
diving the a/c to Mach 4 to Mach 6 have any effect on the prop/engine.
BUT, because the feathered position did/does require a lot of travel and
wasn't often used, the effect of sludge in the prop cylinder was very
marked....

(I know the PA30 has always had a lot of bad press, but I consider it to be
a very nice little a/c - albeit requiring a considerable amount of
respect............)

RT wrote:

From my experience with the Twin Comanche, the feathered position is a
you-beaut, fair-dinkum FEATHERED position and no way known to man would
diving the a/c to Mach 4 to Mach 6 have any effect on the prop/engine.
BUT, because the feathered position did/does require a lot of travel and
wasn't often used, the effect of sludge in the prop cylinder was very
marked....

Thanks, RT, I was wondering if someone might bring this topic up. In the
Comanche owner's forum I was surprised when a very senior and respected flight
instructor made a comment which I had never considered before. The subject of
discussion was air-restarts and the effect, either beneficial or detrimental,
that an increased airspeed would have on the restart process. In his opinion,
additional airspeed would actually inhibit the restart process (during that
period before the engine had started and the prop started coming out of feather)
because "the prop would have to 'displace' a greater amount of air" or words to
that effect, which was opposite of what I would have thought. My initial
opinion was that since no prop is truly completely feathered - i.e. 82 degrees
is a typical 'feathered' position, and some surface of the propeller airfoil
will always be presented at some angle to the relative wind, more wind would be
better to restart the prop. After all, props want to windmill.

The conversation continued and it was specified that we were talking quite
specifically about the portion of the restart process in which the prop was
feathered, NOT as it started coming out of feather. It was agreed upon by all
that increased airspeed would assist in bringing up the RPM as the prop came out
of feather, but not before (i.e. the initial cranking period prior to engine
start.) This distinction was important in understanding this person's point.

The conversation meandered from that point but I've always wondered since if
diving to increase airspeed would in any way assist in getting the engine
started, assuming of course the prop was fully feathered.

-Ryan
CFII-A/MEI/CFI-H

On Fri, 01 Aug 2003 20:23:49 GMT, Ryan Ferguson
wrote:

snip

The conversation meandered from that point but I've always wondered since if
diving to increase airspeed would in any way assist in getting the engine
started, assuming of course the prop was fully feathered.

snip

Hmmm. If the prop ain't turning, but is aerodynamically (?) on the
verge of turning, a little more airspeed probably wouldn't hurt.

Never really figured how close the angles work out to zero rotational
force, I figured if the force generated wasn't enuff to overide the
cylinder compression, the prop wouldn't turn.

Never shutdown a PT6A in flight, but feathered 'em for fun, in every
case the propeller windmilled, but at a slow rate.

Do know, from experience with un-feathering accumulators (Baron &
Colemill Navajo's) and un-feathering pumps (Beech 18's) that the
visible angle on the propeller blade doesn't change very much before
the engine starts turning over at a fairly rapid rate.

Have air-started a Twin Co and an Aztec (for the heckofit) and it
seemed really, really similiar to the engines I've started with
feathered props on the ground. A lot of shuddering and shaking at low
rpm until the oil pressure in the gov builds enuff to start driving
the prop back to "flat".

Actually, they shudder a lot more on the ground (no "airspeed" to help
accel the engine) but my rectal condition was nowhere near as critical
with the tires sitting on the tarmac.

TC