Pointing into the wind for a run up?
Dallas
I had about 4 instructors tell me to point into the wind during the run up
to keep maximum airflow over the engine's cooling fins.
Suddenly this make no sense to me.
In calm air, run an engine up to 1700 RPM and measure the airflow behind
the prop.
Then set up a fan and blow 40 mph of wind into a prop turning 1700 RPM.
Seems to me the airflow would be the same, the difference would be the less
strain on the engine to turn 1700 RPM.
Comments?
--
Dallas
BT
2000 rpm..
the rest of the time, you are at idle or about 1000rpm or lower while you
complete the rest of the checklist, configuration checks, radio set up etc.
and the engine is not getting adequate cooling
One flying club I was at was at the south end of a 2 mile long runway, and
tower did not approve intersection departures. So with a south wind it was a
2 mile taxi, in hot conditions with tail winds in a tightly cowled Mooney.
Had to watch the temps during taxi, and more than once turn around to face
the wind at the half way point to get the engine temps back down. Also had
to face the winds at the departure end for a while, to get the temps back
down before starting the take off, which of course would help immensely.
BT
"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
news:81aq62znbpwp.1s...@40tude.net...
Mark Hansen
In addition to the other response you got, I was told that on a typical
C172 trainer, not much of the prop wash is directed into the cowling, so
the breeze you feel from behind the plane while the engine is turning
at 1700 RPM is not the same as what you would feel if you were in the
engine compartment.
However, this is just what a local instructor told me - I don't know if
it is true.
--
Mark Hansen, PP-ASEL, Instrument Airplane, USUA Ultralight Pilot
Cal Aggie Flying Farmers
Sacramento, CA
Bob Gardner
portion in front of the air intake ports. Not of heck of a lot of air is
moved at that point. Your fan analogy is faulty.
Bob Gardner
"BT" <bNO...@SPAM.cox.net> wrote in message
news:IrH_j.1805$BK1....@newsfe17.phx...
Bob Gardner
Dallas.
Bob Gardner
"BT" <bNO...@SPAM.cox.net> wrote in message
news:IrH_j.1805$BK1....@newsfe17.phx...
Dan_Thom...@yahoo.com
> In addition to the other response you got, I was told that on a typical
> C172 trainer, not much of the prop wash is directed into the cowling, so
> the breeze you feel from behind the plane while the engine is turning
> at 1700 RPM is not the same as what you would feel if you were in the
> engine compartment.
>
> However, this is just what a local instructor told me - I don't know if
> it is true.
It's true. The propeller's blades near the hub have a high
pitch and are pretty much stalled when the airplane isn't moving, so
little air is moving through the engine compartment. Running up with
the tail to any significant wind will result in higher CHTs.
The short-field takeoff technique involves standing on the
brakes while running the engine at full throttle, and leaning to max
RPM before releasing the brakes. The CHTs can get really high during
this operation, in spite of all that wind past the cowling. This sort
of runup should be kept as brief as possible.
See this: http://www.fortlangleyair.com/docs/Cowl%20Flaps%20and%20Engine%20Cooling.pdf
Dan
BT
as a fan
BT
"Bob Gardner" <bob...@comcast.net> wrote in message
news:wtOdneQ4fs-o1abV...@comcast.com...
Steve Foley
news:IrH_j.1805$BK1....@newsfe17.phx...
> One flying club I was at was at the south end of a 2 mile long runway, and
> tower did not approve intersection departures
Was there a good reason for this policy?
Mark Hansen
> On May 26, 5:16 pm, Mark Hansen <m...@NOSPAMwinfirst.com> wrote:
>
>> In addition to the other response you got, I was told that on a typical
>> C172 trainer, not much of the prop wash is directed into the cowling, so
>> the breeze you feel from behind the plane while the engine is turning
>> at 1700 RPM is not the same as what you would feel if you were in the
>> engine compartment.
>>
>> However, this is just what a local instructor told me - I don't know if
>> it is true.
>
> It's true. The propeller's blades near the hub have a high
> pitch and are pretty much stalled when the airplane isn't moving, so
> little air is moving through the engine compartment. Running up with
> the tail to any significant wind will result in higher CHTs.
Incidentally, the flying club of which I am currently a member has a policy that
you should point the airplane toward the approach area of the runway. When I tried
to point the plane into the wind, I was chastised and told that the need to point
into the wind during the run-up was an old wive's tale :-(
> The short-field takeoff technique involves standing on the
> brakes while running the engine at full throttle, and leaning to max
> RPM before releasing the brakes. The CHTs can get really high during
> this operation, in spite of all that wind past the cowling. This sort
> of runup should be kept as brief as possible.
>
> See this: http://www.fortlangleyair.com/docs/Cowl%20Flaps%20and%20Engine%20Cooling.pdf
>
> Dan
Thanks for the link. I'll pass it along to the club's chief pilot.
gatt
> On 05/26/08 17:22, Dan_Thom...@yahoo.com wrote:
>> On May 26, 5:16 pm, Mark Hansen <m...@NOSPAMwinfirst.com> wrote:
> Incidentally, the flying club of which I am currently a member has a policy that
> you should point the airplane toward the approach area of the runway. When I tried
> to point the plane into the wind, I was chastised and told that the need to point
> into the wind during the run-up was an old wive's tale :-(
Portland-Troutdale Airport has a sign that says "Orient aircraft west
during run-up," but the "old wive's tale" is also a question on the CFI
Written Exam, and, presumably, might come up in a checkride.
-c
Mark Hansen
The funny thing about the requirement by the club to point toward the approach
area is that they also require you to do a 360 on the ramp just before taking
the runway - to look for traffic. Also, while doing the run-up, I'm not really
looking for traffic - I'm going down my checklist, etc. Weird.
Robert M. Gary
I was taught this too. I have an EDM in my Mooney and never noticed a
difference in CHT's either way. Perhaps its more of an issue for J-3s.
In anycase, I orient my runup to see planes on final. In the J-3 it
was easy to do a 360 but the Mooney takes more space than available to
do an actual 360.
-Robert, CFII
Barry
> that
> you should point the airplane toward the approach area of the runway.
I usually orient my plane to minimize the effect on others:
- don't blow my prop wash where other planes might be
- allow room for others to pass (though not always possible with narrow
taxiways).
The best way to accomplish this is usually by pointing 30-45 degrees toward
the runway. For example, for runway 36, if the taxiway is on the west (left
turn onto the runway) I'll do my runup pointing northeast, and positioned as
far back as possible towards the approach end of the runway. This allows
other planes to pull up next to me (on my left) and do their runups, pointed
in the same direction, without getting hit by my prop wash. This position
also leaves maximum space for others to pass, allows a view of final approach,
and will often be into the wind as well.
BT
A Good enough reason?? yes. It was a military base and they said so.
There was one cross taxiway at the mid field point. And they said no
intersection departures.
So when we were landing to the south.. we did not touch down until the last
3rd of the runway.
BT
"Steve Foley" <steve...@att.DELETE.net> wrote in message
news:D5T_j.3115$3f1.1567@trndny02...
Dallas
wrote:
> It's true. The propeller's blades near the hub have a high
> pitch and are pretty much stalled when the airplane isn't moving, so
> little air is moving through the engine compartment.
Myth not busted?
:- )
Thanks
--
Dallas
Dudley Henriques
It's not written in stone, but a runup is simply done better into the
wind whenever possible rather than as a firm rule. The theory is that
ANY cool air through an engine during a runup is better than not having
that air at all.
The trick with runups is that they should be done both correctly and
with minimum time involved.
My runup in the Mustang lasted about 30 seconds. You can do a proper
runup in a Cessna 150 for example in even less time.
No need for extended periods of power if runups are carefully planned
and executed with a well pre-planned cadence.
--
Dudley Henriques
Hilton
> It's not written in stone, but a runup is simply done better into the wind
> whenever possible rather than as a firm rule. The theory is that ANY cool
> air through an engine during a runup is better than not having that air at
> all.
> The trick with runups is that they should be done both correctly and with
> minimum time involved.
> My runup in the Mustang lasted about 30 seconds. You can do a proper runup
> in a Cessna 150 for example in even less time.
> No need for extended periods of power if runups are carefully planned and
> executed with a well pre-planned cadence.
There are numerous occasions where a runup (or at least being in the runup
area) can take a lot longer than 30 seconds; e.g. need to clean the mags,
giving/receiving instruction, copying a clearance, getting charts for said
clearance, waiting for IFR release, troubleshooting a problem... All pretty
common. Granted, the engine won't be near full power, but some
manufacturers recommend an RPM quite a bit above idle.
Hilton
Dudley Henriques
could take longer than 30 seconds to say the least, but engine run up
should only be considered in the context of the time frame required for
checking out the engine(s) and everything else that requires power above
idle. The rest of it are simply procedures done in the run up area. :-)
--
Dudley Henriques
Chris Colohan
I'm currently doing my IFR training in a Cessna 172SP. I have noticed
that every single time I start the engine and taxi to the runup area,
the plugs are fouled when I do the mag checks. As a result I always
have to do an extended runup to burn off the lead. Leaning the engine
(no matter how much) before taxi doesn't seem to matter...
Does this mean that:
a) something is wrong with the engine
b) some engines are just finicky this way
c) the other renters are forgetting to lean before taxiing back to
parking
d) I'm doing something wrong
...?
Chris
BT
and
e) you are leaving the mixture too rich while taxing..
this is especially true at higher DA airports.
B
"Chris Colohan" <colo...@cs.cmu.edu> wrote in message
news:ucly75uc4...@tretiak.stampede.cs.cmu.edu...
Dan_Thom...@yahoo.com
> With all this talk about runups...
>
> I'm currently doing my IFR training in a Cessna 172SP. I have noticed
> that every single time I start the engine and taxi to the runup area,
> the plugs are fouled when I do the mag checks. As a result I always
> have to do an extended runup to burn off the lead. Leaning the engine
> (no matter how much) before taxi doesn't seem to matter...
>
> Does this mean that:
>
> a) something is wrong with the engine
Could be. It's a Lycoming, which doesn't usually have the oil-
fouling problems that the smaller Continentals often display, but if
the rings are worn some there might be enough oil sucking past them
that the bottom plugs get wet and will misfire until a full-throttle
runup clears them. Another factor is the typical requirement that
sparkplugs get cleaned and checked every 100 hours, which isn't often
enough for many engines. The plug's cavity fills with lead byproducts
and the electrodes get shorted out. A full-power runup might burn off
just enough of the crud that the engine will run OK, but the little
bit of further fouling that occurs during the flight brings the
problem back for the next guy. We find that we have to do the plugs
every 50 hours and get LOTS of lead in that time, especially if the
airplanes are in the circuit a bunch. Sometimes chunks of it fall out
when the lower plugs are pulled. The smaller Lycs (O-235) will foul
their plugs in 25 hours of circuit work, as will the derated O-540s,
since those tend to run really rich at low throttle settings. Both
Champion and Unison make the U/REM37BY plug for engines that suffer
lead fouling; those plugs have extended electrodes that keep them much
cleaner. See http://www.sacskyranch.com/combustionClean.htm and
scroll down to the second picture. The caption has the plugs
backwards; the REM37BY is on the left.
>
> b) some engines are just finicky this way
Yup. But more frequent plug cleaning is the solution.
>
> c) the other renters are forgetting to lean before taxiing back to
> parking
Wouldn't make a lot of difference.
>
> d) I'm doing something wrong
I doubt it, unless it's renting from an outfit that hates to
spend what it should on maintenance.
Dan
Gezellig
wrote:
> Could be. It's a Lycoming, which doesn't usually have the oil-
> fouling problems that the smaller Continentals often display, but if
> the rings are worn some there might be enough oil sucking past them
> that the bottom plugs get wet and will misfire until a full-throttle
> runup clears them.
Dan, would you see this in the color of the exhaust?
Dan_Thom...@yahoo.com
> On Wed, 28 May 2008 19:33:33 -0700 (PDT), Dan_Thomas_nos...@yahoo.com
> wrote:
>
> > Could be. It's a Lycoming, which doesn't usually have the oil-
> > fouling problems that the smaller Continentals often display, but if
> > the rings are worn some there might be enough oil sucking past them
> > that the bottom plugs get wet and will misfire until a full-throttle
> > runup clears them.
>
> Dan, would you see this in the color of the exhaust?
Maybe just the tiniest bit of blue when the throttle is opened. At
idle the cylinder pressures are so low on the intake stroke that oil
gets pulled past worn rings into the combustion chamber and will lay
in the bottom and run into the bottom plug and drown it. Opening the
throttle wide makes more fire and turbulence and heat and will burn
that stuff out. It's much more of a problem in small Continentals than
it is in the Lycomings. That 172P has a Lyc in it. I would bet that
your problem is lead-fouled plugs that aren't getting changed out
often enough.
Dan
st...@here.com
>how much of the time during the run up are you really turning 1700 or even
>2000 rpm..
>the rest of the time, you are at idle or about 1000rpm or lower while you
>complete the rest of the checklist, configuration checks, radio set up etc.
>and the engine is not getting adequate cooling
>
>One flying club I was at was at the south end of a 2 mile long runway, and
>tower did not approve intersection departures. So with a south wind it was a
>2 mile taxi, in hot conditions with tail winds in a tightly cowled Mooney.
>Had to watch the temps during taxi, and more than once turn around to face
>the wind at the half way point to get the engine temps back down. Also had
A few years back on very slow taxi from (basically the safety shack by
the homebuilder's center) to 27 with a light tail wind and about 97
degrees I had to ask the tower to turn into the wind as the engine was
starting to run rough. I suspect it was vapor lock rather than
detonation, but they cleared me for immediate departure with my
clearance to come later. If it had hiccupped on the roll I'd have
aborted, but as soon as we started moving toward the runway with more
power it smoothed right out. Man, but that was a hot ride. On the
taxi the right seater held the door nearly wide open with their foot.
IIRC it was still around 80F at 7,000. We crossed the lake at 8000
Eastbound where it was a chilly 76<:-)). No that's not a misprint.
Center asked if I'd accept a climb to 8000 for traffic avoidance.
There was a Bo southbound at 7000 who passed directly under us just as
we reached 8000. We stayed at 8000 until starting our descent into
3BS.
>to face the winds at the departure end for a while, to get the temps back
>down before starting the take off, which of course would help immensely.
>
>BT
>
>"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
>news:81aq62znbpwp.1s...@40tude.net...
>>
>> I had about 4 instructors tell me to point into the wind during the run up
>> to keep maximum airflow over the engine's cooling fins.
>>
>> Suddenly this make no sense to me.
>>
>> In calm air, run an engine up to 1700 RPM and measure the airflow behind
>> the prop.
>>
>> Then set up a fan and blow 40 mph of wind into a prop turning 1700 RPM.
>>
>> Seems to me the airflow would be the same, the difference would be the
>> less
>> strain on the engine to turn 1700 RPM.
>>
>> Comments?
>>
>>
>> --
>> Dallas
>
Roger (K8RI) ARRL Life Member
N833R (World's oldest Debonair)
www.rogerhalstead.com
st...@here.com
>> Incidentally, the flying club of which I am currently a member has a policy
>> that
>> you should point the airplane toward the approach area of the runway.
>
>I usually orient my plane to minimize the effect on others:
>
>- don't blow my prop wash where other planes might be
>- allow room for others to pass (though not always possible with narrow
>taxiways).
>
You almost always can turn at a slight angle.
However I've always figured "Prop Wash" was natures way of chastising
aviation "tail gaters"<:-))
>The best way to accomplish this is usually by pointing 30-45 degrees toward
>the runway. For example, for runway 36, if the taxiway is on the west (left
>turn onto the runway) I'll do my runup pointing northeast, and positioned as
>far back as possible towards the approach end of the runway. This allows
>other planes to pull up next to me (on my left) and do their runups, pointed
>in the same direction, without getting hit by my prop wash. This position
>also leaves maximum space for others to pass, allows a view of final approach,
>and will often be into the wind as well.
>
st...@here.com
Even in the Deb it's less than 30 seconds. That includes doing
everything and then checking it against the written checklist. It's
even faster if the right seater is a pilot who can read off the check
list. We have one plane at the airport (new one too) that the rest
of us try to avoid as it may take them 5 to 10 minutes of checks
before pulling out onto the runway. It's a snug fit down there and
they get excited when you pass with 10' of wing overlap. <:-))
comanche driver
R. Burns
Robert M. Gary
> for some of us it keeps the tail where it belongs, on the ground.
Yea, I hear that is a big problem for Commanche's ;)
-Robert
comanche driver
"Robert M. Gary" <N70...@gmail.com> wrote in message
news:fef0f40e-548c-4525...@j33g2000pri.googlegroups.com...
-Robert
so sorry, i forgot not everyone has a work airplane and a play airplane. My
RV-4 has the wheels where they belong. :)
R. Burns
Dan_Thom...@yahoo.com
> In calm air, run an engine up to 1700 RPM and measure the airflow behind
> the prop.
>
> Then set up a fan and blow 40 mph of wind into a prop turning 1700 RPM.
>
> Seems to me the airflow would be the same, the difference would be the less
> strain on the engine to turn 1700 RPM.
1700 isn't an arbitrary figure. Blowing 40 mph of wind
through the prop would reduce the load on the engine at 1700,
defeating the main purpose for selecting that particular RPM.
The engine manufacturer works with the airframe
manufacturer to determine the best runup setting. In your case, 1700
will give the highest cylinder compression pressures, and checking the
mags at that RPM will give them the most opportunity to fail to spark,
which is what a mag check is all about. Air is a dielectric, an
insulator, and higher cylinder pressures pack more of it between the
electrodes and eventually a bad plug (or bad mag) can't arc through
it.
Higher than 1700 results in more induction system drag,
less volumetric efficiency, and less air entering the cylinder,
lowering its ultimate compression pressure. Lower than 1700 will have
the throttle closed more, again reducing airflow into the cylinder.
We have a Citabria 7ECA that has the O-235 in it. Its
runup RPM is 1800. My old A-65 gets its highest pressures around 1600.
1700 was picked for your engine, and running up into a really strong
wind could reduce the load enough that you'd have the throttle closed
a bit, but POHs don't mention that. I guess they figure that you won't
be flying in any wind strong enough to make a difference.
Dan
rue_b...@yahoo.com
>
> Portland-Troutdale Airport has a sign that says "Orient aircraft west
> during run-up," but the "old wive's tale" is also a question on the CFI
> Written Exam, and, presumably, might come up in a checkride.
>
> -c
I just took a checkride and the examiner told me that it was an old
wives' tale.
Dan_Thom...@yahoo.com
> I just took a checkride and the examiner told me that it was an old
> wives' tale.
This document...
http://bridgesaviation.com/ground_operations.htm
Has this to say about it:
"Face the aircraft into the wind only if the engine temperature(s)
require the additional cooling."
There are engine installations that need it. The problem with an
examiner telling a student that "it's an old wives' tale" is that the
examiner is a pilot, one who may never have flown some tightly-cowled
high-powered engines, so he thinks it isn't a problem anywhere. He is
not an engineer or mechanic, the sort of guy who has to deal with
engines abused by pilots. I am both a pilot and mechanic, and get to
fix the things pilots break, and I know how they broke them. Pilts who
have never bee taught that it's good practice to point into the wind
right from the first lessons might ultimately shorten the life of an
expensive engine.
Dan