Oil pressure gauge

[wingman1]

Was wondering if someone could help me out here.....I have a contradiction between two text books on the same subject. On the subject of the oil pressure gauge, one text is telling me in cold wx, it's best to let the engine run from anywhere between 30 secs. to 1 min. the other said anywhere up to 15 mins., 15 mins seems a little excessive to me....that's quite a bit of fuel just to let the oil pressure flow correctly.
Thanks

[200hr Wonder]

Not too sure what you are asking, however in cold WX remember that your oil has seeped down to the bottom of the sump. When it is cold it is thicker, and will take a while to lubricate the top end of the engine. First thing to worry about is on start up if you do not have oil pressure at between 20 and 30 seconds shutdown the engine something is wrong. If it is warm out or has just run your oil pressure will come up much much faster. The second is before applying any amount of throttle you want to be sure that the oil has heated up to the proper operating temperature to ensure good lubrication of the moving parts. This can take up to 15min. Now sure if you add throttle it will heat the oil up that much faster, DO NOT DO THIS. It is extremely hard on the engine wait till the temp is up well into the green before taxiing and at normal operating temperatures before taking off.

Additionally while in flight keep an eye on the gauge to ensure that it is not rising. On none graduated gauges I like to site the gauge in reference to something. Most will say Oil Temp or similar. Then you can look, normal cruise is the e int Temp climb is the second bump on the m and so forth. Helps to know when your Temp/Pressure have gone south.

[Hedley]

In the Bad Old Days (tm) when everyone used straight-grade
oil, you had to worry about oil temp before takeoff. If you
didn't, it was possible to have excessive oil pressure - the
cold oil was too thick to flow.

However. These days EVERYONE should be running a
multiviscosity oil in the winter, in their piston aircraft
engine. Aeroshell 15w50 and Philips 20w50 are examples.

With these oils, you actually don't need oil temps "in the green"
before takeoff, because they will flow perfectly well when
they are cold. They are multi-viscosity oils, after all.

When you start a cold engine, try not to immediately
run the RPM up, to avoid scuffing the pistons. 1000 RPM.
I wait until I see at least 200F CHT before I will do the
runup at 1700 RPM. Generally it is no problem, after that,
to get 250F to 300F CHT for takeoff. With multi-viscosity
oils, you DON'T need to sit and idle and wait for the oil
to warm up into the green (eg 100F). CHT is what matters.

[B-rad]

On none graduated gauges I like to site the gauge in reference to something....normal cruise is the e int Temp climb is the second bump on the m and so forth. Helps to know when your Temp/Pressure have gone south.

Can you explain this a little more. or maybe in different words. I think I understand what your getting at but your explanation has me re-re-reading it to understand what your saying.

[deflux]

He is saying that during normal cruise if you look at the needle on the gauge, try and reference something to where it is pointing.

For example, if its pointing at the "T" in Oil Temp then you can use that for future reference to make sure it is at it's normal temp.

[trey kule]

I think the original poster inquired about oil pressure.

Normally, you will get oil pres within a few seconds of start. If oil is really cold you will find the oil pressure initially low , and then going to very high. What you want from an oil pressure guage is the oil pressure to be pretty much normal and not moving to the top of the high side when you advance the throttle. As to warm up time, I think that if you contact the tech dept of the engine manufacture you might get some different advice than you are getting here. I have been advised by one manufacturer that they like to see their engines idle for a minimum of 5 mins on the first start of the day and, depending on the ambient temp, a minimum of 2 mins on any start...(just as an aside, if you are a student pilot, if the plane does not move, you are not logging flight time during this phase and should not be getting charged for it...those little hobbs meters do not record flight time). Engine manufacturers put out some interesting info as do companies like Tanis...go online

Some piston engines, particularly radials, specifically do not call for RPM at 1000 when the oil is very cold. Dont take the general advice you are getting here as advice specific to a particular engine.

As far as Temps/CHT, again, some engines call for the oil temp to be in the green..some dont.
It is a good idea, as always, to learn the specific requirements of the particular engine type you are flying.

Now, a bit off the topic, but why in the heck are you starting up a cold engine anyway? The cost of systems like Tanis, even an engine tent and a car interior heater, or a portable lil devil heater will save immense wear and tear on your engine starts. I realize there are times when we get caught, but extreme cold starts should be considered a very unusual situation.

[Hedley]

Some piston engines, particularly radials, specifically do not call for RPM at 1000 when the oil is very cold

Of course, TK! But not many people learn
to fly on R-985 or R-1340 these days

However, for the sake of completeness, just
in case there is anyone doing their ab initio
flight training on say a Harvard, and their
instructor forgot to ever mention it ... (!!!)

How you start a radial engine is with absolute
minimum RPM for at least 5 - 10 minutes after
cold start, depending upon the temperature.

Just barely ticking over, using the huge metal
prop as a flywheel. If you do not, you will
surely find aluminum in the oil! I know a guy
who recently did this. A real impatient fellow,
he liked to jump into his T-28 and start it
and immediately taxiied it off, just like his
car. Trashed the engine, but he didn't really
care - he had enough money, that it was worth
his time to change the engine frequently.

The warbird community is filled with all
sorts of bizarre characters. Sometime I'll
tell you about Tom Cruise flying his P-51

[cgzro]

The warbird community is filled with all
sorts of bizarre characters. Sometime I'll
tell you about Tom Cruise flying his P-51

I think that goes for the Pitts flying community too eh Hedly as I recall Mr Cruise ALSO owns a Pitts and I can think of one or two other colorful characters that fly them!

Peter (in Shenzhen China where there is not a GA plane in the sky Pitts/P-51 or otherwise)

[trey kule]

Hedley, that is so correct. I never included it in detail because the point I was trying to make was that general rules are fine, but you should know your specific engine requirements. Did not know we were talking about ab initio pilots here.

Perhaps I should have been more complete. Besides the oil pressure, there is also the oil temp and the CHT. They should be looked at in total on a warmup, and the decision to begin the taxi should be based on the combined readings. CHT is important, for example, but if you are getting restricted oil flow due to viscosity issues, the CHT's can seem normal but are really an indication of poor lubrication, particularily when power is increased. Just my thoughts on engine care..

As to the guy firing up a radial and starting to taxi..good that no one else is climbing in the plane after him believing the engine has been treated right.

[Hedley]

if you are getting restricted oil flow due to viscosity issues

That's certainly possible if you're running straight-grade
in the winter - a VERY poor choice - but I'm not sure that's
ever going to be a problem with modern, multi-viscosity oil,
which flows superbly at low temperatures.

See, with straight-grade oil, you DO need to get the temp up
for it to thin out and flow properly. But multi-grade flows
just fine when it's cold, so you don't need to worry about
using the oil temperature as a proxy for oil viscosity, with
multi-grade oil.

Don't get me wrong, I love straight-grade w100 and w120
in the summer. But NOT in the winter!

the guy firing up a radial and starting to taxi

You should have heard his after-fires of unburned gas,
out the exhaust, from advancing the throttle too early!

[MichaelP]

I think the T28 is probably the ugliest 'warbird' money can buy. It's an example of showing off how much cash one can put through the fuel and oil systems!

The Katana's run on multi viscosity synthetic oil, we use Mobil 1. On no account should 'aviation' oil be put into the Rtoax engine... It's the difference between motor technology and aviation technology!
We always warm these engines into the green arc before flying.

The -C1 is different. We need the front winterisation baffles for most of the year in the lower mainland... Sometimes it's a problem because of the common 'inversion' in the air above the valleys.
Take them out and the aeroplane comes back because the oil temperature drops well below the green even if it was green on the ground. The CHT in this situation never gets to the green. It's not good training when things are often not green!
Leave the winterisation baffles in and you risk too high an oil temperature while the CHT is happily in the middle green if a continuous climb is made to altitude (4,500 feet or more).
Baffles in or out gives me a lot of headaches!
I understand another school modified their baffles by drilling some holes to be in between what we have and no baffles at all.

The aeroplane that previously gave me concern was the Cessna 206... In the hot summer weather, climbing, the oil temp goes to the red line and sticks there. I lower the nose go for over 100 knots and still it sticks. I was told this is normal.
I worried all the way to Manning Pass when I finally made it to 5,500 feet. In retrospect I should have climbed above Okanagan Lake BPOC.

It's amazing how we simply accept 'abnormal' as being normal for certain aircraft!

The Bucker Jungmann I flew did not have an oil pressure gauge at all!

up to 15 mins., 15 mins seems a little excessive to me....that's quite a bit of fuel just to let the oil pressure flow correctly.

15 minutes waiting for the oil pressure to rise is far too long!
30 seconds is normal, and a minute is too long for any engine we are likely to fly these days, IMHO.
With the Katanas in the very cold the oil pressure rises to the high yellow after start and the comes back into the green as it warms up.

[iflyforpie]

The aeroplane that previously gave me concern was the Cessna 206... In the hot summer weather, climbing, the oil temp goes to the red line and sticks there. I lower the nose go for over 100 knots and still it sticks. I was told this is normal.
I worried all the way to Manning Pass when I finally made it to 5,500 feet. In retrospect I should have climbed above Okanagan Lake BPOC..

This is not normal for a 206. We climb 90kts full load from 3,000 to 10,000 on the hottest summer days and the oil temp never even gets close to red line. CHT sometimes needs attention to keep it under 400, but that is it.

[Hedley]

It's not surprising that an aircraft many decades old might
run hot ... the baffles and seals, over time, have probably
deteriorated and have not been (correctly) repaired.

If the aluminum baffles and seals are not in good shape,
they can allow the incoming air (at the top of the flat
engine) to leak down through all the holes, instead of
being forced past the cylinders and oil cooler.

Also, perhaps the vernatherm is not functioning correctly,
and perhaps the oil cooler is (at least partially) blocked
with sludge, and isn't flowing as well as it could. It's
possible there's even some aluminum tape over the
oil cooler air inlet - some pilots do that in the winter, to
try to get their oil temperature up. But it needs to
be removed for the summer, just like a real winterization
kit.

Oil temp at redline is NOT something to be ignored!

If you run very high oil temps (eg in excess of 220F)
consider decreasing your oil change intervals, and
running at least straight grade 100 (sae 50) or even
straight 120 (sae 60).

[cyxe]

The warbird community is filled with all
sorts of bizarre characters. Sometime I'll
tell you about Tom Cruise flying his P-51

Do tell. (not to sidetrack the thread, but I am curious)

[Tim]

when i was a student our flight school ruined 6 of our 9 cam lobes from high rpm starts one winter (thankfully i did not contribute). of the 6 lobes on the cam shaft, 2 did double duty. those 2 lobes had been rubbed down significantly. 20 grand x 6, plus all the down time made people learn their lessons. its just those first few crucial seconds following start up, once its running oil will spread around pretty quickly.

people seem to think that pushing the throttle further and further up while cranking the engine makes it start easier.

another little story about a guy that has the nickname 'dr death'. in the winter he starts up his cherokee which sits outside for weeks between flights. he doesnt clean the wings (INCHES of snow/ice, but dont worry "it'll just blow off during take off"). he fires up, skips the runup and is airborne in under 2 minutes...incidently he's crashed several a/c.

[Hedley]

our flight school ruined 6 of our 9 cam lobes from high rpm starts one winter

Sigh. I cringe when I hear someone cold start an aircraft
engine, and it roars up to 1700 RPM right away

pushing the throttle further and further up while cranking the engine makes it start easier

urgh. I will probably be attacked for letting this secret out
of the bag, but ... the hand-pump primer on small, flat
carbureted engine rarely puts fuel into all cylinders. Often
just one cylinder gets the primer fuel, and that's not good.

The thing to remember is that carburetors on flat aircraft
engines are UP-DRAFT ... so, if you pump the throttle, and
the engine isn't running, the fuel from the accelerator pump
will run down into the carb heat flapper box, and create quite
a fire hazard. That's not good, either.

However. If you pump the throttle when air is going (up)
through the carburetor, the intake manifold does a very
nice job of distributing the combustible air/fuel mixture
to all cylinders.

So. I didn't tell you this, but if you are cranking the engine,
air is indeed going into and up the carburetor. Think about it.

he's crashed several a/c

I'm sure he's in "good standing" with Transport

[Tim]

i was thinking fuel injected engines when i said dont push the throttle up (im right, right?)

good point with the carb'ed engines though. i like the use of the word 'pump' though. as in dont leave the damn throttle up there!

[tiny]

However. These days EVERYONE should be running a
multiviscosity oil in the winter, in their piston aircraft
engine. Aeroshell 15w50 and Philips 20w50 are examples.

To bad Continental won't warrenty an engine that has run 15W50. Continentals, in my experiance, run better with straight grade anyway.

Lycoming on the other hand loves 15W50.

Tiny

[MichaelP]

If you pump the throttle when air is going (up) through the carburetor, the intake manifold does a very
nice job of distributing the combustible air/fuel mixture to all cylinders.

My goodness I am close to swearing...
Don't pump the throttle on any of my engines this is totally unnecessary.

There's an instructor on the field who teaches all his students to pump the throttle!
This means I have to teach them to do it properly and I hate reteaching and trying to cure a bad habit!
I have never in my thirty five years ever resorted to this stupidity and rarely has an engine not started for me.

Here's another thing... Don't open the throttle at all! Let the idle jet do it's thing; this often works with a hot engine.

In very cold weather, prime, and suck the mixture into the cylinders by hand, throttle closed, mixture idle cut off, magnetos off, check again; throttle closed, mixture idle cut off, magnetos off, wheels chocked/aircraft tied down, and treat the prop live!

If an engine needs the throttle to be pumped in order for a successful start there's something very very wrong with it and you'd better see the mechanic right now.

I'm sorry, but I have NEVER NEVER NEVER seen the need to pump a throttle on any of the common and obscure engines I've flown.
It's a wan*er's habit I suppose

[Hedley]

Sorry, Mike, I knew that letting that out of the bag would
piss some people off

The problem is, that done correctly, it works very well.

Do keep in mind that the hand primer pump on flat
engines may only put fuel in ONE cylinder. The other
cylinders don't even get any fuel. So, you're trying
to start an engine with just ONE cylinder.

You might be able to get away with that in England
or British Columbia, or Thailand, where you don't need
to ever wear long pants, but the reality is that when it
gets cold, many engines simply will not start unless
there is fuel running onto the ramp below. 100LL
simply doesn't evaporate as quickly as winter mogas,
and that makes it worse.

Yes, that's a fire hazard. Yes, there's a reason that
the military always required someone on a fire extinguisher
during a piston start.

I would agree that for many people, it would be best
if they refrained from committing aviation when the
surface temp drops below zero C.

[iflyforpie]

I'm sorry, but I have NEVER NEVER NEVER seen the need to pump a throttle on any of the common and obscure engines I've flown.
It's a wan*er's habit I suppose

+2. The only time I needed to pump a throttle was on a Cherokee 140 I flew that the O-rings in the primer decided to go when I was in the middle of nowhere. It was a bitch to start and I rebuilt the primer as soon as I got home.

Most primer systems go to more than one cylinder. On a typical O-320, three of four cylinders have a primer. The O-300 has only one primer nozzle, but it is in the intake manifold and splits to three cylinders. The O-470 has primer nozzles in all cylinders. The R-1340 I worked on had three cylinder with a primer nozzle that would not only get the engine started on a -20C Calgary winter day, but keep it running after putting the mixture to ICO if the primer wasn't quite locked.

Pretty much all carburetors have an accelerator pump which does shoot extra fuel into the engine. But at cranking RPM it is very difficult for this fuel to get all the way from the carburetor to the cylinders and it will usually collect on the manifold walls and drip back down to the airbox. This pooled fuel is great for catching fire should there be a backfire.

Though I would argue against MichaelP saying the idle jets and nozzles are sufficient (they aren't usually, which is why we crack the throttle on start up) I definitely agree with not pumping the throttle.

[Hedley]

On a typical O-320, three of four cylinders have a primer

uh, no. I have seen 4-cyl Lycoming factory installations
with either one, two or three cylinders fed by the primer,
and the most common I see is one, max two cylinders.

A friend of mine has a 172, he had to change the cylinder
that had the ONE primer line fed to it, because the gas
washed all the oil off the cylinder walls and it scuffed. That
worked really well for him, didn't it?

I just had a conversation last week with a guy who builds
Lycoming engines for homebuilts, he only plumbs two
cylinders from the primer

[iflyforpie]

Every Lycoming 172 I've seen has three cylinders primed. But I guess 172s with O-320s aren't all that common.

Your friend wasn't using mogas was he? Combined with over priming it's a good recipe for scuffed cylinders. A few bucks for some extra primer nozzles and tubing would probably mean he would have to prime as much and offset the cost of a new cylinder.

[Hedley]

A few bucks for some extra primer nozzles and tubing would probably mean he would have to prime as much and offset the cost of a new cylinder

Sure, but that's not what he has, and he'd probably need
an STC for the mod, so that's never going to happen.

Those hand primers are so mickey mouse. They can leak
fuel into your hand, they can plug up and take enormous
pressure to depress, they don't feed all cylinders, etc. Yuck.

Don't get me wrong - an electric boost pump on a
fuel injected engine, that feeds all the cylinders, is
a great way to prime.

[iflyforpie]

On a 172, the installation is standard (like I say, I've never seen one without three cylinders plumbed) so you don't need an STC, you are installing approved parts to what the book already says.

I hate primers too. But I've never had a problem starting any carbureted engine with using one. Fuel injection is better in some ways provided you know what fuel flow/pressure to go to for which temperature you are starting.

But I've spent more time battling a hot start on a fuel injected engine than a carbureted one; and for fear of flooding I am usually pretty lean on the priming in cold weather so it sometimes takes a couple tries there too. My 172, starts first time, every time.