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How much engine warming before take off?

T

Ted Radclyffe

Active Member
A general question....
At a recent fly in, there was a lecture on oil additives and the clear message was that the additives did not start to work (particularly on the rockers and cams) until the oil temperature was well and truly in the working (green) range. There was also most wear caused at low engine temperatures.
The question was asked that if this were so, was it not better to load the engine sooner rather than later I.e. don't needlessly warm the engine as it won't come up to temperature until it is under power. There were two schools of thought on this. One was that it was unsafe to load the engine 'till it was well toward the green. The other was to get the plane into the air as soon as the temperature gauge was moving into the yellow.

A chopper fleet owner said that as soon as the temperature gauge moves into the yellow, the manufacturers instruction was to put the engine under power. This saved both in terms of engine time and wear.

I am not talking about taking the engine from freezing temperatures but, assuming the ambient air temperature is say 20 degrees C ( 68F) then it only takes a few minutes to get the temperature into the yellow arc. and it achieve the green during the first minute or so of climb.

I have to say that the oil supplier commented that there was justification for the two scenarios but would not venture an opinion either way.

Is there some definitive wisdom to be shared?

Ted
Rough Red RV-6A
 
From the operator's guides...

Ted,

My O-360 Lycoming manual says...

5. GROUND RUNNING AND WARM-UP
The engines covered in this manual are air-pressure cooled and depend
on the forward speed of the aircraft to maintain proper cooling. Particular
care is necessary, therefore, when operating these engines on the
ground. To prevent overheating, it is recommended that the following
precautions be observed.
a. Fixed Wing.
(1) Head the aircraft into the wind.
(2) Leave mixture in "Full Rich".
(3) Operate only with the propeller in minimum blade angle setting.
(4) Warm-up to approximately 1000-1200 RPM. Avoid prolonged
idling and do not exceed 2200 RPM on the ground.
(5) Engine is warm enough for take-off when the throttle can be
opened without the engine faltering. Take-off with a turbocharged
engine should not be started if indicated lubricating oil pressure,
due to cold temperature is above maximum. Excessive oil pressure
can cause overboost and consequent engine damage.

Interestingly enough, no actual numbers are given....:confused:

The Superior Vantage manual is similar, but gives a number...

8. Engine is warm enough for take-off when the oil temperature exceeds 75? F and the engine does not hesitate with throttle advancement.

My Tiger does not have a yellow area at the bottom of the OT scale, the green starts at 75F.

Vantage quotes these numbers....

Table 9 ? Oil Temperature Limits
Minimum for Take-off 75?F
Maximum Allowable 240?F
Recommended Cruising 130?F - 200?F

I would read this as
Green .......75F to 200F
Yellow .....200F to 240F
Red Line ...240F

gil A
 
Minimize ground idle

az_gila said:
(5) Engine is warm enough for take-off when the throttle can be
opened without the engine faltering.
gil A
Click to expand...


All the advise from old timer/experts to me has been that ground idle is hard on the engine. As soon as it will take throttle without faltering you are read to take-off.

On my IO-360 at ground idle my oil pressure is on the low end of the green. As soon as I am in the air my oil pressure is way up in the green. I would rather get the rpm up to have good oil pressures then let the engine ground idle longer to try and bring up oil temp. Oil pressure is far more important for engine lubrication then oil temp.
 
Don't linger on the ground!

Aircraft engine cooling systems were not designed for "ground cooling". Once the engine has good oil circulation and at least 75 degree temp, you are ready to go.
 
I warm up the engine in cold weather only, otherwise it is runup and takeoff. I usually build up enough OT on the taxi to the active. The other morning at about 55 F I rotated and got "CHECK OIL PRESSURE" in my headsets from the engine monitor. At about 3' AGL I started an abort, but glanced at my OP gauge. It was in the high red! On thinking about it, the engine had cold soaked overnight and I really didn't realize how cold the engine oil was. Gotta start watching the OT again, now that fall is here.

Bob Kelly
 
Mel said:
Aircraft engine cooling systems were not designed for "ground cooling". Once the engine has good oil circulation and at least 75 degree temp, you are ready to go.
Click to expand...

75 degrees has always been my "magic number". I keep the engine heated in the winter and it is 75 when I get in. Prefight checklist, panel check, fuel selector check, mag check, pilot check (this is most critical), ready for take off.

One of the things I do on the first take off of the day is take it easy on the throttle. I usually don't use full throttle on the first take off, 1/2 to 3/4 is all I use depending on loads. I let the speed build up and ease her off the ground at a shallow climb, giving the engine time to warm up at a "lower" (lower than full throttle) power setting. This might not be in the "book", but it makes sense to me. Keep an eye and airspeed obviously.
 
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So, what you guys are saying is when there is somebody at the warm up area for 15 to 20 minutes they are doing their hail mary's?
 
1, I've been taught that you should only take off full throtle since it opens the carb/injection up for additional cooling?? Partial throttle may make the engine run hotter, not cooler.

2, engines idleing on the ground are fine in the low green for oil PRESSURE. If the engine isn't loaded/under power, low green is more than enough. Taking off before the oil temp is 75 or better is dangerous as flow may be limited by oil that's too thick.

3, I like to see the oil gauge come off the peg (ought to be 75 or better F), but I also like the CHT over 275. I like to see this so that I know the different metals in the engine have warmed and therefore expanded to normal operating size. This only takes 5 minutes and I rarely have to wait afer taxi out.
 
Full power....

grantcarruthers said:
1, I've been taught that you should only take off full throtle since it opens the carb/injection up for additional cooling?? Partial throttle may make the engine run hotter, not cooler.

......
Click to expand...

I was taught that too...
...and that would appear to be the case for our engines...

From The Precision Airmotive "handbook" on their web site....

d. POWER ENRICHMENT, (ECONOMIZER), SYSTEM, (Ref. appropriate figure for a particular model).-Aircraft engines are designed to produce a maximum amount of power consistent with their weight. But since they are not designed to dissipate all of the heat the fuel is capable of releasing, provisions must be made to remove some of this heat. This is done by enriching the fuel - air mixture at full throttle. The additional fuel absorbs this heat as it changes into a vapor. Power enrichment systems are often called economizer systems because they allow the engine to operate with a relatively lean and economical mixture for all conditions other than full power.

http://www.precisionairmotive.com/msa_handbook.htm

gil A
 
az_gila said:
To prevent overheating, it is recommended that the following
precautions be observed.
a. Fixed Wing.
(1) Head the aircraft into the wind.
(2) Leave mixture in "Full Rich".
gil A
Click to expand...

Other views:
I recall Walter Atkinson reporting he had actual data indicating that his engine stayed cooler with the aircraft parked heading DOWNWIND.

John Deakin preaches in his "Pelicans Perch" columuns on Avweb to lean agressively while on the ground to prevent plug fouling. Full rich is much too rich at idle. If leaned agressively, you wont make the mistake of attempting takeoff while leaned, because the engine will not respond to full throttle.

E.
 
Im more interested in CHT

Out of habit I look for a CHT of 300F before take ofnd that useually means an oil temp of 100F.

I doubt the oil temp makes much difference but the rapid heating of parts in the cylinders means differential expansion and the closer you are to operating temp before TO then presumably the less differential expansion there is.

Is the optimum 250F or 300F...who knows?

Certainly 300F and 100F oil temp is a happy point for the motor.

As to ground running, remember at idle the thing is making so little power anway it certainly is not cooking anything....Assuming the motor is broken in of course.

Frank
 
They may not be cooking their engine, but they are burning fuel. And these people are usually the ones that complain the most about the fuel cost.
 
For the RV-12 / LSA crowd:

The Rotax 912 has a takeoff minimum for oil temp of 122F. It doesn't have one for CHT.

Some folks who fly the Rotax find it useful to either install a thermostat / varitherm in the oil and/or coolant lines to speed warmup under cold temps. Another (much cheaper) way to help with low ambient temps is a 1" or 2" strip of metal foil HVAC tape across the radiator and oil cooler. This helps to raise oil temp and CHT and can be left in place up to about 60F ambient. Oil temps will stay in the 200 to 210F range if you get the tape on right and will hot 220 or so on climb out. CHT depends a lot on the amount of cooling that is delivered to the cylinder bores via ram cooling air as well as the radiator, but without the tape, the CHT tends to never get into the green when it's below 50F or so.

However, if you forget to remove the tape and it warms up, you're going to be scratching your head, looking at the OT push 230F and starting to get worried until you remember the tape....

TODR
 
Thank you all for the sound advice.

I have noticed many aircraft sitting on the ground for 10 minutes before taxiing and have felt a bit guilty that I wasn't.

Recently I was criticised for starting the motor and taxiing to the holding point but my contention was that "Rough Red" was warming up during taxi and that the run up was safe as the gauge was in the yellow. That is why I started to follow the lubrication debate.

I will take notice of the magic 75 deg F figure. ......and feel guilty no more!

Ted
 
I have read all the stuff about "Full throttle only" T/O.

I have a hard time believing 20"MP 2500 RPM 250 CHTs and 1250 EGTs is cooking the engine. The engine does not know when the wheels are touching the ground.

I think it should be "If you are using 75% or more power on T/O, use full throttle to get the enrichment" Most of the "Full throttle only" T/O lore must have been written on the assumption of pathetic production acft performance capabilities that will not get airborne with less than 75% power thus trying to T/O with 90% or something, hot day, bad cooling design, slow climb, etc, etc, the enrichment is needed. Whoever wrote that doesn't understand "Total Performance". They live in a world of "Limited Performance" Sad to be them.


That being said, I do recognize the safety of altitude=options.
 
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I have an oil thermostate for the Rotax(kitfox), which will be used on my RV, this is a way cool item, allows me to get that oil temp up to 120f fast. I also use a radiator heater for the winter time. This consist of a funnel (for filling oil with) on the back side of the radiator and a hose from that to the inside of the airplane. I put tape on the front of the radiator to keep things hot on the water side, works really well and cheap heat, no weight and no electric draw. I do have a carbon detector inside for those who think this is a bad idea.

Don't feel bad about taking off when others are sitting doing nothing at the beginning of the runway. I trully feel that they are scared or something, they do it here also. I remember when I was doing my training, I would fire up the electronics and get all the information (class c airspace) with taxi approval before I started. Then I would run it right to the runway and take off. Cheaper that way you know. hobbs time.

I see the flight school for moody aviation doing this, I feel they are the big culprits of end of the runway runs. Sure I suppose the instructor has a bunch to go over with the students, but I think they are wasting a lot of gas and wear and tear.

Now for the everyday flier, hum, I think most of the people guilty of doing this are the ones that fly once a month. At least the ones I see only go up once a month. Myself, I fly every day, I get my behind to the runway and in the air, after all, that is where the fun is.
 
I was taught in 172's and the rule was 100F for oil temp before takeoff. That jives well with the others above who indicated 75F+. Most of my friends use the 100F threshold also. It has to be darned cold outside for the oil not to be close to 100F by the time you get taxi clearance, roll to the hold line, and do run-up.
 
Some flight schools teach the "in the green" rule partially because they are charging you for "hobbs" time. You're paying for the warm-up time.
 
Rupester said:
I was taught in 172's and the rule was 100F for oil temp before takeoff.
Click to expand...
That may be a good idea, but the oil temp gauge in that 172 is no where near accurate or precise enough to measure 100deg. With a modern engine monitor that is a different story.

I see you live in cold country. You will die of old age waiting for the oil to get to 100 deg in the winter. 75 is a more realistic number.
 
1.8 Gallons per hour?

allbee said:
They may not be cooking their engine, but they are burning fuel. And these people are usually the ones that complain the most about the fuel cost.
Click to expand...

Well thats what I get taxiing anyway so 10 minutes of warm up is miniscule...Guess it would add up over a lifetime though.

Frank
 
asav8tor said:
I have read all the stuff about "Full throttle only" T/O.

I have a hard time believing 20"MP 2500 RPM 250 CHTs and 1250 EGTs is cooking the engine. The engine does not know when the wheels are touching the ground.

I think it should be "If you are using 75% or more power on T/O, use full throttle to get the enrichment" Most of the "Full throttle only" T/O lore must have been written on the assumption of pathetic production acft performance capabilities that will not get airborne with less than 75% power thus trying to T/O with 90% or something, hot day, bad cooling design, slow climb, etc, etc, the enrichment is needed. Whoever wrote that doesn't understand "Total Performance". They live in a world of "Limited Performance" Sad to be them.


That being said, I do recognize the safety of altitude=options.
Click to expand...

I can buy that and would change the statement for RV's to no extended climb at less than full power unless full engine instrumentation says it's doing fine at your preferred stettings.:D
 
but that refers to MIXTURE, no?

Gil,
Thx for the carb link; but are they not refering to mixture-RICH for takeoff (to aide in cooling) as opposed to THROTTLE position?
 
Some....

bucaronco said:
Gil,
Thx for the carb link; but are they not refering to mixture-RICH for takeoff (to aide in cooling) as opposed to THROTTLE position?
Click to expand...

Ron... thanks for the clarification.... I re-read the Handbook...:eek:

It apparently depends on the model of carb. - I was extrapolating from the horizontal HA-6 on my Tiger...

It depends on the particular MA-4 model according to the handbook...

It is true for "Large MA-4-5, HA-6 Carburetors"

For these, the enrichment circuit only works at full throttle....
I'm not sure whether our typical O-360 carbs. fall into the "large" description for MA-4s...:confused:

gil A
 
Oil temps affect oil pressure

The TCDS for a given engine lists max oil pressure for warm up and normal ops, the former being higher of course.

Most certified aircraft, piston or turbine, that I've flown, do not allow takeoff power with oil temp in "yellow", due thicker oil at colder temps, etc.. I would be concerned with oil flow in smaller passages at lower temps. It also matters where the sensor is located and whether it's accurate of course. Ditto for whether using multi-viscosity or single.

Perhaps some A&P's with lots of engine teardown experience can chime in here.

In South FL, even in the summer, looking at 6-8 minutes to get over 100F, longer in the winter, in RV-6/O-360/CS Prop with a VERY efficient oil cooler.
 
Oil Temp vs Oil type

Like most it seems, I like to see 100 F oil temp, and 300 F CHT before taking off using full throttle, but fed in gradually on the TO roll.

One thing that hasn't been mentioned as yet, is what grade oil you are using.
As I use Aeroshell 15W-50 I believe that I can afford to take advantage of its multi-viscosity by not having to worry so much about the oil being too cold and thick and not moving through small orifices

Martin in Oz
 
Excellent thread - warmup & high EGT on cold days

This thread answered multiple questions and corrected misstatements provided by my flight instructor. The EGT issue at low altitude fields on cold days went away. My Marvel Schebler equipped 9A climbed at 1250 fpm and remained < 1400 EGT. Warm up time was cut in half and the multi viscosity comment underscored another reason for using that oil.

That's a lot to get from one thread. My thanks to all, especially my neighbor Gil.

2021 dues to be mailed on Friday.
 
Ted Radclyffe said:
I have to say that the oil supplier commented that there was justification for the two scenarios but would not venture an opinion either way.
Click to expand...
And...that pretty much sums up the oil debate. No data. There are a lot of anecdotes....and they usually start with “My pappy once told me....”
 
MacCool said:
And...that pretty much sums up the oil debate. No data. There are a lot of anecdotes....and they usually start with “My pappy once told me....”
Click to expand...

. . . . .and they are usually by people who have no financial risk by relaying their opinion.
 
Mattituck told me min 110 degrees oil, 220 degrees CHT for the runup. That's the only temp limitations I have.
 
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