Excessive ground running of engines, can it be harmful?

[Guest colt_pa22]

How long should light aircraft engines, in my case the 0-235 be warmed up pre takeoff? I was taught that we could takeoff as soon as the oil temp reaches the green arc, which on cold days, could be quite some time.

 

The PA-38 flight manual states:? Warm up the engine at 800 to 1200 RPM for not more than two minutes in warm weather and four minutes in cold.

 

Takeoff can be made as soon as the ground check is completed and the engine is warm?

 

I?m assuming that the engine is warm when the oil temp is over 75 F (in the green arc)? Is this the correct interpretation? 2-4 minutes seems a very short time to allow the engine to warm up. The Lycoming operator?s manual does not give approximate times for warm up.

 

Any thoughts?

 

colt

 

 

[Guest Iain]

Warming up

 

It was pretty cold at Camden on Saturday (3 degrees at 7am) and my instructor said that it was normal for the temperature not to reach the green arc till the end of the first circuit.

 

The engine is a Lycoming O-320-B2B.

 

I'd be interested in others' opinions too.

 

 

[Guest colt_pa22]

Iain,

 

That does seem odd, but not un heard off. I know that the Piper Cherokee does run cool in cold weather due to the standard oil cooler and usually needs winterisation plates fitted in operations under 40F.

 

Piper learned their lesson and did not fit oil coolers to the Tomahawk but as an extra for warmer climates.

 

Response from another source:

 

Most engine manufacturers say "...As long as the oil pressure and the fuel pressure is in the green, engine temps (oil temps, in our case)do NOT have to read anything, as long as smooth throttle movements show no hesitation or problems." Like it was stated, extended engine running on the ground is the WORST possible place to run an engine, and should be kept to a minimum anyway! That's when we have the worst airflow over the engine to cool it, while doing run ups and such at the HIGHEST power settings.

colt

 

 

[Guest colt_pa22]

From Lycoming:

 

To prevent possible power loss, a proper warm-up should be conducted. The engine is usually warm enough for pre-flight ground check in above freezing temperatures after 2 to 3 minutes running at 1000 to 1200 RPM. Below freezing temperatures, the warm-up period should be longer.

Looks like I've been taught an incorrect procedure and am damaging our engine.

 

colt

 

 

[TAA Student Pilot]

I don't think youv'e been damaging too much. I just use temps in the bottom of the green, do the runup's and blast off. On a frosty morning it does take a little while, warm day it's nearly taxi out doing moving runups and take off. I usually have the oil above 40C and the CHT above 125C. Saw an old video (I think a Continental one) lately about engine handling, brilliant tape made in about 1958, there was stuff I've never seen before.

 

When all else fails go on the manufacturers recomendations.

 

 

[sixtiesrelic]

warm ups

 

The engine manual can't take the compactness of the cowling around it into consideration.

 

Go with the aircraft manual's time.

 

For example the Tripacer/Colt is fairly tightly cowled so the Cylinder Head Temp can be much hotter than the oil and you have uneven heat in the engine.

 

 

[TAA Student Pilot]

Done a few hours in our ole rocket (a PA22-20), seems OK. From -6's to 37+ seems to keep warm/cool at the right time. Did have some trouble with the front steel oil cooler, put an aluminium one on and no problems.

 

 

[sixtiesrelic]

Yes! I owned a PA 22-160 ... DEB and the oil temp was always OAT plus some figure I forget now, when cruising. Great aeroplane.

 

The manual gave around two minutes ground running time while parked.

 

 

[Guest colt_pa22]

The engine manual can't take the compactness of the cowling around it into consideration. Go with the aircraft manual's time.

Good point sixtiesrelic. I go by the flight manual.

 

I must have hurt a few 0-200 engines in my day. I was always taught to wait till the oil temp was in the green before running up, this could be 10 minutes or more on winter mornings at 1000 rpm, a lot longer than what the manual states but the school insisted on this practice (TVSA / BMSA Vic). Other flying schools also operate like this. Of course, the cylinder head temp will most likely be higher than the oil temp and the engine will be quite hot despite the oil temp reading.

 

Today, as long as I have oil pressure and with smooth movements of the throttle I'm right to go after 2-4 minutes as per the flight manual.

 

This ground running wives tale is not best practice, flying schools especially should take note.

 

colt