Overheating of aircraft in dusty weather 1

[shariff001]

The main problem we face in operating the ABT-18 aircraft is the high Cylinder Head Temperature (CHT) of between 240degC to 300degC against the designed value of 205 to 240degC. The occurrence is predominant in dry dusty African weather and is rarely observed at other times of the year.

The aircraft is powered by a 180hp, 2700rpm lycoming engine fueled with Mogas. Attempt to solve the problem by moving the oil cooler to where there is better airflow and the use of higher octane fuel have not given much result. Can any one please contribute.
shariff

 

[MintJulep]

What are your operating conditions?

What are the wet and dry bulb temperatures at the altitudes you are operating?

What is the density altitude at ground level?

Are the heads fouled with dust?

 

[shariff001]

The overhaeting mostly occur when the airplane is operating at maximum power in a climb even at rich mixture setting. The temperaature range at altitude is between 18 to 25 degC, and the cylinder heads are not fouled. It may be important to state that the air filter on the plane is a cotton-felt K&N filter. For the density altitude, I will cross check that with the meteorology chaps and get back to you. Thanks for the response.

 

[enginebob]

Those are some very high cylinder head temps. I'm suprized you haven't had some major problems from it. You mention dusty, so are you getting alot of accumilation of dirt on cooling fins? Mogas, at least here in the USA has no lead in it. I suggest av gas with lead. Are you real sure of the air/fuel ratios? Do you run an airfilter? Check your magneto timing also.

 

[aviat]

What is an ABT-18?

Lycoming’s website has info on high CHT’s from a maintenance and an operations perspective. As far as which air filters to use, SI 1002 cover that subject. Also under Publications/KeyReports/Maintenance/Air Filter Maintenance there is more info. I would add that the filter and other openings should be covered/plugged when not in operation.

As far as air filter causing high CHT I think it could occur in a couple ways. With a carb’d engine the hot air box could allow heated air into the engine if the filter is not allowing in enough air. At high power setting this would lead to increased temps. Another way could be a differential pressure causing intake pipe leakage, which leads to a lean mixture and high CHT.

http://www.lycoming.textron.com/main.jsp?bodyPage=/support/index.html