Rotax radiator

[skippydiesel]

Sorry Skippy, if a preflight doesn't include inspection at the cap, you need to 'change your installation'. If not, one day you WILL be looking for somewhere to land with a cooked goose! Experience talkin'.

I have not disagreed with the principal of your argument just its practicality in real life operations where cowling considerations preclude easy access.

 

I would also make the point that a correctly fitted safe cap stays that way until someone does not complete the locking turn or forgets to lock it down altogether. Cooling system problems are better diagnosed by observing leaking coolant, empty or contaminated overflow reservoir than repeatedly opening & closing the cap which lets air into what is supposed to be an air bubble free system.

 

In the scheme of priorities you might do better to checking that the radiator fins are free of chaff/insects etc that may cause your cooling system to overheat.

 

As I said my installation is not ideal from a cooling system cap inspection point of view but after 700+ hrs of trouble free operation and many more hours of trouble free operation of similar systems in land based vehicles, I feel confident that my maintenance regime, preflight checks and instrument scan give me almost all the information I can hope for.

 

Do you inspect the radiator cap on your land based vehicle before each journey? No! nor do I. I do glance at the translucent overflow tank about once per week - coolant level normal, system good to go.

 

Cooling system rarely give problems, if correctly maintained. Usually give plenty of notice of things like seal or cap leakage. Using proper/appropriate cooling system hoses/pipes, coolant mix and observing the Rotax service interval/time limits on hose and coolant life, is far more important than obsessively checking an already correctly installed cap.

 

Any change in cooling system "normal" performance should be responded to as you would an imminent engine failure - if in the air LAND - if on the ground do NOT TAKE OFF.

 

My aircraft along, with all its Rotax 912 powered siblings, has an exemplary safety record.To my knowledge, in about 20 years of operation across hundreds of aircraft, there has yet to be a catastrophic cooling system malfunction reported.

 

There are no grantees an apparently normal engine may fail on take off or in cruise. Usually there are warning signs that were ignored or just not observed/understood.

 

 

[pluessy]

I agree with skippydiesel, there is no need to open the cooling system cap (pressure cap) at every pre-flight. What you need to do is get familiar with your overflow bottle level:

 

- what is the level stone-cold (winter) and cold engine on a hot day? depending on your bottle diameter, there can be quite some different levels.

 

- what is the level when the engine is hot?

 

- keep an eye out for any stains around the overflow bottle, this indicates a leaking radiator cap or overheating cooling system

 

- don't forget to include the radiator cap in the 5-yearly rubber hose replacement program (gasket is rubber and the most likely part to deteriorate and cause loss of cooling system pressure -> loss of coolant)

 

Radiator cap is BMW P/N 17112345074 at about 1/2 of the Rotax price (fitted to BMW motorcycle F650 with Rotax engine).

 

I had one event of total loss of coolant due to a (LAME-fitted) hose coming off on climb-out. caught it in time from increasing CHT (older style heads), reduce power, returned and landed normally. With about 4,000rpm, the CHT went back to normal thanks to the air-cooled cylinders. No damage to the engine, have done about 200h since.

 

At the last annual, I removed the cap to inspect the condition and it was leaking slightly afterwards, noticed the stains on the overflow bottle after the test flight. The less you touch it, the fewer problems you are likely to have.

 

Thomas

 

 

[skippydiesel]

Well said - Thank you Thomas