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Flying club aeroplanes "interdit" above 35deg C...

Interesting Email correspondance from my Aeroclub:

Had an initial Email as per title, ie no flying of Aeroclub Robins if the OAT is 35degC or higher. I naturally questioned this thinking it was to do with performance degredation, pointing out I can make performance calculations and understand density altitude…

…But no, its not about that. Paraphrasing the reply to English: “A cracked cylinder was discovered during the 100h and a 2 cm gap in the intake valve – this is a known problem characteristic of Lycoming engine overheating and we, like many aeroclubs are now limiting flying in high temperatures on the advice of our mechanic..”

Ive spent some time googling and I cant find anything about this kind of OAT limit for Lycomings and such a “known problem”…

My own view is that I doubt many pilots in the club ever look at the engine temperature gauge when they are flying and have no idea about treating an engine kindly. Gut feeling is telling me the highly cyclic "High Power to Low Power/Idle then back to High Power and back to Idle nature of circuit bashing, handling & Engine failure training, is possibly more relavent… But could there be something to it?

Thoughts?

Regards, SD..

Last Edited by skydriller at 21 Aug 08:44

How very odd. I can’t quite figure out where they are thinking the cracking occurs. Following startup and before takeoff? Otherwise if you take off and climb you’re into cooler air anyway. Do people spend a long time on the ground running and getting things too hot? Surely it can’t be coming back into land as you’re coming in with low power and lots of airflow.

I must admit I’ve never thought much of starting up when it’s hot out. My concern is much more when it’s really cold, I understand much below freezing there is a concern about the aluminium piston thermally expanding much quicker than the steel cylinder and getting tight.

Wow. Arizona should stop flying forever then.
The question is : how do the CHTs behave on our club airplanes ?
At first I would say very cool because everybody flies full rich all the time.
Personaly, I have trouble keeping the engine cool when I climb high in summer (above 3000ft in aeroclub speak). In a 172, I have the oil temp nearing the red line, in the robin CHT get above 400F.
I usually climb above Vy for this reason but it makes climbs even longer…

In one of my clubs, we have a different more sensible advice in hot weather : don’t use the carb heat ! They crashed a plane this way.

Can you tell me which club it is via PM ?

LFOU, France

skydriller wrote:

…But no, its not about that. Paraphrasing the reply to English: “A cracked cylinder was discovered during the 100h and a 2 cm gap in the intake valve – this is a known problem characteristic of Lycoming engine overheating and we, like many aeroclubs are now limiting flying in high temperatures on the advice of our mechanic..”

35C deg is way bellow CHT max which is 250C/480F deg? I think the mechanic did read the wrong pages of the Lyco engine book or run the wrong C/F

It will be 25C deg at 5000ft agl, I hope they were not expecting people to fly at 0ft agl in the said Aeroclub

Again, the only sensible speed to climb at is Vy-5kts/Vy+10kts anything else will get you killed or burn your engine !

Last Edited by Ibra at 21 Aug 09:07
Paris/Essex, France/UK, United Kingdom

@skydriller doesn’t the high power, low power, idle cyclic happen all the time, not just in high temperatures?
The question is whether or not that causes a problem or whether the higher ground temps make a difference. We operated Robin’s of all sorts over many years for school and didn’t suffer any real problems. Ground temperature of 35 degrees is unusual except for July and August in certain parts of France, although (canicules/heat waves) do seem to be becoming more prevalent each year. Forgive me for stereotyping but isn’t the phrase “mad dogs and Englishmen go out in the midday sun”.
But contrary to what UK pilots seem to think in our PPL training we were always taught about watching temperatures along with many other engine care procedures.

France

Jujupilote wrote:

Wow. Arizona should stop flying forever then.

As of today, they only fly nights and mornings there but has to do with afternoon bumpy sky and daily TS at end of day !

Paris/Essex, France/UK, United Kingdom

gallois wrote:

doesn’t the high power, low power, idle cyclic happen all the time, not just in high temperatures?

Well yes, and this was my thinking. OAT of 20 deg C or 35 deg C would make no difference.

IMO this is highly dependent on how the cooling system of the engine is designed, not so much the engine itself. Letting the engine run on “idle” on the ground over a longer periods of time may work on some aircraft, but not on others.

The pipistrel alphatrainer is notorious. At “idle” (2000 rpm), it will overheat on the ground, but runs cool in the air. The solution is to “idle” at 3000 rpm, and point it into the wind if holding too long. Other Rotax powered aircraft have no problems with this.

The elephant is the circulation
ENVA ENOP ENMO, Norway

Yes, but that is specific to certain engine/airframe combinations, the Lycomings driving the Robins do not have that problem. I am afraid that 35 degree limitation is complete BS imposed by somebody who “needed to do something”.

Also, how warm it is outside makes more difference for water cooled engines than for air-cooled ones. How effective the cooling system is, all other things like airflow being equal, depends on the temperature difference between the air and the thing it cools.

For water cooled engines, the water (and hence radiator) is typically at around 80 degrees, so the difference between 30 and 40 degrees OAT is a change of delta-T from 50 to 40 degrees, a 20% reduction in cooling capacity. For an air cooled engine at 180 degrees (quite hot on the ground – around 350 F) , that delta-T reduces from 150 to 140 degrees, less than 10% reduction. Although running at 350 on the ground would be atrociously high.

Biggin Hill

Without account for taxi hold ups or similar, my only real ground time restriction is getting the oil up to 100f. As long as I can do my checks and any other bits I need to I’m usually ready to go. I cannot see how this ground time or warmer temps can do any particular damage.

This guy pretty clearly appears to be exercising power because he can.

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