DA40 CHT - Advice needed

[DCLEMONS]

I'm a student pilot and want to say how valuable this forum is. What I read is amazing and Im very thankful for responses. My CFI and I were departing Nampa ( KMAN) - thats close to Boise Idaho. At 1000 AGL, I - started my check list - Pump / Flap / Left Cross Wind call. The baffles have been removed.

I started to lean the Mixture slightly - and noticed within less than one minute the CHT was approaching 450, we both missed the temp reading. The Garmin panel was front and center, we just were not watching it due to inbound traffic, I adjusted the Mix to full and immediately leveled, but was surprised that the CHT temp was not falling back to normal rate .

I realize my mistake of adjusting/ leaning the mix on climb, it was a bad idea. Will never do that again - unless the climb in high elevation requires it.

My question for you is this:
What are the steps for cooling CHT correctly? Is it more than setting the mixture to full and to level?
What is the procedure that you have found that works and how long does it take to get the CHT to respond to cooler readings ?

Since the CHT readings were not coming down - I immediately turned back to the airport and continued manuevering at 4000+ ft AGL, the temp came down and the engine seemed to be OK.

I definitely hit the CHT ceiling and never want to see that again - I will be watching that CHT temp reading going forward.

Appreciate your advice in advance. David

[Rich]

Was it one cylinder, more, all? What were the EGTs and fuel flow?

One thing I'd do is pop the cowling off and make sure there are no nests (bird, rat, hornet, etc.) lurking in the engine compartment to impede cooling airflow to the engine.

[Rick]

David, it sounds like you did all the right things - add fuel, level off or reduce climb to reduce engine load and increase air flow over the engine. And staying over the field was a smart call, just in case things don't start to improve. I, too, would be interested in the answers to Rich's questions.

It is normal for the CHTs to change slowly - remember they are measuring the temerpature of a large mass of metal that takes some time to change temperature - unlike the EGT, which is measuring the temperature of the exhaust gas and changes almost instantly. I would expect it to take many minutes for the CHTs to fall back into the normal range after you take corrective measures. The important thing with CHTs is to see that the trend is in the desired direction.

[DCLEMONS]

Rich - Hello again !
Thanks .
I hanger my plane and just change the OIL with my mechanic - no nest !
All 4 looked to be hitting the same temp within a few points. Really glad I had removed the Baffles the week earlier - Boise was all over the map in TEMPS. But its time for warmer temperatures now and the heat is going to be an issue.

I should have snapped an image -

I would say they temps starting falling within 5- 10 NM down around 300 degrees , by that time I was over the airport.

[DCLEMONS]

Thx Rick , Appreciate the advice.

Its amazing with all of the Avionics I have in the Da40 ( 09) I would be able to catch this. It happened fast - in realtime CHT increase.

I didn't look at the EGT, thx for asking. ( Rich's question...)

Do you think I could have damaged my DA40 by running the temp up to 450? Is there some test I should have my mechanic look at ? This is quite an investment so I want to make sure it is still in good shape. Btw - any idea how long CHT could sustain a high temperature without doing Valve and or Head damage ?

Has anyone experienced damage?

David

[Gasser]

I doubt very much that you damaged your 40 by having your CHTs high for just a couple minutes.
That said, aluminum gets soft at those temps and the cylinder can get out of round causing problems thus it can cause ring issues if left for too long. If your really worried, do a leak down and compression test. I wouldn't worry if all is running well. During your run up, make sure all your spark plugs are working. While your at 2000 RPMs, lean until you can see all your EGT bars. Switch to mag 1 then to mag 2. Watch bars for a steady rise on 1 and return to baseline on both. If you see an EGT fall out completely then hat plug is dead. If one rises way more than others you could have a partially fouled plug or if EGT is way higher than peek maybe a stuck exhaust valve. You can get a lot of info from your run up.

My normal climb out procedure as a diamond driver with "some"experience:

Climb full power, full rich (1000' msl). I make a mental note of my EGTs and CHTs. As I climb out and gain some alt. I will very slowly pull out some fuel every thousand or two feet to keep my EGTs at my original take off value. In other words, as you climb you will get richer and richer because of less air. If your too agressive in the lean you will get the EGT close to peek and thus peek cylinder pressures which in turn will make your CHTs climb out of controll. I also will try to keep CHT at 380 or below.

There are a couple of ways to reduce the CHTs and both involve reducing cylinder pressures.

Add fuel. This reduces pressures and thus heat
Increase airspeed, this increases cooling flow over the cylinders
Reduce manifold pressure, this reduces cylinder pressures as above.

As a student, for now while your mind is VERY busy learning and is preoccupied it might be a good idea to leave it full rich during your climb out for safety since your more likely to be in attentive to your engine monitor. Your also unlikely to fly up very high during training to do all your ppl maneuvers.

Another way you can cool your cylinders is to lean even further past peek EGT to a lean of peek setting.

This reduces cylinder pressures even further than any ROP setting, makes manifold pressure less criticle. But is more work than you need to be worrying about as a student trying to focus on a lesson.

Once you finish your PPL, I highly recomend you take an engine management course. It will be an awesome investment in your money and time.

Jeff

[Rich]

Flying out of the Boise area, full rich mixture is generally called for on takeoff and local flying. But I flew 1,000+ hours out of Idaho Falls. That field (and most of the others in SE Idaho) are high enough to warrant leaning for takeoff in anything but dead of a cold, cold winter day. This is also true for all of Wyoming, and most of Montana and Utah. In fact almost everything South or East of you for 500 miles or more. Many of these require leaning in winter, even.

It sounds like excessive leaning was the culprit here. My practice is to delay leaning until the EGT's start dropping below 1300 deg F in the climb.

When I first got my plane (a 2002) it had cooling problems on #1 cylinder, even in cruise. Then Diamond came out with what they called the "Arizona" baffle, which is now the stock system. Basically this provides a larger inlet on the right side of cowl. Not only did it eliminate the #1 cylinder cooling problem, it brought all cylinders down AND brought all CHT'S tighter together.

[Gasser]

Once you learn your plane, the cool thing about different altitudes is that you lean for the same target EGTs during a climb. For my plane locally, 1000' MSL full rich EGTs tend to be 1250. If I climb out at Denver I lean for best power then take off. I make adjustments once in a steady climb for my same 1250 or so all the while keeping an eye on my CHTs keeping them in check.

GAMI has a nice graph showing this climb and leaning principal. Works perfect for me.

[Rick]

Hey David, I just had another thought. If you had an SD card in the upper slot of your MFD during this flight, you can go through the numbers and see what actually happened, or even upload the flight data to the DAN for all to see (look at the REPORTS section). That is also a good way to look back and see what the potential might be for any possible damage, although I doubt you did any in such a short time.

[Charles]

I've had to enrich to full rich and level off after leaning too aggressively in climb and found that the CHTs dropped faster with the throttle wide open as opposed to pulled back. I believe the greater airflow and fuel flow explain the higher cooling rate.

But this is anecdotal at best.