Trip report Shoreham EGKA to Granada LEGR, TB20, nonstop ~900nm

[Peter]

www.peter2000.co.uk/aviation/granada

[B!]

Post by Peter
www.peter2000.co.uk/aviation/granada

Excellent reading material. Thank you!

-Rene (PPL/IR)

[Mike]

Post by Peter
www.peter2000.co.uk/aviation/granada

That's a very nice writeup. One thing I was curious about was what kind of
CHTs you were observing at 25 LOP. I've been running a IO-540 25 LOP with
similar fuel flow results, however CHTs occasionally reach 400 on the
hottest cylinder at about a 70% power setting.

[Peter]

Post by Mike

Post by Peter
www.peter2000.co.uk/aviation/granada

That's a very nice writeup. One thing I was curious about was what kind of
CHTs you were observing at 25 LOP. I've been running a IO-540 25 LOP with
similar fuel flow results, however CHTs occasionally reach 400 on the
hottest cylinder at about a 70% power setting.

Normal cruise CHTs at peak EGT or thereabouts (I don't run "deep" LOP;
no point as there is no measurable fuel saving) are about 350-370F.

But I don't fly at 70% of max power. More like 60-65%, and having no
turbo, at FL100 one is only doing around 50% anyway although I have
never exactly looked it up.

400F in cruise would seem too high. Worth checking baffling. Even a
3mm gap between a baffle and the ends of the cylinder fins can stop
enough air going in between those fins to raise the CHT by some 50F.

On the TB20, there is a mysterious higher CHT on the RH cylinders
(1,3,5) and this is still there on the ex-SB569 rebuilt engine. I am
sure this is because the oil cooler is on that side, and a lot of air
escapes through that instead of going down through the cylinder fins.

[Mike]

Post by Peter

Post by Mike

Post by Peter
www.peter2000.co.uk/aviation/granada

That's a very nice writeup. One thing I was curious about was what kind of
CHTs you were observing at 25 LOP. I've been running a IO-540 25 LOP with
similar fuel flow results, however CHTs occasionally reach 400 on the
hottest cylinder at about a 70% power setting.

Normal cruise CHTs at peak EGT or thereabouts (I don't run "deep" LOP;
no point as there is no measurable fuel saving) are about 350-370F.
But I don't fly at 70% of max power. More like 60-65%, and having no
turbo, at FL100 one is only doing around 50% anyway although I have
never exactly looked it up.
400F in cruise would seem too high. Worth checking baffling. Even a
3mm gap between a baffle and the ends of the cylinder fins can stop
enough air going in between those fins to raise the CHT by some 50F.
On the TB20, there is a mysterious higher CHT on the RH cylinders
(1,3,5) and this is still there on the ex-SB569 rebuilt engine. I am
sure this is because the oil cooler is on that side, and a lot of air
escapes through that instead of going down through the cylinder fins.

I don't run at 400 CHT for any length of time. My target is the 360-380
range. High CHTs aren't a problem at lower power settings, so what I wind
up doing is setting a lower power setting so I can stay in the happy,
non-cylinder eating range. 65% or lower generally does the trick.