My home airport is 5650 MSL. When things heat up, the DA can be over 8500 on take off. I know Continental recommends full rich on takeoff. At this elevation the engine is not producing full power, should I lean it a bit for takeoff? It sure idles better with a few turns to the lean side. Also does anyone have a link to the IO-550f operators manual? Thanks for the help. The plane is my first 185 and my first io-550.

Folks I know have always leaned for max smooth power around 2100-2200.
for carb. engines as full power will kick in with the fuel enrichment for WOT.
And then leave at WOT during initial climb. SOME POHs may have a limit on WOT time in use as I recall with the first Turbo 206 I flew. It was the only plane I ever had to hold the brakes to ensure to not exceed 35" MP, the first time or two. soon learned how to open the throttle to the "correct" Index finger "pinch" guage without over-boost.

Forgot if Injected engines have the feature but would surely lean for "close" to highest smooth operation on run-up. Maybe a quarter to one half turn rich to avoid detonation if you are not sure. It will inherently get richer as you climb.
That is why you keep leaning as you climb to keep same EGTs and CHT.

Best I can remember
Your POH - AFM - STC supplemental Docs. etc. may vary, with liability limiting instructions or restictions.

Chris C

The best technique for leaning an engine for takeoff at high density altitudes is to run up at the end of the runway, lean quickly... by pulling the mixture back until you see 1300-ish degrees on the EGT and then go.

That being said the IO-550 has an altitude compensating gizmo that figures that out for you so you don't have to lean it yourself. One thing about the 550 (and to a lessor degree the 520) is that you should have adequate fuel flow for COOLING. The 550 should be north of 32 gpm for takeoff.

Of course you didn't hear that from me;

gunny

You need to figure out if you have an altitude compensating fuel pump or not? If you don't know, you can find a copy of TCM SID 97-3G which gives you data for proper fuel injection setup as well as diagrams to help you identify which pump you have. As previously commented, increased fuel flow at take off power is your friend. You can always lean if you're too rich, but if you don't have enough and the cylinders are cooking, you're screwed. The factory max setting is NOT enough. You are looking for around 30 Gal hr and 1250-1300 egt as a general target for sea level wot. (30" map X 2700rpm) For a max effort T/O, lean to get close to 1300 egt. You may find some resistance from some A and P 's that are resistant to higher than book fuel flows because they don't understand the engine. Find one that will set it up correctly. Otherwise you will be buying cylinders.

https://www.twincessna.org/pdf/SID97-3G.pdf

My IO-550 F likes between 24.5 gph-28 gph on takeoff . There is no altitude compensation thing on there . My home airport is at 5900 ft and routinely I operate around 85+ degrees air temp in the summer . .....I have digital fuel flow and I believe it to be very accurate . 550 is great because it seems like after takeoff those scary high fuel flows can be brought way down into happy camper numbers real quick .

low rider wrote:My IO-550 F likes between 24.5 gph-28 gph on takeoff . There is no altitude compensation thing on there . My home airport is at 5900 ft and routinely I operate around 85+ degrees air temp in the summer . .....I have digital fuel flow and I believe it to be very accurate . 550 is great because it seems like after takeoff those scary high fuel flows can be brought way down into happy camper numbers real quick .

28 gph isn't scary high for a 550. As others have noted, at sea level, I want to see over 30 gph, preferably 32 gph at takeoff.

Absolutely find out if you have an altitude compensating pump. And if you do, have it removed and replaced with a standard pump.. Those altitude compensating pumps have done a lot of damage to these engines.

Call Continental and order a manual for that engine. The information in the 185 POH is no longer valid for engine parameters.....you need a 550 manual, and you SHOULD have a POH Supplement for the engine....if not, order that as well.

MTV

Ok - The best advice I ever got on the 520/550 conti's is lean it to 1325-1350 degrees on the EGT's while on your takeoff roll. That will keep it healthy and your CHT's will be 320.

Jim

low rider wrote:My IO-550 F likes between 24.5 gph-28 gph on takeoff . There is no altitude compensation thing on there . My home airport is at 5900 ft and routinely I operate around 85+ degrees air temp in the summer . .....I have digital fuel flow and I believe it to be very accurate . 550 is great because it seems like after takeoff those scary high fuel flows can be brought way down into happy camper numbers real quick .

I must admit I'm a flatland guy... so I did mean 32 gpm for takeoff at or near seal level;) I should have been more specific.

A few things: I agree with the comments about removing the altitude compensating system on the IO-550, it is not smart enough to actually take care of the engine. 28 gpm is definitely NOT enough fuel flow and it isn't scary at all.... that big check to replace the cylinders is what scares me (besides really big is a R-1340 running through 52+ gpm on takeoff and 32 in cruise or an R2600 burning 150 gpm on takeoff and 75 in cruise);)

as always YMMV,
gunny

To be clear , 28 gph does not scare me. It just makes my wallet vibrate in my pocket on take off.Also, I am almost never flying at sea level.? My CHT's and EGT's seem to be real happy with those numbers at the altitude the op was talking about . At sea level I do not lean. Yea and the big radials I am familiar with do show some impressive gph numbers in cruise and on takeoff, those don't scare me either because the radials I have flown behind have been work airplanes and i am not the one buying the fuel,.

I would shoot for 30 gph on takeoff and 1350 on the EGT's in the climb out. ABS magazine had an article on this a while back. There was a picture of the fuel flow/MP gage and the hands were about the 8:30 and 4 o'clock positions if I remember right.

Here is the FF Placard for the Bonaire/Davis IO-550D STC in the 185. This should be in your AFM Supplement as well as a posted placard.
The EGTs are a relative number varying with the position of the probe, which is not a specified distance from the cylinder - at least on the JPI installation.

Thanks for the replies

Since I've flown out of high elevation airports with quite high DAs most of my flying life, I will relate what I was taught to do back in 1973, which seems to be good for any normally aspirated airplane, whether carb'd or fuel injected. When I was instructing, that's what I taught, and that's what I do now. Other than my primary training at sea level in the Anchorage area, the first 23 years I flew was throughout Wyoming and northern Colorado (other than a few cross countries to lower elevations), based at Laramie, elev. 7277'. DAs there in the summer are often in the 10,000' range. Right now, at 10 p.m., the DA there is over 8800', and the temp is only 60F. Now I fly out of Fort Collins and Greeley, DAs right now 7400' and 7150' respectively.

Do it at run-up rpm--higher power settings aren't necessary and are more likely to pick up FOD with the prop. Slowly run the mixture control leaner until the rpm just barely starts to drop--not even a needle's width. Then enrichen the mixture about half an inch with the mixture control--seems crude, but it works with every engine I've flown, from O-200s up through IO-520s. I haven't flown an IO-550, but if it doesn't have an altitude compensating pump "gizmo", I can't think of a good reason why it would be any different.

Turbo'd engines are different, and ordinarily they'll be flown at full rich, even at high DAs. But full rich on a normally aspirated engine is way too rich at high DAs, and really inhibits power. What you're really wanting is best power for take off, but a tad richer for cooling--and that won't compromise best power enough to notice. The method I described above does that.

Cary