Forgot to enrich mixture for take off
 

Hallo

I got a question for all the engine experts out there:

Prior to take off I forgot to enrich the mixture on a Cessna 172 (Lycoming IO-360) by missing out the step in the before take off checklist.
I leaned to prevent plug fouling.
I thought I leaned enough, so the engine would stall when I increase power.
Obviously not:
The engine ran fine for about 5 Seconds, acceleration was o.k., then after 10-15 seconds the aircraft acceleration became less, engine running rough.
At that point I noticed my mistake, pushed the mixture all the way forward and continued.
Airfield elevation is 560' and temp was around 55°F.

Now my question:
I was angry at myself because of this error, otherwise didn't think much of it. Reading some other threads, I came to think:
Can this 10-15 seconds period of running leaned at take off power already damage an engine?


Right now I'm trying to develope a habbit pattern to check the important items prior take off additionally to using the Checklist.

Thanks!

Very unlikely to have damaged the engine in 10-15 seconds. It is good that you leaned enough so you would notice it on take-off. It is a good habit to lead with the mixture and prop (if equipped) before opening the throttle on take-off or go-around.

Try and stick with the factory checklist, sometimes when you add your own items it dilutes the value of the original list as you tend to skip things or create redundant items that are out of sequence from the POH

You should not IMO be reading checklists while on the runway. I teach a memory flow that always occurs as you cross the hold line in order to take position.

It is:

Mixture ......Rich
Carb Heat....Cold
Strobes ........On
Transponder..Alt

The idea is to develop the muscle memory so that the check becomes automatic.

Note: The landing light goes on when cleared for takeoff (controlled airport) or starting yoru takeoff roll (uncontrolled airport)

That's a good practice Big Pistons; use the check-list but also have a memory scan for the critical items. Just like GUMP before landing!

In UK I was taught "reds, blues and greens" before landing ie Mixtures, RPMs and Wheels. "Reds, Blues and carb heat" would work prior to take off and might seem more natural to a UK trained pilot.

The detail is unimportant but the principle is excellent and potentially lifesaving.

Happy landings

3 Point

I like to think that if I experienced a lack of acceleration and rough running on the takeoff roll (particularly in a SEP) I would reject the takeoff rather than trying to troubleshoot the problem on the roll and continue into the air. It's a lot less stressful sorting out a problem on the ground than it is in flight. I know, I know, benefit of hindsight etc etc, but it's a valid point and possibly a lesson to take away from the experience.

have you ever noticed that if everything is FORWARD during TAKEOFF, things are right.

prop fwd (if constant speed) mixture, throttle, carb heat

you screwed up...learn from it and I ask you, did you lean for the runup?

why didn't you do your engine run up with mixture rich?

did you not do a run up/magneto check?

was there a delay between the runup and takeoff?

Has happened to me many times - just last week, actually. No big deal on the ground, but can become a big deal after takeoff. Try to find a system that works for you so you don't forget.

I'm no expert, but I would think it very unlikely that you could do any damage. Because you had leaned aggressively, the engine would not have been developing much power (as a percentage of max power) so I would think that you are fine in that regard.

If you lean for taxi lean so aggressively you need to enrich for any power above idle, don't lean after power checks which should be done full rich

...and then sit in the conga line prior to takeoff with the mixture full rich and the plugs fouling?

I just had a breakfast flight to an airport with a field elevation in excess of 6,000' this morning. If my factory checklist said mixture rich, should I comply or violate another old wive's tale or a lawyer driven POH recommendation?

For the OP, probably not.

Good points! as the OP didn't have a location I assumed he was in the centre of the universe aka the United Kingdom;)

To answer your questions:

you screwed up...That's for sure, everybody does form time to time, I guess...learn from it and I ask you, did you lean for the runup? No, I did the runup with mixture rich

why didn't you do your engine run up with mixture rich?

did you not do a run up/magneto check? Yes, I do it prior every departure

was there a delay between the runup and takeoff? Yes, due to heavy traffic. I leaned after the run up and then forgot. Not good!

PapaAlpha
 

Since I fly anywhere from sea level airports to those with elevations in excess of 6,000', I have developed the habit of setting the mixture for the appropriate density altitude as the final step before adding power for the takeoff.

This final step becomes very easy if flying the same airplane every time, and I confirm the mixture setting by referencing the EGT's shortly after takeoff. I also lean during the climb to maintain the same EGT I would have had if I had taken off at sea level with the mixture full rich.

FWIW, I have been an advocate of WOTLOPSOP for the past 1,000 hrs on my IO-520D with great results as advertised by the GAMI folks. :ok:

Forgot to enrich mixture for take off
 

How much plug fouling would be incurred during that wait for take off?

The reason i say is there are many "club aircraft" that stick to the mixture rich part of poh and those planes buzz around all day weather permitting.

Please dont attack me my baby has kept me up all night :(

I also have a set of "Pre Takeoff Vital Actions" that I perform, although normally just before crossing the stop bars, as after that point I want to have my eyes outside the cockpit as much as possible!

We lean for for taxi and lean for cruise but don't touch the red knob between "Power checks" / run up and takeoff.
Would you not set the mixture to the correct level during the runup then not touch it?
It would have to be a very long weight for plug fouling to occur I'd have thought?!

I have a lining up check that I do every time I cross the threshold.

Everything forward. Take off Flaps set. Fuel on. Correct runway. Engine ok.

I think of the Madrid accident with no take off flap every time I line up. It's a config check but in mind I always think it's my staying alive check.

Lights, Camera, Action (Landing lights on, Transponder on, Mixture/Prop/Throttle full forward).

If you've done all the runup checks and then sat waiting a long while due to heavy traffic, it wouldn't hurt to do a mini-runup again when you enter the runway. Just a quick engine check at 1700-2000 RPM for magnetos and carb heat before pushing in full power. This adds less than 10 seconds to your take-off, but may well catch a fouled plug or carb ice at a very critical moment.

The other thing is to keep a count. If I need to wait for a long time after the runup checks have passed, I might lean the mixture and I might also open the canopy for ventilation (Robin DR400 or R2160 with no other means of ventilation while on the ground). I mentally keep a count of things I need to undo before take-off. So when I finally line up, I know I'm two items short of being ready for departure.

With regard to mixture rich for runup, then leaving it there and then wondering how long it would take to foul the plugs...it depends on how rich/lean the system is calibrated at idle and the density altitude of the airport. Certainly, if nothing were noticeable, the effect of fouling the plugs would be cumulative. I flew a Super Cub on floats that would lead the plugs fairly quickly. One had to lean dramatically to keep the plugs clean. Idling along to the takeoff point didn't help, either.

I lean my IO-520 powered 185 after start and leave it there (even during the runup) until ready for takeoff, then set it for the density altitude (I primarily fly in the mountains), not necessarily full rich.

With regard to everything forward, and leaving it there after the runup, has anyone ever experienced carb ice waiting for takeoff? When flying a carb equipped airplane, especially this time of year in the northern hemisphere when the temp/dew point gets more cozy, I alway begin the takeoff roll with full carb heat. Normal RPM is confirmed and then the carb heat is reset to full cold with a corresponding increase in RPM noted (if flying a fixed-pitch prop).

Blasphemy or practical application and understanding of an internal combustion engine? I would like to think the latter, and the years and hours have confirmed it. My IO-520, with over 1200 hours on a Continental factory reman (with original cylinders...no top overhaul), with good compressions and oil analysis also confirms that I might be doing something right.

I am from the internet, though, so investigate and think for yourself on this stuff. :cool:

I also now do that in some conditions - after having the engine lose power as the throttle was opened for TO. (O200 using mogas.)
PS Could Konsin treated surfaces allow carb ice formation at temperatures lower than would be expected from the usual carbice diagram?