I have been a member here for almost the past year and have learned TONS from reading the post. I had been away from flying for 25 years, bought a used SR20 in January… got current and got my IFR ticket, picked up my new G3 SR22 in July. When everyone asked me how I like my Cirrus… I have to add a disclaimer before I answer the questions, “I drink the coolaide!”
In my 20, I was taught to always run RoP. I did this and always was disappointed with the fuel econ. Started reading the forum more and learned about the benefits of LoP. My general rule now is that if the trip is less than 30 minutes, I go 75% RoP. More, I go 65% LoP. The question that I have is about descents. I got the 1336C Engine Op Procedures today and the reccomendation is “Brutally lean.” What I have been doing is going back to absolute on the Emax, then keeping the CHT’s and EGT’s in a good range for the descent. I have learned that this takes a very delicate touch. It seems that you can spike to peak very quickly if you are not super careful.
Is there any magic in the working with the mixture during the decent?
Any help would be most appreciated!
Thanks!
Doug Kessler
07 SR22 G3
N571SR (soon to be N572GT)
I have been a member here for almost the past year and have learned TONS from reading the post. I had been away from flying for 25 years, bought a used SR20 in January… got current and got my IFR ticket, picked up my new G3 SR22 in July. When everyone asked me how I like my Cirrus… I have to add a disclaimer before I answer the questions, “I drink the coolaide!”
In my 20, I was taught to always run RoP. I did this and always was disappointed with the fuel econ. Started reading the forum more and learned about the benefits of LoP. My general rule now is that if the trip is less than 30 minutes, I go 75% RoP. More, I go 65% LoP. The question that I have is about descents. I got the 1336C Engine Op Procedures today and the reccomendation is “Brutally lean.” What I have been doing is going back to absolute on the Emax, then keeping the CHT’s and EGT’s in a good range for the descent. I have learned that this takes a very delicate touch. It seems that you can spike to peak very quickly if you are not super careful.
Is there any magic in the working with the mixture during the decent?
Any help would be most appreciated!
Thanks!
Doug Kessler
07 SR22 G3
N571SR (soon to be N572GT)
Why go ROP on short trips? The difference between ROP and LOP on a 30 min. trip is about 15 seconds. Why burn the extra 5 or 10 bucks worth of gas?
If I’m going less than 30 minutes (not very high) I go about 80-85% power LOP.
Really learn LOP and you won’t be stuck at 65% power and you will virtually never go ROP.
For descents LOP, I just nudge the mixture forward a little every now and then. Since I am pulling the power back to maintain a reasonable airspeed the mixture doesn’t matter all that much.
Mike,
You shouldn’t have to move the mixture much at all during decent. EGT and CHT will stay very cool as you decend and ultimately reduce power. If you get a little roughness, give it a little mixture, but this will probably only happen in final at MP <13" (this depends a lit bit on what altitude you are decending from). You don’t have to worry, you are so far from Peak EGT at this point, there won’t be a spike, nor will you be in the Red Fin.
If you haven’t already read the LOP operations in Copapedia, I suggest you give that a look. I keep a print out in my plane just as a reference.
I was taught to always run RoP. I did this and always was disappointed with the fuel econ.
Why would anyone who was at all frugal, concerned with efficiency/range, or has any care for the environment want to pour unburned fuel out the exhaust pipe (e.g. run ROP)?
Taxi, idle, cruise, descend LOP.
I cruise-climb LOP asap after takeoff.
I go 65% LoP. The question that I have is about descents.
Doug,
On your SR20 you should not need to touch the mixture knob at all during descent. Your altitude compensating fuel pump will keep the mixture the same, so your EGT’s should change very little. This is different than with the SR22 which lacks the altitude compensation feature.
You will want to go full rich/fuel pump on before landing; I do so when cleared to land at a controlled field, or when entering the pattern at an uncontrolled airport.