Need advice for fuel control in climbing to higher altitudes

[Jer]

Folks:

I have been flying more frequently back and forth between the west coast and Albuquerque.  I am getting interested in seeing how thrifty I can get with the fuel.  I generally fly no higher than 12,000, and as I always use oxygen above 8 or 9 thousand, I started thinking of flying higher, even up to the service cieling.  I am pretty comfortable with leaning at cruise, but I was wondering what folks think about leaning during a cruise climb at these higher altitudes.  I think climbing to 18K will take quite a while, as I imagine the climb rate will be very low, and so I don't really want to throw 15 or 16 gph at it the whole climb.  I just find it hard to accept running at full rich near the flight levels, even while climbing.  Any thoughts on this?

 

Jer

[LANCECASPER]

28 minutes ago, Jer said:

Folks:

I have been flying more frequently back and forth between the west coast and Albuquerque.  I am getting interested in seeing how thrifty I can get with the fuel.  I generally fly no higher than 12,000, and as I always use oxygen above 8 or 9 thousand, I started thinking of flying higher, even up to the service cieling.  I am pretty comfortable with leaning at cruise, but I was wondering what folks think about leaning during a cruise climb at these higher altitudes.  I think climbing to 18K will take quite a while, as I imagine the climb rate will be very low, and so I don't really want to throw 15 or 16 gph at it the whole climb.  I just find it hard to accept running at full rich near the flight levels, even while climbing.  Any thoughts on this?

 

Jer

So let's say you shaved 3 gallons her hour off of your fuel flow and let's say that you were only climbing at a meager 200 feet per minute. To get from 12000 to FL180 would take you 30 minutes or 1.5 gallons extra. At $6 per gallon, congratulations you saved $9. Don't spend it all in one place. Even if you saved twice that much I don't think it will change your standard of living.

I would suggest that you get up to your eastbound tailwind altitude by using max fuel flow so you can enjoy the benefit of the tailwind that much sooner - it will most likely save you much more that leaning in climb.

[Jer]

Thanks for that input.  The goal really was not a financial one, as you correctly surmised.  I just wanted to practice this and see how I did on the trip to ABQ, where I stop for fuel on my way to the Texas panhandle.  I've been toying with the idea of trying to make it all the way without the fuel stop on a day with a big tailwind.

[Slick Nick]

Are you suggesting that you normally climb with a full rich mixture? 

Don’t.

You should be leaning as you climb for best power plus a bit if you need the additional cooling. The J doesn’t. 

If you left it full rich, your engine would quit long before it got to 18,000’. I would know. I’ve been to 180 in my J and it required some extremely aggressive leaning just to make it there. It wont do it with full tanks either. Half tanks and no more than one person is what it takes on an ISA minus day. 

There is no published service ceiling on the J. 

[EricJ]

Lean as you climb, some think just keeping the EGTs about the same as takeoff is good practice.   Just watch CHT and oil temp as well.    You won't be burning anywhere near 15-16 gph as you go up whether you lean or not.    You'll only use that at lower altitude where the air is denser.

If you're careful with the wind over the ridges you can often use that to assist climb.

 

[Ragsf15e]

20 minutes ago, Jer said:

Thanks for that input.  The goal really was not a financial one, as you correctly surmised.  I just wanted to practice this and see how I did on the trip to ABQ, where I stop for fuel on my way to the Texas panhandle.  I've been toying with the idea of trying to make it all the way without the fuel stop on a day with a big tailwind.

While I agree with Lance that it’s probably not a financial winner, it’s also a reasonable thing to use at times.  Especially in the southwest, you can get above most of the thermal turbulence in the summer (well, not all though).  I flew my F at 15,500’ a few times, it’s not terrible, but you’re running like 50% (or less) all in and closing in on best glide as your indicated airspeed, so a little downdraft and you’re probably not holding altitude.  
It will only get up that high (easily) when it’s light, like several hundred pounds below mgw.  I always used target egt method to set mixture in the climb and that was fine.  Thats the method of leaning to hold takeoff egt.

You’ll be at such a low mp anyway, you just use ROP or peak in cruise if you want to try it for a power setting, but you’ll likely want all the power you can squeeze out ROP and still be around 7gph.  If you can catch a tailwind or smooth air, it’s probably worth it, but without the tailwind, you’ll be around the same speed (but on less gas).

[Jer]

More good takes on the issue.  No, I usually do not go full rich in climbing after about 8000.  I do monitor the cht as well as the egt and make sure the cht never surpasses 400 on any cylinder.  I have had no trouble with this.  But I have never flown over 15,500 and the extended time for climbing concerned me.  The KSNA to KABQ would be a trial run to assess whether or not I would try the 845 nm trip KSNA to KPPA.  I would be doing this solo, with full tanks and minimal cargo

[Ragsf15e]

5 minutes ago, Jer said:

More good takes on the issue.  No, I usually do not go full rich in climbing after about 8000.  I do monitor the cht as well as the egt and make sure the cht never surpasses 400 on any cylinder.  I have had no trouble with this.  But I have never flown over 15,500 and the extended time for climbing concerned me.  The KSNA to KABQ would be a trial run to assess whether or not I would try the 845 nm trip KSNA to KPPA.  I would be doing this solo, with full tanks and minimal cargo

Id definitely do it vfr first because she becomes a little mushy up that high because your ias is lower and it can be hard to control altitude if you hit a downdraft.  Otherwise, go for it!  Let us know how it works out!

[Jer]

Good point!

[McMooney]

after about 4k i lean just enough to see the needle twich, try to keep it at that point as i climb.  

oxygen above 8 or 9k, just feel better when i fly at altitude for long bits.

generally fly peak or  slightly rich of peak at altitude

 

 

Edited January 4 by McMooney

[201Mooniac]

14 hours ago, Slick Nick said:

There is no published service ceiling on the J. 

Must depend on the year, my M20J POH shows service ceiling for both 2740lbs and 2300lbs in the climb performance data.

[Jer]

17 hours ago, McMooney said:

after about 4k i lean just enough to see the needle twich, try to keep it at that point as i climb.  

oxygen above 8 or 9k, just feel better when i fly at altitude for long bits.

geenerally fly peak or  slightly rich of peak at altitude

 

 

Mr. McMooney.  What needle is that?  Are you referring to egt, fuel flow or other?

Jer

[McMooney]

24 minutes ago, Jer said:

Mr. McMooney.  What needle is that?  Are you referring to egt, fuel flow or other?

Jer

sorry EGT, i try to lean so it just twitches off the low stop

[Bartman]

I flew solo to 15K once to avoid weather. I started level at 11k and was running about at peak EGT. I asked for 13K, and didn’t change anything except increase from 2,500 to 2,700 for the climb. Running at peak EGT at 13K I asked for 15K and again the only thing I did was increase to 2,700. Once I was at 15K even in VMC it felt very mushy and I left it at 2,700 in cruise, and I would not want to be in the clouds at 15K.  
 

At 15K and above in a normally aspirated M20J you would not have enough power to out climb even a mild downdraft, and I would not want to experience that in IMC. 

[redbaron1982]

23 hours ago, Slick Nick said:

Are you suggesting that you normally climb with a full rich mixture? 

Don’t.

You should be leaning as you climb for best power plus a bit if you need the additional cooling. The J doesn’t. 

If you left it full rich, your engine would quit long before it got to 18,000’. I would know. I’ve been to 180 in my J and it required some extremely aggressive leaning just to make it there. It wont do it with full tanks either. Half tanks and no more than one person is what it takes on an ISA minus day. 

There is no published service ceiling on the J. 

When I try to lean to takeoff EGT while climbing on my J the CHT go above 400F, with cowl flaps trailing (halfway close). 

Do you keep you cowl flaps full open? 

Today at cruise (8500ft) and 22x2500, I was running at 380F with closed cowl flaps and 15F LOP. OAT was 15C. 

I'm still not sure if I have a cooling issue or not. 

Edited January 5 by redbaron1982

[TangoTango]

We cruised from Phoenix to Dallas in our J at 15,500' earlier this past summer. With two aboard, full tanks, and bags, we were probably a little north of 2700# and it did fine. Climb rate was getting below 300 fpm toward the top, but we were isa plus a lot. I even pulled it back to 2500rpm, leaned to peak, and got low 140ktas. I wouldn't call it "mushy", it just felt like it normally does at lower indicated airspeeds. I did note that while it was cool and smooth, we still got about +/-10 knots of mountain wave while maintaining that altitude over NM. Still had plenty of margin over vy. 

For what it's worth, I routinely lean to takeoff EGT all the way up (17.5gph at sea level) and have no cooling issues with cowl flaps full open unless I sustain a vy climb for a long time in hot conditions. This time of year I could do it indefinitely. 

[Ragsf15e]

16 minutes ago, redbaron1982 said:

When I try to lean to takeoff EGT while climbing on my J the CHT go above 400F, with cowl flaps trailing (halfway close). 

Do you keep you cowl flaps full open? 

Today at cruise (8500ft) and 22x2500, I was running at 380F with closed cowl flaps and 15F LOP. OAT was 15C. 

I'm still not sure if I have a cooling issue or not. 

In climb, your cowl flaps should be full open. Especially if your engine is getting warm.  That’s what they’re for.

[Slick Nick]

17 minutes ago, redbaron1982 said:

When I try to lean to takeoff EGT while climbing on my J the CHT go above 400F, with cowl flaps trailing (halfway close). 

Do you keep you cowl flaps full open? 

Today at cruise (8500ft) and 22x2500, I was running at 380F with closed cowl flaps and 15F LOP. OAT was 15C. 

I'm still not sure if I have a cooling issue or not. 

You must have an issue. I keep my cowl flaps completely closed most of the time unless it’s quite warm outside. There’s no hard and fast rule on them, just use as required to keep the temps in check. That said, I can’t seem to get my CHTs anywhere near 400 I think the highest I’ve ever seen on a hot day in Arizona was 375. Have you got the new style cowl flaps or the original J ones? You’re sure they’re rigged properly?

I suspect you may have an issue with your baffles. It doesn’t take much of a leak to cause a rather large decrease in cooling. 

[Ragsf15e]

1 minute ago, Slick Nick said:

You must have an issue. I keep my cowl flaps completely closed unless it’s quite warm outside. I can’t seem to get my CHTs anywhere near 400 I think the highest I’ve ever seen on a hot day in Arizona was 375. Have you got the new style cowl flaps or the original J ones? You’re sure they’re rigged properly?

I suspect you may have an issue with your baffles. It doesn’t take much of a leak to cause a rather large decrease in cooling. 

Weren’t you just talking about flying at -30c though?  That makes a big difference.  Generally these things need cowl flaps open in climb.

[Slick Nick]

4 minutes ago, Ragsf15e said:

Weren’t you just talking about flying at -30c though?  That makes a big difference.  Generally these things need cowl flaps open in climb.

Yes, but I still fly in the summer. 

I usually keep them closed on the ground to help the engine reach operating temp sooner if it’s FFOD, then only open them as required. Once I’m above about 100-120 knots, even on a warmer day, I can still easily keep temps under control with them closed or half open, depending on OAT. The 252 and the J are two very different animals when it comes to cooling requirements. 

My plane has manual flaps, so they’re infinitely adjustable, but you can still feel a “hump” roughly in the middle where the mechanism cams over to hold them in place. 

[Ragsf15e]

15 minutes ago, Slick Nick said:

Yes, but I still fly in the summer. 

I usually keep them closed on the ground to help the engine reach operating temp sooner if it’s FFOD, then only open them as required. Once I’m above about 100-120 knots, even on a warmer day, I can still easily keep temps under control with them closed or half open, depending on OAT. The 252 and the J are two very different animals when it comes to cooling requirements. 

My plane has manual flaps, so they’re infinitely adjustable, but you can still feel a “hump” roughly in the middle where the mechanism cams over to hold them in place. 

I had an F until recently, maybe the cooling is a lot better on the J, but my F needed the cowl flaps open during climb.  Once in cruise closed was good.  Leaning to SL target egt should be fine in climb, and Id say if it’s hot and the cowl flaps aren’t all the way open, then open them, that’s what they’re for?

[Slick Nick]

6 minutes ago, Ragsf15e said:

I had an F until recently, maybe the cooling is a lot better on the J, but my F needed the cowl flaps open during climb.  Once in cruise closed was good.  Leaning to SL target egt should be fine in climb, and Id say if it’s hot and the cowl flaps aren’t all the way open, then open them, that’s what they’re for?

Yep exactly. Did the F still have the “dog house” under the cowl? Also having well sealed baffles makes a huge difference as I mentioned above. 

[Ragsf15e]

2 minutes ago, Slick Nick said:

Yep exactly. Did the F still have the “dog house” under the cowl? Also having well sealed baffles makes a huge difference as I mentioned above. 

Nope, it had flexible baffles, the cowl design isn’t quite as good as the J though, so I believe you when you say you can keep them half open, but if your engine is warm in the climb and they’re half open, id definitely open more.  Obviously airspeed, oat and mixture will play a part too. (And baffle quality).

[redbaron1982]

48 minutes ago, Slick Nick said:

Have you got the new style cowl flaps or the original J ones?

My J is a 1986 model, not sure when the new style cowls flaps become standard. 

My baffle seals, AFAIK, are in good shape. I have considered using Gee Bees seals.

[Jer]

1 hour ago, TangoTango said:

We cruised from Phoenix to Dallas in our J at 15,500' earlier this past summer. With two aboard, full tanks, and bags, we were probably a little north of 2700# and it did fine. Climb rate was getting below 300 fpm toward the top, but we were isa plus a lot. I even pulled it back to 2500rpm, leaned to peak, and got low 140ktas. I wouldn't call it "mushy", it just felt like it normally does at lower indicated airspeeds. I did note that while it was cool and smooth, we still got about +/-10 knots of mountain wave while maintaining that altitude over NM. Still had plenty of margin over vy. 

For what it's worth, I routinely lean to takeoff EGT all the way up (17.5gph at sea level) and have no cooling issues with cowl flaps full open unless I sustain a vy climb for a long time in hot conditions. This time of year I could do it indefinitely. 

Just to help me understand, when you said you were at "low 140ktas", you were still in the climb?  If you were in level cruise, maybe you meant KIAS?  I generally get 157 KTAS in a cruise between 8000 and 12000, full throttle, leaned rich of peak but I do richen it up to keep CHT below 400.  I don't know why they call it a 201, which is 175 KIAS.  I had hopes of achieving this at higher altitudes, but the comments here seem to indicate that is not going to happen.