Old dog trying to learn new tricks - enroute climbs

[Bennett]

Really enjoy all the academic discussions of VZ, vs VY, LOP vs ROP climbs, Carson speeds, and CAFE efficiency, but I guess I'm just not that kind of pilot who needs, or wants to fool with absolute maximum efficiency, and lowest rate of fuel burn. I like Mooneys, primarily for their relative speed, and for their perceived general

efficiency. For more than 30 years, no matter what aircraft, I have cruise climbed to cruise altitude at about 1.25 times Vy (about 115 KIAS in my J) full rich, full prop

forward, cowl flaps open, under 200 degrees oil temperature, and CHTs all under 380 degrees. When CHT or oil temperature increases beyond these values I lower the

nose of the aircraft, increase my indicated airspeed by reducing my rate of climb. This has always worked out well for me, and I have run engines to TBO (including my

turbo engines). Within the last year or so, thanks to various members of this forum, and from reading the discussions, I have now started to cruise LOP, usually in the

6000' - 9000' altitude range, and I have to say I am quite impressed with the low fuel burns (9-10 GPH) with the prop at 2550 RPM, full throttle, Ram Air open (LoPresti cowl), cowl flaps closed, Oil temp under 190 degrees, and CHTs around 350 degrees or lower. At this set of parameters my TAS is about 160 Knots, about 2 to 3 knots

less than well ROP. I have all the usual speed mods, a PowerFlow exhaust system, and a two bladed "Top Prop". I'm happy with this.

I am wondering how to best do interim climbs. For example I was out a few days ago testing some avionics that were updated, and I was cruising at 5,500' LOP at about 10 GPH,

and I wanted to climb to 8,500' for a course reversal, and to clear terrain. In prior years I would have opened the cowl flaps (unless it was very cold outside), increased the RPMs to 2700, and pushed in the mixture to full, climb at about 120-125 KIAS, and once level, closed the cowl flaps, reduced RPMs, and leaned the mixture to keep CHTs

under 380 degrees. I am curious if the test gurus remain LOP during interim climbs of this magnitude. I certainly don't mind the fiddling of engine and prop controls, as my main concern is not taxing the engine unreasonably. I can't imagine that there would be much of a difference in actual fuel burned for such a short duration, although the increasein rate(GPH) is quite noticeable between LOP and ROP. Maybe it doesn't matter much in the real world, but I would like to hear some opinions about these interim climbs.

[larryb]

Or the other scenario, I often want to climb to 11,500, but ATC holds me at 4,000 and 9,000 for several minutes each due to descending airliner traffic above me. Usually I throttle back a bit and close the cowl flaps at these steps. I use the target EGT method for my climbs. How do other people manage their engine/power at these altitude steps?

 

Larry

[KSMooniac]

I use the Target EGT method for leaning in the climb vs. full rich, and it is more efficient AND more powerful b/c full rich above ~5000' in warm air is actually *less power* than at the Target EGT.  

 

Climbs from cruise speed and configuration of less than 2000'... I just leave my power setting alone and pitch up, then re-lean at the new altitude.  More than that, I'll enrichen back to Target EGT.

 

If I'm held low on departure (in busy areas like the DFW region) I'll level out and keep WOT, Target EGT, and cowl flaps closed so long as CHTs are good. Usually that isn't for very long... and then just pitch up to continue the climb and adjust cowl flaps as required.  I never ever throttle back from WOT until I'm slowing down for pattern entry or instrument approach.

[Bennett]

Thanks Scott. I agree with you completely about a "zoom up" for a 2000' change, although I sometimes will open the cowl flaps partially on warm days. My example was a 3,000'foot change, and I ended up increasing fuel flow with the mixture something well below full rich, leveled off, and then as you say, readjusted the mixture to LOP operations, and a fuel flow that I am

comfortable with from prior experience of going LOP at some particular altitude (and Kentucky windage for temperature). I want all cylinders to be LOP, but I don't go as far LOP as some

contributors to the forum relate that they do. Maybe because I am still getting experience with LOP, and partially because I don't want to give up very much airspeed. I have a JPI 830 that I

really like for engine tuning, but I still am tip toeing into the LOP world. For years, the Mantra was "fuel is cheap compared to the cost of an engine rebuild", and I still hear this from

old time mechanics and pilots of my age. On the other hand, the "red box" is a bit scary.

[carusoam]

Along with Scott from KS,

My '94 O1 recommends climbing using target EGT, indicated by a blue box on the EGT gauge. Climbing at high power over a short time is done comfortably this way. The blue box is a range of about 100-200 deg ROP...

Followed by LOP afterwards...

Best regards,

-a-

[carusoam]

Bennett,

You can abide by the red box theory....

It pretty much ends at 8,000'. (from memory?)

So at 11 - 12,000' it is challenging to go 100F LOP even with a well balanced IO550.

With the JPI indicating that all cylinders are properly LOP, it should be comfortable.

My guess is that when the mechanics went to school, their instrumentation wasn't nearly as good as yours!

One day we will all have ICP and piston temp probes... Running turbo engines LOP during climb... ( just a prediction....)

Best regards,

-a-

[testwest]

Great discussions. I never come off WOT until pattern entry or approach, either. For intermediate level offs I just let it accelerate. Typically the controller is trying to increase lateral spacing from some other traffic conflict to let you climb.. so the faster you go while leveled off, the quicker the conflict resolves and they then issue a higher altitude.

[jetdriven]

I use the Target EGT method for leaning in the climb vs. full rich, and it is more efficient AND more powerful b/c full rich above ~5000' in warm air is actually *less power* than at the Target EGT.  

 

Climbs from cruise speed and configuration of less than 2000'... I just leave my power setting alone and pitch up, then re-lean at the new altitude.  More than that, I'll enrichen back to Target EGT.

 

If I'm held low on departure (in busy areas like the DFW region) I'll level out and keep WOT, Target EGT, and cowl flaps closed so long as CHTs are good. Usually that isn't for very long... and then just pitch up to continue the climb and adjust cowl flaps as required.  I never ever throttle back from WOT until I'm slowing down for pattern entry or instrument approach.

 

At sea level, 100 lean of target EGT is more horsepower than target, but I'll let you guys fight that one out. 

 

Scott, I do similar as you. If being "held down" such as departure in a busy terminal IFR enviroment, I just keep it full throttle, 2700 RPM, and target EGT, and let it wind up to the maximum IAS, which is about 165-170 KIAS. When cleared higher, go like the proverbial "bat out of hell at 10 degrees pitch until reaching 115 KIAS, then resume normal V_z climb. If expecting to be held down below 5K for more than 2-3 minutes, I will pull the mixture back to 10 GPH, because although 170 knots and 16 GPH is cool, its wasteful.

 

Enroute, if the flight level change is 1000' or less, I keep cruise power, trim up for 300-500 FPM and drag it up. If the change is more than 1000' altitude, back to 2700 RPM, target EGT (target -100 above 5,000'), cowl flaps in trail, and let the trimmed IAS plus the additional horsepower bring it up.  Throttle is always full. In fact, we owned the plane two years before I had ever moved the throttle off the firewall. I wasnt sure what to do. Seriously. Whats it going to do?

 

But the fuel GPH was too high to complete the 820 NM trip, and further LOP and lower RPM wouldnt do the job.  pulling ti back to 24", and running 15-25 LOP (7.2 GPH) allowed the magic 20 NMPG in order to make destination.  Jim R watched all this on Flightaware and laughed. We still had enough fuel to fly another 100 NM, which theoretically is a 920 NM range in a 54 gallon bladder equipped M20J, plus IFR reserves.

[Bennett]

Thanks for all the comments. Thanks to running LOP in cruise, I now fly San Carlos to/from Scottsdale without a fuel stop (as I was doing when I first bought the M20 J). In fact, I landed with more than 25 gallons remaining (out of 64) coming and going on my last trip - averaged 9.4 GPH in the 8-9,000' area, and sometimes down to the 8.6 GPH area at mildly higher altitudes. This aircraft is proving to be a good traveling machine. I do note that the fuel flow is much higher when I climb out, and hence my questions about interim climbs. Even VFR involves step climbs because of the upside down wedding cake (highly modified by the Bay Area terrain) class B airspace, and IFR sometimes is even worse to the point that departing VFR, and picking up the clearance further down the route allows for higher altitudes sooner.

[201er]

Is there any good reason to stick to a constant target EGT once above 5000ft (or power is below 85%)? Is there anything wrong with being 100ROP in a climb once power is below 75% (as long as CHTs are ok)?

 

Under the presumption that detonation threat diminished as you approach 75%, I've been flying target EGT until my EDM830 shows below 85%. Then I slowly allow EGT to increase toward Target+100 until I reach 75%. Might go something like this:

 

SL 100% 1260

2000ft 90% 1260

3000ft 87% 1260

4000ft 85% 1260

5000ft 83% 1290

6000ft 80% 1310

7000ft 77% 1340

8000ft 75% 1360

9000ft 72% 1360

 

My reasoning for doing this is that it saves a little fuel while giving a little more power. By being less over-rich and closer to best power, I'm giving myself a little more power back for climb at higher altitude when the climb/power is already diminishing. Now I want to check with you guys to make sure that the same logic that would apply toward leaning in cross above 75% will apply the same in climb.

[jetdriven]

I like it Mike, and we do that too. Above 5000 I start running target EGT (1285 on #3 for us)  -50 to -100 depending on OAT.  Above 8K or so, 80 ROP. The power difference is noticeable.

Its almost too easy, above 8K, just turn altitude hold off, prop 2700, mixture to 1420 (80 ROP for us, YMMV),  and the extra horsepower makes it climb at the trimmed cruise airspeed.

[testwest]

201er is right, the way he does it might be called "Target EGT - Advanced" since the method is a little more sophisticated. It's what I do as well, above 5000' lean out a little more, just like he posted.

[garytex]

The benefit I see for climbing LOP is controlling CHTs on hot days.  It really works, and still get 500 fpm at 120 mph indicated at light weights.

[aaronk25]

I'm convinced on our io360 engines its impossible to get into detonation no matter where you put the red knob as long as the chts are under 400.

With that its easy to put the red knob in the wrong spot and get to 400 In a hurry, but transient adjustments will not create detonation in my opinion.

Peak egt is 1550 at 1000agl and target egt on take off is 1250. After take off when work load permits I go to 1380 and target it all the way up. If the chts start going north of 380 I will go to full cowl flaps instead of trail and enrichen to 1320 or so. Lower the nose some too. This only works at 120kts indicated.

Ill flow 17.8gph on roll then about 14.5gph after initial lean. I think running target egt in the 1260-1280 range waste some fuel and creates excessive blow by into the oil.

I'm in MN where its cooler may not work in texas heat. I use to climb LOP, until you guys proved me wrong that it wasn't more efficient due to decreased prop efficiency.