For the SR22 owners: When do you execute your first power reduction after takeoff?
I climb full power until levelling off and then lean the engine to LOP. During the climb, I only lean per the max fuel flow chart on the panel. After the first 1,000’ AGL, I typically increase and hold my airspeed between 120 and 140 and climb at about 1,000 fpm (unless my wife is with me and then do about 700 fpm - she feels that higher rates of climb are less comfortable and more dangerous, and it is only by her good graces that I get to fly at all[;)]). If obstacles or other concerns are an issue, I’ll continue a higher performance climb as necessary.
The recent AvWeb article (Great article, BTW) and others have mentioned reducing power anywhere from 1,000’ to 2,000’ AGL and leaning from there. From my perspective, the high power climb seems better. My thoughts are: Pros:
Easiest, least amount of effort.
Never have to worry about accidentally going too lean during climb. Unless, I’ve missed something, you still have to find PEAK EGT in order to settle on 75 - 100+ degrees ROP.
Never worry abut engine temps.
My climbs are rarely longer than 7-10 minutes (6,000 - 9,000’ MSL), and even if I climb to 11,000’ or 12,000’ MSL at my wife’s climb rates (700 - 800 fpm), I am still leveled off at less than 15 minutes from wheels up.
Gets me to cruise, LOP setting quicker.
Avoids the annecdotal, engine failure at first power reduction, or at least gets me a lot of altitude first. Cons:
Engine runs dirtier.
More noise, inside and out.
Less fuel efficient.
I’m still young enough to change, so I’d like to hear from others…
I have been agonizing over this question as well. Most light planes with big Continentals call for a power reduction shortly after sea level takeoff, which makes me wonder if Cirrus and Continental are pushing the envelope a little here (as with no cowl flaps or other means of cooling air control). I’ve experimented with climbing at full throttle and 2500 RPM. It makes less noise, climb performance is ample, temperatures are fine, but the question is: How to set the mixture?
I took a look at the placarded max power fuel flows. Using the cruise performance tables for full throttle MAP (which is ambient pressure minus some flow loss) I calculated the mass air-fuel ratios at each altitude under ISA conditions. Not surprisingly they are very consistent, varying by a total of 2.1%. I then extrapolated the fuel flows for 2500 RPM assuming the same mass air-fuel ratio. Here are the results:
Altitude (ft) Fuel Flow (GPH)
0 25.1
2000 23.4
4000 22.0
6000 20.6
8000 19.4
10000 18.1
12000 17.0
If I ever get my bird out of the avionics shop I’ll do some careful tests to see what these numbers do in terms of EGT (wish I had multi-probe EGT). IF YOU CHOOSE TO LEAN DURING CLIMB AT LESS THAN MAX POWER YOU ARE NOT FOLLOWING THE POH AND YOU ARE DOING SO AT YOUR OWN RISK. There are things to consider, such as less than ideal mixture balance between cylinders at lower power settings or changes in detonation margins at lower RPM. Below 4000 ft there is the possibility of “lugging” the engine at full throttle and 2500 RPM. Perhaps someone with a better knowledge of spark-ignition IC engines could shed some light on this. I am well aware of the pitfalls of trying to re-engineer complex products without the factory’s knowledge and research facilities. I appreciate any comments and will report my results.
I used to pull the throttle back to 2500 RPM after 1000 feet AGL, but during our first CPPP session, my instructor showed me the error of my ways. I think that we really do end up “lugging” the engine a bit, especially at high climb rates…sooooo, I just keep it at full throttle and manage the leaning until I am at cruise (whether 3000 feet or 17,000 feet).
I don’t claim to be a Deakin but my feelings about full power climbs in the Cirrus revolve around the fact that we cannot control rpm and mp separately, and that the last bit of throttle provides a significant increase in fuel flow.
Using that information it seems to me that full power is where the engine is operating under the most stress. The pressure and temperature in each cylinder are at the highest levels and good engine cooling is mandatory to increase the detonation margin.
Therefore, since the last bit of throttle causes an increase in fuel flow I leave the throttle full forward and let the excess fuel cool the engine. In most aircraft you can reduce rpm while leaving the throttle full forward but in the Cirrus when you pull back the throttle the rpm comes right back to 2500, then the mp decreases. I suspect that there is also a fairly rapid decrease in fuel flow with the concomitant decrease in excess fuel for cooling. At least in theory that should decrease the detonation margin and that is NOT a good thing. (I haven’t tried that so I don’t know if that’s really what does happen).
While I don’t think it’s dangerous to reduce power for climbs (I suspect there is still sufficient cooling to keep detonation at bay) it seems to me that leaving full power for the climb provides for 1) better engine cooling through increased fuel flow, 2) either a faster rate of climb or a faster climb airspeed to get higher or farther faster while still providing good cooling, and 3) a higher detonation margin because of the increased cooling.
The idea of rapidly reducing power relates to older engines that had a maximum takeoff power rating that was time limited. Our engines have no such limitation.
As I climb I reduce the mixture according to the placard on the right glareshield. It seems to work well with very reasonable reading on all CHTs and EGTs.
Marty, Mike,
I know you asked for SR22 procedures, but I just thought I would chime in with a note about the SR20 – at least the older ones, like mine. It’s getting to that time of year again when I cannot climb at full power without exceeding comfortable temps on my cylinders.
So I usually climb to roughly 2000 ft AGL (or whenever CHT #1 hits 410 degrees, typically right around that altitude) at full power. Then I reduce power but leave mixture full rich, and can continue climbing at an anemic 500 fpm (if IFR – if VFR I’ll climb even slower) and can usually keep the CHTs at or under 420.
Although I run LOP at cruise, I have never personally tried it during climbout, though I believe it would help. Even in that case, though, you’re not running full power even if the throttle is wide open.
So for most SR20 drivers, I don’t think a full throttle climb is a possibility.
On the same topic – how do the “newer” SR20s work in this regard? Ones delivered after September 2001, for example. Do they run significantly cooler due to the new cowling?
If so, maybe it’s worth trying to put the new cowl on my plane.
“I even go back to full throttle for enroute climbs, e.g., when climbing from 5000 to 7000.”
Me too, at least for climbs over a few hundred feet. I figure the few seconds it takes to lean to the proper max fuel flow settings is better than running too lean and hot.
I understand that Cirrus has contracted with an engineering firm to modify the SR20 to go faster and cool the engine better. These mods will probably involve cowling changes, at least.
I doubt if anyone can predict whether those mods could be fitted to existing SR20s, but it might be worth waiting to see.
On the same topic – how do the “newer” SR20s work in this regard? Ones delivered after September 2001, for example. Do they run significantly cooler due to the new cowling?
Steve,
I got to test this the other day climbing out of Lake Havasu, AZ (KHII) in our SR20 (S/N 1174, delivered Jan. 2002). It was 39 Celsius on the ground (in Fahrenheit, that’s #^$%*! hot). Climbing out at 95-105 KIAS for the first 3000 feet or so, the cylinder head temp and oil temp both stayed comfortably in the green. So perhaps the new cowl has some significant benefits…
I have SR20 #1170 (delivered Jan 02). I can climb out at full throttle in 90 degree F ambient air from a 1180 ft msl airport at climb rates of 700 to 1000 fpm and keep the CHT (based on the “steam gauge” CHT, don’t have engine monitoring yet), between 375 and 400. The highest I’ve hit was ~410(one needle width past 400), when asked by ATC to climb as fast as possible after departure to 6000 ft for traffic. In cruise at 2500 rpm and 25 map, CHT routinely stays right at 300.
I spoke with Ian yesterday. The mods that will be incorporated into the SR20 version 2.x will primarily be, as stated in the customer update, to help the SR20 meet its stated book performance numbers in more real-world scenarios. It does well at 8000’ and standard temperature, but vary the temp or the altitude and performance fails to meet the book values too frequently. The mods are many that individually each add little, but together make a measurable difference. Since there are a number of parts that will be involved, the liklihood of a retrofit being cost-effective is not very high.
I got to test this the other day climbing out of Lake Havasu, AZ (KHII) in our SR20 (S/N 1174, delivered Jan. 2002). It was 39 Celsius on the ground (in Fahrenheit, that’s #^$%*! hot). Climbing out at 95-105 KIAS for the first 3000 feet or so, the cylinder head temp and oil temp both stayed comfortably in the green. So perhaps the new cowl has some significant benefits…
Roger,
Do you have multi-point CHT monitoring? My factory CHT gauge (on cyl #2) stays comfortbly in the green, but CHT #1 (on the Arnav engineview system) is pushing 420-430 on extended climb outs. Just wondering when you say that your CHT and oil temp stay in the green if you’re just talking about the factory guages or all 6 CHTs?
I have SR20 #1170 (delivered Jan 02). I can climb out at full throttle in 90 degree F ambient air from a 1180 ft msl airport at climb rates of 700 to 1000 fpm and keep the CHT (based on the “steam gauge” CHT, don’t have engine monitoring yet), between 375 and 400. The highest I’ve hit was ~410(one needle width past 400), when asked by ATC to climb as fast as possible after departure to 6000 ft for traffic. In cruise at 2500 rpm and 25 map, CHT routinely stays right at 300.
Okay, let me ask a related question now, since both you and Roger have mentioned that you’re able to keep the “steam gauge” CHT within good limits.
Have other people with SR20s noticed that the “steam gauge” CHT is not the hottest temp, when using a multi-point engine monitor (Arnav, JPI, etc.)?
I can also typically keep my #2 CHT (the one connected to the steam gauge) below 400 – say 380-390. But the #1 runs a good 30 degrees hotter than #2. So when #2 is reading, say, 390, #1 is at 420.
In other words, if the “steam gauge” CHT really is the most accurate and/or the hottest cylinder (like I would have imagined, when they chose which cylinder to put the CHT probe on), then, like you guys, I can also climb with no problems.
On the other hand, it appears that CHT #1 in my plane runs hotter. So THIS is the one that I have problems keeping cool, unless I throttle back and climb slowly (slow vertically - fast horizontally).
Steve, I have the older model. Although I may move to the new cowl, I don’t want to do it to offset a problem that is coming from a different source without fixing the source.
I’ve been working with the service center, Cirrus, and now Continental - the Continental rep is coming to look at my plane next week.
When I have a better idea of what’s going on, I’ll be sure and share it on the forum. We seem to be making progress with my heat problem, if nothing other than eliminating possible sources of the problem.