Dear All
Just purchase a SR 22 GTS 2006
I have been discussing with some pilot friends which would be better altitude for the aspirated engine. Some pilots are saying that the best performance is achieved on 7000 feet, and, for my only 47 hours of cirrus, I still think a 9000 feet would be better if you want to operate in 75% b. performance mode on a 200 mile trip.
Is there any material regarding this information.
Best
AFAP
I’m not sure which performance parameter you’re interested in but if it’s speed at 75% power then the highest altitude at which the engine can produce the 75% power you want is the one that will give you the highest true airspeed. That altitude will vary depending on temperature. You can find these speeds in Section 5 of the POH.
Of course depending on winds you might be better off at some other altitude because what determines how fast you get where you’re going is ground speed and that depends on airspeed and winds aloft.
Finally, the altitude you chose may depend on other factors like cloud bases or tops, or turbulence or terrain.
So there is no simple answer to your question.
To elaborate further on what Jerry said, if you want raw speed with calm winds I find it is somewhere around 8,000’ but other factors generally override that as the decision maker. For fuel efficiency it is as high as you can go. The speed makes so little difference in time that many other factors (weather, terrain, airspace, winds, fuel burn) come into play. AT 180 kts I’ll burn about 18 GPH running rich of peak. Up high I might only do 164 lean of peak but my fuel burn will be about 11 GPH.
Paul
Thank you Jerry and Paul. Totally agree regarding the other aspects that are really important on flight. During long international flights from Ft. Faudardale to São Paulo, we use to travel around 12.000, and had 11.5 GPH. The engine rpm started to vary after 13.500 without the fuel pump on, which I think it is normal.
So basically if you want to “rent” the airplane to friends in 200 mile trip, the best thing to do is to use the airplane around 10.000, to get the best fuel efficiency.
Best,
Andre
The NA SR22 is happy all the way up to 17,500. I fly with the mixture LOP, and do about 170 knots independent of altitude. On long trips, I go high for fuel efficiency. On short trips I fly 9K or below (I get headaches at 10K without O2).
I wouldn’t say it’s happy at 175… 200 fpm from 140 on up… constanly leaning? Takes quite a long time wallowing at 102 KIAS.
Marc,
Do you use 75% LOP or your limit for LOP is 65 % ?
I really don’t have a % power limit in mind that I use, but it turns out I don’t think I ever cruise over 70% power (14.5GPH). I generally do a “Big Mixture Pull” to get lean of peak and just leave it there or adjust the mixture based upon EGT and CHT. At low altitudes, I’m not flying long enough to worry about gaining a few extra knots. At higher altitudes, I’m generally at 50-60% power.
Luiz,
One of the most difficult concepts for many new to LOP to grasp is the concept of percent power. When you are running lean of peak percent power is directly related to fuel flow. So regardless of what percent power it says on the Avidyne (or ARNAV) your power LOP is dependent only on Fuel Flow.
Once you reach cruise most of us do what Marc does - The “big pull” - and that puts us in the LOP range. We then can enrich, find peak from the lean side and back off OR we can simply set the fuel flow we want. As long as all EGTs are rising while we enrich from the result of the big pull we are still in LOP territory.
The formula for knowing your percent power in the SR 22 is ( (Fuel Flow * 14.9)/310) * 100. For example, 13.5 gallons/hr gives about 65% power.
There’s lots of good info about this on the Members Side. Look especially for Gordon Feingold’s posts on “The Red Fin”
Hi, I also bought a SR22 GTS last July; so far, i achieved three weeks ago a KIAS of 179 knots at 73 % power (full throttle) at 8,500 feet over the Adirondacks mountains with an OAT of 56 degrees and an atmospheric pressure of 32.14.
I think that any altitude between 7 and 9 thousand are efficient for the SR22.
Regards
I fly our 2007 SR22 GTS on 500nm+ trips on a regular basis. Over this length segment, the airplane is very happy at 10-12,000ft where at 65% indicated power and LoP/Best Economy I constantly see 13.1gph (or less) and 168-172ktas. Over the same altitudes at Best Power mixture and max power (roughly 75%) TAS inches up to 178-182kt with fuel flows in the 17-18.5gph range.
If wind makes it worthwhile to climb into the 13-16,000ft altitudes, LoP fuel flows are in the 10.5-11.5gph range with TAS around 165-170kt.
Over a 200nm segment, I’d use between 8,000-10,000ft.