I just got my private pilots license this year and have a total of about 250 hours. I purchased a 2001 SR20 and have put on a little over 100 hours on this plane. The plane only has 400 hour TT. I love the plane, but it seems to not perform (as far as airspeed) close to what the specs say it should. Usually during level cruise, I will be flying 110 IAS. Altitude variations from 3000 ft MSL to 12000 ft MSL doesn’t seem to make any difference. Throttle during cruise is usually set at 2500 RPM. Lowering RMP a couple hundred doesn’t make a lot of difference in airspeed, and trying to increase the RPMs a little doesn’t provide any more indicated airspeed either. Leaving the mixture in the full rich position or manually leaning it back doesn’t seem to make any difference either. Unless there is a tailwind, max groundspeed per Garmin 430 is 130kts. I’m based out of Phoenix Deer Valley, AZ. There have been a couple times when returning from a cross country that I decended from 10K or 12K to 4-5K MLS and the plane leveled out and continued at over 140kts IAS for over 20 nm. It surprised me that it continued at this speed – having to throttle back and slow down only before enter D airspace. Is this 110 IAS normal for SR20’s? What settings, altitudes, etc. are other SR20 owners flying at? A couple different shops have checked out the plane and it does’t seem to have anything configured or mechanically wrong.
When comparing performance, we generally use true airspeed (TAS). Indicated airspeed will vary significantly with altitude, and of course ground speed is useless for comparing performance due to winds.
What avionics do you have in your SR20? Do you have a TAS readout?
Also, I am not sure why you mentioned slowing down before entering Class D airspace. The speed limit in Class D is 200 KIAS within 4nm of the airport.
Go up to 7500 or 8500 at full throttle with 75 rich of peak and check your numbers. Mine we’re low and it turned out my pitot static system had a big leak, thus numbers were incorrect.
No no no no NO do not go 75* ROP. Call me. If you can’t access my phone listing, email me.
Flying LOP at 2650rpm between 6K’ and 10K’ at max gross weight I see ~ 140KTAS burning ~9.5Gph. Flying alone with half-full tanks the weight is at 2700lb and I see 147KTAS. In cold weather (which I fly 6 month/year) I see a few (2-3) KTAS faster. I usually see a good 5 KTAS drop flying in the clouds and 8 KTAS drop flying in the rain.
Depending on how heavily loaded you are and what are the OAT and flying conditions, your numbers may or may not be too low.
Alexander, he has a 2001 G1, I doubt he has the avionics to run LOP. Also the POH figures are 75 ROP!
You don’t run ANY engine, let alone his 360 at 75 ROP- especially a G1 of his vintage with zero cooling capability. I’ve got the data from oil analysis and JPI showing what happens. If he doesn’t know how, I’ll show him the quick and dirty way till he gets the proper instrumentation. But 75 ROP, absolutely no way in hell.
For a very expensive engine discussion at 50* ROP and 65% power - see this thread:
These are almost exactly the same speeds and fuel burn I’m seeing in my '01.
Cyler - do yourself a big favor and join COPA to see all the posts, Copapedia, maintenance ideas, etc. If you don’t agree it’s the best 60 bucks you have ever spent in aviation, lunch is on me.
If you do not have full engine monitoring, there are several paths available to upgrade; all explained in COPA posts. From there you can save a great deal of fuel/money by learning how to properly operate your engine LOP. 110 indicated does seem a bit off, particularly if your flying ROP by the book. But as was pointed out it, TAS that matters. Last week I tried a brief speed test at 2,500 from Naples, FL to St Augustine. Full fuel, 2 people & 30 lbs baggage, I was seeing about 151 KTAS; but I was burning nearly 14 gph to do it. Switching to LOP operation, I was seeing 140 KTAS at 9.5 gph. (Although I haven’t finished scraping 3 months of Chicago grit off the plane. It flies a bit faster when it’s clean & polished.)
I regularly see 141 to 144 kts @ 9.5 gph (LOP) at max weight.
Last weekend, I saw 143 to 145 at 7000 and 8000, and at 9.5 gph and about 2800 pounds.
Thanks for your reply. I have the “six pack steam gauges” and the basic single EGT & CHT. I don’t have a TAS readout, but roughly using the 2% rule the 110 IAS at 9000 feet would convert to about 130 TAS which seems to coincide with the ground speed off the Garmin 430.
I don’t know why I mentioned slowing down as I realize I don’t have to, but that’s usually what I’ll do. With Phoenix Deer Valley being the busiest GA airport in the country, there’s always a few students in the pattern. I usually enter the airspace at TPA and slow down to match their traffic pattern speed. I was just pleasantly supprised those couple times that I was “screaming in” at 140 IAS !!!
With the heat and density altitude, I may not be that far off with the airspeed. We’ll keep checking as we get into cooler weather. I was just wondering if I was doing something obviously wrong my power settings. Or, my other thought was that the prop was not properly changing for maximum effeciency in cruise. It does detent the RPMs during runnup though.
The broker I bought the plane from said to cruise at 2500 RPM and lean back to about where the manifold and fuel flow needles meet.(which I believe is about 23# and 9.5 GPH – I would have to check next time I’m at the plane to be sure) I appreciate all the comments here. It seems I should be getting and engine monitering system installed for all cylinders. Thanks again!
I’m not sure that I’m following…I routinely run 75% power ROP (also often run 75% power LOP). Unless I’m missing something, it’s right up the center of what’s in the POH.
Read this thread - and after that and the diagrams provided - YOU tell me is 75% and 75* ROP is a good place to operate.
Second to that - read THIS diagram and tell me if it is a good place to operate. If it takes more then 3 minutes to find the answer - call me: !(http://i145.photobucket.com/albums/r207/wolfala/Engine Related/Redfin.jpg)
I’m not telling you anything…I’m asking what you meant. For clarification, is “75% and 75*ROP” 75% power and 75 degrees ROP?
Based on the above diagram - where can you operate at 75% while ROP without breaking anything?
Based on the above diagram - where you you operate at 75% while LOP without breaking anything?
You said you operate at 75% ROP - where do you operate?
I operate at 75% power, 70 degrees rich of peak (my engine monitor only reasures egt in 10 degree increments).
Again, I’m not trying to question anything or argue anything. I’m just trying to understand what you’re saying.
He is saying that is a bad place to operate your engine for longevity/reliability. Please read the link he provided under the chart - it will explain it.
Cyler, the Garmin 430 has a TAS calculation function - in the Utilities group. You plug in your CAS, OAT etc. and it works it out for you.
I’m based down at Ryan (kryn) & I have a year 2000 sr20. I have a JPI in my plane & would be glad to go over the LOP procedure that I learned from these guy’s on the forum. (Alex, Gordon, Roger etc…) Give me a call (five two oh, fore oh five, eight eight three six) & you could come down & fly with me if you like. It’s a simple concept that will save you the cost of a new engine. The guy’s in COPA have a lot of great advice. By joining our group you will save the $65 many times over. Call me, I’ll be happy to help.