HOW IS THIS PERFORMANCE POSSIBLE?

Cooler weather has finally arrived in Florida. Not typical mid 90s, now low 80s.

I typically fly at 4,000 - 7,000 feet back and forth around the state. At max power cruise, leaned for Best Power, I amy seeing 190 - 195 knots TAS. I typically cruise at 2,500 RPMs and am regularly seeing 185 - 190 knots TAS.

How can this be? I only get this performace when at max cruise in the summer at around 2,000 feet while flying east from KORL to escape the Bravo shelf.

I thought something might have been wrong with my pitot system or something, but have crossed checked it agains the GPS page on the Garmin 430’s indicated Ground Speed and factoring in the wind component (i.e. speed and direction).

I am lovin’ it, but ain’t believin’ it.

MIKE
1-290229-N369MWPFD.jpg

In reply to:


Cooler weather has finally arrived in Florida. Not typical mid 90s, now low 80s.
I typically fly at 4,000 - 7,000 feet back and forth around the state. At max power cruise, leaned for Best Power, I amy seeing 190 - 195 knots TAS. I typically cruise at 2,500 RPMs and am regularly seeing 185 - 190 knots TAS.
How can this be? I only get this performace when at max cruise in the summer at around 2,000 feet while flying east from KORL to escape the Bravo shelf.
I thought something might have been wrong with my pitot system or something, but have crossed checked it agains the GPS page on the Garmin 430’s indicated Ground Speed and factoring in the wind component (i.e. speed and direction).
I am lovin’ it, but ain’t believin’ it.


Mike,

Do you have TKS? And what is the age of your plane?

Your speedometer is calibrated in MPH rather than Knots

In reply to:


Cooler weather has finally arrived in Florida. Not typical mid 90s, now low 80s.
I typically fly at 4,000 - 7,000 feet back and forth around the state. At max power cruise, leaned for Best Power, I amy seeing 190 - 195 knots TAS. I typically cruise at 2,500 RPMs and am regularly seeing 185 - 190 knots TAS.
How can this be? I only get this performace when at max cruise in the summer at around 2,000 feet while flying east from KORL to escape the Bravo shelf.
I thought something might have been wrong with my pitot system or something, but have crossed checked it agains the GPS page on the Garmin 430’s indicated Ground Speed and factoring in the wind component (i.e. speed and direction).
I am lovin’ it, but ain’t believin’ it.
MIKE


I’ve seen in the upper 180s in my G1 (no TKS) flat out… I’ve also seen as much as 183KTAS at 12k sipping less than 13GPH (around peak that day) and close to 180KTAS at 15K on 11.8GPH. We are definitely beating book too…

Maybe your throttle lever is bent and allowing you to give it more power?

Just out of curiosity, why is this posted in the guest area, everyone participating in the discussion is a COPA member.
I rarely check the guest forum (there is sooooo much great info on the inside for those of you folks thinking of joining), and think maybe i am not alone. you might have better responses posted in the SR forum.
BTW, you don’t have alt static on by any chance?

i am not saying that you are mistaken but there can be issues with calibration that result in inaccurate TAS calculations. One source may be the OAT input which is derived from the probe but on the Cirrus installation is not displayed. If you want to get accurate info you need to record temp/alt settings/ and ground speeds in approximately the same area in 90 deg radials (90/180/270/360). with that info the true TAS can be approximated. But all in all if it gets you where you’re going when you want to be there does a few knots make that much of a difference?

Nope, all the number are correct. The computer uses the heading and IAS compared with the GS and track to calculate the wind. I used an E6B (remember those?) and ran the numbers, they are all good. The only other possibility would be that the airspeed indicator is not accurate.

Did you recently wash or wax your plane?

In reply to:


Cooler weather has finally arrived in Florida. Not typical mid 90s, now low 80s.
I typically fly at 4,000 - 7,000 feet back and forth around the state. At max power cruise, leaned for Best Power, I amy seeing 190 - 195 knots TAS. I typically cruise at 2,500 RPMs and am regularly seeing 185 - 190 knots TAS.
How can this be? I only get this performace when at max cruise in the summer at around 2,000 feet while flying east from KORL to escape the Bravo shelf.
I thought something might have been wrong with my pitot system or something, but have crossed checked it agains the GPS page on the Garmin 430’s indicated Ground Speed and factoring in the wind component (i.e. speed and direction).
I am lovin’ it, but ain’t believin’ it.
MIKE


Have you checked the calibration of your airspeed indicator? Mine is about 2 KTAS high, yours may be more. This nifty little program does the calibration.

http://www.csgnetwork.com/tasgpscalc.html

My SR22 picked up about 8 knots suddenly once. I also noticed that the winds didn’t add up: I had headwinds both outbound and on the reciprocal leg, just 30 minutes apart.

Turns out I had a static leak, where the altitude encoder connects to the static line.

The static leak made my indicated airspeed too high, which made my true airspeed too high. The winds are calculated to make the true airspeed and heading match up to the groundspeed (which, being GPS derived, should always be very accurate) and ground track.

Some symptoms of a static leak: opening and closing alt static have no effect on airspeed and altitude, opening and closing cabin vents change airspeed and altitude. If you’re on altitude hold with the autopilot, you can cause it to start climbing by opening the air vent!

-Mike

In reply to:


Cooler weather has finally arrived in Florida. Not typical mid 90s, now low 80s.
I typically fly at 4,000 - 7,000 feet back and forth around the state. At max power cruise, leaned for Best Power, I amy seeing 190 - 195 knots TAS. I typically cruise at 2,500 RPMs and am regularly seeing 185 - 190 knots TAS.
How can this be? I only get this performace when at max cruise in the summer at around 2,000 feet while flying east from KORL to escape the Bravo shelf.
I thought something might have been wrong with my pitot system or something, but have crossed checked it agains the GPS page on the Garmin 430’s indicated Ground Speed and factoring in the wind component (i.e. speed and direction).
I am lovin’ it, but ain’t believin’ it.
MIKE


Mike: This may be a stupid question but how are you computing your TAS?

I few years ago, OK, more than a few, but when the Cirrus were new, I met an owner who claimed that his '22 always exceeded book. His method to figure out his TAS was to first use the slide rule part of the Airspeed Indicator (Yes, pre-pfd) and then took that number and feed that into the Garmin for its TAS computation. Essentially, he took adjusted the TAS for pressure altitude again. He also experienced TASs about 10 knots more than expected. I asked him if he encountered a lot of headwinds, and he said, “Always.” [:)] I couldn’t bust his bubble of having the fastest SR22 in the fleet.

I do have TKS and I took delivery in May 2006

Nope, it says TAS 192 KTS (that would be knots last time I checked)
1-290678-PFDOct.172007KOPFtoKORL.jpg

Michael-

Even though your FF is a bit high, you have a rocket; maybe the fastest in the fleet. Thanks for posting the picture!

Michael-- KTS is not knots–KTS is Know The Speed----
Dennis The Menace was right—knowing your speed is MPH [;)] [:)]
couldnt resist!!

On second glance, I noticed that your TAS is 192, yet your GS is 179 with the wind at 11 knots about 20% off the nose of your plane. I don’t have an EFB handy but would think that your TAS should be in the mid 180 range. So I now question whether your TAS is, in fact, accurate. Anyone out there have any ideas as to why this discrepancy?