Hmm. I do clean it pretty often - roughly every 3 flights. I wipe the painted areas down with Zaino Grand Finale spray, diluted 50% with distilled water. I use Simple Green motorsports formula on the wheels and wells. It's often enough that a few people at the airport have mistaken me for the local detailer and asked what I charged. I just look at them and tell them that they can't afford it.

I always run at 102.1 N1 unless it's a super hot day. ITT is ~665C in August. Limitation is 670C in cruise and I bought this thing to go fast!

Tarver, do you think the weight loss and rearward CG shift from the glass panel makes a material difference? My BEW is 7,151.

You are definitely light, no thrust reversers, aft CG and probably very well rigged. Just be careful with the temps, none of these high turbine blades like above 650 IMO in the long run.

Noted! I will dial it back a bit when it's hot out.

You might be going fast through HT blades as well.

I never see over 640, and often I cruise under 620. If I saw 665 I would be concerned simply because that's abnormal for my plane.

Maybe the -5A engine just runs cooler on my plane than the -1A on the 501.

Mike C.

Limitations on the -1A are 700C for 5 min (Take-Off), 680 Climb, 670 Cruise. Do you cruise at MCT or something less? 102.1 N1/95 N2 is MCT for the -1A. I'll take Tarver's advice and aim for 650. Won't be hard in the winter - it was only at 655 on the above "record" run. The 665 was from a picture of the gauges I had taken back in August. It is HAWT here in the South and we're often heading down to Houston or Gulf Shores where it's even hotter than here.

Chris, that's considerably above book. So much so that I'm wondering if there was instrument error somewhere. Do you recall what your fuel flow was?

From your other posts about this flight it appears that OAT was likely close to ISA, your weight was about 9,500lbs, N1 was 102% and the CG was in mid-range. Book gives TAS of 354 kts at a fuel flow of 905 lbs/hr. A drop to ISA-10 still gives 354 kts at 102%, but fuel flow increases to 946 lbs/hr.

A decrease in weight by 1,000 pounds to 8,500 lbs will give an increase in TAS by 4 kts to 358 kts. So, even a full aft CG (which you did not have) would not seem to give a tremendous boost to TAS.

Unless the Cessna manual is quite conservative, 372 kts TAS seems hard to achieve with the given parameters. Therefore I would investigate possible instrument error. If you are running the engines too hard due to engine instrument miscalibration, that would be a major concern.

Chris,
Was your speed consistent throughout the flight? You were downwind from the Rockies so your nice speed could be mountain wave effect.

Chris' speed totally jives with what I experienced when I owned his airplane. On many occasions I was like, "how does a 501 go this fast?".

But, back to Mike C's HT blade comment, the 5A and -4 runs a little cooler than the 1A (they have an extra booster hub behind the front fans). I've lost track of how many Citation engines I've rebuilt, probably 75, and it's somewhat of a mystery to make cool runners or hot runners. There are so many different stator classifications that it's somewhat luck/trial and error to get them to flow probably so that the N1 and N2 are in a happy balance for coolness. You also have to get the right tip clearance between the HT blades and outer segments. You can speed up the N2 by selecting a more open low turbine stator to make it run cooler but if you go too big it doesn't make max power. Unfortunately there's no magic formula.

But, Chris has the latest and greatest single crystal blades that are less prone to failure than the first generation blades. Almost all the 550 and 560 motors have the improved blades and the fact that they run cooler helps them out. These motors also often have Nickel vs Cobalt HT stators that are less prone to cracking than 1A stators.

Just like Continental cylinders, cool jet engines last longer than hot jet engines.

mine was too.

Here's a couple of pics of mine at FL390. TAS 333, N1 setting 102.1, temps in the low 600's. This was pretty typical. Mine was light with no reversers, new paint and ceramic coating. I really wonder how you get a 30 knot speed bump. Not questioning it just jealous. Thats a huge difference.

I think this is my fastest TAS in the V.

Hi Ian,

My fuel flow was 1,000 lbs/hr. I had pitot static done last Fall and everything passed there so I assume that my G600 is reporting accurate info.

I don't have any reason to think that my ITT gauges are in error but I am new to jets and aircraft ownership in general. My plane has both digital and tape N1 and N2 gauges. The N1 gauge is driven off of its own input - I recall from reading that N1 tape will still work even without power as it is driven off of its own tach generator. I've never gone beyond 201/1 N1 or 95 N2. I always hit the N1 limit before N2. I know the -1B engine allows a higher N1 so maybe N2 could become a limitation with that engine.

Hi James,

I have nothing to compare it to - that's why I love tapping the brain trust here.

Sounds like the only differences in our planes was all glass vs partial steam in yours. Mike C reported that they took out 380lbs from the nose when they did the glass in his V. I don't think that accounts for 30 kts but maybe a little?

Question for the brain trust - confirm or fix my statements below:

GS was 505 - that is GPS derived so we believe it is correct.
TAS is 372 - that is calculated by the ADC. Since my plane passed pitot static recently we believe that is correct.
Tailwind component is 131 - I would think that's a simple GS +/- TAS calculation but using the above numbers that would mean a 133 tailwind component while 131 is listed. Or if we assume that the tailwind component is correct, then using some algebra the TAS should be 374. Maybe there is some smoothing built in to the wind component display?

What I'm trying to tease out is where the possible error could come from? Assuming all of the numbers on the G600 are correct, the possibilities are that there is some magic in my plane (a little straighter, a little more slippery, etc) or I'm overrunning my engines. Now I would think that the only way to get higher than rated thrust (assuming that is what they used in the book) would be to run N1 above 102.1 (since that is where the bulk of your thrust comes from) and/or N2 above 95 (you get some thrust from gas expanding out the rear so a higher N2 would add to total thrust). I am very careful to keep from overspeeding N1 or N2. I should have grabbed a shot of the engine gauges at the same time - didn't think about it at the time.

Lighter weight plus rearward CG add speed due to less induced drag.


Yes, it will be highly accurate.


You don't really know. ADC derived indicated airspeed depends on two things, accurate static pressure and accurate pitot pressure. Airplane installation, probe, and measurement error all contribute to errors in ADC readings. Beyond that, true airspeed also depends on temperature. So there are a lot of variables and opportunities for introducing errors. For example, the pitot can't be installed so that it is directly into the slip stream since that varies with weight and speed.

BTW, pitot is NOT tested during your static/transponder tests.


The wind display confuses a lot of people. Many assume that TAS + wind = GS. Not so. TAS and wind are relative to your heading. GS is your course. In your case, they are pretty close, a course of 094 and a heading of 099. But that difference can make the 2 knot variation you noticed.


N1 is a pretty reliable and accurate measure of your thrust.

If you really want to know how accurate your true airspeed is, you need to do a GPS airspeed test.

Best discussion on this is at the National Test Pilot School, see "Using GPS to Determine Pitot-Static Errors":

https://www.ntps.edu/information/downloads.html

Start here:

https://www.ntps.edu/images/stories/doc ... method.doc

You will need to find a place to do some steady, smooth tracks in a pattern and note your GS and course. Turbulence or variable winds aloft are not good for this test.

There is a second way to do this with somewhat less accuracy, but you don't have to fly any special pattern. This method uses upper air soundings that are done every 12 hours at various specific locations. The accuracy of this method is best when you fly very near one of these locations very near the time they take the measurements.

Here is where you can get the data:

https://weather.uwyo.edu/upperair/sounding.html

From the soundings, you can get an accurate winds aloft. You then compare your flight conditions (GS, course, heading) at that same time and spot. Now you can use the winds aloft to figure out what your true airspeed was.

You can kind of do this after the fact by looking at the ADS-B track airspeeds.

For example, your photo appears to be this flight:

https://flightaware.com/live/flight/N50 ... /KAXX/KRVS

With track:

https://flightaware.com/live/flight/N50 ... S/tracklog

It was taken very near KHHF, and thus this track entry is the best results at the moment:

Mon 23:20:06 35.8427 -100.3900 → 99° 505 34,975 Level FlightAware ADS-B (KELK)

Time (2320Z) also matches as well as the GS of 505 knots.

Now the trick is to find wind data. Your are very close to 0000Z and to KAMA where the soundings take place, so let's just use that data from Jan 17 0000Z. It is 40 minutes later and 75 nm away, so not exact, but it will be moderately close. It was actually probably quite close to your position since the balloon goes with the wind.

This is the sounding:

Since this is flight level, need to convert FL350 to absolute pressure, which is 238.4 hPa. The closest entry is:

238.0 hPa, -52.5 C, winds 267 (true not magnetic) at 137 knots.

That's pretty much a direct tailwind, so 505 GS minus 137 knots tailwind is 368 knots.

The winds aloft method is not nearly as accurate as the GPS course method, but it provides a basic sanity check and works after the fact.

One thing I noticed is that your display shows TAT as -21F. Real pilots use C, of course :-). That's -29 C. At FL350 and 210 KIAS, the ram air rise is about 17 C (per my AFM). So the static air temperature is -46 C from your measurements. But the winds aloft data said -52.5 C, or somewhat colder. This seems like a meaningful error and maybe explains why you get higher than expected true airspeed readings, your temperature indications seem a bit off. Misreading temperature high causes airspeed to be overestimated.

Mike C.

Thank you for breaking this down! 368 is pretty close to 372 so it's in the ballpark.

As for using temps in F, the CAE abbreviated checklist that came with the plane lists everything in F, so that is what I go with (and likely why the plane was set to display in F in the first place).

The temp difference from expected is interesting. I think there is a way to switch between the different temp readouts on the G600. I will try to mess with that next time I'm in cruise for a while. I will also try to cross check with the copilot's side since it should be using its own ADC.