Our new Rocket

[bradp]

This application would benefit from single or dual G5.  Either way you get a backup or two .  Since the century 41 requires and attitude source for the autopilot the only thing you could not do is remove the Vacuum AI.  Since there’s no FD the autopilot AI is allowed to go to the turn coordinator position. Dual G5 and Vacuum AI would get you three redundant sources of attitude info.  Kind of like kpaul’s F.  

[Gavin Woodman]

I am looking forward to getting our GEM up and running properly so that I can to a proper lean check. I'm guessing either an injector swap or GAMI's will be in order, but once done, I look forward to running LOP. We also have a T210 that we run exclusively LOP without issue. Typical cruise power setting on that bird is 30" 2450RPM and 15.7GPH with TIT at about 1590F. It's probably about 10+KTS slower than running ROP but we love the economy. For the Mooney, it's about gaining payload as much as about lower cost per mile.

[jetdriven]

On 12/25/2018 at 6:48 PM, carusoam said:

Restarting a TC’d engine at altitude is worth learning about...

a failed TC or lost hose connection happens...

The engine’s CR doesn’t allow for restart until lower...  

know that it will restart, under the well known conditions...

Unfortunately, there isn’t a good way to practice this experience...

Best regards,

-a-

It’s not just that, but the fuel control unit schedules fuel for the throttle lever angle and expected MP. When the turbo quits or an induction hose comes loose, the MP goes from 33” to 12”, and the engine floods out and shuts down due to a 20 GPh fuel flow when it should be 8.  Pulling the throttle back and leaning should re-light the engine if it’s below 18-20k feet. 

[aviatoreb]

On 12/29/2018 at 10:52 AM, Jeremy95 said:

Just a couple days ago I decided to try the 72% power setting on my way back from Dallas and found that at 19 gal/hr kept my tit at about 1560-1570 after adjusting for temp correction. 

I’ve also tried some LOP at 55% power. If anyone has gamis, I’m curious to compare. At lower alt (8500 ft) I have gotten it to run smoothly at about 11.5 gal/hr and approx 155 Ktas. The biggest problem I’ve seen though is tit is right up against limits and at higher altitudes tit starts creeping up to a point where I can’t run LOP at all. I am considering buying gamis but was hoping for some real world experience and tit numbers to find out if it’s worth the cost.

I’m sure most of you guys are already tracking but one of the biggest frustrations  I had early on was hot starting. I read the Mike Busch article (https://www.avweb.com/news/airman/184350-1.html) prior to buying the airplane so I was expecting it but what seems to work the best for me is a combination of the articles recommendation and the rocket manual. I use mixture cutoff and full throttle with 30 seconds of primer. Push the mixture back in and give it about 3 seconds of primer. Then pull throttle to a little above idle and mixture to cutoff. I start cranking the engine while smoothly feeding in mixture until it fires. Not sure that’s the best technique out there but it has worked for me every time.

Your fuel flows just seem a bit lower than mine and lower than what I read in book fuel flows. My 72% book says 20gph and I get maybe 20.+ maybe 20.2 or 20.4 ROP (2300 31'').  I am wondering what's different?

I got to 0.4gph difference by swapping around injectors so never bothered to get GAMIs.  It runs smooth lop but I find as you, the tit wants to get hot. That's not a symptom of imbalanced injectors is it?  Anyway I don't often run LOP and when I do its maybe 55% so that the TIT doesn't end up too hot (then I'm at 1580-1600 depending), but then Im going maybe 170TAS.  If I try to go high power settings LOP then the TIT gets much hotter like 1630, 1640.... getting very close to the 1650 peak so I just don't do it.

Are you computing your 55% correctly? 100*  13.7 hp/gal * 11.5 gal /305 hp max = 51.6%.  But 100*  13.7 hp/gal * 12.5 gal /305 hp max = 56%.  So maybe my 55% LOP is faster than yours because a) when I do it Im going a long ways trying to stretch my tanks so I'll tend to be higher, and also, you are running 51% and I'm running 56%.  It will even do close to 180 on that fuel flow as you get even higher.

[FloridaMan]

On 12/29/2018 at 10:52 AM, Jeremy95 said:

Just a couple days ago I decided to try the 72% power setting on my way back from Dallas and found that at 19 gal/hr kept my tit at about 1560-1570 after adjusting for temp correction. 

I’ve also tried some LOP at 55% power. If anyone has gamis, I’m curious to compare. At lower alt (8500 ft) I have gotten it to run smoothly at about 11.5 gal/hr and approx 155 Ktas. The biggest problem I’ve seen though is tit is right up against limits and at higher altitudes tit starts creeping up to a point where I can’t run LOP at all. I am considering buying gamis but was hoping for some real world experience and tit numbers to find out if it’s worth the cost.

I’m sure most of you guys are already tracking but one of the biggest frustrations  I had early on was hot starting. I read the Mike Busch article (https://www.avweb.com/news/airman/184350-1.html) prior to buying the airplane so I was expecting it but what seems to work the best for me is a combination of the articles recommendation and the rocket manual. I use mixture cutoff and full throttle with 30 seconds of primer. Push the mixture back in and give it about 3 seconds of primer. Then pull throttle to a little above idle and mixture to cutoff. I start cranking the engine while smoothly feeding in mixture until it fires. Not sure that’s the best technique out there but it has worked for me every time.

Are you sure your TIT gauge is reading accurately? Have you run the test procedure from the manual? Also, for hot starts, I go full lean, throttle full open and prime for a full minute, then mixture full rich and prime for a few seconds and then pull the throttle out and she starts up every time without issue. Even on the ground in Sedona after spending 90 minutes at lunch. Have you read the Continental publication Tips on Engine Care that explains the whys and how’s of a hot start?

[Jeremy95]

To clarify, I was running the 55% ROP numbers from the rocket chart and leaning to LOP so like you said, more like 51% actual power. That seems to give me somewhere around 155 KTAS  maybe a little bit faster but in that ballpark. 19 gal/hr is on the rocket chart for 72% power as the min fuel flow. I’m guessing that on a much hotter day at a higher altitude I would probably have to increase fuel flow to get those tit numbers but I haven’t tried that out yet.

I have run the tit check from the rocket manual and have two tit sources so I’m fairly certain the numbers are good. My biggest question is would the tit decrease with gamis. Right now I have about a 60-80 degree split between the egt on my hottest and coolest cylinder according to my jpi. In my mind it would seem a smaller split between egts I would potentially average out to a lower tit for any given power setting and fix the high tit. I would love to buy some gamis but if I’m going to continue bumping up against tit limits then I’m not sure it’s worth the cost.

[aviatoreb]

23 minutes ago, Jeremy95 said:

To clarify, I was running the 55% ROP numbers from the rocket chart and leaning to LOP so like you said, more like 51% actual power. That seems to give me somewhere around 155 KTAS  maybe a little bit faster but in that ballpark. 19 gal/hr is on the rocket chart for 72% power as the min fuel flow. I’m guessing that on a much hotter day at a higher altitude I would probably have to increase fuel flow to get those tit numbers but I haven’t tried that out yet.

I have run the tit check from the rocket manual and have two tit sources so I’m fairly certain the numbers are good. My biggest question is would the tit decrease with gamis. Right now I have about a 60-80 degree split between the egt on my hottest and coolest cylinder according to my jpi. In my mind it would seem a smaller split between egts I would potentially average out to a lower tit for any given power setting and fix the high tit. I would love to buy some gamis but if I’m going to continue bumping up against tit limits then I’m not sure it’s worth the cost.

Ah. I see where you are looking in the POH.  There are two numbers next to every fuel flow setting.  For example it says 20 (19) on the 72% line.  But then in the subscripts below it says essentially (**do not exceed 1650**) which I interpret as the in parenthesis setting, in this case (19) for 72% is the do not exceed fuel flow setting.  But the healthy setting for the same 72% is suggested at 20gph.  That's my reading of how the POH is written. And sure enough. At 20gph Ill get like 1570 or 1590 depending on atmospherics and maybe 1550 at 20.2 which makes me happier.  And by the way I live in a very cold climate (look where kptd is) and this tit feedback is true even in the winter.

I don't know - I would love to find out if changing to highly balanced GAMI's leads to lowered TiT.  I have not gotten the game's for the same reason as you  mentioned.  At 0.4gph I am still tit limited so I figured I wasn't going to bother getting gamis and running LOP all the time anyway.  Other than occasionally at low power settings.  It sure would be fun to be able to run LOP at 80% eh.  It sure would be a screamer.

[kortopates]

Gami’s can only improve mixture distribution- not lower TIT. But note what happens if you have a lean outlier that is pushing up TIT on the ROP (opposite would be true on the LOP side).if get that lean outlier fixed (more balanced) you won’t have that higher EGT pushing up the TIT, so indirectly in some cases they may actually lower TIT - but not directly.


Sent from my iPhone using Tapatalk

[carusoam]

Looking at EGTs and TITs for a minute... for balanced and unbalanced FIs...

Balanced... <0.5 gph, first minus last to peak... (somewhat arbitrary, well balanced is 0.1 or less)

• They all run Either ROP, LOP, or at peak at the same time...

Unbalanced... >0.5 gph, first to last... (pretty crummy for running LOP

• when running near peak, some will be slightly LOP, and others may be ROP...
• some have excess fuel leaving the cylinder, other leaving excess oxygen...

It is  quite  possible that a quirky imbalance leaves O2 and fuel to combust in the exhaust system...

• When fuel is still burning in the exhaust, the TIT will appear to rise...

Keep in mind, TIT is a very quirky average measurement... Hot exhaust gasses are coming through in waves or pulses, the TC is measuring the average over time... there would need to be a real quirky imbalance of FF in the various FIs to make this happen...

So what is the Gami spread you guys are seeing?

A nice digital engine monitor can really add confusion to the discussion...

• 6 EGTs running around 1200°F are in each of the separate exhaust tubes...
• Magically the TIT is reading a number like 1650°F...
• The EGTs are not accounting for a lot of time off between exhaust strokes...
• The TIT doesn’t get a lot of time off as six exhaust pulses are impinging on the same TC in the same amount of time...
• Looking at going 100°F either LOP or ROP... lowers the peak temp of the pulses coursing through the exhaust tubes...
• You would really need nicely balanced FIs to go 100°F LOP.

PP thoughts only, follow Paul’s advice above... having a bad gami spread might indicate a blocked FI...

Best regards,

-a-

[FloridaMan]

You also have an increase in pressure and, as a result, increase in temperature as the exhaust collects at the turbine inlet. Your fuel mixture burns more slowly when running lean so more timing advance (or perhaps fine wire plugs) would help to reduce the amount of combustion exiting the exhaust valve.