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02 Jul 2020, 01:55 [ UTC - 5; DST ]





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 Post subject: Re: Flying the Epic LT
PostPosted: 07 Feb 2020, 21:18 
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Username Protected wrote:
Beautiful panel ideas Neema!.
You mentioned that you'd like to fly in a plane with a G3X and Garmin auto pilot combo. If an A36 with a G3X and a GFC500 will meet your needs, come on down to Fullerton. I'd be happy to take you up - especially if I can check out your Epic - That thing is awesome!


John, kind of you to offer. I’ll shoot you a message next time I’m headed down south. I’m planning on riding in an LT with the G3X + Garmin AP, but would love to see your plane as well. How do you like your setup?


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 Post subject: Re: Flying the Epic LT
PostPosted: 07 Feb 2020, 21:37 
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The G3X and GFC combo are incredibly impressive. I flew G1000 equipped Cessnas quite a it before buying my A36. In my opinion, the G3X is a step up from the G1000s I used to fly behind.

My previous autopilot was an S-Tec 30 - it was a very good autopilot with altitude hold and GPSS (wouldn't capture an altitude or manage a glideslope). The GFC does everything better. Drop the gear while going down an ILS and you feel none of hte hunting for attitude that I used to experience in a 182. It's very impressive


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 Post subject: Re: Flying the Epic LT
PostPosted: 04 Mar 2020, 16:03 
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Got to fly in a G3X and Garmin autopilot Epic LT. It's the best AP flying experience I've seen (and felt) in an LT.

Everyone speculated the lack of torque on Garmin GSU 28 servos would be an issue. G3X has been out for a while now, and because of the speculated low servo torque, no one wanted to be first to try them in an LT (myself included). I think it was only a matter of time before LT owners became too enticed. G3X product support and development is excellent and it's offered at a great price point.

After checking our how the plane flew, I can recognize where there are issues but they're not deal breakers. They're all AP torture scenarios. If you drive sensibly, no issues.

Examples:
You can notice insufficient servo torque if you give it a fistful of power from low speed/low power setting. The yaw damper does an excellent job of keeping the plane pointing forward but will be half a ball stepped out until trim can catch up and help (and the rudder becoming more effective w/ airspeed). Important thing is that the feeling in the back is still pretty imperceptible, so I'm not sure how much it matters.

Another issue noticed was busting through altitudes when in high climb rates. 4500 fpm will overshoot your bugged altitude by 200'. Slow the climb rate to 2500 fpm and it captures just fine. The fix could easily be a future software release. Higher climb rate should command an earlier pitch down input to level off sooner. Just like hand flying. Frankly, 4500 fpm is a low altitude Vy climb. I never do that just to level off abruptly

Garmin: sell your high torque servos for G3X planes with higher control forces!

It's a lot of work to pull everything out and a crying shame that a G900X Epic LT is only a GFC 700 away from being an excellent platform. It's also a shame there isn't compatibility with Garmin's G3X AP and G900X. Time to move on.


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 Post subject: Re: Flying the Epic LT
PostPosted: 04 Mar 2020, 17:17 
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Username Protected wrote:
Got to fly in a G3X and Garmin autopilot Epic LT. It's the best AP flying experience I've seen (and felt) in an LT.

Everyone speculated the lack of torque on Garmin GSU 28 servos would be an issue. G3X has been out for a while now, and because of the speculated low servo torque, no one wanted to be first to try them in an LT (myself included). I think it was only a matter of time before LT owners became too enticed. G3X product support and development is excellent and it's offered at a great price point.

After checking our how the plane flew, I can recognize where there are issues but they're not deal breakers. They're all AP torture scenarios. If you drive sensibly, no issues.

Examples:
You can notice insufficient servo torque if you give it a fistful of power from low speed/low power setting. The yaw damper does an excellent job of keeping the plane pointing forward but will be half a ball stepped out until trim can catch up and help (and the rudder becoming more effective w/ airspeed). Important thing is that the feeling in the back is still pretty imperceptible, so I'm not sure how much it matters.

Another issue noticed was busting through altitudes when in high climb rates. 4500 fpm will overshoot your bugged altitude by 200'. Slow the climb rate to 2500 fpm and it captures just fine. The fix could easily be a future software release. Higher climb rate should command an earlier pitch down input to level off sooner. Just like hand flying. Frankly, 4500 fpm is a low altitude Vy climb. I never do that just to level off abruptly

Garmin: sell your high torque servos for G3X planes with higher control forces!

It's a lot of work to pull everything out and a crying shame that a G900X Epic LT is only a GFC 700 away from being an excellent platform. It's also a shame there isn't compatibility with Garmin's G3X AP and G900X. Time to move on.


I don't think they can easily use the higher torque servos. The GSA 28 servos used in the G3X and GFC500 are CANBUS units.

The higher torque GSA 8X series are RS485.

Was a GFC 600 not an option?


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 Post subject: Re: Flying the Epic LT
PostPosted: 04 Mar 2020, 23:16 
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Username Protected wrote:
I don't think they can easily use the higher torque servos. The GSA 28 servos used in the G3X and GFC500 are CANBUS units.

The higher torque GSA 8X series are RS485.

Was a GFC 600 not an option?


GFC 600 is just like GFC 700s: developed in house by Garmin specifically for each airframe. Don't think they'll get around to experimental stuff. GSA 28s work, I just don't think it's optimal. G3X still seems to be the best platform moving forward given there are some fun solutions out now to work with trim actuators and Enviro's pressurization controller (needs ARINC 429 landing field data)


In other news, got a new phone with much better low light capability. Cool to capture the light coming from the exhaust stacks at night
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Also, Extreme Simple Green is really awesome for cutting through hours of soot build up. Dilute it and it melts away.

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 Post subject: Re: Flying the Epic LT
PostPosted: 04 Mar 2020, 23:21 
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Was a GFC 600 not an option?
Don't think it matters for servo torque, I believe Garmin has said the 500 and 600 servos are equally powerful, the difference is in environmental packaging.


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 Post subject: Re: Flying the Epic LT
PostPosted: 05 Mar 2020, 09:29 
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Username Protected wrote:
I don't think they can easily use the higher torque servos. The GSA 28 servos used in the G3X and GFC500 are CANBUS units.

The higher torque GSA 8X series are RS485.

Was a GFC 600 not an option?


GFC 600 is just like GFC 700s: developed in house by Garmin specifically for each airframe. Don't think they'll get around to experimental stuff. GSA 28s work, I just don't think it's optimal. G3X still seems to be the best platform moving forward given there are some fun solutions out now to work with trim actuators and Enviro's pressurization controller (needs ARINC 429 landing field data)


You are right, just looked it up (I have not installed a G600 yet, my TBM will be the first one I do). Each airframe has a custom software load.

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 Post subject: Re: Flying the Epic LT
PostPosted: 05 Mar 2020, 09:43 
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Was a GFC 600 not an option?
Don't think it matters for servo torque, I believe Garmin has said the 500 and 600 servos are equally powerful, the difference is in environmental packaging.


You are right, their docs say 60 in/lbs for each. The GSA 87 just looks bulkier.....

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 Post subject: Re: Flying the Epic LT
PostPosted: 05 Mar 2020, 10:00 
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Don't think it matters for servo torque, I believe Garmin has said the 500 and 600 servos are equally powerful, the difference is in environmental packaging.


You are right, their docs say 60 in/lbs for each. The GSA 87 just looks bulkier.....


For comparison, on my TBM, the KC325 pitch servo slip clutch is set to 55 in/lbs.

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 Post subject: Re: Flying the Epic LT
PostPosted: 05 Mar 2020, 14:26 
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You are right, their docs say 60 in/lbs for each. The GSA 87 just looks bulkier.....


For comparison, on my TBM, the KC325 pitch servo slip clutch is set to 55 in/lbs.


GSA 87 definitely looks bulkier, and I'd welcome them for the better packaging like Dave mentioned. C'est la vie.

G600 should be awesome in a TBM, Terry. I'd be thrilled to put that in.

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 Post subject: Re: Flying the Epic LT
PostPosted: 13 Mar 2020, 14:55 
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I have a real world comparison of the Epic vs. Meridian. An Epic departed 5 mins after me and landed 3 minutes before me on a short 100nm flight earlier this week. I climbed 2,000' higher which may have accounted for about a minute of the 8 minute spread. These were same day same time comparisons, so I thought some here might find it interesting. 8 minutes faster is pretty dang fast on a 34 minute flight. Interestingly, the Epic shut down and restarted within less than 10 minutes (seemed closer to 5). Do the Epics not have hot-start concerns for some reason?

https://flightaware.com/live/flight/N31 ... /KSCK/KTRK

https://flightaware.com/live/flight/N72 ... /KSCK/KTRK


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 Post subject: Re: Flying the Epic LT
PostPosted: 13 Mar 2020, 16:22 
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Username Protected wrote:
I have a real world comparison of the Epic vs. Meridian. An Epic departed 5 mins after me and landed 3 minutes before me on a short 100nm flight earlier this week. I climbed 2,000' higher which may have accounted for about a minute of the 8 minute spread. These were same day same time comparisons, so I thought some here might find it interesting. 8 minutes faster is pretty dang fast on a 34 minute flight. Interestingly, the Epic shut down and restarted within less than 10 minutes (seemed closer to 5). Do the Epics not have hot-start concerns for some reason?

https://flightaware.com/live/flight/N31 ... /KSCK/KTRK

https://flightaware.com/live/flight/N72 ... /KSCK/KTRK


From the tracks he departed 5 minutes after and landed 3 minutes after (9:30->10:07 vs 9:35->10:10)

That's only 2 minutes difference.


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 Post subject: Re: Flying the Epic LT
PostPosted: 13 Mar 2020, 17:03 
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Username Protected wrote:

From the tracks he departed 5 minutes after and landed 3 minutes after (9:30->10:07 vs 9:35->10:10)

That's only 2 minutes difference.


I have a hunch that it's more accurate to compare first and last ADS-B returns rather than using FlightAware's arrival time. 8 minutes is still peanuts though for that short of a flight.


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 Post subject: Re: Flying the Epic LT
PostPosted: 13 Mar 2020, 18:21 
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I have a real world comparison of the Epic vs. Meridian. An Epic departed 5 mins after me and landed 3 minutes before me on a short 100nm flight earlier this week. I climbed 2,000' higher which may have accounted for about a minute of the 8 minute spread. These were same day same time comparisons, so I thought some here might find it interesting. 8 minutes faster is pretty dang fast on a 34 minute flight. Interestingly, the Epic shut down and restarted within less than 10 minutes (seemed closer to 5). Do the Epics not have hot-start concerns for some reason?

https://flightaware.com/live/flight/N31 ... /KSCK/KTRK

https://flightaware.com/live/flight/N72 ... /KSCK/KTRK


From the tracks he departed 5 minutes after and landed 3 minutes after (9:30->10:07 vs 9:35->10:10)

That's only 2 minutes difference.


Actually if you look at the track log you'll see that I departed at 9:30 and landed at 10:04 (34 mins). The Epic departed at 9:35 and landed at 10:01 (26 mins). I think because his quick turn was so fast it messed with flightaware's programming and it thought his time on the ground was still flight time. By 10:10 he had already shut down, loaded/unloaded a passenger, restarted, taxi'd out and was back in the air. 8 minutes isn't much, even for short flights like this (which is why I own a Meridian), but it was still pretty impressive. I was watching him overtake me on the iPad and have had similar flights such as this with TBM's and they haven't overtaken me as quickly as the Epic did.

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 Post subject: Re: Flying the Epic LT
PostPosted: 20 Mar 2020, 00:14 
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Giving myself something else to think about outside of CV19. Here's my best guesstimate predicting flight at FL340 and the RVSM substantiation test flight... whenever we may get around to that.

I don't have my hands on E1000 performance data (yet), but we can find a decent proxy for higher altitude engine data from the Beech Starship POH.

Here's a snapshot from the older style engine air inlet LT at cruise, mid weight, close to ISA temps (cabin was nice and tight that day tickling the max diff P warning):
Attachment:
IMG_1144.jpg


And here's a page of normal/recommended cruise from the Starship at similar ISA temps:
Attachment:
Screen Shot 2020-03-19 at 5.58.31 PM.png


So in the Epic, 2580 lb ft of torque at 1600 rpm is 69.6% torque (2580/3707 lb ft) and a fuel flow of 56 gph or 375 pph. The photo above was around 320 ktas.

At 28,000 ft, the Starship manual recommends 73% torque and 389 pph per engine, which yields ~322 ktas at 12,000 lbs

I tried to find the closest speed between the two.

A Starship and an Epic are two very different planes, but for the sake of the guesstimate, let's assume performance will be similar from 28k to 34k feet.

Interpolating between Starship 33k and 35k altitude data yields: recommended power ~58% torque/2150 lb ft, fuel burn 314 pph or 47 gph, ~313 ktas/182 kias. Not bad!

Also: back of napkin Carson speed for an Epic is 157-171 kias (based on best glide between 120-130 kias depending on weight and multiplier of 1.316). A hypothesized 182 kias in "normal" cruise still leaves room to slow for Carson speed and lots of room to slow for max range.

Wing loading on an LT at gross weight is just under 40 lbs per sq ft. Starship is 53 lbs per sq ft. I quickly run out of talent here, but my gut suggests a slightly lower AOA from lower wing loading resulting in less drag (at the same indicated speed). Maybe there's slightly more speed in it at 34k feet? ... and more sauce on tap available with the big E1000 style inlet.

*Edited a little to clean up messy thought process


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