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28 Mar 2024, 11:33 [ UTC - 5; DST ]


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 21 Mar 2023, 19:03 
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Username Protected wrote:
You have all Garmin? They should stay alive during a start.

Yep! Dual G600 and Dual GTN750. That's great to hear. I really need to try this but I'm always headed somewhere and don't want a delay in case it does puke. My battery often drops to 12-14V during a start but now that you got me thinking about it, the Garmin's run in 12V piston aircraft so it should be fine...... :scratch:


I power my 750xi on after the first engine start. Same with my 340.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 21 Mar 2023, 23:22 
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Username Protected wrote:
They should stay alive during a start.

I wondered about doing the same to save fuel on the ground. Start one engine, taxi to runway, and then start the other when close to takeoff time.

Would save TR deployments, brakes, fuel, etc.

Ground idle fuel flow is about 200 pph per side, so a 15 minutes is 50 lbs of fuel.

Mike C.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 05:47 
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I don’t think they drop out until something below 11v. Even short transient below that they work. Since the system is primary for engine indications in other aircraft it’s necessary.

Ground idle would be nice on the earlier aircraft.


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 06:05 
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Aircraft: AA1B,PA28,PA18,CE500
Username Protected wrote:
They should stay alive during a start.

I wondered about doing the same to save fuel on the ground. Start one engine, taxi to runway, and then start the other when close to takeoff time.

Would save TR deployments, brakes, fuel, etc.

Ground idle fuel flow is about 200 pph per side, so a 15 minutes is 50 lbs of fuel.

Mike C.


Brakes you will save a little. Since the speed is low brake wear during taxi is low. From over a decade of experience using TR during taxi might not be he best idea. NetJets found the right engines in their Xs weren’t in as good shape at HSI. Reason was a lot of pilots would taxi with that one out because of its high residual thrust. That thing would get cruising along at idle thrust when light like the 500series. How much the difference was I don’t know. And they were flying 1000+ hrs/yr. Have you recoded block to departure time? 15mins is a very long time if that’s an average. 5-6 is most common. Unless you are departing TEB and in a 2hr conga line when the TMU is running SWAP taxi on 1 engine will be more of a pain than it’s worth. I’d just power everything up on a GPU, program it start and go.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 08:59 
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NetJets found the right engines in their Xs weren’t in as good shape at HSI.

Interesting.

On the small cabin Citations, the right engine is the "APU" engine, you can start it and run systems from it. For example, GND mode on the bleed air was extra air from the right engine for ground ops. The right was preferred due to that and being on the other side of the passenger door.

The Citation X with an actual APU shouldn't have a preference due to that. The engines on the X are so large that they may be picking up FOD when TRs are out. My engines are much smaller and blanked by the wings more effectively than a X, so I doubt that is happening to me.

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Have you recoded block to departure time? 15mins is a very long time if that’s an average.

It isn't, but 15 min at a busy airport can occur, say number 5 for the runway at KSRQ, which has happened to me.

I have not done the "start only one" technique as of yet, just wondering if it would be helpful.

Mike C.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 09:55 
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Username Protected wrote:
I don’t think they drop out until something below 11v. Even short transient below that they work. Since the system is primary for engine indications in other aircraft it’s necessary.

Ground idle would be nice on the earlier aircraft.


The GDUs are rated down to 9V, the GTNs to 11


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 10:19 
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Joined: 11/06/20
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Location: Tulsa, OK - KRVS
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Username Protected wrote:
I don’t think they drop out until something below 11v. Even short transient below that they work. Since the system is primary for engine indications in other aircraft it’s necessary.

Ground idle would be nice on the earlier aircraft.


The GDUs are rated down to 9V, the GTNs to 11

Thank you Terry!

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 17:13 
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Back in the Falcon 20 and Sabreliner days we almost always taxied out on one engine. I have done it some in the Citation but only when we were expecting a delay. We always turned off the avionics for the second engine start except on the Falcon when we had the APU running. I forgot one day in the Sabreliner and blew the radar on a PBI-DAL leg. Luckly the thunderstorm line was around NEW and by then we were at FL450 and could visually work our way around them.


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 22 Mar 2023, 20:10 
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Username Protected wrote:
NetJets found the right engines in their Xs weren’t in as good shape at HSI.

Interesting.

On the small cabin Citations, the right engine is the "APU" engine, you can start it and run systems from it. For example, GND mode on the bleed air was extra air from the right engine for ground ops. The right was preferred due to that and being on the other side of the passenger door.

The Citation X with an actual APU shouldn't have a preference due to that. The engines on the X are so large that they may be picking up FOD when TRs are out. My engines are much smaller and blanked by the wings more effectively than a X, so I doubt that is happening to me.

Mike C.


I wasn’t implying it was from using the engine as an APU. Every plane that I have flown puts out way more cabin air from the APU compared to both engines at idle. It was from taxi. The X engine inlet is in front of the wing TE and way higher than yours. Along with the inlet being much farther distance wise from the back. Longer engine. It could be some for, but that would likely also show in the fan. Either way it could be an issue or maybe not. Just 1 small data point.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 23 Mar 2023, 00:28 
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Username Protected wrote:
I wasn’t implying it was from using the engine as an APU. Every plane that I have flown puts out way more cabin air from the APU compared to both engines at idle.

My plane has a "GND" mode which triples the bleed air flow from the right engine. It exists to get more air flow on the ground so that you can run the right engine kind of like an APU to help cool the cabin. Thus you get in flight like bleed air flow while on the ground, or at least closer to that.

You go back to "NORM" (both) when getting ready for takeoff. If you forget to do that (despite a caution light also indicating you are in GND mode), it automatically switches out of GND mode at high power.

Mike C.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 11 Apr 2023, 18:20 
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Location: Tulsa, OK - KRVS
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To follow up on my post(s) about Garmin staying alive during an engine start...

I tried it last week and IT WORKED! I was sitting on the ramp and fired up one engine. Turned on my inverters and avionics and did all of my checks, got my clearance, etc. Then I fired up the second one before calling for taxi.

On the return it was an uncontrolled field so I fired up one engine, taxied to the run-up area, called for my clearance, then fired up the second one and departed.

The only wrinkle was with the second scenario, my time from avionics on to taxi didn't give enough time for GPS #1 to align. It was grumping at me all the way to the end of the runway. The messages went away while I was getting my clearance but then reappeared as I was rolling down the runway. I thought I might get to do Mike C's GPS denied test for real! Would have been fine, Tulsa has a VOR and I could have just followed that in. I also could have switched to GPS #2 as primary as the copilot G600 wasn't showing the no gps signal message. But it figured itself out while I was still being vectored by Kansas City approach.

Anyway, this will be my new procedure to save a bit of fuel - especially at places with long taxis like IAH.

Thank you Todd and Terry for giving me the confidence to try it!


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 11 Apr 2023, 20:36 
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Company: Naples Jet Center
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Username Protected wrote:
I don’t think they drop out until something below 11v. Even short transient below that they work. Since the system is primary for engine indications in other aircraft it’s necessary.

Ground idle would be nice on the earlier aircraft.


The GDUs are rated down to 9V, the GTNs to 11


So what happens when it goes lower than 9 or 11 V? I was raised not to taxi before the flags pulled, etc, but I don’t understand how a G600 is powered on the battery bus vs any risk with the avionics bus on when starting?

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 11 Apr 2023, 23:43 
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Username Protected wrote:
So what happens when it goes lower than 9 or 11 V?

Modern computer controlled stuff has undervolt monitors. If the voltage sags below a threshold, the system will reset, power down, or otherwise enter some safe mode until power comes back. If a device is rated for 9 volts, the undervolt will be noticeably lower than that, probably around 7 volts or so, to allow for headroom.

The other aspect is that the computer parts, which usually run on 3.3 volts or less, may not reset on undervolt until the input gets down to maybe 5 volts. The 9 volt rating may mean the system no longer meets spec (for example, transmit power is reduced) but it might not reset below that for a while. In other words, the dip from 9 volts to 5 volts may only result in a momentary loss of meeting spec and not a system reset.

I would be astounded if Garmin hasn't designed the power supply inside these boxes to be quite robust and tolerant to the input voltage doing just about anything.

Another aspect about leaving one engine off in a legacy Citation is that the Citation supports cross generator starts. So when you do go to start the second engine, you have both the battery and the operating engine generator providing power. This makes the voltage dip a lot less and the start a lot quicker.

Mike C.

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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 12 Apr 2023, 09:21 
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Is it just the Pratt 617s that require a 3 minute idle prior to advancing the throttles if oil temps are under 14c on start?

Chip-


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 Post subject: Re: New CE-500 owner joined the club
PostPosted: 12 Apr 2023, 09:42 
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Username Protected wrote:
Is it just the Pratt 617s that require a 3 minute idle prior to advancing the throttles if oil temps are under 14c on start?

My AFM says oil temperature limits for takeoff are +10 to +121 C for JT15D-5A.

Although not stated anywhere explicitly, this implies you should wait for takeoff until you get +10C oil temperature.

I've never really checked that before takeoff, but I haven't operated in really cold temps yet.

My engines use Mobil Jet 254 oil, which claims operating range of -40 to +232 C operating range.

Mike C.

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