Fuel minimums

[Shadrach]

28 minutes ago, Danb said:

You lost me on that one Paul..

I took it as a good natured jab at the high empty weights and lowish useful loads of some of the long bodies.

[Fly Boomer]

3 hours ago, A64Pilot said:

That works for a NA engine, it’s my understanding that a turbo at altitude it’s a little more complex, but if managed correctly it will come back

If you start at FL280, and the turbocharger spools down, I would bet that "managed correctly" means gliding down to 18 or 20 to get a relight -- essentially you are normally aspirated.  What's the highest altitude you can keep your NA engine running?

[Danb]

1 hour ago, Shadrach said:

I took it as a good natured jab at the high empty weights and lowish useful loads of some of the long bodies.

Yep I own one, great two person plane.

[Z W]

3 hours ago, Fly Boomer said:

If you start at FL280, and the turbocharger spools down, I would bet that "managed correctly" means gliding down to 18 or 20 to get a relight -- essentially you are normally aspirated.  What's the highest altitude you can keep your NA engine running?

From the M20K POH:

[MikeOH]

7 minutes ago, Z W said:

From the M20K POH:

Gotta love the confidence in the procedure that Step 12 gives you

[Fly Boomer]

16 minutes ago, MikeOH said:

Gotta love the confidence in the procedure that Step 12 gives you

Covers all the bases.

[Shadrach]

3 hours ago, Fly Boomer said:

If you start at FL280, and the turbocharger spools down, I would bet that "managed correctly" means gliding down to 18 or 20 to get a relight -- essentially you are normally aspirated.  What's the highest altitude you can keep your NA engine running?

I’m pretty sure there are several NA Mooneys that have been well above 20K. @Immelman 

Perhaps there are aspects of the turbo that make a restart more challenging.

[Fly Boomer]

1 minute ago, Shadrach said:

I’m pretty sure there are several NA Mooneys that have been well above 20K. @Immelman 

Perhaps there are aspects of the turbo that make a restart more challenging.

The excerpt from the M20K POH posted above by @ZW don't sound too promising.

[Will.iam]

I have done numerous restarts when at 12,500 running a tank dry and not switching over to the other tank quick enough. Engine fires back up in seconds. Haven’t been up in the terns or flight levels and run a tank dry yet. I would be more concerned about shock cooling the engine at high altitudes sucking in sub zero air into the chamber that just moments ago was having 1300+ heat  than the engine not relighting. There was that crew that flamed out both jet engines and the cores locked due to uneven cooling. 

[Shadrach]

14 minutes ago, Fly Boomer said:

The excerpt from the M20K POH posted above by @ZW don't sound too promising.

Indeed it does not. As far as I know, none of the NA planes have such a warning in their POH

[Will.iam]

2 minutes ago, Shadrach said:

Indeed it does not. As far as I know, none of the NA planes have such a warning in their POH

Well what makes it more complicated for turbos is that mixture knob is set for turbo boosted air. You loose the plant and the turbo spools down so you also lost the air. Now that mixture you have set is way too rich. How lean do you need to go? Much easier to just cutoff the fuel and give as much air as you can with full throttle. As you slowly introduce fuel the mixture will get to a combustible mixture and start running the engine but real quickly that turbo is going to spoolup and give so much air it will lean out too much. Hince why reducing throttle immediately after engine starts running.  

[Shadrach]

19 minutes ago, Will.iam said:

Well what makes it more complicated for turbos is that mixture knob is set for turbo boosted air. You loose the plant and the turbo spools down so you also lost the air. Now that mixture you have set is way too rich. How lean do you need to go? Much easier to just cutoff the fuel and give as much air as you can with full throttle. As you slowly introduce fuel the mixture will get to a combustible mixture and start running the engine but real quickly that turbo is going to spoolup and give so much air it will lean out too much. Hince why reducing throttle immediately after engine starts running.  

I would think the servo would compensate for the reduced manifold pressure.

[hais]

On 2/18/2024 at 5:03 PM, EarthboundMisfit said:

Remain calm

Any practical tips on how to accomplish that?

[Shadrach]

10 hours ago, Will.iam said:

Well what makes it more complicated for turbos is that mixture knob is set for turbo boosted air. You loose the plant and the turbo spools down so you also lost the air. Now that mixture you have set is way too rich. How lean do you need to go? Much easier to just cutoff the fuel and give as much air as you can with full throttle. As you slowly introduce fuel the mixture will get to a combustible mixture and start running the engine but real quickly that turbo is going to spoolup and give so much air it will lean out too much. Hince why reducing throttle immediately after engine starts running.  

I’m not a turbo operator (at least not in the air). My assumption was the that the fuel servo would adjust for changes in MP and hold roughly the same air fue ratio based on the mass of the airflow entering the servo. That’s certainly how the RSA system on Lycomings work. They won’t hold an exact F/A mixture across a broad range of airflow, but I cat imagine it being so far off as to not support combustion 

[N201MKTurbo]

NORMALLY ASPIRATED ENGINES HAVE A FUEL PUMP EQUIPPED WITH A JET PLUG IN THE OUTPUT SECTION OF THE PUMP, WHICH BLEEDS OFF FUEL PRESSURE AS IT REACHES ITS MAXIMUM SYSTEM OUTPUT. NORMALLY, NON-TURBOCHARGED 360 ENGINES HAVE NOZZLE PRESSURES (OR MAXIMUM FUEL-PUMP PRESSURES) OF 12 -18 PSI. TURNING THE JET PLUG IN WILL INCREASE THE HIGH-END PRESSURE, WHILE TURNING IT OUT WILL REDUCE THE PRESSURE TO THE MANIFOLD VALVE.

FUEL PUMPS INSTALLED ON TURBOCHARGED ENGINES ALSO REGULATE FUEL-PRESSURE OUTPUT, BUT DO SO BY USING AN ANEROID-ACTIVATED ORIFICE, WHICH RESPONDS TO TURBOCHARGER BOOST (OR DECK) PRESSURE. THE MORE BOOST APPLIED TO THE ANEROID, THE MORE MOVEMENT ALLOWED ON THE ORIFICE. IN THIS WAY, FUEL PRESSURE WILL INCREASE WITH BOOST PRESSURE RATHER THAN REACTING TO JUST ENGINE RPM.

THE ANEROID DOES NOT SENSE ALTITUDE CHANGE OR ATMOSPHERIC PRESSURE. IT SIMPLY PROVIDES A BALANCE BETWEEN SEALED ANEROID PRESSURE AND TURBOCHARGER OUTPUT. 

[Fly Boomer]

1 hour ago, N201MKTurbo said:

FUEL PUMPS INSTALLED ON TURBOCHARGED ENGINES ALSO REGULATE FUEL-PRESSURE OUTPUT

So, regulating fuel pressure means you don't need to worry about the red knob?

[N201MKTurbo]

34 minutes ago, Fly Boomer said:

So, regulating fuel pressure means you don't need to worry about the red knob?

Not necessarily. The point I was making with this post (which is from AvWeb) is that if the turbo wasn't making pressure, it would automatically reduce the fuel flow. So the contention that if you had to restart your turbo engine at high altitude, it would be too rich, isn't true.

With my turbo system, If I set cruise mixture, I can descend from the flight levels to the airport without adjusting the mixture and the FF and TIT will stay the same all the way down. Well actually, the TIT will drop a little. But My turbo system is a bit of a unicorn. there were only 35 of them made and I think some have been taken out of service.

[Shadrach]

55 minutes ago, Fly Boomer said:

So, regulating fuel pressure means you don't need to worry about the red knob?

No. It means that wherever the red knob is set, the servo will attempt to, more or less, maintain the the set F/A ratio.
As an example if you’re at 18,000 feet set at 16.5gph and 26”, and the turbo plumbing fails rendering the engine without boost, the fuel system is not going to continue flowing at 16.5. It will reduce fuel flow based on the now much lower metered airflow.

[Shadrach]

2 hours ago, N201MKTurbo said:

NORMALLY ASPIRATED ENGINES HAVE A FUEL PUMP EQUIPPED WITH A JET PLUG IN THE OUTPUT SECTION OF THE PUMP, WHICH BLEEDS OFF FUEL PRESSURE AS IT REACHES ITS MAXIMUM SYSTEM OUTPUT. NORMALLY, NON-TURBOCHARGED 360 ENGINES HAVE NOZZLE PRESSURES (OR MAXIMUM FUEL-PUMP PRESSURES) OF 12 -18 PSI. TURNING THE JET PLUG IN WILL INCREASE THE HIGH-END PRESSURE, WHILE TURNING IT OUT WILL REDUCE THE PRESSURE TO THE MANIFOLD VALVE.

FUEL PUMPS INSTALLED ON TURBOCHARGED ENGINES ALSO REGULATE FUEL-PRESSURE OUTPUT, BUT DO SO BY USING AN ANEROID-ACTIVATED ORIFICE, WHICH RESPONDS TO TURBOCHARGER BOOST (OR DECK) PRESSURE. THE MORE BOOST APPLIED TO THE ANEROID, THE MORE MOVEMENT ALLOWED ON THE ORIFICE. IN THIS WAY, FUEL PRESSURE WILL INCREASE WITH BOOST PRESSURE RATHER THAN REACTING TO JUST ENGINE RPM.

THE ANEROID DOES NOT SENSE ALTITUDE CHANGE OR ATMOSPHERIC PRESSURE. IT SIMPLY PROVIDES A BALANCE BETWEEN SEALED ANEROID PRESSURE AND TURBOCHARGER OUTPUT. 

No need to yell…

[N201MKTurbo]

32 minutes ago, Shadrach said:

No need to yell…

It is a cut and paste from AbWeb. They were yelling. I'm too lazy to fix it all. 

[N201MKTurbo]

37 minutes ago, Shadrach said:

No. It means that wherever the red knob is set, the servo will attempt to, more or less, maintain the the set F/A ratio.
As an example if you’re at 18,000 feet set at 16.5gph and 26”, and the turbo plumbing fails rendering the engine without boost, the fuel system is not going to continue flowing at 16.5. It will reduce fuel flow based on the now much lower metered airflow.

It will reduce it because of reduced upper deck pressure. It doesn't meter airflow except by throttle position. If the turbo quits, the throttle position will not change.

[Shadrach]

1 minute ago, N201MKTurbo said:

It will reduce it because of reduced upper deck pressure. It doesn't meter airflow except by throttle position. If the turbo quits, the throttle position will not change.

Right,  practically speaking is upper deck pressure not a proxy for airflow?

[N201MKTurbo]

9 minutes ago, Shadrach said:

Right,  practically speaking is upper deck pressure not a proxy for airflow?

If you have a Merlyn it doesn't. If you have a stock 231 the upper deck pressure will follow the throttle.

[slowflyin]

I run Cies senders and JPI FF so I have a pretty good idea how much fuel is onboard.  My rule is to land with no less than 45 minutes.  I plan for an hour with 45 minutes being a minimum.  I'm not concerned about low fuel levels in coordinated flight, but crosswinds can be challenging with a surging engine.  Almost had a C120 eat my lunch years ago when she started sucking air in a strong crosswind landing.    If I calculate landing with less than 14 gallons I check the winds at my destination and run the downwind tank to almost empty.  Here's a picture from yesterday's flight.  Note the totalizers reads 14.9 but the gauges total 23.  In level flight the gauges totaled 15 (1 on the left and 14 on the right).  The wing site gauges totaled 15 after landing as well.  My Bravo's fuel gauges are only accurate in flight and the wing mounted site gauges are only accurate on the ground.  

[Pinecone]

7 hours ago, slowflyin said:

I run Cies senders and JPI FF so I have a pretty good idea how much fuel is onboard.  My rule is to land with no less than 45 minutes.  I plan for an hour with 45 minutes being a minimum.  I'm not concerned about low fuel levels in coordinated flight, but crosswinds can be challenging with a surging engine.  Almost had a C120 eat my lunch years ago when she started sucking air in a strong crosswind landing.    If I calculate landing with less than 14 gallons I check the winds at my destination and run the downwind tank to almost empty.  Here's a picture from yesterday's flight.  Note the totalizers reads 14.9 but the gauges total 23.  In level flight the gauges totaled 15 (1 on the left and 14 on the right).  The wing site gauges totaled 15 after landing as well.  My Bravo's fuel gauges are only accurate in flight and the wing mounted site gauges are only accurate on the ground.  

How much fuel did each tank take?

I would be concerned that the fuel gauge was saying 23 gallons, but the totalizer and sight gauges said 15.