Switch Tanks, Switch Tanks, Switch Tanks!

[carusoam]

There is an adjustment for that...  

write it on the list for your next annual...

Consider getting those funky blue, last forever, o-rings at the same time...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Hank]

1 hour ago, steingar said:

My M20c has brand newgas caps thanks to a Mooneyspace denizen. They are the stiffest caps I’ve ever seen. To get them open I have to pry with a screwdriver (wrapped in a towel). And I still check the tanks before every flight.

If you aren't ready to adjust them (may as well replace the orings when doing that, since it will require replacing the little cotter pin in the castle nut when you adjust the tension and when you disassemble to replace the small inner oring), gently pry the tab up and give a small squirt of TriFlow along the center shaft, then fold the tab down and up a few times. Then next annual, replace both orings in each cap anyway.

[N201MKTurbo]

10 hours ago, steingar said:

My M20c has brand newgas caps thanks to a Mooneyspace denizen. They are the stiffest caps I’ve ever seen. To get them open I have to pry with a screwdriver (wrapped in a towel). And I still check the tanks before every flight.

Lube your fuel caps!

[1964-M20E]

If I find mine getting stiff when I check the oil I let a drop of oi form the dip stick hit the center shaft of the cap.  Works like a charm every time and lasts about a year or more.

 

 

[steingar]

Thanks for the thoughts gentlemen, I shall certainly put your suggestions into action.  My point was despite the relative (and I hope temporary) difficulty in removing my fuel caps, I still check the fuel before every flight.  So should you.  No one should ever run out of gas in a Mooney.

[MoonFlyer68]

I am about to revive this old thread.  Using the "Search" function, this was the best thread I could find that applied to my question.  I have a 1968 M20F.  There is no official In Flight Restart procedure in the POH.  Looking at a later year F model the POH does have a specific checklist for In Flight Restart.  I understand that if an engine is starting to stumble because of fuel starvation your very first priority needs to be restoring fuel to the engine.  Hence, switch tanks is 100% the thing to start with.

So here is where I have a question.  If the engine has actually quit then is switching tanks still step one?  My question is based on the caution that is in the POH for the M20F:

CAUTION:  Do not allow the engine to lose power or quit before switching fuel tanks.  If a tank runs dry and the engine quits, retard the throttle before restarting.  Restarting with an advanced throttle may cause engine overspeeding that can lead to mechanical malfunction.

Based on that caution, it is my assumption that retarding the throttle should be step one if the engine has quit in flight before switching tanks.  Am I reading this wrong?  Do I want my engine to restart with WOT and possibly cause even worse problems?  Appreciate your thoughts on the subject.

[carusoam]

Engine stumble is not a restart... 

Take a look, one step at a time of what occurs....

The most modern POH for your plane/engine will outline the steps required to restart the specific engine...

 

1) restarting will occur naturally because the engine is turning, driven by the prop... air is flowing, spark is occurring...

2) when the new gas arrives the engine starts developing power immediately...

3) Realistically, How Long was the engine not producing power?  Parts of a second, or was the pilot asleep at the switch?

4) it is possible that there may be some air in the fuel lines...

5) using the electric fuel pump will help stabilize the fuel flow during tank switching...

 

6) Things can be different if a turbo has spun down.... the restart may even require descending to a critical altitude...

7) being nice to the engine and exhaust system can also be considered....

8) the mixture knob can be used to gently introduce fuel back into the engine... MP adjusted to limit power... introducing changes.?.?

9) realistically, switching tanks is usually a planned event... burble, switch... done!   Add fuel pump because it is the right thing to do..

10) use caution if a restart doesn't occur immediately... if fuel is flowing and the restart has not occurred... fuel will be going into the exhaust...

11) The governor will be changing blade angle to maintain rpm...  so upon restart and return of power, the mechanical rpm control can be forced to do odd things....

12) what altitude are you at? How much MP is available?

13) Do you have minutes to figure this out, or are you on short final, and need power now!?!?

14) You can practice most of the procedure without needing to run a tank dry...

15) You can practice the procedure by turning the fuel off, if desired... (have safety in mind if going this route...)

PP thoughts only, read the POH for the proper process for the engine....

Emergency restarts take on a whole new level of problem solving while attempting restarting the engine...

Best regards,

-a-

[Gagarin]

On 6/17/2018 at 11:06 AM, DAVIDWH said:

A few years ago there was an FAA accident report of a pilot running a tank dry then switching tanks. Engine never restarted and pilot was killed.

FAA  findings were blocked injectors due to bottom tank debris sucked in from dry tank. 

Personally,  I stopped doing it after reading this report.

There is floating debris that never get drained and can be ingested by the fuel pick up at low fuel levels. To avoid this at every annual remove the fuel tank drain valves and empty the tanks completely. 

[gsxrpilot]

I'm a huge proponent of running tanks dry at altitude. This means I've been in this situation more than a few times. As @carusoam says, unless you fell asleep, the engine won't come to a stop. And even then, it won't likely stop but rather keep windmilling.

My procedure has always been, Step 1 - Switch tanks. And there really is no step 2. I used to fly an M20C with the carb and this procedure worked every time without fail. I never used the boost pump, never retarded the throttle or mixture. Just switch tanks as soon as you notice the engine start to stumble and fuel flow drops off. The engine restarts and the whole event takes 2 seconds.

Now flying the 252, the procedure gets modified just a bit when in the flight levels. I'll first switch tanks and then hit the high boost pump. It can take some time (10 sec or so) for the engine to restart above FL200. Down lower, where there is breathable O2, the engine restart is exactly the same as the M20C. Just switch tanks, done.

The bottom line for me is, whether planned or unplanned, I want the tank switching to be muscle memory and the default reaction. If I have an engine issue, immediately switch tanks and then proceed with other troubleshooting if needed.

 

[MoonFlyer68]

I agree with both of you that if we are talking about an engine stumble that is about to quit because of fuel then of course switch tanks and get the fuel flowing again.  The engine then "should" spring back to full song.  I have also considered doing this up at altitude to get a feel for the event itself and get a better gauge of how accurate my fuel gauges are.  My only hang up is IF the engine has actually quit.  I know there are probably any number of variables that could be taken into consideration if this event ever happens.  My only thought was by reading the POH the caution that if the engine actually quits, you should retard the throttle before starting to help prevent damage to the engine.  I know the general answer is to "Check your POH" so if my engine has quit the POH tells me to retard the throttle first.  From what I am hearing, it seems that most people just switch tanks and call it good no matter what the throttle is set at.  Of course if that doesn't solve your problem, then you have to start trying other things.

A buddy of mine and I both are fairly new owners the same model Mooney and so we had this discussion and thought we would find out what the "tribal Knowledge" had to say.  Thanks for the input.

[MoonFlyer68]

By the way, what may also be of interest is that I am a retired Army Pilot and in the Military they really harp on making sure you know and understand all Warnings, Cautions, and notes.  This being a Caution, really gets my attention.

[Ibra]

If on first RPM blip one go and switch fuel tanks then I think it is no different from water or dirt in fuel? So it it just depends on how quickly one do it 

I think if aircraft speed and propeller have slowed down a lot, then you may have to go back to air restart as per POH or common wisdom

This typically involve slowing down to near stall speeds and back on throttle at idle or 1/2 way, and switch some electrics ON/OFF

On motor-gliders engine will only stop when prop is windmilling at less than some RPM value, 1000RPM above that just restart itself on mags+fuel 

One has to slow down the aircraft near stall to be able to cut the engine and be able to feather the prop

I think there is a relationship between IAS, RPM to get easy air restart without touching anything else other than mags+fuel and not breaking the engine?

Edited March 10, 2020 by Ibra

[Hank]

I've had three "stoppages" in my C.

1. Once at 9500 doing a magneto test, proving that the left one was dead. Plane pitched down immediately to maintain cruise speed when I turned the switch to "L" and restarted as soon as it clicked back to "Both." Ran well after clicking over to "R."
2. My fuel stop had pump problems that the mechanic and FBO operator couldn't fix, so i took off with less than full tanks. Watched like a hawk, kept extending "five more minutes" until it didn't make it and cut out with no burble, then switched tanks and restarted immediately with no issues, no surging. Landed with 1:15 fuel all in one tank.
3. Distracted by looking at my intended destination [reported as closed during preflight briefing] as i went over descending for the next county, I forgot to change tanks. So they reminded me with a burble, but all instruments looked good. The second burble was more intense, and longer, and my scan caught the clock and the position of the red hands. Clicked the fuel to the other tank and it immediately smoothed out.

[carusoam]

@gsxrpilot,

Have you run Into Any challenges regarding the turbo spinning down over time?

It will alter the air flow into the engine, then the power, then the rate the turbo is spinning... making the restart a level more challenging than an NA engine?

If the turbo stops... do you have a POH documented altitude that you may need to get down to before the thermodynamics works again...?

 

The additional challenges of flying in the FLs... 

Best regards,

-a-

[gsxrpilot]

1 hour ago, carusoam said:

@gsxrpilot,

Have you run Into Any challenges regarding the turbo spinning down over time?

It will alter the air flow into the engine, then the power, then the rate the turbo is spinning... making the restart a level more challenging than an NA engine?

If the turbo stops... do you have a POH documented altitude that you may need to get down to before the thermodynamics works again...?

Nope, never. But then I've never let it go more than a couple of seconds before switching tanks. 

And this is one of the reasons for running this procedure, or practicing if you will. I know exactly what it's like when the tank first starts to run dry. In the event I'm not expecting it, switching tanks will be muscle memory and I'll not spend even 15 seconds wondering what's happening. But rather I'll immediately switch tanks without allowing the turbo to spool down.

[Ibra]

1 hour ago, carusoam said:

It will alter the air flow into the engine, then the power, then the rate the turbo is spinning... making the restart a level more challenging than an NA engine?If the turbo stops... do you have a POH documented altitude that you may need to get down to before the thermodynamics works again...?

For Turbos, I guess if turbo fails you are back to NA territory, with extra hassle of having to match to some minimum turbo power to be able to restart without the help of starter or turbo compressions, something like altitude where the MP no-turbo matches 50% of the MP with-turbo?  

The POH documented altitude for restart is highly applicable for turbofans, when the compressor stops/stalls or the fire is dead in the combustion chamber, CFM56 has certified ceiling in 45kft, however, to restart the engine one has to be in the "engine relight envelope" which is about 25-30kft altitude, 250-300kts IAS, engine fan speed (N1) for restart procedure, at 10kft & 300IAS, you will get 50% (N1) and it will magically restart (irrespective of procedure) as long as APU and fuel are ON...

 

Edited March 10, 2020 by Ibra

[gsxrpilot]

My POH says...

At altitudes above 18,000, it may be necessary to slowly lean mixture from full rich position to facilitate engine restart. If engine still shows no indication of restarting then High Fuel Boost Pump - ON.

[MoonFlyer68]

Let me make sure I am understanding some of these replies. If the engine has actually quit running running but the propeller is still spinning at a decent RPM, then starting with advanced throttle should be ok.  It is only if the engine is not running and the prop is stopped or at a very low RPM that I should be worried about retarding the throttle first.  Does that sound about right then? 

Would have been very nice if Mooney made that a little bit clearer when they wrote that caution about in flight restarts.  This is why we come to Mooneyspace, to get the rest of the story.

[Davidv]

2 hours ago, Ibra said:

For Turbos, I guess if turbo fails you are back to NA territory, with extra hassle of having to match to some minimum turbo power to be able to restart without the help of starter or turbo compressions, something like altitude where the MP no-turbo matches 50% of the MP with-turbo?  

The POH documented altitude for restart is highly applicable for turbofans, when the compressor stops/stalls or the fire is dead in the combustion chamber, CFM56 has certified ceiling in 45kft, however, to restart the engine one has to be in the "engine relight envelope" which is about 25-30kft altitude, 250-300kts IAS, engine fan speed (N1) for restart procedure, at 10kft & 300IAS, you will get 50% (N1) and it will magically restart (irrespective of procedure) as long as APU and fuel are ON...

 

I may be a little ignorant in this area, but I don't believe there are a lot of cases where a turbo fails in mid flight and you don't have other big problems on your hands.  It doesn't seem like it would just wind down without some sort of exhaust or V band clamp failure ect... which would basically result in a blow torch in my engine compartment near fuel lines, oil, and other components.  This just means it's get on the ground ASAP rather than just losing the turbo and operating like a NA engine.

I'd be curious if there are other items that could fail which would make for a "graceful" situation where you didn't have some major (fire) problems on your hands.

[aviatoreb]

18 minutes ago, Davidv said:

I may be a little ignorant in this area, but I don't believe there are a lot of cases where a turbo fails in mid flight and you don't have other big problems on your hands.  It doesn't seem like it would just wind down without some sort of exhaust or V band clamp failure ect... which would basically result in a blow torch in my engine compartment near fuel lines, oil, and other components.  This just means it's get on the ground ASAP rather than just losing the turbo and operating like a NA engine.

I'd be curious if there are other items that could fail which would make for a "graceful" situation where you didn't have some major (fire) problems on your hands.

I had a turbo failure 2 years ago that caused a complete engine stoppage at 16,500 ft.  As turns out - learned later - the turbo had seized.  But before it seized it went through a couple of minutes of burning oil, a lot of oil, most of the oil, that caused a lot of smoke in the cockpit as well.  The smoke breached into he cockpit just as the turbo seized and so then engine stopped.  So I thought I had an engine out AND a likely fire and I did what I could with the emergency accordingly.  I failed to starve the engine fuel flow - which I should have done if I had been correct that there was a fire.  That was the one major mistake I made, but I was lucky as it was not of consequence that day.  So with normal fuel flow, yes my engine came back to life on its own from windmilling at around 8000ft.  By then I had a runway made and I was still fearing a fire so I then starved the engine and continued with the dead stick landing, which turned out fine,  I worked the problem as it seemed with the evidence I had at hand as I understood it and in a hyper alert but definitely stressed situation.  Other than the one big mistake with the fuel flow that again I was lucky turned out not to be relevant, I did everything else in a way that looking back I am still happy enough with how I handled it.  And anyway, a nice smooth runway landing is a good way to end a bad day.  Shaking hands and smiling with firemen.  And taking a phone call with the fellow on ATC who called me to see how my declared emergency ended.

So my experience - loosing the turbo isn't necessarily all is fine you can just proceed NA from there.  Its a serious emergency.  Some failure modes would include torching hot gases inside the forward firewall and maybe starting a fire.

Edited March 11, 2020 by aviatoreb

[LANCECASPER]

14 minutes ago, Davidv said:

I may be a little ignorant in this area, but I don't believe there are a lot of cases where a turbo fails in mid flight and you don't have other big problems on your hands.  It doesn't seem like it would just wind down without some sort of exhaust or V band clamp failure ect... which would basically result in a blow torch in my engine compartment near fuel lines, oil, and other components.  This just means it's get on the ground ASAP rather than just losing the turbo and operating like a NA engine.

I'd be curious if there are other items that could fail which would make for a "graceful" situation where you didn't have some major (fire) problems on your hands.

The turbo can fail in flight without an exhaust failure, but when it does above 12,000 ft you get an overly rich mixture which  causes a rough running engine or a complete loss of power - definitely not continue on to destination.

 

[carusoam]

This is a great conversation to have...

TC operations weren’t taught at the flight school I went to... they got a small mention...

0) lots of oil is used to cool and lubricate the bearings...  bad temp control or blocked passageways can lead to coked oil in the bearing... followed by restricted oil passageways, lower flow, and more coking... not enough oil...leads to bearing failure... the turbo stops spinning... a catastrophic failure is not common... but a bound up turbo isn’t very good...

1) Some of the challenges come from it not being an ordinary NA engine because the CR ratio is so low... unless you are flying a TN’d bird...  even then, some have a lower CR than their NA counterparts... 

2) Anything that allows exhaust to leak before the TC is bad... from bad V-bands to thinned, eroded, tube walls... cutting torch effect.

3) Anything that allows the oil to escape... the oil fed to the TC is a high volume of coolant... if the turbo’s seals let go... the amount oil allowed to escape may get large... a smoke show will be going on behind you if that were to happen...

4) Unfortunately, there isn’t a lot of instrumentation to allow you to know what isn’t working properly...

5) high oilT and an OilP reading that may be bouncing.... may give a hint that oil has run very low...

6) can you here the TC spinning while flying in the FLs?  That would be a hint if it weren’t spinning...

7) boost controllers have a way to be disappointing as well.   From their harsh environmental exposure... if you are familiar with mouse milk, the lubricant... you are probably familiar with the maintenance... 

PP thoughts only, not a TC’d pilot...

Best regards,

-a-

[carusoam]

1 hour ago, MilitaryAV8R said:

Let me make sure I am understanding some of these replies. If the engine has actually quit running running but the propeller is still spinning at a decent RPM, then starting with advanced throttle should be ok.  It is only if the engine is not running and the prop is stopped or at a very low RPM that I should be worried about retarding the throttle first.  Does that sound about right then? 

Would have been very nice if Mooney made that a little bit clearer when they wrote that caution about in flight restarts.  This is why we come to Mooneyspace, to get the rest of the story.

The prop keeps spinning at whatever rpm you have set... it is kept there by oil pressure from the governor's gear pump...

Engine powered or not... the prop keeps spinning...  even when you want it to stop... you have to go so slowly... to make that happen... it won’t be accidental...

The cool part...

1) no starter needed...

2) no hot start procedure needed...

3) just deliver the fuel in an ordinary way...

4) adding the electric fuel pump will take care of any anomalies like air bubbles that have entered into the fuel system when the tank ran dry... even then... air bubbles just run through the system... and come out the other side...

5) no need to advance the throttle... wherever it was when last producing power should work perfectly...

6) Overall this is non-event unless you fell asleep at the fuel switch... and it is still pretty much a non-event...

7) Without power... the plane will be slowing, or descending... when power comes back on the slowing stops or the descending stops... as pilot you control the yoke...

8) In the event the engine doesn’t re-start... that would be a different problem... be ready with the problem solving tree of throttle position and mixture position and key position... as usual for engine out...

9) did you ever pop the clutch to start a car with a dead starter...?  in this case, there is no clutch... the engine will rotate until the plane stops moving... or the pilot goes out of the way to make it stop...

10) POHs are written in standard legal English using as few words as possible...

This is what makes Transition Training so valuable... a pilots first days in a plane are probably the most dangerous... just learning all the detail... properly...

PP thoughts only, not a CFI... or mechanic...

Best regards,

-a-

[Ibra]

9 hours ago, Davidv said:

I'd be curious if there are other items that could fail which would make for a "graceful" situation where you didn't have some major (fire) problems on your hands

I was more referring to the conditions for turbo air-restart after turbo has slowed down in high altitudes, it seems you need to go down to a low altitude where you can match Fuel Flow/Manifold Pressure of a NA engine before being able to air-restart, if turbo fails completely (or even malfunction) I guess it is not a day to go to destination 

My guess turbo failure is worse than a propeller governor failure (engine can be run on low power for landing ASAP but also may hide or cause load of other engine issues), as you mentioned the failed turbo has an extra huge potential risk of fire from hot gas and rich fuel, so one is probably better off landing ASAP even off-field engine off than trying to sustain level flight on low MP settings to a nearby airfield, the thing I am not sure about if running on low power with poor mixture settings does save the day? POH suggests poor mixture for turbo malfunction (well only to restart from complete power loss, but it is not that prescriptive on mixture for valve malfunctions), although POH is crystal clear: shutting down the engine is the required action when something like turbo exhaust breaks inside the engine bloc 

Edited March 11, 2020 by Ibra

[cbarry]

After reading about everyone’s techniques, I must be one of the most conservative pilots on the planet.  I’ve always just noted that for most flights, roughly 95% are taken solo (and this stat holds true for many pilots).  Thus, W&B is not really an issue.  So, what, require for flight, variable can I affect the most to give myself the greatest odds of being able to use my options—fuel.  Outside of remembering the old saying “the only time you can have too much fuel is when you’re on fire,” I fly on the top half of the tanks (another old saying) and manage fuel based on time and flow.  If a person wants to experience what it feels like to starve an engine in flight, just turn the valve to the off position.  A tank doesn’t need to be dry to still learn how to respond to an otherwise startling moment.