If dual alternators are installed, say, in a 231 or 252, must they both be working to legally fly? Hypothetical question, of course.

[EricJ]

10 hours ago, Will.iam said:

I don’t have a fuel pressure gauge nor was one ever installed in my 252 from the factory but yet it’s vfr and ifr certified. It calls into question why then does your require one fir vfr flying? Makes no sense to me. 

Do you have a fuel flow gauge?   Usually that's what substitutes for FP, since the fuel flow gauge is usually actually a fuel pressure gauge.

 

[carusoam]

The pilot wants to know fuel can flow...  VFR, IFR, day, and night...

That is accomplished by either FP, or FF... data.

If fuel stops flowing... having this piece of data will help with the normal problem solving...

Hey look ma... no FF!  
Turn on the fuel pump...

Of course... there can be some unusual loss of fuel flow... such as a big leak before the fuel pump....

It always helps to know where the fuel is going, if anywhere...

PP thoughts only, not a mechanic...

-a-

[Scottknoll]

My Ovation FIKI TKS AFMS limitations section requires dual alternators. I agree with the logic discussed so far. I just can’t imagine I can’t fly day vfr just like a non-fiki aircraft if my standby alternator is inop.

But I don’t see a clearly legal path to do so.

Btw, the airplane was delivered from the factory like this. The AFM Kinds of Operation Equipment List shows 1 alternator required, and the requirement for the second alternator is listed in the limitations of the TKS AFM supplement.

[carusoam]

Hmmmm...

We have a TKS guy that might be able to explain why the TKS AFM Supplement would prohibit single alternator flights in non-known ice conditions...  like a dry warm VFR day...

Did I get that right?

If yes, I’m inviting @CAV Ice Protection @CAV Ice
 

They are really good with support for their system...

Best regards,
 

-a-

[kortopates]

I don’t have a fuel pressure gauge nor was one ever installed in my 252 from the factory but yet it’s vfr and ifr certified. It calls into question why then does your require one fir vfr flying? Makes no sense to me. 

because it came with Fuel Flow it doesn’t need fuel pressure.


Sent from my iPhone using Tapatalk

[CAV Ice]

@carusoam The no-hazard system has no requirement for dual alternators.  The FIKI system does only for flight into known icing conditions.  If the flight is not into known icing (dry warm VFR day) the dual alternator requirement does not apply.  See page 8 of the flight manual supplement 08100-FMS:

 

"9. The following equipment must be installed and
operational for flight in icing conditions:"

[Scottknoll]

[mention=7104]carusoam[/mention] The no-hazard system has no requirement for dual alternators.  The FIKI system does only for flight into known icing conditions.  If the flight is not into known icing (dry warm VFR day) the dual alternator requirement does not apply.  See page 8 of the flight manual supplement 08100-FMS:
 
"9. The following equipment must be installed and
operational for flight in icing conditions:"

That makes perfect sense, I missed the fact that it was part of a sub-item in the limitations section. Was just reading it as a straight limitation. For the M20M through M20V, looks like page 6 & 7. Item 10g applies to alternators.

At some point I’ll learn to pay attention to the details. As always, thanks for the quick answer!

[A64Pilot]

18 hours ago, EricJ said:

Do you have a fuel flow gauge?   Usually that's what substitutes for FP, since the fuel flow gauge is usually actually a fuel pressure gauge.

 

Some are, the old ones usually were, they inferred fuel flow from pressure.

‘However more modern better fuel flow indicators actually measure fuel flow with a paddle wheel, and flow does not necessarily indicate pressure.

Then there is the small problem of fuel pressure indicators indicate the pressure of fuel supplied to the injection system, they measure the output pressure of the fuel pump. They exist to warn you of fuel pump failure, not the fuel pressure in the injector system.

‘However the old type of fuel flow indicators measure the fuel pressure in the injection system and by doing that indicate fuel flow, but you dont know pump pressure.

 

Edited March 8, 2021 by A64Pilot

[squeaky.stow]

On 3/7/2021 at 9:19 AM, Will.iam said:

I don’t have a fuel pressure gauge nor was one ever installed in my 252 from the factory but yet it’s vfr and ifr certified. It calls into question why then does your require one fir vfr flying? Makes no sense to me.

Aircraft that require a fuel pressure gauge generally also require that the electric pump be turned on for certain phases of flight. On the J it must be on for takeoff and landing, thus the requirement for an operational pump for both VFR and IFR, and there is a POH requirement to check the pressure when you turn it off after takeoff, thus the requirement for an operating fuel pressure gauge.

On the 252 we are never required to turn it on during normal operations so we have no fuel pressure gauge. It is interesting that we also have no list of required equipment of any sort in the POH even though Mooney did provide one in some older models. 

Even though we don’t require the pump for normal operations, it is required for emergency procedures. This is where @jlunseth ‘s point comes in. If you know your boost pump is not working and you don’t fix it because it’s not in any required equipment list, it might raise some embarrassing questions during an accident investigation if you lost power due to say, being late to switch tanks, and then were unable to restart a serviceable engine.
I would fly VFR without my second alternator because I have an out (land), but having no vacuum system for a backup, I would not fly IFR. If I had a vacuum driven backup ADI, different story.
 

[Will.iam]

25 minutes ago, squeaky.stow said:

Aircraft that require a fuel pressure gauge generally also require that the electric pump be turned on for certain phases of flight. On the J it must be on for takeoff and landing, thus the requirement for an operational pump for both VFR and IFR, and there is a POH requirement to check the pressure when you turn it off after takeoff, thus the requirement for an operating fuel pressure gauge.

On the 252 we are never required to turn it on during normal operations so we have no fuel pressure gauge. It is interesting that we also have no list of required equipment of any sort in the POH even though Mooney did provide one in some older models. 

Even though we don’t require the pump for normal operations, it is required for emergency procedures. This is where @jlunseth ‘s point comes in. If you know your boost pump is not working and you don’t fix it because it’s not in any required equipment list, it might raise some embarrassing questions during an accident investigation if you lost power due to say, being late to switch tanks, and then were unable to restart a serviceable engine.
I would fly VFR without my second alternator because I have an out (land), but having no vacuum system for a backup, I would not fly IFR. If I had a vacuum driven backup ADI, different story.
 

Why is that? That we don’t turn on the boost pump for any phase of flight? My CFI that got me checked out in the 252 did not believe me and looked up my POH and was really surprised. I like that I don’t have to turn it on but did not think about testing both the boost pump and the emergency pump to verify that they are functional. Add that to checking the wing tank vents. Thanks for helping me to be a safer pilot. 

[squeaky.stow]

8 minutes ago, Will.iam said:

Why is that? That we don’t turn on the boost pump for any phase of flight? My CFI that got me checked out in the 252 did not believe me and looked up my POH and was really surprised. I like that I don’t have to turn it on but did not think about testing both the boost pump and the emergency pump to verify that they are functional. Add that to checking the wing tank vents. Thanks for helping me to be a safer pilot. 

Good question. Maybe one of the engine experts will jump in here. Maybe TCM put a really robust engine driven fuel pump in the TSIO360 and they think failure is unlikely? It certainly puts out all the pressure you need for normal ops. If you turn on the boost pump in our airplanes when it isn’t needed it will run too rich and cause it to stumble. 

[larryb]

I'm pretty sure my TSIO360 won't start if I don't prime it, and priming uses the boost pump.

[kortopates]

53 minutes ago, Will.iam said:

Why is that? That we don’t turn on the boost pump for any phase of flight? My CFI that got me checked out in the 252 did not believe me and looked up my POH and was really surprised. I like that I don’t have to turn it on but did not think about testing both the boost pump and the emergency pump to verify that they are functional. Add that to checking the wing tank vents. Thanks for helping me to be a safer pilot. 

Its a Lycoming vs Continental thing, based on differences between Lycoming fuel injection and TCM fuel injection which a good portion of TCM fuel injection is controlled by the fuel pump in Continental engines, where Lycoming used a much simpler diaphram pumpTCM has never called on using the boost pump to change tanks (more on that later below). So sounds like your transition CFI didn't have much Continental experience. So I hope you still got a good understanding of the differences and intended uses of your Low Boost Pump, High Boost pump and your Prime pump which used to be a diverter valve to pump fuel into the induction tubes but should have been changed by a critical SB to pump fuel directly into the cylinder induction ports (via injectors). There is actually only one electric pump used for these activities with a voltage dropping resistor to give it 2 modes of high vs low, prime switch uses low and is now no different than low boost pump.  

Probably out of fear of libability concerns,  but recently TCM has now adopted Lycoming's stance to recommend using the low boost when switching tanks. You'll only see this on the later models POH's for the Acclaim & Utras etc.

Edited March 9, 2021 by kortopates

[squeaky.stow]

2 hours ago, larryb said:

I'm pretty sure my TSIO360 won't start if I don't prime it, and priming uses the boost pump.

The engine driven pump can’t pump until the engine is running. Priming is pretty much the only way we ever run the boost pump but it serves a useful secondary purpose to confirm that the electric pump still works. I went for several months with a failed low boost switch because I never turned it on, so I didn’t realize that the regulator had failed.

[carusoam]

Other fun things to know about Continental engines...

At WOT, during T/O...

the Lycoming requires the fuel pump to be turned on... then off at 1k’ agl...

the Continental... same thing, but the pilot doesn’t have to remember those steps... 

Now to find the reference for that...

Best regards,

-a-

[carusoam]

Special thanks go to CAV Ice!    @CAV Ice
 

Great support today, including Mooney Procedures!

There is a reason why we are nice to all the vendors...

They lend us great support just by asking...

I would love to a Fiki system on my ultimate Mooney!

Best regards,

-a-