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Fuel Flow Transducer location

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Captain Avgas

Well Known Member
I'm opting for an IO360 with Precision Silverhawk vertical updraft fuel injection. After a fair bit of research it does appear to me that the best location for me to instal the Floscan 201B fuel flow transducer is either between the mechanical fuel pump and the throttle body, or between the throttle body and the fuel distributor. Either should work well with this type of injection system providing there are no sudden discontinuities either going into or out of the transducer (and it is orientated with wires up).

However it seems that there are 3 possible support conditions for the transducer. 1. Installed mid-hose 2. Mounted on the firewall 3. Mounted on the engine.

Does anyone have any pix of their firewall forward transducer mounting. It's one of those things that are very difficult to conceptualise through words so pix would be appreciated (together with comments on success of course).
 
I would think you would definitely want it mounted on the firewall versus the engine for vibration consideration.
 
As my plane is a little older, the fuel flow I installed is the Electronics International FP-5L. They are adamant about the transducer being after the mechanical fuel pump; which means firewall forward. The two suggested mounting locations are a firewall mount and an in-line mount with certain restriction on height relative to the fuel pump and carb./throttle body. In most cases, a slight loop upwards in the discharge hose is recommended for any trapped air.

My mount is the inline mount with a strong attachment to the engine mount. It seems very accurate. On a recent flight back from Texas I stopped at Borger for fuel. On my 38 gallon RV-6A, the fuel flow showed 13 gal. remaining. The fuel truck pumped 25 gal. It has been within a tenth or two. Just as soon as I get the tools to do custom fuel hoses, I will probably switch to a rigid firewall mount.
 
Keep the hose lengths as short as possible. It keeps the volume of fuel down in the engine compartment. Less time to pick up heat.

Don
 
Rick6a said:
As a data point for possibilities to consider, I refer you to this thread of a transducer mounting that has for over 175 operational hours to date, proven to be a successful installation.
http://www.vansairforce.com/community/showthread.php?t=2784
Click to expand...

Rick, Thanks for your comments. I checked out your pix. It seems that you have a 90 degree fitting on the downstream side of the transducer. Do you find that this affects accuracy at all. Secondly, are you using aluminium fittings on the fuel line....is that considered Kosher. Thirdly the transponder is not mounted with the wires vertical (is that not a requirement of your particular type of transponder). Fourthly, some people have said that it is advantageous for the fuel line to be rising as it leaves the transducer. What do you think about that.

Sorry for all the questions.
 
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Don at Airflow said:
Keep the hose lengths as short as possible. It keeps the volume of fuel down in the engine compartment. Less time to pick up heat.

Don
Click to expand...

Don, a very interesting and relevant point that I must admit I had not even considered...but it makes sense. Where would you mount the transducer. Something in the back of my brain favours the firewall but that would almost certainly require longer hoses than an engine mount or an "in-line" set-up.
 
N941WR said:
This looked like a good spot to me. I can't remember who I copied it from though.

Click to expand...

That set-up places the transducer before the mechanical fuel pump. My understanding is that this is not ideal for two reasons. 1. The transducer may be less accurate when the electric fuel pump is turned on. 2. It creates another system of fuel flow resistance upstream of the mechanical pump thus increasing the possibility of vapour lock.

I'm reasonably convinced the correct position is either between the mechanical pump and the throttle body, or between the throttle body and the divider....but where to mount the transducer...that's the million dollar question.
 
My fuel flow transducer (Flowscan 201B) has been between the fuel selector and the boost pump in the cockpit of my -6 for almost 14 years and works great.
 
on engine

Rob Hickman at Advanced Flight Systems indicated a preference for placing the transducer downstream of the fuel injection servo. Mine is on a small steel angle mount I fab'd which is bolted to the angled boss on the lower right side of the engine case behind the alternator and FAB. This was the only way I could think of that would keep the lines short and still allow placement of the transducer between the servo and the spider. It keeps all the fuel lines short and after almost 50 hrs, I've had no weird flow indications nor fuel vaporization problems. YMMV...
 
Flow transducer installation on FI engine

Here?s how we install a flow transducer on a fuel injected installation.

The installations that we have done have all used the Flow Scan transducer. I have not personally done one using the big cube type.

We use AN816-4-4D fittings on the inlet and outlet side of the transducer. Heck the transducer housing is aluminum. And we use aluminum fittings on our fuel controls. But if it makes you feel better use AN816-4-4 steel fittings.

We have installed as short as 3? of #4 hose (straight fittings only) on the inlet side of the transducer with no operational problems.

We have installed a full flow 90 degree #4 hose fitting (bent tube type) on the outlet of the transducer with no operational problems.

We have mounted the transducer with wires up and wires horizontal with no operational problems.

We typically mount the transducer in the metered fuel line (hose between the fuel control (servo) and flow divider (spider)). On some installations as space permits the transducer is Adel clamped to a motor mount tube. In most cases the transducer is supported by only the hoses and the hoses are supported or clamped off to some structure. We never mount the transducer directly to the engine (although I have seen that done. On a Piper Malibu the transducer is screwed directly into the outlet side of the engine driven pump), I feel the direct engine vibration is not good for the transducer (just my personal opinion).

We wrap the transducer with fire sleeve after the installation is complete.

In any case we keep the length of hose as short as possible to eliminate fuel volume in the engine compartment. We don?t like putting the flow transducer on the suction side of pumps (but I know there are installations done this way and they work) due to the increased pressure drop put on the inlet side of the fuel pump.

An installation on a carbureted engine will be different but I would think that the transducer should be placed after the engine driven fuel pump and before the carb inlet.
 
Here is my attempt so far with the transducer on my 0-320 (carb). I am not sure if I will end up installing it this way but so far it looks OK. The bend in the hose seems to give the whole thing natural support. It is not attached to the firewall in any way. The section with the short hose and the transducer is somewhat rigid so if I support it, I was thinking of some type of flexible brace from the fittings on the aft side of the transducer to the mount tubes on both sides. The plastic ties on the fire sleeve are only temporary. Any comments, suggestions or criticism would be appreciated.

Fin
9A Australia

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#4 hose ??

Don at Airflow said:
We have installed as short as 3? of #4 hose (straight fittings only) on the inlet side of the transducer with no operational problems.

We have installed a full flow 90 degree #4 hose fitting (bent tube type) on the outlet of the transducer with no operational problems.
Click to expand...
Do you normally run #4 (1/4") hose between the servo and the flow divider, or is this only when you instal a flow transducer. What if the transducer is located between the mechanical pump and the servo....do you still advocate the use of #4 hose. In my ignorance I had imagined that all hose up to at least the servo would be #6 (3/8") to reduce line friction.


Don at Airflow said:
We typically mount the transducer in the metered fuel line (hose between the fuel control (servo) and flow divider (spider)).
Click to expand...
Is this a specific requirement with the AFP system because of fuel return lines associated with that product. For instance with the Precision Silverhawk system (which has no return line) wouldn't it be just as satisfactory to mount the transducer between the mechanical fuel pump and the servo.

Thanks for your valued contribution Don.
 
Finley Atherton said:
Here is my attempt so far with the transducer on my 0-320 (carb). I am not sure if I will end up installing it this way but so far it looks OK. The bend in the hose seems to give the whole thing natural support. It is not attached to the firewall in any way. The section with the short hose and the transducer is somewhat rigid so if I support it, I was thinking of some type of flexible brace from the fittings on the aft side of the transducer to the mount tubes on both sides. The plastic ties on the fire sleeve are only temporary. Any comments, suggestions or criticism would be appreciated.

Fin
9A Australia

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Click to expand...

Yes I'd like to know what others think of this arrangement as well. I suspect it might work quite well in that it seems to comply approximately with all of the important installation parameters as far as flow accuracy is concerned....but don't place too much weight on my opinion (in fact don't place any weight on my opinion.!!!)

I'm presuming the transducer is located between the mechanical pump and the carbie. What size hoses did you use.

Incidentally where are you based in Oz.
 
Quote:
Originally Posted by Finley Atherton
Here is my attempt so far with the transducer
-------

This "in-line" arrangement is very close to what I have; except that I have a support point on the longer hose to the engine mount tube using hose clamps.

My limited data so far: Good accuracy (+- 0.2 gallons) with about 20 flight hours after installation.
 
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Captain Avgas said:
I'm presuming the transducer is located between the mechanical pump and the carbie. What size hoses did you use.

Incidentally where are you based in Oz.
Click to expand...

The transducer is between the mechanical pump and the carb. Standard 3/8" hose with F-816-6D fittings. The hose from the fuel pump to the transducer is actually the standard Vans hose that is supposed to go between the gascolator and the mechanical fuel pump. My nearest town is Armidale, northern NSW.

Fin
 
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Captain Avgas said:
Do you normally run #4 (1/4") hose between the servo and the flow divider, or is this only when you instal a flow transducer. What if the transducer is located between the mechanical pump and the servo....do you still advocate the use of #4 hose. In my ignorance I had imagined that all hose up to at least the servo would be #6 (3/8") to reduce line friction.



Is this a specific requirement with the AFP system because of fuel return lines associated with that product. For instance with the Precision Silverhawk system (which has no return line) wouldn't it be just as satisfactory to mount the transducer between the mechanical fuel pump and the servo.

Thanks for your valued contribution Don.
Click to expand...

It doesn?t matter if it?s Airflow or Precision; both systems use a #4 metered fuel hose. And again we want to keep the fuel volume to a minimum on a fuel injected installation.

We prefer to put the transducer in the metered fuel line as the flow from the servo is smoother, there can be some pressure pulsing from the engine driven pump which may make the read out a little unstable (has to do with sample rate). But like I said in the previous post both installations have been done with success. If you place the flow transducer in the hose on the outlet side of the engine driven fuel pump then you would use whatever size hose that is normally used in that location which is typically #6.

The purge return that we use on our systems has nothing to do with the placement of the flow transducer, as there is no fuel returning when the engine is running. The Precision Silver Hawk (RSA-5), and the Airflow Performance fuel injection systems do not require a return line for operation. We have sold many purge valves to people running Bendix/Precision fuel injection systems to eliminate the hot start and fuel bleed off at shut down problems.

Don
 
Captain Avgas said:
I'm opting for an IO360 with Precision Silverhawk vertical updraft fuel injection. After a fair bit of research it does appear to me that the best location for me to instal the Floscan 201B fuel flow transducer is either between the mechanical fuel pump and the throttle body, or between the throttle body and the fuel distributor. Either should work well with this type of injection system providing there are no sudden discontinuities either going into or out of the transducer (and it is orientated with wires up).

However it seems that there are 3 possible support conditions for the transducer. 1. Installed mid-hose 2. Mounted on the firewall 3. Mounted on the engine.

Does anyone have any pix of their firewall forward transducer mounting. It's one of those things that are very difficult to conceptualise through words so pix would be appreciated (together with comments on success of course).
Click to expand...

JPI has a very nice Installation Manual which outlines placing the transducer (#1) mid hose, between the servo and the fuel distributer (spider). This document can be downloaded from JPI's web site at

http://www.jpinstruments.com/700-800_FF_install.PDF

Charlie Kuss
 
chaskuss said:
JPI has a very nice Installation Manual which outlines placing the transducer (#1) mid hose, between the servo and the fuel distributer (spider). This document can be downloaded from JPI's web site at

http://www.jpinstruments.com/700-800_FF_install.PDF

Charlie Kuss
Click to expand...

It's an excellent document that I have previously read (highly recommended) and it confirms several things that I pointed out earlier. 1. Aluminium fittings into the transducer are not recommended. 2. When using a FI system with no vapour return lines the correct location for the transducer is between the mechanical fuel pump and the throttle body. 3. The transducer output port should be mounted even or lower than the throttle body (rising hose).

However providing the parameters for an installation with least fuel flow error is not the same as explaining how one can achieve those parameters in the context of an actual installation. That's what we're attempting to achieve here and I think the best solution that has been put forward so far is Finley Athertons. However there may be room for improvement. Finley's design may require support and it places the transducer very close to the exhaust pipe.

Any other builders like to send some pix of their transducer installation.
 
Captain Avgas said:
Finley's design may require support and it places the transducer very close to the exhaust pipe.
Click to expand...

Your are right. It will need support but this should be no problem.
The transducer is just over two inches from the exhaust pipe. I plan to wrap the transducer in two layers of Fire Sleeve and also install another exhaust pipe heat shield between the exhaust pipe and the transducer. Also this should be an area with good airflow.

Fin
 
VA-188 Mount

I noticed that Vans sells a VA-188 mount for the Floscan. Does anyone have this mount that might describe its location and mounting orientation (picture is always good)?

THanks,
Scott
 
UPDATE

I was never really happy with the transducer installation I had in post # 15 for my 0-320 (carb). So, here is my latest and final installation. I have ground run, but not flown yet. Everything works as it should and the transducer is securely attached to the engine mount. This installation just about satisfies all the installation recommendations. The clamps are #11 and there are ?? OD sleeves on the AN3 bolts that hold the transducer to the clamps.

FIN 9A

http://i211.photobucket.com/albums/bb6/fpgath/TRANSDUCER.jpg

EDIT. Added an extra photo below for clarification.

http://i211.photobucket.com/albums/bb6/fpgath/TRANSDUCER2.jpg
 
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Mounted on the Engine

I had my engine supplier mount the transducer to the divider on the top of the engine. I have the Precision vertical updraft injection. The unit is wrapped in firesleave and utilises aluminium fittings.

When I enquired as to the safety of doing this, I was told that there are certified units using the flowscan module in this configuration without issues. This setup meant I can use the standard (single) hose suppkied by Vans.

I plan to support the hose where it attaches to the fuel flow sensor.

Regards
Richard

RV-7A - Firewall forward.
 
rwtrwtau said:
I had my engine supplier mount the transducer to the divider on the top of the engine. I have the Precision vertical updraft injection. The unit is wrapped in firesleave and utilises aluminium fittings.

When I enquired as to the safety of doing this, I was told that there are certified units using the flowscan module in this configuration without issues. This setup meant I can use the standard (single) hose suppkied by Vans.

I plan to support the hose where it attaches to the fuel flow sensor.

Regards
Richard

RV-7A - Firewall forward.
Click to expand...

Do you have any pix of this installation. Who was the engine supplier that installed it. And was it the engine supplier that recommended this position. If not then who recommended it.

Finally, can you state what certificated planes have this configuration.
 
Captain Avgas said:
Do you have any pix of this installation?
Click to expand...

Hi Bob, I will post some when I return form overseas.

Captain Avgas said:
Who was the engine supplier that installed it. And was it the engine supplier that recommended this position. If not then who recommended it.
Click to expand...

Mattituck supplied my engine, and when I asked about how to mount it in the line between the divider and the servo this particular configuration was Mahlon's recommendation.

Captain Avgas said:
Finally, can you state what certificated planes have this configuration.
Click to expand...

No. I didn't ask but given where the advice came from I believed I had good reason to trust it. There is at least one aircraft type already mentioned in this thread though.

I suspect mounting the sensor to the engine may not be the best for it long term, but my main concern is if it presents a hazard. I do not think so, but I am going to check with Floscan directly and report what I find. If there is any issue I will look at installing two hoses.

Richard
 
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Example Pictures

G'day Bob et all,

I contacted Floscan regarding this installation and they refused to provide any information, other than telling me it is the reseller that should advise me of the correct installation.

I have included a picture of the installation below, you can see the fuel flow sensor attached to the divider and in the bottom right hand corner, the brown Aeroquip hose running down the back of the engine to the servo.

The sensor and fittings were originally double firesleaved and cable tied. I have removed the firesleaving to take the photo.

I would be interested in people's comments.

Regards
Richard

fuellflow.jpg
 
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The only issue I have with that is vibration metal fatigue from the mass of the sensor riding on the nipple connecting it to the fuel divider. I see this commonly with compressors, anything of even small mass hanging on a nipple like that will suffer fatigue cracking rather quickly under vibration.
 
I have to agree with Greg. Not only do you have the mass of the sensor, but the mass of the fuel line. You really should add some support for the transducer.
 
Mel said:
I have to agree with Greg. Not only do you have the mass of the sensor, but the mass of the fuel line. You really should add some support for the transducer.
Click to expand...


I agree. I would have reservations about that set-up and frankly I'm surprised that Mattituck would recommend it. Did Mattituck actually instal it.....or did you instal it.

Also my understanding is that fuel flow transducers don't like being mounted directly onto the engine...apparently the vibrations damage the bearings.
 
Safety first

Safety should always be your first consideration when installing the fuel flow sensor in the engine compartment.

I will gladly give up best accuracy over safety any day of the week. The more connections you have the more potentials for a leak. If you mount your sensor in the engine compartment and it was to leak at the fitting or you had complete catastrophic fatigue at the fitting where do you want the gas to spill? On the engine or under it?

Either way it could have deadly consequences.

I haven't installed my sender yet but these are the thoughts running through my head when I look at some to the photos and read the explanations.

The firewall install maybe better from a "safety" perspective. I have been considering mounting the sensor down stream of the high pressure fuel pump in the cockpit. My only concern is if it were to leak. However a fuel leak in the cockpit maybe unpleasant but I would to expect a fire. A fuel leak or catastrophic fitting failure in the engine compartment will almost certainly cause a fire.

My two cents-

If installing the sensor in the engine compartment use steel fitting, Adel clamps on the hoses and carefully consider the safety implications of where you are installing the sensor.

Food for thought.

Paul
RV-7A (finishing kit)
 
Fuel Flow fluctuations

N941WR said:
This looked like a good spot to me. I can't remember who I copied it from though.

Click to expand...


I have my Floscan fuel flow transducer mounted just like the picture above. Overall, it seems to be reasonably accurate (within 5% or less).

My beef with the installation is that the fuel flow indication will fluctuate over a 2 to 3 gph range, e.g. 7 to 10 gph after I've leaned it to about 8 to 8.5 gph depending on rpm and altitude. Would a different location give a steadier indication? Anyone with operational experience care to share?

I've got about 230 hrs. on my ECI O-360 carb engine installation with a Sensenich fixed pitch prop on my -7A.

Mike
 
Re rwtrwtau's installation...

I thought Rule 1 was never install transducers directly to the engine? Van's repeatedly makes this point - all transducers firewall mounted via flexible hoses?
 
Question for Finley

Finley Atherton said:
I was never really happy with the transducer installation I had in post # 15 for my 0-320 (carb). So, here is my latest and final installation. I have ground run, but not flown yet. Everything works as it should and the transducer is securely attached to the engine mount. This installation just about satisfies all the installation recommendations. The clamps are #11 and there are ?? OD sleeves on the AN3 bolts that hold the transducer to the clamps.

FIN 9A

http://i211.photobucket.com/albums/bb6/fpgath/TRANSDUCER.jpg

EDIT. Added an extra photo below for clarification.

http://i211.photobucket.com/albums/bb6/fpgath/TRANSDUCER2.jpg
Click to expand...


Finley,
How does your new installation work?

Mark
 
Mark Burns said:
Finley,
How does your new installation work?

Mark
Click to expand...
Mark,
I have flown about 25 hours now. Structurally the installation continues to look good. Fuel flows indications are accurate and stable at higher power settings, however the readings fluctuate considerably at lower power settings. I am guessing that there is turbulence created on the inlet side by the 90 degree bend. My understanding is that it is more important to have a straight run into the transducer, so I plan to re-orientate the transducer so that the bend is on the outlet side.

Fin 9A
 
Hi Fin, good to hear from you again. Please report back when you remove the 90 degree bend on the inlet side of the transducer. It would be VERY interesting to learn if it improves accuracy.

Incidentally, I plan on doing something very similar to you, but I'm going to try avoiding the 90 degree bend, either in or out.

Also I plan to use only steel fittings. I suspect that the aluminium fittings might fatigue in that application. You're certainly very brave using that aluminium 90 degree fitting in that location. It could produce such a nasty outcome if it cracked (I'm just thinking of your welfare).

Cheers Bob




Finley Atherton said:
Mark,
I have flown about 25 hours now. Structurally the installation continues to look good. Fuel flows indications are accurate and stable at higher power settings, however the readings fluctuate considerably at lower power settings. I am guessing that there is turbulence created on the inlet side by the 90 degree bend. My understanding is that it is more important to have a straight run into the transducer, so I plan to re-orientate the transducer so that the bend is on the outlet side.

Fin 9A
Click to expand...
 
Captain Avgas said:
Hi Fin, good to hear from you again. Please report back when you remove the 90 degree bend on the inlet side of the transducer. It would be VERY interesting to learn if it improves accuracy.

Incidentally, I plan on doing something very similar to you, but I'm going to try avoiding the 90 degree bend, either in or out.

Also I plan to use only steel fittings. I suspect that the aluminium fittings might fatigue in that application. You're certainly very brave using that aluminium 90 degree fitting in that location. It could produce such a nasty outcome if it cracked (I'm just thinking of your welfare).

Cheers Bob
Click to expand...
Hi Bob,
It may be awhile before I get around to changing the installation. I appreciate your suggestion about the 90 degree bend and I may indeed change it to steel. I have had the installation inspected by 4 LAMEs including the AP. None of them suggested it may be suspect. You are the first person that has suggested it may be inadequate.

Fin 9A Flying
Australia
 
Finley Atherton said:
Hi Bob,
It may be awhile before I get around to changing the installation. I appreciate your suggestion about the 90 degree bend and I may indeed change it to steel. I have had the installation inspected by 4 LAMEs including the AP. None of them suggested it may be suspect. You are the first person that has suggested it may be inadequate.

Fin 9A Flying
Australia
Click to expand...


Fin, I recommend the following document as being excellent reading on the installation of fuel flow transducers.

It is the definitive transducer installation manual supplied by JP Instruments. It is available as a PDF file at the following http://www.jpinstruments.com/downloads.html

Download the file: Fuel Flow Installation Manual for EDM-701.

You will note that JPI specifically specify steel fittings into the transducer. I would imagine that for a 90 degree bend the situation would be even more critical.

Cheers Bob
 
Bob is 100% correct. The JPI doc will give you all the info you need to install the fuel flow unit correctly. It's much preferable to just doing it as some others have as I'm sure you can see from this ongoing thread.
Danny
 
the best location IMO

This is a pic of a floscan tranducer mounted on a friend's F1. Very simple and clean, works accurately. Its always in the path of cool air in flight, easy to replace if it quits working. Note the bracket supporting the transducer. The fitting was made from a 1/8" NPT steel nipple welded to a 1/4" NPT steel nipple at 90 degrees.



Regards,
Bob Japundza
RV-6 flying F1 under const.
Indy
 
Captain Avgas said:
Incidentally, I plan on doing something very similar to you, but I'm going to try avoiding the 90 degree bend, either in or out.
Also I plan to use only steel fittings. I suspect that the aluminium fittings might fatigue in that application. You're certainly very brave using that aluminium 90 degree fitting in that location. It could produce such a nasty outcome if it cracked (I'm just thinking of your welfare).

Cheers Bob
Click to expand...

I don't want to start a steel V aluminium war so let me say that I agree that a steel 90 degree bend would be preferable to an aluminium one. For others that have a aluminium 90 degree bend in their fuel lines and are feeling brave (reckless??) I think you can be reasonably confident that your fitting is not in immediate danger of falling apart. Let me restate, my installation (see post #25) was inspected by 4 LAMEs (Australian for Licensed Aircraft Maintenance Engineer). Yesterday I discussed it further with one of the LAMEs, an experienced Chief Engineer who maintains a large fleet of agricultural aircraft plus the usual array of Cessnas, Pipers etc. In his opinion the aluminium 90 degree bend in this installation was completely adequate and acceptable.
As far as I can tell you cannot get a -6 Aeroquip 90 degree bend in steel. You can get a -4 in steel, but all the larger sizes are in aluminium. I presume this is because the -6 and larger sizes are considered bulky enough to handle the expected stresses??. If you want this fitting in steel you may have to go to Stratoflex or similar.

Fin 9A
 
Vans Flo-scan brackett

Anybody have a picture of the VA-188 brackett and where it mounts.
Thanks
 
rocketbob said:
Its always in the path of cool air in flight, easy to replace if it quits working.
Click to expand...

I've never seen a fuel flow transducer installed in this location on a certificated aircraft. Have you ?

With time, the engine vibration will damage the precision bearings.
 
Bob how will the bearings get damaged? The wheel is dampened in fuel. I have seen many installations of the transducer in the metered fuel line on both experimental and certificated aircraft. I have mine installed in my -6 in the fuselage free of any vibration and it is now starting to read erratically. They will wear out regardless of where they are mounted. The EI cube transducers have a much better MTBF than the Floscan units do, according to the datasheet EI provides with the transducer. They are much less expensive as well.

Regards,
Bob Japundza A&P
RV-6 flying ~900 hours F1 under const.
Indy
 
rocketbob said:
Bob how will the bearings get damaged? The wheel is dampened in fuel. I have seen many installations of the transducer in the metered fuel line on both experimental and certificated aircraft. I have mine installed in my -6 in the fuselage free of any vibration and it is now starting to read erratically. They will wear out regardless of where they are mounted. The EI cube transducers have a much better MTBF than the Floscan units do, according to the datasheet EI provides with the transducer. They are much less expensive as well.

Regards,
Bob Japundza A&P
RV-6 flying ~900 hours F1 under const.
Indy
Click to expand...


Bob, a few points:

1. I am not aware that any manufacturer of fuel flow instrumentation has recommended the type of transducer installation you photographed. If you have data to the contrary.... please refer to it.

2. In fact JP Instruments in their installation guide SPECIFICALLY advise that there MUST be flexible hose both in and out of the transducer.

3. I repeat that I have not personally seen a certificated aircraft with this transducer installation method (ie transducer cantilevered off the spider valve with an unsupported hose on the other side). You say that there is a certificated installation identical to this....please refer to it.

4. I note that neither the transducer nor the hose has firesleeve. That in itself says volumes about the merits of this particular installation.

5. You say that the vibrations induced by mounting the transducer directly to the engine will not affect the precision bearings. Do you have technical data on that....please refer to it.

I believe that this is a very unsatisfactory transducer installation from a point of view of precedence, safety, and accuracy. I would not recommend that other builders follow this example.

If you have specific technical data that suggests otherwise then please put it forward. Not personal opinions....data.

Honestly, FWF fuel supply installation has no redundancy. If it fails the fan stops and there is every likelihood of an horrendous fuel fed fire. It is not the place for "experimental" make-it-up-as-you-go-along installations. This is the one place above all to be VERY conservative.
 
Captain Avgas said:
Bob, a few points:

I believe that this is a very unsatisfactory transducer installation from a point of view of precedence, safety, and accuracy. I would not recommend that other builders follow this example.
Click to expand...

Bob, without getting into an argument I wholeheartedly disagree with you and lets leave it at that. The installation works fine, is simple and robust, has been running on that particular rocket for several hundred hours now with not a single problem. I've been around this stuff for a lot of years now and trust me, I've seen some tranducer installations that were far less robust than the one I presented. I know of one particular Aerostar that has the transducers adel clamped to pushrod tubes, no firesleeve on the transducer. Its common to see them on top of the engine. If you don't believe me, next time you go to a flyin have a look for yourself on all of the uncowled engines you may see.

Regards,
Bob Japundza A&P
RV-6 flying ~900 hours F1 under const.
Indy
 
rocketbob said:
Its common to see them on top of the engine. If you don't believe me, next time you go to a flyin have a look for yourself on all of the uncowled engines you may see.
Click to expand...

Bob, you're talking about experimental aircraft....in that category it's often the blind leading the blind.

My advice to builders on transducer installation is to follow the recommendations of the instrument manufacturer because that advice will be based on history and precedence rather than intuition.
 
Didn't really seem like Avgas was trying to start an argument, just asking for data to support claims. As far as endorsing a particular installation because you've seen lots of em like this at fly-ins is, in my opinion, not a good idea. I hate to agree with the bit about the blind leading the blind, but in some ways that really is the case. I have to assume that the manufacturer says to not mount it on the engine and to not use a rigid connection because their engineers have found problems with this setup. If I trust them to make the device, then how can I disregard their advice on the install? The simple fact is that if a fuel line on top of the engine snaps off in flight the pilot will in all probability be killed in a horrible fiery crash, maybe even taking a house or two with him. If we were talking about primer vs. bare I'd say to each his own, but with fuel system design I really can't afford to disregard anybody's advice.
 
The way it was installed in my friends rocket one could shake the whole airplane just by grabbing onto the floscan transducer. For the record the gentleman who built that airplane has built/owned 3 RV-4's and a F1, and has something like 5000 hours in RV's. You ought to see the heavy equipment he's designed and built himself. Certainly not a case of the "blind leading the blind" here, in fact he's a very talented mechanic who has a very firm grasp of how things can break through fatigue and vibration.

Once again I will reiterate that it is a solid installation and if you really studied it carefully especially in person you would see why it works well. There is a steel strap supporting it that makes the assembly suprisingly rigid. That's all the data I need to install mine exactly the same way.

I honestly don't understand the mentality that exists in the garage-built crowd anymore where something you read must be followed as gospel, and alternative ways of making things are frowned upon just because someone says there's no data to support what one is doing. EAA- EveryAirplaneAlike.

Regards,
Bob Japundza A&P
RV-6 flying ~900 hours F1 under const.
Indy
 
Finley Atherton said:
Mark,
I have flown about 25 hours now. Structurally the installation continues to look good. Fuel flows indications are accurate and stable at higher power settings, however the readings fluctuate considerably at lower power settings. I am guessing that there is turbulence created on the inlet side by the 90 degree bend. My understanding is that it is more important to have a straight run into the transducer, so I plan to re-orientate the transducer so that the bend is on the outlet side.

Fin 9A
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I may have been a bit premature with my statement above (see posts # 34 & 35) as I now seem to be getting reasonably accurate and stable readings at both high and low power settings. Like many others I have had erratic and and sometimes frighteningly low fuel pressure readings. As a result, I have been progressively insulating the fuel line fittings and gascolator and installing blast tubes to the mechanical fuel pump. I don?t know if this is the reason for the better fuel flow readings, but it is the only thing I have changed in the fuel system. It is a bit to early to tell yet if the installation is working OK but it now looks promising.

Fin 9A
 
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