AVSIG: R44 Raven II mechanical fuel pump wwswsigarch.jpg (7236 bytes)

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LouisC Grenierz
Public Guest


Reged: 05/15/04
Posts: 255
Loc: Quebec
R44 Raven II mechanical fuel pump
      #299068 - 09/18/10 11:08 PM

Is there a way to test that the mechanical fuel pump is working ? The last 30 seconds of a shut-down, when the electric pump is turning OFF, if the motor stop just before cutting the mixture, is this the official way of knowing that the mechanical pump is not working ?

Where is it in the POH ?

Thanks

Louis


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Anne Umphrey (KBED)
Top Gun


Reged: 04/28/04
Posts: 12756
Loc: KBED
Re: R44 Raven II mechanical fuel pump [Re: LouisC Grenierz]
      #299104 - 09/19/10 05:23 PM

Louis,

I have contacted a couple of folks about this, one being my mechanic. Waiting for an answer. My hangar mate says there is nothing in the POH about it.

Have you called the Robinson factory? They are very good about answering questions and explaining things.

RHC
310-539-0508 x215 will get you to maintenance.

Anne

--------------------
You haven't seen a tree until you've seen its shadow from the sky.
- Amelia Earhart, 1897 - 1937


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Evad Rellimhtug
Top Gun


Reged: 08/31/01
Posts: 2310
Re: R44 Raven II mechanical fuel pump [Re: LouisC Grenierz]
      #299115 - 09/19/10 08:03 PM

Quote:

Is there a way to test that the mechanical fuel pump is working? The last 30 seconds of a shut-down, when the electric pump is turning OFF, if the motor stop just before cutting the mixture, is this the official way of knowing that the mechanical pump is not working?




Louis,
Can you turn off the electrical pump with a switch or by pulling a breaker in the R-44? I would think that doing so while ground running it will tell you what you want to know. But... we're talking helicopters here. Them things are strange beasts.<g>

--------------------
Best,
Evad


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Anne Umphrey (KBED)
Top Gun


Reged: 04/28/04
Posts: 12756
Loc: KBED
Re: R44 Raven II mechanical fuel pump [Re: LouisC Grenierz]
      #299130 - 09/20/10 07:45 AM

Here is Paul's answer. Paul is a very experienced R44 pilot and knows it inside and outside.



Quick answer about testing the fuel pump: Yes.

Longer answer: There are two times the engine is running solely on the mechanical fuel pump: when you first start, but have not switched the clutch switch to the engage position, and during shutdown when you are disengaging the clutch.

The description of the fuel pumps is, I believe, in the Systems section of the POH where it talks about the electric pump being controlled with the clutch switch.

I took a quick look at the NTSB site and there were no accidents in Raven IIs due to fuel pump failures. This doesn't say that there has never been a dual pump failure, just that if there was such a failure it didn't result in an accident.

While you might devise a startup procedure to test the mechanical fuel pump, my personal feeling is that the chance of a double pump failure is very small and probably not worth worrying about given that you do test the mechanical fuel pump at the end of every flight. If Robinson though this was a likely failure, you would expect that there would be a test procedure incorporated into the startup sequence.

--------------------
You haven't seen a tree until you've seen its shadow from the sky.
- Amelia Earhart, 1897 - 1937


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Russell Holton
AVSIG Member


Reged: 07/07/05
Posts: 14136
Re: R44 Raven II mechanical fuel pump [Re: Anne Umphrey (KBED)]
      #299156 - 09/20/10 01:50 PM

Quote:

I took a quick look at the NTSB site and there were no accidents in Raven IIs due to fuel pump failures.




Please forgive the secpisim of a not-licensed-anything, but my reaction to that is:

1) - yet. I'd hate to be the first.

2) In my experience with equipment, the common failure modes change as the equipment ages. See response #1.

3) At least none that they were able to trace to the fuel pump. The NTSB is very good at what they do, but given a bad enough accident, I'm not sure as they would be able to verify the functioning of the fuel pump in every case.


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Ray Tackett
Top Gun


Reged: 04/30/04
Posts: 8892
Loc: Philadelphia, USA
R44 Raven II mechanical fuel pump [Re: Russell Holton]
      #299210 - 09/20/10 08:51 PM

I've got a couple thousand flight hours with dual (one electric, one
mechanical) fuel pumps. I have never had one fail, never mind two. In that
same time, I've had two other fuel system failures (not empty tanks) which no
pump could have overcome. Both of the fuel system failures were in Pipers,
not Robinsons.

In Robbies, I've had no failures of anything at all, but I have only a couple
hundred hours in them.

--------------------
Ray,

Owner, Lake Wood Be Gone

Turning quality lumber into sawdust and noise since 2013.


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Terry Carraway
Top Gun


Reged: 06/02/04
Posts: 7098
Loc: Maryland
Re: R44 Raven II mechanical fuel pump [Re: Ray Tackett]
      #299231 - 09/21/10 06:54 AM

Exactly, the dual fuel pump (1 x mechanical and 1 x electric) is a very common setup in piston aircraft. And it seems to work well, even on very old aircraft.

As long as there is some check at some point that at least one is working. And the R-44 seems to have that in there are two points that the engine is running off only the mechanical pump.

But notice, nobody seems to worrry about checking that the electric pump is actually working. :)

I know in some airplanes I have flown, you can check by going to a high setting and seeing a fuel presure rise.

--------------------
Terry
Mostly 0W3


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Sean Franklin
Top Gun


Reged: 08/15/04
Posts: 2566
Loc: Eureka Springs, Arkansas
Re: R44 Raven II mechanical fuel pump [Re: Terry Carraway]
      #299234 - 09/21/10 08:15 AM

Quote:

But notice, nobody seems to worrry about checking that the electric pump is actually working. :)



If it's fuel injected, you probably use the electric for priming so that's a test scenario.

--------------------
Eureka Springs, Arkansas


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Jeff Hartmann CIC
Top Gun


Reged: 05/18/04
Posts: 7323
Loc: Chico,CA
Re: R44 Raven II mechanical fuel pump [Re: Sean Franklin]
      #299236 - 09/21/10 08:46 AM

(short drift)
Remember when Cessna changed the checklist on Twin Cessnas, (Singles also? don't know) It had fuel pumps "on" for take off, they would run on low and only activate "high" with a drop in fuel pressure, if there was a blib, and the pump came on "high" when it wasn't needed it would flood the engine and it would quit.

http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX02FA214&rpt=fa

Sorry for the drift, but it is fuel pump related.

--------------------
Jeff

nothing clever to say right now...


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: R44 Raven II mechanical fuel pump [Re: Terry Carraway]
      #299239 - 09/21/10 09:17 AM

Quote:

But notice, nobody seems to worrry about checking that the electric pump is actually working. :)




I used to check both pumps (and tanks) when I was flying Cherokees:

-fuel selector to non-takeoff tank
-electric pump on
-verify fuel pressure
-start engine
-electric pump off
-taxi out
-fuel selector to takeoff tank
-runup
-electric pump on
-take off

--------------------
Ralph Jones
LS-4a N49LS 6R


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B. Butler (Oregonian)
Top Gun


Reged: 05/15/04
Posts: 9760
Loc: Ashland, Oregon
Re: R44 Raven II mechanical fuel pump [Re: Ray Tackett]
      #299254 - 09/21/10 12:24 PM

Quote:

I've got a couple thousand flight hours with dual (one electric, one
mechanical) fuel pumps. I have never had one fail, never mind two.




I have had the electric pump in my '67 Arrow fail once in 1200 hours (assuming it was original, had about 2800 hours on it at the time). I was at a remote location, swallowed hard and departed anyway.

Bill

--------------------
"Why not be a nihilist? A man has to believe in something."
-Bernie Gunther


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Evad Rellimhtug
Top Gun


Reged: 08/31/01
Posts: 2310
Re: R44 Raven II mechanical fuel pump [Re: B. Butler (Oregonian)]
      #299264 - 09/21/10 02:30 PM

Sometimes in the summer when it's real hot my RV6 will experience vapor lock with just the mechanical pump. The electric fuel pump is required to overcome that.

--------------------
Best,
Evad


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Terry Carraway
Top Gun


Reged: 06/02/04
Posts: 7098
Loc: Maryland
Re: R44 Raven II mechanical fuel pump [Re: Sean Franklin]
      #299359 - 09/22/10 04:23 PM

I thought of that later :)

--------------------
Terry
Mostly 0W3


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LouisC Grenierz
Public Guest


Reged: 05/15/04
Posts: 255
Loc: Quebec
Re: R44 Raven II mechanical fuel pump [Re: Anne Umphrey (KBED)]
      #299584 - 09/25/10 06:31 AM

Quote:

and during shutdown when you are disengaging the clutch.




Bingo !!

Thanks. A friend of mine was giving me a ride and the motor stopped at that point. The " it always does that" did not satisfy me.

At start-up, the electrical pump was left at priming position until the clutch switch was pushed (the motor was probably then working on the electrical pump)

Thanks for the explanation.

Lou


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