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fuel pump issues

D

dick seiders

Well Known Member
Landed last Sunday and while rolling out on runway engine quit. I immediately tried the start key and engine started right up with no further indication of problems. Ran some engine run tests today and found I could get only 3.6 lb psi regardless of rpm (tried 1400 up to 3900). Turned off Facet pump and it made no diff. Looked at the flow or consumption rate and it varied with rpm but only reached 3.5 gal. Sounds like one or both pumps to me. I am due to change mechanical pump anyway as it is 5 yrs old. Tried Facet with engine off and psi maxed out at 1.5 tp 1.7. Seems to me it was higher in the past maybe 2.0 or 2.1. Maybe both are bad? Any input is appreciated. Thanks.
Dick Seiders 120093
 
Hi Dick,

Normal fuel pressure for most is around 3.2 - 5.5 psi. This takes into consideration any of the Rotax fuel pumps. Since the engine quit what is your idle rpm set at? Should be around 1650-1750 rpm. Getting lower just beats the gearbox especially on the 912ULS with an 11:1 compression ratio. If you set the idle too low then you can risk an engine shutdown. The electric pump may not show an increase over the mechanical pressure, but quite a few people do show a .5 - 1 psi increase.

My guess is the fuel pump didn't cause the shutdown.
 
The fuel pressure sender is notoriously inaccurate. Do not trust it.
3.5 gph seems reasonable at 3900 RPM.
I think that the engine driven fuel pump is more likely to fail than the electric pump.
 
Sink said:
Since the engine quit what is your idle rpm set at? Should be around 1650-1750 rpm.

My guess is the fuel pump didn't cause the shutdown.
Click to expand...

Hmmm

Sounds like the same idle speed RPM #'s that Roger Lee always recommended ;)..... for best landing performance I would recommend that RV-12 owners try and not let the idle speed get above 1650 to improve.

I do agree that based on the information provided, the engine stoppage was probably the result of something other than a fuel pump problem.
 
fuel pump issue

Thank you gentlemen for the helpful info. I spent some time today thinking about my rush to judgment on both pumps. After all my concern about the apparent psi changes I was thinking about all the airplanes that are flying very well with only gravity to provide flow pressure.
I took the advice on idle speed setting altho I am not altogether certain how the pullback of the throttle can cut the flow of fuel sufficiently to cause engine stoppage, but it makes sense to look at the idle speed. I found that after warm-up to 150 degrees with a slow but steady pullback on throttle resulted in a a drop to 1300 rpm and it was still going down so I increased speed to 1650 locked the throttle and shut it down. After adjusting the stop screw to hopefully the same on both carbs it settled in at 1600 to 1650. Interestingly I found I could cause rpm to fall to 1500 with a rapid pull-back which surprised me a bit. However if I bring the throttle back steadily as opposed to rapid the rpm holds right around the 1600+ setting. Will take it up for a check mtc ride next day or so to see how she performs.
dick seiders 120093
 
Sorry to delay response, but weather and honey do's etc. Flew last Sat and air was very rough floated 12-1300 before getting mains on rwy. I believe the rough air was culprit, and at any rate couldn't be certain. Idle rpm was 1650-1700.
Decided to reset idle rpm using Rotax mech. sync method. This raised rpm to a solid 1750. Flew Sunday and wind was 3-8 out of 300 with gusts on rwy 28. Tried 3 times and floated 1000 ft before touchdown each time. Had throttle all the way back on final over nos at 60-65kts with 1/2 flaps. I normally use 1/2 flaps due to winds, but will try full next time to see If I can slow it to 50 over the nos.
If it still floats I may try going down to 1650 rpm but the gearbox really seems to like the higher rpm on shutdown.
Any other suggestions?
dick seiders 120093
 
dick seiders said:
Any other suggestions?
Click to expand...

As already mentioned numerous times previously, fully warmed up idle speed no higher than 1650 RPM.


If you don't like the shut down you can use a technique that makes it smoother....

With engine idling at 1800 -1850 (you are not supposed to idle slower than that anyway, even if the idle stops are set lower)

Pull the throttle to the idle stops

As the engine slows to your minimum idle RPM, switch off one ignition.

Switch off the second one off about 1/2 second later as the RPM is droping from the first one being switched off.

When done properly (takes a little practice), the engine will have a continuous and somewhat smooth RPM reduction from 1800 all the way to stopped.
 
Hi Dick,

Pull the stick back farther. You will slow down faster with a slightly higher nose up. The stick controls the speed, not the throttle. An idle rpm can be
1500-1900 and the stick still controls the speed. The plane quits flying at the same speed regardless of idle rpm and pushing the stick forward or backward controls the speed regardless of that rpm. You do this on approach for speed and is the same for landing. Sounds like you flew it down and rounded off level and let the speed bleed on its own.
 
Half flaps for takeoff. Makes a BIG difference particularly when you are heavy. So doing that you are getting maximum lift - exactly what you do NOT want for landing! Full flaps for landing. Install the $12 AOA mod and figure it out at altitude. At medium weights you can fly level at 48 knots, make turns, etc. with very low engine RPM.

Also, get a lot of practice slipping.
 
Sink said:
Hi Dick,

Pull the stick back farther. You will slow down faster with a slightly higher nose up. The stick controls the speed, not the throttle. An idle rpm can be
1500-1900 and the stick still controls the speed. The plane quits flying at the same speed regardless of idle rpm and pushing the stick forward or backward controls the speed regardless of that rpm. You do this on approach for speed and is the same for landing. Sounds like you flew it down and rounded off level and let the speed bleed on its own.
Click to expand...

Hmmmm..... sounds just like Roger Lee's answer.

Roger?

Do you know what flying behind the power curve is?
If a lot of RV-12 owners were to actually listen to your advice and attempted this at idle RPM's of 1900, a lot of RV-12 owners would be pranging their airplanes.

I don't understand why you need to keep finding a way to use an new alias (Isn't this the third one now... I lose count) to participate in this forum Roger. Your choice I guess, but please stay away when your info is contrary to what is safe for an RV-12.
 
Rvbuilder,

You have the wrong guy. I teach Rotax engine's and have 4500 hrs. of flight time behind me and I stand by my comment. This isn't the first time this has come up evidently. I talk to many RV owners on a regular basis and have flown several. I'm fairly well versed on their landing characteristics. I talk to hundreds of Rotax and light aircraft owners worldwide. This has been presented many times on forums and classes and for the most part 90% would agree. How do you think a jet lands?
It's easy enough for each person to test. You practice this very thing in slow flight. You set rpm to a selected point and pull the stick back to reduce to your target speed right down to stall if that is what you are practicing. The stick controls the speed and not the rpm especially at idle. I have talked to 3-4 RV12 owners that actually leave a tad throttle to touch. One of my guys in a class said that this was actually discussed at some fly-in and the majority agreed that idle rpm wasn't an issue once you realised the stick controls the speed.

I'm not telling any MFG where to set their rpm as any recommendations is on them.
I have been demoing this rpm issue for 20+ years.
 
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Sink said:
One of my guys in a class said that this was actually discussed at some fly-in and the majority agreed that idle rpm wasn't an issue once you realised the stick controls the speed.
Click to expand...
You didn't answer my original question, and I guess none of those guys know what flying on the back side of the power curve means either.....

You (clone of Roger) can keep selling it all you want, but if you go back and look through previous discussions here in the forum (there are many) you will find lots of people, that based on their own experience flying their own RV-12, support setting the idle speed properly and none that have supported your position that idle speed doesn't matter. So please go ahead and preach it on the CT forum but refrain from doing so here.

P.S.
If you are not Roger, then surely you can provide a link to info advertising you teaching Rotax engines in Florida......??? (I find it interesting that you say you teach Rotax which would imply you yourself are Rotax trained, but the only iRMT registered person within 100 miles of where you say you are, is named "Cindy")

P.P.S
Comparing how a high wing loading jet configures power for landing, to a light weight low wing loading aircraft speaks volumes about why people should question your advice regarding setting their idle speed....
 
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Hello all responders. I should probably should re-title the thread to rpm issues. I appreciate the varying input, but I normally use a combination of throttle pitch, and engine soeed when landing. I plan to drop the idle to 1500 to eliminate the float as this worked for me before I allowed the idle to drift down to too low a speed and will post results as before. Appreciate the help from all.
dick seiders 120093
 
Sink said:
Rvbuilder,

You have the wrong guy. I teach Rotax engine's and have 4500 hrs. of flight time behind me and I stand by my comment. This isn't the first time this has come up evidently. I talk to many RV owners on a regular basis and have flown several. I'm fairly well versed on their landing characteristics. I talk to hundreds of Rotax and light aircraft owners worldwide. This has been presented many times on forums and classes and for the most part 90% would agree. How do you think a jet lands?
It's easy enough for each person to test. You practice this very thing in slow flight. You set rpm to a selected point and pull the stick back to reduce to your target speed right down to stall if that is what you are practicing. The stick controls the speed and not the rpm especially at idle. I have talked to 3-4 RV12 owners that actually leave a tad throttle to touch. One of my guys in a class said that this was actually discussed at some fly-in and the majority agreed that idle rpm wasn't an issue once you realised the stick controls the speed.

I'm not telling any MFG where to set their rpm as any recommendations is on them.
I have been demoing this rpm issue for 20+ years.
Click to expand...

When landing a swept wing jet, power generally controls airspeed, the stick controls the v/s to remain on g/s.

In a light aircraft you can control the speed with your pitch, BUT in a RV-12, with that huge wing generating all that lift, I find that isn't always true.

But for me the biggest reason to set a higher RPM is protecting your gearbox imho.

The hardest part for me is figuring out where to land on a 12,000' runway to get down and clear the runway at the most convenient taxiway to the hangar!

Yeah - she can be a floater at times. I haven't ever landed 1/2 flap - God gave us full flaps for a reason.
 
Setting the idle RPM to the minimum allowed by the Rotax manual does not mean that the pilot should operate the engine at that minimum RPM. On final approach, the momentum of the RV-12 through the air will keep the RPM well above the idle set-point. After touchdown, the pilot should add throttle to keep the RPM well above the minimum allowed. Just because my idle RPM is set at the minimum allowed does not mean that I operate the engine at that RPM. My car might be capable of going over 100 mph. That doesn't mean that I drive that fast. I do not operate the Rotax at minimum RPM either, even though it has that capability. I fly out of a very short private strip and want to minimize floating.
 
Mich48041 said:
Setting the idle RPM to the minimum allowed by the Rotax manual does not mean that the pilot should operate the engine at that minimum RPM. On final approach, the momentum of the RV-12 through the air will keep the RPM well above the idle set-point. After touchdown, the pilot should add throttle to keep the RPM well above the minimum allowed. Just because my idle RPM is set at the minimum allowed does not mean that I operate the engine at that RPM. My car might be capable of going over 100 mph. That doesn't mean that I drive that fast. I do not operate the Rotax at minimum RPM either, even though it has that capability. I fly out of a very short private strip and want to minimize floating.
Click to expand...

Here, here....dead on�� And following Scott's engine shut-down procedure I.e. (1800ish rpm, shut "A" switch, then as rpm drops, shut off "B" switch results in minimum rattle tattle on the old gear drive!
 
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Phantom30 said:
Here, here....dead on�� And following Scott's engine shut-down procedure I.e. (1800ish rpm, shut "A" switch, then as rpm drops, shut off "B" switch results in minimum rattle tattle on the old gear drive!
Click to expand...

So, is there a reason that you shut down "A" first, and then "B"?? I've been using a similar routine for quite awhile now, but move right to left; "B", then "A", then Master. Is there some advantage to your stated routine that I am unaware of??

Tom
 
todehnal said:
So, is there a reason that you shut down "A" first, and then "B"?? I've been using a similar routine for quite awhile now, but move right to left; "B", then "A", then Master. Is there some advantage to your stated routine that I am unaware of??

Tom
Click to expand...

Doesn't matter.
 
Phantom30 said:
Here, here....dead on�� And following Scott's engine shut-down procedure I.e. (1800ish rpm, shut "A" switch, then as rpm drops, shut off "B" switch results in minimum rattle tattle on the old gear drive!
Click to expand...

Just to clarify....
for a smoother shut down I don't recommend shutting off an ignition at 1800 RPM....

- First you pull the throttle to idle (asuming you have been idling at 1800+ so that you are in the green range)
- As RPM drops to your minimum idle speed (what ever you have it set at, but somewhere below 1800) switch off one ignition.
- about a second later switch off the other.
 
Talk to ten pilots and you'll get ten favorite techniques.

I went from my Cherokee 180 to the RV-12. It took me a considerable amount of time to learn to plan ahead for the slippery RV. My Cherokee can salvage many a high and hot landing with 40 degrees flaps. The RV requires you to think ahead and slip early if you're high and hot. I have learned that if I get much above 60 KIAS on final it's time to slip.

With regard to the shutdown, we discussed this at the ROTAX course, and the instructor recommended shutting down from a higher than idle RPM to avoid the wear on the gearbox caused by the prop bouncing off the gearbox dogs. I have yet to find that sweet spot.
 
rvbuilder2002 said:
Just to clarify....
for a smoother shut down I don't recommend shutting off an ignition at 1800 RPM....

- First you pull the throttle to idle (asuming you have been idling at 1800+ so that you are in the green range)
- As RPM drops to your minimum idle speed (what ever you have it set at, but somewhere below 1800) switch off one ignition.
- about a second later switch off the other.
Click to expand...

Thanks for the clarification Scott...it's easy to pass on mis-information😔
 
Really an interesting thread in the widely diverse ideas. Looking at it all again I am betting on my technique, but only because I feel comfortable with it and am not proposing it for anyone who has their own idea.
Two thoughts come up as a result of my re read.

1. John Mc what do you do when air conditions require other than full flaps, like gusts , cross winds, rwy burbles? If calm I use full flaps, but conditions are seldom calm so I usually use 1/2 , or none depending.

2. Scott, on your last note you described what I had been doing from the start. The missing point is what is that elusive rpm number that is the minimum pain to the gearbox? I was cutting off at 1300 or so and that seemed to be too low (gearbox clank). It seems to me that letting engine settle to 1800 then slowly pull throttle back while cutting the switches with min. at 1500 for stop would be engine/gearbox comfortable. Am I worrying too much about this?
dick seiders 120093
 
dick seiders said:
Am I worrying too much about this?
Click to expand...

I could be wrong, but I think you are.

The 912 normal operating range (green) is from 1800 RPM and up.

It is (obvious, I know)not possible to shut one down without it transitioning from 1800 RPM down to zero.

All of our company airplanes are set up with the hot idle at 1600-1650 RPM.
Pilots control the idle with the throttle and keep it at 1800 or higher for all ground ops

I personally use the following procedure....
At shut down start from 1800-1850
Pull throttle to idle stop
About a second later (rpm usually down to about 1600) switch off one ign.
About a second after that switch off the other.

It never spends any time rattling at a specific RPM (like the 1300 you mentioned). It is one continuous, relatively smooth reduction in RPM until it stops.
It never spends any time running at a specific RPM.
 
1. John Mc what do you do when air conditions require other than full flaps?

IMHO 99.9% of the time you use full flaps. The 12 airframe is so clean anyways even with full flaps! Think of it this way, if you land 9 out of 10 time more than 1000 feet down the runway when the winds are light then you need to change your technique. Most likely your approach speed is to high.;)

2. Am I worrying too much about this?
Yes!:rolleyes:

.
 
When I got transition trainihng in Van's -12

I was taught to set RPM at 2500, **** one mag. pull throttle to stop, shut second mag off 2-3 seconds after the first. Sounds much the same except for starting higher.

I have the Bullyhawk soft start system which requires starting on mag A only, so I always shut B off first.

Wayne 120241/143WM. 325 hours as of today
 
Ok made an adjustment to idle at 1600. Flew 7 landings and with full flaps I am turning onto a taxiway within 1500' of threshold. Tried 1 at half flaps and rolled to assisted light brake stop at 1800'. As I slow the 12 to 50 over the threshold it will improve further. Regarding shutdown followed advice given and starting at 1800 click and click results in a smooth shutdown (for a 912).

Now the problem is my Moller gage but I will start a thread for that.
Thanks all.
dick seiders 120093
 
OK, here's my opinion from the peanut gallery!😜

I like landing with my Cherokee and RV with the flaps set for short field takeoff (half flaps on the RV and 25 degrees on the Cherokee). My reasoning is that if I need to go around at the last minute the flaps are already set to do it.

I only land with full flaps when I need to do a short field landing.

True confessions: I used to own a Yak-52 and once forgot the flaps on a go around. 360 HP is as good as Papal dispensation when you %#*? up!😈
 
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