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mtherr(at)yahoo.com
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 Posted: Thu May 27, 2010 11:08 am Post subject: Bad takeoff, but still good landing |
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Last sunday was a beautiful day here in my region and I couldn't resist flying after completing the engine portion of my annual inspection. I changed the oil, tested the compression (150 +-5 on all cylinders), timing OK, removed valve covers... all neat, cleaned air filter, etc, etc... all was GREAT 
Well, I did my preflight inspection, did my runnup (at about 3600 rpm) near runway 15 of Beloeil airport, positioned myself on the runway and applied full throttle. The feeling of accelerating and taking off on such a beautiful day was enjoyable... for about 4 seconds... I climbed to about 5 feet in the air and then, total loss of power (like lack of fuel). I was getting close to mid-runway (maybe even past it... don't remember), and I pulled the throttle, and landed the plane. The engine was still running at low rpm.
Then I went to an area to check the engine behavior... when I raised the throttle above 4000 rpm, it would do the same thing. I then tried at lower rpms... would just take more time and at about 2100 rpm, the engine would run smooth, miss and run smooth again.
My first idea was the fuel supply... so I disconnected the fuel line and filter from the carburetor and tested the fuel flow.. very good.. certainly, the issue is not that. I then removed the top of the carburetor (Holley 5200) to see if the bowl has fuel and to see if the float valve operates properly... bowl was OK (but with some small debrits on the bottom) and floats appeared to work OK (I applied fuel pressure while playing with float movement and making a mess besides the catch can I was using).
My questions: what failures could create this condition?
1. fuel system ? (I think so)
2. ignition system ?
3. cam shaft ?
4. ?
Oh... a funny thing... I'm surprised to notice I did not get excited through this... I don't think my heart beat got any faster during that failure.
I got a strange feeling that I'll miss many good days of flying opportunities now.
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://pages.infinit.net/mthobby
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larry(at)macsmachine.com
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| Posted: Thu May 27, 2010 12:49 pm Post subject: Bad takeoff, but still good landing |
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Michel,
I'd look for a fuel restriction in the line, gascolator, filter or
anywhere ahead of the carb. This doesn't sound like an ignition, choke
or spark type failure.
A fuel restriction would allow you to get full throttle until the engine
need gets ahead of the flow. Then it would starve itself at full setting
after running full out
for a short time.
Larry McFarland 601HDS at www.macsmachine.com
Michel Therrien wrote:
| Quote: |
Last sunday was a beautiful day here in my region and I couldn't resist flying after completing the engine portion of my annual inspection. I changed the oil, tested the compression (150 +-5 on all cylinders), timing OK, removed valve covers... all neat, cleaned air filter, etc, etc... all was GREAT
Well, I did my preflight inspection, did my runnup (at about 3600 rpm) near runway 15 of Beloeil airport, positioned myself on the runway and applied full throttle. The feeling of accelerating and taking off on such a beautiful day was enjoyable... for about 4 seconds... I climbed to about 5 feet in the air and then, total loss of power (like lack of fuel). I was getting close to mid-runway (maybe even past it... don't remember), and I pulled the throttle, and landed the plane. The engine was still running at low rpm.
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://pages.infinit.net/mthobby
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mtherr(at)yahoo.com
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| Posted: Thu May 27, 2010 3:53 pm Post subject: Bad takeoff, but still good landing |
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Indeed that was my first impression. The symptom is exactly it. I did check the fuel flow right at the carb (disconnected the filter from the carb, put the hose towards a container and activated each fuel pump) and all was nice. I did check the float action and flow control of the float mechanism (as much as I could do it). I suspect a carburetor defect, but I'm wondering it this could be anything else.
At the parking lot, I tested the operation with my three fuel pumps and my two ignition.. none would change anything in that bad engine behavior.
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://pages.infinit.net/mthobby
--- On Thu, 5/27/10, Larry McFarland <larry(at)macsmachine.com> wrote:
| Quote: | From: Larry McFarland <larry(at)macsmachine.com>
Subject: Re: Bad takeoff, but still good landing
To: zenith601-list(at)matronics.com
Received: Thursday, May 27, 2010, 4:46 PM
--> Zenith601-List message posted
by: Larry McFarland <larry(at)macsmachine.com>
Michel,
I'd look for a fuel restriction in the line, gascolator,
filter or anywhere ahead of the carb. This doesn't sound
like an ignition, choke or spark type failure.
A fuel restriction would allow you to get full throttle
until the engine need gets ahead of the flow. Then it would
starve itself at full setting after running full out
for a short time.
Larry McFarland 601HDS at www.macsmachine.com
Michel Therrien wrote:
>
Therrien <mtherr(at)yahoo.com>
>
> Last sunday was a beautiful day here in my region and
I couldn't resist flying after completing the engine portion
of my annual inspection. I changed the oil, tested the
compression (150 +-5 on all cylinders), timing OK, removed
valve covers... all neat, cleaned air filter, etc,
etc... all was GREAT
>
> Well, I did my preflight inspection, did my
runnup (at about 3600 rpm) near runway 15 of Beloeil
airport, positioned myself on the runway and applied full
throttle. The feeling of accelerating and taking off
on such a beautiful day was enjoyable... for about 4
seconds... I climbed to about 5 feet in the air and then,
total loss of power (like lack of fuel). I was getting
close to mid-runway (maybe even past it... don't remember),
and I pulled the throttle, and landed the plane.
The engine was still running at low rpm.
> ----------------------------
> Michel Therrien CH601-HD, C-GZGQ
> http://mthobby.pcperfect.com/ch601
> http://pages.infinit.net/mthobby
>
>
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Tim Juhl
Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan
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| Posted: Thu May 27, 2010 4:22 pm Post subject: Re: Bad takeoff, but still good landing |
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Did you check that your tank vents were not plugged up? Mud dauber wasps have been known plug them up.
Tim
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Zodiac XL - Jabiru 3300A
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mtherr(at)yahoo.com
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| Posted: Thu May 27, 2010 5:21 pm Post subject: Bad takeoff, but still good landing |
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Yes, I did.. forgot to mention. Thanks Tim.
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://pages.infinit.net/mthobby
--- On Thu, 5/27/10, Tim Juhl <juhl(at)avci.net> wrote:
| Quote: | > Did you check that your tank vents were not plugged
up? Mud dauber wasps have been known plug them up.
|
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PatrickW
Joined: 27 Oct 2006
Posts: 380
Location: Fort Worth, Texas
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| Posted: Thu May 27, 2010 5:42 pm Post subject: Re: Bad takeoff, but still good landing |
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Heat source near a fuel line causing vapor lock (possibly a dislodged heat shield)?
Air leak in the intake manifold?
Hope you find the solution. Let us know what it is when you find it...
- Pat
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Thu May 27, 2010 9:18 pm Post subject: Bad takeoff, but still good landing |
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You would get similar symptoms if the air filter was clogged up or the exhaust system was partially blocked.
Do you have a fuel pressure gauge installed? A fuel pressure pickup just before the carburetor would give a valuable indication of fuel system performance.
On May 27, 2010, at 3:07 PM, Michel Therrien wrote:
| Quote: |
Well, I did my preflight inspection, did my runnup (at about 3600 rpm) near runway 15 of Beloeil airport, positioned myself on the runway and applied full throttle. The feeling of accelerating and taking off on such a beautiful day was enjoyable... for about 4 seconds... I climbed to about 5 feet in the air and then, total loss of power (like lack of fuel). I was getting close to mid-runway (maybe even past it... don't remember), and I pulled the throttle, and landed the plane. The engine was still running at low rpm.
Then I went to an area to check the engine behavior... when I raised the throttle above 4000 rpm, it would do the same thing. I then tried at lower rpms... would just take more time and at about 2100 rpm, the engine would run smooth, miss and run smooth again.
My questions: what failures could create this condition?
1. fuel system ? (I think so)
2. ignition system ?
3. cam shaft ?
4. ?
|
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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sonar1@cox.net
Joined: 02 Oct 2007
Posts: 55
Location: Santa Barbara, Ca
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| Posted: Fri May 28, 2010 8:36 am Post subject: Re: Bad takeoff, but still good landing |
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I had a forced landing with an engine that was doing the same thing. Met a really nice farmer. Problem was the fuel filter - small one from Aircraft Spruce. I would change the filter or try a bigger one, and try again....Fred N9601 (sold)
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mtherr(at)yahoo.com
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| Posted: Sat May 29, 2010 1:21 pm Post subject: Bad takeoff, but still good landing |
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Hello all,
I found the problem today. I had another Holley 5200 carb at home that I studied. I examined the fload mechanism. Then, I went back to the airport and opened the carb and this time, noticed that the movement of the float was very restrained. I then saw the issue. The floats activates a needle that seats in the bottom of a female piece. That piece was unscrewed! (see picture attached) So, the needle would seat and restrict the flow at low bowl fuel level. That was easilly repared.
I tested my engine on the ground, holding it between 4600 and 4900 rpm with no mis or anything like that.... so, I'll fly it may be tomorrow.
It is a bit frightening to see how we depend on so small things when we fly. An annual inspection would not reveal this type of problem.
Thanks all who provided ideas of what to look for.
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