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stewart graham
Joined: 27 Feb 2011
Posts: 7
Location: launceston Australia
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 Posted: Sun Dec 18, 2011 1:35 pm Post subject: engine starvation |
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Ladies and gents
I have had a problem with what appears to be fuel starvation on two occasions on my M 14 in the yak 18 T
On both occasions, I was on descent, from approximately 8000 feet, into CTA. Both were relatively clear low humidity days. Prop setting moved from cruise (usually about 75% as manifold pressure is down around 650 mm at that altitude and the plane wallows a good deal making IFR tolerances difficult to maintain) down to 60%. Manifold pressure dropped to 600 mm. On the first occasion carburettor heat wasn't used on the second occasion carburettor heat was engaged at the top of dissent and was reading 50° C.
All goes well until approximately 6000 feet, and then the rpm begins to decrease, the engine note changes and we have become a glider.
On the first occasion, carburettor heat was applied, prop was moved to approximately 80%, throttle moved to approximately the position of 700 mm induction pressure, and within 5-10 seconds (although I admit it did feel longer) the engine is firing perfectly normally. On the second occasion I removed carburettor heat, adopted the same manifold and pitch positions, with the engine starting again within five seconds.
I have not seen this at any other time with this engine in the last 300+ hours of operation, including aerobatics, prolonged cruise, slowing down dramatically in the circuit to get you out, or on practised forced landings. We have not experienced the problem if the descent is actually conducted a good deal faster, with prop settings of 75%, and induction pressure at 600 mm or above of around 140- 150 kn indicated but always with the carburettor heat applied.
I am aware that some of the Dromader M18 aircraft have experienced similar situations, and will suck air through a number of connections of the fuel system, in particular passing through the firewall and priming system. We are fitted with manifold drains on the lower three cylinders, to drain being a spring-loaded mechanism as is common on most oil drains.
Has anyone any thoughts
Dr Stewart Graham MBBS FRACP Consultant Rheumatologist
Prov No. 462449A ABN-79105443463
Main Office: Suite1, 7 High St. Launceston, Tas 7250.
Clinics: Queenstown, King island, Burnie & Devonport
Email: srgrheumatology(at)bigpond.com Ph: 0363348631 Fax: 0363348547
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brian(at)lloyd.com
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| Posted: Sun Dec 18, 2011 1:47 pm Post subject: engine starvation |
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On Sun, Dec 18, 2011 at 1:32 PM, SRGraham <sgyak18t(at)bigpond.com (sgyak18t(at)bigpond.com)> wrote:
| Quote: |
Ladies and gents
I have had a problem with what appears to be fuel starvation on two occasions on my M 14 in the yak 18 T
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In your narrative you did not mention fuel pressure indication. Was it normal? If you had normal fuel pressure readings and no fluctuations (indicative of vapor in the fuel system) then I would be looking downstream of the fuel pressure sensor, i.e. at the carburetor itself.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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javiercarrascob
Joined: 06 Sep 2009
Posts: 62
Location: Virginia
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| Posted: Sun Dec 18, 2011 9:34 pm Post subject: engine starvation |
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Hello Stewart, just my 2 cents.
I had an issue similar to that, After descending from 6.000 to 2.000 I can hear the engine surge and then go back to normal.
One thing keep your engine temps close to 180 C and not lower on decent by closing the shutters.
Also I had the Autoplug convertion installed and never had this issue again, but also going back to the temp, one of the Russian Gurus told me that that might had been the issue, leting the engine cool down too much.
Hope that helps.
Javier Carrasco
Yak-55m
--- On Sun, 12/18/11, SRGraham <sgyak18t(at)bigpond.com> wrote:
| Quote: |
From: SRGraham <sgyak18t(at)bigpond.com>
Subject: engine starvation
To: yak-list(at)matronics.com
Date: Sunday, December 18, 2011, 4:32 PM
Ladies and gents
I have had a problem with what appears to be fuel starvation on two occasions on my M 14 in the yak 18 T
On both occasions, I was on descent, from approximately 8000 feet, into CTA. Both were relatively clear low humidity days. Prop setting moved from cruise (usually about 75% as manifold pressure is down around 650 mm at that altitude and the plane wallows a good deal making IFR tolerances difficult to maintain) down to 60%. Manifold pressure dropped to 600 mm. On the first occasion carburettor heat wasn't used on the second occasion carburettor heat was engaged at the top of dissent and was reading 50° C.
All goes well until approximately 6000 feet, and then the rpm begins to decrease, the engine note changes and we have become a glider.
On the first occasion, carburettor heat was applied, prop was moved to approximately 80%, throttle moved to approximately the position of 700 mm induction pressure, and within 5-10 seconds (although I admit it did feel longer) the engine is firing perfectly normally. On the second occasion I removed carburettor heat, adopted the same manifold and pitch positions, with the engine starting again within five seconds.
I have not seen this at any other time with this engine in the last 300+ hours of operation, including aerobatics, prolonged cruise, slowing down dramatically in the circuit to get you out, or on practised forced landings. We have not experienced the problem if the descent is actually conducted a good deal faster, with prop settings of 75%, and induction pressure at 600 mm or above of around 140- 150 kn indicated but always with the carburettor heat applied.
I am aware that some of the Dromader M18 aircraft have experienced similar situations, and will suck air through a number of connections of the fuel system, in particular passing through the firewall and priming system. We are fitted with manifold drains on the lower three cylinders, to drain being a spring-loaded mechanism as is common on most oil drains.
Has anyone any thoughts
Dr Stewart Graham MBBS FRACP Consultant Rheumatologist
Prov No. 462449A ABN-79105443463
Main Office: Suite1, 7 High St. Launceston, Tas 7250.
Clinics: Queenstown, King island, Burnie & Devonport
Email: srgrheumatology(at)bigpond.com Ph: 0363348631 Fax: 0363348547
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