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Rschultz5(at)houston.rr.c
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 Posted: Wed Aug 02, 2006 6:59 pm Post subject: Oshkosh by air - return by Avis |
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I am looking for ideas on a recurring engine problem that caused me 3 precautionary landings on the way from Oshkosh last weekend. The typical setting was after an hour to hour and a half of cruise flight time the engine would drop RPM and feel like it was ready to quit. Moving the throttle forward made it worse and pulling it back made it better. The first hint of a problem was on landing at Green Bay after coming up from Texas. The engine ran at reduced power as soon as I came off the throttle to start the decent for landing from 6500 feet. The initial thought was the problem came from the longer idle coming down and fouling the plugs. A change of the plugs and the engine ran on the ground for 20 minutes going in to and out of full turbo power without a hitch. The plane was then flown for an hour to Oshkosh and for an additional hour during the week both at low level (2500’) the return trip started out great and at 6500’ and about an hour in to the flight again the engine lost power. I tried the throttle settings and again moving up was bad down was good. I tried both fuel pumps on and each alone, I tried both sets of plugs alone and together with no change in the engine response at cruise range. Another landing and calls to Lockwood for advice. They had me inspect the filters with were just replaced prior to the trip and clean, Next I opened the fuel pressure regulator to check for dirt, nothing clean as the day it was built. I next check the carbs to see of they were free floating and they were no lead build up. I then was told to report the needle valve richer to see if that would help. Run up on the ground for 20 minutes showed no signs of problems. Next morning (Sunday) run up on the ground looked good. Climbed up to 6500 over the airport and hung out doing circles for about half an hour using the full range of throttle settings. After the half hour set 5000 RPM and 30 inches and off I went. 30 minutes latter the same old problem was back. I again made a precautionary landing in Iowa. Having had all the fun I cold have and no new ideas the plan was left to think about its behavior and drove home. I am taking my trailer up to embarrass the plane in from of its new friends and pull the wings and bring it back to Houston this weekend. Dose anyone have a thought on why this is happening after a hour or more at cruise power? Flight up was 12 hours with no problems and it just came on very sudden. I have been burning a combination of avgas and mogas with the trip up being all avgas. Fuel pumps were tested the week before the flight (at) 20 gallons an hour for each pump.
Comments anyone with a 914 having similar problems?
Aircraft has 95 hours. 914 with an intercooler, AirMaster prop
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rparigor(at)suffolk.lib.n
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| Posted: Wed Aug 02, 2006 9:10 pm Post subject: Oshkosh by air - return by Avis |
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Hello Richard
"Comments anyone with a 914 having similar problems"
I am not yet flying my 914, but have a pretty good in site.
Do you have a Differential pressure gauge? Was it less than 2 pounds?
If you don't have one, why not?
Was your EGT high? Running out of gas will create a lean mixture and show
high on EGT.
What fuel schematic you using? Parallel or series with bypass?
What type of filters you using and where are they placed? If Parallel do
you have a filter at the inlet of each pump? If series with bypass is 1
filter on inlet of pump 1 and the other at the inlet of checkvalve where
it can only supply pump 2.
It sounds like you are running out of gas. The very first think to check
is make sure the vent on your fuel tank is allowing air to get into tank.
If air can't get into tank, after a while fuel will not be able to get
out.
See:
http://www.sarangan.org/europa_forum/2005-10/index.html
Search: Rob Neils Ron
Do you have any gasculators? If so is it a Mini Andair? Did you clean the
gasculator filters?
Have you ever run for any reason with no filter going to the fuel pumps?
There are filter socks in the inlet of the pumps that could be clogged.
Very careful inspect all the vacuum/pressure hoses on the 914, especial to
one supplying the diaphragm of the fuel pressure regulator, and the hoses
going from airbox to solenoid valve, and from the solenoid valve to the
float bowls of the carbs. A crack, leak or restriction will do no good for
proper running. These are critical on a 914.
Check for kinked or restricting hoses from outlet of tank all the way to
engine.
Did you try reserve? I heard that 1 guy in England had animal hair sneak
past the snake catcher filter on tank outlet, and became a sort of spider
web that collected debris and clogged outlet, so could be outlet of tank
clogged.
You mention you saw 20GPH on each pump. I suspect the test you did was
useless. Read on Rotax service manual how to test flow of pumps. You want
to make sure not only the pump has an OK flow rate, but bottom line is you
need to be able to persuade the fuel pressure regulator to overcome 115%
airbox pressure, that takes flow and pressure. Worst case is at altitude
where pumps need to make more pressure over ambient to net 2 to 5 pounds
over airbox pressure.
I recent posted how to obtain manuals and how to update them.
Good Luck.
Let us know resolve.
Sincerely
Ron Parigoris
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ptag.dev(at)tiscali.co.uk
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| Posted: Wed Aug 02, 2006 10:00 pm Post subject: Oshkosh by air - return by Avis |
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Hi! Richard
I don’t know about 914’s…yet but have you thought about Ice possibility ? You didn’t mention about use of carb heat on decent?
Regards
Bob Harrison G-PTAG
Robt.C.Harrison
-----Original Message-----
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Richard Schultz
Sent: 03 August 2006 03:54
To: europa-list(at)matronics.com
Subject: Oshkosh by air - return by Avis
I am looking for ideas on a recurring engine problem that caused me 3 precautionary landings on the way from Oshkosh last weekend. The typical setting was after an hour to hour and a half of cruise flight time the engine would drop RPM and feel like it was ready to quit. Moving the throttle forward made it worse and pulling it back made it better. The first hint of a problem was on landing at Green Bay after coming up from Texas. The engine ran at reduced power as soon as I came off the throttle to start the decent for landing from 6500 feet. The initial thought was the problem came from the longer idle coming down and fouling the plugs. A change of the plugs and the engine ran on the ground for 20 minutes going in to and out of full turbo power without a hitch. The plane was then flown for an hour to Oshkosh and for an additional hour during the week both at low level (2500’) the return trip started out great and at 6500’ and about an hour in to the flight again the engine lost power. I tried the throttle settings and again moving up was bad down was good. I tried both fuel pumps on and each alone, I tried both sets of plugs alone and together with no change in the engine response at cruise range. Another landing and calls to Lockwood for advice. They had me inspect the filters with were just replaced prior to the trip and clean, Next I opened the fuel pressure regulator to check for dirt, nothing clean as the day it was built. I next check the carbs to see of they were free floating and they were no lead build up. I then was told to report the needle valve richer to see if that would help. Run up on the ground for 20 minutes showed no signs of problems. Next morning (Sunday) run up on the ground looked good. Climbed up to 6500 over the airport and hung out doing circles for about half an hour using the full range of throttle settings. After the half hour set 5000 RPM and 30 inches and off I went. 30 minutes latter the same old problem was back. I again made a precautionary landing in Iowa. Having had all the fun I cold have and no new ideas the plan was left to think about its behavior and drove home. I am taking my trailer up to embarrass the plane in from of its new friends and pull the wings and bring it back to Houston this weekend. Dose anyone have a thought on why this is happening after a hour or more at cruise power? Flight up was 12 hours with no problems and it just came on very sudden. I have been burning a combination of avgas and mogas with the trip up being all avgas. Fuel pumps were tested the week before the flight (at) 20 gallons an hour for each pump.
Comments anyone with a 914 having similar problems?
Aircraft has 95 hours. 914 with an intercooler, AirMaster prop
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Dave Miller
Joined: 10 Jan 2006
Posts: 51
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| Posted: Thu Aug 03, 2006 7:03 am Post subject: Oshkosh by air - return by Avis |
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Hi Richard,
Something similar happened while I was in a friends 914 mono.
The turbo boost dropped and we lost power. Reducing power improved things, as the prop went to fine with the reduced throttle setting.
The problem was the cabin heat system, taking heat off the muffler, was dumping hot air near the air intake, when not directing it to the cockpit.
The computer in the turbo system ( I think ) sensed that things were too hot and cut back the boost.
Re routing the hot air to the canopy vent cured the problem.
Just an idea, may not have any relevance to your problem
Dave A061
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rparigor(at)suffolk.lib.n
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| Posted: Thu Aug 03, 2006 10:58 pm Post subject: Oshkosh by air - return by Avis |
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Hello Richard
I had a few more easy to check thoughts today about your power loss:
Check to see if your carb to manifold rubber boots are leaking. If you
don't have Kevlar reinforced, very good idea to replace them. Read
bulletin on how far you can tighten boots, better yet if you don't have
new style clamps with built in stops, get some.
Did you satisfy the recent bulletin to change carb float pivot pins?
Ron Parigoris
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SPurpura(at)aol.com
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| Posted: Fri Aug 04, 2006 5:45 pm Post subject: Oshkosh by air - return by Avis |
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Sounds like vapor lock, how well are yor fuel lines insulated? I had a similar problem with my 914 and wrapping the fuel lines was the fix.
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robust_design(at)hotmail.
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| Posted: Tue Aug 08, 2006 10:55 am Post subject: Oshkosh by air - return by Avis |
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Richard,
I don't know if my emails get beyond my computer,0 but here goes:
Ignition could be the problem. It takes0 higher voltage to arc across higher pressure fuel mix.
If the ignition coil or distributor cap or rotor or0 wires have conductive "dirt" on them, the spark may jump along the short circuit0 rather than through the spark plug.
In a borderline situation, a higher throttle0 setting increases the combustion pressure enough to force the voltage to a0 higher level before arcing, and the higher voltage causes the current to take a0 short circuit across the deteriorated surface of the distributor cap,0 etc.
Reducing the throttle reduces the plug gap voltage0 required, and the engine runs normally.
Now why this should occur 1 1/2 hrs into cruise, or0 at higher altitudes, I can not guess. Heat distribution? 0
Your troubleshooting has eliminated the likelyhood0 of it being a pump or plug problem.
I have no experience with the Rotax, but in a0 different engine, I'd replace the distributor cap and rotor.
Donald Ingram
xs mono
[quote] ---
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