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dsavarese0812(at)bellsout
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 Posted: Mon Sep 11, 2017 3:32 am Post subject: Low Pass Engine Sputter |
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I suggest possible carburetor icing. Most of us never consider that possibility. But it CAN happen even though the window for carb icing with a pressure carb is very small. Ironically, having experienced the same symptom twice doing a low pass/fly-by with hard pitch up, I could not find a single problem with the engine each time.
Dennis
From: HÃ¥vard Dale <yaknorway52(at)gmail.com>
To: yak-list(at)matronics.com
Sent: Monday, September 11, 2017 6:21 AM
Subject: Re: Low Pass Engine Sputter
Hi,
Interesting subject as on my last display with my Yak 50 had the same experience. Was to fly a Display to celebrate opening of a new Museum at an old abandoned WW II German Airstrip here in Norway. After take-off from my base its only 10 minutes flight time to where the display took place. After take-off I kept Aerobatic power setting and all the way. Display started and lasted 10-12 min. On the last "low-pass" 400+ km/t and 200 feet the engine made a, in my opinion Misfire. I pulled up and gained 1500 feet to sort the shit out. As I like to see out the cockpit on low passes I did,t see on the fuel pressure gauges when the "misfired" happened. Did that on the climb out and all gauges where Normal. Can't remember my Cylinder temp, but I am sure it was in the green arc, the Gills was fully open and around 10c' outside temp. I circled overhead the old German Airstrip and prepared an emergency landing if the engine went quiet. It did run stable, but a little rough so I sat course back home and landed safely. Back at base I did a leak check on all cylinders, checked for leaks on fuel system, checked all filters, Have not checked fuel vent yet(shall do that) Since the ignition system is original I have decide to replace with Auto Ignition Kit, and new magnetos. For the moment I suspect the ignition to be my source of wake up during the low-pass:-)
Kind Regards
Havard
Norway
2017-09-09 0:38 GMT+02:00 Adrian Hale <coolade2(at)gmail.com (coolade2(at)gmail.com)>:
[quote]--> Yak-List message posted by: Adrian Hale <coolade2(at)gmail.com (coolade2(at)gmail.com)>
My Yaks never did this but my good friend had the exact problem you describe we were told that 25w60 would cause it-- made no sense to me as an engineer but we went back to shell 120 and the problem went away.
Sent from my iPad
> On Sep 8, 2017, at 12:32 PM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:
>
> --> Yak-List message posted by: "Bitterlich, Mark G CIV NAVAIR, WD" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
>
> Oh darn. I'm sorry. The message was from Bill Geipel. Disregard.
>
> --
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bmsim
Joined: 02 Jun 2009
Posts: 32
Location: Alabama
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| Posted: Mon Sep 11, 2017 4:37 am Post subject: Re: Low Pass Engine Sputter |
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Update:
Flew several hours this weekend, no low approaches, and she ran like a top. After doing a good bit of pattern work to make certain things were stable, I took her up and put her through the paces - she was very happy about it and purred along like she should.
Thanks to all that offered suggestions, I'm looking into all of them:
1. Possible icing
2. Oil
3. Sticking valve (add Mystery Oil)
I'll post updates as I have them, but with this hurricane coming in I'm afraid it may be a bit!
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romaine_richard(at)yahoo.
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| Posted: Tue Sep 12, 2017 4:19 am Post subject: Low Pass Engine Sputter |
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Is there something in that a diving entry, low pass is a longer max inlet pressure (high dynamic ram and ambient pressure), high load event than the aerobatics?
Something that can tolerate a transient but not the sustained pass followed by a pull up?
In the humid DC area, my carb icing has been worst on climbout after running too long on ground...have seen the condensation on the carb after immediate return and shutdown.
Rich
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