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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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 Posted: Mon Apr 04, 2016 2:53 am Post subject: High CHTs HS6A - on one mag |
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IAS 95 knots, 680mm 2000rpm OAT 10°C. With both magnetos selected CHT (of No4 Cyl front cockpit gauge) stabilises a bit over 200°C.
This alone is usually hot for an HS6A under these conditions - based on experience from flying many other CJs
Switch to Mag No2, minimal amount of change in anything, slightly rougher, but hardly perceptible. Switch to No1 Mag, a definitely rougher but CHT drop, instantly and rapidly! After very short period (30-40 seconds) the CHT is around 165°C. A value that is in line with what is normally seen under these conditions.
The same trend is shown on the rear cockpit CHT gauge - even though absolute values are about 20°C lower overall.
Witch mags back to both and boom! CHT rises very quickly back up.
So what is happening!?
Is No2 Mag auto advancing to some crazy value? Maybe a broken spring, or advance stop out of adjustment? Showing my complete lack of knowledge of the inner workings of the CD5 now...
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dsavarese0812(at)bellsout
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| Posted: Mon Apr 04, 2016 3:17 am Post subject: High CHTs HS6A - on one mag |
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Did you check the mag timing?
Although this may be far fetched, I'm thinking ...... the CHT probe is installed on a rear plug. When you switch to #1 Mag, that is the left mag which fires only the front plugs. You mentioned when you switched to #1 mag, it was definitely rougher. Maybe the front spark plug on the cylinder with the CHT probe (some are on the rear plug on the Huosai engine) is fouled or causing the rougher running. Try swapping the front and rear plugs on the cylinder with the CHT probe. Then go fly the airplane and see if the symptom you've described follows the plug change.
Dennis
From: JL2A <info(at)flyingwarbirds.com.au>
To: yak-list(at)matronics.com
Sent: Monday, April 4, 2016 6:53 AM
Subject: High CHTs HS6A - on one mag
--> Yak-List message posted by: "JL2A" <info(at)flyingwarbirds.com.au (info(at)flyingwarbirds.com.au)>
IAS 95 knots, 680mm 2000rpm OAT 10°C. With both magnetos selected CHT (of No4 Cyl front cockpit gauge) stabilises a bit over 200°C.
This alone is usually hot for an HS6A under these conditions - based on experience from flying many other CJs
Switch to Mag No2, minimal amount of change in anything, slightly rougher, but hardly perceptible. Switch to No1 Mag, a definitely rougher but CHT drop, instantly and rapidly! After very short period (30-40 seconds) the CHT is around 165°C. A value that is in line with what is normally seen under these conditions.
The same trend is shown on the rear cockpit CHT gauge - even though absolute values are about 20°C lower overall.
Witch mags back to both and boom! CHT rises very quickly back up.
So what is happening!?
Is No2 Mag auto advancing to some crazy value? Maybe a broken spring, or advance stop out of adjustment? Showing my complete lack of knowledge of the inner workings of the CD5 now...
Read this topic online here:
http://forums.matronics.com/viewtopic.p://www.matronics.com/contribution" target="_blank">http://www.matronics.cbsp; -Matt Dralle, List Adp; --> http://forums.matronics.comhttp://www.matronics.com/contribution</a=============
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Mon Apr 04, 2016 5:43 pm Post subject: High CHTs HS6A - on one mag |
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Check your mag timing.
Doc
Sent from my iPad
| Quote: | On Apr 4, 2016, at 5:53 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:
IAS 95 knots, 680mm 2000rpm OAT 10°C. With both magnetos selected CHT (of No4 Cyl front cockpit gauge) stabilises a bit over 200°C.
This alone is usually hot for an HS6A under these conditions - based on experience from flying many other CJs
Switch to Mag No2, minimal amount of change in anything, slightly rougher, but hardly perceptible. Switch to No1 Mag, a definitely rougher but CHT drop, instantly and rapidly! After very short period (30-40 seconds) the CHT is around 165°C. A value that is in line with what is normally seen under these conditions.
The same trend is shown on the rear cockpit CHT gauge - even though absolute values are about 20°C lower overall.
Witch mags back to both and boom! CHT rises very quickly back up.
So what is happening!?
Is No2 Mag auto advancing to some crazy value? Maybe a broken spring, or advance stop out of adjustment? Showing my complete lack of knowledge of the inner workings of the CD5 now...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=454520#454520
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Tue Apr 05, 2016 6:29 pm Post subject: Re: High CHTs HS6A - on one mag |
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checked timing, left mag was 2.5° BTDC the RH 3.5° BTDC! They are 24° mags.
Yikes
I think you have probably pointed the finger at the most likely explanation of the CHT drop.
Obviously this is a grossly mistimed engine, but to me in the direction of lower CHTs??? (too retarded)
Cheers
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Last edited by JL2A on Tue Apr 12, 2016 3:37 am; edited 1 time in total |
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Tue Apr 05, 2016 7:14 pm Post subject: High CHTs HS6A - on one mag |
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👍
Doc
Sent from my iPad
| Quote: | On Apr 5, 2016, at 9:29 PM, JL2A <info(at)flyingwarbirds.com.au> wrote:
checked timing, left mag was 2.5°C BTDC the RH 3.5°C BTDC! They are 24° mags.
Yikes
I think you have probably pointed the finger at the most likely explanation of the CHT drop.
Cheers
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=454594#454594
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wlannon(at)shaw.ca
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| Posted: Tue Apr 05, 2016 8:52 pm Post subject: High CHTs HS6A - on one mag |
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The numbers you have given for the ignition angle are not correct.
They are also corrupted by what appears to be a computer glitch. I am
referring to the "A(with an accent above) and the C with degree mark. I
note the A is also repeated in "they are 24 deg. mags." but not the C.
If the "C" is not an error I would interpret that to mean the angles you
have given are relative to the crankshaft. If that is the case they are so
far out I doubt the engine would run. If that is an error and you are
referring to the propellor shaft angle they are still far out of tolerance.
Please advise.
Rather than give you the numbers from memory I will confirm at the hangar
tomorrow and get back to you.
Walt
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dsavarese0812(at)bellsout
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| Posted: Wed Apr 06, 2016 2:51 am Post subject: High CHTs HS6A - on one mag |
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I agree with you 100% Walt.
Dennis
From: Walter Lannon <wlannon(at)shaw.ca>
To: yak-list(at)matronics.com
Sent: Wednesday, April 6, 2016 12:51 AM
Subject: Re: Re: High CHTs HS6A - on one mag
--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
The numbers you have given for the ignition angle are not correct.
They are also corrupted by what appears to be a computer glitch. I am
referring to the "A(with an accent above) and the C with degree mark. I
note the A is also repeated in "they are 24 deg. mags." but not the C.
If the "C" is not an error I would interpret that to mean the angles you
have given are relative to the crankshaft. If that is the case they are so
far out I doubt the engine would run. If that is an error and you are
referring to the propellor shaft angle they are still far out of tolerance.
Please advise.
Rather than give you the numbers from memory I will confirm at the hangar
tomorrow and get back to you.
Walt
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Wed Apr 06, 2016 3:18 pm Post subject: Re: High CHTs HS6A - on one mag |
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They are degrees propeller angle! miles out I know, I have recommended the owner get his normal shop to reset the timing also find Tdc properly as I only used quick n nasty method - but repeated 4 times as I thought it was I that was surely wrong! Even with a +\-2 degree margin of error finding tdc they are still out. Also noticed both mags were against their adjustment stops advanced - ie could not advance any more without re doing the coupling adjust. Suspect someone thought it was near enough or best they could do when timing was last checked. Or I can't find tdc for nuts
Still the fact remains this engine running about 20°C hotter than any installation I have flown behind. We put a independent thermocouple in one of the cooling fins of number four cylinder and found the cockpit gauge reads around 15°C more, but then this would probably be found if you put a thermocouple on any other engine two (a result of having the thermocouple under the spark plug as eluded to earlier)
Cheers all!
PS – is there any way of checking dynamic timing of these engines with strobes etc?
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wlannon(at)shaw.ca
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| Posted: Thu Apr 07, 2016 7:50 pm Post subject: High CHTs HS6A - on one mag |
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I'm sure you have the TDC just fine.
Sounds like the couplings are the problem. But; Could it be that the
points have been filed, or otherwise screwed up, enough to drastically
change the timing??
Not very likely! Maybe the mags came from a different engine and never had
a coupling adjustment?
Walt
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