We have introduced Topic Prefixes into the Classified Sections. When posting an item into any of these areas, you will notice an additional field at the top of the posting box. Please select one of the options when posting. We also request that sellers come back and edit their post once item is sold using the same field to indicate that the item is no longer available. (Click on the X in top right corner of this box to dismiss this announcement)

Failed blow-by on Cylinder 5

The Jabiru Engine which is used in many other aircraft.

Moderator: Moderators

Shaunus
Airborne from Unmanned field
Posts: 525
Joined: Wed Mar 26, 2008 1:56 pm
Closest Airfield: Morningstar
Location: Cape Town
Has thanked: 91 times
Been thanked: 109 times

Failed blow-by on Cylinder 5

Unread post by Shaunus »

Morning all

So alas my 500hr 3300 engine failed its blow-by on the 5th cylinder, reading 40/80. All others were fine, and no other issues to date. So currently getting a ring replacement at Diepkloof AMO north of Malmesbury. Anything I should be aware of anything going forward, any of you had similar issues?

Cheers
Shaun
Privileged to have flown Cubby (ZU-CYB), Jabbie (ZU-JHF), Thunderbird (ZS-WPN, ZS-VWH), Samba XL (ZU-LAR), and C172 (ZS-JIM)
User avatar
Chalkie
Too Tousand
Too Tousand
Posts: 2886
Joined: Mon Jun 02, 2008 9:19 am
Closest Airfield: FAPX
Location: Jeffreys Bay
Has thanked: 840 times
Been thanked: 1771 times

Re: Failed blow-by on Cylinder 5

Unread post by Chalkie »

If a blowbye is that low, the air can only leak past the rings, or past an inlet or exhaust valve or in the case of your engine past the cylinder head gasket. Considering you are changing piston rings this will indicate that you did remove the dipstick to confirm air leaking past the rings?
Pray, tell me Guru. What is the secret to eternal peace and contentment?
Never argue with an idiot.
OH, but I disagree!
Yes. You are right.

I would rather have scientific questions that cannot be answered; than answers that cannot be questioned.
Shaunus
Airborne from Unmanned field
Posts: 525
Joined: Wed Mar 26, 2008 1:56 pm
Closest Airfield: Morningstar
Location: Cape Town
Has thanked: 91 times
Been thanked: 109 times

Re: Failed blow-by on Cylinder 5

Unread post by Shaunus »

Chalkie wrote: Sun Oct 13, 2019 10:34 am If a blowbye is that low, the air can only leak past the rings, or past an inlet or exhaust valve or in the case of your engine past the cylinder head gasket. Considering you are changing piston rings this will indicate that you did remove the dipstick to confirm air leaking past the rings?
Hi Chalkie. Yes as far as I am aware, Pieter did confirm that the leak was via the rings using the usual listening techniques at the oil filler.

Am sure I will get a full run down from Pieter, keen to see how many other people have had to replace a ring here and there on the Jabbie and if this is a cause for concern at the 500hr mark.
Privileged to have flown Cubby (ZU-CYB), Jabbie (ZU-JHF), Thunderbird (ZS-WPN, ZS-VWH), Samba XL (ZU-LAR), and C172 (ZS-JIM)
User avatar
Chalkie
Too Tousand
Too Tousand
Posts: 2886
Joined: Mon Jun 02, 2008 9:19 am
Closest Airfield: FAPX
Location: Jeffreys Bay
Has thanked: 840 times
Been thanked: 1771 times

Re: Failed blow-by on Cylinder 5

Unread post by Chalkie »

If you over heated that cylinder the rings can be annealed and lose their tension, causing the blowby.
Pray, tell me Guru. What is the secret to eternal peace and contentment?
Never argue with an idiot.
OH, but I disagree!
Yes. You are right.

I would rather have scientific questions that cannot be answered; than answers that cannot be questioned.
User avatar
Antman
Airborne from Unmanned field
Posts: 517
Joined: Tue Aug 08, 2006 10:25 am
Closest Airfield: FARA
Location: Glen Erasmia JNB
Has thanked: 37 times
Been thanked: 62 times

Re: Failed blow-by on Cylinder 5

Unread post by Antman »

Want to learn more about piston engines, read Mike Busch’s articles and books. Very Informative!!

https://www.savvyaviation.com/home/resources/

This article is about blow-bys
https://www.savvyaviation.com/wp-conten ... ndancy.pdf

Here’s the continental SB he talks about.
https://www.aircraftspruce.com/catalog/ ... lletin.pdf
Shaunus
Airborne from Unmanned field
Posts: 525
Joined: Wed Mar 26, 2008 1:56 pm
Closest Airfield: Morningstar
Location: Cape Town
Has thanked: 91 times
Been thanked: 109 times

Re: Failed blow-by on Cylinder 5

Unread post by Shaunus »

Thanks, wish I had read that earlier!

New rings have been put in and all seems good, will monitor and see how it goes. Apparently I need to fly relatively hard for the next 3 hours for the new rings to take properly, mainly just circuits and landings.

Cheers
Shaun
Privileged to have flown Cubby (ZU-CYB), Jabbie (ZU-JHF), Thunderbird (ZS-WPN, ZS-VWH), Samba XL (ZU-LAR), and C172 (ZS-JIM)
User avatar
TOFFS
Engine full power confirmed
Posts: 180
Joined: Thu Feb 27, 2014 9:07 am
Closest Airfield: FARS
Location: Robertson
Has thanked: 17 times
Been thanked: 85 times

Re: Failed blow-by on Cylinder 5

Unread post by TOFFS »

Hi Shaun

Reading this and the comment of circuit work for initial break-in did peak my interest as the stipulated break-in procedures for type certified engines is very different and low power settings as used in the circuit are counter productive to the run-in procedure in that +75% power is called for, for a period of 2 hours. Low power settings are blamed for the varnishing of cylinders and no bedding in of the rings.

Here is an excerpt from the Jabiru Manual:

"CIRCUIT WORK is possibly a good sequence for initial run in work. Abbreviate circuits initially, step climb, climb shallow. No glide approaches. Gradually reduce power. Avoid sudden heating up and sudden cooling down."

Within the Maintenance Manual it does recommend a non-detergent oil for the break-in period.
Eric Cook
User avatar
Flooi
1k poster
1k poster
Posts: 1104
Joined: Fri Apr 20, 2012 10:29 am
Closest Airfield: Fahg
Location: Nigel
Has thanked: 103 times
Been thanked: 57 times

Re: Failed blow-by on Cylinder 5

Unread post by Flooi »

I once wrecked a newly overhauled Conti in 40 hours
because I nursed it.... so leer mens.🙄
Shaunus
Airborne from Unmanned field
Posts: 525
Joined: Wed Mar 26, 2008 1:56 pm
Closest Airfield: Morningstar
Location: Cape Town
Has thanked: 91 times
Been thanked: 109 times

Re: Failed blow-by on Cylinder 5

Unread post by Shaunus »

Have done 4 hours circuit work on the new ring, temps looking really good. Using Phillips 66 X/C Aviation SAE 20W-50 to run it in. Apparently can continue using this oil after the run in period.

Holding thumbs for a long ring life! On the side, also used the circuit work time to adjust the fixed trim tabs by shaving a bit off, biggest improved to my Jabbie in 5 years. Have posted in the J430 trimming post.

Happy flying all, and thanks for the advice to date
Cheers
Shaun
Privileged to have flown Cubby (ZU-CYB), Jabbie (ZU-JHF), Thunderbird (ZS-WPN, ZS-VWH), Samba XL (ZU-LAR), and C172 (ZS-JIM)
User avatar
JvTonder
Frequent AvComer
Posts: 666
Joined: Wed Jan 27, 2010 12:53 pm
Closest Airfield: RhinoPark
Location: Bronkhorstspruit, RhinoPark
Has thanked: 148 times
Been thanked: 24 times

Re: Failed blow-by on Cylinder 5

Unread post by JvTonder »

TOFFS wrote: Thu Oct 17, 2019 9:00 am Hi Shaun

Reading this and the comment of circuit work for initial break-in did peak my interest as the stipulated break-in procedures for type certified engines is very different and low power settings as used in the circuit are counter productive to the run-in procedure in that +75% power is called for, for a period of 2 hours. Low power settings are blamed for the varnishing of cylinders and no bedding in of the rings.

Here is an excerpt from the Jabiru Manual:

"CIRCUIT WORK is possibly a good sequence for initial run in work. Abbreviate circuits initially, step climb, climb shallow. No glide approaches. Gradually reduce power. Avoid sudden heating up and sudden cooling down."

Within the Maintenance Manual it does recommend a non-detergent oil for the break-in period.
Sorry for the Hi-Jack, TOFFS when breaking in a newly overhauled motor, Conti, for said two hours must it be flying or can it be done on the ground?

Thanks
J
Flying feeds the soul!
User avatar
TOFFS
Engine full power confirmed
Posts: 180
Joined: Thu Feb 27, 2014 9:07 am
Closest Airfield: FARS
Location: Robertson
Has thanked: 17 times
Been thanked: 85 times

Re: Failed blow-by on Cylinder 5

Unread post by TOFFS »

"Sorry for the Hi-Jack, TOFFS when breaking in a newly overhauled motor, Conti, for said two hours must it be flying or can it be done on the ground?"

Continental talk about a "Break-in" and a "Run-in"

A break-in would be conducted on the ground in a cell with a test club fitted so therefore the engine would not be installed in the airframe.

A run-in would be during a flight in accordance with the Service Bulletin relating to engine run-in's. I'm not sure of the number off the top of my head, but within it, it will give you time periods and engine settings conducted during the flight.
These users thanked the author TOFFS for the post:
JvTonder
Eric Cook

Return to “Jabiru Engines”