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Allegro 2000, 912UL Initial Engine Test Run

 
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hgmckay



Joined: 23 May 2006
Posts: 397

PostPosted: Sat Sep 02, 2006 2:32 pm    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Gentlemen: Today I ran my Rotax 912UL for its first test run. The plane is an Allegro 2000. Plane was anchored down, outside temperature 86 to 88 degrees F, bright and sunny, plane sitting on asphalt.
<![if !supportEmptyParas]> <![endif]>
Here is the chronology of the results.
<![if !supportEmptyParas]> <![endif]>
  1. Oil system was vented properly.
  2. Oil level checked. OK (Mobile 1 MX4T 10w-40 motorcycle oil)
  3. Coolant level OK. (50/50 distilled water and Texaco Anti-freeze Coolant Concentrate)
  4. Started electric fuel pump.
  5. Closed choke, (full choke)
  6. Throttle in idle position.
  7. Master switch on.
  8. Ignition switches (2) on.
  9. Started engine (engine started immediately).
  10. Held engine rpm at 1000 for 5 min.
  11. Oil pressure went to 5 bar on start.
  12. After 5 min increased rpm to 2500
  13. At 2500 rpm, oil pressure 4.0 bar, oil temp. 60 degrees C, cylinder head temp. 100 degrees C, fuel pressure 0.3 bar (held this rpm for 10 to 15 min.) I noticed the cylinder head temp gradually continued to rise.
  14. After 15 min gradually increased rpm to 4000
  15. At 4000 rpm; Oil pressure 4.0 bar, oil temp. increased to 120 degrees C, cylinder head temp increased to 130 degrees C, fuel pressure 0.3 bar (held this rpm for another 15 +/- min.)
  16. At 4000 rpm checked both ignition (kill) switches. rpm drop was aprx. 100 rpm on each switch.
  17. At this point the engine had been running for about 30 to 40 minutes sitting on the ground with the cowling on and the ambient temp. at aprx.88 degrees F.
  18. I then increased the engine speed to max throttle position and checked the engine rpm. Max rpm was 4600 rpm. Held this speed for one minute. Based on this number the existing Prop pitch (17.5 degrees by the Warp Drive Protractor) needs adjusting to get the rpm up to the 4800-5100 range. I assume I will have to reduce the pitch to do this (i.e. less pitch equals higher rpm). How much less than 17.5 degrees I don’t know. I’m guessing about 1 to 1.5 degrees.
  19. At max throttle, 4600 rpm; oil pressure 3.4 bar, oil temp. 120 degrees C, cylinder head temp 130 degrees C and rising, fuel pressure 0.3 bar.
  20. Reduced engine speed to 1000 rpm for 3 min. for cool down.
  21. Engine stopped.

<![if !supportEmptyParas]> <![endif]>
Note: After engine shut down coolant in over flow bottle was boiling, and there was evidence of overflow on the asphalt. I noticed that the specs on the Texaco Anti-freeze coolant container showed that for a 50/50 mix ratio and a 15 psi radiator cap (my cap is rated 1.2 bar or 17.2 psi), the boil over protection is only 129.3 degree C. For a 60/40 mix ratio the protection goes up only to 132.2 degrees C. This is the max. recommended mix ratio. If the CHT gauge is correct I exceeded the boil over protection for the mixture.
<![if !supportEmptyParas]> <![endif]>
The Rotax Engine Operators Manual 10.2.1 states that the ratio of anti-freeze to water should be increased if boiling should occur. I can only go to a 60/40 and that only protects to 132.2 degrees C.
One thing that concerned me when I filled the engine cooling system, it took less than one gallon (aprx. 3 quarts) of 50/50 mix to fill the system. This seems to me to be a very small amount of liquid to cool the engine properly. What is the proper volume of coolant in the Allegro 2000 cooling system?
<![if !supportEmptyParas]> <![endif]>
Everything seemed to be normal except the CHT. Can any one help me with this problem?
<![if !supportEmptyParas]> <![endif]>
Hugh McKay in North Carolina
[quote][b]


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Gilles.Thesee(at)ac-greno
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PostPosted: Sat Sep 02, 2006 3:12 pm    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hi Hugh,

Quote:
Gentlemen: Today I ran my Rotax 912UL for its first test run.....

1. Started engine (engine started immediately).
2. Held engine rpm at 1000 for 5 min.
3. Oil pressure went to 5 bar on start.
4. After 5 min increased rpm to 2500
5. At 2500 rpm, oil pressure 4.0 bar, oil temp. 60 degrees C,
cylinder head temp. 100 degrees C, fuel pressure 0.3 bar (held
this rpm for 10 to 15 min.) I noticed the cylinder head temp
gradually continued to rise.


I would have shut down long before that.

Quote:
1. After 15 min gradually increased rpm to 4000
2. At 4000 rpm; Oil pressure 4.0 bar, oil temp. increased to 120
degrees C, cylinder head temp increased to 130 degrees C, fuel
pressure 0.3 bar (held this rpm for another 15 +/- min.)
3. At 4000 rpm checked both ignition (kill) switches. rpm drop was
aprx. 100 rpm on each switch.
4. At this point the engine had been running for about 30 to 40
minutes sitting on the ground with the cowling on and the
ambient temp. at aprx.88 degrees F.
5. I then increased the engine speed to max throttle position and
checked the engine rpm. Max rpm was 4600 rpm. Held this speed
for one minute. Based on this number the existing Prop pitch
(17.5 degrees by the Warp Drive Protractor) needs adjusting to
get the rpm up to the 4800-5100 range. I assume I will have to
reduce the pitch to do this (i.e. less pitch equals higher rpm).
How much less than 17.5 degrees I don’t know. I’m guessing about
1 to 1.5 degrees.
6. At max throttle, 4600 rpm; oil pressure 3.4 bar, oil temp. 120
degrees C, cylinder head temp 130 degrees C and rising, fuel
pressure 0.3 bar.
7. Reduced engine speed to 1000 rpm for 3 min. for cool down.


IMHO, 40 minutes on the ground seems quite an ordeal for a first engine
run. Especially with the temperatures you achieved. 130°C seems to me
way too high.
One thing common to any piston engine, is they need to be treated with
care at the beginning of their operating life. And you don't want to
thermally load them during the run in period.

If it were my engine, I'd do short runs progressively increased in RPM
and duration, with a careful monitoring of temperatures. And I would
stop as soon as they climb too high. Adequate airflow is key.
When building a 4-seater project, I conducted a thorough cooling
investigation, and designed a radiator duct which performs very well,
with great ease of adjustment.
See :
http://contrails.free.fr/engine_refroid.php
http://contrails.free.fr/tunnel_en.php
Quote:

1.
Note: After engine shut down coolant in over flow bottle was boiling,
and there was evidence of overflow on the asphalt.

This is no surprise.

First start, run 30 seconds, shut down, check everything.
Then resart for a few minutes, without allowing the temps to exceed the
lower authorized range, shut down, check, etc...

Quote:
I noticed that the specs on the Texaco Anti-freeze coolant container
showed that for a 50/50 mix ratio and a 15 psi radiator cap (my cap is
rated 1.2 bar or 17.2 psi), the boil over protection is only 129.3
degree C. For a 60/40 mix ratio the protection goes up only to 132.2
degrees C. This is the max. recommended mix ratio. If the CHT gauge is
correct I exceeded the boil over protection for the mixture.


It's not the boiling that harms the engine, but high CHT. To the
contrary, boiling helps reducing temps, that is as long as there is
coolant to boil, and not for 40 minutes. You definitely need cooling
airflow to correctly reject heat from the engine.
Quote:

The Rotax Engine Operators Manual 10.2.1 states that the ratio of
anti-freeze to water should be increased if boiling should occur. I
can only go to a 60/40 and that only protects to 132.2 degrees C.

One thing that concerned me when I filled the engine cooling system,
it took less than one gallon (aprx. 3 quarts) of 50/50 mix to fill the
system. This seems to me to be a very small amount of liquid to cool
the engine properly. What is the proper volume of coolant in the
Allegro 2000 cooling system?

Everything seemed to be normal except the CHT. Can any one help me
with this problem?

The Rotax 91X series are very enduring engines, so you may hope you did

not really damage your engine.
I would suggest you start again the right way :

- Download the applicable cooling SBs and service letters from the Rotax
website and read them thoroughly.
- Seek the advice of a knowledgeable Rotax mechanic, engineer or dealer.
- Check for adequate engine and radiator installation.
- Do not do long ground runs with no cooling.

Best of luck,
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr


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hgmckay



Joined: 23 May 2006
Posts: 397

PostPosted: Sun Sep 03, 2006 4:05 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Gilles: The times stated in my email are excessive. After reviewing the
actual sequence of events I shut down the engine after the CHT was
approaching 130 degrees C. It took about 15 min to reach the 130 degrees. I
did not hold the engine at 130 degrees for any length of time. I believe the
problem was that I was not moving (static) and the ambient temp. was about
88 degrees F. The air flow across the engine was only what the cowling
allowed. Has any one else experienced this high CHT while sitting on the
ground with the engine running for about 15 min.?

Hugh

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Thom Riddle



Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

PostPosted: Sun Sep 03, 2006 5:27 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hugh,

Though they do have a very explicit run-in procedure for their 2-stroke
engines, Rotax does not require a run-in sequence for the 912 series
engines. Maintaining all parameters within normal ranges is important
though, especially while the engine is new. You allowed the oil
temperature to get above the normal range (90-110C) but kept it below
the max of 140C so I would not be too concerned about that. There is no
normal range specified for the CHT and you kept it below the 150C max.
Again no real concern. Oil pressure was maintained in normal range. No
concern there either. Note the temperature limits are different for the
912ULS engines.

Your report was very thorough with the exception of what the
temperatures were when you shut down the engine. You stated that you
let the engine cool down for 3 minutes but did not mention what the
temps were when you shut it down. In normal operation of our Allegro
2000 912UL, the engine has had plenty time to cool off for shutdown
after final approach and landing at idle, taxiing off the runway and
taxiing to hangar. If you don't let the engine cool down properly, then
the overflow coolant at ambient pressure would be expected to boil. On
static runs I would do the cool down at 2,000 rpm until the oil
temperature dropped into the low end of normal range before shutting
down. As I said, in normal operations, we've never had to let ours cool
down after taxiing to the hangar.

Rotax recommends letting the engine cool down at 2,000 rpm before
shutting it down, not 1,000 rpm. 1,000 rpm is too slow for this engine
and idle should be set to 1400 rpm minimum to 1800 max. Note that the
idle speed must be set when the engine is at normal operating
temperatures. If done at cooler temps, it will change when warmed up to
normal temps. Extended idling at too low rpm on the 912 can cause
gearbox damage. Since the Allegro glides so well, you will find that
setting the idle at the low end of the 1400-1800 rpm range is best. If
you set it at the high range, you will have trouble keeping the
airspeeds down on final approach.

We have not changed our coolant yet so I don't know what the total
system capacity is, but I suspect it is not very much. Remember, this
is not a big engine (1.2 liters) and the cooling system is pretty
compact.

I would decrease the prop pitch by no more than 1 degree for first
change. You may be surprised how much rpm difference 1/2 degree can
make. The range you are looking for (4800-5100 rpm) static is good for
the Allegro. Ours runs about 4900 rpm static and yields best cruise
speeds at this pitch. 5100 rpm static would give better climb.

Thom Riddle
FAA Powerplant Mechanic
Allegro 2000 #03-202


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PostPosted: Sun Sep 03, 2006 5:45 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

These are very good informations. Thanks Thom for posting them.

Jean-Paul
do not archive
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PostPosted: Sun Sep 03, 2006 7:34 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hugh and Thom,

The following update re cooling may be of interest.
Quote:

There is no normal range specified for the CHT and you kept it below
the 150C max.

Rotax 912 operator's manual does specifiy a normal CHT range of
75-110°C with a red mark at 135°C/150°C for the hottest cylinder (to be
determined by tests) IF you switch to Evans water-free coolant.
If you stick to the 50/50 coolant, your CHT redlines is 120°C with the
1.2 bar cap and only 115°C with the old 0.9 bar cap.
The normal oil temp range is 90-110°C.

I would strongly advise you to download and read the last applicable
Rotax recommendations. Rotax runs a free subscription service to advise
you of Service Bulletins, Service Letters and manual updates. You can
also search their website by engine s/n.

Regarding engine run-in, the Rotax takes about 20-35 hours to run-in, as
indicated by the lower running temperatures attained after the initial
period. Of course, it is not i"n the manual", but to achieve optimal
life for a new engine, it is best not to thermally abuse it during the
bedding down process. Prolonged ground runs are best avoided.

BTW, Philip Lockwood has written interesting articles on the
installation and operation of the Rotax 4-strokes.

FWIW,
Best regards,
Gilles
http://contrails.free.fr


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hgmckay



Joined: 23 May 2006
Posts: 397

PostPosted: Sun Sep 03, 2006 10:43 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Thom/Gilles:

I have read the FAA Special Airworthiness Information Bulletin dated Aug.
30, 2005 and the Austro Control AD No. A-2004-004R1 dated December 22, 2004,
both of which address this issue. The FAA document simply states that
operating above the 120 degree F with 50/50 mix, loss of coolant and engine
over heating can occur. That did occur. The Austro Control AD states that
the Max CHT is 120 degrees F with 50/50 mix. I exceeded that (130 degrees
F). All that being said, my question is "have I damaged my engine"? Any
thoughts?

Hugh

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PostPosted: Sun Sep 03, 2006 12:00 pm    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hugh,

Quote:
I have read the FAA Special Airworthiness Information Bulletin dated Aug.
30, 2005 and the Austro Control AD No. A-2004-004R1 dated December 22, 2004,
both of which address this issue. The FAA document simply states that
operating above the 120 degree F with 50/50 mix, loss of coolant and engine
over heating can occur. That did occur. The Austro Control AD states that
the Max CHT is 120 degrees F with 50/50 mix.

Thoroughly reading the Maintenance, Installation and Operator's manuals,
and the SBs and SLs direct from Rotax will give you a better
understanding of the engine operation and limitations.
Quote:
I exceeded that (130 degrees
F). All that being said, my question is "have I damaged my engine"?

Only the engine knows ;-(

You sure did not do it much good, but did you do much harm ? Only a
knowledgeable Rotax engineer, with much experience about this type of
engine could answer. Why not give Lockwood Aviation a call ?

What I would advise you not to do again, is remove the coolant cap
before the engine has cooled down. The circuit is pressurized, and by
premature release of the pressure, the coolant starts to boil. And
boiling means massive cooling. That is shock cooling the hot spots
within, and no engine likes that.
But those engines are very rugged, and very tolerant. So Lockwood may
shrug about it. (and you risk scalds).

Out of memory, the maintenance or operator manual may give information
about the checks following overheating.
What I would do after consulting knowledgeable people :
After those checks, start again, and limit ground operation to what is
necessary to ascertain correct operation. During flight tests, limit
full throttle operation to what is necessary to climb to a safe
altitude, without leaving the temperatures exceed the normal operating
range. During descent, beware of shock-cooling.
For subsequent flights, never let the engine run outside its
limitations, and gradually increase cruise power duration, with, at the
beginning, short bursts at full throttle.

Best regards,
Gilles
http://contrails.free.fr


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hgmckay



Joined: 23 May 2006
Posts: 397

PostPosted: Sun Sep 03, 2006 6:53 pm    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Gilles:

Thanks for the advice and counsel. I will call Lockwood Aviation. By the
way, I did not open the coolant cap until the engine had cooled down. The
boiling coolant was in the overflow bottle with some being dumped out
through the overflow line. After cool down, the coolant that was in the
overflow bottle was sucked back into the engine. I then opened the cap and
replenished the lost coolant (aprx. 1 pint).

Hugh

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Thom Riddle



Joined: 10 Jan 2006
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Location: Buffalo, NY, USA (9G0)

PostPosted: Mon Sep 04, 2006 6:11 am    Post subject: Re: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Giles,

I have reviewed, again, my Operator's Manual, Installation Manual, Line Maintenance Manual, Heavy Maintenance Manual and all Service
Documentation available at Rotax-owner.com since July 1998 (date of my Operator's Manual). The only place I found what could be interpreted as a "normal cylinder head temperature range" is in the Heavy Maintenance Manual. See attached image. All the other documentation I've looked at contain only a Maximum CHT specification. You will notice that it says the "operational temperature" is 90-120C (194-250F) with a MUST NOT EXCEED CHT of 150C (300F). It also says what to do if the maximum is exceeded. In Hugh's case, he did not exceed the maximum. I don't think Hugh should be at all concerned about having run his engine at 130C CHT.

I'm not trying to be argumentative, just wanting the facts to be known. This is the best information I've been able to find on the subject. If you know of another more up-to-date source from Rotax, please let us all know.


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PostPosted: Mon Sep 04, 2006 7:33 am    Post subject: Re: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Giles,

I just found the rev_3 update (July 2004) to the 912 Operator's Manual and it does indeed include the normal CHT range of 75-110C (167-230F). The MUST NOT EXCEED temperature is still 150C (300F). This update and two earlier ones were found at

http://www.rotax-aircraft-engines.com/

Curiously, the North American importer's website

http://www.kodiakbs.com/

does not have these updates. Their latest version of the Operator's Manual on their website is dated July 1998. Perhaps they also have these updates but I could not find them on their site. I will be using the the first link I listed above, from now on.

Thanks for the motivation to keep looking.


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PostPosted: Mon Sep 04, 2006 7:38 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hi Thom,

Quote:

I have reviewed, again, my Operator's Manual, Installation Manual,
Line Maintenance Manual, Heavy Maintenance Manual and all Service
Documentation available at *Rotax-owner.com* since July 1998 (date of
my Operator's Manual).
The only place I found what could be interpreted as a "normal cylinder
head temperature range" is in the *Heavy Maintenance Manual.* See
attached image. All the other documentation I've looked at contain
only a Maximum CHT specification.

Operator's manual Rev 3, July 2004 page 10-1, states the limitations
and best operating ranges.
An updated version of the various manuals can be downoaded from the
Kodiak research website : http://www.kodiakbs.com/tiintro.htm
The Rotax-owner's website provides the list of effective documentation
for the 912 :
http://www.rotax-owner.com/SI_TB_INFO/returndoc.asp?PATH=http://www.rotax-owner.com/si_tb_info/serviceb/sb-all-000-r4.pdf&DOCID=SB-912-000&S_TYPE=SS
Quote:
You will notice that it says the "operational temperature" is 90-120C
(194-250F) with a MUST NOT EXCEED CHT of 150C (300F). It also says
what to do if the maximum is exceeded. In Hugh's case, he did not
exceed the maximum. I don't think Hugh should be at all concerned
about having run his engine at 130C CHT.

Let's try a thought experiment. Suppose with start with two brand new
identical engines. One is run at 149°C from the start. The other is
thoroughly run-in and used inside normal range by a caring owner, but
one day, experiences a short temperature excursion up to say, 151 °C.
Would you still say the #1 was soundly used, and the #2 engine is to be
grounded ? What happens between 149.9°C and 150°C ?

Limits are just that, limits. I would not be too confindent with an
engine that has been consistently run to its red line, just because "the
pointer did not pass the red mark".

Engines are best treated with care, and not thermally abused.
But of course, it's not my engine.

Best regards,
Gilles
http://contrails.free.fr


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Thom Riddle



Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

PostPosted: Mon Sep 04, 2006 8:07 am    Post subject: Re: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Giles,

You are correct, of course, in that the difference between 149 and 151 degrees is not meaningful and that operating in the normal range is better than running near the redline. Howecer, I can tell you that a one time excursion above the temperature limit, though not good for the engine, is not necessarily cause for alarm. If this happens (it did not happen to Hugh's engine), it is reason to investigate the cause and remedy it before operating the engine again. Also, it is just as important to make sure the engine is cooled down properly before shutting it off.

I am a retired mechanical engineer and spent most of my career in machine design. It is normal in this business to over-design machines so that if the operator does inadvertently operate out of recommended ranges, the machine is not likely to self-destruct. Another way of saying this is that a reputable manufacturer usually is conservative in documenting operating limits. This does not mean that the limits should not be observed but that a single, slight excursion over the temperature limits is not necessarily reason for concern, if the cause is discovered and remedied.

In my experience, RPM limits are usually more important in the case of a single excursion past redline because forces on the reciprocating parts of the engine are proportional to the 4th power of the rotational speed. That is why our prop pitch is set such that in straight and level flight, at full throttle, the maximum rpm is only 5,500 rpm. I don't want to be anywhere near the 5,800 rpm redline, even though it is "okay" at that speed for up to 5 minutes.

I think we are in general agreement and the discussion has been of value to anyone who cares, or at least I hope so.


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PostPosted: Mon Sep 04, 2006 9:51 am    Post subject: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Hello Thom

CHT max with EG and .9 bar 240F
CHT max with EG and 1.2 bar 250F
CHT max with Evans and .9 bar 300F 912 and 275F 912S and 914

See:
http://www.rotaxservice.com/rotax_tips/rotax_feed4.htm

I remember seeing in documentation from Rotax these changes, it was
convoluted.

Ron Parigoris


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PostPosted: Mon Sep 04, 2006 10:20 am    Post subject: Re: Allegro 2000, 912UL Initial Engine Test Run Reply with quote

Ron,

Thanks!

That link is a great resource. I did not realize they lowered the MAX CHT to 250F w/ 1.2 bar pressure cap from 300F. Big difference.


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