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First Flight - Engine Break In

Tsabean

Active Member
Preparing for first flight with a new (overhauled) O-320. Lycoming SI 1427 indicates 1 hour at 75% power then 2nd hour at 65-75% power.
Vans section 15 recommends first flight should be limited to 30-40 minutes. Do the Lycoming time recommendations need to be completed cumulatively or can they be broken down into shorter sessions.

Thanks, Tom
Rv4
O-320
Hartzell C/S
 
My Opinion

Just my opinion from reading all these threads over the last several years, Run the thing hard, but dont compromise safety. So follow Vans recommendations using short flight. Above all else, watch the cylinder head temps; apparently the CHTs are what determines glazing or not. JMHO
 
CHT

You should search for the Mahlon Russell break in information as well as others. You may have a difficult time finding any qualified person or company that believes that Vans number of 440 CHT is acceptable.
There is absolutely nothing wrong with reducing power and increasing airspeed to control CHT on early break in flights. Step climb if necessary.
Towing the airplane to the end of the runway is a helpful option. Do a runup before towing. Let the engine cool. Tow to the end of the runway. Perform all pre takeoff items before starting. Start the engine, do a quick mag check and takeoff. This is based on the oil still being warm from the previous run.
If you have a manifold pressure gage, reducing the power to 24" and leveling off momentarily at 500' AGL will keep the CHT under control. Climb at the highest possible airspeed even if the rate of climb is only 3-500 ft per minute.
Reducing the power momentarily to control CHT will not glaze the cylinders. High CHT glazes the cylinders. Target is not to exceed 400 degrees. Momentary excursion above 400 immediately reduce the power.
Be sure to pre oil the engine before first start. Remove one set of spark plugs and motor the engine with starter until oil pressure comes up.
 
You should search for the Mahlon Russell break in information as well as others. You may have a difficult time finding any qualified person or company that believes that Vans number of 440 CHT is acceptable.
There is absolutely nothing wrong with reducing power and increasing airspeed to control CHT on early break in flights. Step climb if necessary.
Towing the airplane to the end of the runway is a helpful option. Do a runup before towing. Let the engine cool. Tow to the end of the runway. Perform all pre takeoff items before starting. Start the engine, do a quick mag check and takeoff. This is based on the oil still being warm from the previous run.
If you have a manifold pressure gage, reducing the power to 24" and leveling off momentarily at 500' AGL will keep the CHT under control. Climb at the highest possible airspeed even if the rate of climb is only 3-500 ft per minute.
Reducing the power momentarily to control CHT will not glaze the cylinders. High CHT glazes the cylinders. Target is not to exceed 400 degrees. Momentary excursion above 400 immediately reduce the power.
Be sure to pre oil the engine before first start. Remove one set of spark plugs and motor the engine with starter until oil pressure comes up.

400 may be a bit low for a target for an engine without time on the test stand; The first hours is the worst for heat. Several folks here have posted their test stand data and most have the CHTs topping out at 435. I am guessing that is what the shops use as a max. I can say that on my 320, I let two cylinders get above 450 for a few seconds and both of them were glazed. The other two were not. They topped out around 440, I think but can't be sure.

I had a test pilot with me flying on the first flight and he didn't like the way the engine sounded, so he started leaning it. Took me 30 seconds to figure out what he had done and that was enough to glaze them.
 
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Lycoming

Preparing for first flight with a new (overhauled) O-320. Lycoming SI 1427 indicates 1 hour at 75% power then 2nd hour at 65-75% power.
Vans section 15 recommends first flight should be limited to 30-40 minutes. Do the Lycoming time recommendations need to be completed cumulatively or can they be broken down into shorter sessions.

Thanks, Tom
Rv4
O-320
Hartzell C/S

Here are some references.
https://www.lycoming.com/sites/defa...ating engine Break-In and Oil Consumption.pdf
https://www.lycoming.com/content/hard-facts-about-engine-break
https://generalaviationnews.com/2020/08/17/engine-break-in-101/
 
Is there any break-in difference for a newly rebuilt engine versus the Lycoming factory new engine?

From my engine log, my IO360-M1B has been run for almost 120 minutes at the factory. Some runs were made at low power, and some at high power.
 
Is there any break-in difference for a newly rebuilt engine versus the Lycoming factory new engine?

From my engine log, my IO360-M1B has been run for almost 120 minutes at the factory. Some runs were made at low power, and some at high power.

Not really. However, you might find that most if not all of the break-in was done at the factory. I found mine was pretty much fully broken in from the factory as my CHTs never changed or oil consumption. I still followed the guidance though.
 
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Break in

The Mahlon Russell info can be found by searching "Mahlon Russell engine break in procedure".
Mahlon recommends a very short first flight.
The OP specified an overhauled 0 320.
Mahlon does not specify hard limits for first flight but does state a limit of 350 for ground runs and a limit of 115% of the highest ground run temperature for first flight. In my case ground run was at the 350 limit and 115% of that is 402.
That served me very well. 0 320 with 10-1 pistons, very tight baffling with plenum and very small cowl inlet and outlet. I do have a cowl flap which was fixed in the open position for initial flights. Ambient temperatures around 110 F. Density altitude around 4000'. There was a noticeable CHT drop at around 2 hours. No measurable oil consumption.
 
I’ve broken in five Lycoming factory rebuilts using their procedures. One or two were done in a single flight, the others in several grabs. It made no difference to long term performance.

Jack
 
Did you have a engine shop do the overhaul? They will usually provide break-in instructions with their overhauls. The shop I used a couple of years ago provided good break in instructions, and more than willing to answer questions, as well as guidance on the proper procedures.
 
What I did

I also built a -4, and overhauled an O320H2AD that I put in it. I'm an A&P/IA, and had good confidence in both the plane and the engine. Because the RV's are such a well proven design, I had little worry of any surprises that would be render the airplane hard to fly, and felt as long as the engine indications (tested on short ground runs) stayed in range, I would make the first flight get through the high power range of the break in. My first flight was 1 hr. 15 min, and I simply stayed over the airport, loitering at 5K. After I was comfortable with the break in procedure, I did a few minutes of slow flight to validate airspeed vs. impending stall and idle / throttle response checks, I landed. If you have a Go-pro or similar camera (I had one on a headband), its a fantastic tool for later review of panel scans and speed recordings both visual and audio. Congrats on getting to this stage! Your going to love it.
 
I strongly recommend you keep the first flight relatively short.

I found two significant issues after pulling the cowling following my first flight. I had a significant oil leak from the hose going from the prop governor to the front end of the engine. That hose is only pressurized when the power is high enough so the prop is governing, so the oil leak never became evident during the short ground run prior to first flight. And, the alternator pulley was rubbing on the lower cowling, and had ground a pretty deep groove. I fear that it might have worn all the way through if I had done a long flight. It hadn't rubbed during the ground run, but the air loads on the lower cowling from the high speed engine break-in run had pushed the cowling closer to the engine.

I was very glad that the first flight was only 20 minutes long.
 
Excellent advice in this thread from some very qualified people!

One thing I learned on my first flight is that it's hard to set the max prop RPM doing only ground runs, even full power ground runs with the aircraft tied down. Be ready to pull the blue knob back a bit once you get some velocity.
 
Finally got first flight accomplished. Used a lot of suggestions from this thread. The towing the aircraft to the departure runway alleviated the concern of high CHTs on the first hop. CHTs were not an issue, max seen was 402F. Once airborne the RV grin was certainly in evidence.
Thanks to all the suggestions, this forum has been an enormous help from the start.
Cheers, Tom
 
Congratulations on your first flight! Good to hear that all your pre-flight worries about break-in were resolved satisfactorily.
 
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