New Engine Break-In Procedures of Accu-Sim Aircraft?

Find or share aviation knowledge
new reply
Harry_The_Pilot_Guy
Airman
Posts: 16
Joined: 11 Dec 2014, 15:58

New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by Harry_The_Pilot_Guy »

Hi all,
I have the C172 and C182, and continue to be baffled by their realism. I noticed that even the "break-in" of a new engine seems to be simulated. With a new engine in my accu-sim aircraft, each cylinder will have different compression by a few PSI or so when I run a compression test; however on an engine that has about 30 hours on it, each cylinder will have the same compression (or nearly the same compression). I believe this is because the piston rings on a new engine are not seated perfectly yet, correct?

I have flown an actual C172P with a new engine, and the owner wanted it to be run at greater than 75% Power for no shorter than 1.5 hours at a time until the engine had accumulated about 50 hours or so. The C172 POH has this written in the Airplane Systems and Descriptions Section: "The engine underwent a run-in at the factory and is ready for the full range of use. It is, however, suggested that cruising be accomplished at a minimum of 75% power until a total of 50 hours has been accumulated or oil consumption has stabilized. This will ensure proper seating of the rings." This got me thinking...is it necessary to run the engine of my accu-sim aircraft according to the break-in procedures listed in the POH?

Your input would be much appreciated,
-Harry

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

I recall from previous discussions on the subject that the break-in would not be simulated. Of course, one can still fly it as if it was, on some occasion I at least did. :)

-Esa

User avatar
Piper_EEWL
Chief Master Sergeant
Posts: 4544
Joined: 26 Nov 2014, 14:14
Location: Germany

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by Piper_EEWL »

That's an interesting topic. We just got a new engine in our Super Cub and the recommendation is to not run it below 2400rpm during cruise for the first 25h with a flight time minimum of 20 minutes.

I was actually a bit suprised with that procedure because with automobile or motorcycle engines there is usually a reduce maximum rpm when under run-in. Though I don't think there are any published procedures anymore for modern cars.
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

Yeah, the point in break-in recommendations is to use it hard, so to say. :) With fixed-pitch prop this will, of course, result in highish RPMs in most cases, but I don't remember any specific recommendation on operating RPM.

I could ask for opinions from a few gurus.

-Esa

User avatar
Piper_EEWL
Chief Master Sergeant
Posts: 4544
Joined: 26 Nov 2014, 14:14
Location: Germany

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by Piper_EEWL »

Yes that would be really interesting Esa. It seems that there's a lot of opinions out there on this issue. Would be nice to hear from someone with lots of experience on break in.
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

Yes, I guess it might - I've never went too much into science (or "science") of the break-in recommendations myself.

The few aspects are of course that the higher power settings with associated higher cylinder pressures help to seat and wear in the rings better, and that the proper operating temperature is rather critical for these engines, especially during break-in. An air-cooled airplane cylinder is not necessarily completely straight-walled but has (or may have) a slight taper or "choke" in it. This is to account for uneven heating and resulting expansion of it, and it should be more or less straight in bore when at its operating temperature.

-Esa

User avatar
CAPFlyer
A2A Aviation Consultant
Posts: 2241
Joined: 03 Mar 2008, 12:06
Location: Wichita Falls, Texas, USA

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by CAPFlyer »

The most interesting thing to me about airplanes is that they are designed to work BETTER when operated a lot. Its been found over the years that one of the biggest issues with not making TBO on a piston aero engine is lack of use, not overuse. If you let an engine sit for several weeks between usage and then sit there "babying" the engine, it actually REDUCES the life of the engine. These engines are designed for continuous use at high RPM (car engines aren't. They're designed for extended operation at low RPMs - around 2000 in fact with a max RPM of 10,000 in most cases). As such, the only way to properly operate them is to use them HARD. 55% Power cruise on a flight every few weeks will result in problems because the rings and equipment never gets up to proper temperature and then you shut it down for another few weeks. The amount you save of fuel won't equal the amount you spend on that premature overhaul.

Let's put it this way -

Convair 240 flying 3-5 hours one day every 2 weeks. TBO was under 200 hours because pilots were abusing the engine in two ways - 1) using too much power on takeoff (100LL restricts takeoff power to 50") and 2) too low cruise (900HP). Pilots told to stop abusing the engines (under penalty of termination), engines run at power for at least 30 minutes every week on the ground when it didn't fly, and upped cruise to 1100HP, and the engines were making 900 hour TBO. Due to low utilization, we didn't expect it to get much better than that, but it was a major improvement.
Image

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

Great post, Chris! Thank you!

When comparing to car engines, one important consideration is that they are designed for wide ranges of RPMs, and for constantly varying rotational speed. An airplane engine, on the other hand, is mostly a relatively constant-speed apparatus on a short term, and the entire useful RPM range is very limited. A car engine could, in practice, be operated in between 1200...6000 RPM or so in everyday regular driving whereas an airplane engine could be limited to, say, 1900...2600 RPM. This shows in many aspects of the design, not least in the moment of inertia of rotating and reciprocating parts.

It is indeed a very good point that "hard use" is not automatically harmful - quite the opposite! I always want to bring up the engines of glider towing airplanes and skydiver lifts, which are likely the ones pushed the hardest. They tend to do very well in general, in comparison to a typical club or private travel airplane.

While it is apparently quite generally accepted that continuous high-power usage, unloaded high RPMs, too high MP + very low RPMs, and whatnot are stressing to the engine, surprisingly little consideration is given on what should be the optimal then? This is because, as you say, "babying" the engine is not that good to it either. There lies that thin line of optimal somewhere, balancing all the settings.

As much as I hate it, the "piston ring miles" seem to be a relatively good rule-of-thumb to start with: At takeoff, full available MP and full RPM to balance it reduces the time needed for such a pushing setting. During climb, the same applies. One wants to get up to the cruise as fast as possible, and perhaps reduce the RPM to balance out the naturally reducing MP. During cruise it still applies: generally one wants to pick the lowest usable RPM setting for the performance required, together with full throttle when applicable. It gets a bit involved with the mixtures and everything to balance the low RPM, but anyway!

And so on.

But even this rule-of-thumb runs out for running an engine at too low RPM is not good, even if it apparently runs very well. A classic example of this is the Cessna 175, where the engine driving the propeller via a reduction gear, the engine itself being designed to run at around 3000 RPM, but pilots having been designed to run the engine at around 2000 RPM. The ignition timing of 28° BTC should ring some bells on what that does to the engine.

BTW, when discussing "where an engine wants to be", the ignition timing is one of the most important, revealing parameters one should note. Interestingly, it is very little, if at all, discussed in pilot training, at least around here. It kind of sets the origin to all the other parameters: RPM, mixture, MP. It also tells quite a bit about the nature of the engine. For instance, if a comparatively low-RPM engine had a particularly large ignition advance, I'd expect it to be a lame engine, so to speak, whereas if vice versa, I'd expect it to be either turbo/supercharged or of relatively high compression ratio.

Running a piston engine is like pedaling a bicycle: there is that balance of pushing and the numbers of pushes.

-Esa

ammorman
Airman
Posts: 18
Joined: 03 Apr 2013, 21:27

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by ammorman »

When I first get into an accusim aircraft, I like to perform a break in like what would be done in real life just for immersion. As far as I have noticed, not performing a break in with the accusim aircraft doesn't affect compressions or oil consumption, but it's a habit I've developed from working on the real thing. If you google Lycoming service instruction 1427C, it provides a real world break in procedure.


Sent from my iPhone using Tapatalk
To invent an airplane is nothing. To build one is something. To fly is everything. — Otto Lilienthal

User avatar
Piper_EEWL
Chief Master Sergeant
Posts: 4544
Joined: 26 Nov 2014, 14:14
Location: Germany

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by Piper_EEWL »

Interesting posts guys. Thanks for sharing your view and experience.

I also think that babying the engines is not healthy. The problem that I see with engines used on tow planes and skydiving planes though is if they're not treated correctly with respect to temperature management. I think that's an issue especially in clubs where a lot of different pilots operate the planes. If one does everything correct I don't think there's a problem with the engine reaching Its design TBO even though it might be highly stressed.

Happy flying
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

Around here, many glider tow airplanes are such as Piper Pawnee or some specifically built models. These tend to have relatively efficient cooling even at low airspeeds associated with glider towing. When some usual GA types, which sacrifice cooling efficiency for cruise performance, are used in those operations, bad things will happen.

-Esa

User avatar
Piper_EEWL
Chief Master Sergeant
Posts: 4544
Joined: 26 Nov 2014, 14:14
Location: Germany

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by Piper_EEWL »

The problem being that a lot of flying clubs have to buy planes that can do everything. Tow, cruise be used for training. So you need a compromise.
B377&COTS, J3 Cub, B-17G, Spitfire, P-40, P-51D, C172, C182, Pa28, Pa24, T-6 Texan, L-049&COTS, Bonanza V35B

User avatar
AKar
A2A Master Mechanic
Posts: 5207
Joined: 26 May 2013, 05:03

Re: New Engine Break-In Procedures of Accu-Sim Aircraft?

Post by AKar »

That is the case sometimes. Around here, several big gliding airfields have enough activity to justify dedicated towing airplanes. For now, at least.

-Esa

new reply

Return to “Flight Academy”

Who is online

Users browsing this forum: No registered users and 10 guests