0320H2AD

0320H2AD

Is It true that an 0320H2AD is inferior when compared to other O320s ?

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Re: 0320H2AD

Yes.

The lifters in the H2AD are barrell type instead of mushroom type, resulting in higher loads on the cam lobes. This was done to make the lifters easier to service, but the higher load results in severe spalling. An improved lifter design was incorporated into new H2AD engines and retrofitted to earlier ones (Lycoming Service Bulletin #424). An anti-wear oil additive is required (Lycoming Service Bulletins #446C and #435C). AeroShell W 100 Plus contains the additive (TriPhenyl Phosphate).

Lycoming eventually developed the "T" case modification (Lycoming Service Bulletin #1406B) in which the engine case is modified to accommodate larger lifters. These larger lifters are not as largeas the mushroom lifters on other Lycoming engines, but they are bigger than the original barrell lifters, increasing the contact area between the lifter and the cam lobe, reducing the pressure per square inch of contact surface, and reducing cam lobe wear and spalling. The "T" mod has reduced the problem, but not eliminated it. Ney Nozzles to prelubricate the cams are also a popular mod for the H2AD.

Operators in warmer climates and engines that get used regularly seem to fare better than those used in colder areas that don't see regular use.

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Re: 0320H2AD

I have an "H" engine.  I live in a cold climate.  This engine has performed great.  It starts easily, runs smoothly.  Before I purchased my 79 Skyhawk, I was warned about this dreaded engine.  I do fly it frequently, 5-8 hours a week.  Many times the temps are below zero F.  I change the oil and filter every 50 hours and I am very happy with it.  Are you thinking about purchasing an "N" model?  Good Luck!

Rich

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Re: 0320H2AD

One other point worth mentioning related to the O-320-H2AD is its use of a D4RN-2O21 impulse coupling dual magneto. This arrangement is different from most other O-320 models in that both L and R magnetos are in a single case and use a single drive through the accessory case. If the gears jam or the one drive gets sheared, both mags quit and your airplane becomes a glider.

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Re: 0320H2AD

Dave, the H2AD engine is as good as the others, sure they had a lot of problems in the early days, yes the cam followers can 'spall'
[esp. on the pre T mod engines]
Oil changes and good usage, oil additive [or the shell 100 plus] are essential to keeping any engine going. We used to run about a dozen 172N's and pull the 'lifters' each 100 Hrly, if we found one starting to look sick we ditched it, it only adds about an hour to the job when you know what your doing, and can save the camshaft. I should also say that in the 'other' engines the lifters cannot be removed without splitting the case, but they can still kill camshafts, you just don't know about it until it it runs sick enough to be found or is found at o/h, and either way it takes a long time for a crook camshaft to cause noticable engine running problems, but its engine out when its discovered. At least the H2AD can be checked without pulling the engine.
Stan mentioned the single drive magneto could be a problem if the drive gear got jiggered, I don't agree with him implying that is a problem for the H2AD. [my apologies Stan.]
The magneto did have problems early and by now they should have all been modded and be ok,[those problems were in the mag.]
as for single drive being a risk of engine failure due to drive gear problems more than 2 separate mags, lets look at it this way,
if the engine gear train that drives a 2mag engine fails, it will destroy the drive to both mags,[and vac pump/camshaft]
if the single mag drive train fails the result is the same -
     The engine will stop.
Now to confuse the issue, NEVER have I heard that the Piper Chieftain engine is a sick puppy because it has a single drive magneto.[and as they often run RPT with ten pax, wouldn't FAA jump on this if it were a problem?]
Although the Lycoming people blame Cessna for the design of the H2AD, [it did have a lot of niggles early] with good maintenance its a good reliable engine.
safe travels
HOWARD.

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Re: 0320H2AD

Howard/Stan
When an 0320H2AD is STC'd for 160hp how doze this change/improve the engine...or doze it?
Dave

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Re: 0320H2AD

The O-320-H2AD is rated at 160 horsepower; it doesn't need any STC.

I think you might be referring to the RAM STC to change the rated horsepower of the O-320-E2D from 150 horsepower to 160 horsepower?

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Re: 0320H2AD

Howard, Dave's original question was "Is It true that an 0320H2AD is inferior when compared to other O320s?"

I believe the overwhelming evidence, based on the lifter problems and Lycoming's many attempts to fix that problem, is "Yes"..

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Re: 0320H2AD

Regarding the reliability of the Bendix D-2000/D-3000 series dual magnetos, the FAA issued Special Airworthiness Information Bulletin NE-02-31 as a result of an investigation of in incident involving engine failure caused by the failure of BOTH distributor gears in a Piper PA-32RT-300. NE-02-31 also cites an additional eleven Service Difficulty Reports since 1995 involving engines equipped with these mags and related to failure of both distributor gears.

The Australian CASA issued AWB 74-1, Issue 1, on22 May 2002, on the same subject.

The FAA issued AD 82-11-05 requiring replacement of the distributor gear assembly in these mags.

Bottom line is that the Bendix D4RN-2021 dual magnetos used on the O-320-H2AD simply do not afford the same level of redundancy as two separate magnetos.

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Re: 0320H2AD

The following is excerpted from NTSB Report FTW02LA079:

"According to the FAA inspector, who responded to the accident site, both wings and the firewall were substantially damaged. The aircraft was recovered to a hangar for further examination. On February 11, 2002, the flight instructor, who was also a certified mechanic and maintained the airplane, and the FAA inspector examined the Lycoming O-320-H2AD (serial number L5684-76) engine. During an ignition timing check, the engine crankshaft was rotated by hand; however, "the apparent spark from each of the 8 leads was not what would be expected from this system." The Continental/Bendix D-3000 single-drive dual magneto's lower timing inspection port was removed and approximately 2 cups of engine oil drained from the magneto. It was determined that the magneto driveshaft oil seal had failed allowing engine oil to enter the magneto."

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Re: 0320H2AD

...and another. NTSB Report LAX02FA056:

"The Lycoming O-320-H2AD engine was equipped with a Teledyne Continental D-3000 dual magneto (both magnetos are contained in a single housing and driven by one drive gear). During engine rotation, investigators did not hear a strong click from the impulse coupling, and they could not obtain spark from the ignition leads. They removed the magnetos and observed the magneto drive gear on the crankshaft rotate freely. They rotated the magnetos manually and noted that they rotated freely.

The Safety Board IIC took the magnetos and ignition harness to an accessory shop for inspection. The repairman connected the magnetos and ignition harness to a test stand, and the magnetos did not fire. The repairman disconnected the harness from the magnetos and noted that the impulse coupling did not snap briskly when he manually rotated the magneto.

The repairman cleaned the magnetos and reconnected them to the test stand using a test harness. He observed flash crossover from the coil to ground.

He separated the distributor block from the magneto and cleaned the unit. He removed the impulse coupling to set the timing and found a broken coupling spring."

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Re: 0320H2AD

..and another. From NTSB Report LAX01LA231:

"The Lycoming O-320-H2AD engine (serial number L-5102-76T) had accumulated 302.2 total hours since its last overhaul.

The dual magneto was found secured to its mounting pad with the distributor cap and wires in place. Both "P" leads were secure in their respective ports. A magneto synchronizer was attached at the magneto "P" leads to check the magneto to engine timing. The magneto timing check indicated the left and right points were not opening. The magneto distributor cap was removed to provide a visual examination of the contact assemblies. During manual rotation of the propeller, the points were examined and found not to be opening as the magneto cam rotated.

The magneto (part number D4RN-3000, serial number 1268803G) was removed from the engine and was taken to Homes Aviation, Chandler, Arizona, for further examination. It was confirmed that the points would not open during cam rotation. It was also placed on a test bench and no sparks were noted through the ignition harness. The facility then reset the contacts and timing and retested the magneto. The magneto was found operationally functional after the contact and timing work."

Howard wrote: "as for single drive being a risk of engine failure due to drive gear problems more than 2 separate mags, lets look at it this way, if the engine gear train that drives a 2mag engine fails, it will destroy the drive to both mags,[and vac pump/camshaft] if the single mag drive train fails the result is the same - The engine will stop."

Howard, the drive shafts are designed to shear if a mag rotor gets stuck, thus PROTECTING the engine gear train. With a dual magneto, if the shaft shears, BOTH mags stop. On an engine with two separate mags, the shaft to one of the mags can shear, and the other mag will keep working.

Look, I've flown many hours in H2AD equipped 172Ns and don't hesitate to fly them. I'm just trying to honestly answer Dave's original question, and I believe the statistics show that the O-320-H2AD was (and still is) less reliable than other O-320 models in spite of Lycoming's efforts to improve its reliability.

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Re: 0320H2AD

From NTSB Report FTW00LA207:

"According to a representative of the owner, the airplane was recovered to Air Salvage Of Dallas near Lancaster, Texas, where an engine test run was attempted. The engine remained attached to the airplane with all components the same as they were on the date of the accident, with the exception of using a different fuel tank. The engine would not start. The single-drive dual-magneto was removed from the engine, and a bench test revealed that no spark was being produced from either magneto. An examination of the magnetos revealed that the neoprene cam followers on both sets of points had melted and "smeared," which kept the points from opening."

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Re: 0320H2AD

Stan, I did apologise before I wrote my reply,
yes I agree there have been many incidents of mag failure, however on the whole, I wouldn't kill the bird by saying the thing is dangerous. This single drive mag, in various versions, is used in many other aircraft applications and people don't write off those as bad because of it, even Cessna R182's have a single drive magneto, others include Chieftain, Duchess.
safe travels
HOWARD

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Re: 0320H2AD

I agree Howard - We have a combined Total Time of over 32,000 hours on 3 182RGs running single magnetoes.. They are sent in for Overhaul each 1000 hrs (which equates to 2 1/2 years). So far, So good...

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Re: 0320H2AD

Thanks Jack, its nice to see that someone is getting the utilization that these machines deserve.[read 'all a/c'] I also think that most of the mag problems are directly due to lack of maintenance, and from what you said, I guess you're doing a lot more preventative maintenance than just mags, and that is what keeps aircraft reliable.
Stan cited a few failures, but none of those were from 'engine gear train failure', and in my humble opinion all could be directly related to lack of maintenance of the mag.
Now, back to Dave.
HOWARD.

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Re: 0320H2AD

Thanks Jack, its nice to see that someone is getting the utilization that these machines deserve.[read 'all a/c'] I also think that most of the mag problems are directly due to lack of maintenance, and from what you said, I guess you're doing a lot more preventative maintenance than just mags, and that is what keeps aircraft reliable.
Stan cited a few failures, but none of those were from 'engine gear train failure', and in my humble opinion all could be directly related to lack of maintenance of the mag.
Now, back to Dave.
HOWARD.

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Re: 0320H2AD

One of the best discussion regarding the Lycoming valve difficulties can be found at:
<http://www.prime-mover.org/Engines/Marvel/tbo3.html>

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