Cylinder head cracks

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Boatguy
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Re: Cylinder head cracks

Post by Boatguy »

The report is now 5 1/2 years old and Austro has issued numerous service bulletins. Is there evidence that these "teething" persist?

Last year's problems with the HPP seem to be associated with the "teething" problems of the new blocks.
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Re: Cylinder head cracks

Post by UglyBuzzard »

My total ignorance is why I asked. Do you guys slide a borescope down the injector holes at annual, like the Lycoming guys do by pulling a plug? Seems they make them small enough for that.
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Re: Cylinder head cracks

Post by Boatguy »

Ask an IA.
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Re: Cylinder head cracks

Post by Mdm0515 »

And there's this...down under

https://www.atsb.gov.au/publications/in ... -2017-090/

Loss of control and collision with terrain involving Diamond DA40, VH-YPQ, 1 km south of Port Macquarie Airport, New South Wales, on 8 September 2017

What happened

On the evening of 8 September 2017, an instructor and student from the Australian International Aviation College were preparing to conduct night training circuits at Port Macquarie Airport, New South Wales, in a Diamond DA40 NG aircraft, registered VH-YPQ. As it was the student’s first time conducting night circuits, once lined up on the runway, the instructor took the aircraft controls for the take-off.

After take-off, as the aircraft climbed, the instructor heard and felt the engine and propeller surging. Propeller speed and engine power fluctuations occurred from about 200 ft above the runway and increased in amplitude as the aircraft climbed to about 400 ft. Recorded data showed that the engine was producing full power despite the fluctuations. The instructor interpreted the fluctuations as a partial engine power loss and commenced a left turn, aiming to return and land on the runway in the opposite direction to the take-off. The instructor had considered landing straight ahead but assessed that there was power available to turn and that they would be unable to see and avoid trees or to be sure to land in a suitable clearing ahead.

In the 10 seconds that the instructor was assessing and making decisions about a perceived partial power loss, the airspeed reduced from 75 to 69 kt due to the aircraft’s nose-up pitch attitude. Then, at the same time as commencing the turn back towards the runway, the instructor reduced engine power to 30 per cent, while maintaining a nose-up attitude, and the airspeed reduced rapidly.

During the turn, the aircraft aerodynamically stalled resulting in a loss of control. Although the aircraft pitched down and the instructor subsequently increased the power, control was not regained. The aircraft descended and collided with trees, coming to rest inverted. The student and instructor were seriously injured, and the aircraft was destroyed.

What the ATSB found

After reducing the power, the instructor did not maintain adequate airspeed during the turn. This resulted in an aerodynamic stall, loss of control and collision with terrain.

The aircraft manufacturer could not determine the reason for the engine speed fluctuations. Propeller speed fluctuations had occurred in other aircraft, and either resolved without pilot input or by moving the power lever.

Although not contributing to this occurrence, in the course of the investigation it was found that engine cylinder heads for the aircraft type were cracking prior to reaching their service life.

What's been done as a result

After the accident, the Australian International Aviation College:

added a requirement to the take-off safety briefing to include setting partial power safety speed in the event of a partial power loss
conducted partial engine failure after take-off training for instructors and students, comprising pre-flight planning and self-briefing, ground training, and flight training
performed flight simulator tests for partial engine failure after take-off conditions in each single engine aircraft model operated by the flying school to assess the power required to maintain altitude in the event of a partial power loss.
Safety message

In this accident, the instructor perceived there was a partial power loss. The ATSB research report Avoidable Accidents No. 3 – Managing partial power loss after take-off in single-engine aircraft provides information to assist pilots maintain aircraft control in the event of an emergency or abnormal situation after take-off. The report prescribed initial actions to be considered including:

Lower the nose to maintain the glide speed of the aircraft. If turning is conducted, keep in mind an increased bank angle will increase the stall speed of the aircraft.
Maintain glide speed and assess whether the aircraft is maintaining, gaining or losing height to gauge current aircraft performance.
Fly the aircraft to make a landing, given the aircraft’s height and performance, and the pre-planned routes for the scenario.
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Re: Cylinder head cracks

Post by Boatguy »

This has been reported before and the report circulated. There have been a couple incidents of maintenance induced partial power failures from poor attachment of the intake manifold ducting during servicing.
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Re: Cylinder head cracks

Post by Mdm0515 »

Boatguy wrote: Fri Apr 01, 2022 3:43 pm This has been reported before and the report circulated. There have been a couple incidents of maintenance induced partial power failures from poor attachment of the intake manifold ducting during servicing.
Yes. I had originally reported this set of occurrences and report on DAN. Unless I missed something, I have not yet seen any maintenance-related causality regarding these multiple cylinder head failures.
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Re: Cylinder head cracks

Post by Mdm0515 »

Boatguy wrote: Fri Apr 01, 2022 3:43 pm This has been reported before and the report circulated. There have been a couple incidents of maintenance induced partial power failures from poor attachment of the intake manifold ducting during servicing.
I think the larger issue is relevant way down towards the end of the Aussie report related to multiple cylinder head failures at this flight school, many within within normal TBO guidelines. Worth reading in its entirety.
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Re: Cylinder head cracks

Post by Davestation »

That is interesting about the inter-valve cracks. I have yet to see one on an AE head, though I would have bet A LOT of money that we'd find at least one on a 1.7L head whenever we pulled one off. I've been operating under the assumption that the head is warped, as merely changing the head gasket does not solve the problem. We had a CD-135 once that overheated and would actually run fine up to about 30% until it would start puking coolant like it was allergic to it. Presumably the head warped significantly when it overheated and the higher cylinder pressures once the turbo started loading up found a quick path to a water jacket.

“are not expected to restrict the functionality in any manner” sounds a bit scary but to their credit, nobody would know the heads were cracked until they were pulled off. We'd have one low compression cylinder(still made full power) due to the common cracks between the glow plug port and a valve, but when we pulled the head off we'd find a dozen others in all cylinders between valves as shown here, and including at the glow plugs, though the other cylinders had normal leak-down readings.
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