New Waste Gate Controller AD for AE300

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New Waste Gate Controller AD for AE300

Post by dgger » Wed May 30, 2018 11:18 am

If you are like me, you might have missed the EASA AD on the AE300 issued earlier this year. It would appear the FAA has now adopted this AD as well which effectively means we are having a new lifetime-limited part being introduced:

EASA: https://ad.easa.europa.eu/blob/EASA_AD_ ... 017-0250_1
FAA: http://rgl.faa.gov/Regulatory_and_Guida ... -07-16.pdf
Diamond: http://support.diamond-air.at/fileadmin ... roller.pdf
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Re: New Waste Gate Controller AD for AE300

Post by CFIDave » Wed May 30, 2018 2:00 pm

This waste gate controller AD (Airworthiness Directive) applies to all Austro DA40 NGs, DA42 NG/-VI, and DA62 aircraft, and unfortunately is a recurring AD that requires all waste gate controllers to be replaced EVERY 250 hours, indefinitely. This applies to AE300 (E4-A, E4-B, E4-C) and AE330 (E4P-C) engines.

Apparently the circlip at the end of the controller's rod can come loose, or the rod itself can break. If either of these occurred, they would cause the ECUs to lose control of the amount of air being forced into the engine's intake manifold, somewhat analogous to a broken throttle cable on a non-FADEC engine. The engine would still continue to operate, but at a sub-optimal fuel/air mixture and at somewhat reduced power; "ECU Fail" messages would be generated by both ECUs for that engine. However, the ECUs could still control prop RPM and fuel injection based on the pilot's movement of the throttle lever.

Austro Engine has come up with a "fix," which involves clamping a pair of short cables alongside of the threaded control rod. If the control rod were to break, the added pair of cables would maintain mechanical continuity, allowing the waste gate controller to continue to operate the turbocharger's waste gate, and the engine would continue to operate normally.

Here's a photo of the fix, showing the pair of clamps and cables added to the control rod (which Austro calls a "con-rod fail-safe bridge"):
Wastegate controller bridge.jpg
The good news is that according to Austro's latest Mandatory Service Bulletin MSB-E4-022/3, installation of the con-rod fail-safe bridge is considered a "terminating action" that no longer requires the entire waste gate controller to be replaced every 250 hours. See: http://austroengine.at/uploads/pdf/MSBE40223.pdf

The bad news is that neither EASA nor the FAA seem to have recognized this con-rod fail-safe bridge as a terminating action in their ADs.

So for now, as Austro engine owners we're still required to replace the entire waste gate controller as a repetitive action every 250 hours. Hopefully this will change soon.
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Re: New Waste Gate Controller AD for AE300

Post by dgger » Wed May 30, 2018 2:34 pm

CFIDave wrote:The engine would still continue to operate, but at a sub-optimal fuel/air mixture and at somewhat reduced power; [...] However, the ECUs could still control prop RPM and fuel injection based on the pilot's movement of the throttle lever.
Having lost turbo pressure in DA42s three times now, I think „somewhat reduced power“ is putting it mildly. Let me add two data points here: At 3.000ft I got a maximum of 80% and at 10.000ft < 30% i.e. this has the potential to seriously ruin your day - particularily when flying in the mountains.
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Re: New Waste Gate Controller AD for AE300

Post by Colin » Wed May 30, 2018 10:14 pm

this has the potential to seriously ruin your day
That's why I like having two of these engines.
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Re: New Waste Gate Controller AD for AE300

Post by Steve » Wed May 30, 2018 11:56 pm

This reminds me of a problem that the Navy had with the PT6 engine on the T34C trainer I flew in 1982. The fuel control unit was only indirectly controlled by the throttle, which told the FCU to adjust the fuel flow based on bleed air pressure. There was a bleed air line which went to the FCU which apparently was prone to cracking. When it cracked, the engine went to idle, regardless of the throttle position.

The solution was to add an auxiliary power lever which was directly linked to the fuel valve in the FCU. Push it and you got fuel dumped into the engine, irrespective of bleed air, etc.

A relatively cheap fix, but you had that extra lever to manage in the throttle quadrant...

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Re: New Waste Gate Controller AD for AE300

Post by rdrobson » Thu Apr 11, 2019 9:56 pm

CFIDave wrote:
Wed May 30, 2018 2:00 pm
The good news is that according to Austro's latest Mandatory Service Bulletin MSB-E4-022/3, installation of the con-rod fail-safe bridge is considered a "terminating action" that no longer requires the entire waste gate controller to be replaced every 250 hours. See: http://austroengine.at/uploads/pdf/MSBE40223.pdf

The bad news is that neither EASA nor the FAA seem to have recognized this con-rod fail-safe bridge as a terminating action in their ADs.

So for now, as Austro engine owners we're still required to replace the entire waste gate controller as a repetitive action every 250 hours. Hopefully this will change soon.
I just had my annual done back in London and they informed me that the fix is now considered a terminating action by the FAA, no repeat 250 hours later.

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Re: New Waste Gate Controller AD for AE300

Post by CFIDave » Fri Apr 12, 2019 12:32 pm

rdrobson wrote:
Thu Apr 11, 2019 9:56 pm
]I just had my annual done back in London and they informed me that the fix is now considered a terminating action by the FAA, no repeat 250 hours later.
I wish this were true, but my check of the latest version of the AD on the FAA website says that it must still be performed every 250 hours; there is no "terminating action" yet for the FAA. (EASA *has* approved the fix as a terminating action).

Maybe the FAA is just behind in updating their online database?
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Re: New Waste Gate Controller AD for AE300

Post by Tommy » Sun Apr 14, 2019 11:24 am

I don’t quite get it. Why not just design a more robust control rod rather than go through the complexity of cables and clamps that really looks like a Mickey Mouse back door fix than anything permanent. It kind of looks like a design fix by committee. A really big committee.
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Re: New Waste Gate Controller AD for AE300

Post by Steve » Sun Apr 14, 2019 1:15 pm

Tommy wrote:
Sun Apr 14, 2019 11:24 am
I don’t quite get it. Why not just design a more robust control rod rather than go through the complexity of cables and clamps that really looks like a Mickey Mouse back door fix than anything permanent. It kind of looks like a design fix by committee. A really big committee.
I would guess that it is because even a thicker control rod assembly could fail, and there is no redundancy. The illustrated fix is doubly redundant (the control rod plus both cables would have to fail to render it inoperative). Plus, the present fix allows easier retrofit of the existing fleet.

I agree that it isn't an elegant solution...

Steve
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Re: New Waste Gate Controller AD for AE300

Post by Tommy » Sun Apr 14, 2019 1:31 pm

Ok,I can buy that to a degree. However, why cable and not solid rod? In addition, there comes a point where redundancy is a non issue.
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