Landing Gear Microswitch Failure

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rdrobson
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Landing Gear Microswitch Failure

Post by rdrobson »

Yesterday I didn't get my '3 greens' while on approach, one was missing. After running through the emergency checklist and unable to resolve the condition, I landed without incident. One of the wires to the left gear's down microswitch had broken. See attached photo. Anyone else have this happen to them? Both the mechanic and I thought the whole assembly looked rather fragile, especially in the context of the landing gear's environment. The aircraft only has 80 hours on it, so it seems rather early to be dealing with issues like this.

I'm wondering if the cable routing is bad. Although difficult to tell in the photo, the black sheathed cable comes towards the camera (aircraft aft) and then back towards the switch. On the right side, the cable seems to be more in the plane of the microswitch and (if I took a similar photo) would not come towards the camera.

--Ron
Gear Microswitch.jpg
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nrenno
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Re: Landing Gear Microswitch Failure

Post by nrenno »

Hi Ron,
From a quick examination of the photo it appears that either the hardware to secure the cables is missing or the landing gear system engineering was not done properly. I suggest that you inspect all other aircraft systems carefully to make sure that they do not need to be fixed.
Regards,
--Nilton
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Rich
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Re: Landing Gear Microswitch Failure

Post by Rich »

This looks like a condition I fought with in my DA40 compass light and floodlight power connectors where they transitioned between the canopy and the fixed instrument compartment. The installation causes the necessary flexing to happen right where the conductor terminates, instead of distributed across the body of the cable away from the terminations.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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rdrobson
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Re: Landing Gear Microswitch Failure

Post by rdrobson »

nrenno wrote:Hi Ron,
From a quick examination of the photo it appears that either the hardware to secure the cables is missing or the landing gear system engineering was not done properly. I suggest that you inspect all other aircraft systems carefully to make sure that they do not need to be fixed.
Regards,
--Nilton
You make a very good point (the same one my wife made as well). As only the 3rd DA62 out of London, they may not have refined their processes yet. There are some other issues that seem relatively minor, but they may be just the first manifestations of deeper issues. It will soon be going in for it's 100 hour check and oil change, that will be a good opportunity to look at some of the other items.

The question is, who is better to examine the other systems? My local mechanic or should I arrange to take it back to London for a few days?

--Ron
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Colin
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Re: Landing Gear Microswitch Failure

Post by Colin »

During my pre-flight I *always* think, "Those microswitches seem so fragile looking..."

You just confirmed it for me.
Colin Summers, PP Multi-Engine IFR, ~3,000hrs
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http://www.flyingsummers.com
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nrenno
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Re: Landing Gear Microswitch Failure

Post by nrenno »

Hi Ron,
Perhaps you and other owners could encourage Diamond to do a complete project review. A group engineers and mechanics could review at all systems to make sure that nothing was overlooked. Fixing small flaws could prevent serious mishaps in the future. Everyone would benefit from a review.
Regards,
--Nilton
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Rich
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Re: Landing Gear Microswitch Failure

Post by Rich »

On a related note: I picked up my DA40 from the factory in May 2002. It's serial number 40.208, which makes it 8th off the London production line. Something I really didn't notice until the following fall was the canopy seal leaked air (and sometimes rain) into the cabin. In fact, if you looked just right, you could see an air gap beneath the seal. In 2004 I flew it back to London for the first Diamond Fest and (among other things) squawked this to them. They removed the seal from the outer edge of the canopy and put a new one at the inner edge. Problem solved.

There was also a problem with the cable linking the right canopy latch to the latch lever. This caused the right-side latch to let go from time to time. I had an interim fix in place, but they also made a permanent fix for that problem on this visit.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Rmateu
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Re: Landing Gear Microswitch Failure

Post by Rmateu »

Comparing the photo with one of the micros on my DA42VI, it seems to lack a tye-rap that secures the cable to the assembly. I believe that by securing it, the cable does not lever against the micro switch when in transit
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rdrobson
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Re: Landing Gear Microswitch Failure

Post by rdrobson »

Rmateu wrote:Comparing the photo with one of the micros on my DA42VI, it seems to lack a tye-rap that secures the cable to the assembly. I believe that by securing it, the cable does not lever against the micro switch when in transit
Thanks for posting that picture. My mechanic secured the cable so that it is now identical to my right gear however neither one has the tie wrap on that little bracket as yours does. I can see where that would eliminate any chance of motion between the switch and the wires where they terminate into the switch potting material.
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