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Mooney down near Boulder, Colorado

Joe Zuffoletto

By Joe Zuffoletto
in General Mooney Talk

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FloridaMan Grand Master

FloridaMan

Posted
Posted

 

Jeff Slater, who was working on gas lines near the runway, heard but did not see the crash. He told The Daily Camera that the plane "didn't sound right" when it took off.

"It was choking and sputtering pretty bad," he said.

 

Guys, if your plane sputters, abort. 

M20JFlyer Enthusiast

M20JFlyer

Posted
Posted

The early evening news Boulder ch 9 indicting Fire crew identified aircraft as a Mooney m20 C.

news expands to include pilot is deceased

We extend condolences to the family and friends

Piloto Grand Master

Piloto

Posted
Posted

Power failure on take off. This happened to me on my old C model. Cause: water in the tanks that is not drainable when the drain adapter fitting has plugged holes at the skin interface. The holes can be plugged by tank debris or during a tank reseal. The drain valve then drain fuel from the stem top instead from the bottom making you believe there is no water in the tank. Since I switched to the F-391-72 drain valve to avoid this problem. It has the drain holes above the threads instead below the threads.

 

The problem is not visible during run up. As the plane accelerates and pitch up the small amount of water is displaced toward the rear where the fuel pick up is located. This causes engine power loss. I was lucky and landed straight ahead on a 9,000 ft runway. Before I landed looked at the fuel pressure but it was instead water pressure what I had. I removed the drain valve and sure enough water started pouring out. 

 

There is a small reduction in drain flow when draining from the stem top but can be mistaken by low fuel level in the tank. No matter how cautious of a pilot you are this one can get you.

 

José

Piloto Grand Master

Piloto

Posted
Posted

The F-391-72 is the one used in the Monroy LR tanks. The factory ones are the F-391-53. I didn't bother to advice the FAA or Mooney on this because it is not really a design flaw but a maintenance issue. If the adapter holes are periodically inspected and cleaned during resealing it is not an issue. But to me the added precaution is worth it, specially on vintage planes. BTW some mechanics put sealant on the F-391-53 threads before inserting it. When screw in the sealant squeeze down blocking the drain holes. This does not happens with the F-391-72

 

José

Sabremech Veteran

Sabremech

Posted
Posted

Hi Jose,

 I'm not sure I'm following your logic on using a -72 drain valve instead of the -53S which is called out in Mooney S/B M20-188A. By not having the drain holes at skin level as they are on the 53S you can't get the water out to the lowest level in the tank. The -72 will extend above the fuel drain nut plate and leave about 1/2 inch of fuel that isn't sumped. I recently cleaned debris from the drain slots on the drain nut plates as I had one sump that would hardly drain any fuel.

 There isn't a need to put sealant on the threads of the valve as there is an oring to seal the valve to the aircraft skin.

 

 David

  • Like 2
kmyfm20s Veteran

kmyfm20s

Posted
Posted

Correct me if I'm wrong Jose. But I think your saying is that since the debris is plugging the hole below the thread and is holding back potential water contamination. After lift off debris is agitated and allows water to enter the fuel line. If the holes are above the threads the agitated debris doesn't allow the water into the fuel line but remains in the low point of the tank?

orionflt Veteran

orionflt

Posted
Posted

Correct me if I'm wrong Jose. But I think your saying is that since the debris is plugging the hole below the thread and is holding back potential water contamination. After lift off debris is agitated and allows water to enter the fuel line. If the holes are above the threads the agitated debris doesn't allow the water into the fuel line but remains in the low point of the tank?

that is incorrect, any water in the tank will be agitated and has potential to cause an issue, sabermech summed things up nicely.

 

Brian

wishboneash Experienced

wishboneash

Posted
Posted

The F391-53S seems to be the correct design in my opinion. See this link below with pictures. It doesn't make sense to have the drain holes well above the threads. At worst, with the 53S, you can't drain the fuel if it gets blocked which forces you to inspect the valve and tank for debris, at least you don't get a false sense of security if there is water present below the threads with the -72 version.

 

http://www.bondline.org/wiki/Fuel_Tank_Drains

  • Like 1
Piloto Grand Master

Piloto

Posted
Posted

The difference in hole height is just 1/4", which is the same as the nutplate. To better understand the issue you have to look inside the tank of an old M20C Mooney. With age the -53S nutplate bottom drain holes eventually get clogged with tank debris, tank reseal or fuel truck hose material. You can insert a wire to clear the holes but you are just merely pushing out the debris that will come back and block the nutplate holes again. If you have the tanks resealed with someone unfamiliar to this it will just plug the nutplate holes. As you apply PRC-1422-A in non meticulous fashion it  has a tendency to build up at the nutplate blocking the drain holes. But if you are too meticulous the nutplate rivets may not get enough sealant and you may get leaks around the rivets. 

With the F-391-72 the above is not an issue because the valve holes are in direct contact with the fuel and not subject to the nutplate drain holes blockage. The drain valve location is the lowest point in the tank so everything accumulates at this point.

 

One way to check if the nutplate drain holes are blocked is by looking at the fuel stream when the valve is removed.

On clear drain holes the stream will look like a fan shower. You will be unable to drain in a container because is a mess.

On blocked drain holes the stream is narrow and you will be able to drain in a container. 

 

José

FloridaMan Grand Master

FloridaMan

Posted
Posted

Power failure on take off. This happened to me on my old C model. Cause: water in the tanks that is not drainable when the drain adapter fitting has plugged holes at the skin interface. The holes can be plugged by tank debris or during a tank reseal. The drain valve then drain fuel from the stem top instead from the bottom making you believe there is no water in the tank. Since I switched to the F-391-72 drain valve to avoid this problem. It has the drain holes above the threads instead below the threads.

 

The problem is not visible during run up. As the plane accelerates and pitch up the small amount of water is displaced toward the rear where the fuel pick up is located. This causes engine power loss. I was lucky and landed straight ahead on a 9,000 ft runway. Before I landed looked at the fuel pressure but it was instead water pressure what I had. I removed the drain valve and sure enough water started pouring out. 

 

There is a small reduction in drain flow when draining from the stem top but can be mistaken by low fuel level in the tank. No matter how cautious of a pilot you are this one can get you.

 

José

 

I know of an M20E pilot who was killed due to the same thing. There should be an AD on this, given the level of effort for the modification and the associated risk. 

Sabremech Veteran

Sabremech

Posted
Posted

Hi Jose,

 This is really a maintenance issue and shouldn't be solved by installing a part that isn't approved for this installation. The -72 will not get all the water out of the tank and by doing so, will allow the opportunity for corrosion to start or accelerate if already present.

 

 David

  • Like 1
bonal Grand Master

bonal

Posted
Posted

My prayers are to the famiies and friends. I hate it so much when this happens especially when its a mooney. As we take flight we are elated excited and full of joy doing what we love then tragedy strikes ending in the loss of life.  As people who fly we strive to achieve greater things in life so the loss to our community and culture is greater than the sum of the parts.

 

As for the drain issue well we dont know if that was the cause. That being said, can any one comment on the drains when there are O&N bladders installed. 

 

God Speed

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