Piper Comanche's can vent fuel and then ya lose both engines

EdFred said:
The Comanche will lose 13gallons from the mains in one trip around the pattern if the fuel door is shut, but the fuel cap is left off.
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About 42 winters ago I was a new-ish copilot on a Lear 24D for a flight from Latrobe, PA to Boston. It was a bitter-cold (sub-zero cold, Prist plastic tube-snapping cold) morning and in my haste to follow the passengers into the warm cabin and out of the wind I didn't run around to the right wing tank to inspect the fuel cap. The fueler had given me a "thumbs up", so I figured he buttoned up the cap properly. Wrong. Shortly after lift-off the tower called with panic in their voice to tell us we were porting fuel out the right wing and wanted to know our "intentions". I looked over my right shoulder to find a geyser-looking plume of fuel like an opened fire hydrant spewing out the tip tank.

"What should I say, Rex?"
"Tell him were going to Boston."
"Rex, look out there! This is major!"
"We're going to Boston."

And we did. When we taxied in and all the passengers had left, forever unaware of the situation, he tells me he once spent an hour on his back trying to shake fuel out of an F-100 before making an emergency landing, for some reason that I don't recall, and hardly was able to make a meaningful dent in it. It might have been a drop tank that didn't. Anyway, I figure we only lost about 25 gallons of jet fuel during the trip, but the cap was still in place. The locking tab was not pressed down though. You couldn't see that from inside the airplane.
 
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CobraDriver said:
I could not have switched tanks sine the outboard were the ones causing problems and I ran out on the mains. And yes a mystery indeed.

My reason for posting this IS the mystery. I had no confirmation from the FAA, from the owner or from other sites I posted on.

As a matter of fact, a couple months ago there was an accident that involved with that type airplane, I called the local FSDO off the news reports I saw and shared my story, told them to call the guy that did my investigation and I never heard anything back from those guys either.

My whole point to this post was simple, be careful what happens when you go from mains to tips in a twin Comanche. That flight right there was the last time I flew THAT plane and ANY Comanche. I will never fly another again, and I love PIPER aircraft. It's what I grew up in.
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It is wise not to fly airplanes that you don't understand.
 
Kristin said:
It is wise not to fly airplanes that you don't understand.
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Nor one with invisible tip tanks :):

CobraDriver said:
So....BEWARE....a PA-30 (corrected/Edit) can vent when you switch from mains, to tips and back to mains...
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CobraDriver said:
The tips make "an extension " to the entire wing system and this aircraft did not have that
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CobraDriver said:
My whole point to this post was simple, be careful what happens when you go from mains to tips in a twin Comanche.
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Kristin said:
It is wise not to fly airplanes that you don't understand.
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Ohhhh so YOU understand what the issue is? I see....so YOU are an ancient FAA investigator or work for the NTSB or something right? Because even the FAA had no clue what the issue was....but YOU do. Of course you do.

Why don't you Oh Great One share with us minions exactly what happened....please do tell. I'll contact my investigator and quote you directly.

There always has to be one in the crowd
 
CobraDriver said:
Ohhhh so YOU understand what the issue is? I see....so YOU are an ancient FAA investigator or work for the NTSB or something right? Because even the FAA had no clue what the issue was....but YOU do. Of course you do.

Why don't you Oh Great One share with us minions exactly what happened....please do tell. I'll contact my investigator and quote you directly.

There always has to be one in the crowd
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I don't know Kristen, but she has a Twin Comanche. She's an A&P mechanic too. Your posts are all over the map, whether you flew something with actual tip tanks or not. I've speculated the best I can about what might reconcile everything you've said happened, so I guess she can too. Again, what was the corrective action by the mechanic who addressed the discrepancy?
 
dtuuri said:
I don't know Kristen, but she has a Twin Comanche. She's an A&P mechanic too. Your posts are all over the map, whether you flew something with actual tip tanks or not. I've speculated the best I can about what might reconcile everything you've said happened, so I guess she can too. Again, what was the corrective action by the mechanic who addressed the discrepancy?
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As I mentioned before, I never flew the plane again, avoided the owner that kept calling me to fly it again, I assisted with the investigation, was cleared 100% since even the FAA didn't know what the answer was, I really don't know nor do I care what the mechanic did or what the corrective action was. That's a job for the FAA and their investigators to analyze/decide/correct/issue corrections for. I have many other irons in the fire to make this a priority. That's why I never flew it again....I'll stick to AZTECS for starters, I only have 1200 or so hrs in them but they have always treated me well.
 
You do realize that Kristin is probably THE expert on Twin Comanches in the nation, dont you?

Here's the deal from what I can tell if I read everything right...
You didnt visually check all the tanks before departure.

Owner says they were full (maybe to cover his ass)

Occams Razor
 
CobraDriver said:
Ohhhh so YOU understand what the issue is? I see....so YOU are an ancient FAA investigator or work for the NTSB or something right? Because even the FAA had no clue what the issue was....but YOU do. Of course you do.

Why don't you Oh Great One share with us minions exactly what happened....please do tell. I'll contact my investigator and quote you directly.

There always has to be one in the crowd
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I understand what is not the issue for sure. I haven't yet found anyone in the FAA that knew much about a Twin Comanche and I have found many that have virtually no GA experience at all. So what the FAA finds or doesn't find is of little value in the vast majority of cases.

You can share this with your inspector: You didn't confirm that the aux tanks for actually full of fuel. In fact, the aux tanks were empty, and the mains were not likely full, if you only flew two hours as even poorly leaned, the plane is not likely to burn more than 20 gph and if the mains are full you have 54 usable. Of course, if no one was watching the person filling the mains, they may have only filled to the bottom of the neck, in which case you only have about 48 gallons usable fuel in the aircraft. Unfamiliarity with the aircraft. Failure to get a proper check out. Improper pre-flight. Feel free to give your inspector my name. I would be happy to talk to him.
 
Chip Sylverne said:
The 90gallon Comanche, post 1960 I think, has 4 tanks standard. The two inboard are the mains 30gallon each, the two outboards are the aux 15gallons each. All of those tanks have bladders, and are vented out the front/lower of the wing. The vents icing over was a problem in the early models, so the vent design was changed.

Then there are the tips which are aftermarket, without bladders.
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I have the tips on my pa24.

I was flying my PA24 from St. Martin to Turks and Caicos with Osborne Tip Tanks. I have the fuel selector set on both tips, and about 15 miles off the coast of Puerto Rico, the engine started sputtering. I switched to my mains and landed at San Juan. Did not declare an emergency but had to explain my problem to customs after landing.

During the flight, my right tip was higher than my left and the fuel had siphoned over to the left and vented out. Since that time, I never burn both tips at the same time.

Another time, while parked with full main and auxs with a strut issue (low wing) and leaving fuel switch on both aux tanks, I had the fuel drain over and vent out to the ground.
 
PiperW said:
I have the tips on my pa24

Another time, while parked with full main and auxs with a strut issue (low wing) and leaving fuel switch on both aux tanks, I had the fuel drain over and vent out to the ground.
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I have had that happen on both mains selected as well.
 
PiperW said:
I have the tips on my pa24.

I was flying my PA24 from St. Martin to Turks and Caicos with Osborne Tip Tanks. I have the fuel selector set on both tips, and about 15 miles off the coast of Puerto Rico, the engine started sputtering. I switched to my mains and landed at San Juan. Did not declare an emergency but had to explain my problem to customs after landing.

During the flight, my right tip was higher than my left and the fuel had siphoned over to the left and vented out. Since that time, I never burn both tips at the same time.

Another time, while parked with full main and auxs with a strut issue (low wing) and leaving fuel switch on both aux tanks, I had the fuel drain over and vent out to the ground.
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The fuel selection system is completely redone when tip tanks are installed on a PA-24. Much different than the tip tank plumbing for the twins. It is the only system that allows feeding from both tanks at the same time. That is something I have never been a fan of, even in Cessnas. At the very least, check valves should have been added to the PA-24 plumbing to prevent that.
 
Kristin said:
The fuel selection system is completely redone when tip tanks are installed on a PA-24. Much different than the tip tank plumbing for the twins. It is the only system that allows feeding from both tanks at the same time. That is something I have never been a fan of, even in Cessnas. At the very least, check valves should have been added to the PA-24 plumbing to prevent that.
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How are the Pa30s with tips plumbed ? Transfer pumps ?
 
weilke said:
How are the Pa30s with tips plumbed ? Transfer pumps ?
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The PA-30/39 system uses two solenoid valves installed in the line from the aux tanks. When the fuel selector is set to AUX, flipping a switch will activate the solenoid valve to open the path to the tip tanks which are plumbed to the solenoid along with the aux fuel line. This happens upstream of the manual fuel selector valves. The unpowered position of the solenoid is to draw from the aux tanks so in the event of a valve failure or circuit failure, the fuel in the tips becomes unusable. For that reason primarily, most pilots burn down the tip tanks first after takeoff or establishing themselves in cruise. It is a pretty reliably and easy to use system.
 
While flying long distance legs over the waters of the Caribbean, fuel management using 6 separate tanks was a challenge. I never trusted the gauges as a sole source but I did trust my flow meter accumulator on my JPI930 along with my fuel flow/hr and my watch. In order to have enough fuel to make the mainland from Puerto Rico, I would take each individual tank down to zero. It was paramount that I knew how much fuel I had on board at all times and once I emptied a tank I knew that there was no need in ever switching back to that particular tank. I recorded everything in my journal.
Keeping the small PA24 fuel balanced required switching from wing side to wing side every 5 to 10 gals. These task kept me active, the plane flying reasonably level, and a realistic gallon count.

After making the mainland, getting a good night sleep, and after filling, I would start my next flight using the last main tank I landed on. After establishing level fight, I would switch to each tip and a few times did have sputtering from the previous flight.
 
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