Another plus for a tail wheel aircraft

[davevramp]

I have been working on a Cessna 150. On the squawk list was” water in the gas”. I replaced the gas caps gaskets. Clearly the right one had been leaking. I pulled the sump drains. Found no water, lifted the wings one by one to make the water would run to the wing root, still no water. Each time some one flew the a/c they found water not in the wings sump but a small amount in the GASCOLATOR The owner then had a FBO stored the a/c in a heated building and pulled the sumps, Again no water. I flew the a/c last week did a good pre flight and drained the sumps well I found 2 oz of water in the GASCOLATOR. Flew for 1.5 hr and returned. Before tie down, I sumped the tanks, no water but 2 oz in the GASCOLATOR. Lifted the wings and sumped again no water. Had someone sit on the tail to get the tie down ring to touch the ground and sumped the tanks. I got 10 oz of water out of the right wing.
Any ideas?

[GAHorn]

You've got water in the gas.

(Sorry. Couldn't resist.)

Been using auto-gas (with ethanol) in it? It will attract moisture from atmosphere.

Depending on which year, you may also have collected water in the "moat" around the fuel caps while washing the airplane. It then seeps down into the tanks.

Don't forget, the atmosphere has humidity. The fuel tanks have ullage. (For everyone except bluEldr, That's the airspace above the fuel within the tank.) When nightfall occurs (and during flight at cool altitudes) and as a side-benefit of the cooling effects of evaporative gasoline, that moisture condenses on the interior fuel-tank walls. Turbulence in flight sloshes that fuel and "collects" that condensation and incorporates it into the fuel.... and it settles out in the gascolator. (Which is what gascolators are for.) Drain it each flight like we were all taught.

[Bill Hart]

While this I know doesn't help with the source of the water; the Cessna 150/152 club sells a low point drain that puts a petcock "T" under the belly of the AC. This is great for getting anything from the lowest point in the fuel system out.

[Showboatsix]

This link tells the story of C-150 gas tanks and water.
http://sumpthis.com/cessna150andcessna1 ... 24x768.htm

[blueldr]

My question is, why in hell did the airplane have to be "tailed down" to get the water to settle to the sump. It is supposed to drain to the sump area in the parked attitude. Seems to me that there must be a serious tank problem of some sort. An extended very nose high flight attitude could very likely cause complete loss of power if there was as much water in the tank as they found when depressing the tail.

[GAHorn]

Judging by the excellent pictures in the link provided by Showboatsix, I'd say that is indeed the case, bluEldr. I was surprised at the amount of water (approx. 2 quarts) that must be added before the sump would see it. I believe that would be far more than the capacity of the gascolator, and if true, could prove disastrous.

[Showboatsix]

When you use the links at the upper LH side of the C-150 page , they also tested a C-152, and have many more photos of water in tha tanks. Makes one wonder how many other tanks are like this.

[jrenwick]

When I first flew J3 Cubs in the early 1970s, they had no quick-drain at the rear of the fuselage tank -- which is the low point when the airplane is sitting on the ground. There was just a plug, which was supposed to be removed during annual inspections. My instructor taught me to lock the gascolator drain open, then walk back to the tail and lift it to a level attitude. That was supposed to expel water that would have stayed in the rear of the tank otherwise.

At some time in the 1970s, there was an AD requiring the plug at the rear of the tank to be replaced with a quick-drain valve. More than 30 years after the original design came out!

Seems like the CAA and FAA were slow to realize or react to the dangers of water accumulating in fuel tanks!

[GAHorn]

"I just had an apostrophe." (-Smee, in "Hook", mis-speaking when he meant "epiphany".)

Way back in the early '70's, I was in a '67 C-150 flying from Lufkin to Houston-Hobby, and got caught in a line of severe TRW's (I was out joy-riding as a young time-builder and didn't check wx). I made a dash for Conroe and landed after dark, just ahead of the solid line. The FBO was closed and the airport abandoned. I sat in the airplane while the line of TRW's pounded, rocked, and rained polecats. After about an hour of this the skies suddenly cleared (cold frontal passage) into a crystal-clear night. I took off for Houston and circumnavigated to the west around downtown and approached Hobby from the west. The nighttime city was a constellation below me. I was over the present site of the medical center when the engine quit.
As I glided down to what I believed to be fairly certain death, I got a full windshield view of the Prudential Insurance Bldg and it's colorful top, executive floor.

prudential.jpg

A couple hundred feet from colliding with the bldg, the windmilling propeller must have finished pumping all the water thru the system, and the engine roared back to life, and I was able to continue on to Hobby and land. They never found a thing wrong with the airplane, and everyone thought I'd experienced carb ice. I now believe it was water from sitting thru the heavy rains.

The Prudential Bldg was scheduled for destruction recently, despite my enthusiastic efforts to save it back in the early '70's.

From the Greater Houston Archetectural Preservation website:
"Prudential Building
(Houston Main Building, University of Texas Health Science Center)
1100 Holcombe Blvd.

This finely detailed 18-story skyscraper was the first high-rise office building constructed outside downtown Houston. Architect Kenneth Franzheim designed the building as regional headquarters for the Prudential Insurance Co. At the time, Prudential introduced a high level of amenities for its employees including convenient parking, generous landscaped grounds, public art, tennis courts and a tropically planted swimming pool court (the pool has been filled). The University of Texas M.D. Anderson Cancer Center has owned and occupied the building since 1975.

The Prudential Building is scheduled to be demolished and replaced by a new facility within the next four years. GHPA has been in contact with M.D. Anderson, but the institution's administration is not interested in preserving the building."

[cessna170bdriver]

George,

That's just another story that reinforces my belief that, given the choice of one, I'd rather be lucky than good any day.

Miles

[voorheesh]

This entire thread and the link to the Cessna sump test have been forwarded to the NTSB and a west coast FAA office investigating an engine failure in a Cessna 152 that occurred in California about 3 weeks ago. The airplane had been parked on a ramp with pretty heavy rain occuring for about 3 days. It flew an instructional flight for about 45 minutes without anomalies and then had a sudden engine failure while climbing after a touch and go. Neither the CFI or student were injured. The airplane was found inverted with about 10 gallons of fuel remaining in each wing tank and no sign of water. A significant amount of water was found in the gascolator. The CFI conducted the preflight and did not take a sample from the gascolator. He pulled the lever and let the gas go onto the ramp relating that it looked like gas. He did take a sample out of both wing sump drains and did not observe water. A possible lesson from this is to take several samples after an airplane sits in rain and carefully check for water (smell/make sure the cup is not full of water which may look like avgas). Don't just let the gascolator sample fall on the ramp. Put a cup under it and check.
The NTSB investigator was not aware of the Tennessee study and found both it and the comments by participants on this site to be very relevant to his investigation. He had been leaning towards carb ice until he read this material. I know that many could care less and others might be upset that a governmental agency would borrow the expertise that comes out of the cessna 170 site, but I am sure we all want to learn from accidents and be safe. I mention this only to let everyone know that your inputs are much appreciated.

[PilotMikeTX]

When I was instructing I went out to preflight a 152 after it had sat in steady rain for about 3 days. I noticed it seemed to be dripping water from the belly behind the baggage area. I pushed down on the tail and felt what seemed to be gallons of water sloshing back through the aft fuselage and pouring out from the tail. That certainly could have caused a W&B issue, since we were always at gross in a 152. I remember fuel orders like "5.2 gallons--total." It was either that airplane or another one that we sumped several fuel strainers full of water from each wing sump.

[GAHorn]

My 206 sat in my front yard for a couple of years and once, after a few days heavy rain, I went out to notice the same sort of dripping. I pushed down on the tail and at least five gallons of water sloshed to the rear.
Checking with Cessna, 1/8" drain holes were drilled in the belly just forward of each bulkhead and alodined to provide drainage.

[voorheesh]

I was able to speak at some length with both Robert E. Scowell Jr (Sp?) and Matt Taylor who did the tests documented on www.sumpthis.com. The results of these tests and others performed on several models of high wing Cessna aircraft were passed along to both the FAA and the NTSB years ago with no corrective actions taken or even recommended by those agencies. Cessna Aircraft apparently does not consider this subject to be a serious safety issue. The tests documented on this website were thorough and professional. The facts suggest that the design of high wing Cessna fuel tanks (wet wing, bladder, and even the old drop in tanks) are problematic when it comes to water. It seems that the tank design has low points below the sump and fuel pick ups and water can collect and sit there. When this happens it is very difficult to detect. Water acts strangely in 100LL. It forms globs and does not disperse. In turbulence or other disturbance of the wing, trapped water can break up and get in the fuel pick up to the gascolator. In extreme cases, the gascolator can become water saturated and there will be interruption of fuel to the engine. There have been numerous engine failures in these aircraft where there is no explanation in the investigative reports. When trying to determine if there is water in the tanks a sample is meaningless because the water, if there, is probably below the pick up. Investigators will run the engine out of the wreck and say it works fine, but they don't use the tanks and fuel back at the accident scene. Carb ice will sometimes be blamed if investigators find precipient conditions. When the fuel tank was opened up in the Cessna 152 I mentioned that was involved in an accident a few weeks ago, rust and water related stains were noted in the base of the tank indicating water contamination. There was no water present in the tanks, only in the gascolator. As the originator of this thread pointed out, we are fortunate to have tailwheels but I do not think we are immune to this problem. Even if we keep these old birds out of the rain, condensation during flight will happen and water in the fuel system to some extent is inevitable. This underscores the importance of taking a good sample out of the gascolator and smell it to make sure it is fuel. In some Cessnas, an AD related to this subject has pilots rock the wings side to side and fwd and aft. This might be a good idea if you suspect water in the fuel. Rock and let sit for a bit and then take samples from the wing and smell to make sure you are getting fuel. Mr. Scowell is very frustrated. He had 3 fuel related engine failures in his Cessna 172 (equipped with integral fuel tanks) and has voluntarily grounded it for at least 5 years. I suggested that rather than waiting for Cessna or the government to do something, why not hire a DER who knows fuel systems and see if he/she can design a fix that could be STCd and then sold to Cessna owners who care about this problem. After discussion, this idea, while possible, would be expensive, especially for newer Cessna with integral tanks/hat channel floors/etc. If you guys are interested, google "Cessna Fuel" and read more about it for yourseIves. I am looking into this problem and intend to revive the 6 year old safety recommendations based on this latest accident. If this had happened at night, that young CFI and his student might not have walked away from that 152. I'll keep you advised if you are interested.

[GAHorn]

Thanks Harlow, for taking the time and trouble.