January 2012
Q: Steve,
I have an early model 1973 Cherokee Six 260. The fuel tank selector valve is located under the rear seat. I noticed that I was using more fuel than I expected the last two times I’ve filled my Six’s tanks. I’ve heard that if the selector leaks internally, I’ll lose fuel. How does this happen? Can it be caused by a loose fitting or connection?
Thanks,
—Gas Be Gone
A: Dear Gas,
It’s important to understand the concern over internal leakage. As I understand it, if the valve leaks internally, fuel from the tiptanks leaks through the valve into the main tanks, overfilling the main tanks and spewing fuel overboard out the main tank vent lines.
Before I send you to a repair station that overhauls these Airborne fuel selectors, I want to update you on the Piper Service information on fuel valves.
Piper Service Bulletins 376, 444, 571A, and 1198A have been generated to address fuel selector issues over the years. SB 444 spells out the details of replacing certain valves with improved valves. The newer replacement valves are part numbers 1-H65-2 and 1-H65-3; older valves are part numbers 1H10, 1H16-1, 1H26-2, 1H26-3 and 1H26-4.
FAA Airworthiness Directive 76-18-04 describes a simple test to determine if your fuel valve is leaking internally. Fill the fuel tanks; sump the selector valve quick drain three times to eliminate the possibility of air in the system; and start the engine and run it at 1,000 rpm with the electric fuel pump on.
With the engine running, turn the fuel selector to the “off” position and note the time. If the valve is not leaking, the engine will die before seven minutes passes. If it continues to run past the seven-minute limit, the valve is leaking internally.
AD 76-18-04 applies to the Airborne 1-H26-2 and -3 valves which may be installed in your airplane. Service Bulletin 519A “Fuel Selector Valve Inspection and Replacement” expands on the AD.
AD 77-12-01 also applies to Airborne Model 1H10, 1H16-1, 1H26-2, 1H26-3 or 1H26-4 model fuel selector valves. It describes a simpler valve leak check procedure, but it is more onerous because it mandates that the leak check procedure be done before the first flight of each day, and in addition, at 50-hour intervals.
This leak test consists of turning the fuel selector handle to the “off” position; emptying the fuel in the selector by opening the selector sump drain; then closing the drain after fuel stops flowing. Wait at least three minutes, then again open the fuel selector sump drain and collect the contents. If the fuel collected exceeds one-half fluid ounce this indicates the valve is leaking internally. If removing, cleaning and re-testing does not stop the leakage, the valve must be replaced with valve kit 757 148V or 760 895V.
These valves are pretty simple. Springs push a ball against a seat preventing fuel flow from each tank. The sealing ball is displaced from the seat of the selected tank allowing fuel to flow. Figure 86 in the Cherokee PA-32-260, PA-32-300 and PA-32R-300 parts manual (753-690) shows part numbers for the spring, O-rings, and balls in the earlier valves.
After praising the engineering built into Parker Airborne products, Tim Henderson of Aero Accessories, Inc. in Gibsonville, N.C. said that the O-rings are most likely responsible for any internal leakage. These O-rings are widely available at aviation parts houses.
One facility that overhauls fuel valves is Parker Hannifin in Naples, Fla. (The former Shaw Aero Devices, Inc. was acquired by Parker Hannifin in 2007. —Ed.) According to the quality control manager at the Parker Hannifin repair station, each valve is disassembled and evaluated, then a cost estimate is sent and upon approval the valve is overhauled.
Best,
Steve
Q: Hi Steve,
I want to know more about the advisability of blocking off my oil cooler during cold weather flying. This is a “hot” topic among the pilots at my local airport. Some guys say that they have been flying for years, have never worried about it, and their engines have run fine for years. Then there is the guy who bought his Cessna 172 new in 1976 and he has a set of plates designed to be installed across the cowling inlets and the oil cooler during cold weather operation.
What’s the right answer? Is there one answer that fits all airplanes? If one airplane manufacturer doesn’t mention anything about these plates, and another does, who is right? Finally, where do I get them if I need them?
—Confused in Canada
A: Dear Confused,
You’re right. This discussion on the need for “winter fronts,” how to install them, and when to install and remove them has been going on for years, especially by flyers that live in regions where winter temperatures are only semi-cold.
Piper, Cessna and Beech don’t march in lockstep on this issue.
Cessna has provided winterization equipment and detailed explanation on the steps needed during winter flying for years. Check this out—from the 1966 Cessna 182 owner’s manual: “An optional winterization kit is available for use when operating to temperatures below 20º F.”
To further expand on winterization kits, the parts book for the 1975-84 Cessna 172 shows winterization equipment that consists of restrictor plates to limit airflow through the oil cooler. In addition there are left and right “cover assemblies” that lessen the engine air cooling inlets by at least 30 percent. A panel-mounted placard says that the oil cooler restrictor plate must be removed when OATs exceed 20° F.
From the sales brochure for the Cessna Corvalis high performance single:
“Winterization Kit – includes oil cooler door and ground adjustable flap over oil cooler to assist in obtaining optimal temperatures.”
Piper? Not so much. Not a word in the PA-28E Cherokee owner’s manual about winter operations, but the Archer III information manual gives the briefest of direction in section 8-29 under “Cold Weather Operation.” It says, “For cold weather operation a winterization plate is installed on the inlet opening of the oil cooler duct on the right rear engine baffle. This plate should be installed whenever the ambient temperature reaches 50° F or less.” It goes on to say the plate should be removed whenever the ambient temperature exceeds 50° F.
A Beech Sierra Pilots Information Manual does not mention winterization equipment.
The wording in the Cessna Corvalis manual quoted above is important; it describes the necessity of “obtaining optimal temperatures.” The optimal oil temperature during all operations is between 180 and 200° F. Therefore, the first consideration during winter operations is taking steps to maintain the oil temperature.
Due to the fact that the parts of the winterization kits were optional during purchase, parts are expensive, and suppliers are hard to find, it’s not uncommon to see strips of cloth-reinforced “duct tape” pasted across the face of an oil cooler during winter months.
However, Paul Saurenman of Pacific Oil Cooler Service has seen thousands of coolers returned for repair and cautions owners not to use duct tape across the face of a cooler since the glue and threads will eventually infiltrate the fine passages and lessen the effectiveness of the cooler, rendering it impossible to repair. He suggests that pilots use the tape to hold an aluminum plate in place instead.
Restricting airflow across an oil cooler is required at some point in order to maintain the optimum oil temperature.
Another critical preventive step, especially important on big-bore Continental engines (-470, -520 and -550 series) is insulating the crankcase breather tube which in these engines exits the engine case just behind the prop and then is routed along the top of the engine. This tube, which vents water vapor from the engine, must be lagged during winter operations, lest it freeze up and become blocked.
Block off the oil cooler as necessary to maintain optimal oil temperatures and pay close attention to the engine breather tube, especially if your engine is a big-bore Continental.
Happy flying,
Steve
Steve Ells has been an A&P/IA for 38 years and is a commercial pilot with Instrument and Multi-Engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as Associate Editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (www.EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to editor@www.piperflyer.com.
Resources
Leaking fuel valves
Send parts to
Parker Hannifin
Attn: Repair Station
3580 Shaw Blvd
Naples, FL 34117
The phone number at the
facility is (239) 304-1000.
Oil Coolers
Pacific Oil Cooler Service, Inc.
www.oilcoolers.com
