TangoWhiskey
Touchdown! Greaser!
Time to start thinking about winter flying, and some pre-flight checks we might not otherwise do.
The breather tube (which vents engine crankcase moisture generated as a by-product of the combustion process) can ice up in cold weather, causing back pressure that can blow out oil seals—a bad thing. You lose your oil and the engine seizes.
An excerpt from an edition of the Lycoming Flyer, entitled "The Whistle Slot", states:
"Moisture is expelled from the engine crankcase through the breather tube which often extends through the bottom of the engine cowling into the air stream. Under very cold conditions, this moisture may freeze and continue a buildup of ice until the tube is completely blocked. It is normal practice for the airframe manufacturer to provide some means of preventing freeze-up of the crankcase breather tube. The breather tube may be insulated, it may be designed so the end is located in a hot area, it may be equipped with an electric heater, or it may incorporate a hole, notch or slot which is often called a "whistle slot."
The operator of any aircraft should know which method is used for preventing freezing of the breather tube, and should insure that the configuration is maintained as specified by the airframe manufacturer. Because of its simplicity, the "whistle slot" is often used. Although the end of the tube may extend into the air stream, a notch or hole in the tube is located in a warm area near the engine where freezing is extremely unlikely. When a breather tube with whistle slot is changed, the new tube must be of the same design."
Therefore, cold weather operations emphasize checking that the breather tube is not iced up or blocked.
Do you know which method your aircraft's manufacturer used to prevent freezing of the breather tube? Do you know where it's located, and how to check it?
If not, you might want to ask your mechanic to show you…
Here's what can happen if you don't:
http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20001207X03054&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001207X02834&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001206X01346&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001211X15697&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X18647&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20041201X01900&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X33396&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X24868&key=1
The breather tube (which vents engine crankcase moisture generated as a by-product of the combustion process) can ice up in cold weather, causing back pressure that can blow out oil seals—a bad thing. You lose your oil and the engine seizes.
An excerpt from an edition of the Lycoming Flyer, entitled "The Whistle Slot", states:
"Moisture is expelled from the engine crankcase through the breather tube which often extends through the bottom of the engine cowling into the air stream. Under very cold conditions, this moisture may freeze and continue a buildup of ice until the tube is completely blocked. It is normal practice for the airframe manufacturer to provide some means of preventing freeze-up of the crankcase breather tube. The breather tube may be insulated, it may be designed so the end is located in a hot area, it may be equipped with an electric heater, or it may incorporate a hole, notch or slot which is often called a "whistle slot."
The operator of any aircraft should know which method is used for preventing freezing of the breather tube, and should insure that the configuration is maintained as specified by the airframe manufacturer. Because of its simplicity, the "whistle slot" is often used. Although the end of the tube may extend into the air stream, a notch or hole in the tube is located in a warm area near the engine where freezing is extremely unlikely. When a breather tube with whistle slot is changed, the new tube must be of the same design."
Therefore, cold weather operations emphasize checking that the breather tube is not iced up or blocked.
Do you know which method your aircraft's manufacturer used to prevent freezing of the breather tube? Do you know where it's located, and how to check it?
If not, you might want to ask your mechanic to show you…
Here's what can happen if you don't:
http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20001207X03054&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001207X02834&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001206X01346&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001211X15697&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X18647&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20041201X01900&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X33396&key=1
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001213X24868&key=1