I have never been able to find a record of an instance where a C 172 spontaneously stopped feeding fuel from one tank.
However there are plenty of instances of C172s not feeding from the left tanks as these posts below show in a discussion you took part in!
A 1968 Cessna Skyhawk, Continental O-300-D, in flight, doesn't feed from port wing tank, with fuel selector on Both.
Running on the ground, tank selector to port, no problem. Timed static fuel flow from both tanks is identical.
and these
"A 1968 Cessna Skyhawk, Continental O-300-D, in flight, doesn't feed from port wing tank, with fuel selector on Both. "
How long did you run the test for? My old 172 used to feed from one side for around 45 min then switch itself to the other. I decided never to use "both" so I could keep track of how much was in each tank. Engineering opinion (M3) at the time was that this was normal.
Rod1
flyburg
29th Oct 2014, 10:26
Had the same problem not too long ago, Rented a 1968 C172 in LAX and flew it to SBA. During flight I noticed the left wing tank staying full and the right wing tank decreasing with fuel selector in both. After landing a fuel dip check confirmed that the indicators where accurate. Filled only the right tank and on the way back, same happened. Let the rental place know about it. As most of the flight took place at low altitudes with few places to land I didn't' try and trouble shoot with the fuel selector in different positions!
A first flight of the day check checklist should call for the
exercising(not yet mentioned) of the fuel cock and the selection of all positions. Not only does this stop the cock from becoming difficult to use it proves that you can draw fuel from each system and Cessna do provide the left/right cock for fuel balancing in cruise flight. The tank that you are going to use for take off should be the tank that you use for the power check as a restriction in the fuel line will be more pronounced during a power check than a low power taxy.The 172 manual states that only the section of Both should be used tor Take Off
From an instructors teaching point of view, its important that students actually practice operating fuel cocks, especially at schools where the cock is not routinely turned off after flight, otherwise you can be asking a student to turn tbe fuel off in an emegergency situation without ever having shown him how to actually do it and on some a/c turning the fuel cock off can be difficult while flying the aircraft. especially if you have never done it before!
This is another stupid flight schoolism mindlessly passed down from instructor to instructor.
I wouldnt call exercising and/or proving a fuel system stupid or mindless, I would call it good attitude, airmanship and CRM which prevents stupid and mindless mistakes