MAINTENANCE ITEM #3
*** Fuel Quantity System ***
More 2150's have been lost due to fuel exhaustion than from any other cause. The
Fuel gauges in many 2150's do not tell the truth due to improper
Each tank has a separate, independent gauge system. There are two sending units located inside of the fuel tank that are wired in series and a cockpit indicator, which reacts to the resistance provided by the float position of each of the tank sending units. The inboard sending unit must be installed in such a manner that it does not make electrical contact with the aircraft. This is the problem with most 2150's that have inaccurate fuel gauges.
I have two special tools, one that tests the cockpit gauge for proper operation and another that can verify that the tank senders are adjusted properly or need replacement. Anyone who has fuel quantity problems may contact me for assistance. If you need help, you can arrange a date and we, together, will test your aircraft and perhaps correct the problem in a few hours. There will be no charge for this service. I just don't want to see another 2150 go down due to fuel exhaustion. The following is an outline of how I test the fuel quantity system:
I. Disconnect wires (2) running from inboard tank sender to cockpit gauge. Clip on cockpit gauge tester to these wires, rotate control knobs from full counter-clockwise to full clockwise and note that cockpit gauge follows, empty to full.
2. Using an Ohmmeter, check continuity between inboard sender base and the airframe. If meter reads other than -0- ohms, it indicates that the insulation washers and/or insulating grommets are missing or require replacement.
3. If step I and 2 have not found the problem, drain the fuel tank,
remove both sending units, mount in sending unit test fixture and verify each units resistance using ohmmeter, (Note; We found the senders in our Varga had been reversed, the outboard unit mounted inboard), -0- ohms at bottom of float travel and 15 ohms at top of float travel.
No matter how well your fuel gauges work, keep a notebook under your seat and record tach time when tanks are filled. Never exceed 3.5 hours flying on full tanks.
In the next Newsletter, I will cover the 2150's fuel vent system and maintenance of the fuel shut-off valves. In future letters, we will cover 25 hour maintenance, owner-assist annuals, the proper way to safely fly formation with your buddy, flight control rigging for hands-off flight, engine overhaul/conversions, and installation of Lorans and the new breed of radios.
If you have a problem with your Varga/Shinn, let me know. Maybe we have a fix.