Varga/ShinnVG-21 Squadron
MAINTENANCE ITEM #3
*** Fuel Quantity System ***
By Lee
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
maintenance or
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.