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It’s Father’s Day so I thought I'd relax and share something with other dads that I know I wish I could have found this easily - a way to tell how much fuel a Bravo with Jose Monroy’s LR tanks really has in it! Thanks to the great guys at Weber Aircraft Service in Lancaster PA., who were very happy to help me solve the mystery, I have here a chart which can be used to get a very close reading of the amount of fuel in a wing. The disclaimer here is simple: Use this at your own risk, and it’s up to you to verify the results. A brief background: The M20M has panel fuel gauges that can (in most installations) be adjusted for three conditions: 1) to show empty with unusable fuel in the wing; 2) to annunciate a “low fuel” condition which should be, according to the Maintenance Manual, be about 2.5-3.0 gallons of useable fuel remaining; and 3) to show full tanks. I am told these setting drift over time and the gauge becomes less and less accurate. The panel gauges are adjusted to be “calibrated” for use in level flight, which means they will be different on the ground. To solve for this, Mooney has an option for wing gauges that show the approximate fuel level in each wing, calibrated for use only on the ground when the airplane is on a flat and level surface, which means they will read differently in the air. Stock Bravo’s have a total fuel load of 95 gallons, with 89 gallons considered usable. That’s 44.5 per side. Monroy cleverly designed a system for many models that adds tank space for additional fuel to extend the range of the aircraft. For the M20M with speed brakes the Monroy tanks add 29 additional useable gallons, 14.5 per side. So a Bravo, with speed brakes, and Monroy LR tanks will have a useable capacity of 118 gallons or 59 gallons a side. The **only** issue with this is that the Monroy Tanks are designed to feed from and flow out of the main tank system, and they do this in a non-linear fashion as it relates to fuel quantity. The problem is that the panel and wing gauges are calibrated for a linear fuel drop and as such become inaccurate (as shown) when fuel fills and drains from the LR tanks. Jose has little stickers that are affixed to the panel gauges that show this error and the correction needed, but if the panel gauges are not calibrated correctly in the first place, then all bets are off. Weber did two things for me - they calibrated the panel gauges which were “way off”, and they calibrated an old fashioned fuel stick for me so I never have to guess again. To get this done, I spent all of my Father’s day allowance. First you need a Universal XL 16” Fuelhawk fuel stick, here's a link to Aircraft Spruce they are available at most pilot shops and on Amazon. Next, print the attachment: Remember this is only for the Mooney M20M TLS Bravo, with speed brakes and Monroy LR tanks. Happy fueling! Dave [Edit: Please also remember that you must wait a few minutes after fueling to allow the fuel to settle into the Monroy tanks. Fuel seeps in by a rather small opening and you need to give this time to equalize for an accurate reading]

All.... I have 92 M20-J MSE version. Aircraft has typical fuel gauges on the instrument cluster panel and has dial indicating gauges on the wing tanks. Really nice setup for verification. Just recently I've starting flying the aircraft for longer duration's. I am noticing below 8 gallons on the Instrument Cluster I am seeing 10 to 12 gallons on the wing dials. I am also seeing a very erratic moment on the instrument gauge cluster. Reading will bounce from 0 to ~8........ I do not see an erratic instrument cluster movement when the tanks are in 15 to full range..... I have also seen the instrument gauge cluster needle stick at 0. A slight bounce of the rudder seems to bring it back to a reading but still always lower than the dial gauges on the wings. Having said the above........when the tanks have more than ~15 gallons the accuracy between the wing gauges and the instruments gauges are very close. Does anyone know what creates an erratic instrument reading and inaccurate differences at lower tank volumes? Thanks in advance! Other than this.....This baby is flying GREAT! Rick