End of month fuel flow figures

[FRQ Charlie Bravo]

Hi all,

Do you use Tacho or MR for your end of month fuel flow figures? My company uses Tacho but only by default from the last CP. The current CP doesn't want figures that look like he burns more than the last bloke. i.e. fuel/tacho < fuel/MR time

All I care about when I'm doing a flight is fuel burn per minute in the air and an accurate enough taxi allowance.

Thoughts?

FRQ CB

[kalavo]

Real short answer is there are a number of different systems and the vast majority are going to give you the same end result. Just be aware of the limitation of the system you choose to use. I've seen Fuel/Airswitch, Fuel/Tacho, Fuel/Chock to Chock, Altitude Climbed (glider towing - one guy was using 1 litre per 300'), combinations of the above "40 litres/hr + 1 litre per 1000'" and of course "as per the flight manual" (which usually gives separate figures for climbs, cruises and descents.

Your fuel flow varies with power settings, temperature and altitude. But 99% of the time most of your flights are going to be taking off from the same airfields with the same average temperature, climbing to the same altitude and cruising for the same length of time. Just be aware when you move away from the norm how your system might be impacted.

1 litre per 300' works great when you're towing gliders, but if you took that aircraft to another site for maintenance and based your nav on 10 litres climbing to 3000' and nothing else, you would be an idiot.

Likewise if you'd been using Chock to Chock doing 5min taxi+20min flight and then did a 5min taxi+120min flight based on the same numbers, you'd find your fuel consumption rising dramatically because you're spending a larger portion of time at higher power settings.

Tacho which seems to be your main concern, it does a great job of tracking fuel flow because it takes in to account variations in power. If you fly at 2700rpm the tacho'll tick over quicker than at 2200rpm. Because of this tacho time may not equal flight planned time. Hence be aware of the limitation of your system - if you're using a higher rpm setting then its possible to clock up 1.1 tach hours in one airswitch hour. Make sure you take the fuel for this extra 0.1 hour! If you dont you could be rather embarassed. :)

The more you fly the aircraft, the more you'll get a fill for how thirsty it is.

[FRQ Charlie Bravo]

Yeah, the real shame is that it's so tempting to assume a C206/7/10 will average 60 lph but it really annoys me that it's slightly more year in and year out (i.e. 1 litre per minute gives easy maths but at 62 lph it's no conservative... C'est la vie)

FRQ CB