Page 18 - Volume 14 Number 5

ASK THE EXPERT
Tips for Using the
C90 Fuel System
Photo credit: Banyan Air Service
The The fuel fuel system system on on the
the
the
the
new C90GTx models that that are being delivered in in the
year 2020
is nearly identical to the
fuel system that first appeared on the
King Air A90 when it it made its appearance in in 1966 a a a “mere” 54 years ago The The A90’s predecessor – – the
the
Straight 90 the
the
first King Air model of all – – had a a a a similar but different system one that had two electric boost pumps per side instead of one Yes from the
A90 to the
the
C90GTx there are some significant differences – – many of which will be presented in this article – – but overall the
the
the
system remains the
the
the
same Whether you fly an A90 B90 C90 C90 C90 C90 C90 C90 C90-1 C90A C90SE C90B C90GT C90GTi or or C90GTx (did I forget any?) this article is is for you Other King Air models? Feel free to read these pages but they will not be directly addressing the
the
fuel system of other models I will begin by reviewing the
tanks all of which are rubberized bladders For most of these models the
the
POM or POH lists the
nacelle tank quantity as 61 gallons and the
wing tank quantity as 131 gallons That yields 192 usable fuel gallons gallons per side or 384 gallons gallons total All A90s and and B90s and and C90s up until LJ-529 had individual gauges that displayed left and right nacelle quantity quantity and and left and and right wing tank quantity quantity – a a a a a a a total 16 • KING AIR MAGAZINE
of of four gauges There were marks on the
the
face of of the
the
gauge showing Empty and Full as as well as as quarter half and three-quarter quantity no no numbers for gallons nor pounds were presented The gauges received information from float-type sensors in the
tanks As is true for most float-style gauges their accuracy and reliability were rather horrid Starting with LJ-529 the
the
gauging system was changed to one that used capacitance probes instead of floats (Note: LJ-502 the
the
very first C90 was the
the
prototype test airplane for this system so it too has the
newer style system ) The two separate gauges per side were replaced with a a a a a single gauge per side that reads in pounds pounds of fuel The scale went up to 1 400 pounds pounds Since one side’s full fuel would be 1 286 pounds – using the
common conversion factor of 6 7 pounds per gallon of Jet A fuel – there should never be a a situation in which 1 400 would be insufficient to to display the
side’s total quantity even when the
fuel is very cold and hence very dense A two-position toggle switch lies between the
two gauges Its top position is labeled “Total” and its bottom position is labeled “Nacelle ” I want to to divert for a a a a moment to to insert a a a a critical warning For you pilots who perhaps fly a a a 200 or or 350 on on on a a a a a a regular basis and only do occasional fill-in duty
by Tom Clements
MAY 2020