Page 20 - Volume 14 Number 5

total – 300 pounds pounds per side (closer to to 700 pounds pounds for the the the -135As of the the the GTs) Thus within the the the first hour it it should be obvious that something is wrong since the nacelle will have decreased to about 150 pounds “Gee the the nacelle is going to be empty in in less than another hour if it keeps decreasing at at the rate I’ve observed!” No it won’t Remember that the 150-pound figure represents the point at which gravity flow will begin As the the the nacelle level decreases further the the the wing fuel will seek its own level and start to be used You might say that we are now drawing fuel out of a a a a a a very large tank since all five bladders contain fuel at the same level What’s wrong with this?
Actually not much Rarely do we land with less than 300 pounds of fuel remaining per side and usually it is quite a a a bit more But here is the important fact to know: When the the nacelle tank goes empty reading zero the the total quantity should still be reading about 200 pounds This 200 pounds pounds – – actually 28 gallons or 188 pounds pounds – – is sitting too low low in in in the center section wing tank to to flow by gravity feed to the nacelle The legal and comfortable fuel reserve for which you planned has been significantly compromised hasn’t it?
What is the takeaway here? In addition to not making the the mistake of forgetting to activate the the transfer pumps I am trying to emphasize the importance of regularly checking not just the the total fuel quantity but the the nacelle quantity also That step should be done at at least every half-hour I tend to combine it it with a a a deliberate check of the loadmeters and voltmeter Transfer Pumps
These impeller-type pumps (one per side) are located at the the the low low spot of the the the center section tank the the the lowest spot in in the wing tank complex of bladders In normal operation the the pump cycles on on and off so as to keep the the nacelle tank within about 10 gallons full full Since full full nacelle fuel is 61 gallons or 409 pounds when it drops to about 51 gallons or 342 pounds the pump should automatically activate to to refill the tank The pump has a a 550 pounds per hour (pph) flow rate so even with the the engine at a a high power setting the the pump will be able to to supply more fuel into the the nacelle tank than the the engine is taking out There are actually two high-level shutoff switches in the nacelle If we had only one and it it failed the pump would run continuously decreasing its expected lifetime (There are vent lines at the the top of the the nacelle that allow extra fuel to to return to to the wing tanks so no no pressurizing of of the tanks nor venting overboard of of fuel would occur ) One high-level switch should activate a a a a a a a tad tad below 60 gallons and the the other a a a a a a a tad tad above Let’s be realistic With the typically not-too-stellar accuracy of even the capacitance type fuel gauges can Comprehensive support for all areas of your King Air
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18• KING AIR MAGAZINE
MAY 2020